JP2012225163A - Ehc control method and exhaust gas purification system using the same - Google Patents

Abstract

An exhaust gas purifying apparatus is provided by rapidly increasing power supplied to EHC while avoiding discharge in EHC in a situation where condensate water is generated (can be generated) due to water vapor contained in exhaust gas. Warm up.
When it is determined that dew condensation can occur in the first or second EHC, power is supplied to each of the first EHC and the second EHC at a relatively low voltage. On the other hand, if it is determined that the first or second EHC is not in a state where condensation can occur, and if it is determined that power should be supplied to the first and / or second EHC, the voltage is set to a relatively high voltage. To supply power to the first and / or second EHC.
[Selection] Figure 3

Description

  The present invention relates to a method for controlling a catalyst with an electric heater (EHC) in an exhaust gas purification system of an internal combustion engine. Furthermore, the present invention also relates to an exhaust gas purification system for an internal combustion engine that uses the EHC control method.

  In an internal combustion engine, from the viewpoint of environmental protection, particulate matter (PM: Particulate Matter) such as soot and SOF (Solution Organic Fraction) contained in exhaust gas, carbon monoxide (CO), hydrocarbon (HC), nitrogen oxidation There is a demand to reduce materials (NOx) and the like.

  In response to such a requirement, for example, a technique is known in which a filter for collecting PM such as a diesel particulate filter (DPF) (hereinafter also referred to as a “PM collection filter”) is provided in an exhaust system of an internal combustion engine. Yes. There is also known a technique for providing various exhaust gas purification catalysts for purifying harmful substances such as CO, HC, NOx in exhaust gas. Further, a combination of a PM collection filter and an exhaust gas purification catalyst (hereinafter also referred to as a “filter or the like”), or a substance that purifies plural kinds of harmful substances (for example, a three-way catalyst) is used as an exhaust system for an internal combustion engine. A technique for disposing them is known.

  In these exhaust gas purifying catalysts, in general, the exhaust gas purifying function by the catalyst is not sufficiently exhibited at normal temperature (because the activation temperature of the catalyst has not been reached). That is, in order for the exhaust gas purification catalyst to exhibit its original exhaust gas purification function, these catalysts need to reach a predetermined temperature. Further, for example, a catalyst regeneration process such as a SOx regeneration process for so-called SOx poisoning of an NOx storage reduction catalyst (hereinafter also referred to as “NSR catalyst”) does not proceed sufficiently at room temperature, and the catalyst to be regenerated It is necessary to reach a predetermined temperature.

  Further, in the PM trapping filter, when the amount of trapped PM increases, the exhaust passage resistance increases and eventually the filter becomes clogged, and in the worst case, the filter may be damaged due to sudden combustion of PM. . Therefore, in the PM collection filter, for example, when the differential pressure between the upstream side and the downstream side of the filter (hereinafter also referred to as “front-rear differential pressure”) exceeds a specified value, the PM collection filter collects the PM collection filter. A regeneration process (hereinafter also referred to as “PM regeneration process”) for removing the particulate matter by burning is performed. Also for this PM regeneration process, the PM trapping filter needs to reach a predetermined temperature.

  In the present specification, devices for purifying exhaust gas, such as the above-mentioned various exhaust gas purification catalysts and PM collection filters, are collectively referred to as “exhaust gas purification device”, and the SOx regeneration processing and PM regeneration processing are referred to as “exhaust gas purification device”. In addition, the NOx catalyst may be collectively referred to as “regeneration processing” of the exhaust gas purification device, including NOx reduction processing for the NOx catalyst.

  As described above, in order for the exhaust gas purification device to perform its original exhaust gas purification function or to sufficiently perform the regeneration process of the exhaust gas purification device, the exhaust gas purification device is heated to a predetermined temperature. Need to be. Therefore, for example, by disposing these exhaust gas purification devices near the internal combustion engine, the temperature of the exhaust gas purification device is increased early by using the heat of the exhaust gas or the conduction heat from the exhaust pipe. Measures to do this have been made. However, with such measures, when the internal combustion engine is started in a cold state (hereinafter also referred to as “cold start”), the temperature of the exhaust gas purification device cannot reach a predetermined temperature, The exhaust gas purification function of the exhaust gas purification device is deteriorated or the exhaust gas purification device cannot be sufficiently regenerated, resulting in insufficient reduction of harmful substance emissions in the exhaust gas. There is a fear.

  Therefore, an electrically heated catalyst (EHC) is provided upstream of the exhaust gas purification device in the exhaust passage of the internal combustion engine, and the temperature of the exhaust gas purification device reaches a predetermined temperature when the internal combustion engine is cold started. If not, the EHC is energized to promote warm-up of the exhaust gas purifying device disposed downstream of the EHC, to perform the original exhaust gas purifying function, or to sufficiently perform the regeneration process. The technology to do is known.

  However, the exhaust gas flowing through the exhaust passage where the EHC is provided as described above contains moisture generated as the fuel burns as water vapor, and is, for example, left in a cold state for a long period of time. When the internal combustion engine is cold started, for example, water vapor in the exhaust gas tends to condense in the exhaust passage and easily produce condensed water.

  In such a situation, when the EHC is energized as described above, for example, the EHC, a facility (for example, a vehicle, etc.) including the EHC and the exhaust passage are brought into conduction through the condensed water, and there is a risk of causing a leakage. There is. When the EHC is energized in such a situation where leakage occurs (or can occur), a part of the electric power resources that should originally be used for warming up the exhaust gas purifying apparatus is wasted, and the viewpoint of energy saving. This is also undesirable. In addition, for example, when a facility (for example, a vehicle) or an exhaust passage having an EHC is in a conductive state as described above, for example, when a driver of the facility (for example, a vehicle) contacts the facility. In addition, there is a risk of electric shock, which is not preferable for safety.

  Therefore, for example, prior to the start of energization of the EHC, it is determined whether or not the EHC is in a state where (or can cause) electric leakage, and the determination result is affirmative (that is, the EHC causes (or can cause) electric leakage). In the case of a determination result indicating that there is a situation, it has been proposed to perform control to prohibit energization of the EHC (see, for example, Patent Document 1). Alternatively, when the temperature of the EHC is lower than a predetermined reference value, it is proposed to reduce the moisture in the exhaust gas by introducing the exhaust gas to a bypass passage having a means for adsorbing moisture in the exhaust gas upstream of the EHC. (For example, see Patent Document 2).

  However, if the current supply to the EHC is frequently restricted for the purpose of avoiding leakage as described above, the reduction of harmful substances discharged when the internal combustion engine is cold started becomes insufficient, and the internal combustion engine is cooled. The significance of installing the EHC, which promotes warming up of the exhaust gas purification device during the start-up, is diminished. Further, as described above, newly providing a moisture adsorbing means and a bypass passage may complicate / enlarge the exhaust gas purification system and increase the manufacturing cost.

  On the other hand, with the recent heightened awareness of environmental protection, demands for reducing the amount of harmful substances emitted from internal combustion engines have become increasingly severe. Therefore, when the temperature of the exhaust gas purification device does not reach a predetermined temperature, such as when the internal combustion engine is cold started, the exhaust gas purification device cannot be warmed up quickly to perform its original exhaust gas purification function. In addition, a technique for shortening the period during which the reproduction process cannot be performed as much as possible is required more than ever.

  As described above, in order to warm up the exhaust gas purification device more quickly, it is necessary to increase the voltage of the electric power supplied to the EHC (that is, increase the resistance of the EHC). However, when the electric resistance of the EHC is increased and the voltage applied to the EHC is increased, in the situation where condensed water due to water vapor contained in the exhaust gas is generated (can be generated), as described above, there is a leakage. In addition to a further increase in the possibility of occurrence, discharge may occur in the region where the condensed water is present in the EHC, which may reduce the reliability of the entire exhaust gas purifying apparatus including the EHC. As a result, it has been conventionally difficult to increase the voltage supplied to EHC (to increase the resistance of EHC).

JP 2010-223159 A JP 2010-270653 A

  As described above, in the technical field, a technique capable of quickly warming up the exhaust gas purification device is required. In order to meet such demands, it is necessary to increase the voltage supplied to the EHC (to increase the resistance of the EHC). However, when the electric resistance of the EHC is increased to increase the voltage applied to the EHC, in the situation where condensed water due to water vapor contained in the exhaust gas is generated (can be generated), the region where the condensed water exists in the EHC As a result, discharge may occur and the reliability of the entire exhaust gas purifying apparatus including EHC may be reduced.

