Control system for hybrid vehicles

Abstract

This design minimizes the deterioration of both emissions and drivability when switching between driving modes. [Solution] The control device 20 of a hybrid vehicle equipped with two types of drive sources, a motor 11 and an engine 10, includes a switching process that switches between an EV mode in which the vehicle runs using only the output of the motor 11 and an HV mode in which the output of the engine 10 can be used as driving power; a setting process that sets an upper limit value for driving power so that it is a smaller value in EV mode than in HV mode; and a holding process that maintains the upper limit value for driving power at the value in EV mode for the period from when the switching from EV mode to HV mode is performed by the switching process until the catalytic converter of the engine 10 has finished warming up.

Description

Technical Field

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

Background Art

[0002] As a control device for a hybrid vehicle, there is one that switches between an electric driving mode and a hybrid driving mode according to driving conditions, the state of charge of a battery, and the like. The electric driving mode is a driving mode in which only the power of a motor is used for driving. The hybrid driving mode is a driving mode in which the power of an engine can be used as driving power.

[0003] Conventionally, as a control device for a hybrid vehicle that performs such switching between driving modes, the device described in Patent Document 1 is known. This control device implements output limitation of the engine during a period from the switch from the electric driving mode to the hybrid driving mode until the warm-up of the engine is completed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The maximum driving force, which is the maximum value of the power available for driving, varies depending on the driving mode. In the hybrid driving mode in which the power of both the motor and the engine can be used, the maximum driving force is greater than that in the electric driving mode in which only the power of the motor can be used. Therefore, the driving characteristics of the hybrid vehicle change according to the switching of the driving mode.

[0006] The conventional control device described above limits engine output when switching from electric driving mode to hybrid driving mode while the engine is not warmed up. Even while the output is limited, the engine's power can still be used for driving within the limit, so the maximum driving force is greater than in electric driving mode. Furthermore, when the output limit is released, the maximum driving force increases even more. Therefore, when switching from electric driving mode to hybrid driving mode while the engine is not warmed up, the driving characteristics of the hybrid vehicle change twice. In this case, since the driving characteristics change twice for a single mode switch, the driver may feel uncomfortable. [Means for solving the problem]

[0007] A control device for a hybrid vehicle that solves the above problems is a control device for a hybrid vehicle equipped with two types of drive sources, a motor and an engine, and includes a processing circuit that performs a switching process for switching between an electric driving mode in which the vehicle is driven only by the output of the motor and a hybrid driving mode in which the output of the engine can be used as driving power; a setting process for setting an upper limit value of the driving power to be smaller than that in the hybrid driving mode when the vehicle is in electric driving mode; and a holding process for maintaining the upper limit value of the driving power at the value in the electric driving mode for the period from when the switching process is performed from the electric driving mode to the hybrid driving mode until the engine's catalytic converter warms up. [Effects of the Invention]

[0008] The control device for the above-mentioned hybrid vehicle has the effect of suppressing the deterioration of both emissions and drivability when switching between driving modes. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows the configuration of one embodiment of a control device for a hybrid vehicle. [Figure 2]Figure 1 is a flowchart of the process performed by the control unit to set the upper limit of the requested power. [Figure 3] The following are time charts illustrating a comparative example of a control device that sets the upper limit of requested power without performing a holding process, when switching driving modes: (a) shows the change in battery charge level, (b) shows the change in driving mode, (c) shows the change in driver-requested power, (d) shows the change in motor-requested output, (e) shows the change in engine-requested output, and (f) shows the change in catalyst temperature. [Figure 4] Figure 1 is a time chart showing the following changes when the control device switches between driving modes: (a) shows the change in battery charge level, (b) shows the change in driving mode, (c) shows the change in driver-requested power, (d) shows the change in motor-requested output, (e) shows the change in engine-requested output, and (f) shows the change in catalyst temperature. [Modes for carrying out the invention]

