JP2005082047A - Driving control device of multi-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving switching control device of a multi-wheel drive vehicle capable of suitably preventing the lowering of durability of a power transmission system. <P>SOLUTION: Multi-wheel driving is fixed in a step S5 corresponding to a driving state control means while a shift ratio is decided to be a maximum value (that is, a gear stage is in the lst) in a step S1 corresponding to a shift ratio deciding means. The setting of the shift ratio to the maximum value is inhibited in a step S4 corresponding to a shift limiting means while no four-wheel driving is decided in a step S2 corresponding to a driving state deciding means. Therefore, driving is not performed by two-wheel driving at a lowest speed stage of an automatic transmission, driving torque normally transmitted to a driving wheel becomes low according to the shift ratio smaller than the driving torque at the time of the two-wheel driving. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for a multi-wheel drive vehicle capable of switching between two-wheel drive and four-wheel or more multi-wheel drive.

There is known a multi-wheel drive vehicle configured to be able to switch between multi-wheel drive (for example, four-wheel drive) and two-wheel drive. In such a multi-wheel drive vehicle, the drive is switched manually according to the driver's intention or automatically according to the traveling state of the vehicle. In other words, two-wheel drive enables driving with excellent fuel consumption rate, and multi-wheel drive improves driving stability and bad road running performance, so it can be switched to a desired driving state according to the desired or road surface. . For example, the rear wheel is configured as a constantly driven wheel that is directly connected to the engine, and the front wheel is connected to the rear wheel via a transfer equipped with a clutch. An example is a four-wheel drive vehicle that switches between driving. During four-wheel drive running, the driving force distribution of the front and rear wheels, that is, the distribution torque is controlled according to the running state of the vehicle by changing the clutch engagement force (see, for example, Patent Document 1).
JP 2001-287557 A JP-A-4-257742 JP-A-9-249050 JP 7-315071 A

  By the way, the switching mechanism between the multi-wheel drive and the two-wheel drive in the multi-wheel drive vehicle is configured to be switched in conjunction with the change of the transmission gear ratio and to be switched independently. There are cases. For example, when the transfer has a low speed stage and a high speed stage (L / H), the drive switching lever is set to H2-H4-L4 (where H is the high speed stage, L is the low speed stage, and 2 is the two-wheel drive. (4 indicates four-wheel drive) so that the setting can be changed between settings, and the switching of the driving state and the change of the gear ratio are linked. In addition, when the transfer is switched to two-wheel drive, the control valve is operated in conjunction with this to prohibit the low speed stage from being achieved. On the other hand, when the switching between the multi-wheel drive and the two-wheel drive is performed by a dedicated changeover switch or the like, even if the transfer is provided with L / H switching, the change of the gear ratio is The driving state is switched independently. In addition, when the transfer is not provided with L / H switching, the driving state is inevitably switched independently of the change of the gear ratio.

  However, it is difficult to mechanically prohibit two-wheel drive at a relatively large gear ratio, for example, the maximum gear ratio, in a configuration in which the driving state is switched independently of the change in the gear ratio. Therefore, in the case where switching to multi-wheel drive is not possible due to a failure of the hydraulic control solenoid valve of the transfer, etc., excessive drive torque corresponding to multi-wheel drive can be transmitted to the constantly driven wheels during two-wheel drive. . As a result, when the driving torque exceeds the frictional force with the road surface, the driving wheel always slips, or when the driving wheel is always subjected to some restraint, the durability of the power transmission system may be reduced. there were.

  The present invention has been made in the background of the above circumstances, and its object is to provide an excessive driving torque for a constant driving wheel in a multi-wheel drive vehicle in which a driving state is switched independently of a change in gear ratio. It is an object of the present invention to provide a drive control device that can suitably prevent the transmission of noise.

  In order to achieve such an object, the gist of the first invention is that the transmission provided between the prime mover and the drive wheels, and the multi-wheel drive and the two-wheel drive independently of the change of the transmission gear ratio of the transmission. A drive control device for a multi-wheel drive vehicle, comprising: (a) a gear ratio determining means for determining that the gear ratio of the transmission is equal to or greater than a predetermined value; And (b) drive state control means for bringing the drive wheel switching device into a multi-wheel drive state while the determination by the gear ratio determination means is affirmed.

  The gist of the second invention is a transmission provided between the prime mover and the drive wheel, and a drive wheel capable of switching between multi-wheel drive and two-wheel drive independently of a change in the gear ratio of the transmission. A drive control device for a multi-wheel drive vehicle comprising a switching device, wherein (a) drive state determination means for determining that the vehicle is multi-wheel drive, and (b) determination by the drive state determination means is denied. And a shift limiting means for prohibiting the transmission gear ratio of the transmission from being set to a value equal to or greater than a predetermined value.

