JPH1199844A - Power transmission switching device of four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of impact noise in a part time 4WD system even when the 2WD is switched from the 4WD during the steering operation. SOLUTION: In a power transmission switching device, an air piping 7 for switching the 4WD and an air piping 8 for switching the 2WD are connected to a vacuum pressure source through solenoid valves 9, 10 on the forward side and the rear side of a diaphragm 1 of an air-type actuator 2, and an orifice 12 is provided between the solenoid valve 10 of the air piping 8 for switching the 2WD and the vacuum pressure source. When the switching is achieved from the 4WD to the 2WD, the gear disengagement to the 2WD side during the rapid steering of a vehicle is avoided by generating the time lag in the operation of an actuator 2, and the impact noise caused by excessive disengagement of the gear can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission switching device for four-wheel drive and two-wheel drive of a four-wheel drive vehicle, and more particularly to a power transmission switch for selectively switching between four-wheel drive and two-wheel drive by a driver. It concerns the device.

[0002]

2. Description of the Related Art In a four-wheel drive vehicle, a driver can select a four-wheel drive (hereinafter, referred to as 4WD) or a two-wheel drive (hereinafter, referred to as 2WD) depending on a running state.
WD) is switched by a lever or a switch, and a full-time 4WD system in which drive torque is automatically distributed to the front and rear wheels in accordance with a difference in rotation speed between the front and rear wheels.

One of the important problems related to 4WD is that when turning on a road surface having a high coefficient of friction with a tire such as a pavement road, a brake is applied due to torque circulation due to a difference in rotation speed between front and rear wheels. There is a corner braking phenomenon.

[0004] In the part-time 4WD system, 4 W
It is common to switch between D and 2WD,
When entering a turning road during 4WD driving, the vehicle is switched to 2WD in advance in order to avoid the tight corner braking phenomenon.

[0005]

When the driver enters the turning road during the 4WD driving described above, the driver sometimes forgets to switch from 4WD to 2WD in advance, and performs the operation of switching to 2WD during turning.

During turning in 4WD, since the above-described torque circulation occurs, a large force acts on the gear of the power transmission switching device, and in this state, the rotation transmitting power to one of the propulsion shafts is performed. If the gears of the members are cut off to bring them into the 2WD state, there is a problem that the impact sound of the cutout is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power transmission switching device for a four-wheel drive vehicle in which a part-time 4WD system does not generate an impact sound even when switching from 4WD to 2WD during turning. .

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a first rotation in which the rotation of an output shaft of a transmission is constantly transmitted and power is transmitted to one of the propulsion shafts of the front and rear wheels. A member, a second rotating member disposed coaxially with the first rotating member and transmitting power to the other propulsion shaft of the front and rear wheels, and by moving forward and backward in the axial direction of the two rotating members, A sliding member for connecting and disconnecting the two rotating members, wherein the sliding member is connected to an actuator in a power transmission switching device of a four-wheel drive vehicle, wherein the sliding member disconnects the two rotating members. Further, a configuration is provided in which means for causing a time delay in the operation of the actuator is provided.

That is, the driver notices that he has forgotten to switch from 4WD to 2WD, and often operates the levers and switches of the power transmission switching device during a sharp turn. This operation switches the power transmission switching device to 2WD. In most cases, the vehicle has already passed through a sharp turning section and is now entering a gentle turning section or straight road, so the actuator of the power transmission switching device operates with a delay only when switching from 4WD to 2WD 2WD during a sharp turn of the car
This prevented the generation of impact noise due to the release of the gear to the side.

As the actuator, an actuator which operates by air pressure via an electromagnetic valve can be adopted.

As means for causing a time delay in the operation of the actuator, the actuator is connected to a source of air pressure via an electromagnetic valve through two pipes for connecting the slide member and for shutting off the slide member. A method of providing a flow resistor between the solenoid valve of the pipe and the source of the air pressure or between the solenoid valve of the connection pipe and the open end of the atmosphere can be adopted.

That is, by providing a flow resistor such as an orifice between the solenoid valve of the shutoff pipe and the air pressure source or between the solenoid valve of the connection pipe and the open end of the atmosphere, the actuator is mounted. Since the flow rate of the operating air is reduced and the operating force is reduced, the slide member moves, causing a time delay in the operation of disconnecting the gear of the rotating member that transmits power to one propulsion shaft. it can. The operating force is small only in the initial stage when the flow of air is unsteady, and the operating force gradually increases, so that the gear can be reliably released.
A nozzle or a venturi tube may be used as the flow resistor.

When switching from 2WD to 4WD, there is no air flow in the flow resistor, so that the operating speed of the actuator does not change.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall view of a power transmission switching device according to a first embodiment, and FIGS. 2 and 3 are enlarged views of an actuator portion and a transfer portion of the power transmission switching device, respectively.

