Control device for a hybrid vehicle

Abstract

To provide a control device of a hybrid vehicle, the control device materializing suppression of increase of loads on a motor.SOLUTION: A control device of a hybrid vehicle is provided, comprising: a deceleration control portion controlling an engine and a motor which are power sources for vehicle travelling, thereby controlling deceleration of the hybrid vehicle; a fuel cut control portion which restricts or permits fuel cut in the engine on the basis of a result of whether a predetermined condition is satisfied or not; a turning control portion which performs turning control by which the deceleration is increased when the hybrid vehicle travels while turning more than when the vehicle travels in a straight line; and a deceleration restricting portion which restricts the deceleration at the time when the fuel cut is restricted and the turning control is performed, in such a manner that the deceleration becomes lower than the deceleration at the time when the fuel cut is permitted and the turning control is performed.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In a hybrid vehicle, it is possible to secure the deceleration of the vehicle by executing fuel cut (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Based on the establishment of predetermined conditions, fuel cut may be restricted. When the fuel cut is restricted, the deceleration decreases. In such a case, turning control requiring a high deceleration may be executed. During the execution of turning control where the fuel cut is restricted and a high deceleration is required, it is conceivable to secure a high deceleration by increasing the regenerative torque of the motor. However, in this case, there is a risk that the load on the motor increases.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that suppresses an increase in the load on the motor.

Means for Solving the Problems

[0006] The above object can be achieved by a control device for a hybrid vehicle, comprising: a deceleration control unit that controls an engine and a motor, which are driving power sources, to control the deceleration of the hybrid vehicle; a fuel cut control unit that restricts or permits fuel cut in the engine based on the establishment or non - establishment of a predetermined condition; a turning control unit that executes turning control to increase the deceleration during turning travel of the hybrid vehicle compared to straight - ahead travel; and a deceleration limiting unit that limits the deceleration during the execution of the turning control when fuel cut is restricted to be lower than the deceleration during the execution of the turning control when fuel cut is permitted.

[0007] The deceleration limiting unit may limit the deceleration during the execution of the turning control when fuel cut is restricted to be higher than the deceleration during the stop of the turning control when fuel cut is restricted.

[0008] The deceleration limiting unit may limit the deceleration during the execution of the turning control when fuel cut is restricted to be lower than the deceleration during the stop of the turning control when fuel cut is permitted.

[0009] Comprising an over - temperature prediction unit that predicts whether a filter for collecting particulate matter in the exhaust of the engine will overheat due to the execution of fuel cut, and the fuel cut control unit restricts fuel cut assuming that the predetermined condition is established when it is predicted that the filter will overheat, and permits fuel cut assuming that the predetermined condition is not established when it is predicted that the filter will not overheat.

[0010] It may further comprise a notification control unit that causes a notification unit to notify that the deceleration is restricted when fuel cut is restricted.

Advantages of the Invention

[0011] According to the present invention, a control device for a hybrid vehicle that suppresses an increase in the load of the motor can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] [Schematic Configuration of Hybrid Vehicle] Figure 1 is a schematic configuration diagram of the hybrid vehicle 1 of this embodiment. This hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor generator (hereinafter referred to as "first MG (Motor Generator)") 14, a second motor generator (hereinafter referred to as "second MG") 15, a PCU (Power Control Unit) 17, a battery 18, a power split mechanism 50, a transmission mechanism 51, a deceleration mechanism 52, and drive wheels 53. The engine 10 is a gasoline engine, but is not limited thereto and may be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are the driving power sources of the hybrid vehicle 1.

[0014] Both the first MG 14 and the second MG 15 have a function as a motor that outputs torque when driving power is supplied, and a function as a generator that generates regenerative power when torque is applied. Specifically, the first MG 14 and the second MG 15 are alternating current rotating electric machines. The alternating current rotating electric machine is, for example, a permanent magnet type synchronous motor provided with a rotor in which permanent magnets are embedded.

[0015] The first MG 14 and the second MG 15 are electrically connected to the battery 18 via the PCU 17. The PCU 17 includes a first inverter that exchanges power with the first MG 14, a second inverter that exchanges power with the second MG 15, and a converter. The converter boosts the power of the battery 18 and supplies it to the first and second inverters, and reduces the power supplied from the first and second inverters and supplies it to the battery 18. The first inverter converts DC power from the converter to AC power and supplies it to the first MG 14, and converts AC power from the first MG 14 to DC power and supplies it to the converter. The second inverter converts DC power from the converter to AC power and supplies it to the second MG 15, and converts AC power from the second MG 15 to DC power and supplies it to the converter. That is, the PCU 17 charges the battery 18 using the regenerative electric power generated in the first MG 14 or the second MG 15, and drives the first MG 14 or the second MG 15 using the charged electric power of the battery 18.

