JPS625958Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention normally performs two-wheel drive using one of the front and rear wheels, and when necessary, performs four-wheel drive using both the front and rear wheels. The present invention relates to an automatic switching device for a part-time four-wheel drive vehicle that automatically switches from four-wheel drive to two-wheel drive only during extremely low-speed large steering on a dry paved road.

[Conventional technology and problems]

Previously, as a part-time four-wheel drive vehicle of this kind,
The applicant has already proposed a system in which a transfer clutch is provided in the middle of the rear wheel transmission system, and switching between two and four-wheel drive is achieved by engaging or disengaging this clutch (Utility Model Publication No. 53-24014). (see official bulletin). Therefore, with this system, the front and rear wheels are directly connected when the vehicle is in four-wheel drive due to the engagement of the transfer clutch. The difference in turning radius of the wheels generates torsional torque in the transmission system, resulting in the so-called tight corner braking phenomenon. By the way, in this case, on road surfaces with a small coefficient of friction, one of the front and rear wheels can slip appropriately and release torsional torque, so the steering force is light and there is no inconvenience in steering, and on such roads the vehicle remains in four-wheel drive. is preferable because it ensures maneuverability. However, on dry paved roads, when the front and rear wheels have sufficient tire grip, a large amount of torsional torque is generated without escaping, which increases steering force, worsens maneuverability, and increases tire wear. increases, leading to deterioration in fuel consumption and ride comfort due to vibration and noise. Furthermore, since there is no risk of slipping on such dry paved roads, there is no need to use four-wheel drive.

Therefore, in order to solve the problem that occurs when the steering wheel is turned significantly in a 4-wheel drive state, a steering angle sensor is used to automatically switch the steering angle to 4-wheel drive when the steering wheel is turned beyond a certain level. The applicant has proposed a method of returning to two-wheel drive. However, in this method, the switching is performed regardless of the road surface condition, so the above-mentioned advantage of a small friction coefficient cannot be exhibited.

[Means for solving problems]

The present invention was developed in view of the above circumstances, and the power is directly transmitted to one of the front and rear wheels, and the front and rear wheels are connected as necessary by engaging a transfer clutch.
In a four-wheel drive vehicle configured to transmit power to the other rear wheel, the actuating section of the transfer clutch is connected to a power source via a normally closed switch and a two- and four-wheel drive changeover switch, and the power source is The coil for opening the above-mentioned normally closed switch is connected through the torsion angle displacement detection device of the steering shaft system, and in the case of a very low speed large turn on a dry paved road with 4-wheel drive, the coil is applied to the steering wheel. When a torsion angle exceeding a predetermined value occurs in the steering shaft system due to a large steering force, the torsion angle displacement detection device is turned on and the normally closed switch is turned off to automatically switch to two-wheel drive. It is.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, in the drawings, 4 according to the present invention is shown.
To explain the transmission system of a wheel drive vehicle, there are two types of FF.
It is based on wheel drive, where 1 is the engine crankshaft, 2 is the clutch, 3 is the input shaft,
4 is a manual transmission. The transmission 4 is of a constant mesh type, with an output shaft 5 installed parallel to the input shaft 3, and four sets of gears for shifting from 1st speed to 4th speed on both shafts 3 and 5. 6 to 9 are provided, and each gear change is performed by selecting these gears 6 to 9 via two sets of synchronizing mechanisms 10 and 11 by operating a change lever. Also, one synchronizing mechanism 10 is connected to the reverse gear 12 provided on the input shaft 6.
Reverse speed is obtained by meshing the gear 13 on the sleeve side of the vehicle through an idler gear (not shown).

In addition, an input shaft 3 between the clutch 2 and the transmission 4
A front wheel final reduction device 14 is disposed at the bottom, and one drive pinion 16 of the output shaft 5 meshes with the crown gear 15 of this device 14.
Wheel drive is provided.

The side of the output shaft 5 of the transmission 4 opposite to the drive pinion 16 extends rearward;
A transfer device 17 is attached to the rear of the
The output shaft 5 and the rear drive shaft 20 are configured to be transmitted by the transfer drive and driven gears 18 and 19 of this device 17. Here, the gear 18 is integrally connected to the output shaft 5, while the gear 19 is rotatably fitted to the rear drive shaft 20, and these gears 19 and the rear drive shaft 20 are connected to the hydraulic pressure for switching between 2 and 4 wheel drive. The rear drive shaft 20 is connected by a clutch type transfer clutch 21, and the rear drive shaft 20 is further connected to the propeller shaft 2.
2 to the rear wheel final reduction gear 23.

Oil pump 2 is attached to transfer clutch 21.
A hydraulic circuit is constructed from 4 through a solenoid valve 26 in an oil passage 25, and this valve 26 connects the clutch 21 side of the oil passage 25 to the drain port 28 to drain oil when the solenoid 27 is de-energized as shown in the figure. When the solenoid 27 is energized, the plunger 29
the spool 30 through the return spring 31
By moving against the
Close the oil passage 25 and open the clutch 21.
It is configured to refuel the A two- and four-wheel drive selector switch 32, an ignition switch 33, and a battery 34 on the driver's seat side are electrically connected to the solenoid 27 of the solenoid valve 26 in series.

According to the present invention, in such a configuration, a normally closed switch 35 is provided in the circuit connected from the battery 34 to the solenoid 27 via the 2- and 4-wheel drive changeover switch 32.
The opening coil 35a of No. 5 is connected to the battery side via a switch 36 and a timer 37 of a torsional angle displacement detection device of the steering shaft system. Then, when the changeover switch 32 is turned on and the four-wheel drive mode is on, when the switch 36 is turned on, the switch 35 is turned off for a certain period of time to disconnect the circuit of the switch 32, and the solenoid 27 is turned on to switch to two-wheel drive. is de-energized.