The power transmission switching device includes a diaphragm 1
The rod 3 attached to the front surface of the diaphragm 1 is connected to the rod 6 which engages with the slide gear 5 in the transfer by the push-pull wire 4 using the pneumatic actuator 2 in which is incorporated.

On the front side and the rear side of the diaphragm 1, air pipes 7 for switching 4WD, 2WD
A switching air pipe 8 is connected. Solenoid valves 9 and 10 are attached to each of the air pipes 7 and 8, and they are joined on the way and connected to a negative pressure source (not shown) of an engine manifold via an accumulator 11 for accumulating negative pressure. ing. An orifice 12 as a flow resistor is attached to the 2WD switching air pipe 8 between the junction of the solenoid valve 10 and the air pipe 7.

Each of the solenoid valves 9 and 10 is a three-way valve, and each of the solenoid valves 9 and 10 is closed so that one side communicates with the atmosphere. FIG. 2 shows the actuator 2
Is operated on the 2WD side. The solenoid valve 10 of the 2WD switching pipe 8 is opened, the solenoid valve 9 of the 4WD switching pipe 7 is closed, the air on the rear side of the diaphragm 1 is sucked by the negative pressure source, and the air is discharged on the front side by the electromagnetic valve. 9, the diaphragm 1 is moving to the rear side. During the operation on the 2WD side, when the solenoid valve 10 is opened, the flow of air to the negative pressure source receives the resistance of the orifice 12, so that the movement of the diaphragm 1 is delayed.

Inside the transfer, a hollow rotating shaft 13 for transmitting the output of the transmission and a rotating shaft 14 directly connected to the propulsion shaft of the rear wheel are coaxially arranged. The rotary shaft 14 has a key 15
And a second rotating member 18 rotatable by a needle roller bearing 17. Gears 19 and 20 are formed on the outer peripheral surfaces of these rotating members 16 and 18, respectively.
It is possible to mesh with.

A sprocket 21 is also formed on the outer peripheral surface of the second rotating member 18. This sprocket 21
, A silent chain 22 is wound therearound to transmit power to a rotating shaft 23 connected to a propulsion shaft of a front wheel.

FIG. 3 shows a state in which the transfer is switched to the 2WD side by the operation of the actuator 2 shown in FIG. With the movement of the diaphragm 1, the rod 3
And the rod 6 connected to the diaphragm 1 via the push-pull wire 4 moves to the left, engages with the fork 24 attached to the rod 6, and the slide gear 5 retreats to the left. The engagement of the second rotating member 18 with the gear 20 is released.

A sub-transmission is also incorporated inside the transfer. This auxiliary transmission switches a transmission path from a rotating shaft 13 for transmitting the output of the transmission to a rotating shaft 14 directly connected to a propulsion shaft of the rear wheel by a gear mechanism. High gears 25a, 25b formed on the outer peripheral surface, low gears 26a, 26b and neutral gear 27 attached to the rotating shaft 14, and respective gears 25a, 26a, 27
A slide gear 28 that can mesh with the rotary shaft 13;
It comprises a gear 30 mounted on a shaft 29 parallel to 14.

The low gears 26a and 26b and the gear 30
Are rotatably formed by needle roller bearings 31 and 32, respectively, and the neutral gear 27 is fixed to the rotating shaft 14 for rotation. The slide gear 28 can be slid in the axial direction of the rotating shaft 14 by a rod 33 with a fork connected to another actuator (not shown).

FIG. 3 shows a state in which the auxiliary transmission is set to the high position, and the slide gear 28 is engaged with the high gear 25a and the neutral gear 27. That is, the rotating torque of the rotating shaft 13 is
a, the slide gear 28 and the neutral gear 27 in this order, and are transmitted to the rotating shaft 14. In the case of the low position, the slide gear 28 is
a meshes with the neutral gear 27 and the rotation shaft 13
Is transmitted to the rotary shaft 14 via the high gear 25b, the gear 30, the low gears 26b and 26a, the slide gear 28, and the neutral gear 27.

FIG. 4 and FIG.
The actuator part and the transfer part in the state switched to WD are shown in an enlarged manner. Actuator part is 4W
The solenoid valve 9 of the D switching pipe 7 is opened, the solenoid valve 10 of the 2WD switching pipe 8 is closed, the air on the front side of the diaphragm 1 is sucked by the negative pressure source, and the air is discharged on the rear side by the solenoid valve. 10, the diaphragm 1 has moved to the front side. In this case, the orifice 1
Since no air flows in the portion 2, the time delay as described above does not occur.

The transfer section includes the diaphragm 1
With this movement, the slide gear 5 is engaged with the fork 24 of the rod 6 and moves forward to the right, meshing with the gear 20 of the second rotating member 18. Therefore, in this case, power is also transmitted to the rotating shaft 23 connected to the propulsion shaft of the front wheels via the silent chain 22.