  According to this configuration, in the first aspect of the invention, the drive wheel switching device is set to the multi-wheel drive state by the drive state control means while it is determined by the speed ratio determination means that the speed ratio is not less than the predetermined value. . In the second aspect of the present invention, while the drive state determining means determines that the multi-wheel drive is not performed, setting the speed ratio to a predetermined value or more is prohibited by the shift limiting means. Therefore, in any case, a multi-wheel drive state is established at a gear ratio greater than a predetermined value, so that the drive torque transmitted to the drive wheels at the time of two-wheel drive is always a low value corresponding to the gear ratio smaller than the predetermined value. Become. Therefore, it is suppressed that an excessive driving torque is transmitted to the power transmission system during two-wheel drive, and thus it is possible to suppress slipping of the driving wheels and a decrease in durability of the power transmission system.

  The gear ratio determining means is not limited to determining the transmission gear ratio value itself, but substantially determines the gear ratio value based on the gear position of the transmission, the operation position of the shift lever, and the like. Something to do is also included.

  Preferably, in the first invention, the drive control device for the multi-wheel drive vehicle includes a start time determining means for determining that the vehicle is starting, and the speed ratio determining means is When the determination of the time determination means is affirmed, it is determined that the transmission gear ratio is a value greater than or equal to a predetermined value. In this way, the friction ratio between the drive wheels and the road surface is large compared to when driving, and the drive wheels are likely to be restrained. Therefore, slipping of the drive wheels and a decrease in durability of the power transmission system are further suppressed.

  Preferably, the drive control device for a multi-wheel drive vehicle according to the second invention is a switching failure determination means for determining the presence or absence of a failure of the driving wheel switching device when the determination by the driving state determination means is denied. The shift limiting means prohibits the transmission gear ratio from being set to a value greater than or equal to the predetermined value while a failure is determined by the switching failure determination means. In this way, when the multi-wheel drive is not performed due to the failure of the drive wheel switching device, the gear ratio is prohibited from being a predetermined value or more by the shift limiting means. That is, even in the case of non-multi-wheel drive, drive switching is executed as it is in a transition period after the switching condition from two-wheel drive to multi-wheel drive that is not a failure of the drive wheel switching device is established. Become.

  Preferably, in the second aspect of the invention, the drive control device for the multi-wheel drive vehicle includes start time determination means for determining that the vehicle is starting, and the drive state determination means is for the start time. When the determination by the determination means is affirmed, it is determined that the vehicle is multi-wheel drive. In this way, the frictional force between the drive wheel and the road surface is large compared to when driving, and the drive state is determined and the gear ratio is increased when starting from a stationary state where the drive wheel is likely to be restrained. Since it is prohibited to set the value to a value greater than or equal to a predetermined value, the slip of the drive wheels and the decrease in durability of the power transmission system are further suppressed.

  Preferably, in the first and second inventions, the drive control device for the multi-wheel drive vehicle includes switching instruction means for instructing the drive wheel switching device to switch driving, and the switching failure determination means includes When the switching instruction means instructs to switch to multi-wheel drive, it is determined whether or not the driving wheel switching device has failed. In this way, the fail determination is performed only when an instruction to switch to multi-wheel drive is generated by a driver's operation or by automatic vehicle control.

  Preferably, in the first and second inventions, preferably, the drive wheel switching device is operated independently or independently of a change in the transmission gear ratio of the transmission. As a result, the multi-wheel drive and the two-wheel drive can be switched.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a skeleton diagram illustrating the configuration of a power transmission device 10 for a hybrid vehicle to which the present invention is applied. In the figure, for example, the output of the engine 12 as a driving force source for traveling constituted by an internal combustion engine is passed through an input clutch 14 and a torque converter 16 as a fluid transmission device, and a first transmission unit 18 and a second transmission unit. 20 is transmitted to a drive wheel, that is, a rear wheel 25 and a front wheel 27 via a differential gear device 21, 23 and an axle through a transfer device 24. In the present embodiment, the engine 12 corresponds to a prime mover, and the transfer device 24 corresponds to a drive wheel switching device.

  Between the input clutch 14 and the torque converter 16, a first motor / generator MG1 that functions as an electric motor and a generator (that is, a motor generator) as a rotating machine is disposed. The torque converter 16 includes a pump impeller 28 connected to the input clutch 14 via the crankshaft 26 of the engine 12, a turbine impeller 32 connected to the input shaft 30 of the automatic transmission 22, and the pump impellers. A lock-up clutch 34 for directly connecting the vehicle 28 and the turbine impeller 32, and a one-way clutch 36 prevent rotation in one direction, and an angle actuator 38 can change the angle with respect to the turbine impeller 32. A stator impeller 40.