  That is, in this technical field, the electric power supplied to the EHC is increased to avoid the discharge in the EHC in a situation where condensed water due to water vapor contained in the exhaust gas is generated (can be generated), and the exhaust gas is discharged. There is a continuing need for technologies that can quickly warm up gas purification devices. The present invention has been created to meet such demands. In other words, an object of the present invention is to increase the power supplied to the EHC while increasing the voltage supplied to the EHC while avoiding the discharge at the EHC in a situation where condensed water due to water vapor contained in the exhaust gas is generated (can be generated). An object of the present invention is to provide an EHC control method capable of quickly warming up a gas purification device.

The above object of the present invention is to
A first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC, which are disposed in an exhaust passage of the internal combustion engine;
A power source for supplying power to each of the first EHC and the second EHC;
A first circuit that supplies power from the power source only to the first EHC at a first voltage, a second circuit that supplies power from the power source only to the second EHC at a second voltage, and a first circuit from the power source to the first EHC and A switch mechanism that switches a second circuit that supplies power to the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.
Dew condensation determining means for determining whether or not dew condensation can occur in the first EHC or the second EHC;
First EHC determination means for determining whether or not power is to be supplied to the first EHC;
And a second EHC determination unit that determines whether or not power is to be supplied to the second EHC, and the switch mechanism is operated based on the determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit. A control device for switching a power supply circuit to any one of the first circuit, the second circuit, and the third circuit;
In an exhaust gas purification system comprising:
Determining whether or not the dew condensation determination means is in a state where dew condensation can occur in the first EHC or the second EHC;
A first EHC determination step of determining whether or not the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether the second EHC is in a state in which power should be supplied to the determination result in the second EHC determination step, and the determination results in the dew condensation determination step, the first EHC determination step, and the second EHC determination step. A switching step of switching the power supply circuit to any one of the first circuit, the second circuit, and the third circuit by operating the switch mechanism by the controller; If the determination result in step S3 is affirmative, the determination result in the third circuit is negative. If the determination result in step S1 is negative, and if the determination result in the first EHC determination step is positive, the dew condensation determination is performed in the first circuit. The determination result in step is negative, and the determination result in the second EHC determination step is positive A circuit switching step for switching the power supply circuit to the second circuit, respectively,
Is achieved by an EHC control method including:

  According to the EHC control method of the present invention, when it is determined by the dew condensation determination means that dew condensation is possible in the first EHC or the second EHC, the switch mechanism is operated by the control device, and the third circuit is activated. Thus, electric power is supplied to each of the first EHC and the second EHC at a relatively low third voltage and fourth voltage. As a result, when it is determined that the first EHC or the second EHC is in a state where condensation can occur, the discharge is suppressed in the first EHC or the second EHC.

  On the other hand, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the first EHC determination means that power is to be supplied to the first EHC. The switch mechanism is actuated by the control device, and power is supplied to the first EHC at a relatively high first voltage via the first circuit. Accordingly, the first exhaust gas purification device is warmed up more quickly by the first EHC to which a relatively high voltage is supplied.

  Also, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the second EHC determination means that power is to be supplied to the second EHC The switch mechanism is actuated by the control device, and power is supplied to the second EHC through the second circuit at a relatively high second voltage. Accordingly, the second exhaust gas purification device is warmed up more quickly by the second EHC to which a relatively high voltage is supplied.

  As described above, according to the EHC control method according to the present invention, supply to the EHC while avoiding discharge in the EHC in a situation where condensed water caused by water vapor contained in the exhaust gas is generated (can be generated). The electric power can be increased to warm up the exhaust gas purification device quickly.

It is a mimetic diagram showing a schematic structure of an exhaust-gas purification system concerning one embodiment of the present invention. It is a schematic diagram which shows schematic structure of the cross section of EHC. It is a mimetic diagram explaining composition and operation of a switch mechanism in an exhaust-gas purification system concerning one embodiment of the present invention. It is a flowchart which shows the flow of a series of processes performed in the EHC control method which concerns on one embodiment of this invention.

  As described above, the present invention increases the power supplied to the EHC while avoiding the discharge in the EHC in a situation where condensed water caused by water vapor contained in the exhaust gas is generated (can be generated), An object of the present invention is to provide an EHC control method capable of quickly warming up an exhaust gas purification device.

  As a result of intensive studies to achieve the above object, the present inventor can cause condensation in an exhaust gas purification system including a first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC. When in a state, power is supplied to the first EHC and the second EHC at a relatively low voltage, and when not in a state where condensation can occur, power is supplied to the first EHC and / or the second EHC at a relatively high voltage. As a result, the electric power supplied to the EHC is increased while avoiding the discharge at the EHC in the situation where the condensed water due to the water vapor contained in the exhaust gas is generated (can be generated). The inventors have found that the apparatus can be warmed up quickly and have arrived at the present invention.

(1) First aspect The first aspect of the present invention is:
A first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC, which are disposed in an exhaust passage of the internal combustion engine;
A power source for supplying power to each of the first EHC and the second EHC;
A first circuit that supplies power from the power source only to the first EHC at a first voltage, a second circuit that supplies power from the power source only to the second EHC at a second voltage, and a first circuit from the power source to the first EHC and A switch mechanism that switches a second circuit that supplies power to the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.
Dew condensation determining means for determining whether or not dew condensation can occur in the first EHC or the second EHC;
First EHC determination means for determining whether or not power is to be supplied to the first EHC;
And a second EHC determination unit that determines whether or not power is to be supplied to the second EHC, and the switch mechanism is operated based on the determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit. A control device for switching a power supply circuit to any one of the first circuit, the second circuit, and the third circuit;
In an exhaust gas purification system comprising:
Determining whether or not the dew condensation determination means is in a state where dew condensation can occur in the first EHC or the second EHC;
A first EHC determination step of determining whether or not the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether the second EHC is in a state in which power should be supplied to the determination result in the second EHC determination step, and the determination results in the dew condensation determination step, the first EHC determination step, and the second EHC determination step. A switching step of switching the power supply circuit to any one of the first circuit, the second circuit, and the third circuit by operating the switch mechanism by the controller; If the determination result in step S3 is affirmative, the determination result in the third circuit is negative. If the determination result in step S1 is negative, and if the determination result in the first EHC determination step is positive, the determination of condensation is performed in the first circuit. The determination result in step is negative, and the determination result in the second EHC determination step is positive A circuit switching step for switching the power supply circuit to the second circuit, respectively,
Is an EHC control method.

  The internal combustion engine is not limited to a specific type, and various types of internal combustion engines generally used as an internal combustion engine, such as a gasoline engine and a diesel engine, are assumed.

  Moreover, EHC refers to the catalyst with an electric heater as mentioned above. The first EHC and the second EHC can be, for example, an oxidation catalyst provided with an electric heater that generates heat when energized. The materials of the first EHC and second EHC base materials are not particularly limited as long as they satisfy the required specifications (for example, operating temperature, mechanical strength, etc.) of the first EHC and second EHC. In view of the installation purpose of the first EHC and the second EHC to quickly warm up the first exhaust gas purification device and the second exhaust gas purification device, the base material of the first EHC and the second EHC is a material having a small specific heat (for example, , Metal, etc.). Note that the configurations and materials of the first EHC and the second EHC may be the same or different.

  As described above, the first exhaust gas purification device and the second exhaust gas purification device refer to devices for purifying exhaust gas, such as various exhaust gas purification catalysts and PM collection filters. In addition, the first exhaust gas purification device and the second exhaust gas purification device are heated to a predetermined temperature in order to perform the original exhaust gas purification function or to sufficiently perform the regeneration process of the device. A device that needs to be heated. Therefore, the first exhaust gas purification device and the second exhaust gas purification device include the first EHC and the second EHC, respectively.

  Specific examples of the first exhaust gas purification device and the second exhaust gas purification device include, for example, a filter for collecting particulate matter (PM) such as a diesel particulate filter (DPF) (PM collection filter), Various exhaust gas purification catalysts that purify harmful substances such as CO, HC, NOx in exhaust (for example, diesel oxidation catalyst (DOC), selective reduction catalyst (SCR catalyst), NOx storage reduction catalyst (NSR catalyst), etc.) Can be mentioned. Further, as described above, the first exhaust gas purification device and the second exhaust gas purification device may be a combination of a PM collection filter and an exhaust gas purification catalyst (also referred to as “filter or the like”), or a plurality of types. It may be one that purifies harmful substances (for example, a three-way catalyst).

  The first exhaust gas purification device and the second exhaust gas purification device are disposed in the exhaust passage of the internal combustion engine as described above. Any of the first exhaust gas purification device and the second exhaust gas purification device may be arranged on the upstream side, and any of them may be arranged on the downstream side. For example, when the internal combustion engine is mounted on a vehicle, the first exhaust gas purification device and the second exhaust gas purification device are respectively disposed in a maniverter portion and an under floor portion (U / F portion, lower floor portion). Also good.

