JPH0460848B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a four-wheel drive system, and in particular, the present invention is capable of switching between a two-wheel drive state and a four-wheel drive state, and absorbs the rotational speed difference between front wheels and rear wheels in a four-wheel drive state. Regarding those equipped with a center day differential.

[Conventional technology]

In four-wheel drive vehicles, a so-called center differential (hereinafter referred to simply as a differential) is used to avoid braking during turns and to achieve neutral steering to improve steering performance. ) is provided. This center differential is functionally equivalent to a front differential or a rear differential, and first transmits the rotational output from the transmission to the differential case, and also has a pair of side gears that simultaneously mesh with a pinion that is rotatably supported by the trunnion shaft of this differential case. One of them (the differential side gear for front wheel drive) is connected to the front wheel drive system, and the other (the differential side gear for rear wheel drive) is connected to the rear wheel drive system. This center differential distributes driving force to the front wheels and rear wheels so that the rotation speed of the differential case becomes the average rotation speed of the front wheels and the average rotation speed of the rear wheels. the result,
While transmitting driving force from all wheels to the road surface, it is possible to absorb the difference in rotational speed between the front and rear wheels when turning, thereby avoiding braking phenomena. Furthermore, since driving force can be appropriately distributed to all wheels, steering performance can be dramatically improved, approaching neutral steering. Furthermore, recently, even though it is a four-wheel drive vehicle with a center differential as mentioned above, it can be put into four-wheel drive mode (hereinafter, four-wheel drive is simply referred to as four-wheel drive) when necessary.
Four-wheel drive vehicles have also been proposed that are configured to be able to selectively switch between a two-wheel drive state and a two-wheel drive state (hereinafter, two-wheel drive is simply referred to as two-wheel drive). For example, when switching between a 2WD state in which only the rear wheels are driven and a 4WD state in which all four wheels are driven, 2WD/4WD switching allows the front wheel drive differential side gear of the center differential to be connected to and removed from the front wheel drive system. In addition to the mechanism,
A center differential lock that switches between a differential function state (center differential free state) in which the differential case and the front wheel drive differential side gear can rotate relative to each other, and a center differential lock state that prevents relative rotation between the differential case and the front wheel drive differential side gear.・Free switching mechanism is added. In the 2WD state, the 2WD/4WD switching mechanism disconnects the front wheel drive differential side gear from the front wheel drive system, and the center differential lock/free switching mechanism selects the center differential state. In 4WD mode, the above 2WD/
The 4WD switching mechanism connects the front wheel drive differential side gear and the front wheel drive system, and the center differential lock/free switching mechanism selects the center differential free state. The reason why the center differential lock mechanism is added is that if the center differential is not locked, the front wheel drive differential side gear will become free in 2WD mode, and only this front wheel drive differential side gear will idle, resulting in the engine revving up. Because it will be. When the center differential lock mechanism is in the differential lock state, the pinion cannot rotate, so the differential case and the pair of side gears rotate together. In 2WD mode, the front wheel drive differential side gear is disconnected from the front wheel drive system, so the engine rotational output transmitted to the differential case is directly transmitted to the rear wheel drive system via the rear wheel drive subside gear. The Rukoto. In addition, in order to avoid the above-mentioned racing, when transitioning between 2WD and 4WD, the 2WD/4WD switching mechanism switches to 4WD, and the center differential lock mechanism switches to center differential. It is necessary to go through the state that it takes. In addition, the above-mentioned center differential lock mechanism forcibly connects the front wheel drive system and the rear wheel drive system directly by operating a switch when either the front or rear wheels are spinning while off-roading to avoid muddy conditions. It can be used when escaping. Furthermore, in a two-wheel drive state (for example, when only the rear wheels are driven), one side gear of the front differential is connected to one side gear of the front differential in order to prevent mechanical loss or vibration and noise caused by the driven rotation of the propeller shaft of the front wheel drive system. A freewheel clutch is interposed between the axle shaft and the axle shaft to be connected to the freewheel clutch, and this freewheel clutch is locked when the vehicle is in 4WD mode (axle lock state), and is in the free state when the vehicle is in 2WD mode. (axle free state). If this freewheel clutch is set to a free state in a two-wheel drive state, even if the side gear directly connected to the wheel rotates following the wheel,
The side gear on the freewheel side simply spins in the opposite direction and the differential case does not rotate. Therefore,
The front propeller shaft, which has a relatively large mass, is not rotated when in two-wheel drive mode, which reduces mechanical loss and avoids vibrations.

[Problems to be solved by the invention]

By the way, the above-mentioned freewheel clutch is normally operated in conjunction with the operation of the two-wheel drive/four-wheel drive switching mechanism, so its operation requires the following steps:
There is a slight delay in the operation of the two-wheel drive/four-wheel drive switching mechanism, and there is a concern that this may cause the engine to rev up. In other words, when switching from a 4WD state to a 2WD state, the 2WD/4WD switching mechanism first switches to the 2WD state, and even if the freewheel clutch becomes free after this, the front There is no problem because the transmission of driving force to the propeller shaft is cut off, but if the locking operation of the freewheel clutch is too delayed when switching from 2WD to 4WD, the drive to the front propeller shaft will be lost. Even when power is transmitted, a no-load condition occurs in which the side gear on the freewheel clutch side of the front differential simply spins, causing the engine to rev up. Once the engine revs up like this, the freewheel clutch will shift to a locked state while the side gear is idling at high speed, and when this clutch engages, impact torque will be applied to the drive system, which is undesirable. . This invention was devised under the above circumstances, and the axle is linked to a center differential, a 2WD/4WD switching mechanism, and either the front or rear axle that is driven in the 2WD state. To prevent engine revving when changing from 2WD to 4WD for 4WD vehicles equipped with a freewheel clutch that operates in conjunction with a 2WD/4WD switching mechanism between the differential and the differential. That is the issue.