  The lock-up clutch 34 is a hydraulic friction clutch that is frictionally engaged by a differential pressure ΔP between the hydraulic pressure in the engagement-side oil chamber 42 and the hydraulic pressure in the release-side oil chamber 44. As a result, the pump impeller 28 and the turbine impeller 32 are rotated together. Further, the differential pressure ΔP, that is, the engagement torque is feedback-controlled so as to be engaged in a predetermined slip state, so that when the vehicle is driven (power-on), the turbine blades have a predetermined target slip amount of, for example, about 50 (rpm). While the vehicle 32 is rotated following the pump impeller 28, when the vehicle is not driven (powered off), the pump impeller 28 is moved relative to the turbine impeller 32 with a predetermined target slip amount of, for example, about −50 (rpm). Follow and rotate.

  The automatic transmission 22 is a stepped automatic transmission in which a plurality of gear stages are selectively established, that is, switched. The first transmission unit 32 is mainly composed of a double pinion type first planetary gear unit 46, and the second transmission unit 34 is composed of a single pinion type second planetary gear unit 48 and a single pinion type third planetary gear unit 46. The gear unit 50 and the single pinion type fourth planetary gear unit 52 are mainly configured to shift the rotation of the input shaft 30 and output it from the output shaft 54.

  The first planetary gear unit 46 includes a sun gear S1, a ring gear R1, and a pinion gear (not shown) that is rotatably supported by the carrier CA1 and meshed with the sun gear S1 and the ring gear R1. The carrier CA1 is connected to the input shaft 30 and is driven to rotate about its axis. The sun gear S1 is integrally fixed to the case 56 so as not to rotate. The ring gear R1 is rotated at a reduced speed with respect to the input shaft 30 as an intermediate output member. And transmitted to the second transmission 20.

  The second planetary gear unit 48 is composed of a sun gear S2, a ring gear R2, and a pinion gear rotatably supported by the carrier CA2 and meshed with the sun gear S2 and the ring gear R2. The ring gear R1 and the sun gear S2 are selectively connected to the ring gear R1 via the clutches C1 and C2, and the ring gear R2 is connected to the carrier CA1 via the clutch C3 that is selectively engaged with the clutch C1. Is selectively linked. The ring gear R2 is selectively connected to the case 56 by the brake B1 and stopped.

  The third planetary gear unit 50 is composed of a sun gear S3, a ring gear R3, and a pinion gear rotatably supported by the carrier CA3 and meshed with the sun gear S3 and the ring gear R3. The sun gear S3 is selectively connected to the ring gear R1 via the clutch C2, and the carrier CA3 is selectively connected to the carrier CA1 and the input shaft 30 via the clutch C4. That is, the sun gear S2 and the sun gear S3 are integrally connected to each other. Further, the ring gear R3 is integrally connected to the carrier CA2 of the second planetary gear device 48, and is selectively connected to the case 56 by the brake B2 and stopped.

  The fourth planetary gear unit 52 includes a sun gear S4, a ring gear R4, and a pinion gear rotatably supported by the carrier CA4 and meshed with the sun gear S4 and the ring gear R4. The carrier CA4 is integrally connected to the carrier CA3 of the third planetary gear device 50, and is selectively connected to the case 56 by the brake B3 and stopped. That is, the carrier CA4 is also selectively coupled to the carrier CA1 and the input shaft 30 via the clutch C4. The ring gear R4 is integrally connected to the ring gear R3 of the third planetary gear device 50. The sun gear S4 is coupled to the output shaft 54.

In the automatic transmission 22 configured as described above, for example, in accordance with the operation table shown in FIG. 2, the reverse speed and the gear ratio γ (the rotational speed N _IN of the input shaft 30 / the rotational speed N _OUT of the output shaft 54) are successively decreased. Is switched to any one of the 9 forward gear stages (1st to 9th). In FIG. 2, “◯” represents engagement of the brakes B1 to B3 and the clutches C1 to C4, and a blank represents release. The clutches C1 to C4 and the brakes B1 to B3 are all hydraulic friction engagement devices that are engaged by a hydraulic actuator.

  Returning to FIG. 1, the transfer device 24 includes a pair of pulleys 60 and 62 around which a timing belt 58 and the like are wound, a transfer clutch TFC for selectively connecting the pulley 60 to the output shaft 54, and the like. It consists of and. The transfer device 24 outputs the driving force transmitted from the engine 12 to the rear wheel 25 via the output shaft 54, and when the clutch TFC is engaged, the pulley 60, the belt 58, the pulley 62, and the front wheel output shaft. A part of the transmitted driving force is transmitted to the front wheel 27 via 64. The clutch TFC is also a hydraulic friction engagement device that is engaged by a hydraulic actuator or the like, and the power is transmitted to the front and rear wheels 25 and 27 by controlling the engagement pressure to change the engagement state. The front-rear wheel drive force distribution ratio in the range from the four-wheel drive state driven by the vehicle to the two-wheel drive state driven by transmitting power to one of the front wheels 27 and the rear wheels 25 (rear wheel 25 in this embodiment). Change. In the present embodiment, the rear wheel 25 directly connected to the output shaft 54 is a constant drive wheel.

