JP7081213B2 - Heater control device - Google Patents

Description

The present invention relates to a heater control device that controls energization of a heater for a fuel filter.

For example, in a common rail fuel supply system for a diesel engine, light oil is used as fuel. It is conceivable that when the temperature of the fuel becomes low, wax precipitates, and the wax adheres to the fuel filter to cause clogging. Then, there is a concern that the clogging causes a shortage of fuel supply, which causes a decrease in engine output. In order to suppress such clogging of the fuel filter, a technique has been proposed in which a heater for heating the fuel is provided to melt the precipitated wax (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-51920

Here, if the fuel is heated to a temperature at which the wax is completely melted, the clogging of the fuel wax can be cleared. However, by repeating such heating, the power consumption increases. It is feared that this may cause, for example, a decrease in fuel efficiency.

The present invention has been made in view of the above problems, and a main object thereof is to provide a heater control device capable of appropriately removing precipitates while reducing power consumption.

Hereinafter, means for solving the above problems will be described.

The present invention is applied to a fuel supply system including a fuel filter arranged in a fuel path from a fuel tank to a fuel pump to filter fuel, and a heater for heating the fuel supplied to the fuel filter by energization. A heater control device that controls energization of the heater, a condition determination unit for determining the success or failure of the heating start condition of the heater in a state where fuel precipitates adhere to the fuel filter, and the heating start condition are satisfied. When it is determined, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater and the heating of the heater removes more of the precipitate than the first heating control. It is provided with a heating control unit that selectively executes any of the second heating controls.

When it is determined that the heating start condition of the heater is satisfied with the fuel precipitate (wax) adhering to the fuel filter, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater. , The second heating control, which removes more precipitates than the first heating control by heating the heater, is selectively executed. In this case, according to the first heating control, it is possible to remove the precipitate while giving priority to suppressing the power consumption associated with the energization of the heater. Further, according to the second heating control, it is possible to give priority to wax removal and remove more precipitates. Therefore, by appropriately selecting two heating controls, it is possible to appropriately remove precipitates while reducing power consumption, unlike the case where, for example, one heating control is executed.

The figure which shows the structure of the common rail type fuel supply system in 1st Embodiment. The figure which shows the structure to affect the heater energization control. A flowchart showing a control parameter setting process. The figure which shows the relationship between a cloud point and kinematic viscosity. The flowchart which shows the heater energization control processing. A timing chart showing the flow of heater energization control. The figure which shows the structure which concerns on the heater energization control in 2nd Embodiment. The flowchart which shows the heater energization control processing in 2nd Embodiment. The figure which shows the change of the filter differential pressure at the time of heating. The figure which shows the relationship between the change amount of a filter differential pressure, and a counter threshold value. The flowchart which shows the heater energization control processing in 3rd Embodiment. The flowchart which shows the heater energization control processing in 4th Embodiment. The flowchart which shows the heater energization control processing in 5th Embodiment. The figure which shows the relationship between the fuel temperature and the filter differential pressure for each execution time of the 1st heating control in the 6th Embodiment.

Hereinafter, embodiments in which the fuel filter heater control device of the present invention is embodied will be described with reference to the drawings.

<First Embodiment>
The first embodiment is embodied as a fuel supply system for a diesel engine for a vehicle. First, an outline of the fuel supply system will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the fuel tank 10 and the fuel pump 11 are connected to each other through a fuel pipe 12 as a fuel path. The fuel pump 11 is a mechanical pump that is driven by the rotation of an engine (not shown) to repeatedly inhale and discharge fuel. A filter unit 13 is provided in the middle of the fuel pipe 12. An electromagnetically driven suction metering valve (SCV) 14 is provided in the fuel suction section of the fuel pump 11, and the low-pressure fuel pumped from the fuel tank 10 is fueled by the fuel pump 11 via the suction metering valve 14. Inhaled into the pressurizing chamber. Then, in the fuel pump 11, the fuel in the fuel pressurizing chamber is increased in pressure by the reciprocating movement of the plunger in synchronization with the engine rotation, and the high pressure fuel is discharged.

The suction metering valve 14 is configured as a normally open valve that is held in an open state (fully open state) when the electromagnetic solenoid is not energized, and the fuel suction passage is closed by energizing the electromagnetic solenoid. In this case, the fuel discharge amount by the fuel pump 11 is adjusted according to the energization timing of the electromagnetic solenoid. It is also possible to use a solenoid valve that is a normally closed valve as the suction metering valve 14.

A common rail 20 is connected to the fuel pump 11 via a fuel discharge pipe 18. The high-pressure fuel discharged from the fuel pump 11 is sequentially fed to the common rail 20 through the fuel discharge pipe 18, whereby the fuel in the common rail 20 is maintained in a high-pressure state. The common rail 20 is provided with a fuel pressure sensor 21 for detecting the fuel pressure in the common rail 20. In FIG. 1, the fuel pressure sensor 21 is provided on the common rail 20, but the fuel pressure sensor 21 may be provided on the path from the common rail 20 to the injection port of the injector 23.

An electromagnetically driven injector 23 provided in each cylinder of an engine (not shown) is connected to the common rail 20. High-pressure fuel is supplied to the injector 23 from the common rail 20 through the high-pressure fuel pipe 24, and fuel is injected and supplied to each cylinder of the engine by driving the injector 23. A part of the high-pressure fuel supplied to the injector 23 is returned to the fuel tank 10 through the return pipe 25. As the injector 23, a piezo-driven injector can be used instead of the electromagnetically driven injector.

