JPH075065B2 - Parking brake device for four-wheel drive vehicle - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parking brake device for a four-wheel drive vehicle in which a front wheel is rotatable at a higher peripheral speed than a rear wheel.

(Prior Art) For example, some agricultural tractors have four-wheel drive in order to improve work performance in the field, and a tractor with a front wheel higher than the rear wheel peripheral speed and a small turning radius has been developed. There is.

This type of tractor has a technique disclosed in Japanese Patent Laid-Open No. 59-176121 and the like, which transmits the power of the engine to the front and rear wheels via a front wheel differential device and a rear wheel differential device, respectively. At the same time, the front wheel drive system is equipped with a speed change mechanism that can switch between high and low speeds.When the steering angle of the front wheels exceeds, for example, 40 degrees, it is detected and the speed change mechanism is switched from low speed to high speed. The speed is increased to about twice the peripheral speed of the rear wheels, and the resistance of the front wheels during a small radius turn is reduced to obtain a smooth turn.

By the way, a brake device for an agricultural tractor is provided with a hydraulic brake device for a traveling system on a rear axle and a parking brake operating device for manually operating the hydraulic brake device.

(Problems to be Solved by the Invention) In the above-mentioned related art, the hydraulic brake device is also used as the parking brake, but since the hydraulic brake device may decrease in pressure after a long time, it is used for the parking brake. Not optimal to do. Therefore, it is considered to provide a mechanical friction brake device on the traveling drive force transmission member in the mission to make it a parking brake device. However, newly providing this friction brake device on the transmission shaft is Must be long enough to secure the installation pace, and a gear is also required to extract power from the transmission shaft.

(Means for Solving Problems) According to the present invention, a mechanical parking brake device is provided by using a gear provided on a rear wheel drive system transmission shaft to form a front wheel drive system transmission mechanism. It is intended to solve the problems of the prior art.

That is, as a specific configuration of the problem solving means in the present invention, the transmission in the transmission case has a rear wheel drive system and a front wheel drive system, and the front wheel drive system has a front wheel peripheral speed substantially equal to a rear wheel peripheral speed. A speed change mechanism for switching between high speed and low speed is provided, a pair of transmission gears constituting the speed change mechanism are fixed to a rear wheel drive system transmission shaft, and a brake shaft is provided in parallel with the transmission shaft. Is provided with a mechanical parking brake means for loosely fitting a brake gear meshing with one of the transmission gears and braking the brake gear. The opening of the mission case is provided to insert the brake gear into the mission case from the outside. The brake shaft is supported by a lid which is openably and closably closed, and the operating means for operating the parking brake means is supported by the lid.

(Working) Pull the parking brake lever to mechanical parking brake means 36
When the brake gear 35 is actuated, frictional resistance is applied to the brake gear 35, and the bevel pinion shaft 5 is braked through the transmission gear 15 of the front wheel high / low speed switching mechanism 7 meshing with the brake gear 35, and the rear wheel 11 cannot rotate. To The parking brake means 36 is a friction type but not a hydraulic type, so that the hydraulic pressure does not decrease even after a long time, and the braking force is maintained. The brake shaft 31 and the operating means 49 are supported by a lid 29 that opens and closes the opening 28 of the mission case 27, and by attaching the lid 29 to the mission case 27, the brake gear 35 enters the mission case 27 from the outside. Mesh with the transmission gear 15. The parking brake means 36 is provided on the brake shaft 31 in order to control the brake gear 35, and it is not necessary to arrange it on the transmission shaft 5 provided with the transmission gear 15, and the operating means 49 for operating it is also the lid 29. The parking brake device is attached to the lid 29 and is attached to the transmission when the lid 29 is attached.

(Example) Hereinafter, the Example of this invention is described based on drawing.

1 to 3, reference numeral 1 denotes a transmission of a four-wheel drive type agricultural tractor, and the power of the engine 2 is transmitted to a multi-stage or continuously variable transmission 4 via a main clutch 3 and the transmission 4 is Rear wheel drive system power is transmitted from the bevel pinion shaft (transmission shaft) 5 to the rear wheel diff device 6 at the rear, and front wheel drive system power is transmitted from the bevel pinion shaft 5 to the front wheel diff device 8 via the speed change mechanism 7. To be done.