[0010] Below, one embodiment of a control device for a hybrid vehicle will be described in detail with reference to Figures 1 to 4. <Configuration of the control system for hybrid vehicles> First, the configuration of this embodiment will be described with reference to Figure 1. The hybrid vehicle employing the control device 20 of this embodiment is equipped with two types of drive sources, an engine 10 and a motor 11, as drive sources for driving. The motor 11 generates power by being supplied with power from the battery 12. The motor 11 and the battery 12 are electrically connected via an inverter 13. The inverter 13 adjusts the power that the battery 12 supplies to the motor 11. The hybrid vehicle of this embodiment is configured as a plug-in type hybrid vehicle in which the battery 12 can be charged externally. Various sensors are installed on the engine 10, motor 11, and battery 12 to detect their respective states.

[0011] The control device 20 comprises a processing circuit 21, a storage device 22, and an I / O module 23. The storage device 22 stores programs and data used for vehicle control. The processing circuit 21 performs various processes for vehicle control by executing programs read from the storage device 22. The processing circuit 21 is connected to the engine 10, motor 11, battery 12, and inverter 13 via the I / O module 23. The processing circuit 21 acquires detection results from the engine 10, motor 11, and battery 12, as well as from various sensors installed in them. For example, the processing circuit 21 acquires detection results such as intake air volume, engine rotational speed NE, and engine water temperature from the engine 10. The processing circuit 21 also acquires detection results such as motor rotational speed NMG and motor torque from the motor 11, and detection results such as charge level (SOC) and battery temperature from the battery 12. Furthermore, sensors installed in parts of the hybrid vehicle other than the engine 10, motor 11, and battery 12, such as the accelerator pedal sensor 24, are also connected to the I / O module 23. The accelerator pedal sensor 24 is a sensor that detects the accelerator opening degree (ACCP), which is the amount the driver operates the accelerator pedal. The processing circuit 21 also acquires the detection results from these sensors.

[0012] The processing circuit 21 controls the output of the engine 10 and motor 11 based on the detection results of these sensors. Specifically, the processing circuit 21 controls the output of the engine 10 by manipulating the throttle opening, fuel injection amount, ignition timing, etc. The processing circuit 21 also controls the output of the motor 11 by operating the inverter 13 to adjust the power supplied to the motor 11 by the battery 12.

[0013] <Driving mode switching process> The hybrid vehicle employing the control device 20 of this embodiment has two driving modes: an electric driving mode and a hybrid driving mode. The electric driving mode is a driving mode in which the vehicle is driven solely by the output of the motor 11, while the hybrid driving mode is a driving mode in which the output of the engine 10 can be used as the power source for driving. The processing circuit 21 stops the engine 10 when the vehicle is in electric driving mode. In addition, when the vehicle is in hybrid driving mode, the processing circuit 21 automatically stops and restarts the engine 10 according to the driving conditions of the hybrid vehicle and the charge level (SOC) of the battery 12. In the following description, the electric driving mode will be referred to as EV mode. In the following description, the hybrid driving mode will be referred to as HV mode.

[0014] The processing circuit 21 determines the driving mode based on the operation status of the EV switch 25 installed in the hybrid vehicle, the charge level (SOC) of the battery 12, etc. The EV switch 25 is a switch operated by the driver to select the driving mode. The processing circuit 21 selects the EV mode when the EV switch 25 is ON and the charge level (SOC) of the battery 12 is equal to or greater than the predetermined EV driving permission judgment value S0. The processing circuit 21 also selects the HV mode when the EV switch 25 is OFF or the charge level (SOC) of the battery 12 is less than the EV driving permission judgment value S0. Therefore, the switching of the driving mode from EV mode to HV mode occurs in either of the following situations 1 or 2. Situation 1 is when the driver turns the EV switch 25 OFF. Situation 2 is when the charge level (SOC) of the battery 12 falls below the EV driving permission judgment value S0. Situation 2 occurs due to the driver's operation, whereas Situation 1 occurs regardless of the driver's operation. In the following explanation, switching the driving mode in situation 1 will be described as manual switching, and switching the driving mode in situation 2 will be described as automatic switching.

