Vehicle control system

Abstract

To suppress a reduction of the cruising distance due to the power consumption caused by shifting of an automatic transmission when an electric motor is operated by an electric power supplied from a power storage device to cause a vehicle to perform a limp-home running.SOLUTION: During a limp-home running in which an electric motor MG is operated by an electric power supplied from a power storage device, a gear position Gr of an automatic transmission is limited to a limp-home-running gear position Gr1 or a low-speed gear position Gr2 to suppress shifting of the automatic transmission, and therefore it is possible to suppress power consumption caused by control of rotational speed of the electric motor MG for suppressing shifting shock or the like, so as to extend a cruising distance of a vehicle accordingly.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle, and particularly to a technique for operating an electric motor by power supply from a power storage device to perform evacuation running when an engine fails.

Background Art

[0002] There is known a vehicle provided with an engine and an electric motor as driving power sources, and an automatic transmission capable of forming a plurality of gear stages having different gear ratios in a power transmission path between the power source and drive wheels (see Patent Document 1). In such a vehicle, when the engine fails, it is conceivable to operate the electric motor by power supply from a power storage device to perform evacuation running.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a gear shift for switching the gear stage of the automatic transmission is performed during such evacuation running, the power consumption increases due to rotation speed control by the electric motor for suppressing a gear shift shock or the like, and there is a possibility that the cruising distance becomes short.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to suppress a shortening of the cruising distance due to power consumption associated with a gear shift of an automatic transmission when operating an electric motor by power supply from a power storage device to perform evacuation running.

Means for Solving the Problems

[0006] To achieve this objective, the first invention provides (a) an engine and an electric motor as power sources for propulsion. The hydraulic control circuit includes a mechanical oil pump driven by the aforementioned electric motor and an electric oil pump driven by a dedicated pump drive motor, The vehicle is equipped with an automatic transmission capable of forming multiple gear stages with different gear ratios in the power transmission path between the power source and the drive wheels, and the control device for the vehicle is equipped with (b) an escape run control unit that operates the electric motor by supplying power from a power storage device to perform escape run when the engine fails, and (c) the escape run control unit is Depending on the actual gear ratio of the retracted driving gear, the automatic transmission is fixed to a predetermined constant retracted driving gear while the vehicle speed is higher than a predetermined low-speed determination value such that the rotational speed of the electric motor is below a predetermined low-speed determination value such that the amount of oil discharged from the mechanical oil pump is below a certain amount. On the other hand, when the vehicle speed falls below the low-speed determination value, the automatic transmission is downshifted to a predetermined constant low-speed gear with a gear ratio greater than that of the retracted driving gear. The present invention is characterized by restricting the gear changes of the automatic transmission. [Effects of the Invention]

[0009] With this type of vehicle control system, during emergency driving, when the vehicle is powered by an electric motor supplied by a battery, the shifting of the automatic transmission is restricted. This reduces power consumption caused by motor rotation speed control to suppress shifting shocks, etc., and thereby extends the vehicle's driving range. Furthermore, as long as the vehicle speed is higher than a predetermined low-speed threshold that causes the motor's rotational speed to fall below a certain amount of oil discharged from the mechanical oil pump, the automatic transmission gear is fixed to a certain retracted gear. This eliminates power consumption caused by motor rotational speed control during gear changes, thereby appropriately extending the driving range. Furthermore, when the vehicle speed falls below the low-speed threshold, the automatic transmission downshifts to a low-speed gear with a larger gear ratio than the retracted driving gear. This downshift increases the rotational speed of the electric motor regardless of the vehicle speed, and also increases the amount of oil discharged by the mechanical oil pump driven by that electric motor. As a result, it is possible to suppress the operation of the electric oil pump by the amount of oil discharged, thereby reducing power consumption by the electric oil pump and extending the driving range. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating a vehicle drive system equipped with a control device, which is one embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating an example of an automatic transmission found in the vehicle shown in Figure 1. [Figure 3] Figure 2 illustrates the relationship between the multiple gear stages and engagement devices of an automatic transmission. [Figure 4] Figure 1 illustrates an example of a gear shift map that automatically switches the gear positions of an automatic transmission by the gear shift control unit functionally provided in the electronic control unit. [Figure 5] Figure 1 is a flowchart illustrating the operation of the retraction control unit functionally provided by the electronic control unit. [Figure 6] Figure 1 illustrates the torque characteristics of the electric motor installed in the vehicle shown in Figure 1. [Figure 7] Figure 5 illustrates the predetermined relationship when setting the retraction gear stage Gr1 according to the vehicle speed V in step S3. [Figure 8] This diagram illustrates another embodiment of the present invention and is a flowchart corresponding to Figure 5. [Modes for carrying out the invention]

