JP3106982B2 - Catalyst preheat control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preheat control device for a catalyst, which raises the temperature of a catalyst to a temperature at which its exhaust gas purifying performance can be sufficiently exhibited (active temperature) before starting an engine.

[0002]

2. Description of the Related Art Automobiles using an engine as a drive source purify exhaust gas discharged from the engine using a catalyst, but it is difficult to sufficiently purify exhaust gas in all running states.

[0003] Therefore, the development of electric vehicles has been promoted. Most electric vehicles drive the tires by driving the motor with the power of the battery mounted on the vehicle body.However, the ratio of power consumption to the power of the battery mounted on the vehicle body is large, The drawback is that the distance that can be achieved is short.

[0004] Therefore, as shown in Japanese Patent Application Laid-Open No. 7-71236, the vehicle normally runs only with the power of the battery,
When the power of the battery falls below a predetermined level, the engine operates according to the state of the battery, in which the engine with a small displacement is driven to drive the generator, and the vehicle runs while generating power while charging until the predetermined power level is reached.・ Hybrid electric vehicles that repeatedly stop and continue electric running have been developed.

[0005] Such a hybrid electric vehicle drives a generator with a constant (light) load only for a short charging time required for the engine to maintain the electric running, so that high purification performance can be achieved while compensating for the drawbacks of the battery. Has the advantage that it can be secured.

[0006]

Incidentally, such a hybrid vehicle is required to have a particularly high purification performance. For this purpose, it is desirable that the temperature of the catalyst be raised to the activation temperature at which the exhaust gas is sufficiently purified at the time of starting the engine.

Therefore, a catalyst provided with a heating means for raising the temperature of the catalyst as disclosed in Japanese Patent Application Laid-Open No. 5-22925, for example, an electric heating catalyst called an EHC (a component for electrically heating such as a heater is built-in. A technique of heating the catalyst in advance, called so-called preheating, has been proposed in which the temperature of the catalyst is raised by energizing the heater of the electrically heated catalyst before the cold start of the engine.

[0008] Specifically, Japanese Patent Application Laid-Open No. 5-22925 discloses a technique for improving exhaust gas purification performance at the time of cold start of an engine in a normal car, that is, a car in which the power of the engine is transmitted to tires as it is to run. Using the engine water temperature as a determination signal as to whether or not to preheat, before starting the engine in a cold state, the heater is energized to raise the temperature of the catalyst, and the temperature of the catalyst reaches a predetermined temperature with a catalyst temperature sensor. Then, the energization of the heater is terminated.

However, the hybrid electric vehicle differs from such an engine-driven vehicle in that the battery needs to be charged regardless of whether the engine is cold or hot before starting the engine. Requires that the temperature of the catalyst be raised to the activation temperature.

For this reason, the preheating of the catalyst may not be performed properly. That is, since a high temperature sensor suitable for detecting a high temperature corresponding to the activation temperature of the catalyst (about 600 ° C.) is used as the catalyst temperature sensor for detecting the catalyst temperature, temperature detection in a low temperature range is not accurate.

For this reason, when the temperature of the catalyst is low, for example, 10
Preheating is not required when the engine is required to be started when the engine is warm at ℃ and the engine is warmed up. Is output.

[0012] Therefore, the preheat control depending only on the catalyst temperature as described above cannot cope with a hybrid vehicle that requires strict exhaust gas purification performance, and instead, a high-precision preheat controllability is required. I have.

The present invention has been made in view of the above circumstances, and an object of the present invention is to always perform appropriate preheating control of a catalyst regardless of the temperature state of the catalyst and the temperature state of the engine. It is an object of the present invention to provide a catalyst preheating control device capable of performing the preheating.

[0014]

In order to achieve the above-mentioned object, the invention described in claim 1 is provided before starting the engine.
It has control means for operating a heating means for purifying exhaust gas to raise the temperature of the catalyst to a predetermined temperature. The control means detects a state temperature of the engine and controls heating required to raise the temperature of the catalyst to a target temperature. First setting means for determining the operation time of the means, second setting means for detecting the state temperature of the catalyst and determining the operation time of the heating means required to raise the temperature of the catalyst to the target temperature, and And a determining means for comparing the respective operating times obtained by the second setting means to determine a longer operating time as the actual operating time, and an operating means for operating the heating means in accordance with the determined actual operating time. Then, in both the high-temperature range and the low-temperature range, the preheat control is performed with the operation time obtained by using the parameter for which the detection accuracy can be expected.