[0015] <Setting the upper limit of power requirements> While the hybrid vehicle is in operation, the processing circuit 21 calculates the driver-requested power PW*, which is the required driving force of the hybrid vehicle, based on the accelerator opening degree ACCP, etc. When calculating the driver-requested power PW*, the processing circuit 21 performs an upper limit guard on the driver-requested power PW* so that it is less than or equal to the upper limit of the required power PWLM. Next, the processing circuit 21 sets the engine-requested output PE, which is the required output to be generated by the engine 10, and the motor-requested output PMG, which is the required output to be generated by the motor 11, so that their sum is equal to the driver-requested power PW*. Then, the processing circuit 21 controls the output of the engine 10 according to the engine-requested output PE and controls the output of the motor 11 according to the motor-requested output PMG. Note that in EV mode, the processing circuit 21 sets the value of the engine-requested output PE to "0".

[0016] Figure 2 shows a flowchart of the process performed by the processing circuit 21 to set the upper limit requested power PWLM. While the hybrid vehicle is running, the processing circuit 21 repeatedly performs the process shown in Figure 2 at predetermined control cycles.

[0017] When this process is started, the processing circuit 21 first calculates the maximum motor output PMGMX in step S100. The maximum motor output PMGMX represents the upper limit of the motor output. In this embodiment, the processing circuit 21 calculates the maximum motor output PMGMX based on the battery discharge amount WOUT. The battery discharge amount WOUT represents the upper limit of the power that the battery 12 can supply to the motor 11. In this embodiment, the processing circuit 21 determines the battery discharge amount WOUT based on the charge level (SOC) and temperature of the battery 12.

[0018] In the subsequent step S105, the processing circuit 21 determines whether the current driving mode is the EV mode. Then, when the processing circuit 21 determines that the current driving mode is the EV mode (YES), it proceeds to step S110, and when it determines that the current driving mode is not the EV mode (NO), it proceeds to step S115. In the case of this embodiment, the HV mode is set as the driving mode of the hybrid vehicle when the processing circuit 21 makes a negative determination in step S105.

[0019] In step S110, the processing circuit 21 sets the value of the maximum motor output PMGMX calculated in step S100 as the value of the upper limit required power PWLM. Then, after the processing of step S110, the processing circuit 21 ends the processing of FIG. 2 in the current control cycle.

[0020] On the other hand, in step S115, the processing circuit 21 determines whether the switching of the driving mode to the currently set HV mode was a manual switch. Then, when the processing circuit 21 determines that it was a manual switch (YES), it proceeds to step S125, and when it determines that it was not a manual switch, that is, it was an automatic switch (NO), it proceeds to step S120.

[0021] In step S120, the processing circuit 21 determines whether the catalyst warm-up of the engine 10 is completed. In the case of this embodiment, the processing circuit 21 determines that the catalyst warm-up is completed when the catalyst temperature of the engine 10 has risen above the activation temperature of the catalyst. Then, when the processing circuit 21 determines that the catalyst warm-up is completed (YES), it proceeds to step S125, and when it determines that the catalyst warm-up is not completed (NO), it proceeds to step S110.

[0022] In step S125, the processing circuit 21 adds the maximum motor output PMGMX and the maximum engine output PEMX, and sets the sum of these values ​​as the upper limit requested power PWLM. The maximum engine output PEMX represents the upper limit of the output that the engine 10 can generate. After processing in step S125, the processing circuit 21 completes the processing shown in Figure 2 for the current control cycle.

[0023] <Operation of the Embodiment> The processing circuit 21 performs a switching process to switch between EV mode, in which the vehicle runs solely on the output of the motor 11, and HV mode, in which the output of the engine 10 can be used as a power source in addition to the motor 11. Switching from EV mode to HV mode through the switching process can be done manually, in response to the driver's manual operation, or automatically, without manual operation. For example, automatic switching is performed when the state of charge (SOC) of the battery 12 that supplies power to the motor 11 falls below a predetermined value (EV driving permission determination value S0).