[0012] The present invention is applicable to hybrid vehicles equipped with an engine and an electric motor as power sources. A motor-generator that also functions as a generator is preferably used as the electric motor, but an electric motor that does not function as a generator can also be used. An automatic transmission is provided in the power transmission path between the power source and the drive wheels, but a fluid-type transmission device such as a torque converter may be provided as needed. A stepped transmission such as a planetary gear type or a two-axis mesh type is suitable for the automatic transmission, but a continuously variable transmission such as a belt type can also be applied if the gear ratio is switched in stages like a stepped transmission. The retraction travel control unit is configured, for example, to fix the automatic transmission to a predetermined retraction travel gear stage for driving, but it may also perform gear shift control in a way that reduces the frequency of gear changes, such as by reducing the number of gear stages to be changed. [Examples]

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram illustrating the schematic configuration of the drive system of a vehicle 10 equipped with an electronic control device 90 as a control device according to one embodiment of the present invention, and also illustrates the control functions and key parts of the control system for various controls in the vehicle 10. The vehicle 10 is a hybrid electric vehicle equipped with an engine 12 and an electric motor MG as power sources. The vehicle 10 includes an engine 12, drive wheels 14 which are the left and right rear wheels or front wheels, and a power transmission device 18 provided in the power transmission path between the engine 12 and the drive wheels 14. The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine. The engine torque Te of the engine 12 is controlled by the electronic control device 90 through engine control equipment 22 including a throttle actuator, fuel injection device, ignition device, etc. The electric motor MG is a rotating electric machine that has the function of an engine that generates mechanical power from electric power, and the function of a generator that generates electric power from mechanical power, and is a so-called motor generator. The electric motor (MG) is connected to a high-voltage HEV (Hybrid Electric Vehicle) battery (28) via a PCU (Power Control Unit) (24) which has an inverter, etc. The MG torque (Tmg) of the electric motor (MG) is controlled by the PCU (24) controlled by an electronic control unit (90). The HEV battery (28) is an energy storage device that supplies power to the electric motor (MG).

[0014] The power transmission device 18 is a non-rotating member attached to the vehicle body, and is equipped with a K0 clutch 34, a WSC clutch 36, and an automatic transmission 38 in series from the engine 12 side. Power is transmitted from the transmission output shaft 40 to the drive wheels 14 via a differential gear 42, a pair of drive shafts 44, etc. The K0 clutch 34 is an engagement device that connects and disconnects the engine 12 and the electric motor MG, and is an engine disconnection clutch that disconnects the engine 12 from the power transmission path. The WSC clutch 36 is an engagement device that connects and disconnects the electric motor MG and the drive wheels 14, and functions as a starting clutch and input clutch by being controlled by slip engagement by an electronic control device 90.

[0015] The power transmission device 18 includes an engine connecting shaft 46 that connects the engine 12 and the K0 clutch 34, and an electric motor connecting shaft 48 that connects the K0 clutch 34 and the WSC clutch 36, and an electric motor MG is connected to the electric motor connecting shaft 48 so as to be able to transmit power. Both the K0 clutch 34 and the WSC clutch 36 are wet or dry friction engagement devices composed of multi-plate or single-plate clutches that are pressed by a hydraulic actuator, and the control state, such as engaged state or disengaged state, is switched by the electronic control device 90. The control state of the K0 clutch 34 is switched by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 34, by the K0 hydraulic pressure PRk0 supplied from the hydraulic control circuit 52. The control state of the WSC clutch 36 is switched by changing the WSC torque Twsc, which is the torque capacity of the WSC clutch 36, by the WSC hydraulic pressure PRwsc supplied from the hydraulic control circuit 52. The input side member of the WSC clutch 36 is connected to the motor coupling shaft 48, and the output side member of the WSC clutch 36 is connected to the transmission input shaft 50, which is the input rotating member of the automatic transmission 38.

