Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle improved in startability.SOLUTION: A control device of a hybrid vehicle is provided with a motor on a power transmission path between an engine and wheels and is provided with a clutch between the engine and the motor on the power transmission path. The control device of a hybrid vehicle is equipped with an obtaining portion that obtains engine speed, a first determining portion that determines whether or not the engine is being driven and the clutch is in either one of an open state or a slip state, a second determining portion that determines whether or not the engine speed drops from a target engine speed, and a correcting portion that corrects so as to increase the output torque of the engine when the first and second determining portions make a positive determination.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] 2. Description of the Related Art A hybrid vehicle is known in which a motor is provided on a power transmission path between an engine and wheels, and a clutch is provided on the power transmission path between the engine and the motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-067008 A Summary of the Invention [Problem to be solved by the invention]

[0004] When starting a hybrid vehicle, after the engine and the motor are started, the clutch goes from a disengaged state to a slipped state and then to an engaged state, and the engine and the motor are connected. At this time, the rotation speed of the engine and the motor is maintained at, for example, a target idle rotation speed. Here, for example, at a low-temperature start or when some abnormality occurs in the motor, the output torque of the motor may be lower than the desired output torque. If the clutch goes into a slipped state in such a state, the engine output torque may not be able to compensate for the decrease in the output torque of the motor, and the engine rotation speed may be lower than the target idle rotation speed. In this case, even after the clutch goes into an engaged state, the rotation speed of the engine and the motor may not be able to maintain the target idle rotation speed. In this way, the startability may be deteriorated.

[0005] For this reason, when the clutch is in a slip state, it is possible to make a correction so as to increase the output torque of the engine. Here, it is possible to determine whether the clutch is in a slip state based on the hydraulic pressure supplied to the clutch. However, the relationship between the magnitude of the hydraulic pressure and the state of the clutch varies depending on the environmental temperature and the amount of oil, and it is difficult to accurately determine the state of the clutch based on the hydraulic pressure. For this reason, even if it is determined that the clutch is in a slip state based on the hydraulic pressure, such a determination is actually made after the clutch is engaged, and the above correction cannot be performed at an appropriate time, which may result in a decrease in startability.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS The present invention has an object to provide a control device for a hybrid vehicle with improved starting performance. [Means for solving the problem]

[0007] The object of the present invention is to provide a control device for a hybrid vehicle in which a motor is provided on a power transmission path between an engine and wheels, and a clutch is provided between the engine and the motor on the power transmission path, the control device being configured to control the rotation speed of the engine. and the number of revolutions of the motor. a first determination unit that determines whether the engine is running and the clutch is in either an open state or a slip state; Idol a second determination unit that determines whether the engine speed has decreased or not; and when the first and second determination units make a positive determination, A specified torque increase A correction unit that performs a correction to increase the torque increase amount is increased as the shortage speed, which is the value obtained by subtracting the engine speed from the target idle speed, increases, the torque increase amount is increased as the decrease in the engine speed per unit time increases, and when the difference speed, which is the engine speed minus the motor speed, is equal to or less than a value that can be regarded as the state immediately before the clutch is engaged, the torque increase amount is gradually decreased to zero. This can be achieved by a control device for a hybrid vehicle. Effect of the Invention

[0008] According to the present invention, a control device for a hybrid vehicle with improved starting performance can be provided. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram of a hybrid vehicle. [Diagram 2] FIG. 2 is a timing chart showing changes in engine speed, motor speed, and hydraulic pressure supplied to the K0 clutch in a comparative example. [Diagram 3] FIG. 3 is a flowchart showing an example of the output torque increase control executed by the ECU. [Figure 4] FIG. 4 is an example of a map that defines the torque increase amount. [Diagram 5] FIG. 5 is a timing chart showing the transition of the engine speed, the motor speed, the hydraulic pressure supplied to the K0 clutch, and the torque increase amount in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [General configuration of hybrid vehicle] FIG. 1 is a schematic diagram of a hybrid vehicle. The hybrid vehicle is equipped with an engine 10 and a motor 15 as driving sources for traveling. The engine 10 is, for example, a gasoline engine, but may be a diesel engine. The engine 10 is provided with a starter 24 for cranking and starting the engine 10. A transmission unit 11 is provided on a power transmission path from the engine 10 to wheels 13. The transmission unit 11 and the left and right wheels 13 are drivingly connected via a differential 12.

