JP6287567B2 - Control device for four-wheel drive vehicle - Google Patents

Description

  The present invention relates to a control device for a four-wheel drive vehicle including a connection / disconnection mechanism that connects / disconnects a power transmission path for transmitting a part of the power of a driving force source transmitted to a main drive wheel via a transmission to a sub drive wheel. Is.

  A transmission and disconnection mechanism for connecting and disconnecting the power transmission path provided in the power transmission path for transmitting a part of the power of the driving force source transmitted to the main drive wheel via the transmission to the sub drive wheel. A four-wheel drive vehicle equipped with is well known. For example, this is the vehicle described in Patent Document 1. In such a four-wheel drive vehicle, various proposals have been made regarding control in which a transmission and a connection / disconnection mechanism are associated with each other. For example, Patent Document 1 discloses that in such a four-wheel drive vehicle, the connection / disconnection mechanism is not engaged under a traction condition in which the transmission is in a neutral state.

US Pat. No. 8,204,657

  By the way, when the four-wheel drive (4WD) state is set, the transmission is switched from the non-travel range to the travel range, or the transmission travel range is switched between the forward travel range and the reverse travel range. Or when the transmission is switched to the parking range during traveling, or when the parking range switching of the transmission is performed during traveling, the torque temporarily generated with the range switching (hereinafter referred to as range switching torque) There is a possibility of being input to the power transmission path on the auxiliary drive wheel side. If the output torque of the driving force source is large (and / or the rotational speed of the driving force source is high) when the driving range is switched, or if the vehicle speed is high when the parking range is switched during driving, a large torque will be generated on the side of the auxiliary driving wheel. May be input to the power transmission path. On the other hand, if the component parts of the power transmission path on the side of the auxiliary drive wheels have a high-strength configuration, the physique of the component parts may increase or the fuel consumption may deteriorate due to an increase in the weight of the component parts. On the other hand, in a vehicle provided with a wet friction clutch capable of torque control as a connecting / disconnecting mechanism, it is conceivable to suppress torque input to the power transmission path on the auxiliary drive wheel side by torque control in the friction clutch. However, if the viscosity of the hydraulic fluid for the friction clutch is increased as at low temperatures, there is a possibility that appropriate torque control in the friction clutch becomes difficult. When a large torque is input to the power transmission path on the auxiliary drive wheel side, the durability of the components of the power transmission path may be reduced. Note that the above-described problem is not known, and no control has yet been proposed that relates the range switching of the transmission to the engagement control of the connection / disconnection mechanism.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to provide a four-wheel drive vehicle capable of suppressing a decrease in durability of components of the power transmission path on the side of the sub drive wheels. It is to provide a control device.

The subject matter of the first invention for achieving the above object is as follows: (a) The transmission and a part of the power of the driving force source transmitted to the main drive wheel through the transmission are sub-drive wheels. A control device for a four-wheel drive vehicle provided with a connecting / disconnecting mechanism for connecting / disconnecting the power transmission path provided in a power transmission path for transmitting to the vehicle, and (b) changing the transmission from a non-traveling range to a traveling range. When switching or switching between the forward travel range and the reverse travel range, the connection / disconnection mechanism is released or the connection / disconnection mechanism is released, and the engagement element associated with the range switching of the transmission is changed. (C) The transmission is switched from the non-travel range to the travel range, or the forward travel range and the reverse travel range are engaged after completion of engagement. when switching between the driving force The rotation speed of the driving force source at the start of engagement of the engagement element accompanying the range change of the transmission and the drive at the completion of engagement of the engagement element accompanying the range change of the transmission When any of the rotational speed difference from the rotational speed of the force source and the requested drive amount is equal to or greater than a predetermined value, the connection / disconnection mechanism is released or the connection / disconnection mechanism is released. It is in.

In this way, since the power transmission path on the auxiliary drive wheel side is cut off when the transmission range of the transmission is switched, it is avoided that the torque at the time of range switching is input to the power transmission path on the auxiliary drive wheel side. Is done. Therefore, it is possible to suppress a decrease in durability of the components of the power transmission path on the auxiliary drive wheel side. In particular, only when there is a possibility that a large torque may be input to the power transmission path on the side of the auxiliary drive wheel in accordance with the switching of the travel range of the transmission, the power transmission path on the side of the auxiliary drive wheel is interrupted, and the configuration It is possible to suppress a decrease in durability of the component.

The second invention is the control apparatus for a four wheel drive vehicle according to the first inventions, the oncoming of the engagement element with the switching range of the transmission, switching range of the transmission This is to wait until a predetermined time later or until the release of the connection / disconnection mechanism is completed. In this way, the power transmission path on the auxiliary drive wheel side is reliably interrupted when the engagement element is engaged with the range change of the transmission.

According to a third aspect of the present invention, in the control device for a four-wheel drive vehicle according to the first aspect or the second aspect, the connection / disconnection mechanism includes a wet friction clutch, When any one of the temperature of the driving force source, the temperature of the transmission, and the temperature of the friction clutch is not more than a predetermined value, the connection / disconnection mechanism is released or the connection / disconnection mechanism is released. It is to maintain. In this way, only when it is difficult to control the torque input to the power transmission path on the side of the auxiliary drive wheel by the friction clutch due to the low temperature of the hydraulic fluid of the friction clutch, The power transmission path is cut off, and a decrease in durability of the component parts can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a skeleton diagram explaining the schematic structure of the four-wheel drive vehicle to which this invention is applied, and is a figure explaining the principal part of the control system in a vehicle. It is a figure which shows an example of the parking mechanism which prevents rotation of a main drive wheel mechanically. It is a functional block diagram explaining the principal part of the control function of an electronic controller. It is a flowchart explaining the control action for suppressing the principal part of the control action of an electronic controller, ie, the durability reduction of the component of the power transmission path by the side of a rear wheel. It is a time chart at the time of performing the control action shown in the flow chart of Drawing 4, and is an example at the time of premised on 2WD running. It is a time chart at the time of performing the control action shown in the flowchart of Drawing 4, and is an example at the time of premised on 4WD running. FIG. 5 is a flowchart for explaining a control operation for suppressing a decrease in durability of a main part of the control operation of the electronic control unit, that is, a component of a power transmission path on the rear wheel side, and is an embodiment different from FIG. 4.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a skeleton diagram illustrating a schematic configuration of a four-wheel drive vehicle 10 (hereinafter referred to as a vehicle 10) to which the present invention is applied, and also illustrates a main part of a control system for various controls in the vehicle 10. FIG. In FIG. 1, a vehicle 10 includes an engine 12, left and right front wheels 14L and 14R (hereinafter referred to as front wheels 14 unless otherwise specified), and left and right rear wheels 16L and 16R (hereinafter referred to as rear wheels 16 unless otherwise specified). A first power transmission path for transmitting the power of the engine 12 to the front wheels 14 as a power transmission path between the engine 12 and the front wheels 14, and an engine as a power transmission path between the engine 12 and the rear wheels 16. A second power transmission path for transmitting 12 power to the rear wheel 16 is provided.

