Control device for hybrid electric vehicle

Abstract

A control device for a hybrid electric vehicle, which is provided with two drive sources, i.e., an electric motor and an engine, is provided with a processing circuit for performing: a switching process for switching between a switching process for switching between a switching process for switching between a switching process for switching between a switching process for switching between a switching process for switching between a switching process and a switching process; an EV mode in which the vehicle is driven only by the output of the electric motor, and an HV mode in which the output of the engine can be used as driving power are switched; a setting process for setting the upper limit value of the driving power so as to be smaller in the EV mode than in the HV mode; and a holding process for holding the upper limit value of the travel power at the value during the EV mode during a period from the execution of the switching from the EV mode to the HV mode by the switching process until the catalyst warm-up of the engine is completed.

Description

Technical Field

[0001] This invention relates to a control device for a hybrid electric vehicle. Background Technology

[0002] As a control device for hybrid electric vehicles, there is a mechanism that switches between electric driving mode and hybrid driving mode based on driving conditions and battery charging status. Electric driving mode is a driving mode that uses only the power of the electric motor for propulsion. Hybrid driving mode is a driving mode that can use the power of the engine for driving.

[0003] Previously, as a control device for switching between electric and hybrid electric vehicles, the device described in Japanese Patent Application Publication No. 2013-133040 is known. This control device implements engine output limitation during the period from switching from electric driving mode to hybrid driving mode until the engine has warmed up. Summary of the Invention

[0004] The maximum driving force, which is the maximum amount of power available for driving, varies depending on the driving mode. In a hybrid driving mode that utilizes the power of both the electric motor and the engine, the maximum driving force is greater than in an electric driving mode that utilizes only the electric motor. Therefore, the driving characteristics of a hybrid electric vehicle change depending on the driving mode.

[0005] The aforementioned conventional control device limits engine output when switching from electric driving mode to hybrid driving mode while the engine is not warmed up. Even with the output limited, engine power can still be used for driving within the limited range, therefore the maximum driving force is greater than in electric driving mode. Then, if the output limit is lifted, the maximum driving force increases further. Therefore, when switching from electric driving mode to hybrid driving mode while the engine is not warmed up, the driving characteristics of the hybrid electric vehicle change twice. In this case, the driving characteristics change twice compared to a single driving mode switch, which may cause discomfort to the driver.

[0006] To address the aforementioned issues, the control device for a hybrid electric vehicle incorporates both an electric motor and an engine as drive sources, and the control device for the hybrid electric vehicle includes a processing circuit that performs the following processing:

[0007] The switching process allows for the switching between an electric driving mode that operates solely on the output of the electric motor and a hybrid driving mode that utilizes the output of the engine for driving power.

[0008] The setting process, in the case of the electric driving mode, sets the upper limit value of the driving power in a manner that is smaller than that in the case of the hybrid driving mode; and

[0009] During the period from the start of the switching process from the electric driving mode to the hybrid driving mode until the engine catalyst warm-up is completed, the upper limit of the driving power is maintained at the value in the electric driving mode.

[0010] The control device for the aforementioned hybrid electric vehicle has the effect of suppressing both emissions and drivability degradation when switching driving modes. Attached Figure Description

[0011] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0012] Figure 1 This is a diagram schematically illustrating the structure of one embodiment of the control device for a hybrid electric vehicle.

[0013] Figure 2 yes Figure 1 The flowchart shows the process performed by the control device to set the upper limit of the requested power.

[0014] Figure 3 This is a time graph showing the switching of driving modes in a comparative example of a control device that sets an upper limit for requested power without performing a hold-up process. Graph (a) shows the change in battery charge rate, graph (b) shows the change in driving mode, and graph (c) shows the change in driver requested power. Furthermore, graph (d) shows the change in electric motor requested output, graph (e) shows the change in engine requested output, and graph (f) shows the change in catalyst temperature.