[0016] The automatic transmission 38 is a known planetary gear type automatic transmission, for example, comprising a plurality of planetary gear systems and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices, for example, consisting of a multi-plate or single-plate clutch or brake pressed by a hydraulic actuator, or a band brake tightened by a hydraulic actuator. Each of the plurality of engagement devices CB has its control state, such as engaged or disengaged, switched by changing its respective torque capacity, the CB torque Tcb, which is supplied by a regulated CB hydraulic pressure PRcb from the hydraulic control circuit 52. The automatic transmission 38 is a stepped transmission in which, when any of the engagement devices CB are engaged, one of a plurality of gear stages Gr with different gear ratios γat (= input rotational speed Ni / output rotational speed No) is formed. The input rotational speed Ni is the rotational speed of the transmission input shaft 50 and is the input rotational speed of the automatic transmission 38. The input rotational speed Ni is also the rotational speed of the output side member of the WSC clutch 36. Output rotational speed No. is the rotational speed of the transmission output shaft 40, and is the output rotational speed of the automatic transmission 38.

[0017] Vehicle 10 includes a mechanical oil pump 58 and an electric oil pump 60. The mechanical oil pump 58 is connected to be capable of power transmission via a transmission device such as a gear, a belt, or a chain to, for example, the motor coupling shaft 48, is rotationally driven by at least one of the engine 12 and the motor MG, and discharges the hydraulic oil used in the power transmission device 18. The electric oil pump 60 is rotationally driven by a dedicated pump drive motor 62 to discharge the hydraulic oil, and can discharge the hydraulic oil at any timing including when the vehicle 10 is stopped. The pump drive motor 62 is powered and operated from the HEV battery 28 of the same high voltage as the motor MG via the PCU 24, but may be powered from a low voltage normal battery such as 12V. The hydraulic oil discharged from the mechanical oil pump 58 and the electric oil pump 60 is supplied to the hydraulic control circuit 52. The hydraulic control circuit 52 outputs, based on the hydraulic oil supplied from the mechanical oil pump 58 and the electric oil pump 60, the regulated CB hydraulic pressure PRcb, K0 hydraulic pressure PRk0, WSC hydraulic pressure PRwsc, etc. respectively.

[0018] FIG. 2 is a schematic diagram for explaining an example of the automatic transmission 38. This automatic transmission 38 is configured to include three sets of planetary gear devices 54, 55, 56, four clutches C1 to C4, and two brakes B1, B2. The clutches C1 to C4 and the brakes B1, B2 correspond to the engagement device CB and are hydraulic friction engagement devices that are engaged by a hydraulic actuator. By engaging these engagement devices CB according to the "○" marks in the engagement operation table shown in FIG. 3, as a plurality of gear stages Gr, eight forward gear stages from the first gear stage "1st" to the eighth gear stage "8th" are established, and a reverse gear stage "Rev" is established. Also, when all the engagement devices CB are released, it becomes neutral "N" that interrupts power transmission. The first gear stage "1st" is a low-speed gear stage with the largest transmission ratio γat, and the transmission ratio γat decreases from the first gear stage "1st" toward the eighth gear stage "8th". The automatic transmission 38 is configured substantially symmetrically with respect to the center line, and in FIG. 2, the lower half of the center line is omitted, and the transmission input shaft 50 and the transmission output shaft 40 are shown on the center line.

[0019] The vehicle 10 includes an electronic control unit 90 as a control device that executes various controls. The electronic control unit 90 is configured to include a so-called microcomputer including, for example, a CPU, a RAM, a ROM, an input / output interface, etc., and executes various controls of the vehicle 10. The electronic control unit 90 is configured to include a plurality of computers such as an engine control computer, an MG control computer, a hydraulic control computer, etc. as necessary.

[0020] The electronic control unit 90 is supplied with signals related to various information necessary for various controls, such as the engine rotation speed Ne, input rotation speed Ni, output rotation speed No, corresponding to the vehicle speed V, the rotation speed Nmg of the electric motor MG, the accelerator opening θacc, which represents the driver's power request amount based on the amount of operation of the accelerator pedal, the throttle valve opening θth, the opening of the electronic throttle valve, the power switch press signal Spw, the battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the HEV battery 28, and the oil temperature THoil, which is the temperature of the hydraulic fluid in the hydraulic control circuit 52. These signals are supplied from, for example, the engine rotation speed sensor 70, input rotation speed sensor 72, output rotation speed sensor 74, MG rotation speed sensor 76, accelerator opening sensor 80, throttle valve opening θth, which is the opening of the electronic throttle valve, the power switch press signal Spw, the battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the HEV battery 28, and the oil temperature THoil, which is the temperature of the hydraulic fluid in the hydraulic control circuit 52. The power switch 84 is an automatic reset push-button switch located near the driver's seat. When pressed by the driver at the start or end of operation of the vehicle 10, a power switch press signal Spw is output, and it is used to switch between Ready OFF, which disables driving by the power source (engine 12, electric motor MG), Ready ON, which enables driving, and Accessory ON, which allows the use of various accessory products.