The common rail 20 is provided with a normally closed pressure limiter 30 as a pressure release valve. The pressure limiter 30 has a mechanical check valve (check valve) structure, and opens when the fuel pressure in the common rail 20 excessively rises and exceeds the valve opening pressure of the pressure limiter 30. When the pressure limiter 30 opens, the high-pressure fuel is returned to the fuel tank 10 through the return pipe 25, and the fuel pressure is reduced. As a result, damage to high-pressure parts such as high-pressure piping and common rail 20 is suppressed.

The ECU 50 is an electronic control device including a well-known microcomputer including a CPU, ROM, RAM, flash memory, and the like. The ECU 50 takes in signals from various sensors such as a fuel pressure sensor 21, a rotation speed sensor 51 for detecting the engine rotation speed, an accelerator sensor 52 for detecting the accelerator operation amount, and a water temperature sensor 53 for detecting the temperature of the engine cooling water, and ROMs. By executing the control program or the like stored in the engine, the operating state of the engine is controlled. In the present embodiment, the ECU 50 corresponds to the condition determination unit, the heating control unit, and the kinematic viscosity acquisition unit.

Light oil fuel is used as the fuel for the engine shown in this embodiment. For light oil fuel, wax (precipitate) is deposited when the fuel temperature becomes a cloud point (so-called CP point) or lower. If the filter unit 13 is clogged with this wax, there is a concern that the fuel supply will be hindered and the engine operation will become unstable. In consideration of such circumstances, the fuel supply system in the present embodiment incorporates a heating device for heating the fuel.

Specifically, as shown in FIG. 2, the filter unit 13 has a fuel filter (filter element) 41 for filtering fuel, and is on the upstream side of the fuel filter 41 (that is, on the fuel tank 10 side) in the fuel supply path. ) And an electric heater 42 (specifically, a PTC heater) capable of heating fuel is arranged in the vicinity of the fuel filter 41. The heater 42 is connected to the ECU 50, and the ECU 50 executes energization control of the heater 42. When the heater 42 is energized and the fuel is heated, the above-mentioned wax precipitation is suppressed or the precipitated wax is melted. The heater 42 is arranged in the vicinity of the fuel filter 41 in order to shorten the time required for the heated fuel to reach the fuel filter 41, improve the responsiveness, and suppress the temperature decrease. .. The heater 42 is not limited to the PTC heater as long as it has a configuration in which the fuel can be heated by energization. For example, a temperature riser using a pressure wave may be used.

A fuel temperature sensor 43 for detecting the fuel temperature is arranged on the downstream side (that is, the fuel pump 11 side) of the fuel filter 41 in the fuel supply path. The fuel temperature sensor 43 is connected to the ECU 50, and the ECU 50 acquires the fuel temperature from the fuel temperature sensor 43.

Further, the filter unit 13 includes a kinematic viscosity sensor 44 that detects the kinematic viscosity of the fuel. The kinematic viscosity sensor 44 is provided on the downstream side of the fuel filter 41 in the fuel supply path, and is connected to the ECU 50. The ECU 50 acquires the kinematic viscosity of the fuel from the kinematic viscosity sensor 44, and sets various control parameters for energization control of the heater 42 based on the acquired kinematic viscosity. Then, the energization of the heater 42 is controlled based on the various control parameters.

In the present embodiment, when the fuel temperature is lower than the reference temperature T0, which is the heating start temperature, it is assumed that the heating start condition of the heater 42 is satisfied, and the fuel heating by the heater 42 is started and the fuel is heated. After the start of the above, the heating of the fuel by the heater 42 is terminated based on the fact that the fuel temperature rises to the target temperatures T1 and T2, which are the heating end temperatures. As a result, heating of the heater 42 is intermittently executed. In this case, in particular, two target temperatures T1 and T2 having different temperature levels are set as the heating end temperature, and by heating until the first target temperature T1 is reached after the start of heating, the degree of heating is relative. A small first heating control is performed. As a result, a part of the wax is melted, and the filter differential pressure, which is the differential pressure between the upstream side and the downstream side of the fuel filter 41, is reduced. Further, by heating until the second target temperature T2 is reached after the start of heating, the second heating control having a relatively large degree of heating is executed. As a result, the wax deposited on the fuel filter 41 is completely melted.

Here, the first heating control is a heater energization control that removes a part of the wax in the fuel filter 41 by heating the heater 42, and according to this first heating control, priority is given to suppressing the power consumption associated with the heater energization. While doing so, the wax can be removed. Further, the second heating control is a heater energization control that removes more wax than the first heating control by heating the heater 42, and according to this second heating control, priority is given to wax removal and more wax is used. Can be removed.

In the present embodiment, the heating corresponding to the first target temperature T1 is mainly executed, and the heating corresponding to the second target temperature T2 is executed only when a predetermined condition is satisfied. Specifically, when the number of times the heating corresponding to the first target temperature T1 is repeatedly executed reaches the threshold value N, the heating is switched to the heating corresponding to the second target temperature T2.

Hereinafter, the control parameter setting process in the heater energization control will be described with reference to FIG. This process is executed by the EUC 50 at a predetermined cycle while the ignition switch is on. Here, the reference temperature T0, the target temperature T1, T2, and the threshold value N are set as the control parameters, and the execution mode of the heater energization control including the first heating control and the second heating control is set by the parameter settings. It will be set. It should be noted that this process may be executed only when the engine is started, for example.