  As described above, in the present embodiment, the first exhaust gas purification device and the second exhaust gas purification device include the first EHC and the second EHC, respectively. Thereby, in this embodiment, compared with the case where only any one exhaust gas purification apparatus is equipped with EHC, an exhaust gas purification apparatus can be warmed up more efficiently. Specifically, when only one of the exhaust gas purifying devices (for example, the exhaust gas purifying device disposed in the maniverter unit) includes the EHC, the other exhaust gas purifying device (for example, U / F) is provided by the EHC. It is assumed that the exhaust gas purifying device disposed in the section is to be warmed up. In this case, the EHC that is the heat source is separated from the exhaust gas purification device to be warmed up, and a large amount of heat is released from the exhaust pipe that should conduct heat from the EHC, so that the other exhaust gas purification device can be warmed up quickly. Not only is it difficult to do so, but the power supplied to the EHC is wasted. On the contrary, the same applies to the case where only the exhaust gas purifying device disposed in the U / F section includes the EHC. On the other hand, in the present embodiment, the first exhaust gas purification device and the second exhaust gas purification device each include the first EHC and the second EHC, so that each EHC quickly warms up each exhaust gas purification device. In addition, there is an advantage that the wasteful use of electric power due to heat dissipation as described above does not occur.

  Next, the power source for supplying power to each of the first EHC and the second EHC is not particularly limited, and is appropriately selected according to the equipment (for example, vehicle, ship, etc.) on which the internal combustion engine is mounted. be able to. For example, when the facility on which the internal combustion engine is mounted is a vehicle, a power source mounted on the vehicle (for example, a power source generally used as a vehicle battery) can be used as the power source. In addition, the power source may be a voltage conversion circuit such as a DC / DC converter (DC-DC converter), for example, an AC-DC converter (AC input DC output power source), an inverter (DC input AC), if necessary. A power conversion circuit such as an output power source may be provided.

  The switch mechanism is a mechanism for switching to which of the first EHC and the second EHC power is supplied from the power source. Specifically, as described above, the switch mechanism supplies the first voltage from the power source to the first EHC only at the first voltage, and supplies the power from the power source to the second EHC only at the second voltage. And a third circuit that supplies power from the power source to the first EHC and the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.

  As described above, the first voltage is a voltage applied to the first EHC when power is supplied to the first EHC by the first circuit. Similarly, the second voltage is a voltage applied to the second EHC when power is supplied to the second EHC by the second circuit. On the other hand, the third voltage is a voltage applied to the first EHC when power is supplied to the first EHC by the third circuit, and the fourth voltage supplies power to the second EHC by the third circuit. This is the voltage applied to the second EHC.

  The first voltage and the second voltage are voltages necessary for the first EHC and the second EHC to quickly warm up the first exhaust gas purification device and the second exhaust gas purification device, respectively. May be different. Specific values of the first voltage and the second voltage are based on, for example, the specifications of the first EHC and the second EHC, the heat capacities of the first exhaust gas purification device and the second exhaust gas purification device to be warmed up, and the like. It can be set appropriately. In addition, the third voltage and the fourth voltage warm up the first exhaust gas purification device and the second exhaust gas purification device without causing discharge in the first EHC and the second EHC in a state where condensation can occur. Therefore, the voltages are respectively applied to the first EHC and the second EHC, and these may be the same or different. Furthermore, as described above, the third voltage and the fourth voltage are lower than the first voltage and the second voltage.

  In order to realize the various voltages (first voltage, second voltage, third voltage, and fourth voltage) as described above, each circuit (first circuit, second circuit, and third circuit) If necessary, for example, a voltage conversion circuit such as a DC / DC converter (DC-DC converter), an AC-DC converter (AC input DC output power supply), an inverter (DC input AC output power supply), etc. A power conversion circuit or the like may be provided.

  The dew condensation determination means determines whether or not dew condensation is possible in the first EHC or the second EHC. Here, the “state in which condensation can occur” refers to, for example, the outside temperature, humidity, atmospheric pressure, etc., among various conditions that define the surrounding environment of the equipment (for example, a vehicle) on which the internal combustion engine is mounted. It is determined based on a concept that includes environmental conditions that define the state of occurrence of dew condensation (including easiness of occurrence and generation speed) in exhaust gas, which can be represented by various physical quantities, control amounts, index values, and the like. In the present specification, the “state where condensation can occur” includes the state where condensation occurs.

  Therefore, the dew condensation determination means includes, for example, means (for example, various sensors) for detecting various physical quantities, control amounts, index values, etc. (for example, outside air temperature, humidity, atmospheric pressure, etc.) as described above. It is common. In addition, the dew condensation determination unit is configured to detect the first EHC based on a detection signal or the like that represents various physical quantities, control amounts, index values, etc. (for example, outside air temperature, humidity, atmospheric pressure, etc.) obtained from the detection unit. Alternatively, it is common to provide an algorithm for determining whether or not condensation is possible in the second EHC. The algorithm may be implemented as software (for example, a program or the like), or may be implemented as hardware (for example, an arithmetic circuit or the like). For example, in general, the algorithm is, for example, a ROM (Read Only Memory) or a RAM (Random Access Memory) provided in an electronic control unit (ECU) for performing various controls related to the internal combustion engine. The program is stored in the storage device as a program, and is implemented so as to be executed by a central processing unit (CPU: Central Processing Unit) included in the ECU. In addition, the ECU includes, for example, a communication port for receiving the detection signal.

  In addition, the conditions for the dew condensation determination means to determine whether or not dew condensation can occur in the first EHC or the second EHC are, for example, the above various physical quantities, control amounts, index values, etc. (for example, A data table (map) based on the outside air temperature, humidity, atmospheric pressure, etc.) can be created in advance by experiments or the like, and stored in the ROM or the like so that it can be referred to when the program is executed. Alternatively, as an example of a very simple determination condition, for example, whether or not dew condensation can occur in the first EHC or the second EHC depending on whether or not the temperature of the first EHC or the second EHC is lower than the boiling point of water. May be determined.

  Next, the first EHC determination unit and the second EHC determination unit determine whether power is to be supplied to the first EHC and the second EHC, respectively. The condition for determining whether or not to supply power to the first EHC and the second EHC is that the first exhaust gas purification device and the second exhaust gas purification device including the first EHC and the second EHC are any exhaust gas purification. It depends on whether it is a device.

  Specific examples of the first exhaust gas purification device and the second exhaust gas purification device include, for example, a filter that collects particulate matter (PM) such as a diesel particulate filter (DPF) (PM collection filter), Various exhaust gas purification catalysts (such as diesel oxidation catalyst (DOC), selective reduction catalyst (SCR catalyst), NOx storage reduction catalyst (NSR catalyst), etc.) that purify harmful substances such as CO, HC, NOx in the exhaust Can be mentioned. Further, as described above, the first exhaust gas purification device and the second exhaust gas purification device may be a combination of a PM collection filter and an exhaust gas purification catalyst (also referred to as “filter or the like”), or a plurality of types. It may be one that purifies harmful substances (for example, a three-way catalyst).

  As described above, the exhaust gas purification catalyst generally does not sufficiently exhibit the exhaust gas purification function of the catalyst at normal temperature (because the activation temperature of the catalyst has not been reached). That is, in order for the exhaust gas purification catalyst to exhibit its original exhaust gas purification function, these catalysts need to reach a predetermined temperature. Therefore, when the first exhaust gas purification device or the second exhaust gas purification device is such an exhaust gas purification catalyst, for example, in the exhaust gas detected by various sensors (for example, CO sensor, HC sensor, etc.) When the concentration of the harmful substance exceeds a predetermined threshold value, electric power should be supplied to the first EHC or the second EHC. That is, when the first exhaust gas purification device or the second exhaust gas purification device is an exhaust gas purification catalyst as described above, for example, the concentration of harmful substances in the exhaust gas detected by various sensors or the like is predetermined. Whether or not the threshold is exceeded is a condition for determining whether or not power is to be supplied to the first EHC or the second EHC.

  For example, when the first exhaust gas purification device is a PM collection filter such as DPF, the amount of PM collected increases and the exhaust passage resistance increases, and the differential pressure across the filter exceeds a specified value. In this case, it is necessary to raise the temperature of the PM trapping filter to a predetermined temperature in order to perform the PM regeneration process. Therefore, when the first exhaust gas purification device is a PM trapping filter such as a DPF, for example, when the differential pressure across the filter exceeds a specified value, power is supplied to the first EHC. That is, when the first exhaust gas purification device is a PM collection filter such as a DPF, for example, whether or not the differential pressure across the filter exceeds a specified value is in a state where power should be supplied to the first EHC. This is a condition for determining whether or not.