[0021] The electronic control unit 90 outputs various signals to each device installed in the vehicle 10, such as the engine control equipment 22, PCU 24, and hydraulic control circuit 52. These signals include an engine control command signal Se for controlling the engine 12, an MG control command signal Smg for controlling the electric motor MG, an electric oil pump control command signal Seop for controlling the electric oil pump 60, a CB hydraulic control command signal Scb for controlling the engagement device CB, a K0 hydraulic control command signal Sk0 for controlling the K0 clutch 34, and a WSC hydraulic control command signal Swsc for controlling the WSC clutch 36. The hydraulic control circuit 52 is equipped with various solenoid valves that switch oil passages and control hydraulic pressure according to the K0 hydraulic control command signal Sk0, the CB hydraulic control command signal Scb, and the WSC hydraulic control command signal Swsc.

[0022] The electronic control unit 90 is functionally equipped with a power source control unit 92, a gear shift control unit 94, and an emergency running control unit 96, etc., in order to realize various controls in the vehicle 10.

[0023] The power source control unit 92 calculates the amount of drive requested by the driver to the vehicle 10 by, for example, applying the accelerator opening θacc and vehicle speed V to the drive request amount map. The drive request amount map is a predetermined relationship for determining the drive request amount, which has been experimentally or design-driven and stored in advance. The drive request amount is, for example, the required drive torque Trdem [Nm], required drive force Frdem [N], and required drive power Prdem [W] at the drive wheels 14. The power source control unit 92 calculates the required input torque Tidem at the transmission input shaft 50 that can realize the above-mentioned drive amount, taking into account transmission losses, auxiliary loads, the gear ratio γat of the automatic transmission 38, the rechargeable power Win and dischargeable power Wout of the HEV battery 28, etc., and determines the target engine torque Tetgt and target MG torque Tmtgt that can obtain that required input torque Tidem. The system then outputs an engine control command signal Se to control the engine 12 so that the target engine torque Tetgt is output, and an MG control command signal Smg to control the electric motor MG so that the target MG torque Tmtgt is output. The rechargeable power Win and dischargeable power Wout of the HEV battery 28 are calculated by the electronic control unit 90 based on, for example, the battery temperature THbat and the charge state value SOC[%] of the HEV battery 28. The charge state value SOC of the HEV battery 28 is a value that indicates the charge state of the HEV battery 28, i.e., the remaining charge, and can be calculated based on, for example, the battery charge / discharge current Ibat and the battery voltage Vbat.

[0024] The power source control unit 92, for example, if the required input torque Tidem can be met by the output of the electric motor MG alone, sets the vehicle to a motor driving mode, which is the BEV (Battery Electric Vehicle) driving mode, in which the electric motor MG is driven solely by power from the HEV battery 28. In BEV driving mode, the K0 clutch 34 is released to stop the engine 12, and the WSC clutch 36 is engaged to perform BEV driving, using only the electric motor MG as the power source. In this BEV driving mode, the MG torque Tmg is controlled to achieve the required input torque Tidem. On the other hand, if the required input torque Tidem cannot be met without using at least the output of the engine 12, the power source control unit 92 sets the vehicle to an engine driving mode, which is the HEV driving mode. In HEV driving mode, both the K0 clutch 34 and the WSC clutch 36 are engaged to perform engine driving, i.e., HEV driving, using at least the engine 12 as the power source. In this HEV driving mode, the engine torque Te is controlled to achieve all or part of the requested input torque Tidem, and the MG torque Tmg is controlled to compensate for any torque deficiency in engine torque Te relative to the requested input torque Tidem.

