JP2017136935A - Hybrid vehicle and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid vehicle capable of suppressing melting damage of a filter for exhaust emission control and a control method thereof.SOLUTION: A hybrid vehicle includes: a hybrid system 20 which has an engine 10 and a motor generator 21; a filter 42 for exhaust emission control which is arranged in an exhaust passage 41 of the engine; and a control device 70. In the hybrid vehicle, the control device is configured to execute control processing for stopping fuel injection of the engine and rotating an output shaft 13 of the engine by the motor generator when the temperature of the filter is a reference temperature Tc set in advance or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hybrid vehicle and a control method thereof.

  In recent years, a hybrid vehicle (hereinafter referred to as “HEV”) including a hybrid system having an engine and a motor generator that are controlled in combination according to the driving state of the vehicle has attracted attention from the viewpoint of improving fuel efficiency and environmental measures. . In this HEV, driving force is assisted by a motor generator when the vehicle is accelerated or started, while regenerative power generation is performed by the motor generator during inertia traveling or braking (see, for example, Patent Document 1).

  Conventionally, an HEV including an exhaust purification filter is also known (see, for example, Patent Document 2). The filter is disposed in the exhaust passage of the engine, and purifies the exhaust gas by collecting particulate matter (PM) in the exhaust discharged from the engine.

  Incidentally, when a large amount of PM accumulates on the filter, the performance of the filter is degraded. Therefore, conventionally, when a predetermined condition that it is desired to regenerate the filter is satisfied, for example, when the amount of PM accumulated on the filter exceeds a reference value, the exhaust gas upstream of the filter is exhausted. By supplying fuel to the passage, the exhaust temperature is raised to the combustion temperature of PM (for example, 400 ° C. to 600 ° C.) by the combustion heat of the fuel, and the control processing (filter regeneration control) that burns and removes the PM accumulated on the filter Process).

  However, when the above-described filter regeneration control process is executed, even if PM accumulated on the filter causes self-combustion, even if the fuel supply to the exhaust passage upstream of the filter is stopped, PM There is a possibility that the temperature of the filter may continue to rise due to abrupt expansion of self-combustion due to heat generated by self-combustion, that is, thermal runaway may occur. If this thermal runaway occurs, the filter may melt.

JP 2002-238105 A JP 2010-7520 A

  The present invention has been made in view of the above, and an object of the present invention is to provide a hybrid vehicle and a control method therefor that can suppress melting damage of an exhaust purification filter.

  To achieve the above object, a hybrid vehicle according to the present invention includes a hybrid system having an engine and a motor generator, an exhaust purification filter disposed in an exhaust passage of the engine, and a control device. The control device executes a control process of stopping the fuel injection of the engine and rotating the output shaft of the engine by the motor generator when the temperature of the filter is equal to or higher than a preset reference temperature. It is comprised as follows.

  According to the hybrid vehicle of the present invention, when the temperature of the filter is equal to or higher than the reference temperature, the fuel injection of the engine is stopped, and the engine output shaft is rotated by the motor generator. And fresh air can be discharged. The fresh air exhausted from the engine can remove the heat of the filter and cool the filter to lower the temperature of the filter, so that the filter can be prevented from being melted.

  The above-described configuration includes an EGR system that recirculates a part of the exhaust gas in the exhaust passage to the intake passage, and the control device includes a part of the exhaust gas by the EGR system when the temperature of the filter is equal to or higher than the reference temperature. The control process for stopping the return to the intake passage may be further executed.

  According to this configuration, when the temperature of the filter is equal to or higher than a preset reference temperature, a part of the exhaust in the exhaust passage is stopped from returning to the intake passage, and the temperature of the fresh air discharged from the engine is reduced. It is possible to suppress an increase due to exhaust gas recirculation by the EGR system. Thereby, it can suppress effectively that the temperature of the fresh air which flows into a filter raises, and can reduce the temperature of a filter rapidly. As a result, the melting loss of the filter can be effectively suppressed.

