Control system for hybrid vehicles

Abstract

The present invention provides a control device for a hybrid vehicle that can select an engine start control that can expel water from the exhaust pipe if an engine start request is made while crossing a river. [Solution] When the transfer case 22 is in low range and the ignition is turned on after the ignition is turned off, the engine start control selection unit 154 requests engine start and selects an engine start control with a large cranking torque from among multiple engine start control options. In this way, when crossing a river, if the low range of the transfer case 22 is selected (when crossing a river), when the ignition is turned on after the ignition is turned off, engine start is requested and an engine start control with a large cranking torque from among multiple engine start control options is selected, so that the water in the exhaust pipe 12c can be pushed out and the engine can be started easily.

Description

Technical Field

[0004] , , , , , ,

[0006] , , , ,

[0005] , , , , ,

[0001] The present invention relates to a control device for a hybrid vehicle that distributes the driving force transmitted from an engine to front and rear wheels, includes a transfer having a transmission mechanism capable of high-low range switching, and has a plurality of engine start controls with different cranking torques.

Background Art

[0002] Patent Document 1 discloses a vehicle control device that prohibits the engine from stopping when the engine is running when the water level around the vehicle is above a predetermined value, and starts the engine when the engine is stopped by idling stop or the like.

[0003] According to such a vehicle control device, it is possible to suppress the entry of water into the exhaust pipe when the engine is stopped when the water level around the vehicle is high.

Prior Art Documents

Patent Documents

[0007] The inventors of this invention focused on the fact that in a hybrid vehicle equipped with a transfer case that has a high / low selectable transmission mechanism, the transfer case is switched to low range when crossing a river. They found that when an engine start request is made by ignition-on while the transfer case is switched to low range, if the engine start control is performed with a cranking torque that is sufficiently greater than the minimum necessary cranking torque, the water in the exhaust pipe can be pushed out, and the engine can be started easily. This invention was made based on this finding.

[0008] In other words, the gist of the first invention is a control device for a hybrid vehicle comprising (a) an engine and an electric motor, and a transfer case having a high / low gear shift mechanism that distributes the driving force transmitted from the engine and the electric motor to the front and rear wheels, and (b) a plurality of engine start control systems that start the engine with relatively different cranking torques, and an engine start control selection unit that, when the IG is turned on after IG-OFF when the transfer case is in low range, requests engine start and selects the engine start control system with the largest cranking torque from among the plurality of engine start control systems.

[0009] The gist of the second invention is that, in the first invention, (c) the hybrid vehicle is provided with an engine engagement clutch between the engine and the electric motor, and (d) the engine start control selection unit transmits cranking torque to the engine using the electric motor with the engine engagement clutch slip-engaged in the case of an engine start control with a small cranking torque among the plurality of engine start controls, and transmits cranking torque to the engine using the electric motor with the engine engagement clutch fully engaged in the case of an engine start control with a large cranking torque.

[0010] The gist of the third invention is that, in the second invention, when the transfer case is in high range, the engine start control selection unit selects the engine start control with the smallest cranking torque from among the plurality of engine start controls. [Effects of the Invention]

[0011] In the control device for the hybrid vehicle of the first invention, when the ignition is turned on after the ignition is turned off while the transfer case is in low range, the engine start control selection unit requests engine start and selects an engine start control with a large cranking torque from among multiple engine start controls. Thus, when driving across a river, when the ignition is turned on after the ignition is turned off while the transfer case is in low range, engine start is requested and an engine start control with a large cranking torque from among multiple engine start controls is selected, so that the water in the exhaust pipe can be pushed out and the engine can be started easily.

[0012] In the second invention, the hybrid vehicle is equipped with an engine engagement / disengagement clutch between the engine and the electric motor. The engine start control selection unit transmits cranking torque to the engine using the electric motor with the engine engagement / disengagement clutch slip-engaged when the engine start control with low cranking torque is selected from among multiple engine start control options, and transmits cranking torque to the engine using the electric motor with the engine engagement / disengagement clutch fully engaged when the engine start control with high cranking torque is selected. As a result, since cranking torque is transmitted to the engine using the electric motor with the engine engagement / disengagement clutch fully engaged, water in the exhaust pipe can be quickly pushed out, and the engine can be started easily.