  FIG. 3 is a diagram schematically showing the configuration of the power transmission device 10 shown in FIG. In the figure, an exhaust turbine supercharger 70 is provided in an intake pipe 66 and an exhaust pipe 68 of the engine 12. The exhaust turbine supercharger 70 is provided in a turbine impeller 72 that is rotationally driven by an exhaust flow in an exhaust pipe 68, an intake pipe 66 for compressing intake air to the engine 12, and a turbine blade. A pump impeller 74 connected to the wheel 72 is provided, and the pump impeller 74 is rotationally driven by the turbine impeller 72. The intake pipe 66 is provided with an electronic throttle valve 78 that is controlled to be opened and closed by a throttle actuator 76. The engine 12 is composed of left and right banks that can be operated independently or simultaneously, and the number of cylinders that actually contribute to driving can be changed by switching the banks.

  The first motor / generator MG1 is disposed between the engine 12 and the gear transmission mechanism of the automatic transmission 22 so as to be operatively connected to the engine 12, and the input clutch 14 is connected to the engine 12 and the first gear. It is arranged between the motor generator MG1. Each hydraulic friction engagement device and the lock-up clutch 34 of the automatic transmission 22 are controlled by a hydraulic control circuit 82 that uses, for example, a line pressure due to the hydraulic pressure generated from the electric hydraulic pump 80 as a source pressure. Yes. The line pressure is the maximum engagement pressure that is used to engage each hydraulic friction engagement device of the automatic transmission 22.

  The engine 12 is operatively connected to a second motor / generator MG2 that functions as an electric motor or a generator as a rotating machine. Further, the first motor / generator MG1 and the second motor / generator MG2 also function as a rotational drive device that assists the rotational drive of the engine 12 by the operation thereof. is there. Then, the fuel cell 84 and the secondary battery 86 functioning as a power source for the first motor / generator MG1 and the second motor / generator MG2, and the first and second motor / generators MG1 and MG2 are supplied from them. Power supply changeover switches 88 and 90 are provided for controlling the current or controlling the current supplied to the secondary battery 86 for charging. The power supply changeover switches 88 and 90 indicate devices having a switch function, and may be constituted by, for example, a semiconductor switching element (not shown) having an inverter function or the like.

FIG. 4 is a block diagram illustrating a control system for the power transmission device 10, and illustrates a signal input to the electronic control device 92 and a signal output from the electronic control device 92. For example, the electronic control unit 92 includes an accelerator opening signal indicating an accelerator opening Acc that is an operation amount of an accelerator pedal detected by an accelerator opening sensor, and a throttle valve 62 detected by a throttle valve opening sensor 94. A throttle valve opening signal indicating the valve opening θ _TH , a rotation speed N _OUT of the output shaft 54 detected by the output shaft rotation speed sensor, that is, a vehicle speed signal corresponding to the vehicle speed V, and a turbine rotation speed detected by the turbine rotation speed sensor N _T signals representing the (= rotational speed N _iN of the input shaft 30), a signal indicative of engine rotational speed N _E detected by the engine speed sensor, signals representing the supercharge pressure P _a in the intake pipe 66, the air-fuel ratio signal representative of a / F, the signal representing the operation position P _SH of the shift lever 96, a signal representing the presence or absence of depression of 2WD⇔4WD changeover switch 98, the transmission Such second hydraulic oil temperature, ie AT oil temperature T _OIL is supplied from a sensor (not shown).

Further, the electronic control unit 92 controls a signal for driving the throttle actuator 76 for setting the throttle valve opening θ _TH having a magnitude corresponding to the accelerator opening Acc, and the amount of fuel injected from the fuel injection valve. An injection signal for switching, signals S1, S2, and S3 for controlling a shift solenoid for driving a shift valve in the hydraulic control circuit 82 for switching the gear stage of the automatic transmission 22, and a line pressure for controlling a clutch-to-clutch shift. Command signal D _SLT for driving the linear solenoid valve SLT for controlling the gear, command signal D _SLU for driving the linear solenoid valve SLU for controlling the engagement, disengagement, and slip amount of the lockup clutch 34, and accum back pressure The command value signal D _{SLN and the} like for driving the linear solenoid valve SLN for controlling the motor are respectively output.

