Control system for hybrid vehicles

Abstract

This ensures that the filter system has a chance to regenerate even when driving downhill for extended periods. [Solution] An electronic control unit that controls a hybrid vehicle 10 equipped with an engine 11 having a filter device 26 for collecting particulate matter in the exhaust gas installed in the exhaust passage 25, and a first generator motor 12 and a second generator motor 13 as a drive source for driving, operates the engine 11 in a state where a heating process is performed to raise the temperature of the filter device 26 until the temperature of the filter device 26 reaches a predetermined temperature, if the amount of PM accumulated in the filter device 26 is above a predetermined value and the hybrid vehicle 10 is driving downhill for a long period of time.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle.

Background Art

[0002] As a hybrid vehicle, there is one equipped with an engine in which a filter device for collecting particulate matter in exhaust gas is installed in an exhaust passage. The filter device may become clogged due to the accumulation of the collected particulate matter. The particulate matter deposited on the filter device burns and is purified when the engine fuel cut is performed and oxygen is supplied to the filter device while the filter device is at a sufficiently high temperature. Therefore, filter regeneration for burning and purifying the deposited particulate matter is carried out by the engine fuel cut.

[0003] As a control device applied to the hybrid vehicle as described above, the device described in Patent Document 1 is known. This control device usually performs an engine fuel cut when the vehicle speed is equal to or higher than a predetermined speed and the accelerator is off. Further, when the deposition amount of particulate matter in the filter device is equal to or more than a predetermined value, even if the accelerator is not off, if the accelerator opening is equal to or less than a predetermined value, the control device performs an engine fuel cut to increase the opportunity of filter regeneration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when driving on a route from high altitude to low altitude, the vehicle is constantly descending, limiting the opportunities to press the accelerator pedal. When the accelerator is off, the temperature of the filter device does not rise. Therefore, when driving downhill for an extended period, even if fuel cut-off is performed, filter regeneration may not be possible. [Means for solving the problem]

[0006] A control device for a hybrid vehicle that solves the above problems is a control device applied to a hybrid vehicle that has an engine and an electric motor as a drive source for driving, the engine having a filter device for collecting particulate matter in the exhaust gas provided in the exhaust passage, and is configured to start the engine and perform temperature rise control of the filter device when it is determined that the amount of particulate matter accumulated in the filter device is greater than or equal to a predetermined value, and the hybrid vehicle has been driving downhill for a long period of time with the accelerator off, and to perform a filter regeneration process which involves cutting the fuel of the engine when the temperature of the filter device reaches a predetermined temperature. [Effects of the Invention]

[0007] The control system of the above-mentioned hybrid vehicle has the effect of ensuring an opportunity for the filter device to regenerate even when driving downhill for a long period of time. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the configuration of the drive system of a hybrid vehicle to which one embodiment of the control device is applied. [Figure 2] Figure 2 is a schematic diagram showing the configuration of one embodiment of a control device for a hybrid vehicle. [Figure 3] Figure 3 is a flowchart of the process related to the execution determination of the forced temperature rise control performed by the control device in Figure 2. [Figure 4] Figure 4 is a flowchart of the process related to forced temperature rise control performed by the control device shown in Figure 2. [Modes for carrying out the invention]

[0009] Below, one embodiment of a control device for a hybrid vehicle will be described in detail with reference to Figures 1 to 4. <Hybrid vehicle configuration> First, with reference to Figure 1, the configuration of the hybrid vehicle 10 to which the control device of this embodiment is applied will be described. The hybrid vehicle 10 is equipped with an engine 11 and two motors, a first generator motor 12 and a second generator motor 13, as a drive source for driving. The first generator motor 12 and the second generator motor 13 each have the function of a motor that generates power by receiving an electrical supply, as well as the function of a generator that generates power by receiving power from an external source. The hybrid vehicle 10 is equipped with a power split mechanism 14. The power split mechanism 14 is a planetary gear having three rotating elements: a sun gear S, a ring gear R, and a planetary carrier C. The engine 11 is connected to the planetary carrier C of the power split mechanism 14, and the first generator motor 12 is connected to the sun gear S. Furthermore, the second generator motor 13 and the drive wheels 16 are connected to the ring gear R of the power split mechanism 14 via a reduction differential mechanism 15. Furthermore, the first generator-motor 12 and the second generator-motor 13 are electrically connected to the battery 18 via the inverter 17.