[0024] Furthermore, the processing circuit 21 performs a setting process to set the upper limit of the requested power PWLM, which is the upper limit of the power used for driving. In the setting process, the processing circuit 21 basically sets the value of the requested power PWLM to be smaller in EV mode than in HV mode. Specifically, in EV mode, the processing circuit 21 sets the maximum motor output PMGMX, which is the maximum output that the motor 11 can generate, as the value of the requested power PWLM (S110 in Figure 2). In HV mode, the processing circuit 21 sets the sum of the maximum motor output PMGMX and the maximum engine output PEMX, which is the maximum output that the engine 10 can generate, as the value of the requested power PWLM (S125 in Figure 2).

[0025] However, even in HV mode, if both of the following requirements (1) and (2) are met, the processing circuit 21 sets the maximum motor output PMGMX as the value of the upper limit required power PWLM, just as in EV mode. Requirement (1) is that the catalyst of the engine 10 has not finished warming up (S120:NO in Figure 2). Requirement (2) is that the switch to the current HV mode was an automatic switch (S115:NO in Figure 2). In this way, the processing circuit 21 performs a holding process to maintain the value of the upper limit required power PWLM at the value used in EV mode during the period from when the automatic switch from EV mode to HV driving mode is performed until the catalyst of the engine 10 has finished warming up. This holding process is performed with the aim of suppressing the deterioration of both emissions and drivability when switching driving modes.

[0026] Figure 3 shows an example of the control behavior of a hybrid vehicle during driving mode switching when the upper limit requested power PWLM is set without holding processing. Figure 3(a) shows the change in the charge rate (SOC) of the battery 12, Figure 3(b) shows the change in the driving mode, and Figure 3(c) shows the change in the driver requested power PW*. Figure 3(d) shows the change in the motor requested output (PMG), Figure 3(e) shows the change in the engine requested output (PE), and Figure 3(f) shows the change in the catalyst temperature. In Figure 3(c), the change in the value of the driver requested power PW* before the application of the upper limit guard by the upper limit requested power PWLM is shown by a dashed line, and the change in the value of the driver requested power PW* after the application is shown by a solid line.

[0027] In the case of Figure 3, at time t1 while driving in EV mode, the charge level (SOC) of the battery 12 drops below the EV driving permission threshold S0, and an automatic switch to HV mode is performed. Then, at this time t1, the processing circuit 21 starts the engine 10.

[0028] At time t1, the driver requested power PW* is a value exceeding the maximum motor output PMGMX before the upper limit guard is applied. As mentioned above, in EV mode, the maximum motor output PMGMX is set as the value of the upper limit requested power PWLM. Therefore, the final driver requested power PW* after the upper limit guard is applied is set to a value equal to the maximum motor output PMGMX. In the case of Figure 3, even after time t1, the value of the driver requested power PW* before the upper limit guard is applied is maintained at the value at time t1.

[0029] If the hold process is not performed, at time t1, the value of the upper limit requested power PWLM is switched from the value for EV mode to the value for HV mode. Therefore, if the hold process is not performed, the engine 10 may be operated at a high output immediately after starting. In the case of Figure 3, at time t1 when the engine 10 is started in response to the switch to HV mode, the catalyst temperature is below the activation temperature. Therefore, the engine 10 is in a state where it cannot adequately purify the exhaust until the catalyst temperature reaches the activation temperature at the subsequent time t2 and the catalyst warm-up is completed. Thus, if the hold process is not performed, the engine 10 may be operated at a high output while the catalyst warm-up is incomplete, which may worsen emissions when switching driving modes.

[0030] Figure 4 shows an example of the control behavior of a hybrid vehicle during driving mode switching in this embodiment. Figure 4(a) shows the change in the State of Charge (SOC) of the battery 12, Figure 4(b) shows the change in the driving mode, and Figure 4(c) shows the change in the driver-requested power (PW*). Figure 4(d) shows the change in the motor-requested output (PMG), Figure 4(e) shows the change in the engine-requested output (PE), and Figure 4(f) shows the change in the catalyst temperature. In Figure 4(c), the change in the value of the driver-requested power (PW*) before the application of the upper limit guard by the upper limit-requested power (PWLM) is shown by a dashed line, and the change in the value of the driver-requested power (PW*) after the application is shown by a solid line.