[0015] Figure 4 yes Figure 1 The time graphs show the timing of driving mode switching implemented by the control device. Graph (a) shows the battery charging rate, graph (b) shows the driving mode, graph (c) shows the driver's requested power, graph (d) shows the electric motor's requested output, graph (e) shows the engine's requested output, and graph (f) shows the catalyst temperature. Detailed Implementation

[0016] Structure of the control device for hybrid electric vehicles

[0017] The following is for reference. Figures 1 to 4 An embodiment of a control device for a hybrid electric vehicle will be described in detail.

[0018] First, refer to Figure 1 The structure of this embodiment will be described. The hybrid electric vehicle using the control device 20 of this embodiment has two drive sources: an engine 10 and an electric motor 11. The electric motor 11 generates power through power supplied from the battery 12. The electric motor 11 and the battery 12 are electrically connected via an inverter 13. The inverter 13 adjusts the power supplied from the battery 12 to the electric motor 11. The hybrid electric vehicle of this embodiment is configured as a plug-in hybrid electric vehicle capable of externally charging the battery 12. Various sensors for detecting their states are respectively provided in the engine 10, the electric motor 11, and the battery 12.

[0019] The control unit 20 includes a processing circuit 21, a storage device 22, and an I / O module 23. The storage device 22 stores programs or data for vehicle control. The processing circuit 21 executes various processes for vehicle control by running programs read from the storage device 22. The processing circuit 21 is connected to the engine 10, the electric motor 11, the battery 12, and the inverter 13 via the I / O module 23. The processing circuit 21 obtains detection results from various sensors installed on the engine 10, the electric motor 11, and the battery 12. For example, the processing circuit 21 obtains detection results from the engine 10 such as intake air volume, engine speed NE, and engine coolant temperature. Furthermore, the processing circuit 21 obtains detection results from the electric motor 11 such as motor speed NMG and motor torque, and from the battery 12 such as charge rate SOC and battery temperature. Moreover, the I / O module 23 is also connected to sensors other than the engine 10, electric motor 11, and battery 12, such as a throttle pedal sensor 24. Accelerator pedal sensor 24 is a sensor that detects the accelerator pedal opening (ACCP) as operated by the driver. Processing circuit 21 also acquires the detection results from these sensors.

[0020] Based on the detection results of these sensors, the processing circuit 21 controls the output of the engine 10 and the electric motor 11. Specifically, the processing circuit 21 controls the output of the engine 10 by operating the throttle opening, fuel injection quantity, ignition timing, etc. Furthermore, the processing circuit 21 controls the output of the electric motor 11 by operating the inverter 13 to adjust the power supplied by the battery 12 to the electric motor 11.

[0021] Driving mode switching

[0022] In the hybrid electric vehicle employing the control device 20 of this embodiment, two driving modes are provided: an electric driving mode and a hybrid driving mode. The electric driving mode is a driving mode that operates solely using the output of the electric motor 11, while the hybrid driving mode is a driving mode that utilizes the output of the engine 10 for driving power. The processing circuit 21 stops the engine 10 in the electric driving mode. Furthermore, in the hybrid driving mode, the processing circuit 21 automatically stops and restarts the engine 10 based on the driving conditions of the hybrid electric vehicle or the state of charge (SOC) of the battery 12. In the following description, the electric driving mode will be referred to as EV mode. And in the following description, the hybrid driving mode will be referred to as HV mode.

[0023] The processing circuit 21 determines the driving mode based on the operation status of the EV switch 25 provided in the hybrid electric vehicle and the state of charge (SOC) of the battery 12. 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 SOC of the battery 12 is above a predetermined EV driving allowable judgment value S0. Furthermore, the processing circuit 21 selects the HV mode when the EV switch 25 is off or the SOC of the battery 12 is below the EV driving allowable judgment value S0. Therefore, the switching of the driving mode from EV mode to HV mode occurs in either of the following situations: Situation 1: The driver operates the EV switch 25 to be off. Situation 2: The SOC of the battery 12 drops below the EV driving allowable judgment value S0. Situation 2 is generated by the driver's operation, while Situation 1 is not dependent on the driver's operation. In the following description, the switching of the driving mode based on Situation 1 is described as manual switching, and the switching of the driving mode based on Situation 2 is described as automatic switching.

