JP7401021B2 - hybrid vehicle - Google Patents

Description

The present invention relates to a control technology for a hybrid vehicle including a motor (electric motor) and an engine (internal combustion engine).

It is known that the output performance of rechargeable secondary batteries (batteries) decreases at low temperatures, and the lack of driving force due to decreased battery output is recognized as an important issue, especially for plug-in type and series type hybrid vehicles. There is. In order to solve this lack of driving power, for example, Patent Document 1 states that when the driver requests an output larger than a predetermined value by operating the accelerator at low temperatures when the output performance of the battery decreases, the engine torque is temporarily reduced. A control method has been proposed to increase the amount of power generated by the generator.

Japanese Patent Application Publication No. 2019-162930

In the control method disclosed in Patent Document 1, when the driver increases the required output to a predetermined value or more at a low temperature, engine torque is increased to suppress a decrease in power performance. Therefore, the control operation depends on the driver's accelerator operation and only operates while the vehicle is driving.

However, while the vehicle is running in EV mode or stopped, the engine may be started to generate electricity regardless of the driver's accelerator operation. At this time, when the battery output is reduced, the rotational speed of the engine cannot be maintained at the target value, and the rotational speed decreases and an engine stall may occur. Although the details will be described later, the inventor found that this decrease in engine speed is caused by a torque error between the engine and the generator caused by the difference in the rate of increase in engine water temperature and oil temperature (Figure 3 ). When the accelerator is not operated, the required engine output is maintained at a predetermined value, so if the power running output of the generator is sufficient, normal control can be maintained with an output that exceeds the torque error by the power running assist of the generator.

However, the power output of the generator takes power from the battery to drive the generator and the motor, increasing the engine speed, so as the battery output decreases, the power output of the generator also decreases, resulting in extremely low temperatures or It becomes zero at the time of deterioration. When the power running output of the generator decreases in this way, the total value of the engine required output and the power running output of the generator becomes smaller than the torque error, and the engine rotation speed decreases, eventually causing the engine to stall. This will be explained below with reference to FIG.

In FIG. 1, it is assumed that the engine starts at time t1 and transitions to series travel at time t2 while the vehicle is traveling in the EV travel mode. When the engine starts, the generator drives the motor, causing the engine rotation speed to rise and reach the target rotation speed. However, when the driver is not operating the accelerator, the required engine output is a constant value, and as the battery output decreases, the power running output of the generator decreases and the generator assist decreases, the required engine output and power generation decrease. The total value together with the machine's power running output begins to fall below the torque error. As a result, the engine rotational speed cannot maintain the target and begins to gradually decrease, and at time tx, the engine stops and stalls. A control method that relies on the driver's accelerator operation, as in Patent Document 1 mentioned above, cannot prevent such engine stalling.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a hybrid vehicle that can maintain the engine rotation speed and prevent engine stalling even when the battery output is reduced. .

In order to achieve the above object, an embodiment of the present invention includes an engine, a generator mechanically connected to the output shaft of the engine and capable of regenerative operation or power operation, and a generator that generates electricity during the regenerative operation of the generator. a battery that stores the generated electric power and supplies the electric power during power operation of the generator; a motor that converts the electric power supplied from the battery into driving force for driving wheels; and controls the engine, the generator, and the motor. A hybrid vehicle comprising: a control unit, wherein the control unit determines whether, when starting the engine, the total value of the requested output of the engine and the maximum powering output of the generator is smaller than a predetermined determination threshold; and, if the total value is smaller than the predetermined determination threshold, calculate a torque feedback correction amount for the engine according to the deviation from the target rotational speed of the engine, and control the required torque of the engine. It is characterized by
Further, according to an embodiment of the present invention, the predetermined determination threshold value may be set in advance for each target rotational speed of the engine depending on the cooling water temperature of the engine.
According to an embodiment of the present invention, the control unit further determines whether the total value is smaller than a value obtained by adding a hysteresis setting value to the predetermined determination threshold; If the value is smaller than the predetermined determination threshold plus a hysteresis setting value, a torque feedback correction amount for the engine is calculated in accordance with the deviation from a target rotational speed of the engine, and the requested torque of the engine is controlled. I can do it.
Further, according to an embodiment of the present invention, the control unit can reduce the torque feedback correction amount of the engine at a predetermined rate at least when the requested torque control of the engine ends.
According to an embodiment of the present invention, the predetermined determination threshold may be an output value corresponding to a maximum torque error including a friction torque error of the output shaft of the engine.