[0031] In the case of Figure 4, as in the case of Figure 3, at time t10 while driving in EV mode, the charge level (SOC) of the battery 12 drops below the EV driving permission judgment value S0, and an automatic switch to HV mode is performed. Then, the processing circuit 21 starts the engine 10 at this time t10. In the case of Figure 4, as well, the driver-requested power PW* at time t10 and thereafter exceeds the maximum motor output PMGMX before the upper limit guard is applied.

[0032] In this embodiment, even after switching to HV mode, the upper limit requested power PWLM is maintained at the value from EV mode until the catalyst temperature reaches or exceeds the activation temperature at time t11 and the catalyst warm-up of the engine 10 is completed. More specifically, during the period from the start of the engine 10 due to switching to HV mode until the catalyst warm-up is completed, the driver requested power PW* is maintained at or below the maximum motor output PMGMX. Therefore, the output of the engine 10 is suppressed until the catalyst warm-up is completed. Even if the catalyst warm-up is not complete, if the engine 10 is at low output, the exhaust flow rate is low, so the deterioration of emissions is limited. Moreover, in this case, the upper limit requested power PWLM is maintained at the value from EV mode until the catalyst warm-up is completed, so the change in the driving characteristics of the hybrid vehicle due to the change in the upper limit requested power PWLM occurs only when the catalyst warm-up is completed.

[0033] Furthermore, the driver can manually switch to HV mode when a greater driving force is required that cannot be generated in EV mode. In response to this, the processing circuit 21 is configured to perform a hold process only in the case of automatic switching. Therefore, in the case of manual switching, the value of the upper limit requested power PWLM is changed from the value in EV mode to the value in HV mode, along with the switch from EV mode to HV mode. As a result, in this case, the driving force of the hybrid vehicle can be quickly increased in response to the driver's request.

[0034] <Effects of the Embodiment> The control device 20 of the hybrid vehicle in this embodiment provides the following effects. (1) The control device 20 of the hybrid vehicle in this embodiment is equipped with a processing circuit 21 that performs the following switching, setting, and holding processes. The switching process is the process of switching between EV mode, in which the vehicle runs using only the output of the motor 11, and HV mode, in which the output of the engine 10 can be used as the power for driving. The setting process is the process of setting the value of the upper limit required power PWLM, which is the upper limit of the power for driving, to a smaller value in EV mode than in HV mode. The holding process is the process of holding the upper limit required power PWLM at the value used in EV mode for the period from when the switching from EV mode to HV mode is performed until the catalyst warm-up of the engine 10 is completed. After switching from EV mode to HV mode, the engine 10 can be operated at low output for the period until the catalyst warm-up of the engine 10 is completed. In addition, the change in driving characteristics due to the change in the upper limit required power PWLM can be limited to only once when the catalyst warm-up is completed. Therefore, deterioration of both emissions and drivability when switching driving modes can be suppressed.

[0035] (2) The processing circuit 21 is configured to perform the holding process only in the case of automatic switching, of which manual switching and automatic switching are available. Therefore, when the driver requests an increase in driving force during manual switching, it is possible to generate the driving force as requested, while when the driver does not request an increase in driving force during automatic switching, the deterioration of emissions is suppressed.

[0036] (3) The processing circuit 21 is configured to perform an automatic switchover during the switching process if the State of Charge (SOC) of the battery 12 that supplies power to the motor 11 falls below a predetermined value. As a result, driving in EV mode can be continued as long as the battery 12 does not become undercharged.

[0037] (4) The processing circuit 21 is configured to set the value of the upper limit required power PWLM in EV mode according to the state of charge (SOC) of the battery 12 that supplies power to the motor 11 during the setting process. In this case, the driver required power PW* during the period in which the upper limit required power PWLM is held at the value for EV mode by the holding process is kept at a value that can be satisfied by the output of the motor 11 alone. Therefore, it is possible to set the output of the engine 10 to an arbitrary value for the period until the catalyst warm-up is complete. Consequently, it is possible to set the output of the engine 10 during the period from switching to HV mode until the catalyst warm-up is complete to a value appropriate for suppressing the deterioration of emissions.