  The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine, and is a driving force source that generates a driving force. The front wheels 14 are main drive wheels that serve as drive wheels during both two-wheel drive travel (2WD travel) and four-wheel drive travel (4WD travel). The rear wheel 16 is a sub-drive wheel that becomes a driven wheel when traveling in 2WD and a drive wheel that transmits power from the engine 12 via the second power transmission path when traveling in 4WD. Accordingly, the vehicle 10 is an FF-based four-wheel drive vehicle.

  The first power transmission path includes a transmission 18, a front differential 20, left and right front wheel axles 22L and 22R (hereinafter referred to as front wheel axle 22 unless otherwise distinguished), and the like. The second power transmission path is connected to the transfer 24, the driven pinion 26, and the transfer 24, which are front and rear wheel power distribution devices that distribute a part of the power of the engine 12 transmitted to the transmission 18 and the front wheels 14 to the rear wheels 16. The propeller shaft 28, the drive pinion 30, the rear differential 32, and the left and right rear wheel axles 34L and 34R (hereinafter, particularly distinguished from each other) are transmitted to the rear wheels 16 during 4WD traveling. If not, the rear wheel axle 34 is provided).

  The transmission 18 is a part of a common power transmission path among the first power transmission path between the engine 12 and the front wheel 14 and the second power transmission path between the engine 12 and the rear wheel 16. The power of the engine 12 is transmitted to the front wheel 14 side and the rear wheel 16 side. The transmission 18 is a known planetary gear type multi-stage transmission in which a plurality of shift stages having different gear ratios (transmission ratios) γ (= transmission input rotation speed Nin / transmission output rotation speed Nout) are selectively established. An automatic transmission such as a known continuously variable transmission in which the gear ratio γ is continuously changed continuously or a known synchronous mesh type parallel twin-shaft transmission. A parking gear 18p is integrally connected to an output gear 18a that is an output rotating member of the transmission 18.

  The front differential 20 includes a differential case 20c and a differential mechanism 20d composed of a bevel gear, and is a known differential gear that transmits rotation while appropriately imparting differential rotation to the left and right front wheel axles 22L and 22R. is there. A ring gear 20r is formed in the differential case 20c. The ring gear 20r meshes with the output gear 18a of the transmission 18 via the gear mechanism 35. Therefore, the power output from the transmission 18 is input to the ring gear 20r.

  The transfer 24 is provided side by side with a front differential 20 as a rotating member that constitutes a part of the first power transmission path, and is connected to the front differential 20. The transfer 24 includes a first rotating member 36, a second rotating member 38, and a front side clutch 40.

  The first rotating member 36 has a substantially cylindrical shape, and the front wheel axle 22R passes through the inner peripheral side thereof. On one side of the first rotating member 36 in the axial direction, a fitting tooth that is fitted to a fitting tooth (not shown) formed on the differential case 20c of the front differential 20 is formed. It is integrally connected to the differential case 20c (in other words, it rotates integrally with the differential case 20c). A clutch tooth 42 that forms a part of the front side clutch 40 is formed on the other axial direction of the first rotating member 36.

  The second rotating member 38 has a substantially cylindrical shape, and the front wheel axle 22R passes through the inner peripheral side thereof. A ring gear 38r that meshes with the driven pinion 26 for transmitting the power of the engine 12 to the rear wheel 16 side is formed on one side of the second rotating member 38 in the axial direction. A clutch tooth 44 that forms part of the front clutch 40 is formed on the other axial direction of the second rotating member 38. The driven pinion 26 that meshes with the ring gear 38 r is connected to the propeller shaft 28, and further connected to the drive pinion 30 via the propeller shaft 28.

  The front side clutch 40 is a clutch that selectively connects / disconnects between a first rotating member 36 and a second rotating member 38 as opposing rotating members. The front side clutch 40 is a dog clutch (that is, a meshing clutch) including a clutch tooth 42, a clutch tooth 44, a sleeve 46, a holding member 48, and a front side actuator 50. The sleeve 46 has a substantially cylindrical shape. On the inner peripheral side of the sleeve 46, clutch teeth 42 and inner peripheral teeth 52 that can mesh with the clutch teeth 44 are formed. The sleeve 46 is moved in the axial direction by a front side actuator 50 that can be controlled electrically (electromagnetically), for example. The front clutch 40 may further include a synchronization mechanism (synchronization mechanism).

  FIG. 1 shows a state in which the front side clutch 40 is released. In this state, since the connection between the first rotating member 36 and the second rotating member 38 is cut off, the power of the engine 12 is not transmitted to the rear wheel 16. On the other hand, when the sleeve 46 is moved and the clutch teeth 42 and the clutch teeth 44 are engaged with the inner peripheral teeth 52, the front clutch 40 is engaged, and the first rotating member 36 and the second rotating member 38 are connected. The Therefore, when the first rotating member 36 rotates, the second rotating member 38, the driven pinion 26, the propeller shaft 28, and the drive pinion 30 are rotated. Thus, the front side clutch 40 disconnects the power transmission path between the front differential 20 and the propeller shaft 28 (in other words, the second power transmission path) provided on the engine 12 side of the propeller shaft 28. It is a connecting / disconnecting mechanism. That is, the front side clutch 40 is provided in the second power transmission path that transmits a part of the power of the engine 12 transmitted to the front wheels 14 via the transmission 18 to the rear wheels 16. This is a connection / disconnection mechanism for connecting / disconnecting the power transmission path.

  The rear differential 32 includes a differential case 32c and a differential mechanism 32d formed of a bevel gear, and is a known differential gear that transmits rotation while appropriately applying differential rotation to the left and right rear wheel axles 34L and 34R. is there. A ring gear 32r is formed in the differential case 32c, and the ring gear 32r meshes with the drive pinion 30. Therefore, the power of the engine 12 distributed by the transfer 24 is input to the ring gear 32 r via the propeller shaft 28 and transmitted to the rear wheel 16 via the rear differential 32.

  The vehicle 10 further includes a coupling 54 that is provided between the rear differential 32 and the left rear axle 34L and forms a part of the second power transmission path. The coupling 54 is a known electronically controlled coupling having, for example, a multi-plate clutch 54c and an electromagnetic solenoid (not shown) as a rear actuator, and transmits torque between the rear differential 32 and the left rear axle 34L. Do. The multi-plate clutch 54c is a wet friction clutch having a plurality of inner clutch plates 54ca and a plurality of outer clutch plates 54cb as opposed rotating members. In the coupling 54, for example, the driving force transmitted to the rear wheel 16 is controlled by controlling the engagement force of the multi-plate clutch 54c (in other words, the transmission torque of the coupling 54).