In the control parameter setting process, first, in step S101, it is determined whether or not the kinematic viscosity can be acquired from the kinematic viscosity sensor 44. At this time, for example, if the kinematic viscosity sensor 44 is normal, the kinematic viscosity can be acquired, and if the kinematic viscosity sensor 44 is abnormal, the kinematic viscosity cannot be acquired.

If the kinematic viscosity can be obtained, the process proceeds to step S102. In step S102, the kinematic viscosity is acquired from the kinematic viscosity sensor 44. The correspondence between the kinematic viscosity of the fuel and the melting point CP of the fuel and the melting point MP of the wax is stored in advance in the ROM of the EUC50. The cloud point CP and melting point MP of the fuel are estimated based on the obtained kinematic viscosity. The cloud point CP of the fuel increases as the kinematic viscosity of the fuel increases (see FIG. 4), and the melting point MP also increases as the kinematic viscosity of the fuel increases.

In the following step S104, the reference temperature T0 is set based on the cloud point CP estimated in step S103, and the target temperatures T1 and T2 are set based on the cloud point CP and the melting point MP. The ROM of the EUC50 stores the correspondence between the cloud point CP and the melting point MP, the reference temperature T0 (heating start temperature), and the target temperatures T1 and T2 (heating end temperature), and based on the correspondence, the correspondence is stored. The reference temperature T0 and the target temperatures T1 and T2 are set. Specifically, the reference temperature T0 is set as a temperature lower than the cloud point CP. Further, the first target temperature T1 is set as a temperature higher than the cloud point CP and lower than the melting point MP, and the second target temperature T2 is set as a temperature higher than the melting point MP.

Further, in step S104, the threshold value N is set based on the cloud point CP. Generally, a fuel having a higher kinematic viscosity contains a large amount of high molecular weight hydrocarbons, so that clogging progresses faster after a heating / cooling cycle. Therefore, the threshold value N is defined to become smaller as the cloud point CP becomes higher, that is, as the kinematic viscosity becomes higher (see N1 to N3 in FIG. 4).

In steps S103 and S104, the cloud point CP and the melting point MP are estimated based on the kinematic viscosity of the fuel, and each control parameter (reference temperature T0, target temperature T1,) is estimated based on the cloud point CP and the melting point MP. T2, threshold value N) is set. From this, each control parameter is set based on the kinematic viscosity of the fuel.

If it is determined in step S101 that the kinematic viscosity cannot be obtained, the process proceeds to step S105. In step S105, the cloud point CP and the melting point MP are estimated using the maximum value of the kinematic viscosity (maximum value in FIG. 4) in the preset range of the kinematic viscosity. In the following step S106, the reference temperature T0, the target temperatures T1 and T2, and the threshold value N are set based on the estimated value in step S105. That is, when the kinematic viscosity cannot be obtained, the reference temperature T0 and the target temperatures T1 and T2 become the maximum in each assumed range.

Next, the heater energization control process executed based on the above various parameters will be described with reference to FIG. This process is executed by the EUC 50 at a predetermined cycle while the ignition switch is on.

In the heater energization control process, first, the fuel temperature detected by the fuel temperature sensor 43 in step S201 is acquired. In the following step S202, it is determined whether or not the heater 42 is turned off. If the heater 42 is turned off, an affirmative determination is made in step S202, and the process proceeds to step S203.

In step S203, it is determined whether or not the fuel temperature is lower than the reference temperature T0. If the temperature is less than the reference temperature T0, the process proceeds to step S204. In step S204, it is determined whether or not the value of the operation counter is less than the threshold value N. The operation counter is a counter that counts the number of times that the first heating control is repeatedly executed, and the count value is stored and held in the backup memory (for example, EEPROM) even after the ignition switch is turned off.

If the value of the operation counter is less than the threshold value N, an affirmative determination is made in step S204, and the process proceeds to step S205. In step S205, a relatively low first target temperature T1 is set as the target temperature. After that, the value of the operation counter is incremented by 1 in step S206, the heater 42 is turned on in step S207, and then this control process is terminated.

When the value of the operation counter reaches the threshold value N, the process proceeds to step S208 and a relatively high second target temperature T2 is set as the target temperature. After that, in step S209, the operation counter is cleared to 0, the heater 42 is turned on in step S207, and then this control process is terminated.

Returning to the description of step S202, if a negative determination is made in step S202, that is, if the heater 42 is ON, the process proceeds to step S210. In step S210, it is determined whether or not the current fuel temperature has reached the target temperature set at the start of the current heating based on the fuel temperature acquired from the fuel temperature sensor 43. If a negative determination is made in step S210, this control process is terminated as it is. If an affirmative determination is made in step S210, the process proceeds to step S211 to turn off the heater 42, and then the control process is terminated.

Next, with reference to FIG. 6, the change in the amount of wax in the fuel filter 41 due to the heater energization control will be described. FIG. 6 shows the heater energization control after the ignition switch is turned on (that is, after the engine is started).

In FIG. 6, after the ignition switch is turned on, the heater 42 is turned on and the fuel heating is started based on the fact that the fuel temperature is lower than the reference temperature T0. As a result, the wax adhering to the fuel filter 41 is melted, and the clogging in the fuel filter 41 is alleviated. In this case, the filter differential pressure decreases as the heater is energized, and the fuel supply shortage is suppressed. As the heater energization is executed, the operation counter is incremented by 1. The value of the operation counter is retained even after the ignition switch is turned off, and if the counter value at the end of the previous running of the vehicle is a value other than zero, it is incremented with respect to the value other than zero. Is done.