  Further, for example, when the second exhaust gas purification device is an NSR catalyst, the NOx occlusion amount estimated by a model calculation based on a test mapping of the exhaust gas state in the engine use range or detected by a NOx sensor, for example. When the NOx storage amount estimated based on the NOx concentration in the exhaust gas exceeds a predetermined threshold value, a rich spike (excess fuel supply) is generated in the internal combustion engine and the NSR catalyst is It is necessary to purify the NSR catalyst by reducing the adsorbed NOx with the fuel that has been heated to the temperature and temporarily increased. When the SOx accumulation amount calculated from the rotational speed of the internal combustion engine and the fuel injection amount exceeds a predetermined threshold, a rich spike (excess fuel supply) is also generated in the internal combustion engine and the NSR catalyst is set to a predetermined temperature. It is necessary to perform a SOx regeneration process for SOx poisoning of the NSR catalyst. Therefore, when the second exhaust gas purification device is an NSR catalyst, for example, when it is estimated that the NOx storage amount or SOx accumulation amount in the NSR exceeds a predetermined threshold value, power should be supplied to the second EHC. It becomes a state. That is, when the second exhaust gas purification device is an NSR catalyst, for example, whether or not it is estimated that the NOx occlusion amount or the SOx accumulation amount in the NSR exceeds a predetermined threshold is supplied to the second EHC. This is a condition for determining whether or not it is in a state to be performed.

  As described above, the condition for determining whether or not to supply power to the first EHC and the second EHC is the first exhaust gas purification device and the second exhaust gas purification device including the first EHC and the second EHC. Depends on what type of exhaust gas purifying device is. That is, the condition for determining whether or not to supply power to the first EHC and the second EHC is, for example, that the first exhaust gas purification device and the second exhaust gas purification device including the first EHC and the second EHC have Judgment is made based on whether or not it is determined that it is necessary to purify the harmful substances, or whether it is necessary to regenerate the first exhaust gas purification device and the second exhaust gas purification device including the first EHC and the second EHC. Is done.

  Accordingly, the first EHC determination unit and the second EHC determination unit detect, for example, various physical quantities, control amounts, or index values (for example, outside air temperature, humidity, atmospheric pressure, etc.) that define the determination conditions as described above. It is common to provide means (for example, various sensors). In addition, the first EHC determination unit and the second EHC determination unit may generate detection signals representing various physical quantities, control amounts, index values, etc. (for example, outside air temperature, humidity, atmospheric pressure, etc.) obtained from the detection unit. In general, an algorithm for determining whether or not power is to be supplied to the first EHC or the second EHC, respectively, is provided. The algorithm may be implemented as software (for example, a program or the like), or may be implemented as hardware (for example, an arithmetic circuit or the like). For example, in general, the algorithm is implemented so as to be stored as a program in a storage device such as a ROM or a RAM provided in an ECU for performing various controls relating to the internal combustion engine and executed by a CPU provided in the ECU. Is done. In addition, the ECU includes, for example, a communication port for receiving the detection signal.

  Next, the control device operates the switch mechanism based on the determinations by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit, so that the control device is set to any one of the first circuit, the second circuit, and the third circuit. Switch the power supply circuit. Specifically, in the control device, when the determination result by the dew condensation determination unit is affirmative, the determination result by the dew condensation determination unit is negative in the third circuit, and the determination result by the first EHC determination unit is affirmative. In this case, the power supply circuit is switched to the first circuit when the determination result by the dew condensation determination means is negative and the determination result by the second EHC determination means is affirmative.

  Therefore, the control device receives, for example, a signal corresponding to the result of determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit, and the first power supply circuit to each EHC is set based on the signal. A control signal (instruction signal) for switching to any one of the circuit, the second circuit, and the third circuit is sent to the switch mechanism. That is, the control device, for example, based on the determination results received from the dew condensation determination means, the first EHC determination means, and the second EHC determination means (corresponding signals), the power supply circuit to each EHC, the first circuit, It is common to provide an algorithm for determining which of the second circuit and the third circuit to switch to. The algorithm may be implemented as software (for example, a program or the like), or may be implemented as hardware (for example, an arithmetic circuit or the like). For example, in general, the algorithm is implemented so as to be stored as a program in a storage device such as a ROM or a RAM provided in an ECU for performing various controls relating to the internal combustion engine and executed by a CPU provided in the ECU. Is done. In addition, the ECU sends, for example, a control signal (instruction signal) indicating whether the power supply circuit to each EHC is switched to the first circuit, the second circuit, or the third circuit to the switch mechanism. A communication port is provided.

  As described above, the exhaust gas purification system includes the first exhaust gas purification device including the first EHC, the second exhaust gas purification device including the second EHC, the power source, the switch mechanism, the dew condensation determination unit, the first EHC determination unit, and the second EHC. A determination unit and a control device are provided. The EHC control method according to the first aspect of the present invention is executed in such an exhaust gas purification system.

As described above, the EHC control method according to the first aspect of the present invention is as follows.
Determining whether or not the dew condensation determination means is in a state where dew condensation can occur in the first EHC or the second EHC;
A first EHC determination step of determining whether or not the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether the second EHC is in a state in which power should be supplied to the determination result in the second EHC determination step, and the determination results in the dew condensation determination step, the first EHC determination step, and the second EHC determination step. A switching step of switching the power supply circuit to any one of the first circuit, the second circuit, and the third circuit by operating the switch mechanism by the controller; If the determination result in step S3 is affirmative, the determination result in the third circuit is negative. If the determination result in step S1 is negative, and if the determination result in the first EHC determination step is positive, the determination of condensation is performed in the first circuit. The determination result in step is negative, and the determination result in the second EHC determination step is positive A circuit switching step for switching the power supply circuit to the second circuit, respectively,
including.

  The details of each step included in the EHC control method are as already described in the above description of each component included in the exhaust gas purification system to which the EHC control method according to the first aspect of the present invention is applied. is there. The order of execution of the dew condensation determination step, first EHC determination step, and second EHC determination step is not necessarily limited to the above.

  In the circuit switching step, the power supply circuit to each EHC has a third circuit when the determination result in the dew condensation determination step is affirmative, and the determination result in the dew condensation determination step is negative and the first EHC determination When the determination result in the step is affirmative, the first circuit is switched to, and when the determination result in the dew condensation determination step is negative and the determination result in the second EHC determination step is affirmative, the circuit is switched to the second circuit. At this time, when the determination result in the dew condensation determination step is negative, the first circuit supplying power to the first EHC with the first voltage and the second EHC using the second voltage as the power supply circuit to each EHC. It is not excluded that both of the second circuits for supplying are selected. That is, in a state where it is not determined that condensation can occur, power is supplied to the first EHC at the first voltage and the second EHC at the second voltage, and these EHCs are simultaneously energized at a high voltage. Alternatively, only one of the first EHC and the second EHC may be energized with a high voltage.

  As described above, the EHC control method according to the first aspect of the present invention includes the condensation determination step, the first EHC determination step, the second EHC determination step, and the circuit switching step. The processing routine for executing these steps may also be implemented as software (for example, a program) or may be implemented as hardware (for example, an arithmetic circuit). For example, in general, the processing routine is stored as a program in a storage device such as a ROM or a RAM provided in an ECU for performing various controls related to the internal combustion engine, and is executed by a CPU provided in the ECU. Implemented. Furthermore, the processing routine for executing each step included in the EHC control method according to the first aspect of the present invention can be executed by the ECU as an interrupt process for each predetermined crank angle, for example.

  As described above, the EHC control method according to the first aspect of the present invention and the configuration of the exhaust gas purification system to which the method is applied have been described in detail. As described above, in the EHC control method according to the first aspect of the present invention, when it is determined by the dew condensation determining means that the dew condensation can occur in the first EHC or the second EHC, the switch mechanism is operated by the control device. Is operated, and electric power is supplied to each of the first EHC and the second EHC through the third circuit at a relatively low third voltage and fourth voltage. As a result, when it is determined that the first EHC or the second EHC is in a state where condensation can occur, the discharge is suppressed in the first EHC or the second EHC.

  On the other hand, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the first EHC determination means that power is to be supplied to the first EHC. The switch mechanism is actuated by the control device, and power is supplied to the first EHC at a relatively high first voltage via the first circuit. Accordingly, the first exhaust gas purification device is warmed up more quickly by the first EHC to which a relatively high voltage is supplied.

  Also, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the second EHC determination means that power is to be supplied to the second EHC The switch mechanism is actuated by the control device, and power is supplied to the second EHC through the second circuit at a relatively high second voltage. Accordingly, the second exhaust gas purification device is warmed up more quickly by the second EHC to which a relatively high voltage is supplied.

  As described above, in the EHC control method according to the first aspect of the present invention, the discharge to EHC is avoided while avoiding the discharge in EHC in the situation where the condensed water caused by the water vapor contained in the exhaust gas is generated (can be generated). The object of the present invention described at the beginning, which is to quickly warm up the exhaust gas purification device by increasing the supply power voltage, is achieved.