[Means to solve the problem]

In order to solve the above problem, the present invention takes the following technical measures. That is, the four-wheel drive vehicle of the present invention includes a differential case to which the rotation of the output shaft of the transmission is transmitted, a pinion rotatably supported on the trunnion shaft of the differential case, and a pair of side gears that mesh with the pinion at the same time. a center differential provided therein; a constant drive system for one of the front wheels or rear wheels connected to a first side gear among the side gears; and a constant drive system for one of the front wheels or rear wheels connected to a second side gear among the side gears. Interposed between the other two-drive driven side drive system and the second side gear connected to the two-drive driven side drive system, and operates the two-wheel drive/four-wheel drive changeover switch. Accordingly, it is possible to switch between a two-drive state in which the second side gear and the two-drive driven drive system are cut off, and a four-drive state in which the second side gear and the two-drive driven drive system are connected. a two-wheel drive/four-wheel drive switching mechanism; a center differential lock state that is interlocked with the operation of the two-wheel drive/four-wheel drive switching mechanism and disables relative rotation of the differential case and the second side gear when in the two-wheel drive state; a center differential lock-free switching mechanism that operates to switch between a center differential free state and a center differential free state that allows the differential case and the second side gear to rotate relative to each other when in a drive state; It is interposed between one of the axle shafts, and is interlocked with the operation of the 2WD/4WD switching mechanism, and has an axle-free state that cuts off between the differential and the axle shaft when in the 2WD state, and an axle free state when in the 4WD state. a freewheel clutch that connects the differential and the axle shaft to switch between an axle lock state and a four-wheel drive vehicle, wherein the freewheel clutch detects that the freewheel clutch switches from the axle free state to the axle lock state. An axle lock detection switch is provided to detect the axle lock, and when changing from a two-wheel drive state to a four-wheel drive state, the center deflock/free switching mechanism is forced to remain in the center deflock state until an axle lock signal is received from the axle lock detection switch. It is configured by providing a compulsory maintenance means to maintain it.

[Effect]

When the two-wheel drive/four-wheel drive switching mechanism assumes the four-wheel drive state, the second side gear and the two-drive driven side drive system are connected, and the center differential lock-free mechanism selects the center differential free state. Therefore, the center differential functions, and the power from the transmission is distributed and transmitted from the first side gear to the constant drive system and from the second side gear to the driven side drive system during two-wheel drive. At this time, since the freewheel clutch locks the driven side drive system to the axle during two-drive mode, engine revving does not occur. When attempting to shift the 2WD/4WD switching mechanism from the 4WD state to the 2WD state, the center differential lock/free mechanism first selects the center differential lock state, then the second side gear and the 2WD state. The state shifts to a two-drive state in which the driven drive system is cut off.
Therefore, no racing occurs in the center differential during this switching. In conjunction with these operations, the freewheel clutch is switched to the axle free state. Therefore, in the two-wheel drive state, the propeller shaft on the driven side does not follow the wheels and idle. Note that before the freewheel clutch switches to the axle-free state, the two-wheel drive/four-wheel drive switching mechanism cuts off power transmission to the driven drive system, so engine revving does not occur. Here, a supplementary explanation of the meaning of operating the freewheel clutch in conjunction with the operation of the two-wheel drive/four-wheel drive switching mechanism is as follows. For example, if the freewheel clutch is operated in conjunction with the indoor 2WD/4WD changeover switch, the freewheel clutch can be operated in conjunction with the 2WD/4WD changeover switch, and the freewheel clutch can be operated in conjunction with the 2WD/4WD changeover switch. There is a concern that the wheel clutch may shift from the axle lock state to the axle free state first. If such concerns were to become a reality, the axle would become free while the driving force was being transmitted to the front propeller shaft on the driven side via the center differential during two-wheel drive, and the front differential would become unloaded. Engine revving will occur. To avoid this situation, the axle freewheel is basically
It operates in conjunction with the operation of the four-wheel drive switching mechanism. On the other hand, when attempting to shift the 2WD/4WD switching mechanism from the 2WD state to the 4WD state, the second side gear and the 2WD driven drive system are first connected, and then the center differential lock is connected. The freewheel clutch attempts to shift from the center differential lock state to the center differential free state, and the freewheel clutch switches from the axle free state to the axle lock state in conjunction with the operation of the two-wheel drive/four-wheel drive switching mechanism. In this case, the center differential lock state of the center differential lock/free switching mechanism is forcibly maintained by the forced maintaining means until an axle lock signal is received from an axle lock detection switch provided on the freewheel clutch. In other words, when transitioning from a 2WD state to a 4WD state, the transition of the center differential lock/free switching mechanism from the differential state to the differential free state is forcibly delayed until the freewheel clutch is completely in the axle lock state. It is. As a result, even though the freewheel clutch operates in conjunction with the 2WD/4WD switching mechanism, the center differential becomes free only after the freewheel clutch has completely switched to the axle lock state. The power transmitted to the driven side drive system during driving is transmitted to the wheels without any loss, so engine revving does not occur.