The slide gear 5 and the second rotating member 18
As shown in FIG. 6, a synchro mechanism is provided between the gears 20 for smooth engagement of the two gears. The synchronizing mechanism includes a synchronizer key 34.
And a ring-shaped center cone 35, and two rings 36, 3 arranged on both inner and outer sides of the center cone 35.
The synchronizer key 34 is moved rightward as the slide gear 5 advances rightward, and the second rotation is performed using the frictional force between the three rings 35, 36, and 37. The rotation is transmitted to the member 18, and the slide gear 5
Before the rotation member 18 meshes with the gear 20, the rotation of both members is synchronized.

FIG. 7 shows a second embodiment. In this power transmission switching device, the transfer unit is exactly the same as that of the first embodiment, and the installation location of the orifice 12 of the actuator unit is different from that of the first embodiment. In this case, the orifice 12 is mounted between the solenoid valve 9 of the 4WD switching pipe 7 and the open end of the atmosphere.

FIG. 7 shows a state in which the actuator 2 is operated to the 2WD side similarly to FIG. 1, and the solenoid valve 10 of the 2WD switching pipe 8 is opened and the solenoid valve 9 of the 4WD switching pipe 7 is closed. Then, the air on the rear side of the diaphragm 1 is sucked by the negative pressure source, and the air flows into the front side through the solenoid valve 9 to move the diaphragm 1 to the rear side. In this case, when the solenoid valve 9 is closed, the air flowing from the atmosphere receives the resistance of the orifice 12, so that the movement of the diaphragm 1 has a time delay.

[0029]

As described above, the power transmission switching device for a four-wheel drive vehicle according to the present invention, when performing the switching operation from 4WD to 2WD, between the solenoid valve for operating the actuator and the air pressure source, or A flow resistor was provided between the solenoid valve and the open air end to cause a time delay in the operation of the actuator.
Disengagement of the gear to the WD side can be avoided, and generation of an impact sound due to excessive disengagement of the gear can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially omitted cross-sectional view illustrating a power transmission switching device according to a first embodiment.

FIG. 2 is an enlarged cross-sectional view showing the actuator section of FIG. 1;

FIG. 3 is an enlarged cross-sectional view showing a transfer unit of FIG. 1;

FIG. 4 is a sectional view showing the 4WD state in FIG. 2;

FIG. 5 is a sectional view showing the 4WD state in FIG. 3;

FIG. 6 is an enlarged sectional view showing a part of FIG. 5;

FIG. 7 is a partially omitted sectional view showing a power transmission switching device according to a second embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Actuator 3 Rod 4 Push-pull wire 5 Slide gear 6 Rod 7, 8 Air piping 9, 10 Solenoid valve 11 Accumulator 12 Orifice 13, 14 Rotary shaft 15 Key 16 Rotary member 17 Needle roller bearing 18 Rotary member 19, Reference Signs List 20 Gear 21 Sprocket 22 Chain 23 Rotary shaft 24 Fork 25a, 25b High gear 26a, 26b Low gear 27 Neutral gear 28 Slide gear 29 Shaft 30 Gear 31, 32 Needle roller bearing 33 Rod 34 Synchronizer key 35 Center cone 36, 37 Ring

Claims (4)

[Claims] A first rotating member that constantly transmits the rotation of an output shaft of the transmission and transmits power to one of the propulsion shafts of the front and rear wheels; and a first rotating member that is disposed coaxially with the first rotating member. A second rotating member that transmits power to the other propulsion shaft of the front and rear wheels, and a slide member that connects and disconnects the two rotating members by moving forward and backward in the axial direction of the two rotating members; In a power transmission switching device for a four-wheel drive vehicle in which the slide member is connected to an actuator, means for causing a time delay in the operation of the actuator when the slide member shuts off the two rotating members is provided. A power transmission switching device for a four-wheel drive vehicle. 2. The power transmission switching device for a four-wheel drive vehicle according to claim 1, wherein the actuator is operated by air pressure via an electromagnetic valve. 3. A means for causing a time delay in the operation of the actuator includes two pipes for connecting and disconnecting the slide member, the actuator connecting the actuator to the air pressure source via the electromagnetic valve. 3. The power transmission switching device for a four-wheel drive vehicle according to claim 2, further comprising a flow resistor provided between the solenoid valve of the shutoff pipe and a source of air pressure. 4. A means for causing a time delay in the operation of the actuator includes two pipes for connecting and disconnecting the slide member, the actuator connecting the actuator to the air pressure source via the electromagnetic valve. 3. The power transmission switching device for a four-wheel drive vehicle according to claim 2, further comprising a flow resistor provided between the solenoid valve of the connection pipe and an open end of the atmosphere.