[0025] The gear shift control unit 94 performs automatic gear shift control by, for example, using a gear shift map with predetermined relationships to make a gear shift decision for the automatic transmission 38, and outputting a CB hydraulic control command signal Scrb to the hydraulic control circuit 52 to switch the gear stage Gr of the automatic transmission 38 as needed. Figure 4 shows an example of the gear shift map described above, in which the required drive torque Trdem and vehicle speed V are defined as variables. The solid line is the upshift line for making an upshift decision, and the dashed line is the downshift line for making a downshift decision. This gear shift map is defined so that as the vehicle speed V increases or the required drive torque Trdem decreases, the gear stage Gr becomes a high-speed gear stage with a smaller gear ratio γat, and as the vehicle speed V decreases or the required drive torque Trdem increases, the gear stage Gr becomes a low-speed gear stage with a larger gear ratio γat. The gear shift control unit 94 also performs manual gear shift control to switch the forward gear Gr of the automatic transmission 38 according to the gear shift instruction when a manual gear shift operating member such as a shift lever is operated by the driver and a gear shift instruction signal such as up or down is supplied. The numbers "1" to "4" in Figure 4 represent the first gear "1st" to the fourth gear "4th", and the gear shift lines for the fifth gear "5th" to the eighth gear "8th" are omitted. Note that the output rotational speed No. may be used instead of the vehicle speed V in Figure 4, and the required drive torque Trdem may be used instead of the required drive force Frdem or accelerator opening θacc.

[0026] The evacuation control unit 96 performs evacuation driving using the motor when an abnormality such as engine failure occurs in the engine 12, in order to extend the driving range. Specifically, it performs signal processing according to steps S1-S11 of the flowchart in Figure 5 (hereinafter, the steps will be omitted and simply referred to as S1-S11). In the flowchart in Figure 5, YES in the diamond-shaped decision step means affirmation, and NO means negation.

[0027] In S1 of Figure 5, the retraction control unit 96 determines whether an abnormality has occurred, including a failure of the engine 12. If an abnormality has occurred, it executes S2. If no abnormality has occurred, there is no need to retract the vehicle, and the process ends. An abnormality includes at least an abnormality that prevents the engine 12 from being used as a power source, such as a failure of the engine 12, the K0 clutch 34, or the WSC clutch 36. A failure of the engine 12 can be determined, for example, from the change in engine rotational speed Ne and rotational acceleration relative to the target engine torque Tetgt calculated by the power source control unit 92. A failure of the K0 clutch 34 can be determined, for example, from the difference in rotation between the engine rotational speed Ne and the MG rotational speed Nmg during the engagement control of the K0 clutch 34, such as a failure of the solenoid valve of the hydraulic control circuit 52. A failure of the WSC clutch 36 can also be determined similarly from the control state and the difference in rotation before and after. A malfunction that restricts the shifting of the automatic transmission 38, such as a malfunction of the solenoid valve in the hydraulic control circuit 52 that prevents the vehicle from achieving a predetermined gear position Gr, can also be included in the abnormalities judged by S1, as it affects the vehicle's operation powered by the engine 12.

[0028] In S2, the evacuation driving control unit 96 determines whether motor driving is possible based on the content of the abnormality determined in S1, etc. In this embodiment, it determines whether BEV driving mode is possible. For example, when there is a failure in the WSC clutch 36, etc., if motor driving is impossible, the process ends as it is. If motor driving is possible, S3 and below are executed, and evacuation driving control is performed by operating the electric motor MG by power supply from the HEV battery 28 to perform evacuation driving. In S3, a constant evacuation driving gear stage Gr1 is set as the gear stage Gr of the automatic transmission 38 during evacuation driving. That is, as shown in FIG. 6, the torque characteristics of the electric motor MG are little affected by the MG rotation speed Nmg, so it is possible to drive, start, etc. without shifting gears. In this embodiment, for example, as shown in FIG. 7, the evacuation driving gear stage Gr1 is set according to the vehicle speed V at that time, and the evacuation driving is performed while fixed to the evacuation driving gear stage Gr1 regardless of changes in the subsequent vehicle speed V or changes in the required driving torque Trdem. FIG. 7 is an example. When V < V1, the 4th gear stage "4th" is set as the evacuation driving gear stage Gr1, when V1 ≤ V < V2, the 5th gear stage "5th" is set, and when V2 ≤ V, the 6th gear stage "6th" is set as the evacuation driving gear stage Gr1 respectively, and the evacuation driving gear stage Gr1 is maintained without depending on the shift map in FIG. 4. V1 and V2 are gear stage determination vehicle speeds, and are preset, for example, so that the MG rotation speed Nmg is maintained below a predetermined upper limit determination value Nmgs in FIG. 6. The type and number of the evacuation driving gear stage Gr1 can be determined as appropriate. It is also possible to determine a constant evacuation driving gear stage Gr1 regardless of the vehicle speed V, but as a gear stage that can produce a driving force for starting and accelerating even at low vehicle speeds, a low-speed side gear stage Gr with a large transmission ratio γat is appropriate. On the other hand, when the vehicle speed V during the evacuation driving transition on a highway or the like is high, the motor may over-rotate or the upper limit of the MG torque Tmg may decrease. Therefore, in this embodiment, the evacuation driving gear stage Gr1 is set according to the vehicle speed V.

