Control device for a hybrid vehicle

Abstract

To provide a control device of a hybrid vehicle, the control device enabling suppression of increase of loads on a motor.SOLUTION: A control device of a hybrid vehicle is provided, comprising: a deceleration control portion which controls an engine and a motor which are power sources for vehicle travelling, to thereby control 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 travelling mode selecting portion which selects either of a first travelling mode and a second travelling mode in which the deceleration higher than in the first travelling mode is required; and a deceleration control portion which restricts the deceleration in such a manner that the deceleration in a case where the fuel cut is restricted and the second travelling mode is selected becomes lower than the deceleration in a case where the fuel cut is permitted and the second travelling mode is selected.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 ensure 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 fuel cut is restricted, the deceleration decreases. In such a case, a driving mode requiring a high deceleration may be selected. When fuel cut is restricted and a driving mode requiring a high deceleration is selected, it is conceivable to ensure 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 is a control device for a hybrid vehicle, which includes a deceleration control unit that controls an engine and a motor as 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 driving mode selection unit that selects either a first driving mode or a second driving mode in which a deceleration higher than that of the first driving mode is required, and a deceleration restriction unit that restricts the deceleration when fuel cut is restricted and the second driving mode is selected to be lower than the deceleration when fuel cut is permitted and the second driving mode is selected. When fuel cut is restricted, a notification control unit that causes a notification unit to notify that the deceleration is restricted This can be achieved by a control device for a hybrid vehicle provided with the above components.

[0007] The deceleration restriction unit may restrict the deceleration when fuel cut is restricted and the second driving mode is selected to be higher than the deceleration when fuel cut is restricted and the first driving mode is selected.

[0008] The deceleration restriction unit may restrict the deceleration when fuel cut is restricted and the second driving mode is selected to be lower than the deceleration when fuel cut is permitted and the first driving mode is selected.

[0009] The device includes a temperature overshoot prediction unit that predicts whether a filter that collects particulate matter in the exhaust of the engine will overheat due to the execution of fuel cut. The fuel cut control unit restricts fuel cut by considering that the predetermined condition is established when it is predicted that the filter will overheat, and permits fuel cut by considering that the predetermined condition is not established when it is predicted that the filter will not overheat.

Advantages of the Invention

[0011] According to the present invention, a control device for a hybrid vehicle that suppresses an increase in the load on 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 a hybrid vehicle 1 according to the present 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 driving power sources for the hybrid vehicle 1 to travel.

[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 reduction mechanism 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 reduction mechanism 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. As a result, the speed reduction mechanism 52 switches between a plurality of power transmission states. The plurality of power transmission states include the N (Neutral) range, D (Drive) range, R (Reverse) range, and P (Parking) range. In the N range, power transmission to the drive wheels 53 is blocked. 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 blocked and the rotation of the output shaft of the speed reduction mechanism 52 is mechanically prevented. The range of the speed reduction mechanism 52 can be switched by manual operation of the shift lever 90 by the driver. Incidentally, 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 driving control, and a memory in which control programs and data are stored. The ECU 100 is an example of a control device for the hybrid vehicle 1, and specifically functionally realizes a deceleration control unit, a fuel cut control unit, a driving mode selection unit, a deceleration limit unit, an overheating prediction unit, and a notification control unit, which will be described later in detail.

[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 fuel cut being restricted. Incidentally, 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] The ECU 100 receives 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, and an accelerator opening sensor 76. The water temperature sensor 72 detects the temperature of the cooling water of the engine 10. The crank angle sensor 73 detects the engine rotational speed, which is the rotational 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.

[0022] The power mode switch S1 and the economy mode switch S2 are provided at positions operable by the driver. The ECU 100 receives signals from the power mode switch S1 and the economy mode switch S2. When the power mode switch S1 is on, the ECU 100 selects the power mode as the driving mode. When the economy mode switch S2 is on, the ECU 100 selects the economy mode as the driving mode. When both the power mode switch S1 and the economy mode switch S2 are off, the ECU 100 selects the normal mode as the driving mode.