[0013] In the third invention, when the transfer case is in high range, the engine start control selection unit selects an engine start control with a small cranking torque from among multiple engine start controls, so that the engine can be started with the minimum cranking torque necessary to improve fuel efficiency. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram illustrates the schematic configuration of the drive system of a front and rear wheel drive hybrid vehicle to which the present invention is applied, and also shows the main parts of the control function. [Figure 2] Figure 1 is a schematic diagram illustrating a specific example of a power transmission system for hybrid vehicles. [Figure 3] This is a schematic diagram illustrating a specific example of the transfer shown in Figure 1. [Figure 4] Figure 1 is a diagram illustrating the multiple driving modes of the hybrid vehicle. [Figure 5] This is a flowchart illustrating the control actions performed by the engine start control selection unit shown in Figure 1. [Modes for carrying out the invention]

[0015] This invention relates to a hybrid four-wheel drive vehicle having an electric motor and an engine (internal combustion engine) as power sources. A motor generator that also functions as a generator is suitable for the electric motor, but an electric motor that does not provide generator functionality can also be used. The hybrid vehicle preferably uses a so-called one-motor hybrid vehicle in which the engine, engine engagement clutch, electric motor, transmission, and transfer case are arranged in series. However, it may also be a so-called two-motor hybrid vehicle in which the engine is connected to the first rotating element of a planetary gear system that functions as a power distribution device, the first electric motor is connected to the second rotating element, the second electric motor is connected to the third rotating element, and the transmission and transfer case are connected to the third rotating element. Alternatively, it may be a so-called series hybrid vehicle in which the first electric motor is connected to the engine, and the second electric motor, driven by the electricity generated by the first electric motor, drives the four wheels via the transfer case.

[0016] The transfer case may constantly distribute the driving force from the engine and electric motor to the front and rear wheels for permanent four-wheel drive, or it may selectively distribute a portion of the driving force transmitted from the engine and electric motor to the main drive wheels to the secondary drive wheels for partial four-wheel drive. Furthermore, the high / low gear switching device of the transfer case may be, for example, a planetary gear system, but a parallel-axis type high / low gear switching device may also be used. The high / low gear switching device is equipped with a meshing clutch, and it is desirable that the meshing clutch has a synchronization mechanism, but it is not required.

[0017] The driving mode switching control unit is configured to establish four types of driving modes, such as H4F mode, H4L mode, L4F mode, and L4L mode, according to the selection by the high / low selection device and the selection by the differential state selection device. However, it is also acceptable to simply switch to three types of driving modes, such as H4F mode, L4F mode, and L4L mode, or to three types of driving modes, such as H4F mode, H4L mode, and L4L mode. [Examples]

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram for explaining the drive system of a hybrid vehicle 10 to which the present invention is applied, and is a diagram showing the main parts of control functions for various controls in the hybrid vehicle 10. The hybrid vehicle 10 is a hybrid four-wheel drive vehicle based on a front-engine rear-wheel drive (FR) system. The hybrid vehicle 10 includes an engine 12, a pair of left and right front wheels 14, a pair of left and right rear wheels 16, and a power transmission device 18. In the hybrid vehicle 10, as is well known, engine driving and electric motor driving are repeated to reduce fuel consumption, and the engine 12 is intermittently operated.

[0019] The power transmission device 18 includes an HV transmission 20 connected to the engine 12 and a transfer 22 connected to the HV transmission 20. The driving force transmitted from the engine 12 and the HV transmission 20 to the transfer 22 is distributed to be transmitted to the left and right rear wheels 16 via the rear propeller shaft 26 and the differential 30, while a part of the driving force is transmitted to the left and right front wheels 14 via the front propeller shaft 24 and the differential 28. The engine 12 is an internal combustion engine such as a gasoline engine and is used as a power source for running. The engine torque Te, which is the torque of the engine 12, is controlled by an engine control signal Se output from an electronic control unit 150.

[0020] An exhaust pipe 所12c having a catalytic converter 12a and a muffler 12b for discharging the exhaust gas of the engine 12 is connected to the engine 12. The ground height of the outlet 12d of the exhaust pipe 12c is about 30 cm. The hybrid vehicle 10 may, for example, cross a river with a depth of 70 cm, and during the river-crossing driving, it is conceivable that the outlet 12d of the exhaust pipe 12c is submerged in water.