[0016] The battery 18 is composed of a plurality of stacked cells. The cells are, for example, secondary cells such as nickel-metal hydride cells or lithium-ion cells.

[0017] The power split mechanism 50 mechanically connects the crankshaft of the engine 10, the rotating shaft of the first MG 14, and the output shaft of the power split mechanism 50. The power split mechanism 50 is, for example, a planetary gear mechanism including a sun gear, a planetary carrier, a pinion gear, and a ring gear. The output shaft of the power split mechanism 50 is connected to a transmission mechanism 51. In addition, the rotating shaft of the second MG 15 is also connected to the transmission mechanism 51. The transmission mechanism 51 is connected to a CVT 52, and the driving forces of the engine 10, the first MG 14, and the second MG 15 are transmitted to driving wheels 53 via the transmission mechanism 51 and the CVT 52.

[0018] The speed reduction mechanism 52 is a multi-stage automatic transmission that changes the gear ratio under the control of the ECU 100 to change the transmission ratio. Thereby, the speed reduction mechanism 52 switches between a plurality of power transmission states. The plurality of power transmission states include an N (Neutral) range, a D (Drive) range, an R (Reverse) range, and a P (Parking) range. In the N range, power transmission to the drive wheels 53 is interrupted. In the D range, forward travel is possible. In the R range, reverse travel is possible. In the P range, power transmission to the drive wheels 53 is interrupted and rotation of the output shaft of the speed reduction mechanism 52 is mechanically blocked. The range of the speed reduction mechanism 52 can be switched by manual operation of the shift lever 90 by the driver. Note that instead of the speed reduction mechanism 52, a continuously variable transmission (hereinafter referred to as "CVT (Continuously Variable Transmission)") that continuously changes the gear ratio may be employed.

[0019] The ECU 100 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to vehicle travel control and a memory in which control programs and data are stored. The ECU 100 is an example of a control device of the hybrid vehicle 1 and functionally realizes, in detail, a deceleration control unit, a fuel cut control unit, a turning control unit, a deceleration limit unit, an overheating prediction unit, and a notification control unit, which will be described later.

[0020] The display unit 80 is provided on the instrument panel of the hybrid vehicle 1. The display unit 80 is an example of a notification unit that, as will be described in detail later, notifies that the deceleration of the hybrid vehicle 1 is suppressed due to the limitation of fuel cut. Note that instead of the display unit 80, for example, a speaker of an audio system or a navigation system of the hybrid vehicle 1 may be used.

[0021] Signals from an ignition switch 71, a water temperature sensor 72, a crank angle sensor 73, an air flow meter 74, a shift position sensor 75, an accelerator opening sensor 76, and a yaw rate sensor 77 are input to the ECU 100. The water temperature sensor 72 detects the temperature of the cooling water of the engine 10. The crank angle sensor 73 detects the engine rotation speed, which is the rotation speed of the crankshaft of the engine 10. The air flow meter 74 detects the intake air amount introduced into the engine 10. The shift position sensor 75 detects the operation position of the shift lever 90. The accelerator opening sensor 76 detects the operation position of the accelerator pedal 91. The yaw rate sensor 77 detects the angular velocity (yaw rate) around the vertical axis of the hybrid vehicle 1.

[0022] The ECU 100 controls acceleration and deceleration based on the accelerator operation amount. Specifically, the outputs of the engine 10, the first MG 14, and the second MG 15 are controlled so as to achieve a target acceleration or a target deceleration set based on the accelerator operation amount. The output of the engine 10 is controlled by the intake air amount and the fuel injection amount. The outputs of the first MG 14 and the second MG 15 are controlled by the PCU 17. The above control is an example of the process executed by the deceleration control unit.

[0023] The ECU 100 executes turning control based on the detection result of the yaw rate sensor 77. The turning control is a control that increases the deceleration during turning travel compared to straight-ahead travel. Specifically, the ECU 100 controls the deceleration so that the actual yaw rate during turning travel becomes the target yaw rate. The target yaw rate is determined such that the square root of the sum of the squares of the driving front-rear force and the lateral force of the hybrid vehicle 1 is less than or equal to the radius of the friction circle of the hybrid vehicle 1. Incidentally, the radius of the friction circle of the hybrid vehicle 1 is calculated by multiplying the friction coefficient of the road surface by the vertical load of the hybrid vehicle 1. Therefore, the larger the target yaw rate, the smaller the value of the friction circle is calculated, and the deceleration is controlled to increase. Also, during straight-ahead travel, the turning control is not executed. The turning control is an example of the processing executed by the turning control unit. Incidentally, the turning control is not limited to the above, and for example, the turning control may be executed based on the detection result of a lateral acceleration sensor that detects the lateral acceleration of the hybrid vehicle 1. In this case, for example, the greater the lateral acceleration detected by the lateral acceleration sensor, the greater the deceleration is controlled to be.