  Specifically, when the coupling 54 is engaged, the propeller shaft 28 and the left rear wheel axle 34L are connected via the rear differential 32 and the like so that torque can be transmitted, and the propeller shaft 28 and the right rear wheel axle 34R are connected. Are connected via a rear differential 32 or the like so that torque can be transmitted. On the other hand, when the coupling 54 is released, the torque from the propeller shaft 28 is not transmitted to the left rear axle 34L, and accordingly (ie, due to the general characteristic of the rear differential 32 as a differential gear) Torque from the propeller shaft 28 is not transmitted to the rear wheel axle 34R. In the coupling 54, when a current is supplied to the electromagnetic solenoid (not shown), the multi-plate clutch 54c is engaged with an engagement force proportional to the current value, and the rear wheel 16 increases as the transmission torque of the coupling 54 increases. The driving force transmitted to is increased. The coupling 54 can continuously change the torque distribution between the front wheel 14 and the rear wheel 16 between, for example, 100: 0 to 50:50 by controlling the transmission torque. As described above, the coupling 54 interrupts the power transmission path (in other words, the second power transmission path) between the propeller shaft 28 and the rear wheel 16 provided on the rear wheel 16 side of the propeller shaft 28. It is a connecting / disconnecting mechanism. Accordingly, the coupling 54 is provided in the second power transmission path for transmitting a part of the power of the engine 12 transmitted to the front wheels 14 via the transmission 18 to the rear wheels 16 like the front side clutch 40. It functions as one of the connecting / disconnecting mechanisms for connecting / disconnecting the second power transmission path. Since the coupling 54 is a clutch whose transmission torque can be controlled between release and engagement, the engagement force in the process of synchronizing the rotational speeds of the inner clutch plate 54ca and the outer clutch plate 54cb is controlled. The clutch to get.

  In the vehicle 10 configured as described above, for example, when the front side clutch 40 is engaged and the transmission torque of the coupling 54 is controlled to a value larger than zero, the rear wheel 16 is also connected to the coupling 54. A driving force corresponding to the transmission torque is transmitted. Accordingly, the power is transmitted to both the front wheels 14 and the rear wheels 16 to achieve 4WD travel. In the 4WD traveling, the torque distribution between the front wheel 14 and the rear wheel 16 is adjusted as necessary by controlling the transmission torque of the coupling 54.

  In the vehicle 10, for example, when the front side clutch 40 is released, the connection between the first rotating member 36 and the second rotating member 38 is cut off, so that power is not transmitted to the rear wheel 16. Therefore, it becomes 2WD driving | running which only the front wheel 14 drives. In addition, for example, when the coupling 54 corresponding to the rear side clutch is released, each rotating element (the second rotating member 38, the second rotating member 38, and the like) that constitutes a power transmission path from the second rotating member 38 to the differential case 32c during 2WD traveling. Rotation is not transmitted from the engine 12 side or the rear wheel 16 side to the driven pinion 26, the propeller shaft 28, the drive pinion 30, the differential case 32c, and the like. Therefore, during the 2WD traveling, each of these rotating elements stops rotating, the accompanying rotation of each rotating element is prevented, and the running resistance is reduced. The front side clutch 40 and the coupling 54 are disengaged during 2WD traveling to stop the rotation of a predetermined rotating element that transmits power to the rear wheel 16 during 4WD traveling. These are two connecting / disconnecting mechanisms respectively provided on the wheel 16 side. That is, the vehicle 10 includes the two connecting / disconnecting mechanisms as a disconnecting mechanism that stops the rotation of the predetermined rotating element when operated during 2WD traveling. The predetermined rotation element is a rotation element (that is, a second rotation member) sandwiched between the front side clutch 40 and the coupling 54 among the rotation elements constituting the power transmission path between the engine 12 and the rear wheel 16. 38 to each rotation element constituting a power transmission path from the differential case 32c to the differential case 32c. Further, in a driving state in which the front side clutch 40 and the coupling 54 are both released and the rotation elements stop rotating (that is, 2WD travel in which rotation is prevented), the disconnection in which the predetermined rotation element stops rotating is performed. State. The 2WD traveling in the disconnected state is referred to as 2WD_d traveling. In the 2WD_d travel, even if the coupling 54 is released, the predetermined rotating element may not be completely stopped by dragging the multi-plate clutch 54c. It is provided to stop the rotation of the predetermined rotating element (i.e., aiming to stop the rotation), and to stop the rotation of the predetermined rotating element results in the rotation of the predetermined rotating element. It also includes some situations that have occurred.

  Further, in the vehicle 10, when the coupling 54 is released while the front side clutch 40 is engaged, or when the coupling 54 is engaged while the front side clutch 40 is released, the rear wheel 16. No power is transmitted to Therefore, it becomes 2WD driving | running which only the front wheel 14 drives. In such 2WD traveling, each rotating element constituting the power transmission path from the second rotating member 38 to the differential case 32c is rotated. Therefore, the fuel consumption is reduced by the amount that the propeller shaft 28 and the like are rotated in the 2WD traveling mode. However, when switching from 2WD traveling to 4WD traveling, it is only necessary to connect the coupling 54, and quick switching is possible.

  The vehicle 10 is switched between 2WD traveling and 4WD traveling by controlling the connection / disconnection state of the front clutch 40 or the transmission torque of the coupling 54 according to the traveling state of the vehicle 10.

  Further, the vehicle 10 has a shift lever as an operator operated to a plurality of shift positions Psh, for example, a parking position “P”, a reverse travel position “R”, a neutral position “N”, and a forward travel position “D”. 56. The shift lever 56 switches the oil path of the hydraulic control circuit of the transmission 18 by moving a spool of a manual valve (not shown) via an interlocking mechanism such as a link or a cable. When the shift lever 56 is operated to the parking position “P”, the shift range of the transmission 18 is such that the power transmission path in the transmission 18 is cut off and the parking provided in the vehicle 10 as shown in FIG. To a parking range (hereinafter referred to as a P range) in which a parking lock that mechanically prevents rotation of the parking gear 18p (that is, the output gear 18a integrated with the parking gear 18p), and hence rotation of the front wheels 14, is executed by the mechanism 60. Can be switched. When the shift lever 56 is operated to the reverse travel position “R”, the shift range of the transmission 18 is such that the power transmission path in the transmission 18 can transmit power for moving the vehicle 10 backward. To the reverse travel range (hereinafter referred to as R range). When the shift lever 56 is operated to the neutral position “N”, the shift range of the transmission 18 is a neutral range (hereinafter referred to as a neutral range) for achieving a neutral state in which the power transmission path in the transmission 18 is interrupted. N range). When the shift lever 56 is operated to the forward travel position “D”, the shift range of the transmission 18 is such that the power transmission path in the transmission 18 can transmit power for moving the vehicle 10 forward. To the forward travel range (hereinafter referred to as D range). The D range and the R range are travel ranges for causing the vehicle 10 to travel, and the P range and the N range are non-travel ranges for preventing the vehicle 10 from traveling.

  In FIG. 2, the parking mechanism 60 includes a parking gear 18p, a lock pawl 62 that is engaged with the parking gear 18p and prevents rotation of the output gear 18a, a lock cam 64, and a support pin 66. . The lock pole 62 is rotated around the support pin 66 by the lock cam 64. The lock cam 64 is mechanically moved along the direction of arrow A along with the rotation of a shaft (not shown) that is rotated through an interlocking mechanism such as a link or a cable by operating the shift lever 56, for example. By operating the shift lever 56 to the parking position “P”, the lock cam 64 is pushed in the direction of the arrow A, and the lock pawl 62 is pushed up in the direction of the arrow B by the lock cam 64. When the lock pole 62 is pushed up to a position where it engages with the parking gear 18p, the rotation of the front wheel 14 that rotates in conjunction with the parking gear 18p is mechanically blocked, and the shift range of the transmission 18 is switched to the P range.