According to an embodiment of the present invention, when the total value of the required output of the engine and the maximum power output of the generator is smaller than a predetermined determination threshold, the required engine torque is controlled by the engine torque feedback correction amount. For example, even when the battery is in a low output state at low temperatures, it is advantageous to maintain the engine rotation speed and prevent engine stalling without depending on the driver's operation.
Further, according to an embodiment of the present invention, a predetermined determination threshold value is set in advance depending on the engine water temperature for each target rotational speed of the engine, thereby enabling fast and accurate determination processing and preventing engine stalling. This is advantageous in preventing accidents in advance and reliably.
Further, according to an embodiment of the present invention, it is determined whether the total value of the required output of the engine and the maximum powering output of the generator is smaller than a value obtained by adding a hysteresis setting value to a predetermined determination threshold. Since the engine required torque is controlled, it is possible to prevent control hunting due to an increase or decrease in power consumption depending on whether the auxiliary equipment of the hybrid vehicle is turned on or off.
Further, according to an embodiment of the present invention, the torque feedback correction amount is gradually reduced at least at the end of the engine request torque control, which is advantageous in that vibrations in the vehicle and discomfort felt by the driver can be alleviated.
Further, according to an embodiment of the present invention, by setting the predetermined determination threshold to an output value corresponding to the maximum torque error including the friction torque error of the output shaft of the engine, torque feedback is performed in consideration of the maximum torque error. This is advantageous in calculating the correction amount and preventing engine stalling.

5 is a time chart showing changes in engine required torque, rotational speed, and generator torque when battery output decreases in a hybrid vehicle according to the background art. FIG. 1 is a block diagram showing a schematic configuration of a control system in a hybrid vehicle according to an embodiment of the present invention. It is a graph which shows an example of the time change of the water temperature of an engine, oil temperature, and those temperature differences. FIG. 2 is a schematic block diagram showing the flow of energy between an engine, a generator, and a battery in a hybrid vehicle. FIG. 3 is a schematic diagram for explaining a determination threshold used for control according to the present embodiment. 3 is a flowchart showing a control method according to the present embodiment. 5 is a time chart showing an example of the operation of the control device according to the present embodiment.

1. Vehicle Configuration As illustrated in FIG. 2, in a hybrid vehicle 10 according to an embodiment of the present invention, a battery 100 is connected to inverters 101, 102, and 103, and each inverter is connected to a front motor 104, a rear motor 105, and a generator 106. It is connected. Inverters 101 and 102 convert DC power supplied from battery 100 into three-phase AC power and supply it to front motor 104 and rear motor 105, respectively.

The inverter 103 converts the three-phase AC power generated by the generator 106 into DC power, and is used to charge the battery 100 and as a power source for auxiliary equipment (not shown). Note that during regenerative braking of the hybrid vehicle 10, the front motor 104 and the rear motor 105 function as generators, and the three-phase AC power generated by each motor is converted to DC power by the inverters 101 and 102, and the battery 100 is charged. used for.

The rotor shaft of the generator 106 is mechanically connected to the output shaft of the engine 107, and the rotation of the engine 107 generates electricity. Here, the rotational speeds of the engine 107 and the generator 106 are the same. The generator 106 also operates as a motor. Specifically, it can be operated as a starter for starting the engine 107, or the engine 107 can be rotated as a load and used for waste electricity.

Note that if the hybrid vehicle 10 is a plug-in type (PHEV: plug-in hybrid capable of external charging), the battery 100 is connected to a household commercial power source or a quick charging power source at a charging station via a charging device (not shown). The battery may be charged by power supplied from a power source, etc.