[0024] Setting the upper limit of requested power

[0025] During the operation of the hybrid electric vehicle, the processing circuit 21 calculates the driver-requested power PW*, which is the requested value of the driving force of the hybrid electric vehicle, based on the throttle opening (ACCP), etc. When calculating the driver-requested power PW*, the processing circuit 21 performs upper limit protection on the driver-requested power PW*, ensuring it is below the upper limit requested power PWLM. Next, the processing circuit 21 sets the engine-requested output PE and the electric motor-requested output PMG so that their sum equals the driver-requested power PW*. The engine-requested output PE is the requested value of the output generated in the engine 10, and the electric motor-requested output PMG is the requested value of the output generated in the electric motor 11. Furthermore, the processing circuit 21 controls the output of the engine 10 based on the engine-requested output PE, and controls the output of the electric motor 11 based on the electric motor-requested output PMG. Additionally, in EV mode, the processing circuit 21 sets "0" to the value of the engine-requested output PE.

[0026] Figure 2 The diagram shows a flowchart of the processing circuit 21 performing to set the upper limit requested power PWLM. During the operation of the hybrid electric vehicle, the processing circuit 21 repeatedly executes this process according to each predetermined control cycle. Figure 2 The processing.

[0027] If this process begins, the processing circuit 21 first calculates the maximum motor output PMGMX in 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 battery 12's state of charge (SOC) and temperature, etc.

[0028] In the subsequent S105, the processing circuit 21 determines whether the current driving mode is EV mode. Then, if it is determined that the current driving mode is EV mode (yes), the processing circuit 21 proceeds to S110; if it is determined that it is not EV mode (no), the processing circuit 21 proceeds to S115 and performs processing accordingly. In this embodiment, the processing circuit 21 sets the HV mode in the driving mode of the hybrid electric vehicle when the determination is negative in S105.

[0029] In S110, processing circuit 21 sets the value of the maximum motor output PMGMX calculated in S100 to the value of the upper limit requested power PWLM. Then, after processing in S110, processing circuit 21 ends the current control cycle. Figure 2 The processing.

[0030] On the other hand, in S115, the processing circuit 21 determines whether the current setting for switching to the HV mode is a manual switch. Then, if it is determined to be a manual switch (yes), the processing circuit 21 enters S125; if it is determined not to be a manual switch, i.e., it is determined to be an automatic switch (no), the processing circuit 21 enters S120 and performs processing accordingly.

[0031] In S120, the processing circuit 21 determines whether the catalyst warm-up of the engine 10 has been completed. In this embodiment, the processing circuit 21 determines that the catalyst warm-up has been completed if the catalyst temperature of the engine 10 rises above the catalyst's active temperature. Then, if the catalyst warm-up is determined to be completed (yes), the processing circuit 21 proceeds to S125; if it is determined not to be completed (no), the processing circuit 21 proceeds to S110 to perform processing respectively.

[0032] In S125, processing circuit 21 adds the maximum motor output PMGMX to the maximum engine output PEMX and sets the sum as the upper limit requested power PWLM. The maximum engine output PEMX represents the upper limit of the output that engine 10 can produce. Then, after processing in S125, processing circuit 21 ends the current control cycle. Figure 2 The processing.

[0033] The role of the implementation method

[0034] The processing circuit 21 performs switching processing to switch between EV mode, which operates solely on the output of the electric motor 11, and HV mode, which allows the output of the engine 10 to be used for driving power in addition to the electric motor 11. The switching from EV mode to HV mode based on the switching processing can be either manual switching, performed based on the driver's manual operation, or automatic switching, performed automatically without manual operation. For example, automatic switching is performed when the charge rate (SOC) of the battery 12 supplying power to the electric motor 11 is less than a predetermined value (EV driving allowable judgment value S0).