  In FIG. 1, the vehicle 10 is provided with an electronic control device 100 including a control device for the vehicle 10 that switches the operating state of the front side clutch 40 and the coupling 54 according to, for example, the traveling state of the vehicle 10. The electronic control device 100 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like, and the CPU uses a temporary storage function of the RAM according to a program stored in the ROM in advance. Various controls of the vehicle 10 are executed by performing signal processing. For example, the electronic control unit 100 executes output control of the engine 12, shift control of the transmission 18, switching control of the driving state of the vehicle 10, and the like. And driving state control. As shown in FIG. 1, the electronic control unit 100 includes various sensors (for example, various rotational speed sensors 70, 72, 74, 76, 78, an accelerator opening sensor 80, a throttle valve opening sensor 82) provided in the vehicle 10. , G sensor 84, yaw rate sensor 86, steering sensor 88, shift position sensor 90, various temperature sensors 92, 94, 96, 98, and the like, based on various actual values (for example, engine rotational speed Ne, transmission input rotational speed). Nin, transmission output rotational speed Nout, propeller shaft rotational speed Np, wheel speeds Nw corresponding to the wheel speeds Nwfl, Nwfr, Nwrl, Nwrr of the front wheels 14L, 14R and rear wheels 16L, 16R, accelerator opening θacc, throttle The valve opening degree θth, the longitudinal acceleration Gx of the vehicle 10, the lateral acceleration Gy of the vehicle 10, and the rotational angular velocity about the vertical axis of the vehicle 10 -Ryaw, steering angle θsw and steering direction of the steering wheel, shift position Psh which is the operation position of the shift lever 56, outside air temperature THair, cooling water temperature THeng corresponding to the temperature of the engine 12, hydraulic oil corresponding to the temperature of the transmission 18 The temperature THat, the clutch temperature THclt, which is the temperature of the coupling 54, etc.) are respectively supplied. As shown in FIG. 1, for example, an engine output control command signal Se for controlling the output of the engine 12, an operation command signal Sd for switching the state of the front side clutch 40, a coupling 54 (multiple An engagement force command signal Sc for controlling the engagement force of the plate clutch 54c) is an electromagnetic actuator (not shown) that drives the engine control device such as the fuel injection device, the ignition device, and the throttle actuator, the front side actuator 50, and the coupling 54. Output to solenoids, etc. The electronic control unit 100 calculates a speed V of the vehicle 10 (hereinafter referred to as a vehicle speed V) as one of various actual values based on each wheel speed Nw. The electronic control device 100 sets the average wheel speed of each wheel speed Nw as the vehicle speed V, for example.

  FIG. 3 is a functional block diagram for explaining a main part of the control function by the electronic control device 100. In FIG. 3, the electronic control unit 100 includes a drive state determination unit, that is, a drive state determination unit 102, a drive force calculation unit, that is, a drive force calculation unit 104, a clutch control unit, that is, a clutch control unit 106, and a shift control unit, that is, a shift control unit 108. It has.

  The driving state determination unit 102 determines the optimal driving state of the vehicle 10 based on information such as the various signals. Specifically, the driving state determination unit 102 has obtained and stored a driving force change of the vehicle 10 experimentally or in advance based on the accelerator opening θacc and the vehicle speed V (that is, predetermined). 2) When it is determined that the vehicle is in a steady running state smaller than the driving force change threshold, the vehicle 10 is driven in the disconnected state in which the front clutch 40 and the coupling 54 are both released. It is determined to be 2WD_d traveling which is traveling. On the other hand, when the driving state determination unit 102 determines that the driving force change exceeds the driving force change threshold value, the driving state of the vehicle 10 is determined based on the engagement of the front clutch 40 and the coupling 54. It is determined to be 4WD traveling that travels with engagement or slip engagement. The driving state determination unit 102 also determines predetermined turning determination threshold values θswth, Gyth for determining that the steering angle θsw, the left-right acceleration Gy, and the yaw rate Ryaw are absolute values, respectively. , Whether or not the vehicle 10 is turning is determined based on whether or not it is equal to or greater than Ryawth, and if it is determined that the vehicle 10 is not turning, the driving state of the vehicle 10 is set to 2WD_d traveling. Judgment is made. Further, the drive state determination unit 102 serves as a predetermined 4WD determination threshold for determining that it is better to set the drive state of the vehicle 10 to 4WD traveling between the wheels based on each wheel speed Nw. It is determined whether or not a predetermined wheel speed difference has occurred, and when it is determined that any of the rotational speed differences between the wheels has exceeded the predetermined wheel speed difference, the vehicle 10 is determined to be driven in 4WD. To do. Further, the drive state determination unit 102 determines a predetermined steering angle as a predetermined steering determination threshold value for determining that the steering wheel is steered by the driver so that the absolute value of the steering angle θsw turns the vehicle 10. It is determined whether or not the vehicle 10 is being steered based on whether or not it is greater than or equal to θswth2, and if it is determined that the vehicle 10 is being steered, it is calculated based on the vehicle speed V, the steering angle θsw, and the like. The target yaw rate Ryawtgt is compared with the actual yaw rate Ryaw to determine whether the vehicle behavior is in an understeer state or an oversteer state. Then, when it is determined that either the understeer state or the oversteer state has occurred, the driving state determination unit 102 determines that the driving state of the vehicle 10 is the 4WD traveling. As described above, the drive state determination unit 102 performs the 2WD travel during 2WD_d travel (hereinafter referred to as 2WD when the front side clutch 40 is engaged and the transmission torque of the coupling 54 is substantially zero unless otherwise distinguished). It functions as a four-wheel drive request determination means, that is, a four-wheel drive request determination unit that determines whether or not there is a request for switching to (including traveling).

  The driving force calculation unit 104 calculates the optimal front / rear wheel driving force distribution based on the information such as the various signals. Specifically, the driving force calculation unit 104 calculates an estimated value (estimated engine torque) Tep of the engine torque Te based on the engine rotational speed Ne, the throttle valve opening θth, etc., and the maximum acceleration performance is ensured. The driving force distribution of the front and rear wheels is calculated as follows. When the driving state determination unit 102 determines that the 2WD_d traveling is to be performed, the driving force calculation unit 104 sets the driving force distribution to the rear wheels 16 to zero. In addition, when the driving force calculation unit 104 determines that the operation state of the driver and the driving force change of the vehicle 10 are stable based on the throttle valve opening θth, the vehicle speed V, each wheel speed Nw, and the like. By reducing the driving force distribution to the rear wheels 16, the fuel consumption is improved in a situation close to front wheel driving. Further, the driving force calculation unit 104 reduces the distribution of driving force to the rear wheels 16 in order to prevent a tight braking phenomenon when turning at a low speed.

  The clutch control unit 106 switches the connection / disconnection state of the front clutch 40 so that the driving state determined by the driving state determination unit 102 and the front / rear wheel driving force distribution calculated by the driving force calculation unit 104 are obtained. Each command signal is output to an electromagnetic solenoid (not shown) that controls the transmission torque of the side actuator 50 and the coupling 54. Specifically, when it is determined by the drive state determination unit 102 that the 2WD_d travel is to be performed, the clutch control unit 106 releases a command to release the front clutch 40 and set the transmission torque of the coupling 54 to zero. Output to the front actuator 50 and the electromagnetic solenoid, respectively. When the driving state determination unit 102 determines that the 4WD traveling is to be performed, the clutch control unit 106 is configured to perform the 4WD traveling with the driving force distribution of the front and rear wheels calculated by the driving force calculation unit 104. A command to connect (engage) the clutch 40 and control the transmission torque of the coupling 54 is output to the front actuator 50 and the electromagnetic solenoid, respectively.