(2) Second Aspect As described above, in the EHC control method according to the present invention, when it is determined by the condensation determination means that the first EHC or the second EHC is in a state where condensation can occur. The switch mechanism is operated by the control device, and power is supplied to each of the first EHC and the second EHC through the third circuit at a relatively low third voltage and fourth voltage. As a result, when it is determined that the first EHC or the second EHC is in a state where condensation can occur, the discharge is suppressed in the first EHC or the second EHC.

  In this case, as a specific means for applying the third voltage and the fourth voltage, which are relatively low voltages, to the first EHC and the second EHC through the third circuit, as described above, for example, a DC / DC converter, for example, A voltage conversion circuit such as a (DC-DC converter) or a power conversion circuit such as an AC-DC converter (AC input DC output power supply) or an inverter (DC input AC output power supply) may be provided in the third circuit. . However, providing such an additional circuit complicates and enlarges the configuration of the exhaust gas purification system to which the EHC control method according to the first aspect of the present invention is applied, and increases the manufacturing cost of the system. It leads to. Therefore, it is desirable to apply the third voltage and the fourth voltage, which are relatively low voltages, to the first EHC and the second EHC, respectively, through the third circuit without providing the additional circuit as described above.

That is, the second aspect of the present invention is
The EHC control method according to the first aspect of the present invention is the EHC control method according to the third circuit, wherein the first EHC and the second EHC are connected in series in the third circuit.

  As described above, in the second aspect of the present invention, in the third circuit, the first EHC and the second EHC are connected in series. As a result, the voltage applied from the power source is distributed according to the resistance value of each of the first EHC and the second EHC. That is, according to the second aspect of the present invention, the voltage applied to each of the first EHC and the second EHC can be reduced without providing the additional circuit as described above in the third circuit.

(3) Third aspect By the way, as described above, the equipment on which the internal combustion engine to which the EHC control method according to the present invention is applied includes, for example, a vehicle and a ship. As a matter of course, the application target of the EHC control method according to the present invention is not limited to these. For example, the EHC control method according to the present invention is applied to equipment other than a moving body such as a generator or a compressor. You may apply to the internal combustion engine mounted. Thus, the EHC control method according to the present invention can be applied to internal combustion engines mounted on a wide variety of facilities. Among them, from the viewpoint of protecting the global environment, one of the vehicles that are most strongly desired to reduce harmful substances contained in exhaust gas is a vehicle.

  As an exhaust gas purifying device mounted on a vehicle using an internal combustion engine as a power source, for example, a so-called maniverter (manifold converter) disposed directly connected to an exhaust manifold, and an under-floor portion of the vehicle (downstream of the maniverter) ( And an underfloor catalyst (U / F catalyst, underfloor catalyst) disposed in an exhaust passage that passes through the U / F portion and the lower floor). In general, an oxidation catalyst that can oxidize HC and CO from a low temperature range is used as the manipulator, and a three-way catalyst, a NOx storage reduction catalyst, or the like is often used as the underfloor catalyst.

  Since the maniverter is directly connected to the exhaust manifold close to the internal combustion engine body, the catalyst activation temperature (for example, about 400 ° C. or more) can be easily secured if the internal combustion engine or the like is warmed up. It has the merit of being able to. As a result, in a low temperature range such as when the internal combustion engine is started, the manipulator is activated early, and the temperature of the exhaust gas rises due to heat generated by the reaction. As a result, the underfloor catalyst is also activated at an early stage, so that there is a merit that emission in a low temperature region is improved.

  However, as described above, since the demand for reducing harmful substances contained in the exhaust gas of the internal combustion engine has become increasingly strong, the temperature of the exhaust gas purifying device has a predetermined temperature, such as during a cold start of the internal combustion engine. When the temperature of the exhaust gas has not been reached, energization of the EHC promotes the warm-up of the exhaust gas purification device disposed on the downstream side of the EHC more than before, and the original exhaust gas purification function There is a need for a technology that makes it possible to exhibit the image at an earlier stage and to perform the regeneration process quickly.

Therefore, the third aspect of the present invention is
The EHC control method according to any one of the first aspect and the second aspect of the present invention, wherein the first catalyst is a manipulator and the second catalyst is an underfloor catalyst. It is a control method.

  The EHC control method according to the third aspect of the present invention is due to the water vapor contained in the exhaust gas while enjoying the above-mentioned merits already recognized in the prior art by adopting the above configuration. A further advantage provided by the present invention is that the power supplied to the EHC is increased to quickly warm up the exhaust gas purification device while avoiding the discharge at the EHC in the situation where condensate is generated (can be generated). You can enjoy the benefits.

(4) Fourth Embodiment Although several embodiments of the EHC control method according to the present invention have been described in detail above, as described above, the present invention purifies exhaust gas of an internal combustion engine that uses the EHC control method. Also related to the system.

That is, the fourth aspect of the present invention is
A first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC, which are disposed in an exhaust passage of the internal combustion engine;
A power source for supplying power to each of the first EHC and the second EHC;
A first circuit that supplies power from the power source only to the first EHC at a first voltage, a second circuit that supplies power from the power source only to the second EHC at a second voltage, and a first circuit from the power source to the first EHC and A switch mechanism that switches a third circuit that supplies power to each of the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.
Dew condensation determining means for determining whether or not dew condensation can occur in the first EHC or the second EHC;
First EHC determination means for determining whether or not power is to be supplied to the first EHC;
And a second EHC determination unit that determines whether or not power is to be supplied to the second EHC, and the switch mechanism is operated based on the determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit. A control device for switching a power supply circuit to any one of the first circuit, the second circuit, and the third circuit;
An exhaust gas purification system comprising:
Determining whether the condensation determination means is in a state where condensation can occur in the first EHC or the second EHC;
Determining whether the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether or not the second EHC should be supplied with power, and based on the determination results by the dew condensation determination means, the first EHC determination means, and the second EHC determination means, When the switch mechanism is operated by the control device to switch the power supply circuit to any one of the first circuit, the second circuit, and the third circuit, the determination result by the dew condensation determination means is affirmative When the determination result by the dew condensation determination means is negative in the third circuit and the determination result by the first EHC determination means is affirmative, the determination result by the dew condensation determination means is negative in the first circuit. And when the determination result by the second EHC determination means is affirmative, the power supply circuit is switched to the second circuit, respectively.
It is an exhaust gas purification system characterized by this.

  As described above, the exhaust gas purification system according to the fourth aspect of the present invention includes the first exhaust gas purification device including the first EHC, the second exhaust gas purification device including the second EHC, the power supply, the switch mechanism, the dew condensation determination unit, 1st EHC determination means, 2nd EHC determination means, and a control apparatus are provided. Since the configuration and operation of these individual components have been described in detail in the description of the EHC control method according to the first aspect of the present invention, description thereof is omitted here.

  In the exhaust gas purification system according to the fourth aspect of the present invention, when it is determined by the dew condensation determination means that dew condensation can occur in the first EHC or the second EHC, the switch mechanism is operated by the control device, Electric power is supplied to each of the first EHC and the second EHC through the third circuit at a relatively low third voltage and fourth voltage. As a result, when it is determined that the first EHC or the second EHC is in a state where condensation can occur, the discharge is suppressed in the first EHC or the second EHC.

  On the other hand, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the first EHC determination means that power is to be supplied to the first EHC. The switch mechanism is actuated by the control device, and power is supplied to the first EHC at a relatively high first voltage via the first circuit. Accordingly, the first exhaust gas purification device is warmed up more quickly by the first EHC to which a relatively high voltage is supplied.

  Also, when it is determined by the dew condensation determination means that there is no dew condensation in the first EHC or the second EHC, and when it is determined by the second EHC determination means that power is to be supplied to the second EHC The switch mechanism is actuated by the control device, and power is supplied to the second EHC through the second circuit at a relatively high second voltage. Accordingly, the second exhaust gas purification device is warmed up more quickly by the second EHC to which a relatively high voltage is supplied.

  As described above, in the exhaust gas purification system according to the fourth aspect of the present invention, to the EHC while avoiding the discharge in the EHC in a situation where condensed water due to water vapor contained in the exhaust gas is generated (can be generated). The object of the present invention described at the beginning is achieved, in which the supply power is increased to quickly warm up the exhaust gas purification device.

(5) Fifth aspect As described above, in the exhaust gas purification system to which the EHC control method according to the present invention is applied, the dew condensation determination means causes the dew condensation to occur in the first EHC or the second EHC. If it is determined that there is, the control mechanism activates the switch mechanism, and power is supplied to each of the first EHC and the second EHC at a relatively low third voltage and fourth voltage via the third circuit. . As a result, when it is determined that the first EHC or the second EHC is in a state where condensation can occur, the discharge is suppressed in the first EHC or the second EHC.