In the heating corresponding to the first heating control, the heater 42 is turned off when the fuel temperature reaches the first target temperature T1 after the start of heating. After the heater 42 is turned off, the wax is captured by the fuel filter 41 as the low-temperature fuel is supplied from the fuel tank 10, so that the amount of wax deposited on the fuel filter 41 starts to increase. As described above, a part of the high-pressure fuel supplied to the injector 23 is returned to the fuel tank 10 through the return pipe 25, so that the fuel temperature in the fuel tank 10 gradually rises.

After that, when the fuel temperature drops to the reference temperature T0, the heater 42 is turned on again, and the heater is heated again based on the first target temperature T1. Each time the heater heating is executed, the operation counter is incremented by 1. In a situation where the first heating control is repeatedly executed, the amount of residual wax will gradually increase. That is, when heating → cooling is repeated, clogging gradually progresses even if the temperature is heated to the same temperature.

Then, when the value of the operation counter reaches the threshold value N, heating is executed with the heating target temperature set to the second target temperature T2. The second target temperature T2 is a temperature determined aiming at complete melting of the wax, and by heating to the second target temperature T2, all the wax deposited on the fuel filter 41 is melted. As a result, the gradually progressing clogging is cleared at once.

In the first heating control corresponding to the first target temperature T1, the energization time of the heater 42 is shorter than that in the second heating control for the purpose of complete melting of the wax. That is, the power consumption is small. In this way, it is possible to reduce the power consumption required to realize the stabilization of the fuel supply by mainly executing the first heating control having a small power consumption and reducing the execution opportunity of the second heating control. This is advantageous in achieving low fuel consumption of the vehicle as compared with, for example, a configuration in which complete melting is performed by the second heating control each time.

In the first heating control, it is allowed that a part of the wax remains without being completely melted. Therefore, the clogging progresses by repeating the first heating control. Therefore, when clogging progresses to some extent by repeating the first heating control (that is, when the number of executions of the first heating control reaches a predetermined number of times), the wax is completely melted by the second heating control. It prevents the fuel supply from being hindered, that is, the stability of the fuel supply is impaired by reducing the power consumption.

The cloud point and melting point of the fuel differ depending on the kinematic viscosity. Therefore, as shown in the present embodiment, the kinematic viscosity of the fuel is acquired by using the kinematic viscosity sensor 44, and various parameters for heating control (first target temperature T1, second target temperature, threshold N) are obtained based on the results. ) Can be set to make the heating control appropriate.

Hereinafter, another embodiment will be described focusing on the differences from the first embodiment.

<Second Embodiment>
The present embodiment is different from the first embodiment in that the execution condition of the second heating control is changed in consideration of the filter differential pressure (the front-rear differential pressure of the fuel filter 41). There is. Hereinafter, the configuration related to the heating control in the present embodiment will be described with a focus on the differences from the first embodiment.

As shown in FIG. 7, the filter unit 13 is provided with a differential pressure sensor 45 for detecting the differential pressure of the filter. The differential pressure sensor 45 is connected to the ECU 50, and information from the differential pressure sensor 45 is input to the ECU 50. The ECU 50 monitors the change in the filter differential pressure when the wax remaining in the fuel filter 41 is completely melted by the second heating control, and the threshold value N of the operation counter is set according to the change in the filter differential pressure. Perform the process to change. This process constitutes a part of the heater energization control process. Hereinafter, the heater energization control process will be described with reference to FIG.

In the heater energization control process, the fuel temperature is first acquired in step S301, and in the subsequent step S302, it is determined whether or not the heater 42 is turned off. If an affirmative determination is made in step S302, the process proceeds to step S303 to acquire the filter differential pressure Pa at the start of heating detected by the differential pressure sensor 45. After that, various processes for heating the fuel according to the fuel temperature are executed in steps S304 to S310, but each of these processes will be described because they are the same as the processes of steps S203 to S209 in the first embodiment. Is omitted.

Returning to the description of step S302, if a negative determination is made in step S302, that is, if the heater 42 is OFF, the process proceeds to step S311. In step S311, it is determined whether or not the fuel temperature has reached the target temperature. If a negative determination is made in step S311, this control process is terminated as it is. If an affirmative determination is made in step S311, the process proceeds to step S312 and the heater 42 is turned off.

After the heating is completed in step S312, it is determined in step S313 whether or not the current heating target temperature is the second target temperature T2. If a negative determination is made in step S313, this control process is terminated as it is. If an affirmative determination is made in step S313, the process proceeds to step S314. In step S314, the filter differential pressure Pb at the end of heating detected by the differential pressure sensor 45 is acquired. In the following step S315, the amount of change in the filter differential pressure (Pa—Pb) before and after heating is calculated, and it is determined whether or not this amount of change is smaller than the preset reference change amount ΔP. The reference change amount ΔP may be set based on the filter differential pressure Pa at the start of heating. For example, when the filter differential pressure Pa at the start of heating is large, the reference change amount ΔP may be larger than when it is small.

When the wax is completely melted by the second heating control, it is theoretically assumed that the filter differential pressure returns to the value (initial value) before the occurrence of clogging due to the wax (see Pb1 in FIG. 9). However, when the fuel filter 41 is clogged not only with the wax but also with foreign matter mixed in the fuel, the foreign matter remains even if the wax is completely melted, so that the filter differential pressure becomes clogged. It may not return to a value that does not exist (see Pb2 in FIG. 9).