  In particular, when shifting from 2WD_d traveling to 4WD traveling, first, when releasing the disconnected state, the clutch control unit 106 outputs a command to the coupling 54 to generate a transmission torque to the electromagnetic solenoid, thereby The ring 54 is controlled toward engagement. In order to connect the front side clutch 40, the rotational speed of the propeller shaft 28, which is substantially stopped in rotation, is increased, and the rotating members (the first rotating member 36 and the second rotating member 38) in the front side clutch 40 are opposed to each other. This is for the purpose of synchronizing the rotation speeds. Thereafter, the clutch control unit 106 outputs a command to connect the front side clutch 40 to the front side actuator 50 when determining the synchronization of the rotational speeds of the opposing rotary members in the front side clutch 40. Then, the clutch control unit 106 outputs a command for causing the coupling 54 to generate transmission torque to the electromagnetic solenoid so that the front / rear wheel driving force distribution calculated by the driving force calculation unit 104 is obtained. A series of control procedures when shifting from 2WD_d traveling to 4WD traveling described above is a normal 4WD transition control procedure.

  For example, the clutch control unit 106 determines whether the propeller shaft rotation speed Np has reached a rotation speed that synchronizes the rotation speed of the opposite rotation member in the front side clutch 40 or not. It is determined whether or not the rotation speed is synchronized. The rotation speed to be synchronized is, for example, a synchronization determination threshold value N1 obtained by converting a synchronizable rotation speed obtained by subtracting the synchronizable maximum rotation speed difference ΔNsync from the rotation speed of the first rotation member 36 into a rotation speed on the propeller shaft 28. Further, the rotation speed of the first rotation member 36 may be a rotation speed directly detected by a rotation speed sensor (not shown), or may be a rotation speed converted from the transmission output rotation speed Nout. good. Further, the synchronizable maximum rotation speed difference ΔNsync is, for example, the difference in rotation speed between the rotation speed of the first rotation member 36 and the rotation speed of the second rotation member 38 that allows the front side clutch 40 to be connected (engaged). This is a synchronous permissible rotational speed difference that is predetermined as a maximum absolute value. Therefore, the clutch control unit 106 calculates the synchronization determination threshold value N1 based on the rotation speed of the first rotating member 36, and determines whether the front side clutch 40 is based on whether the propeller shaft rotation speed Np exceeds the synchronization determination threshold value N1. It is determined whether or not the rotational speeds of the opposing rotating members in the are synchronized.

  For example, the shift control unit 108 switches the shift range of the transmission 18 based on the shift position Psh of the shift lever 56. Specifically, when the transmission 18 is an automatic transmission in which a predetermined gear stage is formed by a combination of engagement and release of a plurality of engagement devices (hereinafter referred to as AT clutch 18c (see FIG. 1)). Will be described as an example.

  When the shift position Psh is the forward travel position “D”, the shift control unit 108 establishes the D range and executes automatic shift control. In this automatic shift control, the shift control unit 108 engages a predetermined AT clutch 18c as a predetermined engagement element for forming a predetermined forward travel gear based on a predetermined shift map. When the engagement of the predetermined AT clutch 18c is completed in accordance with the range switching to the D range of the transmission 18, a predetermined forward traveling gear stage is established. Further, when the shift position Psh is the reverse travel position “R”, the shift control unit 108 establishes the R range and engages a predetermined AT clutch 18c for forming a predetermined reverse travel gear stage. To do. When the engagement of the predetermined AT clutch 18c is completed along with the range switching to the R range of the transmission 18, a predetermined reverse gear stage is established. Further, when the shift position Psh is the parking position “P” or the neutral position “N”, the shift control unit 108 establishes the P range or the N range so that the power transmission path in the transmission 18 is interrupted. To switch the state of the AT clutch 18c. When the switching of the state of the AT clutch 18c is completed along with the range switching to the N range of the transmission 18, the power transmission path in the transmission 18 is interrupted. When the transmission 18 is switched to the P range, the power transmission path in the transmission 18 is interrupted, and when the lock pawl 62 is engaged with the parking gear 18p in the parking mechanism 60, the output gear 18a. Is prevented from rotating. In the transmission 18, the parking gear 18p and the lock pole 62 function as predetermined engagement elements. As described above, the transmission 18 is engaged with predetermined engagement elements according to a plurality of types of shift ranges.

  By the way, when the travel range of the transmission 18 is switched in the 4WD state, the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side. If the engine torque Te is large or the engine rotational speed Ne is high when the travel range is switched, a large torque may be input to the power transmission path on the rear wheel 16 side. Assuming that such a large torque is input to the power transmission path on the rear wheel 16 side, if the component parts of the power transmission path on the rear wheel 16 side have high strength, the size of the component parts may increase. There is a risk that the fuel consumption will deteriorate due to the increase in the weight of the components. From another viewpoint, when considering an FF-based four-wheel drive vehicle, the power transmission path on the rear wheel 16 side is auxiliary, so the hardware configuration of the power transmission path on the rear wheel 16 side becomes heavy. I want to avoid that. In this embodiment, from such a viewpoint, an embodiment is proposed in which the protection of the components of the power transmission path on the rear wheel 16 side is prioritized over the power performance (drivability). Note that the traveling range switching of the transmission 18 is switching from the non-traveling range (P, N range) to the traveling range (R, D range) (PorN → RorD range). Further, the traveling range switching of the transmission 18 includes switching between the D range and the R range (R → D range, D → R range). The N → RorD range, R → D range, and D → R range include both when the vehicle is stopped and when the vehicle is traveling.

  When the travel range of the transmission 18 is switched, the electronic control unit 100 releases the connection / disconnection mechanism or maintains the release / connection mechanism so that the vehicle 10 is in the 2WD state. After the engagement of the predetermined AT clutch 18c accompanying the switching is completed, the connecting / disconnecting mechanism is engaged as necessary to bring the vehicle 10 into the 4WD state. In this 2WD state, at least the front side clutch 40 has only to be released.

  Specifically, the electronic control device 100 further includes a traveling state determination unit, that is, a traveling state determination unit 110, and a standby instruction unit, that is, a standby instruction unit 112.

  For example, the traveling state determination unit 110 determines whether or not the transmission 18 is in one of the D, R, and N ranges and the vehicle speed V exceeds 0 [km / h]. The traveling state determination unit 110 determines whether or not a shift operation for switching the transmission 18 to the traveling range (hereinafter referred to as a traveling range switching operation) has been performed based on the shift position Psh, for example. Further, the traveling state determination unit 110 determines, for example, whether the vehicle 10 is in a 2WD state or a 4WD state.

  The clutch control unit 106 determines that the transmission 18 is in one of the D, R, and N ranges and the vehicle speed V exceeds 0 [km / h] by the traveling state determination unit 110, for example, When it is determined that the switching operation has been performed and it is determined that the vehicle 10 is in the 4WD state, switching control to 2WD (for example, control for releasing the front side clutch 40) is executed.

