Control device for a hybrid vehicle

Abstract

The present application relates to a control device for a hybrid vehicle, the control device including: a deceleration control unit configured to control an engine and a motor as travel power sources to control a deceleration of the hybrid vehicle; a fuel cut control unit configured to limit or allow fuel cut in the engine based on presence or absence of a predetermined condition; a turning control unit configured to execute turning control for increasing the deceleration during turning to be higher than the deceleration during straight running; and a deceleration limit unit configured to limit the deceleration in a case where the fuel cut is limited and the turning control is executed to be lower than the deceleration in a case where the fuel cut is allowed and the turning control is executed.

Description

Technical Field

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

[0002] In hybrid vehicles, deceleration is ensured by performing fuel cut-off (see, for example, Japanese Patent Application Publication No. 2017-177823).

[0003] Fuel cutoff can be limited based on predetermined conditions. When fuel cutoff is limited, deceleration decreases. In such a case, cornering control requiring high deceleration can be implemented. When fuel cutoff is limited and cornering control requiring high deceleration is implemented, it is conceivable to ensure high deceleration by increasing the regenerative torque of the motor. However, in this case, the load on the motor may increase. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide a control device for hybrid vehicles that suppresses the increase of motor load.

[0005] The aforementioned objective is achieved by a control device for a hybrid vehicle, the control device comprising: a deceleration control unit configured to control an engine and an electric motor, which serve as driving power sources, to control the deceleration of the hybrid vehicle; a fuel cut-off control unit configured to limit or allow fuel cut-off in the engine based on the fulfillment or non-fulfillment of predetermined conditions; a cornering control unit configured to perform cornering control to increase the deceleration during cornering to a higher level than the deceleration during straight-line driving; and a deceleration limiting unit configured to limit the deceleration when fuel cut-off is limited and the cornering control is performed to a lower level than when fuel cut-off is allowed and the cornering control is performed.

[0006] The deceleration limiting unit can be configured to set the deceleration when fuel cut-off is restricted and the cornering control is executed to be higher than the deceleration when fuel cut-off is restricted and the cornering control is stopped.

[0007] The deceleration limiting unit can be configured to limit the deceleration when fuel cut-off and the cornering control are restricted to a lower level than when fuel cut-off and the cornering control are permitted.

[0008] The control device may further include an overheating prediction unit configured to predict whether the temperature of the filter collecting particulate matter in the engine exhaust will rise excessively due to the execution of fuel cut-off, wherein the fuel cut-off control unit may be configured to limit fuel cut-off when a predetermined condition is met if the temperature of the filter is predicted to rise excessively, and to allow fuel cut-off when the predetermined condition is not met if the temperature of the filter is predicted not to rise excessively.

[0009] The control device may further include a notification control unit configured to notify that deceleration is limited when fuel cutoff is restricted.

[0010] Effects of the present invention

[0011] According to the present invention, a control device for hybrid vehicles that suppresses the increase of motor load can be provided. Attached Figure Description

[0012] Figure 1 This is a schematic structural diagram of a hybrid vehicle according to an embodiment of the present invention.

[0013] Figure 2 This is a schematic structural diagram of an engine.

[0014] Figure 3 This is a flowchart illustrating an example of deceleration limit control performed by an ECU;

[0015] Figure 4 This is an example of a graph that defines the duration of fuel cutoff. Detailed Implementation

[0016] [Schematic structure of a hybrid vehicle]

[0017] Figure 1 This is a schematic structural diagram of a hybrid vehicle 1 according to an embodiment of the present invention. The hybrid vehicle 1 includes an electronic control unit (ECU) 100, an engine 10, a first electric generator (hereinafter referred to as the first MG) 14, a second electric generator (hereinafter referred to as the second MG) 15, a power control unit (PCU) 17, a battery 18, a power distribution mechanism 50, a transmission mechanism 51, a reduction mechanism 52, and drive wheels 53. The engine 10 is, but is not limited to, a gasoline engine, and may also be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are the driving power sources for the hybrid vehicle 1.

[0018] Each of the first MG 14 and the second MG 15 functions as an electric motor that outputs torque when supplied with drive power, and as a generator that produces regenerative power when torque is applied. Specifically, the first MG 14 and the second MG 15 are alternating current rotating motors. An alternating current rotating motor is, for example, a permanent magnet synchronous motor in which permanent magnets are embedded in the rotor.

