Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle that can prevent delay in start of preheating of an electrically heating catalyst while reducing an arithmetic load.SOLUTION: A control device of a hybrid vehicle includes: a control unit that starts preheating control when the SOC is equal to or less than a start threshold for starting the preheating control of an electrically heating catalyst; a switching unit that switches from a motor travel mode that uses a motor as a power source to a hybrid travel mode that uses at least an engine as a power source when the SOC is equal to or less than a switching threshold which is less than the start threshold; and a calculation unit that calculates the start threshold on the basis of a predicted reduction rate of the SOC from the start to the completion of the preheating control and the switching threshold during travel in the motor travel mode. The calculation unit calculates the predicted reduction rate on the basis of the SOC, the primary delay SOC obtained by applying filter processing to the SOC and a time constant of the filter processing.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] There is a method for preventing delays in the start of preheating by calculating a predicted value of the driving load amount based on past data on the driving load of a hybrid vehicle and setting the SOC of the battery that starts preheating the electrically heated catalyst based on that predicted value (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-148022 Summary of the Invention [Problem to be solved by the invention]

[0004] The above method requires calculations to be performed using a large amount of past data, which results in a large calculation load.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for a hybrid vehicle that can prevent a delay in the start of preheating of an electrically heated catalyst while reducing the calculation load. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a hybrid vehicle having an engine and a motor, an electrically heated catalyst arranged in an exhaust passage of the engine, a battery capable of supplying power to the motor and the electrically heated catalyst, and a detection unit that detects the SOC of the battery, the control unit starting pre-heating control when the SOC falls below a start threshold that starts pre-heating control of the electrically heated catalyst, a switching unit switching from a motor driving mode using the motor as a power source to a hybrid driving mode using at least the engine as a power source when the SOC falls below a switching threshold that is smaller than the start threshold, and a calculation unit that calculates the start threshold while driving in the motor driving mode based on a predicted rate of decline of the SOC from the start to the completion of the pre-heating control and the switching threshold, wherein the calculation unit calculates the predicted rate of decline based on the SOC, a first-order lag SOC obtained by filtering the SOC, and a time constant of the filtering.

[0007] The calculation unit may calculate the start threshold value at a calculation period that is longer as the running load of the hybrid vehicle is higher, based on the first-order lag SOC, which has a smaller time constant as the running load of the hybrid vehicle is higher.

[0008] The calculation unit may set the time constant before a predetermined time has elapsed since the hybrid vehicle started to travel in the motor travel mode to be smaller than the time constant after the predetermined time has elapsed, regardless of the travel load.

[0009] The calculation unit may calculate a plurality of first-order lag SOCs obtained by performing a plurality of filter processes each having a different combination of the time constant and the calculation period, select one first-order lag SOC from the plurality of first-order lag SOCs according to the road load, and calculate the start threshold based on the selected first-order lag SOC.

[0010] The calculation unit may calculate the running load based on a vehicle speed of the hybrid vehicle, a torque of the motor, and a rotation speed of the motor. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a control device for a hybrid vehicle that can prevent a delay in starting preheating of an electrically heated catalyst while reducing the calculation load. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Figure 2] FIG. 2 is a timing chart illustrating preheating control in this embodiment and a comparative example. [Figure 3] FIG. 3 is an explanatory diagram of calculation of the start threshold value. [Figure 4] FIG. 4A is an explanatory diagram of calculation of a predicted decrease rate, and FIG. 4B is a calculation method of a predicted decrease rate in a comparative example. [Figure 5] FIG. 5 is a flowchart illustrating the preheating control. [Figure 6] FIG. 6A is an example of a map that defines a time constant for each road load, and FIG. 6B is an example of a map that defines a calculation cycle for each road load. [Figure 7] FIG. 7 is an explanatory diagram of the difference in calculation period. [Figure 8] FIG. 8 is a diagram showing an example of a map that defines the running load according to the vehicle speed and the vehicle power. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Hybrid vehicle configuration] 1 is a schematic diagram of a hybrid vehicle 10. The hybrid vehicle 10 includes an engine 20 and a second motor 32 as power sources. The second motor 32 is, for example, a three-phase AC motor.