  In this case, as a specific means for applying the third voltage and the fourth voltage, which are relatively low voltages, to the first EHC and the second EHC through the third circuit, as described above, for example, a DC / DC converter, for example, A voltage conversion circuit such as a power conversion circuit such as an AC-DC converter inverter may be provided in the third circuit. However, providing such an additional circuit complicates and enlarges the configuration of the exhaust gas purification system according to the fourth aspect of the present invention, and increases the manufacturing cost of the system. Therefore, it is desirable to apply the third voltage and the fourth voltage, which are relatively low voltages, to the first EHC and the second EHC, respectively, through the third circuit without providing the additional circuit as described above.

That is, the fifth aspect of the present invention is
An exhaust gas purification system according to the fourth aspect of the present invention, wherein the first EHC and the second EHC are connected in series in the third circuit. .

  As described above, in the fifth aspect of the present invention, in the third circuit, the first EHC and the second EHC are connected in series. As a result, the voltage applied from the power source is distributed according to the resistance value of each of the first EHC and the second EHC. That is, according to the second aspect of the present invention, the voltage applied to each of the first EHC and the second EHC can be reduced without providing the additional circuit as described above in the third circuit.

(6) Sixth aspect By the way, as described above, examples of the equipment on which the internal combustion engine to which the exhaust gas purification system according to the present invention is applied include vehicles and ships. As a matter of course, the application target of the EHC control method according to the present invention is not limited to these. For example, the exhaust gas purification system according to the present invention is installed in a facility other than a moving body such as a generator or a compressor. You may apply to the internal combustion engine mounted in. Thus, the exhaust gas purification system according to the present invention can be applied to internal combustion engines mounted on a wide variety of facilities. Among them, from the viewpoint of protecting the global environment, one of the vehicles that are most strongly desired to reduce harmful substances contained in exhaust gas is a vehicle.

  As described above, as an exhaust gas purifying device mounted on a vehicle using an internal combustion engine as a power source, for example, a so-called maniverter disposed directly connected to an exhaust manifold, and an under floor portion of the vehicle hitting the downstream of the maniverter And an underfloor catalyst disposed in an exhaust passage that passes through. In general, an oxidation catalyst that can oxidize HC and CO from a low temperature range is used as the manipulator, and a three-way catalyst, a NOx storage reduction catalyst, or the like is often used as the underfloor catalyst.

  Since the maniverter is directly connected to the exhaust manifold close to the internal combustion engine body, the catalyst activation temperature (for example, about 400 ° C. or more) can be easily secured if the internal combustion engine or the like is warmed up. It has the merit of being able to. As a result, in a low temperature range such as when the internal combustion engine is started, the manipulator is activated early, and the temperature of the exhaust gas rises due to heat generated by the reaction. As a result, the underfloor catalyst is also activated at an early stage, so that there is a merit that emission in a low temperature region is improved.

  However, as described above, since the demand for reducing harmful substances contained in the exhaust gas of the internal combustion engine has become increasingly strong, the temperature of the exhaust gas purifying device has a predetermined temperature, such as during a cold start of the internal combustion engine. When the temperature of the exhaust gas has not been reached, energization of the EHC promotes the warm-up of the exhaust gas purification device disposed on the downstream side of the EHC more than before, and the original exhaust gas purification function There is a need for a technology that makes it possible to exhibit the image at an earlier stage and to perform the regeneration process quickly.

Accordingly, the sixth aspect of the present invention provides
The exhaust gas purification system according to any one of the fourth aspect and the fifth aspect of the present invention, wherein the first catalyst is a manipulator and the second catalyst is an underfloor catalyst. It is a gas purification system.

  The exhaust gas purification system according to the sixth aspect of the present invention is configured as described above, and further enjoys the above-mentioned merit already recognized in the prior art, and is further attributed to water vapor contained in the exhaust gas. It is provided by the present invention that the electric power supplied to the EHC is increased and the exhaust gas purification device is quickly warmed up while avoiding the discharge in the EHC in the situation where the condensed water is generated (can be generated) You can enjoy further benefits.

  As described above, according to the EHC control method and the exhaust gas purification system using the method according to the present invention, when it is determined that dew condensation can occur in the first or second EHC, it is relatively low. Electric power is supplied to each of the first EHC and the second EHC by voltage. On the other hand, if it is determined that the first or second EHC is not in a state where condensation can occur, and if it is determined that power should be supplied to the first and / or second EHC, the voltage is set to a relatively high voltage. Thus, electric power is supplied to the first and / or second EHC. As a result, the electric power supplied to the EHC is increased while avoiding the discharge in the EHC in a situation where the condensate caused by the water vapor contained in the exhaust gas is generated (can be generated), and the exhaust gas purification device can be quickly operated. Can warm up.

  Hereinafter, an EHC control method according to some embodiments of the present invention and an exhaust gas purification system using the method will be described with reference to the accompanying drawings. However, the following description is for illustrative purposes only, and the scope of the present invention should not be construed as being limited to the following description.

(1) Schematic Configuration of Exhaust Gas Purification System As described above, FIG. 1 is a schematic diagram showing a schematic configuration of an exhaust gas purification system according to one embodiment of the present invention. As shown in FIG. 1, the exhaust gas purification system according to the present embodiment is disposed immediately below an exhaust manifold 33 that constitutes an exhaust passage of the internal combustion engine 30, and includes a first EHC 11, an exhaust gas purification element 12, and an exhaust gas purification. A power source for supplying power to the first exhaust gas purification device 10 including the element 13, the second exhaust purification device 20 including the second EHC 21 and the exhaust gas purification element 22, the first EHC 11 and the second EHC 21 (see FIG. A first circuit that supplies power from the power source to the first EHC 11 only at the first voltage, a second circuit that supplies power from the power source to the second EHC 21 only at the second voltage, and the first EHC 11 and the second EHC 21, respectively. Switch mechanism for switching a third circuit that supplies power at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively (whatever (Not shown), dew condensation determining means (not shown) for determining whether or not the first EHC 11 or the second EHC 21 is in a state where condensation can occur, and whether or not the first EHC 11 is in a state where power should be supplied. First EHC determination means (not shown) for determining, second EHC determination means (not shown) for determining whether or not power is to be supplied to the second EHC 21, and a switch mechanism based on the determination by these determination means And a control device (not shown) for switching the power supply circuit. In FIG. 1, the left arrow (41) indicates the flow of intake air, and the right arrow (42) indicates the flow of exhaust gas.

  In the present embodiment, DOC is assumed as the exhaust gas purification element 12, DPF as the exhaust gas purification element 13, and SCR as the exhaust gas purification element 22, and the SCR as the exhaust gas purification element 22 is assumed. In order to supply the reducing agent (for example, urea), the reducing agent addition valve 23 is disposed in the exhaust passage 34 upstream of the second exhaust purification device 20. With this configuration, the exhaust gas purification system in the present embodiment oxidizes various harmful substances (for example, CO, HC, and NO) contained in the exhaust gas, collects PM (particulate matter), and collects NOx ( The exhaust gas is purified by reducing (nitrogen oxide).

  Here, in order to oxidize various harmful substances and reduce NOx, as described above, each exhaust gas purification element (in this embodiment, the exhaust gas purification element 12 and the exhaust gas purification element 22 are configured. DOC and SCR) need to reach a predetermined temperature (catalyst activation temperature). Further, as described above, when the differential pressure across the PM collection filter (in this embodiment, the DPF constituting the exhaust gas purification element 13) exceeds a specified value, it is collected by the PM collection filter. The PM regeneration process for removing the burned PM by burning is performed. In order to perform this PM regeneration process, the PM collection filter needs to reach a predetermined temperature.

  Therefore, for example, when the temperature of the exhaust gas purification device 10 or the exhaust gas purification device 20 does not reach a predetermined temperature, such as when the internal combustion engine 30 is cold started, the exhaust gas is sufficiently purified in the state as it is. Therefore, harmful substances are released into the atmosphere. Therefore, electric power is supplied to the first EHC 11 or the second EHC 21, and the exhaust gas purification device 10 or the exhaust gas purification device 20 is quickly heated. Thereby, even when the temperature of the exhaust gas purification device 10 or the exhaust gas purification device 20 does not reach a predetermined temperature, for example, when the internal combustion engine 30 is cold started, the exhaust gas is exhausted by the first EHC 11 or the second EHC 21. The temperature of the gas purification device 10 or the exhaust gas purification device 20 is quickly raised, and a state in which the original exhaust gas purification function can be exhibited is quickly achieved.

  As shown in FIG. 1, the internal combustion engine 30 is composed of an in-line four-cylinder engine 31 equipped with a turbo-type supercharger with an intercooler. As described above, the internal combustion engine to which the present invention is applied is The present invention is not limited to a specific type, and the present invention can be applied to various types of internal combustion engines used as internal combustion engines.