[0010] Engine 11 is configured as a multi-cylinder engine with multiple cylinders 20. Figure 1 shows four cylinders 20. Engine 11 is equipped with an injector 21 and an ignition device 22 for each cylinder 20. Engine 11 also has an intake passage 23, which is the path for introducing intake air to each cylinder 20, and an exhaust passage 25, which is the path for discharging exhaust from each cylinder 20. A throttle valve 24 is installed in the intake passage 23. A filter device 26 for collecting particulate matter in the exhaust is installed in the exhaust passage 25.

[0011] <Configuration of the control system for hybrid vehicles> Figure 2 shows the configuration of the control device applied to the hybrid vehicle 10 in Figure 1. In this embodiment, the control device is configured as an electronic control unit 30 comprising an arithmetic processing unit 31, a storage device 32, an input circuit 33, and an output circuit 34. The storage device 32 stores control programs and data. The electronic control unit 30 is configured to perform various processes for controlling the hybrid vehicle 10 by having the arithmetic processing unit 31 execute the programs stored in the storage device 32. An airflow meter 35, a crank angle sensor 36, an accelerator pedal sensor 37, a vehicle speed sensor 38, and a G sensor 39 are connected to the input circuit 33 of the electronic control unit 30. The airflow meter 35 is a sensor that detects the intake air amount GA of the engine 11, and the crank angle sensor 36 is a sensor that detects the crank angle of the engine 11. The accelerator pedal sensor 37 is a sensor that detects the accelerator opening degree ACC, which is the amount of accelerator pedal operation. The vehicle speed sensor 38 is a sensor that detects the vehicle speed SPD, which is the driving speed of the hybrid vehicle 10, and the G sensor 39 is a sensor that detects the acceleration acting on the body of the hybrid vehicle 10. Meanwhile, the output circuit 34 of the electronic control unit 30 is connected to actuators of the engine 11, such as the throttle valve 24, the injectors 21 of each cylinder 20, and the ignition device 22. The inverter 17 is also connected to the output circuit 34. The electronic control unit 30 calculates the engine rotational speed NE based on the crank angle detection result. The electronic control unit 30 also calculates the engine load ratio KL based on the intake air volume GA of the engine 11, the engine rotational speed NE, etc. The engine load ratio KL represents the charging efficiency of the intake air of cylinder 20.

[0012] <Drive control of hybrid vehicles 10> Next, an overview of the drive control of the hybrid vehicle 10 performed by the electronic control unit 30 will be explained. When performing drive control, the electronic control unit 30 first calculates the required driving force based on the accelerator pedal position (ACC), vehicle speed (SPD), etc. The required driving force represents the driving force of the hybrid vehicle 10 requested by the driver through the operation of the accelerator pedal. Next, the electronic control unit 30 calculates the charge / discharge required power based on the charge state of the battery 18, etc. The charge / discharge required power represents the driving force required for the traction / regenerative drive of the second generator motor 13 necessary to bring the charge state of the battery 18 within an appropriate range. Then, the electronic control unit 30 calculates the required engine output, which is the required value of the engine output, based on the required driving force and the charge / discharge required power. Subsequently, the electronic control unit 30 calculates the target rotational speed NE* and target load ratio KL* of the engine 11 based on the required engine output. The target rotational speed NE* and target load ratio KL* represent the engine rotational speed NE and engine load ratio KL that can efficiently generate an output equal to the required engine output. The electronic control unit 30 then adjusts the opening of the throttle valve 24 of the engine 11 so that the engine load ratio KL is equal to the target load ratio KL*. The electronic control unit 30 also adjusts the rotational speed of the first generator motor 12 so that the engine rotational speed NE is equal to the target rotational speed NE*. The adjustment of the rotational speed of the first generator motor 12 is performed by controlling the charging current of the first generator motor 12 to the battery 18 through the control of the inverter 17. The electronic control unit 30 also controls the inverter 17 to adjust the charging and discharging current of the second generator motor 13 based on the charge and discharge power request.