[0014] An electrically heated catalyst 23 that generates heat in response to the passage of current is mounted in the exhaust passage 21 of the engine 20. The electrically heated catalyst 23 is connected to a battery 50 via a power supply device 25.

[0015] The second motor 32 is connected to a battery 50 via a power control unit 35. The second motor 32 is coupled to drive wheels 40 via a reduction mechanism .

[0016] The engine 20 is connected to the drive wheels 40 via a power split mechanism 30 and a reduction gear mechanism 34. A first motor 31 is also connected to the power split mechanism 30. The first motor 31 is, for example, a three-phase AC motor. The power split mechanism 30 is a planetary gear mechanism, and can split the driving force of the engine 20 between the first motor 31 and the drive wheels 40.

[0017] The first motor 31 generates electricity by receiving driving force from the engine 20 and driving force from the drive wheels 40. The first motor 31 also serves as a starter that drives the rotary shaft of the engine 20 when starting the engine 20. In this case, the first motor 31 functions as a motor that generates driving force in response to the supply of electric power from the battery 50.

[0018] The first motor 31 and the second motor 32 are connected to a battery 50 via a power control unit 35. The AC power generated by the first motor 31 is converted to DC by the power control unit 35 and charged into the battery 50. In other words, the power control unit 35 functions as an inverter.

[0019] The DC power of the battery 50 is converted to AC by the power control unit 35 and supplied to the second motor 32. When the hybrid vehicle 10 is decelerating, the second motor 32 generates power using the driving force from the drive wheels 40. The generated power is then charged to the battery 50. In other words, the hybrid vehicle 10 performs regenerative charging. At this time, the second motor 32 functions as a generator. At this time, the AC power generated by the second motor 32 is converted to DC by the power control unit 35 and charged to the battery 50.

[0020] The ECU (Electronic Control Unit) 100 is an electronic control unit that performs control processing related to the engine 20, the first motor 31, the second motor 32, and the power supply device 25. The ECU 100 is mainly composed of a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 100 executes programs installed in the memory on the CPU to perform various control processing related to the engine 20 and the like. Various sensors are connected to the ECU 100, which will be described in detail later. The ECU 100 is an example of a control device, and functionally realizes a control unit, a switching unit, and a calculation unit, which will be described in detail later.

[0021] The ECU 100 receives detection signals from sensors provided in various parts of the hybrid vehicle 10. An ignition switch 101, a SOC (State Of Charge) sensor 102, and a vehicle speed sensor 103 are connected to the ECU 100. The ignition switch 101 detects whether the ignition is on or off. The SOC sensor 102 detects the charge amount of the battery 50 (hereinafter referred to as actual SOC). The SOC sensor 102 is an example of a detection unit. The vehicle speed sensor 103 detects the vehicle speed of the hybrid vehicle 1.

[0022] The ECU 100 switches the driving mode of the hybrid vehicle 10 between a motor driving mode and a hybrid driving mode. The motor driving mode is a driving mode in which the second motor 32 is driven using the power stored in the battery 50, thereby driving the drive wheels 40 using only the second motor 32. The hybrid driving mode is a driving mode in which the drive wheels 40 are driven using at least the driving force of the engine 20. The ECU 100 switches from the motor driving mode to the hybrid driving mode when the actual SOC falls below the switching threshold value. This makes it possible to suppress further decline in the actual SOC.

[0023] The ECU 100 executes preheating control to preheat the electrically heated catalyst 23 before switching from the motor driving mode to the hybrid driving mode. Specifically, the ECU 100 starts the preheating control when the actual SOC becomes equal to or less than a start threshold that is greater than the above-mentioned switching threshold. The preheating control is a control for raising the temperature of the electrically heated catalyst 23 to its activation temperature before the engine 20 starts. By raising the temperature of the electrically heated catalyst 23 to the activation temperature when the engine 20 starts, exhaust emissions can be reduced from the start of the engine 20. However, if the start of the preheating control is delayed, the engine 20 may start before the temperature of the electrically heated catalyst 23 reaches the activation temperature, resulting in a deterioration in exhaust emissions.