When foreign matter is one of the causes of clogging in this way, the time until the fuel supply amount reaches the limit value is shortened due to the progress of the clogging of the wax. Therefore, if the amount of change in the filter differential pressure before and after heating is less than the reference change amount ΔP, that is, if the recovery of the filter differential pressure is insufficient, an affirmative determination is made in step S315 and the process proceeds to step S316. , The execution condition of the second heating control is relaxed. Specifically, the threshold value N of the operation counter is lowered in order to increase the execution frequency of the second heating control. As a result, in the subsequent heater energization control process, the second heating control is executed in a shorter span than before. In this way, by increasing the chances of executing the second heating control in consideration of the presence or absence of clogging due to the inclusion of foreign matter, it is possible to suitably achieve both the power consumption reduction function and the engine operation stabilization function.

When the change amount (Pa—Pb) of the filter differential pressure before and after heating is smaller than the reference change amount ΔP, the threshold value N of the operation counter may be changed in the embodiment shown in FIG. In this case, the smaller the amount of change in the filter differential pressure (Pa—Pb), the smaller the threshold value N.

When lowering the threshold value N of the operation counter, N = 0 may be set. When N = 0, only the second heating control of the first heating control and the second heating control is executed. The threshold value of the operation counter may be returned to the value before the change when the clogging of the foreign matter is cleared and the differential pressure is sufficiently recovered.

When the change amount (Pa-Pb) of the filter differential pressure before and after heating is smaller than the reference change amount ΔP, it is considered that the fuel filter 41 is clogged with foreign matter. The heater energization control may be executed so that the fuel supply is not hindered even if the clogging occurs. From this point of view, as a setting of the execution mode of the heater energization control when the change amount (Pa-Pb) of the filter differential pressure before and after heating is smaller than the reference change amount ΔP, the threshold value N of the operation counter is changed. You may execute the process of. For example, in addition to or in place of the process of changing the threshold value N of the operation counter, a process of raising the first target temperature T1 in the first heating control may be executed.

In steps S315 and S316 above, the execution condition of the second heating control is relaxed based on the amount of change in the filter differential pressure (Pa-Pb) before and after heating. The configuration may be such that the execution condition of the second heating control is relaxed based on the filter differential pressure Pb. In this case, the execution condition of the second heating control is relaxed (that is, the threshold value N is reduced) on condition that the filter differential pressure Pb at the end of heating is larger than a predetermined value.

In step S315, when it is determined that the change amount (Pa-Pb) of the filter differential pressure is smaller than the reference change amount ΔP, it is assumed that the fuel filter 41 is clogged with foreign matter, and information to that effect is provided. It may be configured to be stored in a memory. Further, when the clogging occurs, the user or the like may be notified to that effect.

<Third Embodiment>
In the fuel filter 41, clogging due to fuel wax is likely to occur immediately after the engine is started (immediately after the cold start), and it is considered that the degree of clogging increases as the engine start is repeated. One of the features of the present embodiment is that the execution conditions of the second heating control are set in consideration of such an actual situation, and the execution conditions are different from those of the first embodiment. Hereinafter, the heater energization control process in the present embodiment will be described with reference to FIG. 11 with reference to the configuration relating to the difference from the first embodiment.

In the heater energization control process, first, the fuel temperature is acquired in step S401, and it is determined in the subsequent step S402 whether or not the heater 42 is turned off. If an affirmative determination is made in step S402, it is determined in step S403 whether or not the fuel temperature is lower than the reference temperature T0. If an affirmative determination is made in step S403, the process proceeds to step S404. The processes of steps S401 to S403 are the same as the processes of steps S201 to S203 in the first embodiment.

In step S404, it is determined whether or not the engine has started. Specifically, it is determined whether or not the engine start switch has been turned on by the user. If an affirmative determination is made in step S404, the value of the start counter is incremented by 1. In the ECU 50, the number of times the engine is started is grasped by the value of the start counter. After executing the process of step S405, or when a negative determination is made in step S404, the process proceeds to step S406.

In step S406, it is determined whether or not the value of the start counter is less than the threshold value M. This threshold value M is a criterion for determining whether the heater energization control is the first heating control or the second heating control, and becomes smaller as the cloud point CP becomes higher, that is, as the kinematic viscosity becomes higher. It is stipulated in.

If an affirmative determination is made in step S406, the first heating control is executed. Specifically, the first target temperature T1 is set as the heating target temperature in step S407, and then the heater 42 is turned on in step S410, and then this control process is terminated. Heating with the heating target temperature as the first target temperature T1 is continued until the fuel temperature reaches the first target temperature T1 (steps S411 to S412).

If a negative determination is made in step S406, the second heating control is executed. Specifically, the second target temperature T2 is set as the heating target temperature in step S408, and then the start counter is cleared to 0 in step S409. After that, the heater 42 is turned on in step S410, and then this control process is terminated. Heating with the heating target temperature as the second target temperature T2 is continued until the fuel temperature reaches the second target temperature T2 (steps S411 to S412).

In this way, by switching between the first heating control and the second heating control according to the number of engine starts (1 trip = 1 count), the heating control is executed according to the actual situation that wax is likely to be deposited when the engine is started. This makes it possible to preferably realize stabilization of the fuel supply.