That is, according to the first aspect of the present invention, when the engine is started, the operating time of the heating means until the catalyst reaches the target temperature depends on the system based on the state temperature of the catalyst, and the state temperature of the engine. 2 with the system based on
Required from one.

[0016] Then, from the comparison of both operating time, to determine the operating time of not long direction as the actual operating time.

Then, the operation of the heating means is controlled in accordance with the actual operation time, and preheating for raising the temperature of the catalyst to a predetermined temperature (active temperature) is performed. Thereby, the state temperature of the catalyst is high, that is, from the state temperature of the engine, in a region where a high temperature that cannot be detected at all is detected,
Preheating control is performed based on the operating time obtained from the temperature state of the catalyst where detection accuracy can be expected.

On the other hand, when the state temperature of the catalyst is low, that is, in the region where a low temperature that cannot be detected at all from the state temperature of the catalyst is detected, the operating time obtained from the engine temperature state where detection accuracy can be expected is obtained. Preheat control is performed. Specifically, when the temperature of the catalyst is low (for example, 1
0 ° C) and the engine is warm (for example, 3
If the start of the engine is required at 5 ° C.), the preheat control is performed based on the operation time obtained from the state temperature of the engine.

Thus, what kind of temperature condition of the catalyst,
Good preheat control is always performed regardless of the temperature state of the engine. Therefore, the strict exhaust gas purification performance required for a hybrid vehicle can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on a first embodiment shown in FIGS. FIG. 1 is a schematic configuration diagram of a hybrid electric vehicle (hybrid electric vehicle) to which the present invention is applied.
A traveling motor 3 disposed between the two is a transmission connected to an output section of the motor 1.

The output of the transmission 3 is connected to the front wheels 2, 2 via a differential (not shown), for example.
And the front wheels 2 and 2 can be driven using the traveling motor 1 as power.

A battery 4 is mounted at the center of a vehicle body (not shown). The output terminal of the battery 4 is connected to a wiring 5 extending from a connection terminal of the traveling motor 1.
5 so that the electric power of the battery 4 can be supplied to the traveling motor 1.

Between the rear wheels 6, 6, a water-cooled engine (an engine having a cooling structure in which cooling water circulates through a radiator and a jacket in the engine body), for example, a water-cooled electronically controlled engine 7 (hereinafter simply referred to as an engine) Engine 7). The output of the engine 7 includes a generator 8
Are connected so that power can be generated using the engine 7 as a drive source.

The output terminal of the generator 8 is connected to the extending ends of the wires 5, 5, so that the power generated by the generator 8 can be supplied to the battery 4 and the traveling motor 1 through the wires 5, 5. It is like that.

On the other hand, reference numeral 9 denotes M connected to the traveling motor 1.
A CU (Motor Control Unit), 10 is a BCU (Battery Control Unit) connected to the battery 4, 11 is an APU (Auxiliary Processor Unit) connected to the generator 8, and 12 is an ECU (Engine) connected to the engine 7. Control unit).

The MCU 9 has a function of controlling the operation of the traveling motor 1 according to the opening of an accelerator pedal (not shown). BCU 10 is battery 4
When the amount of power of the battery 4 is reduced to a power value equal to or less than a predetermined value, an engine start command signal corresponding to turning on an ignition switch is output.

The APU 11 has a function of controlling the start of the engine 7, a function of controlling the throttle of the engine 7, a function of controlling the power generation, and a heating type which is interposed in the exhaust pipe 7 a of the engine 7 together with the three-way catalyst 13 a. It has a function of controlling a catalyst, for example, a heater 13c (heating means) of an electrically heated catalyst (EHC) 13b. The three-way catalyst 13a and the electrically heated catalyst 13b are housed in the same container 13d to form one catalytic converter.