  For example, when the travel state determination unit 110 determines that the travel range switching operation has been performed, the standby command unit 112 is accompanied by the travel range switching of the transmission 18 according to the travel range switching operation, if necessary. An instruction (command) for waiting for control of the transmission 18 (ie, engagement control of a predetermined AT clutch 18c) is output to the shift control unit 108. The standby command unit 112 prohibits switching control to 4WD (for example, control for engaging the front side clutch 40) when the traveling state determination unit 110 determines that the vehicle 10 is in the 2WD state, for example. An instruction is output to the clutch control unit 106.

  The standby command unit 112 outputs the instruction prohibiting the switching control to 4WD, for example, or after the release of the front side clutch 40 by the clutch control unit 106 is completed, the standby command unit 112 replaces the instruction to wait for the travel range switching An instruction for permitting control of the transmission 18 associated with switching of the travel range of the transmission 18 according to the operation is output to the shift control unit 108. That is, the start of engagement of the predetermined AT clutch 18c accompanying the travel range switching by the shift control unit 108 is performed until an instruction to prohibit switching control to 4WD is output or until the release of the front clutch 40 is completed. , Made to wait. As a result, the power transmission path on the rear wheel 16 side is reliably cut off when the predetermined AT clutch 18c is engaged when the travel range of the transmission 18 is switched. It should be noted that instead of “until the release of the front side clutch 40 is completed”, “a predetermined time which is predetermined as a time for completing the release of the front side clutch 40 after the travel range switching operation (that is, after the travel range change) is completed. It may be “until time elapses”. Also, the instruction to prohibit the switching control to 4WD is released after the engagement of the predetermined AT clutch 18c accompanying the travel range switching by the shift control unit 108 is completed.

  FIG. 4 is a flowchart for explaining the control operation for suppressing the deterioration of the durability of the main parts of the control operation of the electronic control unit 100, that is, the components of the power transmission path on the rear wheel 16 side, for example, several msec to several tens. It is repeatedly executed with an extremely short cycle time of about msec. 5 and 6 are examples of time charts when the control operation shown in the flowchart of FIG. 4 is executed.

  In FIG. 4, first, in step S10 corresponding to the traveling state determination unit 110 (hereinafter, step is omitted), for example, the transmission 18 is set to one of the D, R, and N ranges, and the vehicle speed V is 0 [km. / h] is determined. If the determination at S10 is negative, this routine is terminated. If the determination in S10 is affirmative, it is determined in S20 corresponding to the traveling state determination unit 110 whether, for example, the traveling range of the transmission 18 has been switched according to the traveling range switching operation. If the determination at S20 is negative, this routine is terminated. If the determination in S20 is affirmative (see the time t2 in FIG. 5 and the time t1 in FIG. 6), in S30 corresponding to the standby command unit 112, for example, control of the transmission 18 accompanying the travel range switching (that is, a predetermined value) An instruction to wait for the engagement control of the AT clutch 18c) is output (see time t1 to time t3 in FIG. 6). Next, in S40 corresponding to the traveling state determination unit 110, for example, it is determined whether the vehicle 10 is in the 2WD state or the 4WD state. When it is determined in S40 that the state is the 2WD state, in S50 corresponding to the standby command unit 112, for example, an instruction to prohibit switching control to 4WD is output (see time t2 to time t3 in FIG. 5). On the other hand, if it is determined in S40 that the state is the 4WD state, in S60 corresponding to the clutch control unit 106, for example, the connecting / disconnecting mechanism is disconnected (released) and switched from 4WD to 2WD (t2 in FIG. 6). See time point). Subsequent to S50 or S60, in S70 corresponding to the standby command unit 112, for example, the instruction to wait for the control of the transmission 18 performed in S30 is canceled, and the transmission 18 is controlled in accordance with the travel range switching. Is output (see time t2 in FIG. 5 and time t3 in FIG. 6). Next, in S80 corresponding to the shift control unit 108, for example, engagement of the predetermined AT clutch 18c accompanying the travel range switching is completed. Next, in S90 corresponding to the drive state determination unit 102, for example, it is determined whether or not there is a request for switching to the 4WD state. If the determination in S90 is negative, this routine is terminated. If the determination in S90 is affirmative, in S100 corresponding to the clutch control unit 106, for example, the connection / disconnection mechanism is engaged and switched from 2WD to 4WD (see time t3 in FIG. 5 and time t4 in FIG. 6). .

  In FIG. 5, time t1 indicates that a request for switching to the 4WD state was made during 2WD travel. From the time t1, the propeller shaft 28 is raised toward the synchronous rotation speed of the front clutch 40 by the engagement of the coupling 54. The time t2 indicates that the predetermined AT clutch 18c is started to be engaged with the R → D range switching corresponding to the R → D shift operation (traveling range switching operation). In the comparative example, the front side clutch 40 is engaged after reaching the synchronous rotational speed. However, in the present embodiment, the switching to the 4WD state is prohibited along with the R → D range switching at time t2, so the front side clutch 40 is not engaged. Therefore, in the comparative example, as shown in the time t2 to the time t3, the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side, but in this embodiment, the torque at the time of range switching is on the rear wheel 16 side. Is not input to the power transmission path. In addition, in the comparative example, torque that is temporarily generated in association with 4WD switching (hereinafter referred to as 4WD switching torque) is also input to the power transmission path on the rear wheel 16 side so as to overlap the torque at the time of range switching. In this embodiment, after the engagement of the predetermined AT clutch 18c is completed, the prohibition of switching to the 4WD state is released and the switching to the 4WD state is performed, and only the torque at the time of 4WD switching is input to the power transmission path on the rear wheel 16 side alone. Is done.

  In FIG. 6, time t1 indicates that the R → D range is switched in accordance with the R → D shift operation during 4WD traveling. In the comparative example, the predetermined AT clutch 18c is started to be engaged with the R → D range switching at time t1. However, in this embodiment, the engagement control of the predetermined AT clutch 18c associated with the R → D range switching is made to wait, and is switched to the 2WD state at the time t2 during the standby, and predetermined at time t3 during the 2WD. The AT clutch 18c is started to be engaged. Therefore, in the comparative example, the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side as shown from the time t1 to the time t4, but in this embodiment, the torque at the time of range switching is on the rear wheel 16 side. Is not input to the power transmission path. In this embodiment, after the engagement of the predetermined AT clutch 18c is completed, the 4WD state is switched according to the switching request to the 4WD state, and only the 4WD switching torque is input to the power transmission path on the rear wheel 16 side alone. The

  Here, the flowchart shown in FIG. 4 may be executed when a large torque may be input to the power transmission path on the rear wheel 16 side. The case where a large torque may be input to the power transmission path on the rear wheel 16 side is, for example, when the engine torque Te is large. Further, when there is a possibility that a large torque may be input, for example, when the engine 12 is in the N, P range, the engine 12 is in an idling state (racing state). Therefore, the electronic control unit 100 changes the engine rotational speed Ne when the travel range of the transmission 18 is switched, and the engine rotational speed Ne at the start of engagement of the predetermined AT clutch 18c associated with the range switching of the transmission 18 and the shift. Any one of the rotational speed difference from the engine rotational speed Ne at the completion of engagement of the predetermined AT clutch 18c due to the range switching of the machine 18 and the required driving amount for the vehicle 10 by the driver is greater than or equal to each predetermined value. In some cases, the connection mechanism is released or the connection mechanism is released. The required drive amount is, for example, a required drive force [N], a required drive torque [Nm], a required drive power [W] or the like calculated by the electronic control device 100 based on the accelerator opening θacc or the vehicle speed V. Further, as the required drive amount, it is also possible to simply use the accelerator opening θacc [%], the throttle valve opening θth [%], the intake air amount [g / sec], or the like. The predetermined value is a predetermined determination threshold value for determining that a large torque may be input to the power transmission path on the rear wheel 16 side, for example.