[0024] FIG. 2 is a timing chart illustrating preheating control in this embodiment and a comparative example. FIG. 2 shows the transitions of vehicle speed, specifically, first-order delay SOC (described later), actual SOC, catalyst temperature (temperature of the electrically heated catalyst 23), and a start request for the engine 20. First, the comparative example will be described. When the ignition is turned on (time t1), the vehicle speed in motor driving mode increases and the actual SOC begins to decrease. When the actual SOC falls below the start threshold of the comparative example, power is supplied to the electrically heated catalyst 23 and preheating control begins (time t5). This causes the catalyst temperature to rise. When the actual SOC falls below the switching threshold, the engine 20 starts and the mode is switched from motor driving mode to hybrid driving mode (time t6). In the comparative example, the start of preheating control is delayed, and the engine 20 starts before the catalyst temperature reaches the activation temperature.

[0025] Next, a description will be given of this embodiment. In this embodiment, the start threshold is a variable value rather than a fixed value, and is always set to a different value based on the actual SOC and first-order lag SOC. In this embodiment, as will be described in detail later, multiple first-order lag SOCs are calculated using multiple types of filter processing. The example in FIG. 2 shows first-order lag SOCs obtained by filter processing immediately after starting, low-load filter processing, and medium-load filter processing. As the hybrid vehicle 1 is just started between time t1 and time t2, as will be described in detail later, the start threshold is set based on the actual SOC and the first-order lag SOC obtained by filter processing immediately after starting. As the hybrid vehicle 1 is operating at a low load between time t2 and time t3, the hybrid vehicle 1 is operating at a low load, and the start threshold is set based on the actual SOC and the first-order lag SOC obtained by low-load filter processing. As the road load becomes medium after time t3, the start threshold is set based on the actual SOC and the first-order lag SOC obtained by medium-load filter processing.

[0026] The start threshold thus set is set to a value higher than the start threshold in the comparative example. Therefore, the actual SOC becomes equal to or lower than the start threshold at an earlier timing than in the comparative example, and pre-heating control is started (time t4). This allows the timing at which the catalyst temperature reaches the activation temperature to correspond to the timing at which the actual SOC becomes equal to or lower than the switching threshold (time t6), thereby reducing exhaust emissions when the engine 20 is started.

[0027] [How to calculate the starting threshold] In this embodiment, the start threshold is calculated based on the following formula (1). Start threshold = Switching threshold + Preheating consumption SOC + (Predicted decrease rate x Preheating required time)...(1) The pre-heating consumption SOC is the SOC consumed from the start to the completion of pre-heating control. The pre-heating required time is the time required from the start to the completion of pre-heating control. The pre-heating consumption SOC and the pre-heating required time may be stored in advance in the ROM of ECU 100, or may be calculated each time. The predicted decline rate is a predicted value of the decline rate of the SOC when pre-heating control is not executed. In other words, the predicted decline rate is a predicted value of the decline rate of the SOC consumed by driving in motor driving mode. The value obtained by multiplying the predicted decline rate by the pre-heating required time corresponds to the predicted value of the SOC consumed by driving in motor driving mode during the pre-heating required time.

[0028] 3 is an explanatory diagram of calculation of the start threshold. As shown in FIG. 3, the start threshold is calculated based on the switching threshold, which is a fixed value. The predicted decline rate corresponds to a predicted value of the SOC slope, and differs depending on the running load of the hybrid vehicle 1.

[0029] The predicted decline rate is calculated based on the following formula (2): Predicted decrease rate = ΔSOC / Time constant = (first-order lag SOC - actual SOC) / Time constant...(2)

[0030] FIG. 4A is an explanatory diagram of the calculation of the predicted decline rate. FIG. 4A shows the transition of the actual SOC and first-order lag SOC. The first-order lag SOC is calculated at a predetermined interval. ΔSOC is calculated by subtracting the current actual SOC from the previously calculated first-order lag SOC. In addition, since the time constant corresponds to the response delay time of the first-order lag SOC relative to the actual SOC, the predicted decline rate can be calculated using equation (2). Therefore, if only the most recently calculated first-order lag SOC value is saved, the predicted decline rate can be calculated, and the start threshold can be calculated.