[0019] 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 from the battery 18 and supplies it to the first and second inverters, and stepps down 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 into AC power and supplies it to the first MG 14, and converts AC power from the first MG 14 into DC power and supplies it to the converter. The second inverter converts DC power from the converter into AC power and supplies it to the second MG 15, and converts AC power from the second MG 15 into DC power and supplies it to the converter. That is, the PCU 17 uses the regenerated power generated by the first MG 14 or the second MG 15 to charge the battery 18, and uses the charged power from the battery 18 to drive the first MG 14 or the second MG 15.

[0020] Battery 18 comprises multiple stacked batteries. These batteries are, for example, secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries.

[0021] The power distribution 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 distribution mechanism 50. The power distribution mechanism 50 is, for example, a planetary gear mechanism including a sun gear, planet carrier, pinion, and ring gear. The output shaft of the power distribution mechanism 50 is connected to the transmission mechanism 51. The rotating shaft of the second MG 15 is also connected to the transmission mechanism 51. The transmission mechanism 51 is connected to the reduction mechanism 52, and the driving forces of the engine 10, the first MG 14, and the second MG 15 are transmitted to the drive wheels 53 via the transmission mechanism 51 and the reduction mechanism 52.

[0022] The reduction gear 52 is a multi-stage automatic transmission that changes the gear ratio by altering the gear ratio under the control of the ECU 100. As a result, the reduction gear 52 switches between multiple drive force transmission states. These drive force transmission states include neutral (N), drive (D), reverse (R), and park (P). In N, drive force transmission to the drive wheels 53 is cut off. In D, forward movement is possible. In R, reverse movement is possible. In P, drive force transmission to the drive wheels 53 is cut off, and rotation of the output shaft of the reduction gear 52 is mechanically prevented. The gears of the reduction gear 52 are switched manually by the driver using the gear lever 90. Instead of the reduction gear 52, a continuously variable transmission (CVT) that continuously changes the gear ratio can be used.

[0023] ECU 100 is an electronic control unit that includes arithmetic processing circuitry that performs various arithmetic operations related to vehicle driving control, as well as a memory that stores control programs and data. ECU 100 is an example of a control device for a hybrid vehicle 1, and functions as a deceleration control unit, fuel cut-off control unit, cornering control unit, deceleration limiting unit, overheat prediction unit, and notification control unit, which will be described in detail later.

[0024] A display unit 80 is provided on the dashboard of the hybrid vehicle 1. The display unit 80, which will be described in detail later, is an example of a notification unit that informs the hybrid vehicle 1 that its deceleration is suppressed due to fuel cut-off restrictions. Note that instead of the display unit 80, for example, a speaker from the audio system of the hybrid vehicle 1, a navigation system, etc., could be used.

[0025] Signals from the ignition switch 71, coolant temperature sensor 72, crank angle sensor 73, air flow meter 74, shift position sensor 75, accelerator pedal opening sensor 76, and yaw rate sensor 77 are input to the ECU 100. The coolant temperature sensor 72 detects the coolant temperature of the engine 10. The crank angle sensor 73 detects the engine speed, which is the crankshaft speed of the engine 10. The air flow meter 74 detects the amount of air entering the engine 10. The shift position sensor 75 detects the operating position of the shift lever 90. The accelerator pedal opening sensor 76 detects the operating position of the accelerator pedal 91. The yaw rate sensor 77 detects the angular velocity (yaw rate) of the hybrid vehicle 1 about its vertical axis.

[0026] ECU 100 controls acceleration and deceleration based on accelerator operation parameters. Specifically, the outputs of engine 10, first MG 14, and second MG 15 are each controlled to achieve a target acceleration or deceleration set based on the accelerator operation parameters. The output of engine 10 is controlled by the intake air volume and fuel injection volume. The outputs of first MG 14 and second MG 15 are each controlled by PCU 17. The above control is an example of a process performed by the deceleration control unit.

[0027] ECU 100 performs cornering control based on the detection results of yaw rate sensor 77. Compared to the deceleration of hybrid vehicle 1 when traveling straight, cornering control increases the deceleration of hybrid vehicle 1 when cornering. Specifically, ECU 100 controls the deceleration such that the actual yaw rate during cornering becomes the target yaw rate. The target yaw rate is determined such that the square root of the sum of the squares of the front and rear driving forces of hybrid vehicle 1 and the squares of its lateral forces is less than or equal to the radius of the friction circle of hybrid vehicle 1. The radius of the friction circle of hybrid vehicle 1 is calculated by multiplying the coefficient of friction of the road surface by the vertical load of hybrid vehicle 1. Cornering control is not performed during straight-line travel. This is an example of a process performed by the cornering control unit. Alternatively, cornering control is not limited to the above configuration and can also be performed based on the detection results of a lateral acceleration sensor that detects the lateral acceleration of hybrid vehicle 1. In this case, for example, the greater the lateral acceleration detected by the lateral acceleration sensor, the greater the deceleration.