[0035] Furthermore, the processing circuit 21 performs a setting process for the upper limit requested power PWLM, which is set as the upper limit value for driving power. In this setting process, the processing circuit 21 essentially sets the value of the upper limit requested power PWLM in EV mode to be a smaller value than that in HV mode. Specifically, in EV mode, the processing circuit 21 sets the maximum output that the motor 11 can produce, i.e., the maximum motor output PMGMX, as the value of the upper limit requested power PWLM. Figure 2S110). Furthermore, in HV mode, the processing circuit 21 sets the sum of the maximum motor output PMGMX and the maximum output that engine 10 can produce, i.e., the maximum engine output PEMX, to the value of the upper limit requested power PWLM. Figure 2 (S125).

[0036] In HV mode, even if both condition (1) and condition (2) are met, the processing circuit 21 sets the maximum motor output PMGMX to the value of the upper limit requested power PWLM, just as it does in EV mode. Condition (1) is that the catalyst of engine 10 has not been fully warmed up. Figure 2 The requirement of S120: No). Requirement (2) is that the current switch to HV mode is automatic ( Figure 2 The requirement of S115 (No). Thus, the processing circuit 21 performs the following maintenance process: from the time the automatic switch from EV mode to HV driving mode is implemented until the catalyst warm-up of engine 10 is completed, the value of the upper limit requested power PWLM is maintained at the value in EV mode. The purpose of performing this maintenance process is to suppress the deterioration of both emissions and drivability when switching driving modes.

[0037] Figure 3 This illustrates an example of the control method for a hybrid electric vehicle when switching driving modes, where the upper limit request power PWLM is set without holding processing. Figure 3 The graph (a) shows the state of charge (SOC) of battery 12 over time. Figure 3 Chart (b) shows the shift in driving modes. Figure 3 Chart (c) shows the shift in driver-requested power PW*. Furthermore, Figure 3 Chart (d) shows the shift in the motor's requested PMG output. Figure 3 The graph (e) shows the shift in the engine's requested output PE. Figure 3 The graph (f) shows the transition of catalyst temperature. Additionally, in Figure 3 In Figure (c), the shift in the value of the driver's requested power PW* before the application of the upper limit protection of the upper limit requested power PWLM is represented by a double-dotted line, and the shift in the value of the driver's requested power PW* after the application is represented by a solid line.

[0038] exist Figure 3 In the case where the battery 12's charge rate (SOC) drops below the EV driving allowable threshold (S0) at time t1 during EV mode driving, an automatic switch to HV mode is implemented. Then, the processing circuit 21 starts the engine 10 at that time t1.

[0039] At time t1, the driver's requested power PW* exceeds the maximum motor output PMGMX before the upper limit protection applies. As mentioned above, in EV mode, the maximum motor output PMGMX is set to the value of the upper limit requested power PWLM. Therefore, the final driver's requested power PW* after the upper limit protection applies at this time is set to a value equal to the maximum motor output PMGMX. Figure 3 In the case of time t1, the value of the driver's requested power PW* before the application of the upper limit protection remains at the value at time t1.

[0040] Without holding processing, at time t1, the value of the upper limit requested power PWM switches from the value in EV mode to the value in HV mode. Therefore, without holding processing, engine 10 may operate at a higher output immediately after startup. Figure 3 In the case of engine 10 starting at time t1 due to switching to HV mode, the catalyst temperature is lower than the activation temperature. Therefore, before the catalyst temperature reaches the activation temperature and the catalyst warm-up is complete at time t2, engine 10 is in a state where exhaust gas cannot be adequately purified. Thus, without maintenance, engine 10 may operate at higher output while the catalyst warm-up is incomplete, potentially leading to worsened emissions when switching driving modes.