[0031] FIG. 4B shows a method for calculating the predicted decline rate in a comparative example. In this comparative example, the predicted decline rate is calculated using a differential method. In the comparative example, it is necessary to store multiple actual SOC values ​​for the set time width. Therefore, the comparative example may increase the calculation load. As described above, in this embodiment, it is only necessary to store the most recent first-order lag SOC value. In this way, the start threshold can be calculated using less data, so the calculation load is reduced. Below, the pre-heating control in this embodiment will be described in detail.

[0032] [Preheating control] 5 is a flowchart illustrating the pre-heating control. This control is repeatedly executed while the ignition is on. The ECU 100 determines whether or not the engine 20 has not yet been started for the first time after the ignition is turned on (step S1). If the answer is No in step S1, this control ends. If the answer is Yes in step S1, the ECU 100 calculates multiple first-order lag SOCs by multiple filter processes based on the SOC (step S2).

[0033] The multiple filter processes have different time constants and calculation periods. FIG. 6A is an example of a map that defines a time constant for each road load. FIG. 6B is an example of a map that defines a calculation period for each road load. As shown in FIG. 6A, the higher the road load, the smaller the time constant. As shown in FIG. 6B, the higher the road load, the longer the calculation period. The ECU 100 performs multiple filter processes, including low-load filter process, medium-load filter process, high-load filter process, and the filter process immediately after starting shown in FIG. 2. In the low-load filter process, the first-order lag SOC is calculated with a time constant τ3 and a calculation period T1. In the medium-load filter process, the first-order lag SOC is calculated with a time constant τ2 and a calculation period T2. In the high-load filter process, the first-order lag SOC is calculated with a time constant τ1 and a calculation period T3. In the filter process immediately after starting shown in FIG. 2, the first-order lag SOC is calculated with a time constant τ0 that is smaller than the time constant τ1 and a calculation period T3, regardless of the road load.

[0034] The reason why the time constant is set to a smaller value as the road load increases is as follows: the higher the road load, the greater the predicted rate of decrease in actual SOC. Filtering with a small time constant improves the responsiveness of the first-order lag SOC to the actual SOC, which has a large rate of decrease.

[0035] The reason why the calculation period is set longer as the road load increases will be explained. FIG. 7 is an explanatory diagram of the difference in calculation period. FIG. 7 shows the first-order lag SOC for cases where the calculation period is short and long relative to the actual SOC. As shown in FIG. 7, the ΔSOC is calculated as a larger value when the calculation period is long than when the calculation period is short. As described above, the higher the road load, the greater the predicted rate of decline of the actual SOC. In contrast, when the calculation period is short, the ΔSOC is calculated as a small value, which may result in a small predicted decline rate. As a result, if the predicted decline rate is calculated lower than the actual decline rate when the road load is high, the start threshold may be calculated lower than the ideal start threshold, which may delay the start of pre-heating control. This may result in the catalyst temperature not reaching the activation temperature when the engine 20 is started, resulting in a deterioration in emissions. In this embodiment, such emissions are reduced by setting the calculation period longer as the road load increases.

[0036] FIG. 8 is an example of a map that defines the running load according to the vehicle speed and vehicle power. The vehicle power is calculated based on the value obtained by multiplying the torque of the second motor 32 by the rotation speed of the second motor 32. The running load is defined to be higher as the vehicle speed is faster and the vehicle power is greater. For example, the most recent average vehicle speed is used as the vehicle speed. The most recent average vehicle speed power is used as the vehicle power.