The electronic control unit 92 includes a so-called microcomputer including a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Basically, for example, the throttle valve opening control for controlling the throttle valve opening θ _TH (%) of the electronic throttle valve 78, the shift control for automatically switching the gear stage of the automatic transmission 22, the engine 12 Output control, lock-up clutch control for engaging, releasing or slipping the lock-up clutch 34, supercharging pressure control, air-fuel ratio control, cylinder selection switching control, operation cycle switching control, 2WD-4WD switching control, Cooperative control between the number of drive wheels and the gear position is executed.

In the drive torque control, for example, the clutch C1 slip control that changes the slip amount by changing the engagement pressure of the clutch C1 between the first transmission unit 18 and the second transmission unit 20 and the angle actuator 38 are driven. Thus, torque ratio change control of the torque converter 16 for changing the stator angle, torque regeneration control by rotating the first motor generator MG1 by the crankshaft 26, and the like are performed. In the shift control, for example, the actual accelerator opening Acc (%) or the throttle valve opening is detected from the detection result of whether the driving state is two-wheel drive or four-wheel drive, or the relationship stored in advance, that is, the shift diagram. Based on the degree θ _TH (%) and the vehicle speed V (km / h), the gear stage of the automatic transmission 22 is determined, and the electromagnetic force of the hydraulic control circuit 82 is obtained so that the determined gear stage and the engaged state are obtained. Drive the valve.

  Further, in the above-described linkage control, for example, in the case of two-wheel drive, the shift limit control for prohibiting the shift stage of the automatic transmission 22 from being set to 1st, that is, setting to the maximum gear ratio, When the gear position is set to 1st, the drive state control etc. which make the transfer apparatus 24 a multi-wheel drive state are performed. In this drive state control, for example, in the multi-wheel drive state, switching to the two-wheel drive is prohibited and maintained in that state, and in the two-wheel drive state, the multi-wheel drive is switched.

  In addition, as schematically shown in FIG. 5, the shift operation device 100 operated to select a plurality of types of shift positions (operation positions of the shift lever 96) provided with the shift lever 96 is provided, for example, on the side of the driver's seat. The shift lever 96 has a parking position for locking the output shaft 54 of the automatic transmission 22, that is, the P position, a reverse traveling position for reverse traveling, that is, the R position, and the automatic transmission 22. Automatic shift in the range from the first gear to the ninth gear in the automatic shift mode in which the automatic transmission of the automatic transmission 22 is executed in the neutral position that is the neutral state where the power transmission path is cut off, that is, the N position. Before the forward traveling position for selecting the D range, that is, the D position, and a plurality of shift ranges having different shift speeds on the high speed side can be switched. It is operably disposed respectively to the running position or M position. Each of the shift positions shown in the P to M positions is a non-travel position that is selected when the vehicle does not travel, the R position is a reverse travel position for causing the vehicle to travel backward, and D The position and the M position are forward travel positions for causing the vehicle to travel forward.

  In the above-mentioned M position, any one of the five different shift ranges of the D range corresponding to the D position which is the highest speed position, and the 4 ranges, 3 ranges, 2 ranges and L ranges which are sequentially lower in comparison with the D range. Is established electrically. The fourth range is a fourth engine brake travel position at which automatic transmission is performed in the range from the first gear to the fourth gear and the engine brake is applied at each gear. The third range is the first gear. Or the third engine brake travel position where the automatic transmission is performed in the range of the third speed gear stage and the engine brake is applied at each gear stage, and the second range is the range of the first speed gear stage to the second speed gear stage. The second engine brake travel position where the gear is automatically shifted and the engine brake is applied at each gear stage, and the L range is the first engine brake travel position where the engine brake is operated and the engine brake is applied. is there. That is, these 4 ranges to L ranges are positions for increasing the driving force of the vehicle and engine brake travel positions for engine brake travel.

  The M position is provided adjacent to the width direction of the vehicle at the same position as the D position in the longitudinal direction of the vehicle. When the shift lever 96 is operated to the M position, the D position to the L range are provided. For example, the range up to that point is established electrically. Specifically, an upshift position “+” and a downshift position “−” are provided in the longitudinal direction of the vehicle at positions adjacent to the front and rear of the “M” position, respectively. When operated to the upshift position “+” or the downshift position “−”, etc., five shift ranges (shift ranges) “D”, “4”, “3”, “2” with different maximum speed gears , “L” is electrically established. This shift range may be detected by a shift detection switch 102 described later for detecting each operation position including the M position.

  The shift lever 96 is automatically returned from the upshift position “+” and the downshift position “−” to the “M” position by an urging means such as a spring, and the upshift position “+”. Alternatively, the shift range is changed according to the number of operations to the downshift position “−” or the holding time. Further, for example, the initial setting range of the M position is 4 ranges, and each time the shift lever 96 is operated to the downshift position “−”, it is sequentially switched to the L range side, and the shift lever 96 is operated to the upshift position “+”. Each time it is switched to the D range side. That is, at the M position of the shift operation device 100, a shift range corresponding to each shift position of the shift operation device 100, that is, the operation position of the shift lever 96 switched by manual operation is electrically established.