【effect】

As a result of the above, it is equipped with a center differential, a 2WD/4WD switching mechanism, and a freewheel clutch that avoids the driven rotation of the propeller shaft of the driven side drive system when in 2WD, and is also capable of changing from 2WD to 4WD. In both cases, when switching from 4WD to 2WD, the engine revs up due to the center differential, and due to the differential in the driven side drive system during 2WD. This achieves a four-wheel drive vehicle that secures a high degree of integrity of the drive power transmission system while reliably avoiding engine revving and reducing mechanical loss, vibration, and noise during driving to the utmost.

[Explanation of Examples]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows the overall configuration of the four-wheel drive vehicle of the present invention, and FIGS. 2 to 6 show the center differential 1,
2WD/4WD switching mechanism 2, center differential lock
Transfer 5 equipped with free switching mechanism 3
The specific configuration is shown below. Note that these figures show an example in which the rear wheels are driven during two-wheel drive, that is, the front wheel drive system becomes the driven side drive system during two-wheel drive. Therefore, in the following explanation, the rear wheel drive system 6 means the constant drive system mentioned in "Means for solving the problem", and the front wheel drive system 7 means the driven side in two-wheel drive. Refers to the drive system. In addition, each of these figures from FIG. 1 to FIG. A case is shown in which the wheel clutch 9 is in the axle lock state. The transfer 5 is attached to the engine 10 and the transmission 11 following them. Output shaft 1 that introduces the output of the transmission 11 into the transfer
2, a differential case 13 of the center differential 1 is supported so as not to be relatively rotatable. The interior of the differential case 13 includes a pinion 15 rotatably supported by a trunnion shaft 14, and a first side gear 16 and a second side gear 17 that mesh with the pinion 15 at the same time. The first side gear 16 is fixed to the front end of a rear wheel output shaft 18 which is coaxially and rotatably supported behind the output shaft 12, and the second side gear 17 is fixed to the outer periphery of this rear wheel output shaft 18. is supported for relative rotation. Then, a spline wheel 19 having the same outer diameter as the differential case 13 is integrally installed in the second side gear 17, and a spline 20 formed on the outer periphery of the rear end of the differential case 13 and the spline wheel 19 are connected to each other. In between, as shown in FIG. 1, there is a differential free position where only the splines 20 of the differential case are engaged, and a differential free position where the splines 20 of the differential case and the spline wheel 1 are engaged.
A free-lock switching sleeve 21 is provided which can reciprocate between differential lock positions in which it engages both of the differential locks 9. This switching sleeve 21 is an actuator 2 for operating a two-wheel drive/four-wheel drive switching mechanism 2, which will be described later.
Shift hawk 23 operated in conjunction with the movement of 2.
These components constitute the center differential/free switching mechanism 3. The spline wheel 1 on the rear wheel output shaft 18
Adjacent to the rear of 9, this spline wheel 1
A front wheel drive gear 25 integrally provided with a spline wheel 24 having the same diameter as the spline wheel 9 is supported for relative rotation. On the other hand, a front wheel output shaft 26 is rotatably supported on the side of the rear wheel output shaft 19 in parallel with the rear wheel output shaft 19, and a chain 28 is connected between an output gear 27 fixed to the rear wheel output shaft 26 and the front wheel drive gear 25. By rotating the front wheel drive gear 25, the front wheel output shaft 2 rotates.
6. In addition, the spline wheel 19 and the spline wheel 24
In between, as shown in FIGS. 1 and 3, there is a two-wheel drive mechanism that can reciprocate between a four-wheel drive position where it engages both spline wheels 19 and 24 and a two-wheel drive position where it engages only the spline wheel 19. A WD/4WD switching sleeve 29 is slidably fitted. The two-wheel drive/four-wheel drive switching sleeve 29 is driven by a shift fork 30 that is reciprocated by the actuator 22, thereby forming the two-wheel drive/four-wheel drive switching mechanism 2. The details of the interlocking mechanisms of the two-wheel drive/four-wheel drive switching mechanism 2 and the center differential/free switching mechanism 3 and their operations will be described later. The rear end of the rear wheel output shaft 18 is connected to a rear wheel 34 via a rear propeller shaft 31, a rear differential 32, and a rear axle 33. The front end of the front wheel output shaft 26 is connected to a front wheel 37 via a front propeller shaft 35, a front differential 8, and a front axle 36, and one axle is connected to one of the front differentials 8 at an intermediate portion thereof. The freewheel clutch mechanism 9 is separated into a portion 36a connected to a side gear and a portion 36b connected to a wheel 37, and a freewheel clutch mechanism 9 is interposed between these portions. This freewheel clutch mechanism 9 includes parts 36a, 3 of the axle.
A spline wheel 38, 3 of the same diameter is attached to the end of 6b.
9 is fixed thereto, and a switching sleeve 40 is fitted between them, which can reciprocate between an axle lock position where it engages with both of them and an axle free position where it engages only one of them.