  The flowchart shown in FIG. 4 may be executed when it is difficult to properly control the torque input to the power transmission path on the rear wheel 16 side by the coupling 54. The case where it is difficult to properly control the torque input to the power transmission path on the rear wheel 16 side by the coupling 54 is, for example, when the coupling 54 is cold when the viscosity of the hydraulic oil in the coupling 54 is increased. Therefore, the electronic control unit 100 releases the connection / disconnection mechanism when any one of the outside air temperature THair, the cooling water temperature THeng, the hydraulic oil temperature THat, and the clutch temperature THclt is equal to or less than the predetermined value. The release of the connection / disconnection mechanism is maintained. The predetermined value is a predetermined determination threshold for determining, for example, that it is difficult to appropriately control the torque input to the power transmission path on the rear wheel 16 side by the coupling 54.

  As described above, according to this embodiment, when the travel range of the transmission 18 is switched, the power transmission path on the rear wheel 16 side is cut off, so that the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side. Is avoided. Therefore, it is possible to suppress a decrease in durability of the components of the power transmission path on the rear wheel 16 side.

  Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  When the parking range switching (P range switching) of the transmission 18 during traveling is performed, the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side. For example, when the shift lever 56 is operated to the parking position “P” while the vehicle is running, the parking gear 18p is in a ratchet state at a vehicle speed V that exceeds the engagement vehicle speed Ve, and the parking gear 18p when the vehicle speed becomes lower than the engagement vehicle speed Ve. Is locked. Accordingly, when the engagement of the parking gear 18p and the lock pole 62 is completed in accordance with the P range switching while the vehicle is traveling, the parking gear 18p receives the traveling energy of the corresponding vehicle 10, and the rear wheel in the 4WD state. The torque at the time of range switching is also input to the 16th power transmission path. Therefore, even when the P range of the transmission 18 is switched during traveling, a large torque may be input to the power transmission path on the rear wheel 16 side, similarly to the switching of the transmission range of the transmission 18. The P range of the transmission 18 during traveling is switched from the N range to the P range during traveling (N → P range), or from the traveling range (R, D range) during traveling to the P range. (RorD → P range). The ratchet state refers to a state in which the lock pawl 62 is pushed up toward the parking gear 18p but cannot engage with the parking gear 18p and has not reached the locked state. The engagement vehicle speed Ve is, for example, a vehicle speed at which the parking gear 18p is locked from the ratchet state (that is, a vehicle speed at which the lock pawl 62 and the parking gear 18p can be engaged) at a predetermined engagement vehicle speed. is there.

  In the present embodiment, the traveling range switching of the transmission 18 in the control mode of the above-described embodiment is read as the P range switching of the transmission 18 during traveling. That is, when the P range of the transmission 18 is switched during traveling, the electronic control unit 100 releases the connection / disconnection mechanism or maintains the release / connection mechanism so that the vehicle 10 is in the 2WD state, and shifts the speed. After the engagement of the lock pole 62 and the parking gear 18p accompanying the P range switching of the machine 18 is completed, the connecting / disconnecting mechanism is engaged as necessary to bring the vehicle 10 into the 4WD state. In this embodiment, each range switching of the transmission 18 according to each range switching operation includes a shift-by-wire (SBW) system that switches the shift range of the transmission 18 by electric control, including switching control in the parking mechanism 60. Adopted.

  FIG. 7 is a flowchart for explaining a control operation for suppressing a deterioration in durability of a main part of the control operation of the electronic control unit 100, that is, a component of the power transmission path on the rear wheel 16 side. It is repeatedly executed with an extremely short cycle time of about msec.

  In FIG. 7, first, in the SB 10 corresponding to the traveling state determination unit 110, for example, whether the transmission 18 is in any of the D, R, and N ranges and whether the vehicle speed V exceeds 0 [km / h]. Is determined. If the determination at SB10 is negative, this routine is terminated. If the determination at SB10 is affirmative, it is determined at SB20 corresponding to the traveling state determination unit 110 whether, for example, a P range switching operation has been performed. If the determination at SB20 is negative, this routine is terminated. When the determination of SB20 is affirmed, in SB30 corresponding to the standby command unit 112, for example, an instruction to wait for control of the transmission 18 and the parking mechanism 60 accompanying the P range switching according to the P range switching operation is output. The Next, in SB 40 corresponding to the traveling state determination unit 110, for example, it is determined whether the vehicle 10 is in the 2WD state or the 4WD state. If it is determined in SB40 that the state is the 2WD state, an instruction for prohibiting switching control to 4WD, for example, is output in SB50 corresponding to the standby command unit 112. On the other hand, if it is determined in SB40 that the state is the 4WD state, for example, in the SB60 corresponding to the clutch control unit 106, the connection / disconnection mechanism is shut off (released) and switched from 4WD to 2WD. Subsequent to SB50 or SB60, at SB70 corresponding to the standby command unit 112, for example, the instruction to wait for the control of the transmission 18 and the parking mechanism 60 performed at SB30 is released, and the shift associated with the P range switching is performed. An instruction to permit control of the machine 18 and the parking mechanism 60 is output. Next, in SB 80 corresponding to the traveling state determination unit 110, for example, the vehicle speed V is set to 0 [km / h] with the completion of the engagement between the lock pole 62 and the parking gear 18p. Next, in SB90 corresponding to the drive state determination unit 102, for example, it is determined whether or not there is a request for switching to the 4WD state. If the determination at SB90 is negative, this routine is terminated. When the determination of SB90 is affirmed, in SB100 corresponding to the clutch control unit 106, for example, the connecting / disconnecting mechanism is engaged and switched from 2WD to 4WD.

  Here, the flowchart shown in FIG. 7 may be executed when a large torque may be input to the power transmission path on the rear wheel 16 side. The case where a large torque may be input to the power transmission path on the rear wheel 16 side is, for example, when the parking mechanism 60 is changed from the ratchet state to the locked state during traveling. Therefore, when the electronic control unit 100 switches the P range of the transmission 18 during traveling, the traveling vehicle speed V is equal to or lower than the engagement vehicle speed Ve or a predetermined vehicle speed that is higher than the engagement vehicle speed Ve by a predetermined value. In addition, the connection / disconnection mechanism is released or the connection / disconnection mechanism is kept released. The predetermined vehicle speed is a predetermined value obtained by adding a predetermined value that reflects a variation in the engagement vehicle speed Ve to the engagement vehicle speed Ve, for example.