Clutch CL mechanically disconnects or connects transmission of rotational torque of engine 107 to gear mechanism 108 . By disengaging the clutch CL, the output shaft of the engine 107 is mechanically connected only to the generator 106, and the hybrid vehicle 10 enters the EV driving mode or the series driving mode. By connecting the clutch CL, the output shaft of the engine 107 is connected not only to the generator 106 but also to the gear mechanism 108. The gear mechanism 108 transmits the driving torque of the front motor 104 to the front wheels 109, and can also transmit the driving torque of the engine 107 to the front wheels 109 if the clutch CL is in a connected state. Further, the rear motor 105 transmits drive torque to the rear wheels 111 via the gear mechanism 110.

Electronic control unit (ECU) 112 constitutes a control section of hybrid vehicle 10. Specifically, the required vehicle output necessary for running the hybrid vehicle 10 is calculated based on various detected amounts and various operating information, and the driving mode (EV mode, series mode ), and also executes output control of the engine 107, output control of the front motor 104 and rear motor 105, output control of the generator 106, etc.

Note that the driving modes of the hybrid vehicle 10 are as follows.
- In the EV mode, the clutch CL is disconnected, the engine 107 is stopped, and the front motor 104 and the rear motor 105 are driven by electric power supplied from the battery 100 to drive the vehicle. If the power supplied from the battery 100 is insufficient for the required output, the engine 107 is started by switching to the series mode described below, and the power generated by the generator 106 is also used to drive the front motor 104 and rear motor 105. use
- In the series mode, the clutch CL is disconnected and all the driving force of the engine 107 is applied to the generator 106. The electric power generated by the generator 106 drives the front motor 104 and the rear motor 105 to cause the vehicle to travel. At this time, if the power generated by the generator 106 is insufficient for the required output, the power stored in the battery 100 is also used to drive the front motor 104 and the rear motor 105. Furthermore, when the power generated by the generator 106 is larger than the required output, the surplus power is used to charge the battery 100.

Furthermore, the ECU 112 executes engine torque control according to the present embodiment by inputting judgment thresholds stored in a judgment threshold table 113 to be described later and the following sensor signals: - The operation amount and operation of the accelerator pedal operated by the driver. An accelerator opening signal from an accelerator position sensor (not shown) that detects the speed;・An engine rotational speed signal from a rotational speed sensor (not shown) that detects the rotational speed [rpm] of the output shaft of the engine 107;・An engine water temperature signal from a water temperature sensor (not shown) that detects the temperature of the cooling water of the engine 107; and an SOC (State Of Charge) sensor (not shown) that detects the remaining battery level and charging state of the battery 100. SOC signal.

Note that the ECU 112 includes a processor such as a CPU (Central Processing Unit), a ROM (Read-only memory) that stores a control program executed by the processor, a RAM (Random access memory) as an operating area for the control program, peripheral circuits, etc. It consists of an interface section with the The determination threshold table 113 may be stored in an erasable and rewritable ROM. The control method according to this embodiment can be implemented by executing a program on the processor of the ECU 112. Hereinafter, after explaining the torque error between the engine and the generator, the control method according to this embodiment will be explained in detail.

2. Calculation of Torque Error As mentioned above, when the battery output decreases at low temperatures or when the battery deteriorates and the power running assist from the generator is lost, the torque error will cause the engine rotational speed to decrease unless the driver increases the required engine output. may not be able to maintain the target value. This torque error occurs due to a discrepancy between the engine water temperature and oil temperature, as described below.

As shown in FIG. 3, the engine water temperature (ENG water temperature) and oil temperature (ENG oil temperature) have different temperature increase rates, so the temperature difference changes with time. Particularly in situations where the engine is started and stopped repeatedly in a short period of time, the discrepancy between the water temperature and oil temperature tends to increase. Friction torque caused by friction acting on the output shaft of the engine is determined by oil temperature and engine rotational speed, and the lower the oil temperature, the larger the friction torque value. When the oil temperature is estimated from the water temperature, if the difference between the water temperature and the oil temperature becomes large, an error will occur in the friction torque value calculated from the actual friction torque value and the water temperature. The maximum torque error amount is calculated by adding the error with respect to the engine command and the friction torque of the reduction gear connected to the engine. Therefore, control is required to increase the required engine output so as to prevent the engine rotational speed from decreasing due to this maximum torque error amount.