[0037] Furthermore, as described above, the first-order lag SOC is calculated by the filtering process immediately after starting, which is not dependent on the road load. In the filtering process immediately after starting, the first-order lag SOC is calculated with a time constant τ0 that is smaller than the time constant τ1. Because a delay in output response occurs immediately after starting due to the nature of the filtering process, a small time constant is used to accommodate this. In addition, in the filtering process immediately after starting, the first-order lag SOC is calculated using a calculation cycle T3. This is because, by calculating a large ΔSOC as described above, it is possible to prevent a delay in the start of pre-heating control and a deterioration in emissions.

[0038] Next, the ECU 100 selects a first-order delay SOC from the plurality of first-order delay SOCs to be used for calculating a start threshold for starting pre-heating control (step S3). Before a predetermined time has elapsed since the ignition was turned on, the first-order delay SOC calculated by the immediately after start filter described above is selected. After the predetermined time has elapsed since the ignition was turned on, the first-order delay SOC calculated by filtering according to the driving load is selected.

[0039] Next, the ECU 100 calculates the start threshold value using the above-mentioned formula (1) based on the selected first-order lag SOC at the same calculation period as the selected first-order lag SOC (step S4). Step S4 is a process executed by the calculation unit. Next, the ECU 100 determines whether the actual SOC is equal to or less than the start threshold value (step S5). If the answer is No in step S5, this control ends. If the answer is Yes in step S5, the ECU 100 starts energizing the electrically heated catalyst 23 to start pre-heating control (step S6). Steps S5 and S6 are an example of a process executed by the control unit.

[0040] Next, the ECU 100 determines whether the actual SOC is equal to or less than the switching threshold value (step S7). If the answer is No in step S7, the control ends. If the answer is Yes in step S7, the ECU 100 stops the pre-heating control and switches the driving mode to the hybrid driving mode (step S8). Steps S7 and S8 are an example of processing executed by the switching unit.

[0041] In the above embodiment, a hybrid vehicle equipped with two motors has been described as an example, but the present invention is not limited to this, and may be a one-motor hybrid equipped with one motor.

[0042] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0043] 1 Hybrid vehicle 20 Engine 23 Electrically heated catalyst 32 Second motor 100 ECU (control unit, control section, switching section, calculation section) 102 SOC sensor (detection part)

Claims

1. A control device for a hybrid vehicle having an engine, a motor, an electrically heated catalyst disposed in an exhaust passage of the engine, a battery capable of supplying power to the motor and the electrically heated catalyst, and a detection unit that detects an SOC of the battery, a control unit that starts pre-heating control when the SOC becomes equal to or less than a start threshold that starts pre-heating control of the electrically heated catalyst; a switching unit that switches from a motor driving mode using the motor as a power source to a hybrid driving mode using at least the engine as a power source when the SOC becomes equal to or less than a switching threshold that is smaller than the start threshold; a calculation unit that calculates the start threshold value based on a predicted rate of decrease in the SOC from the start to the completion of the pre-heating control during running in the motor running mode and the switching threshold value, The calculation unit calculates the predicted decline rate based on the SOC, a first-order lag SOC obtained by filtering the SOC, and a time constant for the filtering.

2. 2. The control device for a hybrid vehicle according to claim 1, wherein the calculation unit calculates the start threshold value at a calculation period that is longer as the driving load of the hybrid vehicle is higher, based on the first-order lag SOC, which has a smaller time constant as the driving load of the hybrid vehicle is higher.

3. 3. The control device for a hybrid vehicle according to claim 2, wherein the calculation unit makes the time constant smaller before a predetermined time has elapsed since the hybrid vehicle started to run in the motor running mode than the time constant after the predetermined time has elapsed, regardless of the running load.

4. 3. The control device for a hybrid vehicle according to claim 2, wherein the calculation unit calculates a plurality of the first-order lag SOCs by performing a plurality of the filter processes each having a different combination of the time constant and the calculation period, selects one of the plurality of first-order lag SOCs in accordance with the traveling load, and calculates the start threshold value based on the selected first-order lag SOC.

5. 5. The control device for a hybrid vehicle according to claim 2, wherein the calculation unit calculates the running load based on a vehicle speed of the hybrid vehicle, a torque of the motor, and a rotation speed of the motor.

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