[0013] <Forced temperature rise control> As part of the hybrid vehicle 10, the electronic control unit 30 performs forced temperature rise control to forcibly raise the temperature of the filter device 26 installed in the exhaust passage 25 of the engine 11. The details of this forced temperature rise control are described below.

[0014] Figure 3 shows a flowchart of the process performed by the electronic control unit 30 to determine whether or not to perform forced temperature rise control. The electronic control unit 30 repeatedly performs the process shown in Figure 3 at predetermined control cycles while the hybrid vehicle 10 is running. Through this process, the electronic control unit 30 starts forced temperature rise control (S130) if all of the following requirements (A) to (C) are met.

[0015] Requirement (A) is that the history flag for forced temperature rise control is cleared (S100: YES). The history flag indicates whether or not forced temperature rise control was performed during the current trip of the hybrid vehicle 10. The history flag is set to a cleared state at the start of the trip of the hybrid vehicle 10.

[0016] Requirement (B) is that the PM accumulation amount is equal to or greater than the regeneration judgment value (S110: YES). The PM accumulation amount represents the amount of particulate matter accumulated in the filter device 26 of the engine 11. The electronic control unit 30 estimates the PM accumulation amount based on the operating status of the engine 11. The regeneration judgment value is the PM accumulation amount used to determine whether or not filter regeneration is necessary to burn and purify the particulate matter accumulated in the filter device 26.

[0017] Requirement (C) is that the hybrid vehicle 10 has been driving downhill for an extended period of time (S120: YES). The electronic control unit 30 determines whether or not the vehicle is driving downhill based on the tilt of the hybrid vehicle 10, for example, as determined from the detection results of the G sensor 39. When driving downhill, the engine speed NE and vehicle speed SPD become high even when the accelerator opening ACC and engine load ratio KL are small. Therefore, it is also possible to determine whether or not the vehicle is driving downhill by estimation based on the accelerator opening ACC, engine load ratio KL, engine speed NE, and vehicle speed SPD. Note that "continued driving downhill" here does not mean a state in which driving downhill is not interrupted even for a moment, but rather a state in which driving downhill is performed for most of the driving period, and the accelerator pedal is not pressed down hard during the remaining period. Furthermore, "extended period" here refers to a time shorter than the time it takes for the PM accumulation to reach the acceptable upper limit if the engine 11 is operated without regenerating the filter device 26 after the PM accumulation exceeds the regeneration judgment value.

[0018] Fig. 4 shows the processing procedure of the electronic control unit 30 in forced temperature rise control. The electronic control unit 30 starts the processing in Fig. 4 when all of the above requirements (A) to (C) are satisfied. When starting the forced temperature rise control, the electronic control unit 30 waits until the accelerator opening ACC is "0" (S200: YES) and the engine 11 is in a state where it can operate independently (S210: YES), and then starts the independent operation of the engine 11 (S230). The independent operation here refers to a state where the engine 11 generates only enough power to overcome its own friction without receiving assistance from the outside and without outputting power to the outside, and continues to operate. Then, the electronic control unit 30 starts the temperature rise process of the filter device 26 in the independently operating engine 11 (S240). The electronic control unit 30 continues the independent operation of the engine 11 after performing the temperature rise process until the filter temperature becomes equal to or higher than the preset temperature. A temperature higher than the temperature required for the combustion purification of particulate matter is set as the preset temperature. Then, when the filter temperature becomes equal to or higher than the preset temperature (S250: YES), the electronic control unit 30 ends the temperature rise process and the independent operation of the engine 11 (S260, S270). After that, the electronic control unit 30 sets the history flag (S280) and then ends the forced temperature rise control. After the start of a trip of the hybrid vehicle 10, when the forced temperature rise control is executed, the history flag is set, so requirement (A) necessary for the execution of the forced temperature rise control is no longer satisfied. Therefore, the execution of the forced temperature rise control is limited to once per trip.

