Control system for hybrid vehicles

Abstract

This invention provides a control device for hybrid vehicles that does not cause problems with vehicle operation or deterioration in fuel efficiency that may arise from the automatic transmission. [Solution] When the series driving determination unit 150 determines that a series driving mode is requested or selected, the series driving control unit 152 sets the transfer case 26 to neutral and performs series driving using only the second motor MG2, with the power generated by the first motor MG1 driven by the engine 12. This allows the hybrid vehicle 10 to run without problems in series driving mode, for example, in the event of a failure of the automatic transmission 24, or when the series driving mode is more fuel-efficient than other driving modes in which power is transmitted via the automatic transmission 24.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle having an engine and a drive unit with a first electric motor, an automatic transmission, a transfer, and a second electric motor, which enables motor driving only with the electric motor by setting the transfer to neutral.

Background Art

[0002] Patent Document 1 discloses a control device for a hybrid vehicle having a drive unit with an engine and a first electric motor, an automatic transmission, and a transfer.

[0003] According to such a control device for a hybrid vehicle, by switching the drive unit and the transfer, four-wheel Hi-gear engine driving, four-wheel Lo-gear engine driving, four-wheel Hi-gear motor driving, and four-wheel Lo-gear motor driving can be selectively performed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the control device for a hybrid vehicle of Patent Document 1, since power is transmitted from the drive unit via the automatic transmission, if a failure occurs such as only a specific gear can be formed in the automatic transmission or parts are damaged and power transmission is impossible, it may cause problems in vehicle running or make the vehicle unable to run. Also, there is a problem that better fuel efficiency can be obtained by driving only with the second electric motor arranged on the downstream side of the transfer without passing through the automatic transmission rather than transmitting power via the automatic transmission.

[0006] This invention was made against the above circumstances, and its objective is to provide a control device for a hybrid vehicle that does not cause problems with vehicle operation or deterioration of fuel efficiency resulting from the automatic transmission. [Means for solving the problem]

[0007] In other words, the gist of the present invention is a control device for a hybrid vehicle which includes an automatic transmission and a transfer case in the power transmission path between a drive unit having an engine and a first electric motor and a drive wheel, the control device comprising: (a) a second electric motor disposed downstream of the transfer case; (c) a series driving determination unit which determines whether a series driving mode is requested or selected in which the vehicle is driven using only the second electric motor as a drive source using the power generated by the first electric motor; and (d) a series driving control unit which, if the series driving determination unit determines that a series driving mode is requested or selected, switches the transfer case to a neutral state and drives the second electric motor using the power generated by driving the first electric motor with the engine. [Effects of the Invention]

[0008] According to the control device for a hybrid vehicle of the present invention, when the series driving determination unit determines that a series driving mode is requested or selected, the series driving control unit sets the transfer case to neutral and performs series driving using only the second motor, with the power generated by the first motor driven by the engine. This allows the hybrid vehicle to run without problems in series driving mode, for example, in the event of a failure of the automatic transmission or when the series driving mode is more fuel-efficient than other driving modes in which power is transmitted via the automatic transmission. This effect is particularly suitable when the hybrid vehicle is a plug-in hybrid vehicle (PHEV). [Brief explanation of the drawing]

[0009] [Figure 1]This figure shows a schematic configuration of a hybrid vehicle to which the present invention is applied, along with an electronic control unit. [Figure 2] This is a schematic diagram illustrating the main components of the transfer mechanism shown in Figure 1. [Figure 3] Figure 1 is a flowchart illustrating the key aspects of the control operation of the electronic control unit. [Figure 4] Figure 1 is a flowchart illustrating other key aspects of the control operation of the electronic control unit. [Modes for carrying out the invention]

[0010] The transfer case of the present invention only needs to be switchable to neutral (power cut-off state), and may constantly distribute the driving force from the drive unit 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 auxiliary drive wheels for partial four-wheel drive. Furthermore, a high / low switching device for the transfer case is not necessarily provided. [Examples]

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram illustrating the drive system of a hybrid vehicle 10 to which the present invention is applied, and also shows the main parts of the control functions for various controls in the hybrid vehicle 10. The hybrid vehicle 10 in this embodiment is a hybrid vehicle with front-engine rear-wheel drive (FR) as the basis, but it may also be a four-wheel drive vehicle with a front-engine front-wheel drive (FF) as the basis.

[0012] The hybrid vehicle 10 is a vehicle capable of four-wheel drive, comprising an engine 12, a pair of left and right front wheels 14, a pair of left and right rear wheels 16 which are drive wheels, and a power transmission device 18. The hybrid vehicle 10 can also be used for plug-in hybrid vehicle (PHEV) applications. In the hybrid vehicle 10, as is well known, an electronic control device 100 alternates between an engine driving mode, in which the vehicle is driven using the engine 12, and an electric motor driving mode, in which the vehicle is driven exclusively using the first electric motor MG1 and / or the second electric motor MG2 without using the engine 12, depending on the vehicle driving conditions, in order to improve fuel efficiency, and the engine 12 is operated intermittently. The first electric motor MG1 and the second electric motor MG2 are preferably composed of motor generators.