[0028] [Schematic diagram of an engine]

[0029] Figure 2 This is a schematic structural diagram of engine 10. Engine 10 has cylinder 30, piston 31, connecting rod 32, crankshaft 33, intake passage 35, intake valve 36, exhaust passage 37 and exhaust valve 38. Figure 2 Only one of the multiple cylinders 30 of the engine 10 is shown. An air-fuel mixture is burned within the cylinder 30. A piston 31 is housed within each cylinder 30 for reciprocating motion and is connected via a connecting rod 32 to a crankshaft 33, which serves as the output shaft of the engine 10. The connecting rod 32 and the crankshaft 33 convert the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0030] Cylinder 30 is equipped with an in-cylinder injection valve 41d. The in-cylinder injection valve 41d injects fuel directly into cylinder 30. Intake passage 35 is equipped with a port injection valve 41p that injects fuel toward intake port 35p. Each cylinder 30 is equipped with an ignition device 42 that emits an electric spark to ignite the mixture of intake air introduced through intake passage 35 and fuel injected by in-cylinder injection valve 41d and port injection valve 41p. At least one of in-cylinder injection valve 41d and port injection valve 41p can be provided.

[0031] The intake passage 35 is connected to the intake port 35p of the cylinder 30 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of the cylinder 30 via the exhaust valve 38. The intake passage 35 is equipped with the aforementioned air flow meter 74 and a throttle valve 40 for controlling the intake air volume.

[0032] A three-way catalyst 43 and a gasoline particulate filter (GPF) 44 are sequentially arranged from the upstream side in the exhaust passage 37. The three-way catalyst 43 contains catalytic metals such as platinum (Pt), palladium (Pd) and rhodium (Rh), has oxygen storage capacity, and purifies NOx, HC and CO.

[0033] GPF 44 is a porous ceramic structure that collects exhaust particulate matter (hereinafter referred to as PM) from the exhaust gas. Furthermore, GPF 44 contains a precious metal, such as platinum. In regeneration control, this precious metal accelerates the oxidation reaction of accumulated PM. GPF 44 is an example of a filter. Alternatively, for example, when engine 10 is a diesel engine, a diesel particulate filter (DPF) is used instead of GPF 44.

[0034] Increasing or decreasing the opening of the throttle valve 40 will increase or decrease the intake air volume into cylinder 30. The opening of the throttle valve 40 is controlled according to the opening required by the ECU 100.

[0035] While the hybrid vehicle 1 is in motion, the ECU 100 performs fuel cut-off when the engine 10 is running and the accelerator pedal opening is zero, stopping fuel injection from the in-cylinder injection valve 41d and port injection valve 41p of the engine 10. As a result, the output torque of the engine 10 becomes negative, and the hybrid vehicle 1 decelerates. Furthermore, during the execution of the fuel cut-off, air (oxygen) is supplied to the GPF 44, thus causing the PM accumulated in the GPF 44 to burn.

[0036] Furthermore, ECU 100 limits or allows fuel cutoff based on the fulfillment or non-fulfillment of predetermined conditions, which will be described in detail later. When fuel cutoff is limited, engine 10 cannot ensure deceleration. When cornering control is performed in this situation, the regenerative torque of the first MG 14 and the second MG 15 needs to be increased, which may increase the load on the first MG 14 and the second MG 15. Therefore, ECU 100 performs the following deceleration limiting control.

[0037] [Deceleration limit control performed by the ECU]

[0038] Figure 3This is a flowchart illustrating an example of deceleration limiting control performed by ECU 100. This control is repeatedly executed at predetermined intervals during ignition turn-on. First, ECU 100 predicts whether the temperature of GPF 44 will rise excessively due to fuel cut-off during engine 10 operation (step S1). Specifically, the prediction of whether the temperature of GPF 44 will rise excessively is made as follows: ECU 100 calculates the fuel cut-off duration for which GPF 44 can withstand fuel cut-off. When the fuel cut-off duration is equal to or longer than a threshold, ECU 100 predicts that the temperature of GPF 44 will not rise excessively. When the fuel cut-off duration is less than the threshold, ECU 100 predicts that the temperature of GPF 44 will rise excessively. Step S1 is an example of the processing performed by the overheating prediction unit.