[0041] exist Figure 4 An example of the control method of a hybrid electric vehicle during driving mode switching in this embodiment is shown. Figure 4 The graph (a) shows the state of charge (SOC) of battery 12 over time. Figure 4 Chart (b) shows the shift in driving modes. Figure 4 Chart (c) shows the shift in driver-requested power PW*. Furthermore, Figure 4 Chart (d) shows the shift in the motor's requested PMG output. Figure 4 The graph (e) shows the shift in the engine's requested output PE. Figure 4 The graph (f) shows the transition of catalyst temperature. Additionally, in Figure 4 In Figure (c), the shift in the value of the driver's requested power PW* before the application of the upper limit protection of the upper limit requested power PWLM is represented by a double-dotted line, and the shift in the value of the driver's requested power PW* after the application is represented by a solid line.

[0042] exist Figure 4 In the case of, also with Figure 3Similarly, at time t10 during EV mode driving, if the SOC of battery 12 drops below the EV driving allowable threshold S0, an automatic switch to HV mode is initiated. Then, processing circuit 21 starts engine 10 at that time t10. Figure 4 In the case of time t10 and thereafter, the driver's requested power PW* exceeds the maximum motor output PMGMX before the upper limit protection applies.

[0043] In this embodiment, even after switching to HV mode, the maximum requested power PWLM remains the same as in EV mode until the catalyst temperature reaches above the activation temperature at time t11 and the catalyst warm-up of engine 10 is complete. More specifically, from the start of engine 10 due to switching to HV mode until the catalyst warm-up is complete, the driver requested power PW* remains below the maximum electric motor output PMGMX. Therefore, the output of engine 10 is suppressed until the catalyst warm-up is complete. Even if the catalyst warm-up is not complete, if engine 10 is at low output, the exhaust flow is low, so the deterioration of emissions is limited. Moreover, in this case, the maximum requested power PWLM remains the same as in EV mode until the catalyst warm-up is complete. Therefore, the change in the driving characteristics of the hybrid electric vehicle resulting from the change in the maximum requested power PWLM is limited to the time when the catalyst warm-up is complete.

[0044] Furthermore, if the driver requires greater driving force that cannot be generated in EV mode, they can manually switch to HV mode. In contrast, processing circuit 21 is configured to perform hold processing only during manual and automatic switching. Therefore, in the case of manual switching, the value of the requested power PWM is changed from the value in EV mode to the value in HV mode, along with the switch from EV mode to HV mode. Thus, in this case, the driving force of the hybrid electric vehicle can be rapidly increased according to the driver's request.

[0045] Effects of the implementation method

[0046] The control device 20 for the hybrid electric vehicle in this embodiment has the following effects.

[0047] (1) The control device 20 of the hybrid electric vehicle of this embodiment includes a processing circuit 21 that performs the following switching, setting, and holding processes. The switching process is a process of switching between EV mode, in which the vehicle operates solely on the output of the electric motor 11, and HV mode, in which the output of the engine 10 can be used as driving power. The setting process is a process of setting the value of the upper limit request power PWLM, which is the upper limit value of driving power, to be a smaller value than that in HV mode in EV mode. The holding process is a process of maintaining the upper limit request power PWLM at the value in EV mode from the time of switching from EV mode to HV mode based on the switching process until the catalyst warm-up of the engine 10 is completed. During the period from switching from EV mode to HV mode until the catalyst warm-up of the engine 10 is completed, the engine 10 can maintain low output operation. Furthermore, the change in driving characteristics caused by the change of the upper limit request power PWLM is limited to once when the catalyst warm-up is completed. Therefore, the deterioration of both emissions and drivability during switching driving modes can be suppressed.

[0048] (2) The processing circuit 21 is configured to perform the holding process only in the case of automatic switching between manual and automatic switching. Therefore, when the driver requests a manual switch to increase the driving force, the driving force corresponding to the request can be generated, while in the case of automatic switching, which is not the case, the deterioration of emissions can be suppressed.

[0049] (3) The processing circuit 21 is configured to automatically switch when the state of charge (SOC) of the battery 12 supplying power to the motor 11 is less than a predetermined value during the switching process. Therefore, it is possible to continue driving in EV mode without the battery 12 being undercharged.