  In addition, at the same position as the M position in the longitudinal direction of the vehicle and on the opposite side of the D position in the width direction of the vehicle, the 2WD⇔4WD changeover switch (that is, the drive change button) 98 is set to the M position. Adjacent to each other. The changeover switch 98 is, for example, a push button switch, and sets the driving state of the vehicle to four-wheel driving by being pushed down, for example, while being driven by a biasing means such as a spring to drive the vehicle. The state is set to two-wheel drive. Specifically, when the changeover switch 98 is depressed, the solenoid for controlling the hydraulic pressure of the clutch TFC is driven to increase the engagement hydraulic pressure, the clutch TFC is engaged, and the pulley 60 is connected to the output shaft. 54, the front wheel output shaft 64 for driving the front wheel 27 is rotated in addition to the output shaft 54 for driving the rear wheel 25. Therefore, the drive torque transmitted to the output shaft 54 via the torque converter 16 and the automatic transmission 22 is distributed to the front and rear wheels 25 and 27 and transmitted to the front and rear wheels 25 and 27, respectively, and the vehicle is driven by four-wheel drive. On the other hand, when the changeover switch 98 is returned, the solenoid is driven and the engagement hydraulic pressure of the clutch TFC is lowered and released, so that the connection between the output shaft 54 and the pulley 60 is released. Is transmitted to the rear wheel 25 set to always drive, and the vehicle is driven by two-wheel drive. The switching state of the changeover switch 98 is detected by the changeover sensor 104, for example. In the present embodiment, the switching between the two-wheel drive and the four-wheel drive is performed independently of the switching of the gear stage of the automatic transmission 22 in this way.

  FIG. 6 is a functional block diagram for explaining a main part of a control function for executing the drive control provided in the electronic control unit 92, particularly the cooperative control. In the figure, when the changeover switch 98, that is, the drive changeover button 98 is pushed, the engagement pressure of the clutch TFC is increased as described above to change to the four-wheel drive mode. Further, the gear ratio determination means 106 determines whether or not the current gear ratio is the maximum value based on the gear position of the automatic transmission 22 and the operation position of the shift lever 96. That is, it is determined whether or not the speed is currently set to the lowest speed (that is, the L range).

  The drive state determination means 108 determines whether the drive state is two-wheel drive or four-wheel drive based on, for example, an output signal of a hydraulic sensor (not shown) that detects the engagement pressure of the clutch TFC. This determination may be performed at any time. For example, it is detected by the switching sensor 104 that the drive switching button 98 has been pressed, or the speed ratio determining means 106 detects that the speed is the lowest speed. Implemented in some cases. This determination is executed regardless of whether or not the drive switching button 98 is depressed, that is, whether or not the four-wheel drive is set by the driver's operation. The switching failure determination unit 110 determines whether or not the switching to the four-wheel drive is not possible due to the failure of the transfer device 24 or the like when the driving state determination unit 108 determines that the two-wheel driving is performed. That is, for example, it is determined whether the transition to four-wheel drive is in progress or whether switching to four-wheel drive has failed due to failure of the clutch TFC or disconnection of a solenoid for controlling the hydraulic pressure.

  Since it is in a transient state when it is determined by the switching failure determination means 110 that it is not a failure, when the clutch TFC of the transfer device 24 is engaged by the drive switching means 112, it is switched to four-wheel drive. On the other hand, when it is determined that a failure has occurred, that is, the switching has failed, control by the shift limiting means 114 is executed, and the shift stage of the automatic transmission 22 is prohibited from being set to 1st. This shift limiting means 114 is executed, for example, by prohibiting engagement of the brake B3 by hydraulic control or mechanically. Note that the shift limiting means 114 may be executed immediately without passing through the determination by the switching failure determination means 110, for example, when the drive state determination means 108 determines that the two-wheel drive is being performed. In the case of such a configuration, for example, in a transitional state and when the transition to the four-wheel drive is completed later, when the drive state determination unit 108 determines that the four-wheel drive is performed, the shift restriction is performed. The shift limitation by means 114 is released.

  Further, the drive state control means 116 determines that the drive changeover button 98 is activated when the speed ratio determining means 106 determines that the speed ratio is the maximum value, that is, when the current gear is determined to be 1st. Switching from four-wheel drive to two-wheel drive is prohibited regardless of the operating state. This drive state control means 116 is executed, for example, by maintaining the engagement hydraulic pressure of the clutch TFC at a high value that maintains the engagement, or by mechanically engaging the pulley 60 with the output shaft 54. .