As shown in the present embodiment, in the configuration in which the first heating control / the second heating control is performed according to the number of engine starts, the residual amount of wax when the engine is stopped is actually measured or estimated, and the residual amount exceeds a predetermined amount. If this is the case, it is possible to further stabilize the fuel supply by performing the second heating control regardless of the number of starts at the next engine start.

Further, when the engine is stopped during the second heating control, the heating control at the next engine start can be configured to be the second heating control regardless of the number of engine starts.

It is determined whether or not the value of the operation counter has reached the threshold value N and whether or not the value of the start counter has reached the threshold value M. It may be configured to execute heating control. In this case, it is preferable that both counters are cleared when the second heating control is executed.

<Fourth Embodiment>
The configuration of the present embodiment is different from that of the first embodiment in that the configuration is such that whether or not the second heating control is performed is determined in consideration of the transition of the residual amount of wax. After the execution of the first heating control, the wax remains in the fuel filter 41, and the residual amount is not constant every time, and it is considered that the wax gradually increases as the number of executions increases. In this case, it is considered desirable to execute the first heating control if the wax residual amount is small, and it is desirable to execute the second heating control if the wax residual amount is large. Further, the residual amount of wax can be grasped as the filter differential pressure which is the front-rear differential pressure of the fuel filter 41. Therefore, in the present embodiment, the filter differential pressure at the time when the heating start condition is satisfied is acquired, and it is determined whether to execute the first heating control or the second heating control based on the filter differential pressure.

Hereinafter, the heater energization control process in the present embodiment will be described with reference to FIG. 12, focusing on the differences from the first embodiment.

In the heater energization control process in the present embodiment, first, the fuel temperature is acquired in step S501, and it is determined in the subsequent step S502 whether or not the heater 42 is turned off. If an affirmative determination is made in step S502, it is determined in step S503 whether or not the fuel temperature is lower than the reference temperature T0. If an affirmative determination is made in step S503, the process proceeds to step S504. The processes of steps S501 to S503 are the same as the processes of steps S201 to S203 in the first embodiment.

The filter unit 13 in the present embodiment is also provided with the same differential pressure sensor 45 as in the second embodiment, and in step S504, the filter differential pressure detected by the differential pressure sensor 45 is acquired. This filter differential pressure is the differential pressure generated by the residual wax in the fuel filter 41 after the heating of the heater 42 by the first heating control is executed and when the fuel temperature drops to the reference temperature T0, and is the differential pressure generated at the start of heating. It corresponds to the residual amount of wax. In the following step S505, it is determined whether or not the acquired filter differential pressure is less than the threshold value X.

Here, if the filter differential pressure is less than the threshold value X, even if the first heating control is executed this time, the amount of wax thereafter, that is, when the fuel temperature drops to the reference temperature T0 again after the execution of the first heating control. It is considered that the residual amount of wax in the wax does not exceed the permissible level. On the other hand, if the filter differential pressure is equal to or higher than the threshold value X, when the first heating control is executed this time, the amount of wax thereafter, that is, when the fuel temperature drops to the reference temperature T0 again after the execution of the first heating control. It is considered that the residual amount of wax exceeds the allowable level.

Therefore, if the filter differential pressure is less than the threshold value X (that is, if step S505 is YES), the process proceeds to step S506, and the first target temperature T1 is set as the heating target temperature. In this case, the first heating control is executed, and a part of the wax is removed while giving priority to the reduction of power consumption. If the filter differential pressure is equal to or higher than the threshold value X (that is, if step S505 is NO), the process proceeds to step S507 to set the second target temperature T2 as the heating target temperature. In this case, the second heating control will be executed and the wax will be completely removed.

As described above, if the transition of the filter differential pressure (residual amount of wax) is reflected in the heating control, the function of reducing power consumption and the function of stabilizing the operation of the engine can be suitably compatible with each other.

<Fifth Embodiment>
In the first embodiment or the like, after the heating of the heater 42 is started, the heating is terminated when the fuel temperature reaches the heating target temperature. In the present embodiment, the configuration related to the heating end condition is different from that of the first embodiment, and the heating is terminated when the elapsed time after the start of heating of the heater 42 reaches a predetermined heating time. .. Hereinafter, the heater energization control process in the present embodiment will be described with reference to FIG. 13, and then the configuration related to the above differences will be described.

In the heater energization control process in the present embodiment, first, the fuel temperature is acquired in step S601, and in the subsequent step S602, it is determined whether or not the heater 42 is turned off. If an affirmative determination is made in step S602, it is determined in step S603 whether or not the fuel temperature is lower than the reference temperature T0. If an affirmative determination is made in step S603, the process proceeds to step S604. The processes of steps S601 to S604 are common to the processes of steps S201 to S204 in the first embodiment.

If the value of the operation counter does not reach the threshold value N, the first heating control in steps S605 to S607 is executed. Specifically, in step S605, the first heating time Y1 is set in the timer counter. The first heating time Y1 is the heater energization time when the first heating control is performed. Then, the operation counter is incremented by 1 and the heater 42 is turned on (steps S606 and S607).

Further, when the value of the operation counter reaches the threshold value N, the second heating control in steps S607 to S609 is executed. Specifically, in step S608, the second heating time Y2 is set in the timer counter. The second heating time Y2 is the heater energization time when the second heating control is performed, and is the time when Y2> Y1. Then, the operation counter is cleared and the heater 42 is turned on (steps S609 and S607).