  In the above configuration, when the temperature of the filter is equal to or higher than the reference temperature, the control device lowers the gear stage of the transmission of the hybrid vehicle as compared with the case where the temperature of the filter is lower than the reference temperature. May be further executed. According to this configuration, the rotational speed of the engine can be increased by reducing the gear stage of the transmission. Thereby, since the amount of fresh air flowing into the filter can be increased and the temperature of the filter can be effectively reduced, the melting loss of the filter can be effectively suppressed.

  In addition, a hybrid vehicle control method according to the present invention for achieving the above object includes a hybrid system including an engine and a motor generator, and an exhaust purification filter disposed in an exhaust passage of the engine. In this control method, when the temperature of the filter is equal to or higher than a preset reference temperature, the fuel injection of the engine is stopped and the control process of rotating the output shaft of the engine by the motor generator is executed. Features.

  According to the hybrid vehicle control method of the present invention, when the temperature of the filter is equal to or higher than the reference temperature, the fuel injection of the engine is stopped and the output shaft of the engine is rotated by the motor generator so that the engine is in a non-combustion state. You can inhale and discharge fresh air. The fresh air exhausted from the engine can remove the heat of the filter and cool the filter to lower the temperature of the filter, so that the filter can be prevented from being melted.

  According to the hybrid vehicle and the hybrid vehicle control method of the present invention, it is possible to suppress the melting loss of the exhaust purification filter.

It is a block diagram of the hybrid vehicle which consists of embodiment of this invention. It is a flowchart for demonstrating a filter high temperature control process.

Hereinafter, a hybrid vehicle and a control method thereof according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a hybrid vehicle according to the present embodiment. This hybrid vehicle (hereinafter referred to as “HEV”) is a normal passenger car or a large vehicle such as a bus or truck, and is a hybrid that controls the HEV in combination with the engine 10, the motor generator 21 and the transmission 30, depending on the driving state. System 20 is mainly provided.

  In the engine 10, a crankshaft 13 as an output shaft is rotationally driven by thermal energy generated by combustion of fuel in a plurality (four in this example) of cylinders 12 formed in the engine body 11. The engine 10 is a diesel engine or a gasoline engine. In the present embodiment, a diesel engine is used as an example of the engine 10. One end of the crankshaft 13 is connected to one end of a rotating shaft 22 of the motor generator 21 via an engine clutch 14 (for example, a wet multi-plate clutch).

  The motor generator 21 is a permanent magnet AC synchronous motor capable of generating operation. The other end of the rotating shaft 22 of the motor generator 21 is connected to an input shaft 31 of the transmission 30 through a motor clutch 15 (for example, a wet multi-plate clutch).

  The transmission 30 is an AMT or AT that automatically shifts to a target gear determined based on the HEV operating state and preset map data. The transmission 30 is not limited to an automatic transmission type such as AMT, and may be a manual type in which a driver manually changes gears.

  In the present embodiment, an AMT is used as an example of the transmission 30.

  The rotational power changed by the transmission 30 is transmitted to the differential 34 through the propeller shaft 33 connected to the output shaft 32, and is distributed as a driving force to the pair of driving wheels 35 as rear wheels.

  The hybrid system 20 includes a motor generator 21, an inverter 23, a high voltage battery 24, a DC / DC converter 25, and a low voltage battery 26 that are electrically connected to the motor generator 21 in order.

  Preferred examples of the high voltage battery 24 include a lithium ion battery and a nickel metal hydride battery. As the low voltage battery 26, a lead battery is used.

  The DC / DC converter 25 has a function of controlling the charge / discharge direction and the output voltage between the high voltage battery 24 and the low voltage battery 26. The low voltage battery 26 supplies power to various vehicle electrical components 27.

  Various parameters in the hybrid system 20, such as a current value, a voltage value, and an SOC, are detected by a BMS 28 (battery management system).

The engine 10 and the hybrid system 20 are controlled by the control device 70. Specifically, at the time of HEV start or acceleration, the hybrid system 20 assists at least a part of the driving force by the motor generator 21 supplied with power from the high voltage battery 24, while at the time of inertia traveling or braking. Performs regenerative power generation by the motor generator 21, converts surplus kinetic energy generated in the propeller shaft 33 and the like into electric power, and charges the high voltage battery 24. In addition, this HEV can perform so-called motor independent travel using only the motor generator 21 as a drive source by disengaging the engine clutch 14 and engaging the motor clutch 15, for example.