[0039] ECU 100 is based on the PM buildup in GPF 44 and the temperature reference of GPF 44. Figure 4 The graph is used to calculate the fuel cut-off duration. Figure 4 This is an example of a graph defining the fuel cutoff duration. This graph, pre-calculated based on experimental and simulation results, is stored in the ROM of the ECU 100. The horizontal axis represents PM buildup. The vertical axis represents the temperature of GPF44. Figure 4 The fuel cutoff durations T1, T2, and T3 are shown. Fuel cutoff duration T1 is shorter than each of fuel cutoff durations T2 and T3. Fuel cutoff duration T3 is longer than each of fuel cutoff durations T1 and T2. Figure 4 As shown, the fuel cutoff duration is calculated to be smaller when PM accumulation is high compared to when PM accumulation is low. This is because the increased PM accumulation results in a higher amount of PM being oxidized per unit time when oxygen flows into GPF 44, thus shortening the time required for GPF 44 to reach its upper temperature limit. Furthermore, the fuel cutoff duration is calculated to be shorter when GPF 44 temperature is high than when temperature is low. This is because the higher the GPF 44 temperature, the shorter the time it takes for GPF 44 to reach its upper temperature limit.

[0040] The PM buildup in GPF 44 is calculated based on factors such as engine speed, filling efficiency, and coolant temperature. Filling efficiency is calculated based on engine speed and intake air volume. Engine speed is calculated based on the reading from crankshaft angle sensor 73. Intake air volume is calculated based on the reading from airflow meter 74. Coolant temperature is calculated based on the reading from coolant temperature sensor 72.

[0041] The temperature of GPF 44 is calculated, for example, based on engine speed and filling efficiency. However, the methods for calculating the PM buildup in GPF 44 and the temperature of GPF 44 are not limited to this. For example, the PM buildup can be calculated based on the pressure difference before and after the GPF 44. Furthermore, the temperature of GPF 44 can be calculated based on the readings from a temperature sensor. These can also be calculated using other known methods.

[0042] If "No" is selected in step S1, ECU 100 allows fuel cutoff (step S2). Specifically, ECU 100 disables the fuel cutoff restriction flag. In this embodiment, when the fuel cutoff restriction flag is OFF, fuel cutoff is performed on all cylinders 30 according to the fuel cutoff requirement.

[0043] If "Yes" is selected in step S1, the ECU 100 displays a notification on the display unit 80 that deceleration has been suppressed to inform the driver (step S3). This notification to the driver can prevent discomfort caused by the failure to perform a fuel cut-off, as deceleration is about to be suppressed due to the fuel cut-off restriction. Step S3 is an example of the process performed by the control unit to notify the driver.

[0044] Next, ECU 100 suppresses deceleration (step S4). Deceleration suppression can be achieved, for example, by changing the upper limit of deceleration to a smaller value, or by multiplying the deceleration by a coefficient less than 1 to correct the deceleration to a smaller value.

[0045] Next, ECU 100 restricts fuel cutoff (step S5). That is, ECU 100 activates the fuel cutoff restriction flag. In this embodiment, when the fuel cutoff restriction flag is ON, even if fuel cutoff is requested, fuel cutoff is not performed on any cylinder 30. That is, fuel injection continues in all cylinders 30.

[0046] Next, ECU 100 determines whether to execute cornering control (step S6). If the result in step S6 is "no", the control ends.

[0047] If "Yes" is selected in step S6, the ECU 100 limits the deceleration required when performing cornering control (step S7). That is, the deceleration when fuel cut-off and cornering control are restricted is limited to a lower deceleration when fuel cut-off and cornering control are permitted.

[0048] For example, the deceleration limit can be changed by altering the upper limit of deceleration when fuel cut-off and cornering control are permitted to a smaller value. Furthermore, the deceleration limit can be adjusted to a smaller value by multiplying the deceleration when fuel cut-off and cornering control are permitted by a coefficient less than 1. Step S7 is an example of a process performed by the deceleration limiting unit.

[0049] By limiting the deceleration in this way, the increase in regenerative torque in the first MG 14 and the second MG 15, which are used to ensure high deceleration during fuel cut-off, and the increase in load on them, are suppressed. Furthermore, overcharging of the battery 18 by the regenerative power of the first MG 14 and the second MG 15 can be prevented. Moreover, although the high speed rotation of the first MG 14 is necessary to ensure high deceleration due to the mechanism of the reduction gear 52, such excessive rotation of the first MG 14 is also avoided.