[0021] It should be noted that there seems to be an incorrect character "所" in the original text of . I translated it as it is, but it might be a typo. If it's a wrong character, please correct it for a more accurate translation.Figure 2 is a schematic diagram illustrating a specific example of a hybrid vehicle (HV) transmission system 20. The HV transmission system 20 comprises an electric motor MG, a motor connecting shaft 42, a torque converter 44, and an automatic transmission 46, all arranged on a common first axis CL1 within a case 40, which is a non-rotating member. The electric motor MG and the torque converter 44 are configured approximately symmetrically with respect to the first axis CL1, and the lower half of the first axis CL1 is omitted in Figure 2.

[0022] An engine engagement clutch K0 is provided between the engine 12 and the motor connecting shaft 42. An electric motor MG, which is used as a power source for driving together with the engine 12, is connected to the motor connecting shaft 42 via a motor engagement clutch K2. The engine engagement clutch K0 and the motor engagement clutch K2 are hydraulic friction engagement devices, and the engagement hydraulic pressure supplied from the hydraulic control circuit 52 (see Figure 1) is controlled by the K0 switching signal Sk0 and K2 switching signal Sk2 output from the electronic control device 150, respectively, thereby switching between engagement, disengagement, and slip states individually. The hydraulic control circuit 52 is equipped with an electromagnetic switching valve, an electromagnetic pressure regulating valve, and an electric oil pump, and is capable of outputting a predetermined hydraulic pressure even when the hybrid vehicle 10 is stopped. The electric motor MG is a motor generator that also functions as a generator, and is connected to an energy storage device via an inverter (not shown). The torque of the electric motor MG, MG torque Tmg, is controlled by the MG control signal Smg output from the electronic control device 150.

[0023] The torque converter 44 comprises a pump impeller 44a connected to a motor connecting shaft 42 and a turbine impeller 44b connected to a transmission input shaft 48. The torque converter 44 is a fluid-type transmission device that transmits power from the power source, the engine 12 and / or electric motor MG, to the transmission input shaft 48 via fluid. The torque converter 44 includes a lock-up clutch LU that connects the pump impeller 44a and the turbine impeller 44b. The lock-up clutch LU is a hydraulic friction engagement device, and the engagement and release states are switched by controlling the engagement hydraulic pressure supplied from the hydraulic control circuit 52 with an LU control signal Slu output from the electronic control unit 150.

[0024] The automatic transmission 46 is a known planetary gear type automatic transmission comprising, for example, one or more sets of planetary gears and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices, and the engagement and disengagement states are switched by the engagement hydraulic pressure supplied from the hydraulic control circuit 52, which is controlled by the CB control signal Scob output from the electronic control device 150. The automatic transmission 46 is a stepped transmission that can form multiple gear stages with different gear ratios γ (= AT input rotational speed Ni / AT output rotational speed No) depending on the engagement and disengagement states of the plurality of engagement devices CB. The AT input rotational speed Ni is the rotational speed of the transmission input shaft 48 and is equal to the turbine rotational speed Nt, which is the output rotational speed of the torque converter 44. The AT output rotational speed No is the rotational speed of the transmission output shaft 50.

[0025] Figure 3 is a schematic diagram illustrating a specific example of the transfer case 22. The transfer case 22 is equipped with a TF input shaft 62 connected to the transmission output shaft 50, a high / low switching device 64, a center differential 66, a rear wheel side output shaft 68, and a sprocket-shaped drive gear 70 that outputs driving force to the front wheels 14, all on a first axis CL1 which is the same axis as the HV transmission device 20. Driving force is transmitted from the rear wheel side output shaft 68 to the rear propeller shaft 26. The transfer case 22 also includes a front wheel side output shaft 72 and a sprocket-shaped driven gear 74 integrally provided on the front wheel side output shaft 72, on a second axis CL2 which is parallel to the first axis CL1. An endless annular chain 76 is wrapped between the drive gear 70 and the driven gear 74, and driving force is transmitted from the center differential 66 to the front wheel side output shaft 72 via the drive gear 70, chain 76, and driven gear 74. Driving force is transmitted from the front wheel side output shaft 72 to the front propeller shaft 24.