  In this embodiment, an electronic control device is used as the control device 70. This electronic control device includes a CPU having a function as a control unit for executing various control processes, and a ROM, a RAM, etc. having a function as a storage unit for storing various data and programs used for the operation of the CPU. A microcomputer is provided. The control device 70 is connected to each part such as the motor generator 21 through a signal line (indicated by a one-dot chain line).

  Note that the arrangement of the motor generator 21 of the hybrid system 20 can be connected to the output shaft (crankshaft 13) of the engine 10 to assist in regenerative power generation or driving force when receiving a control command from the control device 70. Any configuration may be used, and the configuration is not limited to the configuration illustrated in FIG. 1 (the configuration in which the engine clutch 14 is interposed between the engine 10 and the motor generator 21).

  The HEV also includes an EGR system 45 (a system that recirculates part of the exhaust gas in the exhaust passage 41 to the intake passage). Specifically, the EGR system 45 includes an EGR passage that branches from the middle of an exhaust passage 41 on the upstream side of the filter 42, which will be described later, and merges in the middle of the intake passage of the engine 10, and an EGR that opens and closes the EGR passage. And a valve. In response to a control command from the control device 70, the EGR valve is opened and closed to control inflow, stoppage of inflow, and inflow of a part of exhaust gas (EGR gas) into the engine 10.

  The HEV also includes an exhaust purification filter 42 in the middle of the exhaust passage 41 through which the exhaust from the engine 10 passes. The type of the filter 42 is not particularly limited as long as it can collect and remove PM in the exhaust gas. In this embodiment, a diesel particulate filter is used as an example of the filter 42. An exhaust purification catalyst (not shown) is also arranged in the exhaust passage 41 upstream of the filter 42.

  The HEV includes a temperature sensor 43 that detects the temperature of the filter 42. The detection result of the temperature sensor 43 is transmitted to the control device 70.

  By the way, when PM in exhaust gas accumulates on the filter 42, the performance of the filter 42 will fall. Therefore, the control device 70 according to the present embodiment executes a control process described below in order to burn the PM deposited on the filter 42 and restore the performance of the filter 42.

  Specifically, the control device 70, when a predetermined condition (hereinafter referred to as a predetermined condition) for which PM accumulated on the filter 42 is desired to be combusted is satisfied, the exhaust passage 41 on the upstream side of the filter 42. A control process for supplying fuel to the engine (hereinafter, this control process is referred to as a filter regeneration control process) is executed. Specifically, a fuel injection valve that injects fuel toward the exhaust in the exhaust passage 41 in a portion of the exhaust passage 41 according to the present embodiment upstream of the filter 42 and downstream of the engine body 11 (see FIG. (Not shown) is arranged. Then, the control device 70 supplies fuel from the fuel injection valve into the exhaust passage 41 on the upstream side of the filter 42 when the predetermined condition described above is satisfied.

  By performing the filter regeneration control process, the fuel supplied to the upstream side of the filter 42 is combusted, so that the temperature of the filter 42 is raised by the combustion heat, and PM deposited on the filter 42 can be burned and removed. Thereby, the filter 42 can be regenerated.

  The specific content of the predetermined condition described above is not particularly limited. For example, the condition that the amount of PM deposited on the filter 42 is equal to or greater than a preset reference value, and the HEV travel distance is Various conditions such as a condition that the distance is greater than a preset reference distance can be used.

  In addition, when the temperature (T) of the filter 42 becomes equal to or higher than a preset reference temperature (Tc), the control device 70 stops fuel injection of the engine 10, and uses the motor generator 21 to crank the engine 10. 13 (that is, this control process is referred to as a filter high temperature control process) is executed. The details of the high-temperature filter control process are as follows.

  FIG. 2 is a flowchart for explaining the filter high temperature control process. The control device 70 repeatedly executes the flowchart of FIG. 2 at a predetermined cycle. In step S10, the control device 70 determines whether or not the temperature (T) of the filter 42 is equal to or higher than a preset reference temperature (Tc).