[0024] [Schematic Configuration of Engine] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, intake valves 36, an exhaust passage 37, and exhaust valves 38. Only one of the plurality of cylinders 30 of the engine 10 is shown in Figure 2. Combustion of the air-fuel mixture takes place in the cylinder 30. The piston 31 is reciprocally accommodated in each cylinder 30 and is connected to the crankshaft 33, which is the output shaft of the engine 10, via the connecting rod 32. The connecting rod 32 and the crankshaft 33 convert the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0025] The cylinder 30 is provided with an in-cylinder injection valve 41d. The in-cylinder injection valve 41d injects fuel directly into the cylinder 30. The intake passage 35 is provided with a port injection valve 41p that injects fuel toward the intake port 35p. Each cylinder 30 is provided with an ignition device 42 that ignites an air-fuel mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41d and the port injection valve 41p by means of spark discharge. Note that at least one of the in-cylinder injection valve 41d and the port injection valve 41p may be provided.

[0026] The intake passage 35 is connected to the intake port 35p of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of each cylinder 30 via an exhaust valve 38. The intake passage 35 is provided with the above-described air flow meter 74 and a throttle valve 40 that controls the intake air amount.

[0027] The exhaust passage 37 is provided with a three-way catalyst 43 and a GPF (Gasoline Particulate Filter) 44 from the upstream side. The three-way catalyst 43 contains, for example, catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has an oxygen storage capacity, and purifies NOx, HC, and CO.

[0028] The GPF 44 is a porous ceramic structure that collects exhaust particulates (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. Further, the GPF 44 has a noble metal such as platinum supported thereon. During regeneration control, this noble metal promotes the oxidation reaction of PM on which it has been deposited. The GPF 44 is an example of a filter. Note that, for example, when the engine 10 is a diesel engine, a DPF (Diesel Particulate Filter) is provided instead of the GPF 44.

[0029] By increasing or decreasing the opening degree of the throttle valve 40, the amount of intake air introduced into the cylinder 30 can be increased or decreased. The opening degree of the throttle valve 40 is controlled according to a required opening degree from the ECU 100.

[0030] When the accelerator opening is turned off while the engine 10 is running and the hybrid vehicle 1 is in motion, the ECU 100 executes a fuel cut that stops the fuel injection from the in-cylinder injection valve 41d and the port injection valve 41p of the engine 10. As a result, the output torque of the engine 10 becomes a negative value, and the hybrid vehicle 1 can be decelerated. Also, during the execution of the fuel cut, air (oxygen) is supplied to the GPF 44, and the PM deposited on the GPF 44 burns.

[0031] Also, as will be described in detail later, the ECU 100 restricts or permits the fuel cut based on the establishment or non-establishment of a predetermined condition. When the fuel cut is restricted, the engine 10 cannot ensure a deceleration. When turning control is executed in such a case, it is necessary to increase the regeneration torque of the first MG 14 and the second MG 15, and there is a risk that the loads on the first MG 14 and the second MG 15 will increase. Therefore, the ECU 100 executes the following deceleration limit control.

[0032] [Deceleration Limit Control Executed by ECU] FIG. 3 is a flowchart showing an example of the deceleration limit control executed by the ECU 100. This control is repeatedly executed at a predetermined cycle with the ignition on. First, the ECU 100 predicts whether the GPF 44 will overheat due to the execution of the fuel cut while the engine 10 is running (step S1). Specifically, the prediction of whether the GPF 44 will overheat is made as follows. The ECU 100 calculates the time during which the GPF 44 can continue the fuel cut (hereinafter referred to as the fuel cut possible time). When the fuel cut possible time is equal to or greater than the threshold value, the ECU 100 predicts that the GPF 44 will not overheat. When the fuel cut possible time is less than the threshold value, the ECU 100 predicts that the GPF 44 will overheat. Step S1 is an example of the process executed by the overheating prediction unit.