[0019] The temperature rise process of the filter device 26 implemented in such forced temperature rise control can be implemented, for example, as a process of delaying the ignition timing of the engine 11. When the ignition timing is delayed, the combustion efficiency in the cylinder 20 decreases, so the temperature of the exhaust gas increases. Then, the filter device 26 is heated by receiving heat from the high-temperature exhaust gas.

[0020] In addition, the temperature increase process can also be carried out by means of the following specific cylinder fuel cut. The specific cylinder fuel cut is a process in which combustion of some of the plurality of cylinders 20 of the engine 11 is suspended and rich combustion is performed in the remaining cylinders. Rich combustion is combustion in a state where the air-fuel ratio of the air-fuel mixture is set to an air-fuel ratio richer than the theoretical air-fuel ratio. During the implementation of such a process, fresh air containing oxygen is discharged from the cylinders where combustion has been suspended, and exhaust gas containing unburned fuel is discharged from the cylinders performing rich combustion into the exhaust passage 25 respectively. The unburned fuel in the exhaust gas discharged from the cylinders performing rich combustion burns in response to the supply of oxygen from the cylinders where combustion has been suspended. As a result, the temperature of the exhaust gas flowing into the filter device 26 increases, so the temperature of the filter device 26 rises.

[0021] <Function of Embodiment> During fuel cut of the engine 11, the exhaust gas flowing into the filter device 26 is replaced by fresh air. When fuel cut is carried out in a state where the filter device 26 has reached a certain temperature or higher, the particulate matter deposited on the filter device 26 is combusted and purified. Thus, in the engine 11, in response to fuel cut, the particulate matter deposited on the filter device 26 is combusted and purified, that is, the filter device 26 is regenerated.

[0022] During downhill driving of the hybrid vehicle 10, there are many opportunities to carry out fuel cut of the engine 11. However, during downhill driving, the engine 11 is not often operated at high load, and since the amount of heat received by the filter device 26 from the exhaust gas is small, the filter device 26 cools down. Therefore, if downhill driving continues, even if fuel cut is carried out, the filter device 26 cannot be regenerated.

[0023] In response to this, the electronic control unit 30, in forced temperature rise control, will perform autonomous operation of the engine 11 if a certain amount of particulate matter has accumulated in the filter device 26 and downhill driving has continued for a long period of time. At this time, the engine 11 is normally in a state where fuel cut is performed. The electronic control unit 30 then performs a temperature rise process on the filter device 26 with the engine 11 in autonomous operation. The electronic control unit 30 continues the temperature rise process and autonomous operation until the temperature of the filter device 26 reaches a temperature higher than the temperature required to burn the particulate matter. Therefore, when fuel cut is performed afterward, the filter device 26 is regenerated.

[0024] Furthermore, if fuel cut-off is not performed while the filter device 26 is still at a high temperature after the forced temperature rise control has finished, the filter device 26 may not be sufficiently regenerated even if forced temperature rise control is performed. Since forced temperature rise control is a control that operates the engine 11 in a situation where fuel cut-off would normally occur, it results in increased fuel consumption. If forced temperature rise control is repeatedly performed until filter regeneration is complete, the fuel efficiency of the hybrid vehicle 10 will deteriorate. In response to this, the electronic control unit 30 limits the number of forced temperature rise control executions per trip to one, thereby suppressing the deterioration of fuel efficiency.