[0029] In the next step, S4, it is determined whether the vehicle speed V has decreased to a predetermined low vehicle speed threshold Vlo or less. If the vehicle speed is medium to high (V > Vlo), S5 or below is performed, but if the vehicle speed is low (V ≤ Vlo), S8 or below is performed. In this embodiment, a mechanical oil pump 58 and an electric oil pump 60 are provided. The mechanical oil pump 58 is connected to the electric motor coupling shaft 48 and rotated to discharge hydraulic fluid. Therefore, when the vehicle speed V decreases and the MG rotation speed Nmg decreases, the rotation speed of the mechanical oil pump 58 also decreases accordingly, and the amount of hydraulic fluid discharged decreases. A certain amount of engagement hydraulic pressure is required to engage the WSC clutch 36 or to maintain the automatic transmission 38 in a predetermined gear stage Gr (in this case, the retracted driving gear stage Gr1). Therefore, when the amount of oil discharged by the mechanical oil pump 58 decreases, it is necessary to compensate for this with the electric oil pump 60, and the power consumption of the electric oil pump 60 shortens the driving range. To suppress this, when the MG rotational speed Nmg falls below a predetermined low rotational speed threshold Nmglo, which is the amount of oil discharged by the mechanical oil pump 58, S8 is executed to downshift the automatic transmission 38 and increase the MG rotational speed Nmg. In other words, the low vehicle speed threshold Vlo is determined according to the gear ratio γat of the retracted driving gear stage Gr1 at that time, and is set to the vehicle speed at which the MG rotational speed Nmg falls below the low rotational speed threshold Nmglo. In other words, a different low vehicle speed threshold Vlo is set for each retracted driving gear stage Gr1.

[0030] When driving at medium to high speeds (V>Vlo), if the judgment in S4 is NO, S5 is executed to determine whether the charge state value (SOC) of the HEV battery 28 has fallen below a predetermined lower limit value (SOCmin). The lower limit value (SOCmin) is the charge state value (SOC) at which the electric motor MG may not be able to operate properly or the HEV battery 28 may be damaged. If SOC ≤ SOCmin, S7 is executed immediately to stop the power supply to the electric motor MG and set it to the ready OFF state. If SOC > SOCmin and the judgment in S5 is NO, S6 is executed to determine whether the operation to set the vehicle to ready OFF has been performed using the power switch 84. If the ready OFF operation has been performed, S7 is executed to set the vehicle to the ready OFF state. If the ready OFF operation has not been performed, S4 and subsequent steps are repeated to fix the automatic transmission 38 to a certain retraction driving gear stage (Gr1) and perform retraction driving using the electric motor MG.

[0031] During the evasive driving phase, which involves repeatedly performing steps S4 and below, if the vehicle speed V becomes a low vehicle speed below the low vehicle speed judgment value Vlo, and the judgment in S4 becomes YES, the automatic transmission 38 is downshifted in S8 to a predetermined low vehicle speed gear Gr2. The low vehicle speed gear Gr2 is intended to increase the MG rotational speed Nmg, which corresponds to the rotational speed of the mechanical oil pump 58, thereby delaying the start of operation of the electric oil pump 60 or suppressing an increase in the amount of oil discharged by the electric oil pump 60. For example, the second gear "2nd" or the third gear "3rd" is appropriate. This reduces power consumption by the electric oil pump 60 and extends the driving range during evasive driving.