The heating times Y1 and Y2 may be set in the parameter setting process of FIG. 3 described above. In this case, in steps S104 and S106 of FIG. 3, instead of setting the target temperatures T1 and T2 based on the cloud point CP and the melting point MP, the heating times Y1 and Y2 are set based on the cloud point CP and the melting point MP. do. It is also possible to store the correspondence between the target temperatures T1 and T2 and the heating times Y1 and Y2, and set the heating times Y1 and Y2 based on the target temperatures T1 and T2.

The value of the timer counter is subtracted each time the heater energization control process is executed while the heater 42 is ON (step S610), and the heating ends when the value of the timer counter becomes 0 (steps S611 to S612). ..

Also in the present embodiment, as described above, the first heating control enables the removal of precipitates while giving priority to the suppression of power consumption associated with the energization of the heater, and the second heating control gives priority to the removal of wax. Precipitates can be removed. Therefore, by appropriately selecting the two heating controls, it is possible to appropriately remove the wax while reducing the power consumption, unlike the case where, for example, one heating control is executed.

<Sixth Embodiment>
When the wax adhering to the fuel filter 41 is melted by heating, it is considered that there is a temperature range in which the melting efficiency is high in terms of the fuel temperature and the degree of melting (that is, the change in the differential pressure of the filter). Further, when the first heating control is repeatedly executed in order to alleviate the clogging of the fuel filter 41, it is considered that the temperature range in which the wax melting efficiency is high changes according to the number of times the first heating control is executed.

More specifically, as shown in FIG. 14, in a predetermined temperature range from the beginning of melting, the effect of reducing the filter differential pressure becomes larger than in a temperature range different from that temperature range. Then, by repeating heating / cooling, the temperature at which the wax begins to melt gradually rises, and accordingly, the predetermined temperature range having a large reduction effect also shifts to the high temperature side (second target temperature T2 side).

Therefore, in the present embodiment, the first target temperature T1 is changed to a higher temperature side than the previous execution time at the later execution time among the execution times of the first heating control a plurality of times. That is, in the case of performing the first heating control, the ECU 50 first performs the heating according to the number of executions of the first heating control (that is, the change in the melting start temperature) so that the heating is performed in the above-mentioned predetermined temperature range. The target temperature T1 is changed to the high temperature side (second target temperature T2 side).

In this way, if the first target temperature T1 is changed to the high temperature side according to the predetermined temperature range according to the number of executions, even if the heating temperature at the time of performing the first heating control is suppressed, the filter difference. The pressure reduction effect can be fully exerted.

<Other embodiments>
The heating may be terminated when the amount of electric power of the heater reaches a predetermined value after the heating of the heater 42 is started. In this case, when the first heating control is carried out, the heating is terminated when the integrated power after the start of the heater heating becomes the first electric energy W1, and when the second heating control is carried out, the heater heating is started. Heating is terminated when the later integrated power reaches the second electric energy W2. The electric energy W1 and W2 are often set based on, for example, the cloud point CP and the melting point MP, and W1 <W2.

-In each of the above embodiments, the fuel temperature is actually measured by the fuel temperature sensor 43, but the present invention is not limited to this. For example, an outside air temperature sensor or an intake air temperature sensor and a water temperature sensor 53 for cooling water may be used in combination, and the fuel temperature may be estimated based on the detection results from each of these sensors.

-In each of the above embodiments, the kinematic viscosity of the fuel is actually measured using the kinematic viscosity sensor 44, but it is also possible to estimate the kinematic viscosity instead of actually measuring it. For example, it is also possible to estimate the kinematic viscosity from the fuel density and the cetane number. It is also possible to provide an in-cylinder pressure sensor and estimate the kinematic viscosity (molecular structure) from the ignition delay time of the fuel detected by the in-cylinder pressure sensor. Based on these estimation results, the reference temperature T0, the target temperatures T1, T2, the threshold value N, and the like may be set.

-In each of the above embodiments, the case where the fuel temperature sensor 43 is arranged on the downstream side of the fuel filter 41 is illustrated, but it is also possible to dispose of the fuel temperature sensor 43 on the upstream side of the fuel filter 41. Further, the kinematic viscosity sensor 44 does not necessarily have to be arranged on the downstream side of the fuel filter 41, and may be arranged, for example, between the heater 42 and the fuel filter 41, or on the upstream side of the heater 42.

In each of the above embodiments, the temperature lower than the cloud point CP is set as the reference temperature T0, but it is also possible to set the reference temperature T0 = cloud point CP. Further, for example, for the first target temperature T1, any temperature that can reduce the filter differential pressure is sufficient, and for example, the cloud point CP = the first target temperature T1 can be set. In this case, it is preferable to set the reference temperature T0 to a temperature lower than the cloud point CP. Further, the second target temperature T2 is sufficient if it is higher than the first target temperature T1, and for example, the second target temperature T2 can be set to a temperature lower than the melting point MP. In short, the first heating control may be such that a part of the wax in the fuel filter 41 is removed by heating the heater 42, and the second heating control is more wax than the first heating control by heating the heater 42. Should be removed.

-The heating start condition of the heater 42 may be changed. For example, it may be determined that wax is attached to the fuel filter 41 based on the outside air temperature and the water temperature, and the heater heating under the first heating control may be performed at a predetermined time cycle at the time of the adhesion determination. .. In this case, after the start of heating under the first heating control, it is advisable to end the heating based on the target temperature, the heating time, and the like as described above.

10 ... fuel tank, 11 ... fuel pump, 41 ... fuel filter, 42 ... heater, 50 ... ECU (heater control device).