3. Engine Torque Control As shown in FIG. 4A, during regenerative operation, the rotational torque of the engine 107 is transmitted to the generator 106, and the generator 106 generates electricity to charge the battery 100. Further, during power operation, power is supplied from the battery 100 to the generator 106, and the generator 106 rotates the engine 107 as a motor. For example, when the rotational speed of the engine 107 falls below the target value, the ECU 112 can maintain the rotational speed of the engine 107 near the target value by controlling the generator 106 to operate as a motor. However, if the battery 100 is in a reduced output state, the powering output of the generator 106 cannot be increased sufficiently. In other words, the possible power output value of the generator 106 corresponds to the possible output value of the battery 100.

As shown in FIG. 4B, in order to prevent the rotational speed of the engine 107 from decreasing due to the torque error, the total value of the required output P _ENG-RQ of the engine 107 and the maximum powering output P _GEN-DRV of the generator 106 is determined by the torque error. It is necessary to do the above. Therefore, the total value of the engine required output P _ENG-RQ and the generator powering maximum output P _GEN-DRV that does not reduce the rotational speed of the engine 107 when the maximum torque error occurs is set as the determination threshold P _TH .

The determination threshold _PTH is set in advance for each target rotational speed of the engine 107 depending on the engine water temperature, and may be stored in a table format in the determination threshold table 113 within the ECU 112 or in a separate storage device. By storing a plurality of assumed judgment thresholds P _TH in the judgment threshold table 113, the ECU 112 can quickly obtain the judgment threshold P _TH required for accurate judgment from sensor data of the engine's target rotational speed and water temperature. . Note that the units of the engine required output P _ENG-RQ , the generator power running maximum output P _GEN-DRV , and the determination threshold P _TH are power [kW], and the engine required output P _ENG-RQ is the engine required power generation output.

Preferably, the determination is made by adding the hysteresis setting value ΔH to the determination threshold _PTH . The purpose of adding the hysteresis setting value ΔH is to absorb fluctuations due to power consumption in auxiliary equipment (such as an air conditioner) in the vehicle 10. That is, since the power consumption of the auxiliary equipment is included in the normal engine required output value, the power consumption varies depending on whether the auxiliary equipment is turned on or off. Therefore, each time the auxiliary equipment is turned on and off, the total value of the engine required output P _ENG-RQ and the generator power running maximum output P _GEN-DRV exceeds or falls below the determination threshold value P _TH , and hunting occurs in the control. The purpose of adding the hysteresis set value ΔH is to prevent control hunting.

As described below, if the total value of the engine required output P _ENG-RQ and the generator powering maximum output P _GEN-DRV is less than the determination threshold P _TH , the ECU 112 determines the difference between the engine rotation speed and the target rotation speed. The engine torque correction amount is fed back (F/B) according to the deviation, and the engine torque is controlled so as to follow the engine target rotation speed.

As shown in FIG. 5, the ECU 112 determines whether the current driving mode is the series mode (step 201), and if it is the series mode (YES in step 201), the ECU 112 sets the target rotational speed of the engine and the engine water temperature. The determination threshold P _TH is obtained from the determination threshold table 113 by inputting the input, and it is determined whether the sum of the current engine required output P _ENG-RQ and the generator power running maximum output P _GEN-DRV is smaller than the determination threshold P _TH . A judgment is made (step 202).

If the total value of the current required engine output P _ENG-RQ and the maximum generator power output P _GEN-DRV is smaller than the determination threshold P _TH (YES in step 202), the torque error causes the engine 107 to The rotation speed may drop and the engine may stall. Therefore, the ECU 112 calculates an engine torque F/B correction amount according to the difference between the current engine rotation speed and the target rotation speed to avoid engine stalling, and controls the engine 107 according to the calculated engine torque F/B correction amount. Control the torque (step 203). At this time, it is desirable to moderate the variation in engine torque due to the engine torque F/B correction amount. For example, instead of increasing the engine torque rapidly at the start of F/B correction, a predetermined increase rate can be set to reduce vibrations in the vehicle 10 and the driver's discomfort.