The switching sleeve 40 is actuated by a switching fork 42 driven by an actuator 41. Next, details of the interlocking mechanism of the two-wheel drive/four-wheel drive switching mechanism 2 and the center differential lock/free mechanism 3 will be explained. As clearly shown in Figures 2 to 4,
A slide shaft 43 parallel to the rear wheel output shaft 18 is supported at an appropriate upper portion of the transfer housing. This slide shaft 43 is connected to the actuator 2
2 to reciprocate in the axial direction. In the middle of this slide shaft 43, there is a center defrotor whose movement will be described later via a rocking crank 44.
A linking fork 45 for transmitting transmission to the switching wheel 42 of the free switching mechanism 3 is integrally fixed, and is engaged with the arm portion 44a at one end of the swing crank 44. Therefore, this linking fork 45 moves integrally with the slide shaft 43 in its axial direction, and the swing crank 44 also directly responds to the movement of the slide shaft 43. Then, the connecting fork 45 on the slide shaft 43
The proximal end boss portion of the shift hawk 30 for the two-wheel drive/four-wheel drive switching sleeve described above is fitted onto the rear side of the shift fork 30 so as to be freely slidable in the axial direction. The shift hawk 30 also has a generally U-shaped plate member 46 in a plan view that is fitted to the slide shaft 43 so as to be relatively slidable at the rear portion of the shift hawk 30 and the front portion of the interconnection hawk 45. It is constantly urged forward by a compression coil spring 47 inserted into the front part of the body. That is, the shift hawk 30 is directly pushed when the slide shaft 43 slides backward, but is not directly pushed when the slide shaft 43 moves forward. . In addition, in the figure, when the shift fork 30 is located at the rear, it is in a four-wheel drive state, and when it is located at the front, it is in a two-wheel drive state. On the other hand, the base boss portion 30 of the shift hawk 30
As shown in FIG. 6, a locking lever 49 that extends forward is rotatably attached to the side surface of a through a pin 48, and this locking lever 49
is always biased in a direction overlapping the slide shaft 43 by hooking one end of the compression coil spring 47. And this locking lever 49
is dimensioned so that when the shift hawk 30 is at the rear part on the slide shaft 43, that is, in the 4WD position, the tip thereof will stick to the rear surface of the latching step 52 provided at the appropriate part of the transfer housing. has been done. Further, an inclined cam surface 50 is formed on one side of this latch lever 49, and this cam surface 5
0, a guide pin 51 protruding from the linking fork 45 is engaged with the linking fork 45. From the above,
When the slide shaft 43 or the connecting fork 45 moves forward, that is, in the two-wheel drive direction, the guide pin 51 pushes the cam surface 50 of the latch lever 49 and rotates the latch lever 49 in the direction of the arrow. 4
While the tip of the shift fork 9 is sticking to the rear surface of the latching step 52, the shift fork 30 is prevented from moving toward the second drive position. During this time, slide shaft 4
3 is still being moved in the two-drive direction by the action of the actuator 22, the compression coil spring 47 is being charged with energy. Only when the latch lever 49 is further rotated and the tension between its tip and the latch step 52 is released, is the shift hawk 30 allowed to move toward the second drive position. It is moved to the second drive position by the stored force of the compression coil spring 47. When the shift fork 30 is moving to the second drive position, the tip of the latch lever 49 is hooked on the latch step 52, as shown by the imaginary line in FIG. Contrary to the above, when the slide shaft 43 moves from the 2WD position to the 4WD position, the shift fork 30
is moved directly toward the 4WD position. At this time, the tip of the latching lever 49, whose tip had been hooked on the side wall of the latching step 52, is moved to the side wall of the latching step 52 by the biasing force of the spring 47, as shown in FIG.
2. Return to the position where it is against the rear wall and rotate. On the other hand, near the slide shaft 43 of the two-wheel drive/four-wheel drive switching mechanism 2, a support shaft 53 is fixed in parallel to the slide shaft 43 with the swing crank 44 in between. A base boss portion 23a of a shift hawk 23 for moving the switching sleeve 21 of the center differential lock free switching mechanism 3 described above is slidably fitted onto the support shaft 53. One end of the shift fork 23 is fixed to the rear end of the support shaft 53, and the front end is fixed to the boss portion 23.
A compression coil spring 55 is interposed between the tip of the U-shaped plate member 54 and the tip of the U-shaped plate member 54, which is arranged so as to insert the tip of the letter a, so that the spring 55 is always forward, that is,
It is biased toward the free position. Furthermore, a linking sleeve 56 is slidably fitted onto the support shaft 53 adjacent to the rear of the boss portion 23a of the shift fork 23. This linking sleeve 56 includes the above-mentioned swing crank 44.