[0013] The power transmission device 18 is equipped with, in order, a K0 clutch 20 for engaging and disengaging the engine 12, a first electric motor MG1, a torque converter 22, an automatic transmission 24, a transfer case 26, and a second electric motor MG2 in the power transmission path following the engine 12. The engine 12 and the first electric motor MG1 function as a drive unit during HV driving. A portion of the driving force transmitted from this drive unit to the transfer case 26 via the automatic transmission 24 is transmitted to the left and right rear wheels 16 via the rear propeller shaft 28 and differential 30, while the other portion of the driving force is transmitted to the left and right front wheels 14 via the front propeller shaft 32 and differential 34. The second electric motor MG2, located downstream of the transfer case 26, is mounted coaxially with the rear propeller shaft 28 to drive the rear propeller shaft 28, but may also be mounted parallel to the rear propeller shaft 28 and connected to the rear propeller shaft 28 via a gear pair.

[0014] The torque converter 22 is a well-known one, comprising a pump impeller 36 connected to the first electric motor MG1, a turbine impeller 38 connected to the automatic transmission 24, and a lock-up clutch 40 connecting the pump impeller 36 and the turbine impeller 38. The automatic transmission 24 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 a plurality of hydraulic friction engagement devices that can be selectively engaged to form a plurality of gear stages with different gear ratios γ (= AT input rotational speed Ni / AT output rotational speed No).

[0015] The transfer case 26 is configured as shown in Figure 2, for example. The transfer case 26 is equipped with a TF input shaft 62 connected to the output shaft of the automatic transmission 24, a high / low gear selector 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 rear wheels 16, all on a first axis CL1 which is the same axis as the output shaft of the automatic transmission 24. Driving force is transmitted from the rear wheel side output shaft 68 to the rear propeller shaft 28. The transfer case 26 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 32.

[0016] 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 60. 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 a D1 switching signal Sd1 output from the electronic control unit 100, and the high / low switching device 64 is switched between high gear Hi and low gear Lo. Furthermore, when the HL switching sleeve 86 is positioned between high gear Hi and low gear Lo by the D1 switching signal Sd1, it 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.

[0017] 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.

[0018] A differential lock clutch D2 is provided between the sun gear S2 and the carrier C2 of the center differential 66 as a differential rotation restricting device. The differential lock clutch D2 is a meshing clutch without a synchronization mechanism, and includes meshing teeth 90 provided on the sun gear S2, meshing teeth 92 provided on the carrier C2, and a differential sleeve 94 that is disposed so as to be axially movable and has meshing teeth meshed with the meshing teeth 90 and 92. The differential sleeve 94 is constantly meshed with one of the meshing teeth 90 and is reciprocally moved axially by a hydraulic actuator, so as to be meshed with the other meshing teeth 92 to connect the sun gear S2 and the carrier C2 so as to be non-rotatable relative to each other for differential lock, or to release the meshing with the other meshing teeth 92 to allow relative rotation between the sun gear S2 and the carrier C2, that is, differential rotation of the center differential 66, for free. The differential sleeve 94 is controlled by a D2 switching signal Sd2 output from the electronic control device 100 to be moved axially, and the center differential 66 is switched between free and differential lock.

[0019] Returning to FIG. 1, the hybrid vehicle 10 includes an electronic control device 100 as a control device for controlling the operations of each part such as the engine 12, the first motor MG1, the K0 clutch 20, the transfer 26, and the second motor MG2. The electronic control device 100 includes a so-called microcomputer and performs various controls by performing signal processing according to a program stored in advance.

[0020] The electronic control unit 100 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 opening sensor 120, throttle valve opening sensor 122, brake force sensor 124, wheel speed sensor 126, high / low state detection sensor 128, center 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, and accelerator Signals are supplied to represent the accelerator opening θacc corresponding to the amount the starter 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 detected by the wheel speed sensor 126, the vehicle speed V is determined.

[0021] The electronic control unit 100 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 selector 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, all of which are operated by the driver. The range selection device 140 is, for example, a shift lever that selects D range, L range, R range, P range, etc. If the high-low selector device 142 is operated to the low gear selection side, for example in L range, then four-wheel drive driving and low gear (Lo) are selected, and if it is operated to the high gear selection side, then four-wheel drive driving and high gear (Hi) are selected. The differential state selection device 144 is, for example, a differential lock selection switch that is operated when selecting differential lock during four-wheel drive driving, and if it is not operated, then it is set to free.