[0025] <Effects of the Embodiment> The control device for the hybrid vehicle 10 of this embodiment provides the following effects. (1) If the amount of PM accumulated in the filter device 26 is above a predetermined value (regeneration judgment value) and the hybrid vehicle 10 continues to travel downhill for a long period of time, the electronic control unit 30 operates the engine 11 while performing a heating process to raise the temperature of the filter device 26. The electronic control unit 30 continues to operate the engine 11 in this manner until the temperature of the filter device 26 reaches the predetermined temperature. Even when traveling downhill, the filter device 26 is heated to a temperature at which the accumulated particulate matter can be burned. Therefore, even when traveling downhill, opportunities to perform filter regeneration are more readily available.

[0026] (2) The electronic control unit 30 is configured to operate the engine 11 autonomously during forced temperature rise control. As a result, fuel consumption associated with the execution of forced temperature rise control is reduced compared to when the engine 11 is operated under load during forced temperature rise control.

[0027] (3) The electronic control unit 30 sets an upper limit on the number of times the forced temperature rise control is executed per trip of the hybrid vehicle 10. This prevents the forced temperature rise control from being executed repeatedly and worsening the fuel efficiency of the hybrid vehicle 10.

[0028] (Other embodiments) The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0029] If any process can promote the temperature rise of the filter device 26, the temperature rise process may be carried out by forced temperature rise control through a process other than ignition timing retardation and specific cylinder fuel cut-off.

[0030] In the forced temperature rise control, the engine 11 may be operated under load, and the power generated by the engine 11 may be absorbed by the regenerative drive of the first generator motor 12. However, fuel consumption associated with the execution of forced temperature rise control is reduced when the engine 11 is operated independently as in the above embodiment compared to this case.

[0031] The control device of the above embodiment can also be applied to hybrid vehicles with a configuration different from that shown in Figure 1, provided that the hybrid vehicle is equipped with an engine and an electric motor as the drive source for driving, and has a filter device for capturing particulate matter in the exhaust gas installed in the exhaust passage.

[0032] The maximum number of forced temperature control executions per trip for the hybrid vehicle 10 may be set to two or more. Alternatively, the number of forced temperature control executions may be unlimited. [Explanation of Symbols]

[0033] 10 Hybrid Vehicles 11 Engine 12. First Generator / Motor 13. Second Generator / Motor 17 Inverter 18 batteries 20 cylinders 21 Injectors 26 Filter device 30 Electronic control unit 31 Arithmetic Processing Unit 32 Storage device

Claims

1. A control device applicable to a hybrid vehicle equipped with an engine having a filter device for collecting particulate matter in the exhaust passage, and an electric motor as the drive source for driving, If the amount of particulate matter accumulated in the filter device exceeds a predetermined value, and the hybrid vehicle continues to drive downhill for a long period of time, a forced temperature-raising control is executed, which operates the engine while a temperature-raising process is performed to raise the temperature of the filter device until the temperature of the filter device reaches a predetermined temperature. Control system for hybrid vehicles.

2. The control device for a hybrid vehicle according to claim 1, wherein the heating process is performed while the engine is operating autonomously.

3. The control device for a hybrid vehicle according to claim 1, wherein the temperature-raising process is a process that retards the ignition timing of the engine.

4. The engine in question is a multi-cylinder engine equipped with multiple cylinders. The aforementioned temperature-raising process involves suspending combustion in some of the cylinders among the multiple cylinders and adjusting the air-fuel ratio of the mixture burned in the remaining cylinders to a richer ratio than the stoichiometric air-fuel ratio. A control device for a hybrid vehicle according to claim 1.

5. The control device for a hybrid vehicle according to claim 1, which sets an upper limit on the number of times the forced temperature rise control is executed per trip of the hybrid vehicle.

Images