[0023] In the power mode, driving is performed with priority given to power performance over fuel consumption performance compared to the normal mode, and the acceleration and deceleration of the hybrid vehicle 1 are higher than those in the normal mode. In the economy mode, driving is performed with priority given to fuel consumption performance over power performance compared to the normal mode, and the acceleration and deceleration are lower than those in the normal mode. Acceleration is the increase in vehicle speed per unit time. Deceleration is the decrease in vehicle speed per unit time. The normal mode is an example of the first driving mode. The power mode is an example of the second driving mode.

[0024] 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 the target acceleration or the 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.

[0025] [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.

[0026] An in-cylinder injection valve 41d is provided in the cylinder 30. The in-cylinder injection valve 41d injects fuel directly into the cylinder 30. A port injection valve 41p that injects fuel toward the intake port 35p is provided in the intake passage 35. An ignition device 42 that ignites the air-fuel mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41d and the port injection valve 41p by spark discharge is provided in each cylinder 30. Note that at least one of the in-cylinder injection valve 41d and the port injection valve 41p may be provided.

[0027] The intake passage 35 is connected to the intake port 35p of each cylinder 30 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of each cylinder 30 via the exhaust valve 38. An air flow meter 74 and a throttle valve 40 that controls the intake air amount are provided in the intake passage 35.

[0028] In the exhaust passage 37, a three-way catalyst 43 and a GPF (Gasoline Particulate Filter) 44 are provided from the upstream side. The three-way catalyst 43 contains catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has an oxygen storage capacity, and purifies NOx, HC, and CO.

[0029] The GPF 44 is a porous ceramic structure that collects exhaust particulates (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. Further, a noble metal such as platinum is supported on the GPF 44. During regeneration control, this noble metal promotes the oxidation reaction of the deposited PM. The GPF 44 is an example of a filter. When the engine 10 is a diesel engine, for example, a DPF (Diesel Particulate Filter) is provided instead of the GPF 44.

[0030] The throttle valve 40 can increase or decrease the amount of intake air introduced into the cylinder 30 by increasing or decreasing its opening degree. The opening degree of the throttle valve 40 is controlled according to the required opening degree from the ECU 100.

[0031] 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. Thereby, 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.

[0032] Further, as will be described in detail later, the ECU 100 restricts or permits fuel cut based on the establishment or non - establishment of a predetermined condition. When the fuel cut is restricted, the engine 10 cannot ensure deceleration. When the power mode is selected as the driving mode in such a case, it is necessary to increase the regenerative 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.

[0033] [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 fuel cut while the engine 10 is being driven (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 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 over - temperature prediction unit.

[0034] 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 and 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 fuel cuttable time is calculated to be 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 fuel cuttable time is calculated to be 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.

[0035] 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.

[0036] The temperature of the GPF 44 is calculated based on, for example, the engine rotation speed and the filling efficiency. However, the calculation methods of 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.

[0037] 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.

[0038] If the answer in step S1 is Yes, the ECU 100 causes the display unit 80 to display that the deceleration is suppressed and notifies the driver (step S3). Thereby, the driver can be notified in advance that the deceleration will be suppressed due to the subsequent fuel cut limitation, and it is possible to avoid giving the driver a sense of discomfort due to the non - execution of the fuel cut. Step S3 is an example of the process executed by the notification control unit.

[0039] 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.

[0040] 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.

[0041] Next, the ECU 100 determines whether the driving mode is selected as the power mode (step S6). If the answer in step S6 is No, this control ends.

[0042] If the answer in step S6 is Yes, the ECU 100 limits the deceleration that should increase due to the selection of the power mode (step S7). That is, when the fuel cut is limited and the power mode is selected, the deceleration is limited to be lower than the deceleration when the fuel cut is permitted and the power mode is selected.

[0043] The deceleration limit may be achieved, for example, by changing the upper limit value of the deceleration when fuel cut is permitted and a power mode is selected to a smaller value. Also, the deceleration limit may be achieved by multiplying the deceleration when fuel cut is permitted and a power mode is selected 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 limiting unit.