(2) Outline of EHC As described above, FIG. 2 is a schematic diagram showing a schematic configuration of a cross section of a catalyst with an electric heater (EHC). As shown in FIG. 2, the first EHC 11 and the second EHC 21 in the present embodiment are oxidation catalysts provided with an electric heater (electric heating wire) that generates heat when energized. Further, the base material of the first EHC 11 and the second EHC 21 is a material having a small specific heat in view of the installation purpose of the first EHC 11 and the second EHC 21 to quickly warm up the first exhaust gas purification device 10 and the second exhaust gas purification device 20. It was a metal. Thereby, when electric power is supplied to the heating wires provided in the first EHC 11 and the second EHC 21, the first EHC 11 and the second EHC 21 are quickly heated, and as a result, the first exhaust gas purification device 10 and the second exhaust gas purification. The apparatus 20 is quickly heated.

  On the other hand, in a state where condensation can occur in the first EHC 11 or the second EHC 21, if a high voltage is applied to the first EHC 11 or the second EHC 21 to increase the temperature more quickly, the base material of the first EHC 11 or the second EHC 21 becomes a metal. In particular, in the region where condensation occurs, discharge is likely to occur, which may lead to a decrease in the reliability of the first EHC 11 or the second EHC 21. As described in the present specification, the present invention increases the power supplied to the first EHC 11 or the second EHC 21 while suppressing the occurrence of discharge in such a case, and warms up the exhaust gas purification device more quickly. It is something to try.

(3) Configuration and Operation of Switch Mechanism As described above, FIG. 3 is a schematic diagram illustrating the configuration and operation of the switch mechanism in the exhaust gas purification system according to one embodiment of the present invention. As shown in FIG. 3, the first exhaust gas purification device 10 includes a first EHC 11, and further includes an exhaust gas purification element 12 adjacent to the first EHC 11. Similarly, the second exhaust gas purification device 20 includes a second EHC 21, and further includes an exhaust gas purification element 22 adjacent to the second EHC 21. In FIG. 3, the exhaust gas purification element 13 included in the first exhaust gas purification device 10 is not shown for the purpose of simplifying the drawing, but this example is illustrated by the first exhaust gas purification device. It is not excluded that 10 includes a plurality of exhaust gas purification elements. Further, the first EHC 11 provided in the first exhaust gas purification device 10 and the second EHC 21 provided in the second exhaust gas purification device 20 are connected in series on a conducting wire from the terminal A to the terminal C, and the first EHC 11 and the second EHC 21 Wiring from the conducting wire connecting the terminal to the terminal B is separately provided.

  On the other hand, a power source (battery) 50 is disposed in the upper part of FIG. 3 and wirings extending from each of the plus (+) terminal and the minus (−) terminal to each of two terminals represented by black circles. Is provided. These plus (+) and minus (−) terminals and the above-described A terminal to C terminal are configured to be switched between a connection state and a cutoff state by a switch that can be switched. Specifically, in this embodiment, the plus (+) terminal is connected to either the A terminal or the B terminal, and the minus (−) terminal is connected to either the B terminal or the C terminal. It is configured. Of course, if both the plus (+) terminal and the minus (-) terminal are connected to the B terminal at the same time, a short circuit will occur, so these terminals must not be connected to the B terminal at the same time.

  The switching of the connection state between the plus (+) terminal and the minus (−) terminal and the A terminal to the C terminal will be described in detail below. First, as shown in FIG. 3, when the plus (+) terminal and the A terminal are connected and the minus (−) terminal and the B terminal are connected, the power supplied from the power supply 50 is only the first EHC 11. To be supplied. That is, the power supply circuit in this state (that is, the circuit from the terminal A to the terminal B) corresponds to the “first circuit” in the present invention. Next, when the plus (+) terminal and the B terminal are connected and the minus (−) terminal and the C terminal are connected, the power supplied from the power supply 50 is supplied only to the second EHC 21. That is, the power supply circuit in this state (that is, the circuit from the terminal B to the terminal C) corresponds to the “second circuit” in the present invention.

  Further, when the plus (+) terminal and the A terminal are connected and the minus (−) terminal and the C terminal are connected, the power supplied from the power supply 50 is transmitted from the terminal A to the terminal C. Via the first EHC 11 and the second EHC 21. In this case, as described above, the first EHC 11 and the second EHC 21 are connected in series on the conducting wire from the terminal A to the terminal C. As a result, the voltage applied from the power supply 50 is distributed according to the resistance values of the first EHC 11 and the second EHC 21, so the above-mentioned “first circuit” (circuit A-B: terminal A to terminal B)) or “second circuit” (circuit B-C: a circuit from terminal B to terminal C), compared to the case where a voltage is applied to the first EHC 11 or the second EHC 21, the first EHC 11 and The voltage applied to each of the second EHC 21 can be reduced. That is, the power supply circuit in this state (circuit AC: circuit from terminal A to terminal C) corresponds to the “third circuit” in the present invention.

  As described above, in this embodiment, the power supply 50 is switched from the power supply 50 by switching the connection state and the cutoff state between the plus (+) terminal and the minus (−) terminal and the A terminal to the C terminal by the switch. The power supply circuit to the 1EHC 11 and / or the second EHC 21 can be switched to any one of “first circuit”, “second circuit”, and “third circuit”. That is, the switch 60 surrounded by a dotted line in FIG. 3 corresponds to the “switch mechanism” as referred to in the present invention (hence, also referred to as “switch mechanism 60” hereinafter).

(4) Configuration and operation of the switch mechanism In the EHC control method according to the present embodiment, when it is determined that the first EHC 11 or the second EHC 21 is in a state where condensation can occur, the power supply circuit to the EHC is connected to the third circuit. Switching to the circuit (circuits A to C), power is supplied to each of the first EHC 11 and the second EHC 21 at a relatively low voltage (third voltage and fourth voltage). On the other hand, if it is determined that the first EHC 11 and the second EHC 21 are not in a state where condensation can occur and if it is determined that power should be supplied to the first EHC 11 or the second EHC 21, a power supply circuit to the EHC is provided. Switching to the first circuit (circuit A-B) or the second circuit (circuit B-C), power is supplied to the first EHC 11 or the second EHC 21 at a relatively high voltage (first voltage or second voltage).

  Such a series of processes will now be described with reference to FIG. As described above, FIG. 4 is a flowchart showing a flow of a series of processes executed in the EHC control method according to one embodiment of the present invention. The series of processes shown in the flowchart can be repeatedly executed at a sufficiently fast cycle, for example, using a clock built in an electronic control unit (ECU) (not shown).

  As shown in FIG. 4, in the present embodiment, first, in step S <b> 1, it is determined whether or not dew condensation can occur in the first EHC 11 or the second EHC 21 by dew condensation determination means (not shown). The determination is obtained in advance (by experiment or the like) based on detection signals obtained from sensors or the like that detect various physical quantities (external temperature, humidity, and atmospheric pressure, and temperatures of the first EHC 11 and the second EHC 21), for example. And a program configured to refer to a data map that associates the physical quantity with the presence or absence of condensation. The data map and program can be stored in, for example, a ROM provided in the ECU. Alternatively, as an example of extremely simple determination conditions, for example, dew condensation occurs in the first EHC or the second EHC depending on whether the temperature of the first EHC 11 or the second EHC 21 is lower than the boiling point of water (100 ° C. at 1 atm). It may be determined whether it is in a state to obtain.

  If it is determined in step S1 that the first EHC 11 or the second EHC 21 is in a state where condensation can occur (step S1: Yes), a control mechanism (not shown) operates the switch mechanism 60 in step S2. The power supply circuit from the power supply 50 is switched to the third circuit (that is, the circuit A-C), and voltages corresponding to the respective resistance values are applied to both the first EHC 11 and the second EHC 21.

  On the other hand, when it is determined in step S1 that the first EHC 11 or the second EHC 21 is not in a state where condensation can occur (step S1: No), in step S3, the first EHC 11 is determined by the first EHC determining means (not shown). It is determined whether or not it is in a state to supply power. Here, as a state in which power should be supplied to the first EHC 11, in this embodiment, for example, the DOC constituting the exhaust gas purification element 12 included in the first exhaust gas purification device 10 including the first EHC 11 has a predetermined temperature. If the catalyst activation temperature has not been reached and it is necessary to quickly raise the temperature, or the difference between the front and rear of the DPF constituting the exhaust gas purification element 13 included in the first exhaust gas purification device 10 including the first EHC 11 There is a case where the pressure exceeds a specified value and the PM collection filter needs to be heated to a predetermined temperature and the PM regeneration process needs to be performed.