Note that the engine torque F/B correction amount is calculated by PI (Proportional-Integral) control consisting of an integral term and a proportional term, as will be described later. Integral correction alone causes rotational speed hunting, so proportional correction is added to stabilize control. Note that the unit of the engine torque F/B correction amount is [Nm].

Next, the ECU 112 determines whether the total value of the controlled engine request output P _ENG-RQ and the generator powering maximum output P _GEN-DRV is smaller than the sum of the determination threshold P _TH and the hysteresis setting term ΔH. A judgment is made (step 204). If P _ENG-RQ +P _GEN-DRV <P _TH +ΔH (YES in step 204), the ECU 112 repeats the engine torque F/B correction control (step 203).

If P _ENG-RQ +P _GEN-DRV becomes greater than or equal to P _TH +ΔH (NO in step 204), the ECU 211 ends the engine torque correction control, but at this time, the engine torque fluctuation due to the engine torque F/B correction amount is A tailing process is executed to soften the curve (step 205). By setting a predetermined reduction rate instead of suddenly creating an illusion at the end of the engine torque F/B correction, it is possible to reduce the vibration of the vehicle 10 and the driver's discomfort. At this point, it is considered that there is little possibility that the engine 107 will stall, so the rate of decrease in the engine torque F/B correction amount can be made smaller than the rate of increase in the engine torque F/B correction amount in step 203, further reducing the vibration of the vehicle 10 and the driver's discomfort. can.

If P _ENG-RQ + P _GEN-DRV is greater than or equal to P _TH in step 202 (NO in step 202), or if the tailing process (step 205) is completed, the ECU 112 executes control during normal series mode driving. (Step 206), if the running mode is other than the series mode (NO in step 201), the control according to this embodiment is ended and normal control is continued.

4. Operation Next, the operation of the hybrid vehicle 10 according to this embodiment will be described in detail with reference to FIG.

First, as shown in (B) and (C) of FIG. 6, the ECU 112 inputs the engine required output P _ENG-RQ , the generator power running maximum output P _GEN-DRV , the engine rotation speed, and the engine water temperature, and sets the determination threshold. It is assumed that P _TH is determined and it is determined that P _ENG-RQ +P _GEN-DRV <P _TH +ΔH, that is, the powering output of the generator 106 is insufficient.

As shown in FIG. 6A, it is assumed that the engine 107 is started at time t1 during EV travel in a state where the power running output of the generator 106 is insufficient, and the series travel is started at time t2. When the engine is started, as shown in FIGS. 6(F) and 6(G), the engine begins to rotate due to the power running of the generator 106 and reaches the target rotational speed.

When shifting to series running at time t2, the ECU 112 calculates the proportional correction amount shown in (d1) in FIG. 6 while referring to the deviation between the rotational speed of the engine 107 and the target rotational speed as shown in (F) in FIG. (engine torque F/B correction amount (P term) [Nm]) and the integral correction amount (engine torque F/B correction amount (I term) [Nm]) shown in (d2) of Fig. 6, and Calculate the required engine torque F/B correction amount shown in (D) in FIG. 6 by multiplying the sum of the correction amount and the integral correction amount by the switching coefficient ((d3) in FIG. 6) using the rising rate of increase. do.

The required engine torque F/B correction amount shows a negative value because the engine rotation speed slightly overshoots the target rotation speed after time t2 ((F) in FIG. 6), but after that it increases as shown in curve 301. positive values are maintained. As a result, as shown in FIG. 6(E), the engine required torque increases and is maintained in the increased state, and the actual torque 302 follows it.

As the engine required torque increases, as shown in FIG. This prevents the engine from stalling 402.

As the above _- described series running continues, and as shown in ( _B ) and (C) of _FIG . is determined to have recovered, and the switching coefficient 304 is gradually decreased from time t3 to time t4, as shown in (d3) of FIG. Along with this, as shown in FIG. 6(D), the required engine torque F/B correction amount also starts to decrease from time t3 and becomes zero at time t4.