[0033] The ECU 100 calculates the fuel cuttable time with reference to the map in FIG. 4 based on the PM deposition amount at the GPF 44 and the temperature of the GPF 44. FIG. 4 is an example of a map defining the fuel cuttable time. This map is calculated in advance based on experimental results or simulation results and is stored in advance in the ROM of the ECU 100. The horizontal axis indicates the PM deposition amount, and the vertical axis indicates the temperature of the GPF 44. FIG. 4 shows the fuel cuttable times T1, T2, and T3. The fuel cuttable time T1 is shorter than each of the fuel cuttable times T2 and T3. The fuel cuttable time T3 is longer than each of the fuel cuttable times T1 and T2. As shown in FIG. 4, when the PM deposition amount is large, the calculated fuel cuttable time is a shorter value than when it is small. The reason for this is that the larger the PM deposition amount, the larger the amount of PM oxidized per unit time when oxygen flows into the GPF 44, and the shorter the time until the temperature of the GPF 44 reaches the upper limit value. Also, when the temperature of the GPF 44 is high, the calculated fuel cuttable time is a shorter value than when it is low. The reason for this is that the higher the temperature of the GPF 44, the shorter the time until the temperature of the GPF 44 reaches the upper limit value.

[0034] The PM deposition amount of the GPF 44 is calculated based on, for example, the engine rotation speed, the filling efficiency, and the temperature of the cooling water. The filling efficiency is calculated based on the engine rotation speed and the intake air amount. The engine rotation speed is calculated based on the detection value of the crank angle sensor 73. The intake air amount is calculated based on the detection value of the air flow meter 74. The temperature of the cooling water is calculated based on the detection value of the water temperature sensor 72.

[0035] The temperature of the GPF 44 is calculated based on, for example, the engine rotation speed and the filling efficiency. However, the calculation methods for the PM deposition amount of the GPF 44 and the temperature of the GPF 44 are not limited to this. For example, the PM deposition amount may be calculated based on the pressure difference before and after the GPF 44. Also, the temperature of the GPF 44 may be calculated based on the detection value of a temperature sensor. Alternatively, these may be calculated by known methods.

[0036] If the answer in step S1 is No, the ECU 100 permits fuel cut (step S2). Specifically, the ECU 100 turns off the fuel cut limit flag. In this embodiment, when the fuel cut limit flag is off, fuel cut is executed for all cylinders 30 based on the fuel cut request.

[0037] If the answer in step S1 is Yes, the ECU 100 causes the display unit 80 to display that the deceleration is suppressed to notify the driver (step S3). Thereby, the driver can be notified in advance that the deceleration will be suppressed due to the limitation of fuel cut described later, and the driver can be prevented from feeling uncomfortable due to the non - execution of fuel cut. Step S3 is an example of the process executed by the notification control unit.

[0038] Next, the ECU 100 suppresses the deceleration (step S4). The suppression of the deceleration may be realized, for example, by changing the upper limit value of the deceleration to a smaller value, or by multiplying the deceleration by a coefficient less than 1 to correct the deceleration to a smaller value.

[0039] Next, the ECU 100 limits the fuel cut (step S5). That is, the ECU 100 turns on the fuel cut limit flag. In this embodiment, when the fuel cut limit flag is on, even if there is a fuel cut request, fuel cut is not executed for all cylinders 30. That is, fuel injection continues in all cylinders 30.

[0040] Next, the ECU 100 determines whether or not the turning control is being executed (step S6). If the answer in step S6 is No, this control ends.

[0041] If the answer in step S6 is Yes, the ECU 100 limits the deceleration that should increase due to the execution of the turning control (step S7). That is, since the fuel cut is restricted, the deceleration during the execution of the turning control is restricted to be lower than the deceleration during the execution of the turning control when the fuel cut is permitted.

[0042] The deceleration limit may be achieved, for example, by changing the upper limit value of the deceleration during fuel cut permission and turning control execution to a smaller value. Also, the deceleration limit may be achieved by multiplying the deceleration during fuel cut permission and turning control execution by a coefficient less than 1 to correct the deceleration to a smaller value. Step S7 is an example of the process executed by the deceleration limit section.

[0043] By limiting the deceleration in this way, in order to ensure a high deceleration in a state where fuel cut is restricted, it is possible to suppress an increase in the regeneration torque in the first MG14 and the second MG15 and an increase in their loads. Also, overcharging of the battery 18 due to the regenerative power of the first MG14 and the second MG15 can be avoided. Furthermore, due to the mechanism of the CVT52, in order to ensure a high deceleration, it is necessary to rotate the first MG14 at a high speed, but such over-rotation of the first MG14 can also be avoided.