[0011] The transmission unit 11 is provided with a K0 clutch 14 and a motor 15. In the transmission unit 11, the motor 15 is installed so as to be located on a power transmission path from the engine 10 to the wheels 13. The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. When supplied with hydraulic pressure, the K0 clutch 14 changes from a released state to a slip state and then to an engaged state, thereby connecting the power transmission between the engine 10 and the motor 15. When the supply of hydraulic pressure is stopped, the K0 clutch 14 changes to a released state and cuts off the power transmission between the engine 10 and the motor 15.

[0012] The motor 15 is connected to the vehicle battery 16 via an inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the vehicle battery 16, and also functions as a generator that generates power to charge the vehicle battery 16 in response to power transmission from the engine 10 and the wheels 13. The power exchanged between the motor 15 and the vehicle battery 16 is adjusted by the inverter 17.

[0013] The transmission unit 11 is provided with a torque converter 18, which is a fluid coupling having a torque amplifying function, and a stepped automatic transmission 19 that switches the gear ratio in multiple stages by switching the gear stage. In the transmission unit 11, the automatic transmission 19 is provided between the motor 15 and the wheels 13 on the power transmission path. The motor 15 and the automatic transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that is supplied with hydraulic pressure and enters an engaged state to directly connect the motor 15 and the automatic transmission 19.

[0014] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for each of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling the operating hydraulic pressures thereof.

[0015] The hybrid vehicle is provided with an ECU (Electronic Control Unit) 23. The ECU 23 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data. The ECU 23 is an example of a control device for the hybrid vehicle, and functionally realizes an acquisition unit, a first determination unit, a second determination unit, and a correction unit, which will be described in detail later.

[0016] The ECU 23 controls the operation of the engine 10 and the motor 15. For example, the ECU 23 controls the torque of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 23 also controls the inverter 17 to adjust the amount of power exchanged between the motor 15 and the vehicle battery 16, thereby controlling the torque of the motor 15. Furthermore, the ECU 23 controls the operation of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22. The ECU 23 receives detection signals such as an engine speed sensor 25 that detects the rotation speed of the crankshaft of the engine 10, a motor speed sensor 26 that detects the rotation speed of the motor 15, and an accelerator pedal opening degree, which is the amount of depression of the accelerator pedal by the driver.

[0017] [Startability in Comparative Examples] Next, the startability of a hybrid vehicle in a comparative example will be described. FIG. 2 is a timing chart showing the transition of the rotation speed [rpm] of the engine 10, the rotation speed [rpm] of the motor 15, and the oil pressure [Pa] supplied to the K0 clutch 14 in the comparative example. When the ignition of the hybrid vehicle is turned on, the starter 24 is driven to start the engine 10 (time t1), and the rotation speed of the engine 10 is maintained at the target idle rotation speed. After that, the motor 15 starts (time t2), and the oil pressure to the K0 clutch 14 in the disengaged state starts to increase (time t3). Here, for example, at the time of starting in a normal temperature environment with an outside air temperature of 5°C to 30°C, the rotation speed of the engine 10 maintains the target idle rotation speed, and even if the K0 clutch 14 enters a slip state (time t4) and then enters an engaged state (time t5), the rotation speeds of the engine 10 and the motor 15 are maintained at the target idle rotation speed.