[0044] 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 speed reduction mechanism 52, 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.

[0045] In addition, the deceleration when fuel cut is restricted and a power mode is selected is set to be higher than the deceleration when fuel cut is restricted and a normal mode is selected. The deceleration limit when fuel cut is restricted and a power mode is selected can be achieved by reducing the filling efficiency and increasing the engine rotational speed compared to when fuel cut is restricted and a normal mode is selected. Since at least a power mode is selected even when fuel cut is restricted, by having a higher deceleration than when a normal mode is selected, it is possible to avoid giving the driver a sense of discomfort.

[0046] Also, when fuel cut is restricted and a power mode is selected, the deceleration is restricted to be lower than the deceleration when fuel cut is permitted and a normal mode is selected. If the deceleration when fuel cut is restricted and a power mode is selected is made equal to the deceleration when fuel cut is permitted and a normal mode is selected, there is a risk that the loads on the first MG14 and the second MG15 will increase as described above. Incidentally, the respective decelerations in the above power mode and normal mode indicate the decelerations when the shift range is in the D range.

[0047] In step S7 described above, the deceleration is restricted, but the increase in acceleration may also be restricted. As a result, both the deceleration and the acceleration are restricted, so it is possible to avoid giving the driver a sense of discomfort due to the imbalance between the deceleration and the acceleration.

[0048] The deceleration when fuel cut is restricted and a power mode is selected is restricted to be lower than the deceleration when fuel cut is permitted and a normal mode is selected, but it is not limited to this. The deceleration when fuel cut is restricted and a power mode is selected may be equal to or higher than the deceleration when fuel cut is permitted and a normal mode is selected. Considering the load tolerance of the first MG14 and the second MG15, the charge capacity of the battery 18, etc., the deceleration when fuel cut is restricted and a power mode is selected may be set appropriately.

[0049] In the above embodiment, the normal mode is described as the first driving mode and the power mode is described as the second driving mode, but it is not limited to this. For example, the first driving mode may be an economy mode, and the second driving mode may be a power mode or a normal mode.

[0050] In the above embodiment, as an example of the restriction of fuel cut, when fuel cut is restricted for all cylinders 30 of the engine 10, that is, when fuel injection is continued in all cylinders 30, this has been described but 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 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.

[0051] In the above embodiment, the hybrid vehicle 1 including the engine 10, the first MG 14, and the second MG 15 as the driving power source has been 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 disposed on the power transmission path from the engine to the wheels may also be used.

[0052] 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

[0053] 10 Engine 14 First Motor Generator 15 Second Motor Generator 44 GPF (Filter) 100 ECU (Control Device of Hybrid Vehicle, Deceleration Control Unit, Fuel Cut Control Unit, Travel Mode Selection Unit, Deceleration Limitation Unit, Overheating Prediction Unit, Notification Control Unit)

Claims

Claim 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 whether a predetermined condition is satisfied or not; a driving mode selection unit that selects either a first driving mode or a second driving mode in which a deceleration higher than that in the first driving mode is required; a deceleration limiting unit that limits the deceleration when fuel cut is restricted and the second driving mode is selected to be lower than the deceleration when fuel cut is permitted and the second driving mode is selected; a notification control unit that causes the notification unit to notify that the deceleration is limited when fuel cut is restricted; A control device for a hybrid vehicle, comprising the above components. Claim 2 The control device for a hybrid vehicle according to claim 1, wherein the deceleration limiting unit limits the deceleration when fuel cut is restricted and the second driving mode is selected to be higher than the deceleration when fuel cut is restricted and the first driving mode is selected. Claim 3 The control device for a hybrid vehicle according to claim 2, wherein the deceleration limiting unit limits the deceleration when fuel cut is restricted and the second driving mode is selected to be lower than the deceleration when fuel cut is permitted and the first driving mode is selected. Claim 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 the execution of fuel cut; The fuel cut control unit restricts fuel cut assuming that the predetermined condition is satisfied when it is predicted that the filter will overheat, and permits fuel cut assuming that the predetermined condition is not satisfied 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.

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