The ECU 12 has a function of controlling the operation of the engine 7. These MCU9, BCU10,
The APU 11 and the ECU 12 cooperate to obtain the following functions necessary for running a hybrid electric vehicle. (B) A function that allows the vehicle to run only with the electric power of the battery 4. (B) A function of outputting an engine start command signal from the BCU 10 to the APU 10 when the power of the battery 4 drops below a predetermined value. (C) In accordance with this engine drive command, the electrically heated catalyst 1
The function of preheating 3b to a predetermined temperature (activation temperature). (D) Function to start the engine 7 after preheating. (E) A function of operating the engine 7 in a rotation range suitable for exhaust gas purification. (F) A function of appropriately controlling the power generation from the generator 8 and running while generating power. (G) When the battery 4 is charged to a predetermined amount of power,
Function to stop the engine 7.

The function (c) described above is stored in the APU 11 and constitutes a catalyst preheating control device which is an essential part of the present invention. Describing this preheat control device, the APU 11 has an engine cooling water temperature (hereinafter, referred to as a sensor for detecting the temperature of the cooling water, which detects the state temperature of the engine) provided in the engine 7 (hereinafter, referred to as a cooling water temperature sensor 14). The engine water temperature is input to the APU 11 through the ECU 12. That is,
The engine water temperature, which most notably indicates the state temperature of the engine, is input to the APU 11.

The APU 11 is connected to a catalyst temperature sensor 15 (for example, a high temperature sensor) provided in the container 13d of the catalytic converter, and the temperature of the catalyst detected by the catalyst temperature sensor 15 is input to the APU 11. It is to be done.

Further, the APU 11 is provided with a heater 13c having the output (catalyst temperature) of the catalyst temperature sensor 15 as a parameter so that proper catalyst preheating can be performed at various catalyst state temperatures and engine state temperatures. The energization time (operation time) and the energization time (operation time) of the heater 13c (electric heating catalyst 13b) obtained by using the output of the water temperature sensor 14 (engine water temperature) as a parameter are set in a map format.

Specifically, the APU 11 has an electric heating catalyst 13 based on the catalyst temperature as shown by a solid line A in FIG.
The electric heating catalyst 13b reaches the target activation temperature based on the energization time required for b to reach the target activation temperature (catalyst temperature / EHC energization time map) and the engine water temperature as indicated by the broken line B. (Engine water temperature / EHC energization time map) is set (corresponding to the first setting means and the second setting means).

More specifically, the map indicated by the solid line A shows that a high-precision result can be obtained in a high temperature range, for example, in the range of 30 to 500 ° C. (temperature brought by the catalyst) due to the characteristics of the high temperature sensor constituting the catalyst temperature sensor 15. However, an accurate result cannot be obtained in the temperature range (low temperature range) on the engine water temperature side lower than that.

On the other hand, the map indicated by the broken line B indicates that the water temperature sensor 1
Due to the characteristics of No. 4, high accuracy can be obtained up to a low temperature range, for example, a range of -56 to 156 ° C. (temperature brought by the engine), but a temperature range higher than the catalyst activation temperature side (high temperature range)
Will result in a diagram that will not give accurate results.

By the combination of the two maps A and B, an energization map of the electric heating catalyst 13b is obtained which covers the entire range of "state temperature of gasoline engine 7 to state temperature of electric heating catalyst 13b". .

The APU 11 has a function of reading the energizing time of the heater 13c from the maps A and B according to the detected engine water temperature and catalyst temperature.

Further, the APU 11 is provided with a function of comparing the energization time obtained from the engine water temperature and the energization time obtained from the catalyst temperature, and selecting and determining the longer one as the actual operation time. When an unobtainable high-temperature temperature is detected, the energization time that depends on the catalyst temperature is determined as the actual energization time (actual operation time), and a low-temperature temperature that is difficult to detect is detected from the state temperature of the catalyst. At this time (depending on the characteristics of the catalyst temperature sensor 15), the energization time dependent on the engine water temperature (engine state temperature) is determined as the actual energization time (actual operation time) (determination means).

In addition, the APU 11 is provided with a function of energizing the heater 13c of the electric heating catalyst 13b for the determined actual energizing time. When an engine start command is received, the electric heating catalyst 13b is activated before the engine starts. Is raised to the activation temperature (operating means).

The APU 11 has a function of forcibly stopping the energization of the heater 13c when the catalyst temperature rises to a judgment temperature for judging abnormality (prevention of abnormal heating of the catalyst).