As the required engine torque F/B correction amount becomes zero, the value of the engine required torque at that time is maintained thereafter as shown in (E) of FIG. 6, and thereby, as shown in (F) of FIG. The engine rotational speed is also maintained as shown. Further, as shown in FIG. 6(G), the power running output of the generator 106 has been restored after time t3, so that the generator 106 can operate as a generator or a motor as required.

Note that the time chart illustrated in FIG. 6 shows a case where the driver runs a series without increasing the output by operating the accelerator, and the control according to this embodiment is not applicable when the driver increases the required engine output. It becomes operational. That is, the control according to this embodiment is applied when the hybrid vehicle 10 is stopped or running at low output.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that those skilled in the art can come up with various changes or modifications within the scope of the claims, and these naturally fall within the technical scope of the present invention. Understood. Further, each of the constituent elements in the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

Note that this application is based on a Japanese patent application (Japanese Patent Application No. 2021-123380) filed on July 28, 2021, the contents of which are incorporated as a reference in this application.

10 Hybrid vehicle 100 Batteries 101, 102, 103 Inverter 104 Front motor 105 Rear motor 106 Generator 107 Engine 108 Gear mechanism 109 Front wheel 110 Gear mechanism 111 Rear wheel 112 Electronic control unit (ECU)

Claims (10)

an engine, a generator mechanically connected to the output shaft of the engine and capable of regenerative or powering operation, and a battery that stores electric power generated during the regenerative operation of the generator and supplies electric power during the powering operation of the generator. A hybrid vehicle comprising: a motor that converts electric power supplied from the battery into driving force for driving wheels; and a control unit that controls the engine, the generator, and the motor,
The control section,
When starting the engine , determine whether the total value of the required output of the engine, which is set to a predetermined value when the accelerator is not operated , and the maximum powering output of the generator is smaller than a predetermined determination threshold. judge,
If the total value is smaller than the predetermined determination threshold, a torque feedback correction amount for the engine is calculated according to the deviation from the target rotational speed of the engine , and the required torque of the engine is increased to reach the target rotational speed. maintain ,
A hybrid vehicle characterized by: The hybrid vehicle according to claim 1, wherein the case where the total value is smaller than the predetermined determination threshold means that the maximum power output of the generator is insufficient. 2. The hybrid vehicle according to claim 1, wherein the predetermined determination threshold is preset for each target rotational speed of the engine depending on a cooling water temperature of the engine. The control unit further includes:
Determining whether the total value is smaller than a value obtained by adding a hysteresis setting value to the predetermined determination threshold,
If the total value is smaller than the predetermined determination threshold plus the hysteresis setting value, a torque feedback correction amount for the engine is calculated according to the deviation from the target rotational speed of the engine, and the required torque of the engine is calculated. control,
The hybrid vehicle according to claim 1, characterized in that: The control unit further includes:
Determining whether the total value is smaller than a value obtained by adding a hysteresis setting value to the predetermined determination threshold,
If the total value is smaller than the predetermined determination threshold plus the hysteresis setting value, a torque feedback correction amount for the engine is calculated according to the deviation from the target rotational speed of the engine, and the required torque of the engine is calculated. control,
The hybrid vehicle according to claim 3 , characterized in that: The hybrid vehicle according to claim 1, wherein the control unit reduces the torque feedback correction amount of the engine at a predetermined rate at least when the request torque control of the engine ends. 4. The hybrid vehicle according to claim 3 , wherein the control unit reduces the torque feedback correction amount of the engine at a predetermined rate at least when the request torque control of the engine ends. 5. The hybrid vehicle according to claim 4 , wherein the control unit reduces the torque feedback correction amount of the engine at a predetermined rate at least when the request torque control of the engine ends. 6. The hybrid vehicle according to claim 5 , wherein the control unit reduces the torque feedback correction amount of the engine at a predetermined rate at least when the request torque control of the engine ends. 10. The hybrid vehicle according to claim 1, wherein the predetermined determination threshold is an output value corresponding to a maximum torque error including a friction torque error of the output shaft of the engine.

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