  Note that the control device 70 of the present embodiment constantly monitors the temperature of the filter 42 after the HEV is started. However, the timing at which the control device 70 acquires the temperature of the filter 42 is not limited to this. For example, the control device 70 starts acquiring the temperature of the filter 42 after starting the above-described filter regeneration control process. May be.

  Further, the specific value of the reference temperature (Tc) is not particularly limited, but in the present embodiment, the temperature at which the filter 42 is melted (damaged by heat) (1000 ° C. is used as an example). And a temperature higher than the combustion temperature of PM (for example, a temperature selected from 400 ° C. to 600 ° C.). For this reference temperature (Tc), an appropriate value is obtained in advance by experiments, simulations, etc., and stored in a storage unit (for example, ROM) (that is, set in advance). In the present embodiment, 900 ° C. is used as an example of the reference temperature (Tc). When it is determined that the temperature (T) of the filter 42 acquired based on the detection result of the temperature sensor 43 has become equal to or higher than the reference temperature (Tc) of the storage unit, the control device 70 determines YES in step S10. In addition, the control apparatus 70 performs a flowchart from a start, when it determines with NO by step S10 (return).

  When it is determined YES in step S10, the control device 70 stops the fuel injection of the engine 10 and drives the motor generator 21 (MG) using the power of the high voltage battery 24, thereby causing the motor generator 21 to The crankshaft 13 of the engine 10 is rotated (step S20). If the engine clutch 14 is in the disconnected state before the execution of step S20, the control device 70 rotates the crankshaft 13 with the motor generator 21 after the engine clutch 14 is in the engaged state.

  By executing step S20, the engine 10 can inhale in a non-combustion state and discharge fresh air. The fresh air exhausted from the engine 10 can remove the heat of the filter 42 and cool the filter 42 to lower the temperature of the filter 42. As a result, the melting loss of the filter 42 can be suppressed.

Although the execution period of step S20 is not particularly limited, the control device 70 according to the present embodiment continues step S20 for a period during which the temperature of the filter 42 is determined to be equal to or higher than the reference temperature (Tc). And run. That is, in this case, the fuel injection stop of the engine 10 and the rotation of the crankshaft 13 by the motor generator 21 according to step S20 are continuously executed while the temperature of the filter 42 is equal to or higher than the reference temperature. When the temperature drops below the reference temperature, execution is stopped.

  Alternatively, the control device 70 determines whether or not the temperature of the filter 42 has decreased to the combustion temperature of PM once the execution of step S20 has started, and the temperature of the filter 42 has decreased to the combustion temperature of PM. If it is determined, the fuel injection stop according to step S20 and the rotation of the crankshaft 13 by the motor generator 21 may be stopped.

  If it is determined YES in step S10 of FIG. 2 during the execution of the filter regeneration control process described above, the control device 70 stops the execution of this filter regeneration control process (that is, from the filter 42). Step S20 is performed after the fuel supply to the upstream exhaust passage 41 is stopped. Then, the control device 70 may resume the execution of the filter regeneration control process after the temperature of the filter 42 is decreased by the execution of step S20 and the execution of step S20 is terminated.

  According to the present embodiment described above, the filter high temperature control process according to step S20 is executed, whereby the heat of the filter 42 can be taken away by the fresh air exhausted from the engine 10, and thereby the filter 42 Can be cooled to lower the temperature of the filter 42. As a result, the melting loss of the filter 42 can be suppressed.

  Further, in the case of the present embodiment, not only during the HEV traveling stop but also during the HEV traveling, the fuel injection of the engine 10 can be stopped and the crankshaft 13 of the engine 10 can be rotated by the motor generator 21. It is possible to prevent the filter 42 from being melted even during HEV traveling.

  Specifically, for example, when the filter regeneration control process is executed while the HEV is running with the driving force of the engine 10, the control is performed when the temperature of the filter 42 becomes equal to or higher than the reference temperature (YES in step S 10). The apparatus 70 keeps the HEV running by driving the motor generator 21 with the electric power of the high voltage battery 24 with the motor clutch 15 in the engaged state, and stops the fuel injection of the engine 10 and causes the crankshaft 13 to be stopped by the motor generator 21. Is rotated (step S20). Thereby, even during HEV traveling, the filter 42 can be cooled with fresh air exhausted from the engine 10 without hindering HEV traveling, and the melting loss of the filter 42 can be suppressed.