[0026] The high-low switching device 64 is composed of a high-low selectable speed change mechanism comprising a single-pinion type planetary gear system having a sun gear S1, a carrier C1, and a ring gear R1, and a high-low switching clutch D1. The sun gear S1 is connected to the TF input shaft 62, and the ring gear R1 is fixed to the case 40. The high-low switching clutch D1 is a meshing clutch with a synchronization mechanism, comprising a high-gear side meshing tooth 80 provided on the TF input shaft 62, a low-gear side meshing tooth 82 provided on the carrier C1, and an HL switching sleeve 86 disposed on the HL output member 84 so as to be rotatable relative to and movable in the axial direction, and having meshing teeth that selectively mesh with the high-gear side meshing tooth 80 and the low-gear side meshing tooth 82. The HL switching sleeve 86 is reciprocated axially by a hydraulic actuator, switching between high gear Hi, which meshes with the high gear side meshing teeth 80 to directly connect the TF input shaft 62 and the HL output member 84, and low gear Lo, which meshes with the low gear side meshing teeth 82 to connect the carrier C1 and the HL output member 84, causing the HL output member 84 to rotate at a lower speed than the TF input shaft 62. The HL switching sleeve 86 is moved axially by hydraulic pressure supplied from the hydraulic control circuit 52, which is controlled by the D1 switching signal Sd1 output from the electronic control device 150, and the high / low switching device 64 is switched between high gear Hi and low gear Lo. Between high gear Hi and low gear Lo, the HL switching sleeve 86 does not mesh with either the high gear side meshing teeth 80 or the low gear side meshing teeth 82, resulting in a neutral state where power transmission is interrupted.

[0027] The center differential 66 is configured with a single-pinion type planetary gear system having a sun gear S2, a carrier C2, and a ring gear R2. The carrier C2 is connected to the HL output member 84 and rotated. The ring gear R2 is connected to the rear wheel side output shaft 68, and the sun gear S2 is connected to the drive gear 70, transmitting the rotation of the HL output member 84 to the front wheel 14 and the rear wheel 16 in a differential rotation manner.

[0028] Between the sun gear S2 and the carrier C2 of the center differential 66, a differential lock clutch D2 is provided as a differential lock device to limit differential rotation. The differential lock clutch D2 is a meshing clutch without a synchronization mechanism and comprises meshing teeth 90 provided on the sun gear S2, meshing teeth 92 provided on the carrier C2, and a differential lock sleeve 94 that is axially movable and has meshing teeth that mesh with the meshing teeth 90 and 92. The differential lock sleeve 94 is constantly meshed with one of the meshing teeth 90 and is reciprocated axially by a hydraulic actuator to mesh with the other meshing tooth 92, thereby switching between a differential lock that connects the sun gear S2 and the carrier C2 so that they cannot rotate relative to each other, and a free state that releases the meshing with the other meshing tooth 92, allowing relative rotation between the sun gear S2 and the carrier C2, i.e., differential rotation of the center differential 66. The differential lock sleeve 94 is moved axially by hydraulic pressure supplied from the hydraulic control circuit 52, which is controlled by the D2 switching signal Sd2 output from the electronic control unit 150, thereby switching the center differential 66 between free and differential lock.

[0029] Returning to Figure 1, the hybrid vehicle 10 is equipped with an electronic control unit 150 as a control device for controlling the operation of various parts such as the engine 12, the HV transmission 20, and the transfer case 22. The electronic control unit 150 is composed of a so-called microcomputer equipped with a CPU, RAM, ROM, input / output interface, etc., and performs various controls by performing signal processing according to a program stored in the ROM in advance.

[0030] The electronic control unit 150 is supplied with various information necessary for control from various sensors installed in the hybrid vehicle 10. For example, it receives information from the engine rotation speed sensor 112, MG rotation speed sensor 114, AT input rotation speed sensor 116, AT output rotation speed sensor 118, accelerator pedal position sensor 120, throttle valve position sensor 122, brake force sensor 124, wheel speed sensor 126, high / low state detection sensor 128, differential state detection sensor 130, etc., including engine rotation speed Ne (rotation speed of engine 12), MG rotation speed Nmg (rotation speed of electric motor MG), AT input rotation speed Ni, AT output rotation speed No, accelerator pedal position sensor Signals are supplied to represent the accelerator opening θacc corresponding to the amount the pedal is pressed, the throttle valve opening θth which is the opening of the electronic throttle valve of the engine 12, the brake force Fbr corresponding to the force the brake pedal is pressed, the wheel speeds Nwfl, Nwfr, Nwrl, and Nwrr of the front wheels 14 and rear wheels 16, the high / low status Phl which indicates whether the high / low switching device 64 is in high gear (Hi) or low gear (Lo), and the differential status Pdiff which indicates whether the center differential 66 is free or locked. Based on the wheel speeds Nwfl, Nwfr, Nwrl, and Nwrr, the vehicle speed V can be determined.