The other end arm portion 44b is engaged, and therefore, the movement of the slide shaft 43 of the two-wheel drive/four-wheel drive switching mechanism first moves through the link sleeve 56 via the link fork 45 and the swing crank 44. This is transmitted to and activated. Then, this linking sleeve 5
6 is formed with an abutting portion 56a that can be hooked from the front to an engaging piece 57 that extends integrally from the shift fork 23, and this linking sleeve 56
When the shift hawk 23 in the front free position moves from the front to the rear, that is, from the free position to the lock position, the engagement between the contact portion 56a and the engagement piece 57 causes the shift hawk 23 in the front free position to be moved by the elasticity of the compression coil spring 55. It is designed so that it can be forcibly moved to the rear lock position against the force. As shown in FIG. 5, the base boss portion 23a of the shift fork 23 is further formed with a cylindrical portion 59 in which an engaging body 58 having a tapered tip 60 is housed. The protruding end portion is always urged by a spring 61 so as to be elastically pressed against the circumferential surface of the support shaft 53. Further, at least the above-mentioned engaging body 5 on the inner periphery of the base end boss portion 23a
The rear part from 8 is enlarged in diameter so that the front end part of the linking sleeve 56 can enter therein, and a cylindrical space is formed between it and the support shaft 53. On the other hand, a notch 62 is provided around the circumferential surface of the support shaft 53, into which the protruding end 60 of the engaging body 58 can engage when the shift fork 23 slides rearward, that is, to the lock position. Therefore, as described above, the shift fork 2 is slid to the rear lock position against the compression coil spring 55.
3 is held in the locked position by the protruding end 60 of the engaging body 58 automatically engaging the notch 62. Conversely, when the link sleeve 56 moves from the lock position to the free position, that is, from the rear to the front, its front end enters the enlarged diameter portion of the proximal boss portion of the shift fork 23 and engages the engagement body 58 and the notch. The shift fork 23 is held in the locked position until it is disengaged from the shift fork 62.
When the engagement body 58 and the notch 62 are disengaged in this way, the shift fork 23 is moved by the compression coil spring 5.
It tries to return to the free position by using the accumulated force of 5. The interaction between the two-wheel drive/four-wheel drive switching mechanism 2 and the center differential/free switching mechanism 3 up to this point can be briefly summarized as follows. Assume that the 2WD/4WD switching mechanism 2 is now in the 4WD state. At this time, the center differential lock/free switching mechanism 3 is in a free state. That is, the slide shaft 43 or the switching fork 42 is in the rear four-wheel drive position, and the shift fork 23 on the support shaft 53 is in the forward free position. When the actuator 22 operates and the slide shaft 43 moves toward the 2WD position, the linking fork 45, the swinging crank 44, or the linking sleeve 56 on the center differential/free switching mechanism side move directly in conjunction with the switching hawk 42. Since the latch lever 49 is stuck against the rear surface of the latch step 52, it does not move yet. On the other hand, the rocking crank 4
4, the link sleeve 56 on the center differential lock free mechanism side causes its abutting portion 56a to forcibly push the engagement piece 57 of the shift fork 23, thereby directly moving the shift fork 23 to the defrot position. It can be moved. Then, when the center differential 1 is locked, the locking lever 49, which is stuck to the rear surface of the locking step 52 on the two-wheel drive/four-wheel drive switching mechanism side, guides the slide shaft 43 as it moves. The tension relationship is released by the movement of the pin 51, and at this time, the switching fork 42 is slid to the forward two-wheel drive position by the stored force of the compression coil spring 47. Conversely, when the actuator 22 operates and the slide shaft 43 moves from the front two-wheel drive position to the rear four-wheel drive position, the switching fork 42 is directly pushed by the linking fork 45 and is moved in the four-wheel drive direction. At this time, the rocking crank 44 and the connecting sleeve 56 move in direct conjunction with each other, but as described above, the shift fork 23 on the center differential free switching mechanism side
remains in the defrock position due to the mutual engagement of engagement body 58 and notch 62. Then, when the connecting sleeve 56 further moves toward the free position and its front end forcibly releases the engagement between the engaging body 58 and the notch 62, the shift fork 23 is moved to the differential free position by the stored force of the compression coil spring 55. It will be done. In other words, when transitioning from a 4WD state to a 2WD state, or from a 2WD state to a 4WD state, the vehicle must go through a state in which it is in a 4WD state and the center differential is locked. Become. Now, in the present invention, the transfer 5, which is provided with the 2WD/4WD switching mechanism 2 and the center differential/free switching mechanism 3 that moves in conjunction with the 2WD/4WD switching mechanism 2, is further configured to switch from the 2WD state to the 4WD state. During the transition, the center differential free switching mechanism 3 is forced into the differential lock state until it receives a signal from the axle lock detection switch 63, which detects that the freewheel clutch 9 has switched from the axle free state to the axle lock state. Forced maintaining means 67 is provided to maintain the condition. In this example, a stopper wall 64 is integrally formed to extend from the proximal end boss portion 23a of the shift fork 23 in a direction perpendicular to the axis, and when the shift fork 23 is in the defrock position, the stopper wall 64 extends forward of the stopper wall 64. A locking rod 66 is provided at an appropriate part of the transfer case and can be moved back and forth between a locking position for preventing movement of the differential gear 23 to the differential free position and a non-locking position for retracting so as not to interfere with the movement locus of the stopper wall 64. This locking rod 66 extends and assumes the locked position when in the two-wheel drive state, and the axle lock detection switch 66 is activated.
The actuator 65 is configured to retract and assume an unlocked position when the axle lock condition is detected by the actuator 65.