[0038] (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.

[0039] The setting of the upper limit requested power PWLM in the setting process may be carried out in a manner different from that of the above embodiment, as long as the value in EV mode is smaller than the value in HV mode.

[0040] Automatic and manual switching from EV mode to HV mode may be performed under conditions different from those in the above embodiment. For example, the processing circuit 21 may be configured to automatically switch to HV mode when a large driving force exceeding the output limit of the motor 11 is required while driving in EV mode.

[0041] The automatic switching can be configured to have multiple conditions. For example, a configuration can be considered in which automatic switching is performed when either of the following conditions is met: a first condition, which is that a large driving force exceeding the output limit of the motor 11 is requested, or a second condition, which is that the charge level (SOC) of the battery 12 falls below a predetermined value. In such a case, the processing circuit 21 can be configured to perform a hold process only when some of the multiple execution conditions are met. For example, the processing circuit 21 can be configured to perform a hold process when automatic switching is performed due to the fulfillment of the first condition, and not perform a hold process when automatic switching is performed due to the fulfillment of the second condition. When automatic switching is performed due to the fulfillment of the second condition, it is assumed that the driver is requesting a large driving force. Therefore, when the driver requests an increase in driving force, it is possible to generate a driving force that meets the request, while if not, the deterioration of emissions can be suppressed.

[0042] The processing circuit 21 may be configured to perform a holding process even when manually switched. Alternatively, the switching from EV mode to HV mode may be performed by either automatic or manual switching, or only one of the two.

[0043] The above embodiments and their modifications can also be applied to hybrid vehicles with configurations different from those of the above embodiments. <Additional Notes> [Note 1] The control device for a hybrid vehicle according to any one of claims 1 to 3, wherein the processing circuit is configured in the setting process to set an upper limit value of the driving power during the electric driving mode according to the charge level of the battery that supplies power to the motor.

[0044] [Note 2] The control device for a hybrid vehicle according to claim 1 or Note 1, wherein the processing circuit is configured to switch from the electric driving mode to the hybrid driving mode when a first condition is met, in which the charge level of the battery supplying power to the motor falls below a predetermined value, and when a second condition is met, in which case the driver requests the generation of a driving force exceeding a predetermined value, and the holding process is performed only when the first condition is met, of the first and second conditions. [Explanation of symbols]

[0045] 10 Engines 11 Motor 12 batteries 13 Inverter 20 Control device 21 Processing Circuit 22 Storage device 23 I / O Modules 24. Accelerator pedal sensor 25 EV switch

Claims

1. A control device for a hybrid vehicle equipped with two types of drive sources, an electric motor and an engine, A switching process that switches between an electric driving mode in which the vehicle is driven solely by the output of the aforementioned motor, and a hybrid driving mode in which the output of the aforementioned engine can be used as the power source for driving, In the case of the electric driving mode, a setting process is performed to set the upper limit of the driving power to a smaller value than in the case of the hybrid driving mode, During the period from when the switching from the electric driving mode to the hybrid driving mode is performed by the aforementioned switching process until the engine catalyst warm-up is completed, a holding process is performed to maintain the upper limit of the driving power at the value for the electric driving mode, It includes a processing circuit that performs the following actions. Control system for hybrid vehicles.

2. The switching process from the electric driving mode to the hybrid driving mode includes a manual switching method performed in response to the driver's manual operation, and an automatic switching method performed automatically without manual operation. The processing circuit is configured to perform the holding process only in the case of automatic switching, among the manual switching and automatic switching. A control device for a hybrid vehicle according to claim 1.

3. The control device for a hybrid vehicle according to claim 2, wherein the processing circuit is configured to perform the automatic switching when the charge level of the battery supplying power to the motor falls below a predetermined value during the switching process.

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