  As described above, according to this embodiment, when the transmission 18 is switched to the P range, the power transmission path on the rear wheel 16 side is cut off, so that the torque at the time of range switching is input to the power transmission path on the rear wheel 16 side. Is avoided. Therefore, it is possible to suppress a decrease in durability of the components of the power transmission path on the rear wheel 16 side.

  As mentioned above, although the 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 embodiments, each embodiment is implemented independently. However, the above embodiments are not necessarily implemented independently, and may be implemented in combination as appropriate. For example, the electronic control unit 100 is configured to connect and disconnect the connecting / disconnecting mechanism (here, the front-side clutch 40 and the coupling) both when the traveling range of the transmission 18 is switched and when the P range of the transmission 18 is switched during traveling. At least one of 54) or the release of the connecting / disconnecting mechanism is maintained to bring the vehicle 10 into the 2WD state, and it is necessary after completion of engagement of a predetermined engagement element accompanying the range switching of the transmission 18. Accordingly, the connecting / disconnecting mechanism is engaged to bring the vehicle 10 into the 4WD state.

  Further, in the flowchart of FIG. 4 in the above-described embodiment, the D, R, and N ranges during traveling are affirmed in S10, but the present invention is not limited to such a mode. For example, the D, R, N range during traveling or the D, R, N, P range during stopping may be affirmed. If the D, R, N, and P ranges that are parked are affirmed in S10, it is also determined in S20 whether or not a travel range switching operation that results in the P → DorR range has been performed. As described above, in the flowcharts of FIGS. 4 and 7, the execution mode of each step and the like can be changed as appropriate without departing from the scope.

  In the above-described embodiment, the embodiment in which the present invention is implemented when the traveling vehicle speed V is equal to or lower than the engagement vehicle speed Ve or a predetermined vehicle speed higher than the engagement vehicle speed Ve by a predetermined value is exemplified. It is not restricted to this aspect. For example, it is considered that the torque at the time of switching the range when the transmission 18 is switched to the P range during traveling increases as the vehicle speed V increases. For this reason, in the vehicle speed range below the engagement vehicle speed Ve, the present invention is not implemented in the relatively low vehicle speed range, and the present invention is implemented in the relatively high vehicle speed range where the torque at the time of range switching becomes large. Is also possible.

  In the above-described embodiment, the coupling 54 is provided between the rear differential 32 and the left rear axle 34L, but this is not restrictive. For example, the coupling 54 is provided between the propeller shaft 28 and the drive pinion 30, or is provided between the ring gear 32r and the differential case 32c, or between the ring gear 32r and the left and right rear wheel axles 34L and 34R. One each may be provided. In the embodiment in which one coupling 54 is provided, the differential case 32c and the differential mechanism 32d are not necessarily required. Further, another connection / disconnection mechanism (for example, a dog clutch) may be provided as a disconnection mechanism between the ring gear 32r and the rear wheel axle 34. By the way, in the vehicle 10 that is not provided with another connecting / disconnecting mechanism (here, a dog clutch), the multi-plate clutch 54c is dragged even when the coupling 54 is released in 2WD_d traveling. There is a possibility that the rotating element (for example, the propeller shaft 28) cannot be completely stopped. The disconnect mechanism is preferably a mechanism that stops the rotation of a predetermined rotating element, but also includes a mechanism that causes some rotation due to dragging as described above. It should be noted that providing another connecting / disconnecting mechanism (here, a dog clutch) is useful in preventing rotation caused by such dragging.

  In the above-described embodiment, the coupling 54 is an electronically controlled coupling, but is not limited thereto. For example, the coupling 54 may be a dog clutch with a synchro mechanism. In the above-described embodiment, the front side clutch 40 may be provided with a synchronization mechanism. In this case, however, the front side clutch 40 is engaged from the point of time when the shift to the 4WD traveling is determined. You can start. Moreover, although the said connection / disconnection mechanism was the front side clutch 40 and the coupling 54, if the vehicle 10 is provided with at least one of the front side clutch 40 and the coupling 54 as the said connection / disconnection mechanism, The present invention can be applied.

  In the above-described embodiment, the front side clutch 40 is an electromagnetic dog clutch, but is not limited thereto. For example, the front side clutch 40 may be a dog clutch that includes a shift fork that moves the sleeve in the axial direction and that is driven by an electrically controllable or hydraulically controllable actuator. Moreover, although the front side clutch 40 was a dog clutch, it is not restricted to this. The front side clutch 40 can be appropriately applied as long as it is configured to connect and disconnect between the rotating elements.

  In the above-described embodiment, the vehicle 10 has a structure in which power is constantly transmitted to the front wheels 14 and the rear wheels 16 serve as auxiliary driving wheels, but the present invention is not limited thereto. For example, the vehicle 10 may have a structure in which power is constantly transmitted to the rear wheels 16 and the front wheels 14 are auxiliary driving wheels. For example, the vehicle 10 may be an FR-based four-wheel drive vehicle.

  In the above-described embodiment, the transmission 18 is exemplified by various automatic transmissions such as a planetary gear type multi-stage transmission, a continuously variable transmission, and a synchronous mesh parallel two-shaft transmission (including a known DCT). However, it is not limited to this mode. For example, the transmission 18 includes a differential mechanism coupled to the engine 12 and an electric motor coupled to the rotation element of the differential mechanism, which is different from the rotation element coupled to the engine 12. An electric continuously variable transmission or the like that can electrically change the gear ratio by controlling the electric motor may be used. Since this electric continuously variable transmission has a predetermined engagement element that is engaged when the P range is switched, at least the embodiment of the second embodiment can be applied.

  In the above-described embodiment, a gasoline engine or the like that is an internal combustion engine that generates power by combustion of fuel is illustrated as a driving force source. However, for example, another prime mover such as an electric motor is employed alone or in combination with the engine. You can also.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

10: Four-wheel drive vehicle 12: Engine (drive power source)
14 (14L, 14R): Front wheels (main drive wheels)
16 (16L, 16R): Rear wheel (sub drive wheel)
18: Transmission 18c: AT clutch (engagement element)
18p: Parking gear (engaging element)
40: Front clutch (connection / disconnection mechanism)
54: Coupling (connection / disconnection mechanism)
62: Lock pole (engagement element)
100: Electronic control device (control device)

Claims (1)

A transmission and disconnection mechanism for connecting and disconnecting the power transmission path, provided in a power transmission path for transmitting a part of the power of the driving force source transmitted to the main drive wheel via the transmission to the sub drive wheel. A four-wheel drive vehicle control device comprising:
When switching the transmission from the non-travel range to the travel range or switching between the forward travel range and the reverse travel range, release the connection mechanism or maintain the release mechanism, Engage the connecting / disconnecting mechanism as necessary after completing the engagement of the engaging element accompanying the range switching of the transmission,
When switching the transmission from the non-travel range to the travel range or switching between the forward travel range and the reverse travel range, the rotational speed of the driving force source and the range switching of the transmission are accompanied. The rotational speed difference between the rotational speed of the driving force source at the start of engagement of the engaging element and the rotational speed of the driving force source at the completion of engagement of the engaging element due to the range switching of the transmission, and A control device for a four-wheel drive vehicle, wherein when any of the requested drive amounts is equal to or greater than a predetermined value, the connection / disconnection mechanism is released or the release / connection mechanism is released.

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