[0044] In addition, the deceleration during fuel cut permission and turning control execution is set to be higher than the deceleration during fuel cut permission and turning control stop. The deceleration limit during fuel cut permission and turning control execution can be achieved by reducing the filling efficiency and increasing the engine rotation speed compared to the case where fuel cut is restricted and turning control is stopped. Even when fuel cut is restricted, at least turning control is being executed. Therefore, by having a higher deceleration during turning control execution than during turning control stop, it is possible to avoid giving the driver a sense of discomfort.

[0045] Also, the deceleration during fuel cut permission and turning control execution is restricted to be lower than the deceleration during fuel cut permission and turning control stop. If the deceleration during fuel cut permission and turning control execution is made equal to the deceleration during fuel cut permission and turning control stop, there is a possibility that the loads on the first MG14 and the second MG15 will increase as described above. Note that the respective decelerations during and after the execution of the above deceleration control indicate the deceleration when the shift range is in the D range.

[0046] The deceleration during fuel cut being restricted and turning control being executed is restricted to be lower than the deceleration during fuel cut being permitted and turning control being stopped, but is not limited thereto. The deceleration during fuel cut being restricted and turning control being executed may be equal to or higher than the deceleration during fuel cut being permitted and turning control being stopped. Considering the load tolerance of the first MG14 and the second MG15, the charge capacity of the battery 18, etc., the deceleration during fuel cut being restricted and turning control being executed may be set as appropriate.

[0047] In the above embodiment, as an example of the restriction of fuel cut, the case where fuel cut is restricted for all the cylinders 30 of the engine 10, that is, the case where fuel injection is continued in all the cylinders 30, was described, but it is not limited thereto. For example, fuel cut may be restricted only for some of the cylinders 30. In this case, fuel injection is continued in some of the cylinders 30 and fuel cut is executed in the remaining cylinders 30. Even in this case, compared with the case where fuel cut is executed for all the cylinders 30, the deceleration is suppressed, the amount of oxygen supplied to the GPF 44 is also suppressed, and overheating of the GPF 44 can be suppressed.

[0048] In the above embodiment, the hybrid vehicle 1 including the engine 10, the first MG14, and the second MG15 as the driving power source was described as an example, but the hybrid vehicle is not limited thereto. For example, a hybrid vehicle including an engine as the driving power source and one motor arranged on the power transmission path from the engine to the wheels may be used.

[0049] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0050] 10 Engine 14 First Motor Generator 15 Second Motor Generator 44 GPF (Filter) 100 ECU (Control Device for Hybrid Vehicle, Deceleration Control Unit, Fuel Cut Control Unit, Turning Control Unit, Deceleration Limitation Unit, Overheating Temperature Prediction Unit, Notification Control Unit)

Claims

1. A control device for a hybrid vehicle, comprising: a deceleration control unit that controls an engine and a motor, which are driving power sources, to control the deceleration of the hybrid vehicle; a fuel cut control unit that restricts or permits fuel cut in the engine based on the establishment or non-establishment of a predetermined condition; a turning control unit that executes turning control to increase the deceleration during turning travel of the hybrid vehicle compared to straight-ahead travel; a deceleration limiting unit that limits the deceleration during execution of the turning control when fuel cut is restricted to be lower than the deceleration during execution of the turning control when fuel cut is permitted; A control device for a hybrid vehicle, comprising the above components.

2. The control device for a hybrid vehicle according to claim 1, wherein the deceleration limiting unit limits the deceleration during execution of the turning control when fuel cut is restricted to be higher than the deceleration during execution of the turning control when fuel cut is restricted and the turning control is stopped.

3. The control device for a hybrid vehicle according to claim 2, wherein the deceleration limiting unit limits the deceleration during execution of the turning control when fuel cut is restricted to be lower than the deceleration during execution of the turning control when fuel cut is permitted and the turning control is stopped.

4. Comprising an over-temperature prediction unit that predicts whether a filter that collects particulate matter in the exhaust of the engine will overheat due to execution of fuel cut, The fuel cut control unit restricts fuel cut assuming that the predetermined condition is established when it is predicted that the filter will overheat, and permits fuel cut assuming that the predetermined condition is not established when it is predicted that the filter will not overheat. The control device for a hybrid vehicle according to any one of claims 1 to 3.

5. The control device for a hybrid vehicle according to any one of claims 1 to 3, comprising a notification control unit that causes a notification unit to notify that the deceleration is restricted when fuel cut is restricted.

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