[0018] However, for example, at the time of starting in a low-temperature environment where the outside air temperature is less than 5°C, the viscosity of the lubricating oil used in the K0 clutch 14, the motor 15, and the automatic transmission 19 is high because the temperature of the lubricating oil is low, and the friction torque of these oils is increased. As a result, the output torque of the motor 15 is lower than the desired output torque. Therefore, at the time of low-temperature starting, when the K0 clutch 14 is in a slip state (time t4), the output torque of the engine 10 cannot compensate for the decrease in the output torque of the motor 15, and the rotation speed of the engine 10 is lower than the target idle rotation speed. When the K0 clutch 14 is in an engaged state in this state (time t5), the rotation speed of the engine 10 and the motor 15 may not be maintained at the target idle rotation speed. This may result in a decrease in startability, such as stalling of the engine 10. Therefore, the ECU 23 of this embodiment executes the following output torque increase control.

[0019] [Output torque increase control] 3 is a flowchart showing an example of the output torque increase control executed by the ECU 23. This control is repeatedly executed while the ignition of the hybrid vehicle is on. First, the ECU 23 determines whether the engine 10 is running (step S1). The determination in step S1 can be made based on the detection value of the engine speed sensor 25.

[0020] Next, the ECU 23 judges whether the state of the K0 clutch 14 is either the released state or the slip state (step S2). In step S2, the ECU 23 may judge that the state of the K0 clutch 14 is either the released state or the slip state if the detection value of the hydraulic sensor supplied to the K0 clutch 14 is smaller than a value indicating that the K0 clutch 14 is in an engaged state. In addition, in step S2, the ECU 23 may judge that the state of the K0 clutch 14 is either the released state or the slip state if the rotation speed of the engine 10 and the rotation speed of the motor 15 do not match. The processes of steps S1 and S2 are an example of the process executed by the first judgment unit. If the result of either step S1 or S2 is No, the control ends.

[0021] If the results of steps S1 and S2 are Yes, the ECU 23 acquires the rotation speed of the engine 10 and the rotation speed of the motor 15 based on the detection values ​​of the engine rotation speed sensor 25 and the motor rotation speed sensor 26 (step S3). The process of step S3 is an example of a process executed by the acquisition unit.

[0022] Next, the ECU 23 judges whether the rotation speed of the motor 15 is equal to or greater than a predetermined value α (step S4). The predetermined value α is set to a value that is greater than zero and is lower than the target rotation speed. Step S4 will be described in detail later. If the result of step S4 is No, this control ends.

[0023] If the result of step S4 is Yes, the ECU 23 determines whether the rotation speed of the engine 10 has decreased from the target rotation speed (step S5). The process of step S5 is an example of a process executed by the second determination unit. If the result of step S5 is No, this control ends. For example, if the rotation speed of the engine 10 has increased above the target rotation speed, the result of step S5 is No.

[0024] If the answer is Yes in step S5, the ECU 23 executes output torque increase correction (step S6). The output torque increase correction is a correction that increases the output torque of the engine 10 by an amount of torque increase calculated based on a map in FIG. 4 described later, compared to a case where the output torque increase correction is not executed. The increase in the output torque of the engine 10 can be realized by controlling the throttle opening, the ignition timing, and the fuel injection amount. The process of step S6 is an example of a process executed by a correction unit.

[0025] In this way, if the results of steps S1, S2, and S4 are Yes, and if it is determined in step S5 that the rotation speed of the engine 10 has dropped from the target rotation speed, the output torque increase correction is executed. For example, it is possible to determine that the K0 clutch 14 is in a slip state based on the hydraulic pressure supplied to the K0 clutch 14, and then execute the output torque increase correction, but as described above, it is difficult to accurately determine the state of the K0 clutch 14 based on the hydraulic pressure. For this reason, as in this embodiment, the output torque increase correction of the engine 10 can be started at the timing when the rotation speed of the engine 10 actually starts to drop from the target rotation speed, and the output torque increase correction can be executed at an appropriate timing.