It is designed to be operated by. Next, a transfer actuator 22 for operating the two-wheel drive/four-wheel drive switching mechanism 2, and
A description will be given of the freewheel actuator 41 for axle lock/free switching of the front wheel drive system 7, the lock rod actuator 65 for advancing and retracting the lock rod 66, and the pneumatic circuit unique to the present invention related thereto. do. In this example, the transfer actuator 22 and the freewheel actuator 4
1 is composed of a diaphragm-type double-acting actuator, and the lock rod actuator 65 is composed of a diaphragm-type single-acting actuator, which are driven by the negative pressure of the engine. As shown in FIG. 1, the transfer actuator 22 has a four-wheel drive on-off valve 68 and a two-wheel drive on-off valve 69, each of which is a 3-port, 2-position solenoid valve connected to the negative pressure of the engine. Operated by combination. The suction port of the 4WD on-off valve 68 is communicated with the 4WD side compartment 22a of the transfer actuator 22, and the suction port of the 2WD on/off valve 69 is communicated with the 2WD side compartment 22b of the transfer actuator 22.
is communicated with. In other words, 4WD side compartment 2
When negative pressure acts on 2a, the slide shaft 4
3 is moved to the four-wheel drive position side, and when negative pressure is applied to the two-wheel drive side compartment 22b, the slide shaft 43 is moved to the two-wheel drive position side. Also,
When the solenoid of the four-wheel drive on-off valve 68 is not energized, the suction port is opened to the atmosphere,
When the solenoid is energized, it switches so that negative pressure is applied to the suction port. On the contrary, the two-wheel drive on-off valve 68
When the solenoid is not energized, negative pressure is applied to the suction port, and when the solenoid is energized, the suction port is opened to the atmosphere. Moreover, the freewheel actuator 41 is
It is operated by a combination of the axle lock on-off valve 70, which is a 3-port, 2-position solenoid valve connected to the negative pressure of the engine, and the 4WD on-off valve 68. The suction port of the axle lock on-off valve 70 is
The suction port of the four-wheel drive on-off valve 68 is connected to the free side compartment 41a of the freewheel actuator 41.
The lock side compartment 41b is communicated with the lock side compartment 41b. That is, the ventilation pipe connected to the suction port of the 4WD on-off valve 68 branches into the 4WD side compartment 22a of the transfer actuator 22 and the lock side compartment 4 of the freewheel actuator 41.
1a. In this way, when negative pressure acts on the lock side compartment 41b, the switching sleeve 40 is moved to the axle lock side by this actuator, and the free side compartment 41a is moved.
When negative pressure is applied to the switching sleeve 40, the switching sleeve 40 is moved to the axle free side.
Further, in the axle lock on-off valve 70, negative pressure acts on the suction port when the solenoid is not energized, and when the solenoid is energized, the suction port is switched to open to the atmosphere. Furthermore, the rock rod actuator 65 is
It is operated by a differential opening/closing valve 71, which is a 3-port, 2-position solenoid valve connected to the negative pressure of the engine. The suction port of the differential lock valve 71 is communicated with the non-lock side compartment 65a of the lock lock actuator 65. Further, this actuator 65 is a single-acting type that is elastically biased by a spring 72 so that the diaphragm always moves from the locking side to the locking side, and when negative pressure acts on the non-locking side compartment 65a, this negative pressure is Thus, the locking rod 66 is moved to the non-locking side, while when the negative pressure is released, the locking rod 66 is moved to the locking side by the spring 72. The defrock opening/closing valve 71 is switched so that when the solenoid is energized, negative pressure is applied to the suction port, and when the solenoid is not energized, the suction port is opened to the atmosphere. The above four-wheel drive on-off valve 68 and two-wheel drive on-off valve 69
Both of the solenoids are connected to a line 73, and this line 73 is connected to a 4WD side contact 75 of a 2WD/4WD remote changeover switch 74 disposed, for example, in a console box. And line 7
A wire 76 branching from the middle part of 3 is connected to a 2WD side contact 78 of the 2WD/4WD remote changeover switch 74 via a diode 77 that passes current only in the branching direction. Note that the positive terminal of this changeover switch 74 is connected to a power source 79. Additionally, the diode 77 in line 76
The positive side terminal of a 2WD/4WD switching detection switch 80 arranged in the transfer 5 to detect that the 2WD/4WD switching mechanism 2 has been switched to the 4WD state is located between the 2WD and 4WD switching mechanism 2. The 4WD side negative contact 81 of this switch 80 is connected to the ground via the 4WD status display lamp 82. Further, the solenoid of the axle lock on-off valve 70 is connected to a line 83 between the four-wheel drive side negative contact 81 of the switch 80 and the indicator lamp 82. Further, the solenoid of the differential lock valve 71 is connected to a power source 79 via an axle lock detection switch 63 provided on the freewheel clutch to detect when the freewheel clutch 9 has switched to the axle lock state. ing. In addition, the above-mentioned two-wheel drive/four-wheel drive changeover detection switch 80
can be easily configured, for example, by a switch that is closed by the movement of the slide shaft 43 from the 2WD position to the 4WD position in the 2WD/4WD switching mechanism. Further, the axle lock detection switch 63 can also be simply constructed with a switch that is closed when the rod of the freewheel actuator 41 is moved to the axle lock side. Next, the operation of the four-wheel drive vehicle of this example having the above configuration will be explained. A: When the 2WD/4WD changeover switch 74 is turned on to the 4WD side In this state, as shown in FIG. Since they are turned on, the solenoids of the four-wheel drive on-off valve 68 and the two-wheel drive on-off valve 69 are energized. At this time, negative pressure acts on the former suction port 68, and the latter suction port 69 is open to atmospheric pressure. Therefore, negative pressure acts on the 4WD side compartment 22a of the transfer actuator 22, and the slide shaft 43 of the 2WD/4WD switching mechanism 2 is located at the rear, that is, at the 4WD position side. . Further, the center differential lock/free switching mechanism 3 is located at a differential free position depending on the position of the slide shaft 43 of the two-wheel drive/four-wheel drive switching mechanism 2. At the same time, slide shaft 4
3 is in the 4WD position, and the 2WD/
The four-wheel-drive changeover detection switch 80 has a negative contact on the four-wheel drive side, and the four-wheel drive status display lamp 82 is lit. Furthermore, since the current passing through the line 76 and the two-wheel drive/four-wheel drive changeover detection switch 80 to line 83 flows to the solenoid of the axle lock on-off valve 70, the suction port of the axle lock on-off valve 70 is open to the atmosphere. There is. Therefore, the suction port of this axle lock on-off valve 70 communicates with the axle free side compartment 41a, and the suction port of the four-wheel drive on/off valve 68 communicates with the axle lock side compartment 41a.