  Therefore, for example, when the temperature of the exhaust gas purification element 12 (DOC) detected by the temperature sensor or the like does not reach a predetermined temperature, or before and after the exhaust gas purification element 13 (DPF) detected by the pressure sensor or the like When the differential pressure exceeds the specified value and it is necessary to perform the PM regeneration process, it is determined that the first EHC 11 is to be supplied with power (step S3: Yes). In this case, in step S4, a control mechanism (not shown) activates the switch mechanism 60 to switch the power supply circuit from the power source 50 to the first circuit (ie, the circuit AB), and the first EHC 11 is sufficiently connected. A high voltage is applied.

  Conversely, for example, the temperature of the exhaust gas purification element 12 (DOC) detected by a temperature sensor or the like has reached a predetermined temperature, and before and after the exhaust gas purification element 13 (DPF) detected by a pressure sensor or the like. When the differential pressure remains below the specified value, it is determined that power is not to be supplied to the first EHC 11 (step S3: No). In this case, in step S5, it is determined by a second EHC determination means (not shown) whether or not power is to be supplied to the second EHC 21. Here, as a state where power should be supplied to the second EHC 21, in this embodiment, for example, the SCR constituting the exhaust gas purification element 22 included in the second exhaust gas purification device 20 including the second EHC 21 has a predetermined temperature. (Catalyst activation temperature) is not reached, and there is a case where it is necessary to quickly raise the temperature.

  Therefore, for example, when the temperature of the exhaust gas purification element 22 (SCR) detected by the temperature sensor or the like does not reach a predetermined temperature, it is determined that the power is to be supplied to the second EHC 21 (step). S5: Yes). In this case, in step S6, a control mechanism (not shown) activates the switch mechanism 60 to switch the power supply circuit from the power source 50 to the second circuit (ie, the circuit BC), and the second EHC 21 is sufficiently supplied. A high voltage is applied.

  Conversely, for example, when the temperature of the exhaust gas purification element 22 (SCR) detected by a temperature sensor or the like has reached a predetermined temperature, it is determined that power is not to be supplied to the second EHC 21 ( Step S5: No). In this case, since it is determined that it is not necessary to supply power to either the first EHC 11 or the second EHC 21, power is not supplied by any of the first circuit to the third circuit, and is shown in FIG. A series of processes executed according to the flowchart is terminated.

  As described above, the series of processes executed according to the flowchart shown in FIG. 4 represents the EHC control method according to one embodiment of the present invention. That is, according to the EHC control method according to one embodiment of the present invention represented by the flowchart shown in FIG. 4, when it is determined that the first EHC 11 or the second EHC 21 is in a state where condensation can occur, Electric power is supplied to each of the first EHC 11 and the second EHC 21 at a relatively low voltage by the three circuits (circuits AC). On the other hand, when it is determined that the first EHC 11 or the second EHC 21 is not in a state where condensation can occur, and it is determined that the first EHC 11 or the second EHC 21 is to be supplied with power, the first circuit (circuit A- B) or the second circuit (circuit B-C) supplies power to the first EHC 11 or the second EHC 21 at a relatively high voltage. As a result, the electric power supplied to the EHC is increased while avoiding the discharge in the EHC in a situation where the condensate caused by the water vapor contained in the exhaust gas is generated (can be generated), and the exhaust gas purification device can be quickly operated. The object of the present invention to warm up can be achieved.

  In the EHC control method according to the embodiment described above with reference to FIG. 4, when it is determined that the first EHC 11 or the second EHC 21 is not in a state where condensation can occur, the first EHC 11 or the second EHC 21. Electric power is supplied to only one of them. However, the above-described embodiment is merely an example, and the present invention is relatively less than both the first EHC 11 and the second EHC 21 when it is determined that the first EHC 11 or the second EHC 21 is not in a state where condensation can occur. It does not exclude supplying power at a high voltage. That is, as a power supply mode to the first EHC 11 and the second EHC 21 when it is determined that the first EHC 11 or the second EHC 21 is not in a state where condensation can occur, a relatively high voltage is applied to both the first EHC 11 and the second EHC 21. Embodiments including modes of supplying power are also included in the various embodiments of the present invention.

  While several embodiments having specific configurations and specific procedures have been described for purposes of describing the present invention, the scope of the present invention is limited to these exemplary embodiments. However, it goes without saying that appropriate modifications can be made within the scope of the matters described in the claims and the specification.

  DESCRIPTION OF SYMBOLS 10 ... 1st exhaust gas purification apparatus, 11 ... 1st EHC, 12 ... Exhaust gas purification element (DOC), 13 ... Exhaust gas purification element (DPF), 20 ... 2nd exhaust gas purification apparatus, 21 ... 2nd EHC, 22 ... Exhaust gas purification element (SCR), 23 ... Reducing agent addition valve, 30 ... Internal combustion engine, 31 ... Engine body, 32 ... Intake manifold, 33 ... Exhaust manifold, 34 ... Exhaust passage, 41 ... Intake flow, 42 ... Exhaust flow Flow, 50 ... power supply, and 60 ... switch mechanism.

Claims (6)

A first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC, which are disposed in an exhaust passage of the internal combustion engine;
A power source for supplying power to each of the first EHC and the second EHC;
A first circuit that supplies power from the power source only to the first EHC at a first voltage, a second circuit that supplies power from the power source only to the second EHC at a second voltage, and a first circuit from the power source to the first EHC and A switch mechanism that switches a second circuit that supplies power to the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.
Dew condensation determining means for determining whether or not dew condensation can occur in the first EHC or the second EHC;
First EHC determination means for determining whether or not power is to be supplied to the first EHC;
And a second EHC determination unit that determines whether or not power is to be supplied to the second EHC, and the switch mechanism is operated based on the determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit. A control device for switching a power supply circuit to any one of the first circuit, the second circuit, and the third circuit;
In an exhaust gas purification system comprising:
Determining whether or not the dew condensation determination means is in a state where dew condensation can occur in the first EHC or the second EHC;
A first EHC determination step of determining whether or not the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether the second EHC is in a state in which power should be supplied to the determination result in the second EHC determination step, and the determination results in the dew condensation determination step, the first EHC determination step, and the second EHC determination step. A switching step of switching the power supply circuit to any one of the first circuit, the second circuit, and the third circuit by operating the switch mechanism by the controller; If the determination result in step S3 is affirmative, the determination result in the third circuit is negative. If the determination result in step S1 is negative, and if the determination result in the first EHC determination step is positive, the determination of condensation is performed in the first circuit. The determination result in step is negative, and the determination result in the second EHC determination step is positive A circuit switching step for switching the power supply circuit to the second circuit, respectively,
An EHC control method comprising:   2. The EHC control method according to claim 1, wherein in the third circuit, the first EHC and the second EHC are connected in series. 3.   3. The EHC control method according to claim 1, wherein the first catalyst is a manipulator, and the second catalyst is an underfloor catalyst. 4. . A first exhaust gas purification device including a first EHC and a second exhaust gas purification device including a second EHC, which are disposed in an exhaust passage of the internal combustion engine;
A power source for supplying power to each of the first EHC and the second EHC;
A first circuit that supplies power from the power source only to the first EHC at a first voltage, a second circuit that supplies power from the power source only to the second EHC at a second voltage, and a first circuit from the power source to the first EHC and A switch mechanism that switches a second circuit that supplies power to the second EHC at a third voltage and a fourth voltage lower than the first voltage and the second voltage, respectively.
Dew condensation determining means for determining whether or not dew condensation can occur in the first EHC or the second EHC;
First EHC determination means for determining whether or not power is to be supplied to the first EHC;
And a second EHC determination unit that determines whether or not power is to be supplied to the second EHC, and the switch mechanism is operated based on the determination by the dew condensation determination unit, the first EHC determination unit, and the second EHC determination unit. A control device for switching a power supply circuit to any one of the first circuit, the second circuit, and the third circuit;
An exhaust gas purification system comprising:
Determining whether the condensation determination means is in a state where condensation can occur in the first EHC or the second EHC;
Determining whether the first EHC determination means is in a state of supplying power to the first EHC;
The second EHC determination means determines whether or not the second EHC should be supplied with power, and based on the determination results by the dew condensation determination means, the first EHC determination means, and the second EHC determination means, When the switch mechanism is operated by the control device to switch the power supply circuit to any one of the first circuit, the second circuit, and the third circuit, the determination result by the dew condensation determination means is affirmative When the determination result by the dew condensation determination means is negative in the third circuit and the determination result by the first EHC determination means is affirmative, the determination result by the dew condensation determination means is negative in the first circuit. And when the determination result by the second EHC determination means is affirmative, the power supply circuit is switched to the second circuit, respectively.
Exhaust gas purification system.   5. The exhaust gas purification system according to claim 4, wherein in the third circuit, the first EHC and the second EHC are connected in series.   6. The exhaust gas purification system according to claim 4, wherein the first catalyst is a manipulator, and the second catalyst is an underfloor catalyst. Purification system.

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