[0031] The electronic control unit 150 is also supplied with a range selection signal Srang, a high-low selection signal Shl, and a differential state selection signal Sdiff from a range selection device 140, a high-low selection device 142 that selects whether to set the high-low switch 64 to high gear (Hi) or low gear (Lo), and a differential state selection device 144 that selects whether to set the center differential 66 to free or differential lock. These range selection device 140, high-low selection device 142, and differential state selection device 144 are operating devices that are located near the driver's seat and operated by the driver. The range selection device 140 can be set, for example, by a shift lever, allowing selection of the D range for forward driving, the R range for reverse driving, the P range for parking, etc. The high-low selection device 142 is set, for example, by a low gear selection switch that is operated when selecting low gear (Lo), and if not operated, high gear (Hi) is selected. The differential state selection device 144 is set, for example, by a differential lock selection switch that is operated when selecting differential lock, and if not operated, it is set to free. These high / low selector 142 and differential state selector 144 are operated, for example, to improve traction on muddy roads, icy roads, riverbeds, and other areas with poor road conditions, by switching the high / low switch 64 to low gear (Lo) or locking the center differential 66.

[0032] The electronic control unit 150 calculates the required drive torque based on the accelerator opening θacc and vehicle speed V, and determines an engine driving mode or an electric motor driving mode based on the required drive torque from a pre-stored driving mode map so that the required drive torque is obtained with minimum fuel consumption. It then controls the engine torque Te and MG torque Tmg for engine driving, or the MG torque Tmg for electric motor driving. Through this control, the engine 12 of the hybrid vehicle 10 is operated intermittently. In addition, the electronic control unit 150 performs gear shift control of the automatic transmission 46 according to a predetermined gear shift map, and includes a four-wheel driving mode switching control unit 152 that switches between multiple types of four-wheel driving modes with different operating states of the transfer case 22, and an engine start control selection unit 154 that has multiple engine start control (methods) with relatively different cranking torques, and when starting the engine after the engine has stopped (during electric motor driving), if the transfer case 22 is in low range, it selects the engine start control with the maximum cranking torque to improve the starting performance of the engine 12 during river crossing.

[0033] The four-wheel driving mode switching control unit 152 switches the transfer case 22 to one of the four four-wheel driving modes shown in Figure 4 by changing the operating state of the high-low switching device 64 and the differential lock clutch D2 in accordance with the selection by the high-low selection device 142 and the differential state selection device 144. Specifically, the high-low switching device 64 switches to H4F mode, where the gear is high (Hi) and the center differential 66 is free; H4L mode, where the gear is high (Hi) and the center differential 66 is locked; L4F mode, where the gear is low (Lo) and the center differential 66 is free; and L4L mode, where the gear is low (Lo) and the center differential 66 is locked. As shown in Figure 5, in these H4F mode, H4L mode, L4F mode, and L4L mode, the high / low switching device 64 and the differential lock clutch D2 are switched separately in accordance with the selection operation of the high / low selection device 142 and the differential state selection device 144, and the high / low switching device 64 and the differential lock clutch D2 are never switched simultaneously.

[0034] The engine start control selection unit 154 has a plurality of engine start control (methods) pre-configured to start the engine 12 with relatively different cranking torques. When the transfer case 22 is in low range based on a signal from the 4-wheel driving mode switching control unit 152, and the IG-ON (ignition on state) is activated after IG-OFF (engine 12 stopped due to ignition off), the unit requests engine start and selects the engine start control with the largest cranking torque, preferably the one with the maximum cranking torque, from among the plurality of engine start control methods, and starts the engine 12.

[0035] The engine start control selection unit 154 transmits cranking torque to the engine 12 using the electric motor MG with the engine engagement clutch K0 fully engaged when selecting an engine start control with a large cranking torque from among the multiple engine start controls. On the other hand, when selecting an engine start control with a small cranking torque from among the multiple engine start controls, the engine start control selection unit 154 transmits cranking torque to the engine 12 using the electric motor MG with the engine engagement clutch K0 in a slip-engaged state. For example, when the transfer case 22 is in high range, the engine start control selection unit 154 selects an engine start control with a small cranking torque from among the multiple engine start controls.