Freewheel actuator 4 communicated with b
1 has shifted to the axle lock side. At the same time, since the axle lock detection switch 63 is ON, the solenoid of the differential lock on-off valve 71 is also energized and negative pressure is applied to its suction port. is moved to the unlocked position. In this state, a four-wheel drive state appears in which the center differential 1 functions while the rotational difference between the front wheel drive system 6 and the rear wheel drive system 7 can be absorbed. B: When the 2WD/4WD changeover switch 74 is switched from the 4WD side to the 2WD side When the 2WD/4WD changeover switch 74 is switched from the 4WD side negative contact 75 to the 2WD side negative contact 78, First, power to the solenoids of the four-wheel drive on-off valve 68 and the two-wheel drive on-off valve 69 is cut off. Then, the suction port of the four-wheel drive on-off valve 68 is opened to the atmosphere, and negative pressure acts on the suction port of the two-wheel drive on-off valve 69, so the transfer actuator 2
Negative pressure acts on the second two-wheel drive side compartment 22b, and the slide shaft 43 is moved forward, that is, to the two-wheel drive side. At the moment when the 2WD/4WD changeover switch 74 is switched to the 2WD side negative contact 75, the slide shaft 43 is still in the 4WD position, and therefore the 2WD/4WD detection switch 80 is on the 4WD side. Since the contact 81 remains connected, the current from the two-wheel drive side negative contact 78 of the changeover switch 74 remains energized to the solenoid of the axle lock on-off valve 70 via the wire 76 and the wire 83. At this time, each compartment of the freewheel actuator 41 is opened to the atmosphere, but the switching hawk 42 of the freewheel clutch 9 is held in the locked position by a holding mechanism such as a detent mechanism. Next, the slide shaft 43 actually slides to the 2WD position and the 2WD/4WD detection switch 80 is activated.
When the solenoid is opened, power to the solenoid of the axle locking on-off valve 70 is also cut off, and negative pressure acts on its suction port. At this point, a negative pressure is applied to the free side chamber 41a of the freewheel actuator 41, and the freewheel clutch 9 is switched to the axle free state. In conjunction with this switching operation, the axle lock detection switch 63 is opened, the energization to the solenoid of the differential lock valve 71 is also cut off, and the negative pressure to the non-lock side compartment 65a of the lock lock actuator 65 is released. Then, the locking rod 66 is moved toward the locking side by the elasticity of the spring 72 within the actuator 65. At this time, the shift fork 23 of the center differential lock/free switching mechanism 3 has already moved to the differential position, that is, to the rear in FIG. is shift hawk 23
Therefore, the shift fork 23 cannot move to the differential free position until the locking rod 66 is retracted to the unlocked position. The 2WD/4WD switching mechanism 2 and the center differential lock free mechanism 3 in the transfer are linked, and the 2WD/4WD switching mechanism 2 changes from the 4WD/center differential free state to the 4WD/center differential free state via the 4WD/center differential lock state. - As mentioned above, the center differential lock state is entered and the racing at the center differential is avoided. C: When the 2WD/4WD selector switch 74 is switched from the 2WD side to the 4WD side When the 2WD/4WD selector switch 74 is switched from the 2WD side to the 4WD side, first, the 4WD switch is opened/closed. valve 68
The solenoid of the two-wheel drive on-off valve 69 is energized, and the four-wheel drive side compartment 22 of the transfer actuator 22 is energized.