The preheating control of the electric heating catalyst 13b is shown in the flowchart of FIG. Next, the preheat control will be described with reference to running of the hybrid electric vehicle.

That is, it is assumed that the remaining capacity of the battery 4 is 100% (fully charged state). In this state,
When the occupant operates the accelerator pedal, under the control of the MCU 9, electric power corresponding to the accelerator pedal opening is supplied from the battery 4 to the traveling motor 1, and the hybrid vehicle runs with electric power of only the battery 4.

The remaining capacity of the battery 4 gradually decreases as shown in FIG. 4 with such electric running (EV running). Thereafter, the battery 4 has a predetermined capacity value X.
When it is lowered, the BCU 10 outputs an engine start command signal (corresponding to ignition ON) to the APU 11.

When this signal is received, the APU 11 enters a preheating control of the electrically heated catalyst 13b (EHC) in order to set the catalyst temperature to a temperature suitable for exhaust gas purification. Then
The APU 11 generates the map A as shown in step S1.
From the (catalyst temperature / EHC energization time map), the energization time Tcc for the catalyst temperature detected by the current catalyst temperature sensor 15 is read. Subsequently, as shown in step S2, the energization time Twt for the current engine water temperature is read from the map B (engine water temperature / EHC energization time map).

As a result, the energizing time Tcc obtained from the catalyst temperature and the energizing time Twt obtained from the state temperature of the engine are obtained.
Are read. Specifically, for example, if the detection temperature of the catalyst temperature sensor 15 is 10 ° C. and the detection signal from the water temperature sensor 14 is a cold engine state such as 10 ° C., the engine water temperature is changed from T 1 in FIG. Only the determined energizing time Twt1 is read. Further, for example, if the detection temperature of the catalyst temperature sensor 15 is 250 ° C. and the detection signal from the water temperature sensor 14 is a warm engine state such as 35 ° C., the energization time Tcc1 calculated from the catalyst temperature such as T2, The energizing time Twt2 obtained from the engine water temperature such as T3 is read. Further, for example, when the detection temperature of the catalyst temperature sensor 15 is 400 ° C. and the water temperature sensor 14
If the detection signal is a warm engine state such as 160 ° C., only the energizing time Tcc2 obtained from the catalyst temperature is read.

Then, the process proceeds from step S3 to step S4 or step S5, and the APU 11 selects one of the two energizing times Tcc and Twt, specifically, the longer energizing time as the actual energizing time T. I do.

When the selection of the energization time includes detection of a temperature in a high temperature range that cannot be reached by the engine coolant temperature, the energization time based on the catalyst temperature is determined as the actual energization time T, and the catalyst temperature sensor When the temperature in the low-temperature range, which is difficult to detect in 14, is included, the energization time based on the engine coolant temperature is determined as the actual energization time T.

Specifically, when the detected temperature of the catalyst temperature sensor 15 is 10 ° C. and the detection signal from the water temperature sensor 14 is 10 ° C., the energizing time Twt1 becomes the actual operating time T, and 15 detected temperature is 250 ℃
When the detection signal from the water temperature sensor 14 is 35 ° C., the energizing time Twt 2 is the actual operating time T, the detected temperature of the catalyst temperature sensor 15 is 400 ° C., and the water temperature sensor 1
4 is 160 ° C., the energizing time Tcc
2 is the actual operation time T.

Then, the process proceeds to step S6, where the APU 11
Turns on the heater 13c of the electric catalyst 13b. Thereby, the electric catalyst 13b and the three-way catalyst 13b are heated.

During this heating, the APU 11 proceeds to step S7
As described above, the operation time T determined in step S8 becomes 0 while monitoring whether or not the temperature has risen to the catalyst abnormality determination temperature Tc forming an abnormality determination value with the catalyst temperature Ts from the catalyst temperature sensor 15. Counting up.

If the catalyst temperature Ts reaches the catalyst abnormality determination temperature Tc at this time, it is regarded as abnormal and the process proceeds to step S10, where the electric heating catalyst 13b
Of the heater 13c is stopped to prevent the temperature of the catalyst from rising abnormally.

When the operation time T becomes 0, the APU 11
It is determined that the temperature of the electric heating catalyst 13b has been raised to the predetermined activation temperature, and the process proceeds to step S10, in which the power supply to the heater 13c is stopped.