[0050] (4) The processing circuit 21 is configured to set the value of the upper limit requested power PWLM in EV mode based on the charge rate (SOC) of the battery 12 supplying power to the motor 11 during the setting process. In this case, the driver requested power PW* is maintained at a value that is satisfied only by the output of the motor 11 during the period when the value of the upper limit requested power PWLM is maintained at the value in EV mode through the holding process. Therefore, the output of the engine 10 during the period until the catalyst warm-up is complete can be set to any value. Therefore, the output of the engine 10 during the period from switching from HV mode to the completion of catalyst warm-up can be set to a value suitable for suppressing emission degradation.

[0051] Other implementation methods

[0052] The above-described embodiments can be implemented in the following ways. The above-described embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0053] Regarding the setting of the upper limit request power PWLM in the setting process, it can be implemented in a different manner than the above implementation method, as long as the value in EV mode is less than the value in HV mode.

[0054] • Automatic and manual switching from EV mode to HV mode can be implemented under conditions different from the above-described implementation. For example, the processing circuit 21 can be configured to automatically switch to HV mode when a large driving force exceeding the output limit of the motor 11 is requested during driving in EV mode.

[0055] • The system can be configured to have multiple conditions as execution conditions for automatic switching. For example, it can be configured to perform automatic switching when either a first condition (requesting a large driving force exceeding the output limit of the motor 11) or a second condition (the state of charge (SOC) of the battery 12 being less than a predetermined value) is met. In this case, the processing circuit 21 can also be configured to perform a holding process only when a portion of the multiple execution conditions are met. For example, the processing circuit 21 can be configured to perform a holding process when automatic switching is performed based on the fulfillment of the first condition, but not when automatic switching is performed based on the fulfillment of the second condition. When automatic switching is performed based on the fulfillment of the second condition, it can be assumed that the driver is requesting a larger driving force. Therefore, when the driver requests an increased driving force, a driving force corresponding to the request can be generated, while when this is not the case, emission degradation can be suppressed.

[0056] • The processing circuit 21 can be configured to perform hold processing even during manual switching. Furthermore, it can be configured to switch from EV mode to HV mode using only either automatic or manual switching.

[0057] Notes

[0058] Postscript 1

[0059] The above-described embodiments and their modifications can also be applied to hybrid electric vehicles with structures different from those described above.

[0060] According to any one of the embodiments 1 to 3, the control device for a hybrid electric vehicle, wherein the processing circuit is configured to set an upper limit value of the driving power in the electric driving mode based on the charging rate of the battery that supplies power to the electric motor during the setting process.

[0061] Appendix 2

[0062] According to the control device for a hybrid electric vehicle as described in Scheme 1 or Appendix 1, the processing circuit is configured to, during the switching process, perform a switch from the electric driving mode to the hybrid driving mode when a first condition is met (the charging rate of the battery supplying power to the electric motor is less than a predetermined value) and a second condition is met (the driver requests to generate a driving force exceeding a predetermined value), and in the first and second conditions, perform the holding process only when the first condition is met.

Claims

1. A control device for a hybrid electric vehicle, comprising two drive sources: an electric motor and an engine, characterized in that it includes a processing circuit for performing the following processing: The switching process allows for the switching between an electric driving mode that operates solely on the output of the electric motor and a hybrid driving mode that utilizes the output of the engine for driving power. The setting process sets the upper limit of the driving power in the case of the electric driving mode in a way that is smaller than that in the case of the hybrid driving mode; and The process maintains the upper limit of the driving power at the value in the electric driving mode until the engine catalyst warm-up is completed from the start of the switching process from the electric driving mode to the hybrid driving mode.

2. The control device for a hybrid electric vehicle according to claim 1, characterized in that, In the switching process from the electric driving mode to the hybrid driving mode, there are manual switching based on the driver's manual operation and automatic switching that is not dependent on the manual operation. The processing circuit is configured to perform the hold processing only in the case of the automatic switch during the manual switch and the automatic switch.

3. The control device for a hybrid electric vehicle according to claim 2, characterized in that, The processing circuit is configured to perform the automatic switching when the charging rate of the battery supplying power to the motor is less than a predetermined value during the switching process.

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