(Modification 1 of the above embodiment)
Next, HEV according to Modification 1 of the above embodiment will be described. The HEV control device 70 according to the present modification example determines that the temperature (T) of the filter 42 is equal to or higher than a preset reference temperature (Tc) (when YES is determined in step S10). When executing step S20, a control process for stopping the recirculation of a part of the exhaust gas to the intake passage by the EGR system 45 is further executed. Specifically, in step S20, the control device 70 according to the present modification stops the exhaust gas recirculation by the EGR system 45 by closing the EGR valve, stops the fuel injection of the engine 10, and the motor generator 21. As a result, the crankshaft 13 of the engine 10 is rotated.

According to this modification, when the temperature (T) of the filter 42 is equal to or higher than a preset reference temperature (Tc), exhaust gas recirculation by the EGR system 45 can be stopped. It is possible to suppress the temperature of the gas from rising due to the exhaust gas recirculation by the EGR system 45. Thereby, it can suppress effectively that the temperature of the fresh air which flows in into the filter 42 rises, and can reduce the temperature of the filter 42 rapidly.
As a result, the melting loss of the filter 42 can be effectively suppressed.

(Modification 2 of the above embodiment)
Next, HEV according to Modification 2 of the above embodiment will be described. The HEV control device 70 according to the present modification example determines that the temperature (T) of the filter 42 is equal to or higher than a preset reference temperature (Tc) (when YES is determined in step S10). The gear stage lowering control process for lowering the gear stage of the transmission 30 as compared to before the determination of YES in step S10 (that is, when the temperature of the filter 42 is lower than the reference temperature) is further executed. This is different from the embodiment and the first modification of the above embodiment.

  Note that the control device 70 according to the present modification executes this gear stage lowering control process before executing step S20 after determining YES in step S10. Thus, in the state where the gear stage of the transmission 30 is lowered by the gear stage lowering control process to increase the engine speed and increase the displacement, the next step S20 is executed, so that the engine 10 Can be discharged. That is, by executing the gear stage lowering control process in this way, the amount of fresh air flowing into the filter 42 can be further increased as compared with the embodiment and the first modification of the embodiment.

  However, the execution timing of the gear stage lowering control process is not limited to this, and may be executed at the same time as step S20 or after execution of step S20, for example.

  As described above, according to the present modification, in addition to the effects of the above embodiment and the first modification of the above embodiment, the amount of fresh air flowing into the filter 42 is increased by executing the gear stage lowering control process. be able to. Thereby, since the temperature of the filter 42 can be reduced effectively, the melting loss of the filter 42 can be effectively suppressed.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

10 Engine 13 Crankshaft (output shaft)
20 Hybrid system 21 Motor generator 41 Exhaust passage 42 Filter 45 EGR system 70 Control device

Claims (4)

In a hybrid vehicle comprising a hybrid system having an engine and a motor generator, an exhaust purification filter disposed in an exhaust passage of the engine, and a control device,
When the temperature of the filter is equal to or higher than a preset reference temperature, the control device stops the fuel injection of the engine and executes a control process of rotating the output shaft of the engine by the motor generator. A hybrid vehicle characterized by being configured. An EGR system that recirculates part of the exhaust in the exhaust passage to the intake passage;
The control device is configured to further execute a control process for stopping recirculation of a part of the exhaust gas to the intake passage by the EGR system when the temperature of the filter is equal to or higher than the reference temperature. Item 2. The hybrid vehicle according to item 1.   The control device further executes a control process in which the gear position of the transmission of the hybrid vehicle is lowered when the temperature of the filter is equal to or higher than the reference temperature compared to when the temperature of the filter is lower than the reference temperature. The hybrid vehicle according to claim 1, configured as described above. In a control method for a hybrid vehicle, comprising: a hybrid system having an engine and a motor generator; and an exhaust purification filter disposed in an exhaust passage of the engine.
When the temperature of the filter is equal to or higher than a preset reference temperature, the fuel injection of the engine is stopped, and a control process for rotating the output shaft of the engine by the motor generator is executed. Control method.

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