With the end of the preheating of the catalyst, the gasoline engine 7 is started through a starter (not shown), and the electric power generated by the generator 8 is supplied to both the battery 4 and the traveling motor 1.

When the battery 4 recovers (charges) to the predetermined capacity value Y, the BCU 10 outputs an engine stop signal corresponding to ignition off to the APU 11,
The engine 7 is stopped, and the hybrid vehicle is run again using only the power of the battery 4.

The heater 13 obtained from the catalyst temperature as described above
heater 13 calculated from the set energizing time of c and the engine water temperature
According to the control for selecting any one of the set energization times a, the preheat control is performed in the high catalyst temperature region and the low engine water temperature region with the energization time obtained from the parameter for which the detection accuracy can be expected.

Therefore, what temperature condition of the catalyst,
Good preheat control can always be performed regardless of the temperature state of the engine. In particular, it is effective in realizing the strict exhaust gas purification performance required by hybrid vehicles.

In the above-described embodiment, an example in which the present invention is applied to preheating of a catalyst of a hybrid electric vehicle has been described. Needless to say, a tire is powered by the engine 7 as in the second embodiment shown in FIG. It goes without saying that the present invention may be applied to a car that is driven to run. In this case, various functions set in the APU 11 are set in the ECU 12.

However, in FIG. 5, the same portions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In addition,
In both the first embodiment and the second embodiment, an example of preheating using an electric heating catalyst has been described. However, the present invention is not limited to this, and a structure in which fuel is burned by a burner to heat (heat) the catalyst is used. However, the structure for raising the temperature of the catalyst is not limited.

[0058]

As described above, according to the present invention, the longer the set operation time of the heating means determined from the catalyst temperature and the set operation time of the heating means determined from the engine state temperature, whichever is longer.
By controlling the operating time as the actual operating time ,
In any of the low-temperature regions, the preheat control can be performed with the operation time obtained by using the parameter for which the detection accuracy can be expected.

As a result, appropriate preheat control of the catalyst can always be performed regardless of the temperature state of the catalyst and the temperature state of the engine. In particular, this preheat control is effective for realizing the strict exhaust gas purification performance required by hybrid vehicles.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a catalyst preheating control device according to a first embodiment of the present invention, together with a hybrid electric vehicle to which it is applied.

FIG. 2 is a map showing the energization time of an electrically heated catalyst obtained from each catalyst temperature and engine water temperature set in the preheat control device.

FIG. 3 is a flowchart for explaining control until preheating is performed using the map.

FIG. 4 is a diagram showing a change in battery when the hybrid electric vehicle is running.

FIG. 5 is a diagram for explaining a main part of a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Running motor 4 ... Battery 7 ... Gasoline engine (engine) 11 ... APU (Control means, 1st setting means, 2nd setting means, determination means, operation means) 13b ... Electric heating catalyst (catalyst) 13c ... Heater (heating means) 14 ... Water temperature sensor (means for detecting the state temperature of the engine) 15 ... Catalyst temperature sensor (means for detecting the state temperature of the catalyst).

Continuation of front page (56) References JP-A-4-274926 (JP, A) JP-A-8-296431 (JP, A) JP-A-6-129243 (JP, A) JP-A-5-321645 (JP) , A) JP-A-6-81636 (JP, A) JP-A-7-145724 (JP, A) Patent 2874449 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3 / 08-3/38 F01N 9/00-11/00

Claims (1)

(57) [Claims] 1. A catalyst for purifying exhaust gas discharged from an engine, a heating means for heating the catalyst, and a control means for operating the heating means to raise the temperature of the catalyst to a predetermined temperature before starting the engine. Wherein the control means detects a state temperature of the engine when starting the engine, and determines an operation time of the heating means required to raise the temperature of the catalyst to a target temperature. A second setting means for detecting a state temperature of the catalyst when the engine is started and calculating an operation time of the heating means necessary to raise the temperature of the catalyst to a target temperature; and determining means for determining the operating time of longer compares each operating time obtained by said first and second setting means in actual operating time, actuates the heating means in accordance with the actual operating time determined Preheating control device of a catalyst characterized by being provided with actuating means.