[0026] FIG. 4 is an example of a map that specifies the torque increase amount. In FIG. 4, the horizontal axis indicates the amount of change in the rotation speed of the engine 10 per unit time [rpm / msec], and the vertical axis indicates the torque increase amount [N·m]. FIG. 4 also shows the torque increase amount in the case of rotation speed shortages β1 and β2, which are values ​​obtained by subtracting the rotation speed of the engine 10 from the target rotation speed. The rotation speed shortage β1 is a value greater than zero. The rotation speed shortage β2 is a value greater than the rotation speed shortage β1.

[0027] Although the map in FIG. 4 shows only two cases of the insufficient rotation speed, β1 and β2, in reality, the torque increase amount is specified for each insufficient rotation speed. In detail, the map in FIG. 4 specifies that when the amount of change in the rotation speed of the engine 10 is a constant negative value, the torque increase amount increases as the insufficient rotation speed increases. Here, when the amount of change in the rotation speed of the engine 10 is a negative value, it indicates that the rotation speed of the engine 10 is decreasing. When the amount of change in the rotation speed of the engine 10 is a positive value, it indicates that the rotation speed of the engine 10 is increasing. When the amount of change in the rotation speed of the engine 10 is zero, it indicates that the rotation speed of the engine 10 is constant.

[0028] As shown in Fig. 4, the greater the insufficient rotation speed, the greater the torque increase amount, and the greater the decrease in the rotation speed of the engine 10, the greater the torque increase amount. This is because the greater the insufficient rotation speed and the greater the decrease in the rotation speed of the engine 10, the greater the torque required to increase the rotation speed of the engine 10 to the target rotation speed. In this way, the output torque of the engine 10 can be increased without being excessive or insufficient with respect to the required torque.

[0029] Next, the ECU 23 judges whether or not the differential speed obtained by subtracting the speed of the motor 15 from the speed of the engine 10 is equal to or less than a threshold value γ (step S7). The threshold value γ is set to a value that is close to zero but not equal to zero, and that can be regarded as a state immediately before the K0 clutch 14 is engaged. If the result in step S7 is No, this control ends.

[0030] If the result of step S7 is Yes, the ECU 23 executes a gradual decrease process for gradually decreasing the set torque increase amount to zero (step S8). This makes it possible to suppress the rotation speed of the engine 10 from excessively increasing beyond the target rotation speed due to the execution of the output torque increase correction.

[0031] Here, it is also conceivable to start the gradual change reduction process after determining that the K0 clutch 14 is in a state immediately before engagement based on the hydraulic pressure supplied to the K0 clutch 14. However, as described above, it is difficult to accurately determine the state of the K0 clutch 14 based on the hydraulic pressure. For this reason, the gradual change reduction process is started with a delay after the K0 clutch 14 is in an engaged state, and there is a risk that an excessive increase in the rotation speed of the engine 10 due to the execution of the output torque increase correction cannot be suppressed. Therefore, by using the differential rotation speed obtained by subtracting the rotation speed of the motor 15 from the rotation speed of the engine 10, it is possible to accurately determine whether the K0 clutch 14 is in a state immediately before engagement, and to start the gradual change reduction process from a state immediately before engagement of the K0 clutch 14, thereby suppressing an excessive increase in the rotation speed of the engine 10.

[0032] [Startability of this embodiment] Next, the startability of the hybrid vehicle in this embodiment will be described. FIG. 5 is a timing chart showing the transition of the rotation speed of the engine 10, the rotation speed of the motor 15, the hydraulic pressure supplied to the K0 clutch 14, and the torque increase amount in this embodiment. FIG. 5 corresponds to FIG. 2, and since it is the same as FIG. 2 up to time t3, the overlapping description will be omitted. The rotation speed of the motor 15 becomes equal to or higher than the predetermined value α (time t3a), and the above-mentioned step S4 is judged as Yes. After that, the rotation speed of the engine 10 starts to decrease from the target rotation speed (time t4), and the output torque increase correction is performed. This suppresses the decrease in the rotation speed of the engine 10. After that, when the difference rotation speed obtained by subtracting the rotation speed of the motor 15 from the rotation speed of the engine 10 becomes equal to or lower than the threshold value γ (time t5), a gradual decrease process is executed on the torque increase amount, and the torque increase amount is gradually decreased to zero. In this way, the decrease in the rotation speed of the engine 10 can be suppressed, and the startability is improved.