[0022] The electronic control device 100 calculates a required drive torque or the like based on the accelerator opening θacc, vehicle speed V, etc., and determines an engine running mode or an electric motor running mode based on the required drive torque from a pre-stored running mode map so that the required drive torque or the like can be obtained with minimum fuel consumption, and controls the engine torque Te and MG torque Tmg for engine running, or the MG torque Tmg for electric motor running. By such control, the engine 12 of the hybrid vehicle 10 is intermittently operated. Further, the electronic control device 100 executes shift control of the automatic transmission 24 according to a predetermined shift map.

[0023] The above electric motor running mode includes a series running mode and other electric motor running modes, for example, other electric motor running modes using the first electric motor MG1 and / or the second electric motor MG2. The above series running mode is a running mode in which, with the transfer 26 in a neutral state, running is performed only by the second electric motor MG2 disposed downstream of the transfer 26 using the generated electric power output from the first electric motor MG1 rotationally driven by the engine 12. The series running mode is requested or selected by the electronic control device 100 when a failure occurs such as that the automatic transmission 24 can only form a specific gear position or that power transmission cannot be performed due to component damage. Further, the series running mode is requested or selected by the electronic control device 100 when the fuel consumption of the series running mode is better than that of other running modes in which power is transmitted through the automatic transmission 24. The series running mode is suitable for the electric motor running with priority on the cruising distance of a plug-in hybrid vehicle (PHEV).

[0024] The electronic control device 100 functionally includes a series driving determination unit 150 that determines whether a series driving mode is requested or selected, in which the vehicle is driven solely by the second motor MG2 using the power generated by the first motor MG1, and a series driving control unit 152 that, if the series driving determination unit 150 determines that a series driving mode is requested or selected, switches the transfer case 26 to a neutral state and drives the second motor MG2 using the power generated by driving the first motor MG1 with the engine 12 to perform series driving.

[0025] Figures 3 and 4 are flowcharts illustrating the main parts of the control operation of the electronic control unit 100, respectively, and are performed in the electric motor driving mode. In the control operation of Figure 3, step S1 (hereinafter, steps will be omitted) corresponding to the function of the series driving determination unit 150 determines whether the automatic transmission 24 has failed, that is, whether the series driving mode is requested or selected. If the determination in S1 is negative, the execution of S1 is repeated. However, if the determination in S1 is positive, S2 and S3 corresponding to the function of the series driving control unit 152 are executed. In S2, the transfer case 26 is switched to neutral, and in S3, the first electric motor MG1 is driven by the engine 12, and electric motor driving is performed using only the second electric motor MG2 with the generated power output from the first electric motor MG1.

[0026] In the control operation shown in Figure 4, S11, which corresponds to the function of the series driving determination unit 150, determines whether the series driving mode is more fuel-efficient than other motor driving modes that transmit power via the automatic transmission 24, that is, whether the series driving mode is requested or selected. If the determination in S11 is negative, the execution of S11 is repeated. However, if the determination in S11 is positive, S12 and S13, which correspond to the function of the series driving control unit 152, are executed. In S12, the transfer case 26 is switched to neutral, and in S13, the engine 12 drives the first motor MG1, and motor driving is performed using only the second motor MG2 with the generated power output from the first motor MG1.

[0027] As described above, according to the electronic control device (control device) 100 of the hybrid vehicle 10 of this embodiment, when the series driving determination unit 150 determines that a series driving mode is requested or selected, the series driving control unit 152 sets the transfer case 26 to neutral and performs series driving using only the second motor MG2, using the power generated by the first motor MG1 driven by the engine 12. As a result, the hybrid vehicle 10 can run without problems in series driving mode, for example, in the event of a failure of the automatic transmission 24 or when the series driving mode is more fuel-efficient than other driving modes in which power is transmitted via the automatic transmission 24. In series driving, the engine 12 that drives the first motor MG1 is operated at the operating point that is optimal for fuel efficiency, so fuel efficiency can be improved, for example, in the low vehicle speed range.

[0028] 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]

[0029] 10: Hybrid vehicle, 12: Engine (drive unit), 14: Front wheels, 16: Rear wheels (drive wheels), 24: Automatic transmission, 26: Transfer case, 100: Electronic control unit (control unit), 150: Series driving determination unit, 152: Series driving control unit, MG1: First motor (drive unit), MG2: Second motor

Claims

[Claim 1] A control device for a hybrid vehicle, which includes an automatic transmission and a transfer case in the power transmission path between a drive unit having an engine and a first electric motor and a drive wheel, A second electric motor is located downstream of the aforementioned transfer, A series driving determination unit determines whether a series driving mode is requested or selected, in which the vehicle is driven solely by the second motor using the power generated by the first motor, The series driving control unit includes, when it determines that a series driving mode is requested or selected by the series driving determination unit, a series driving control unit that switches the transfer case to a neutral state and drives the second motor using the power generated by driving the first motor with the engine. A control device for a hybrid vehicle characterized by the following features.

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