[0032] In S9, it is determined whether the vehicle speed V has increased to be equal to or higher than a predetermined increase determination value Vup. While V < Vup, S10 and below are executed. However, when Vup ≤ V, S3 and below are executed. The increase determination value Vup is a vehicle speed that is sufficiently higher than the low vehicle speed determination value Vlo. A vehicle speed is determined such that, for example, the MG rotational speed Nmg exceeds the upper limit determination value Nmgs while remaining in the low vehicle speed gear stage Gr2. S10 and S11, which are executed when the determination in S9 is NO with V < Vup, are the same as S5 and S6 respectively. When SOC ≤ SOCmin or when a ready OFF operation is performed, S7 is executed to enter the ready OFF state. Also, when SOC > SOCmin and no ready OFF operation has been performed, S9 and below are repeatedly executed, the automatic transmission 38 is fixed to a certain low vehicle speed gear stage Gr2, and the retreat running using the motor MG is continued. On the other hand, when the determination in S9 becomes YES with Vup ≤ V, S3 is executed, and a new fixed retreat running gear stage Gr1 is set according to the vehicle speed V at that time. Then, the automatic transmission 38 is fixed to the new retreat running gear stage Gr1, and the retreat running using the motor MG is continued.

[0033] Thus, according to the retreat running control unit 96 functionally provided in the electronic control unit 90 of the vehicle 10 of this embodiment, during the retreat running in which the motor MG is operated by power supply from the HEV battery 28, since the gear stage Gr of the automatic transmission 38 is restricted to the retreat running gear stage Gr1 or the low vehicle speed gear stage Gr2 and gear shifting is suppressed, power consumption due to rotational speed control etc. by the motor MG for suppressing gear shift shocks etc. is suppressed, and the cruising distance of the vehicle 10 can be extended by that much.

[0034] Furthermore, when driving at medium to high speeds where the vehicle speed V is higher than the low speed judgment value Vlo, the automatic transmission 38 is fixed to the retracted driving gear stage Gr1, thereby eliminating power consumption caused by rotational speed control by the electric motor MG during gear changes and extending the driving range. On the other hand, when driving at low speeds where the vehicle speed V is below the low speed judgment value Vlo, the automatic transmission 38 is downshifted to the low speed gear stage Gr2, which has a larger gear ratio γat than the retracted driving gear stage Gr1. Therefore, regardless of the low speed, the rotational speed Nmg of the electric motor MG is increased by the downshift, and the amount of oil discharged by the mechanical oil pump 58, which is rotationally driven by the electric motor MG, increases. As a result, it is possible to suppress the operation of the electric oil pump 60 by the amount of the increase in the amount of oil discharged, thereby reducing power consumption by the electric oil pump 60 and extending the driving range.

[0035] In the above embodiment, the automatic transmission 38 was downshifted to the low-speed gear Gr2 when the vehicle speed was low (V ≤ Vlo). However, as shown in the flowchart in Figure 8, steps S4, S8-S11 related to the low-speed gear Gr2 can be omitted. In other words, regardless of the decrease in vehicle speed V or the vehicle stopping, the vehicle can be fixed to a constant retraction gear Gr1 set in S3, and retraction driving can be performed using the electric motor MG.

[0036] Although embodiments of the present invention have been described in detail above with reference to the drawings, this is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0037] 10: Vehicle 12: Engine 14: Drive wheels 18: Power transmission system (power transmission path) 28: HEV battery (energy storage device) 38: Automatic transmission 52: Hydraulic control circuit 58: Mechanical oil pump 60: Electric oil pump 62: Pump drive motor 90: Electronic control unit (control unit) 96: Evacuation running control unit MG: Electric motor Gr1: Evacuation running gear stage Gr2: Low vehicle speed gear stage V: Vehicle speed

Claims

[Claim 1] The present invention relates to a vehicle that includes an engine and an electric motor as power sources for driving, a hydraulic control circuit having a mechanical oil pump driven by the electric motor and an electric oil pump driven by a dedicated pump drive motor, and an automatic transmission capable of forming multiple gear stages with different gear ratios in the power transmission path between the power source and the drive wheels. In a vehicle control device that includes a vehicle escape control unit that operates the electric motor by supplying power from a power storage device to perform escape movement when the engine fails, The retraction travel control unit, in accordance with the actual gear ratio of the retraction travel gear, keeps the automatic transmission fixed to a predetermined retraction travel gear while the vehicle speed is higher than a predetermined low vehicle speed determination value, which is such that the rotational speed of the electric motor falls below a predetermined low rotational speed determination value, which is such that the amount of oil discharged from the mechanical oil pump falls below a certain amount. However, when the vehicle speed falls below the low vehicle speed determination value, the unit downshifts the automatic transmission to a predetermined low vehicle speed gear with a larger gear ratio than the retraction travel gear, thereby limiting the gear changes of the automatic transmission. A vehicle control device characterized by the following features.

Images