[0033] As described at time t3a and step S4, one of the prerequisites for executing the output torque increase correction is that the rotation speed of the motor 15 is equal to or greater than the predetermined value α. For example, the rotation speed of the engine 10 may temporarily drop from the target rotation speed during a period when the combustion state is not stable immediately after the start of the engine 10 before the rotation speed of the motor 15 becomes equal to or greater than the predetermined value α. Even in such a case, the prerequisite for the output torque increase correction is that the rotation speed of the motor 15 is equal to or greater than the predetermined value α, so that the output torque increase correction is prevented from being executed at an unintended timing. In addition, the timing of the rise in the rotation speed at the start of the motor 15 varies depending on the remaining charge of the in-vehicle battery 16 and the filling state of the hydraulic oil in the K0 clutch 14. Even in such a case, the prerequisite for the output torque increase correction is that the rotation speed of the motor 15 is equal to or greater than the predetermined value α, so that the output torque increase correction can be executed without being affected by the variation in the rise in the rotation speed of the motor 15.

[0034] In the above embodiment, the ECU 23 acquires the rotation speed of the engine 10 and the rotation speed of the motor 15 between step S2 and step S4, but this is not limited to this. For example, the ECU 23 may acquire these rotation speeds before step S1, or after step S1 and before step S2, or may constantly acquire these rotation speeds while executing each process.

[0035] In the above embodiment, the map of FIG. 4 specifies the torque increase amount in consideration of the decrease in the output torque of the motor 15 at the time of low-temperature start. For example, when it is detected that the motor 15 has some abnormality such as a breakdown, the output torque increase correction may be performed using a map for the motor 15 at the time of the abnormality occurrence, which is different from the map of FIG. 4. For example, when an abnormality occurs to the extent that the motor 15 cannot start by itself, the K0 clutch 14 is in a slip state, and the motor 15 is forcibly rotated along with the rotation of the engine 10. In this case, it is necessary to increase the output torque of the engine 10 more than at the time of low-temperature start. For this reason, it is preferable to specify the map for the motor 15 at the time of the abnormality occurrence so that the torque increase amount is larger than that of the map of FIG. 4. This makes it possible to improve the startability of the hybrid vehicle even when an abnormality occurs in the motor 15.

[0036] In the above embodiment, a hybrid vehicle is controlled by a single ECU 23, but this is not limited to the above, and the above-mentioned control may be performed by multiple ECUs, such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

[0037] 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 described in the claims. [Explanation of symbols]

[0038] 10 Engine 13 wheels 14 K0 clutch 15 Motor 19 Automatic transmission 23 ECU (control unit for hybrid vehicles) 25 Engine speed sensor 26 Motor speed sensor

Claims

[Claim 1] A control device for a hybrid vehicle in which a motor is provided on a power transmission path between an engine and wheels, and a clutch is provided between the engine and the motor on the power transmission path, an acquisition unit that acquires a rotation speed of the engine and a rotation speed of the motor; a first determination unit that determines whether or not the engine is running and the clutch is in either a released state or a slipping state; a second determination unit that determines whether a rotation speed of the engine has decreased from a target idle rotation speed; a correction unit that performs a correction to increase an output torque of the engine by a predetermined torque increase amount when the first and second determination units make a positive determination, the torque increase amount is increased as the insufficient rotation speed, which is a value obtained by subtracting the rotation speed of the engine from the target idle rotation speed, increases; The torque increase amount is increased as the decrease in the engine speed per unit time increases, A control device for a hybrid vehicle, which gradually reduces the torque increase amount to zero when a differential rotation speed obtained by subtracting the rotation speed of the motor from the rotation speed of the engine is equal to or less than a value that can be regarded as a state immediately before the clutch is engaged.

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