[0036] Figure 5 is a flowchart illustrating the main parts of the control operation of the electronic control unit 150. Steps S3, S5-S7 in Figure 5 correspond to the engine start control selection unit 154. In step S1 (the steps are omitted hereafter), the IG-OFF is performed to stop the intermittently operating engine 12 and switch to electric motor drive mode. Then, in S2, the IG-ON is performed to switch to engine drive mode. Next, assuming that the transfer case 22 is switched to low range by the operation of the high-low selection device 142 at least during river crossing, in S3 it is determined whether or not the transfer case 22 is switched to low range. If the determination in S3 is negative, the transfer case 22 is in high range, so the electric motor drive mode continues, and ReadyON is performed in S4. However, if the judgment in S3 is affirmed, an engine start request is issued in S5, and in S6, from among multiple engine start control (methods) that start the engine 12 with relatively different cranking torques using the electric motor MG and the engine engagement clutch K0, the engine start control with a large cranking torque that transmits cranking torque to the engine 12 using the electric motor MG with the engine engagement clutch K0 fully engaged is selected. Next, in S7, the engine 12 is started using the engine start control with a large cranking torque selected in S6. Then, in S4, the system is set to engine driving mode and enters the Ready ON state.

[0037] As described above, in the electronic control unit 150 of the hybrid vehicle 10 of this embodiment, when the ignition is turned on after the ignition is turned off while the transfer case 22 is in low range, the engine start control selection unit 154 requests engine start and selects an engine start control with a large cranking torque from among the multiple engine start control options. In this way, when the low range of the transfer case 22 is selected, the vehicle is at least crossing a river, so when the ignition is turned on after the ignition is turned off, engine start is requested and an engine start control with a large cranking torque from among the multiple engine start control options is selected, which allows the water in the exhaust pipe 12c to be pushed out and the engine to be started easily.

[0038] Furthermore, in the electronic control device 150 of the hybrid vehicle 10 of this embodiment, the hybrid vehicle 10 is equipped with an engine engagement / disengagement clutch K0 between the engine 12 and the electric motor MG. The engine start control selection unit 154 transmits cranking torque to the engine 12 using the electric motor MG with the engine engagement / disengagement clutch K0 in a slip-engaged state when the engine start control with a small cranking torque is selected from among the multiple engine start control options. When the engine start control with a large cranking torque is selected, the engine engagement / disengagement clutch K0 is fully engaged when the electric motor MG is used to transmit cranking torque to the engine 12. As a result, when the engine start control with a large cranking torque is selected, the engine engagement / disengagement clutch K0 is fully engaged when the electric motor MG is used to transmit cranking torque to the engine 12, which allows water in the exhaust pipe 12c to be quickly pushed out and the engine to be started easily.

[0039] Furthermore, in the electronic control unit 150 of the hybrid vehicle 10 of this embodiment, when the transfer case 22 is in high range, the engine start control selection unit 154 selects the engine start control with the smallest cranking torque from among a plurality of engine start controls with different cranking torques, so that the engine 12 can be started with the minimum cranking torque necessary to improve fuel efficiency.

[0040] Although embodiments of the present invention have been described in detail above with reference to the drawings, these are merely examples, and the invention can be implemented in various modified and improved forms. [Explanation of symbols]

[0041] 10: Hybrid vehicle, 12: Engine, 12c: Exhaust pipe, 14: Front wheel, 16: Rear wheel, 22: Transfer case, 150: Electronic control unit (control unit), 154: Engine start control selection unit, MG: Electric motor, K0: Engine engagement clutch

Claims

1. A control device for a hybrid vehicle comprising an engine and an electric motor, and a transfer case having a high / low gear shift mechanism that distributes the driving force from the engine and the electric motor to the front and rear wheels, The system includes a plurality of engine start control systems that start the engine with relatively different cranking torques, and when the ignition is turned on after being turned off while the transfer case is in low range, it requests engine start and includes an engine start control selection unit that selects the engine start control with the largest cranking torque from among the plurality of engine start control systems. A control device for a hybrid vehicle characterized by the following features.

2. The aforementioned hybrid vehicle is equipped with an engine engagement clutch between the engine and the electric motor. The engine start control selection unit transmits cranking torque to the engine using the electric motor with the engine engagement clutch slip-engaged in the case of an engine start control with low cranking torque among the multiple engine start controls, and transmits cranking torque to the engine using the electric motor with the engine engagement clutch fully engaged in the case of an engine start control with high cranking torque. A control device for a hybrid vehicle according to feature 1.

3. When the transfer case is in high range, the engine start control selection unit selects the engine start control with the smallest cranking torque from among the multiple engine start controls. A control device for a hybrid vehicle according to feature 2.

Images