Claims (11)

A fuel filter (41) arranged in the fuel path from the fuel tank (10) to the fuel pump (11) to filter the fuel, and a heater (42) for heating the fuel supplied to the fuel filter by energization are provided. It is a heater control device (50) that is applied to the fuel supply system provided and controls the energization of the heater.
A condition determination unit for determining the success or failure of the heating start condition of the heater in a state where fuel precipitates are attached to the fuel filter.
When it is determined that the heating start condition is satisfied, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater and the first heating control for heating the heater are more than the first heating control. A heating control unit that selectively executes one of the second heating controls for removing a large amount of the precipitates,
Equipped with
The heating control unit
As the first heating control, the heater is heated until the fuel temperature reaches the first target temperature (T1) equal to or higher than the cloud point of the fuel after the heating of the heater is started.
As the second heating control, a heater control device that executes heating of the heater until the fuel temperature reaches a second target temperature (T2) higher than the first target temperature after the heating of the heater is started. The heater control device according to claim 1 , wherein the first target temperature is a temperature equal to or higher than the cloud point and lower than the melting point of the precipitate, and the second target temperature is a temperature equal to or higher than the melting point of the precipitate. .. The heating control unit executes the second heating control after repeatedly executing the first heating control a plurality of times.
The heater control device according to claim 1 or 2 , wherein the first target temperature is changed to a higher temperature side than in the previous execution at a later execution time among the execution times of the first heating control a plurality of times. A fuel filter (41) arranged in the fuel path from the fuel tank (10) to the fuel pump (11) to filter the fuel, and a heater (42) for heating the fuel supplied to the fuel filter by energization are provided. It is a heater control device (50) that is applied to the fuel supply system provided and controls the energization of the heater.
A condition determination unit for determining the success or failure of the heating start condition of the heater in a state where fuel precipitates are attached to the fuel filter.
When it is determined that the heating start condition is satisfied, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater and the first heating control for heating the heater are more than the first heating control. A heating control unit that selectively executes one of the second heating controls for removing a large amount of the precipitates,
An execution count counting unit that counts the number of times the first heating control is repeatedly executed, and
Equipped with
The heating control unit is a heater control device that executes the second heating control based on the number of executions reaching a predetermined value. A fuel filter (41) arranged in the fuel path from the fuel tank (10) to the fuel pump (11) to filter the fuel, and a heater (42) for heating the fuel supplied to the fuel filter by energization are provided. A heater control device (50) that is applied to a fuel supply system that supplies fuel discharged from the fuel pump to the engine and controls energization of the heater.
A condition determination unit for determining the success or failure of the heating start condition of the heater in a state where fuel precipitates are attached to the fuel filter.
When it is determined that the heating start condition is satisfied, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater and the first heating control for heating the heater are more than the first heating control. A heating control unit that selectively executes one of the second heating controls for removing a large amount of the precipitates,
A start count unit that counts the start count of the engine, and a start count unit.
Equipped with
The heating control unit is a heater control device that executes the second heating control based on the number of starts having reached a predetermined value. Equipped with a kinematic viscosity acquisition unit that acquires the kinematic viscosity of fuel
The heater according to any one of claims 1 to 5 , wherein the heating control unit sets an execution mode of a heater energization control including the first heating control and the second heating control based on the kinematic viscosity. Control device. The heater control device according to claim 6 , wherein the heating control unit sets execution conditions for the second heating control as an execution mode of the heater energization control based on the kinematic viscosity. When the heating control unit can acquire the kinematic viscosity by detection or estimation, the execution mode of the heater energization control is set based on the detected value of the kinematic viscosity, and the acquisition of the kinematic viscosity by detection or estimation is impossible. The heater control device according to claim 6 or 7 , wherein the execution mode of the heater energization control is set by using the maximum value of the kinematic viscosity in the predetermined kinematic viscosity setting range. The second heating control is to execute heating by the heater until the temperature reaches a temperature equal to or higher than the melting point of the precipitate.
A differential pressure acquisition unit for acquiring the differential pressure on the upstream side and the downstream side of the fuel filter is provided.
A claim that the heating control unit sets an execution mode of a heater energization control including the first heating control and the second heating control based on the differential pressure at the end of heater heating by the second heating control. The heater control device according to any one of 1 to 8 . The heating control unit has the first heating control and the second heating control when the differential pressure at the end of the heater heating by the second heating control is large as compared with the case where the differential pressure is small. The heater control device according to claim 9 , wherein the second heating control is executed more frequently. A fuel filter (41) arranged in the fuel path from the fuel tank (10) to the fuel pump (11) to filter the fuel, and a heater (42) for heating the fuel supplied to the fuel filter by energization are provided. It is a heater control device (50) that is applied to the fuel supply system provided and controls the energization of the heater.
A condition determination unit for determining the success or failure of the heating start condition of the heater in a state where fuel precipitates are attached to the fuel filter.
When it is determined that the heating start condition is satisfied, the first heating control for removing a part of the precipitate in the fuel filter by heating the heater and the first heating control for heating the heater are more than the first heating control. A heating control unit that selectively executes one of the second heating controls for removing a large amount of the precipitates,
A residual amount determining unit for determining whether or not the residual amount of the precipitate of the fuel filter after executing heating of the heater by the first heating control is less than a predetermined amount.
Equipped with
The heating control unit executes either the first heating control or the second heating control based on whether or not the residual amount of the precipitate is less than a predetermined amount when the heating start condition is satisfied. A heater control device that determines whether or not.

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