  FIG. 7 is a flowchart for explaining a drive control operation when it is determined that the main part of the control operation of the electronic control unit 92, that is, the gear stage of the automatic transmission 20 is 1st. This control flow is executed, for example, when the vehicle starts. In the figure, in step S1 corresponding to the gear ratio determining means 106, it is determined whether or not the current gear stage is the lowest speed stage. For example, when the vehicle is always configured to start at the lowest speed, this determination is always affirmed at the time of starting, but usually the vehicle starts at 2nd and four-wheel drive is designated by the drive switching button 98. In the case where the vehicle is configured to start at 1st only when the vehicle is on, this determination is affirmed only when the drive switching button 98 is depressed. If the determination in step S1 is negative, the flow is immediately terminated. If the determination is affirmative, the process proceeds to step S2.

  In step S2 corresponding to the drive state determination means 108, it is determined whether or not the vehicle is currently driven on four wheels, for example, based on whether or not the clutch TFC of the transfer device 24 is engaged. If this determination is affirmed, this flow is immediately terminated. If the determination is negative, the process proceeds to step S3. In step S3 corresponding to the switching failure determination means 110, it is determined whether or not the four-wheel drive has not been achieved due to a solenoid failure of the clutch TFC or the like. If this determination is affirmed, the process proceeds to step S4. If the determination is negative, the process proceeds to step S5.

  In step S4 corresponding to the shift limiting means 114, the gear stage is prohibited from being set to 1st, for example, by fixing the brake B3 in the released state. For example, when the current gear stage is 1st, the brake B3 is released and the brake B2 is engaged, whereby the gear stage is changed to 2nd. Therefore, the drive torque transmitted from the input shaft 30 is reduced by a magnitude corresponding to the reduction in the gear ratio of the automatic transmission 22 and transmitted to the output shaft 54. As a result, even if the two-wheel drive is driven only by the rear wheel 25, the drive torque transmitted to the rear wheel 25 is preferably prevented from becoming an excessive value corresponding to the four-wheel drive. That is, when the four-wheel drive is not performed, it is prohibited that the gear stage becomes the lowest speed, that is, 1st and the speed ratio becomes maximum.

  On the other hand, in step S5 corresponding to the drive switching means 112, an operation signal is sent to the solenoid of the clutch TFC regardless of whether or not the drive switch button 98 is depressed, thereby operating the solenoid and engaging the clutch TFC. Is changed to four-wheel drive. That is, at the lowest speed stage, the transfer device 24 is controlled so as to be four-wheel drive. In this case, the release of the brake B3 for limiting the drive torque is not executed.

  As described above, according to this embodiment, while it is determined in step S1 corresponding to the gear ratio determination means 106 that the gear ratio is the maximum value (that is, the gear stage is 1st), the drive state control means 116. In step S5 corresponding to, the multi-wheel drive is fixed. In addition, while it is determined in step S2 corresponding to the drive state determination means 108 that the four-wheel drive is not performed, setting the speed ratio to the maximum value is prohibited in step S4 corresponding to the shift restriction means 114. Therefore, since it is not driven by two-wheel drive at the lowest speed of the automatic transmission 22, the drive torque transmitted to the drive wheels at the time of two-wheel drive is a low value corresponding to a smaller gear ratio. Therefore, it is suppressed that excessive drive torque is transmitted to the power transmission system during two-wheel drive, and thus the rear wheel 25 is prevented from slipping and the power transmission system from being deteriorated in durability.

  Further, in this embodiment, when the determination in step S2 corresponding to the drive state determination unit 108 is denied, step S3 corresponding to the switching failure determination unit 110 that determines the presence or absence of the failure of the transfer device 24 is provided. The shift limiting unit 114 prohibits the automatic transmission 22 from setting the transmission ratio to the maximum value while the switching failure determination unit 110 determines that a failure has occurred. When the driving is not performed, the shift limiting means 114 prohibits the lowest speed stage. That is, if no failure is recognized even in the case of two-wheel drive, it is forcibly changed to four-wheel drive, so that excessive drive torque is prevented from being applied to the rear wheel 25.

  In this embodiment, the transfer device 24 and the automatic transmission 22 are configured such that the settings are changed independently of each other as described above. Is determined and is not switched, the drive torque transmitted to the power transmission system is lowered, so that excessive torque transmission to the drive wheels due to the configuration being changed independently. Is suitably suppressed.

  As mentioned above, although one Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the case where the present invention is applied to a vehicle that can be switched between four-wheel drive and two-wheel drive has been described. However, the present invention is similarly applied to a vehicle that can be switched to six or more wheels. The

  In the embodiment, the present invention is applied to a hybrid vehicle including the engine 12 and the first motor / generator MG1 as a prime mover. However, only the engine 12 or only the first motor / generator MG1 is provided as a prime mover. The present invention can be similarly applied to a vehicle.