Then, as shown in FIG. 2, shaft 41 from steering wheel 40 connects to universal joint 42.
In the steering shaft system, which is bent by the torque rod 43 and connected to the pinion 45 of the steering gear box 44, the torsional angle displacement detection function is applied to the rubber coupling 46 between the torque rod 43 and the pinion 45, which is capable of torsional angle displacement. A device 47 is provided.

As shown in FIG. 3, in the detection device 47, a member 46b to which the rubber coupling 46 is coupled to the pinion 45 side is arranged with a predetermined angle deviation in the rotational direction from a member 46a to which the rubber coupling 46 is coupled to the torque rod 43 side. Of these members 46a and 46b, a metal fitting 48 having the above-mentioned switch 36 is attached to one member 46a, and a metal fitting 49 for operating the switch 36 is attached to the other member 46b. In this way, the switch 36 is turned on by the metal fitting 49 only when the steering wheel 40 is steered with a large steering force and a predetermined torsional angular displacement occurs in the rubber coupling 46.

In addition, as another embodiment shown in FIG.
A potentiometer 50 is shown between 8 and 49, and when the rubber coupling 46 is torsionally displaced, the resistance change of the potentiometer 50 causes the switch to operate as described above. be.

With this configuration, when the 2- and 4-wheel drive switching switch 32 is turned off, the solenoid 27 of the solenoid valve 26 is de-energized, causing the transfer clutch 21 to drain oil and become released. Therefore, the power of the output shaft 5 of the transmission 4 is not transmitted to the rear wheels, but is transmitted only to the front wheels via the front wheel final reduction gear 14, thus performing two-wheel drive driving using the front wheels.

Next, when the switch 32 is turned on, the solenoid valve 26 is switched to supply oil to the transfer clutch 21 by energizing the solenoid 27, so that the clutch 21 is engaged and the power from the output shaft 5 of the transmission 4 is transferred to the rear wheels. The signal is also transmitted to the rear wheels via the final reduction gear 23, and four-wheel drive driving is performed using the front and rear wheels.

By the way, when operating the switch 32 in four-wheel drive, if the vehicle is steered significantly while driving at an extremely low speed on a road surface with a small coefficient of friction, the tire grip force decreases and slips are likely to occur, resulting in tight corner braking. Since the torsional torque of the transmission system is also small, steering by the steering wheel 40 is relatively easy. Therefore, the rubber coupling 46 does not undergo any torsional angular displacement, and the switch 35 continues to be turned on, maintaining four-wheel drive.

On the other hand, when the tire grip is large, such as on a dry paved road, the increased torsional torque of the transmission system places a large load on the steering system, increasing the steering force of the steering wheel 40. Therefore,
A larger steering force is applied to the steering wheel 40 to overcome such a load, which causes a torsional angular displacement in the rubber coupling 46. Then, the metal fitting 49
The switch 36 is operated to turn on, and the timer 37 de-energizes the solenoid 27 when the switch 35 is turned off for a certain period of time, thus automatically switching to two-wheel drive. Therefore, a large steering force is required to start turning, but after that, the problem associated with tight corner braking disappears when switching to two-wheel drive, and the steering performance is restored and it becomes possible to do it easily.

In the embodiment, the timer 37 is used to maintain the two-wheel drive switching state at least during steering by operating the switch 36 of the torsion angle displacement detection device 47 of the steering shaft system. The present invention is not limited to these embodiments, and various other means can be considered.

[Effect of idea]

As is clear from the above explanation, according to the present invention, the system switches to 2-wheel drive only in the case of extremely low-speed large turning on a dry paved road with 4-wheel drive, and remains in 4-wheel drive on roads with a small coefficient of friction. Since it is preferable to do so, and there are fewer inconveniences caused by it, the switching operation is not made, so on the one hand, the performance of the 4-wheel drive vehicle is fully demonstrated, and on the other hand, the steering force is reduced when switching to 4-wheel drive unnecessarily. Problems such as heavy weight can be resolved. Since switching is performed using the fact that the steering force actually increases, the operation is reliable and there is no risk of malfunction, and the switching time can be kept to the minimum necessary.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the device according to the present invention, Fig. 2 is a side view of the steering shaft system showing the installation location of the torsional angular displacement detection device, and Figs. 3 and 4 are implementations of the device. It is a side view which shows an example. 4...Transmission, 14...Front wheel final reduction gear, 21
... Transfer clutch, 23 ... Rear wheel final reduction gear, 26 ... Solenoid valve, 32 ... 2,
4-wheel drive switch, 40... Steering wheel, 46... Rubber coupling, 47...
...Torsional angular displacement detection device.

Claims (1)

[Claims for Utility Model Registration] 4. A power transmission system in which power is directly transmitted to one of the front and rear wheels, and power is also transmitted to the other of the front and rear wheels by engagement of a transfer clutch as necessary.
In a wheel drive vehicle, the actuating part of the transfer clutch is connected to a power source via a normally closed switch and a two- and four-wheel drive changeover switch, and the power source is connected to a torsional angle displacement detection device of the steering shaft system. When the opening coil of the above-mentioned normally closed switch is connected, and in the case of extremely low-speed large turning on a dry paved road with 4-wheel drive, the large steering force applied to the steering wheel will cause the steering shaft system to have a torsional angle exceeding a predetermined value. An automatic switching device for a four-wheel drive vehicle, characterized in that the switch of the torsional angle displacement detection device is turned on and the normally closed switch is turned off to automatically switch to two-wheel drive.