[0050] The deceleration when fuel cutoff is limited and cornering control is applied is set higher than the deceleration when fuel cutoff is limited and cornering control is stopped. This deceleration limitation is achieved by reducing refueling efficiency and increasing engine speed, compared to the case of limited fuel cutoff and cornering control stopped. Since cornering control is applied even when fuel cutoff is limited, driver discomfort due to higher deceleration than when cornering control is stopped is avoided.

[0051] Furthermore, the deceleration under conditions of limited fuel cut-off and cornering control is limited to be lower than the deceleration under conditions of permitted fuel cut-off and stopped cornering control. This is because if the deceleration under conditions of limited fuel cut-off and cornering control is equal to the deceleration under conditions of permitted fuel cut-off and stopped cornering control, the load on the first MG14 and the second MG15 may increase as described above. The deceleration under the aforementioned conditions of permitted and stopped cornering control refers to the deceleration when the transmission is in D gear.

[0052] The deceleration under conditions of limited fuel cutoff and cornering control is limited to a lower rate than that under conditions of permitted fuel cutoff and cornering control, but is not limited thereto. The deceleration under conditions of limited fuel cutoff and cornering control can be equal to or higher than that under conditions of permitted fuel cutoff and cornering control. Taking into account the load endurance of the first MG 14 and the second MG 15, the charging capacity of the battery 18, etc., the deceleration under conditions of limited fuel cutoff and cornering control can be appropriately set.

[0053] As an example of a limitation on fuel cutoff, the above embodiments have described a case where fuel cutoff is limited to all cylinders 30 of the engine 10, i.e., fuel injection continues in all cylinders 30. However, this configuration is not limited. For example, fuel cutoff may be limited to only one of the cylinders 30. In this case, fuel injection continues in one of the cylinders 30, while fuel cutoff is performed in the other cylinders 30. This is because, also in this case, compared to the case where fuel cutoff is performed on all cylinders 30, deceleration is suppressed, thereby suppressing the amount of oxygen supplied to the GPF 44, and thus suppressing excessive heating of the GPF 44.

[0054] In the above embodiments, a hybrid vehicle 1 including an engine 10, a first MG 14, and a second MG 15 as driving power sources was described as an example, but the hybrid vehicle is not limited to this. For example, it can be a hybrid vehicle including an engine as a driving power source and an electric motor arranged in the power transmission path from the engine to the wheels.

[0055] Although some embodiments of the present invention have been described in detail, the present invention is not limited to these specific embodiments, but can be modified or changed within the scope of the present invention as set forth in the claims.

Claims

1. A control device for a hybrid vehicle, the control device comprising: A deceleration control unit, configured to control the engine and motor, which serve as driving power sources, to control the deceleration of the hybrid vehicle; A fuel cut-off control unit, configured to limit or allow fuel cut-off in the engine based on the fulfillment or non-fulfillment of predetermined conditions; A turning control unit, configured to perform turning control to increase the deceleration during turning to be higher than the deceleration during straight-line driving; and A deceleration limiting unit is configured to limit deceleration to a lower level when fuel cutoff and cornering control are restricted than when fuel cutoff and cornering control are permitted.

2. The control device for a hybrid vehicle according to claim 1, wherein, The deceleration limiting unit is configured to set the deceleration when fuel cut-off is restricted and the cornering control is executed to be higher than the deceleration when fuel cut-off is restricted and the cornering control is stopped.

3. The control device for a hybrid vehicle according to claim 2, wherein, The deceleration limiting unit is configured to limit the deceleration when fuel cut-off and cornering control are restricted to a lower level than when fuel cut-off and cornering control are permitted.

4. The control device for a hybrid vehicle according to any one of claims 1 to 3, further comprising an overheating prediction unit configured to predict whether the temperature of the filter collecting particulate matter in the exhaust of the engine will rise excessively due to the execution of fuel cut-off. in, The fuel cut-off control unit is configured to limit fuel cut-off when a predetermined condition is met if the temperature of the filter is predicted to be excessively high, and is configured to allow fuel cut-off when the predetermined condition is not met if the temperature of the filter is predicted not to be excessively high.

5. The control device for a hybrid vehicle according to any one of claims 1 to 3, further comprising a notification control unit configured to notify that deceleration is limited when fuel cut-off is limited.

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