Negative pressure acts only on the slide shaft 43
moves to the rear 4WD position. At this moment, the two-wheel drive/four-wheel drive detection switch 80 and the axle lock detection switch 63 are still open, and the solenoids of the axle lock on-off valve 70 and the differential lock on-off valve 71 are still de-energized. At this time, since negative pressure acts on the suction port of the four-wheel drive on-off valve 68, negative pressure acts on both of the compartments of the freewheel actuator 41, but due to a holding mechanism such as a detent mechanism, The switching sleeve 40 of the freewheel clutch remains in the axle free position. Then, when the slide shaft 43 is completely moved to the 4WD side, the 2WD/4WD changeover detection switch 80 is closed, and the current passing through the diode 77 is transferred through the 4WD side contact 87 of the switch 80. It flows from the power line 83 to the solenoid of the axle lock on-off valve 70. As a result, the suction port of the axle lock opening/closing valve 70 is opened to the atmosphere, and negative pressure acts only on the axle lock side compartment 41b of the freewheel actuator 41, and the freewheel clutch 9 is forced into the axle lock. can be switched to the position. In the transfer shaft 5, when the slide shaft 43 is completely moved from the 2WD position to the 4WD position, the shift fork 23 of the center differential lock/free switching mechanism 3 is already shifted from the differential lock position to the differential free position by the force of the compression coil spring 55. As mentioned above, the locking lock 66 of the forced holding means 67
is extended to the lock position and shift hawk 23
In other words, the center differential-free switching mechanism is forcibly maintained in the differential-free position. Then, when the freewheel clutch 9 is actually switched to the axle lock position, the axle lock detection switch 63 is closed, and as a result, the solenoid of the differential lock on/off valve 71 is energized, and the lock door is closed from its suction port. Negative pressure acts on the non-lock side compartment 65a of the cutter 65,
Only after the lock rod 66 is retracted, the shift fork 23 is allowed to move to the differential free position due to the elasticity of the coil spring 55. As described above, according to the present invention, when the 2WD state shifts to the 4WD state, the freewheel operates in conjunction with the 2WD/4WD switching mechanism 2 switching from the 2WD state to the 4WD state. Since the clutch 9 maintains the center differential state of the center differential/free switching mechanism until the clutch 9 completely transitions from the axle free state to the axle locked state, the front differential when switching from 2WD state to 4WD state is This makes it possible to completely avoid the no-load condition and the resulting engine revving. Of course, the scope of the invention is not limited to the embodiments described above. The type of each actuator or the configuration of the pneumatic circuit for operating the actuator can be modified in various ways in addition to the embodiments. Moreover, although the embodiment is an example in which the rear wheels are driven all the time and the front wheels are driven part-time, it is also possible to drive the front wheels all the time and drive the rear wheels part-time. In this case, a design change may be made in which the rear wheel output shaft of the embodiment is connected to the front wheels, and the front wheel output shaft is connected to the rear wheels.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of a four-wheel drive vehicle according to the present invention, FIG. 2 is a cross-sectional view of the transfer of the above-mentioned embodiment as seen from the rear, and FIG. 3 is a cross-sectional view taken along the line -- in FIG. 4 is a view in the direction of the arrows in FIG. 2, FIG. 5 is an enlarged sectional view taken along the line -- in FIG. 2, and FIG. 6 is an enlarged view in the direction of the arrows in FIG. 1...Center differential, 2...2WD/4WD switching mechanism, 3...Center differential/free switching mechanism, 5...Transfer, 6
...Continuous drive system (rear wheel drive system), 7...Driver side drive system during 2nd drive (front wheel drive system), 8...Differential (of the driven side drive system during 2nd drive), 9...Free Wheel clutch, 10...Engine, 11...
Transmission, 12... Output shaft, 13... Differential case, 14... Trunnion shaft, 15...
Pinion, 16...First side gear, 17...
Second side gear, 36...Axle, 63...
Axle lock detection switch, 67...forced maintenance means.

Claims (1)

[Scope of Claims] 1. A differential case to which the rotation of the output shaft of the transmission is transmitted, a pinion rotatably supported on the trunnion shaft of the differential case, and a pinion that meshes with the pinion at the same time. a center differential including a pair of side gears; a constant drive system for one of the front wheels or rear wheels that is connected to the first side gear of the side gears; and a constant drive system of one of the front wheels or the rear wheels that is connected to the second side gear of the side gears. The two-wheel drive driven side drive system is interposed between the other one of the front wheels or rear wheels that is driven by the two-wheel drive system, and the second side gear that is connected to the two-wheel drive driven side drive system and the second side gear connected thereto. By operating a wheel drive changeover switch, a two-wheel drive state in which the second side gear and the driven side drive system during two-wheel drive are cut off, and a two-wheel drive state in which the second side gear and the driven side drive system during two-wheel drive are connected are connected. Two-wheel drive mode that can switch between four-wheel drive mode and
a four-wheel drive switching mechanism, and a center differential lock state that is interlocked with the operation of the two-wheel drive/four-wheel drive switching mechanism and disables relative rotation between the differential case and the second side gear when in a two-wheel drive state; A center differential lock that switches between a center differential free state and a center differential free state that allows the differential case and the second side gear to rotate relative to each other when in a four-wheel drive state.
The free switching mechanism is interposed between the differential of the driven side drive system during two-wheel drive and one of the axle shafts extending from this, and is interlocked with the operation of the two-wheel drive/four-wheel drive switching mechanism, a freewheel clutch that switches between an axle free state that disconnects the differential and the axle shaft when the vehicle is in a four-wheel drive state and an axle lock state that connects the differential and the axle shaft when the vehicle is in a four-wheel drive state; The four-wheel drive vehicle is equipped with an axle lock detection switch that detects when the freewheel clutch switches from the axle free state to the axle lock state, and when the freewheel clutch shifts from the two-wheel drive state to the four-wheel drive state, A four-wheel drive vehicle, characterized in that a four-wheel drive vehicle is provided with forced maintenance means for forcibly maintaining the center differential lock state of the center differential lock/free switching mechanism until receiving an axle lock signal from the axle lock detection switch.