  In the embodiment, the automatic transmission 22 is a stepped transmission of nine forward speeds and two reverse speeds including four sets of planetary gear units 46 to 52. However, the number of planetary gear units and the number of shift stage numbers are not limited. Is appropriately determined, and the present invention is similarly applied to a vehicle equipped with a continuously variable transmission.

  In the embodiment, the automatic transmission 22 is configured to change to four-wheel drive when the automatic transmission 22 is at the first speed, which is the lowest speed, and the drive wheel is always driven when the shift to the four-wheel drive fails. However, it is possible to set the gear ratio with a gear ratio of a predetermined value or more to be changed to four-wheel drive to a gear speed of 2nd or more with a smaller gear ratio. is there. Further, the shift speed at which the change to the low speed stage is prohibited during two-wheel drive may be set to 3rd or more.

  In the embodiment, the output shaft 54 is always connected to the rear wheel 25 so that the rear wheel 25 is always driven. However, the present invention is also applied to a vehicle that is driven two-wheels by the front wheel 27 on the contrary. The same applies.

  In the embodiment, the torque converter 16 is used as the fluid transmission device. However, a fluid coupling having no torque amplification function may be used.

  In the embodiment, the engine 12 and the motor generators MG1 and MG2 that are operatively connected to the engine 12 are provided as the prime mover. However, at least one of them is used for driving the drive wheels. The engine 12 may be provided as an engine, and the engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine. An exhaust turbine supercharger 70 provided in an intake pipe 66 and an exhaust pipe 68 of the engine 12 is provided. It can also be applied to vehicles that are not equipped. Motor generators MG1 and MG2 may be indirectly connected to engine 12 via a belt or the like in addition to being directly connected to engine 12.

  In the above-described embodiment, the clutch C, TFC, or brake B, which is the engagement element of the automatic transmission 22, is a hydraulic friction engagement device, but an electromagnetic engagement device such as an electromagnetic clutch or a magnetic powder clutch. Etc. When the clutch TFC is constituted by an electromagnetic clutch, the failure determination unit 110 determines whether or not there is a failure based on, for example, whether or not the electromagnetic clutch has failed.

  In addition, although not illustrated one by one, the present invention can be variously modified without departing from the gist thereof.

1 is a skeleton diagram illustrating a power transmission device of a hybrid vehicle to which the present invention is applied. FIG. 2 is a diagram illustrating a relationship between a combination of operations of a plurality of hydraulic friction engagement devices and a shift speed established thereby in the automatic transmission of FIG. 1. It is a schematic block diagram of the power transmission device of the hybrid vehicle of FIG. It is a block diagram explaining the principal part of the input-output system of the electronic controller with which the power transmission device of FIG. 1 is provided. It is a figure which shows an example of the shift operation apparatus provided in the vehicle of FIG. It is a functional block diagram explaining the principal part of the control function with which the electronic control apparatus of FIG. 4 is provided. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, that is, a shift prohibiting and drive switching prohibiting control operation.

Explanation of symbols

12: Engine, 16: Torque converter, 22: Automatic transmission, 24: Transfer device, 30: Input shaft, 54: Output shaft, 106: Gear ratio determination means, 108: Drive state determination means, 110: Switching failure determination Means: 112: drive switching means; 114: shift limiting means; 116: drive state control means; MG1: first motor generator; TFC: transfer clutch

Claims (3)

Driving a multi-wheel drive vehicle comprising a transmission provided between a prime mover and drive wheels and a drive wheel switching device capable of switching between multi-wheel drive and two-wheel drive independently of a change in the transmission gear ratio of the transmission A control device,
Gear ratio determining means for determining that the gear ratio of the transmission is a value equal to or greater than a predetermined value;
A drive control device for a multi-wheel drive vehicle, comprising: drive state control means for setting the drive wheel switching device in a multi-wheel drive state while the determination by the speed ratio determination means is affirmed. Driving a multi-wheel drive vehicle comprising a transmission provided between a prime mover and drive wheels and a drive wheel switching device capable of switching between multi-wheel drive and two-wheel drive independently of a change in the transmission gear ratio of the transmission A control device,
Drive state determination means for determining that the vehicle is multi-wheel drive;
Shift limiting means for prohibiting the transmission gear ratio from being set to a value equal to or greater than a predetermined value while the determination by the drive state determination means is negative. Drive control device. Including switching failure determination means for determining the presence or absence of failure of the driving wheel switching device when the determination by the driving state determination means is denied,
3. The multi-wheel drive according to claim 2, wherein the shift limiting unit prohibits the transmission gear ratio from being set to a value equal to or greater than the predetermined value while a failure is determined by the switching failure determination unit. Car drive control device.

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