The rear wheel drive system drives a rear axle 12 supporting a rear wheel 11 from a rear wheel differential device 6 via a left-right final reduction mechanism 10, and each of the rear axles 12 has a hydraulic brake device 13 for traveling. Is provided and can be operated with the foot brake pedal on the tractor.

The front wheel high / low speed switching transmission mechanism 7 of the front wheel drive system includes a pair of transmission gears on a bevel pinion shaft 5 which is a transmission shaft of the rear wheel drive system.
15A and 15B are spline-fitted, and transmission gears 17A and 17B, which are constantly meshed with the transmission gears 15A and 15B, are loosely fitted on the transmission shaft 16 parallel to the bevel pinion shaft 5, so that both transmission gears 17A and 17B
Is selectively fixed to the transmission shaft 16 by a hydraulic clutch 18 provided between them. The gears 15B and 17B are constant speed transmissions with a speed ratio of 1, and the gears 15A and 17A are speed increasing transmissions with a speed ratio of 2, for example, and the speed increasing ratios can be set variously.

The transmission shaft 16 has a gear 19 at the front end, and the gear 19 transmits power via an idler gear 20 and a gear 21 to a bevel pinion shaft 22 provided outside the tractor vehicle body, and the bevel pinion shaft 22 is a front wheel. Power is transmitted to the front wheels 24 via the differential device 8 and the left / right front wheel final reduction mechanism 23.

The front wheels 24 are steered by operating the steering wheel, and the steering mechanism from the steering wheel to the front wheels 24 includes, for example, 40
When it is cut more than once, a means for sensing it is provided, and between the sensing means and the speed change mechanism 7,
There is provided hydraulic control means for actuating the hydraulic clutch 18 in response to a sensing signal.

Reference numeral 26 denotes a parking brake device, and a lid 29 that closes an opening 28 on a side wall of the mission case 27 serves as a support base. A pair of support legs 30 is integrally formed on the lid 29, and the support leg 30 is integrally formed. A brake shaft 31 parallel to the bevel pinion shaft 5 is fixed.

The brake shaft 31 is a center shaft 33 which is fixed to one of the support legs 30 by a screw 32 and a cylindrical shaft spline-fitted to the center shaft 33.
A brake gear 35 is rotatably fitted to the center shaft 33, and a mechanical friction parking brake means 36 is provided on the center shaft 33 and the cylinder shaft 34.

The brake gear 35 always meshes with the transmission gear 15A having the largest diameter in the transmission mechanism 7, and an outer cylinder portion 39 for supporting the plate 38 is integrally formed on one side of the brake gear 35. A brake disc 40 is arranged between the plates 38,
All brake discs 40 are guide rings fixed to the cylinder shaft 34.
41 is slidably supported in the axial direction.

Reference numeral 42 is a brake pusher provided on the cylindrical shaft 34 so as to be slidable in the axial direction. The plate 38 can press the plate 38 against the brake disc 40.
Is actuated to brake the bevel pinion shaft 5 via the gears 35 and 15A.

The brake pusher 42 has a pin 4 at the end of the arm 43 in the circumferential groove 42a.
4, the arm 43 is fixed to the shaft 45 penetratingly supported by the lid 29, and the lever 46 is fixed to the outer end of the shaft 45. The lever 46 is connected to a parking brake lever 50 provided near the tractor seat via a link 47 or a wire, and is rotated by pulling up the parking brake lever 50 to rotate the shaft 45, the arm 43 and the pin 44. The brake pusher 42 is pushed through the pusher. The pin 44 to the parking brake lever 50 constitutes an operating means 49 of the parking brake means 36.

The parking brake device 26 is a cassette type and can be optionally installed, and the transmission gear 15 is used without changing the gear arrangement and the interval between the intermediate walls 48 and 55 supporting the shafts 5 and 16. Can be arranged.

The parking brake means 36 meshes with the large-diameter transmission gear 15 so that the brake gear 35 can be braked with a low friction force.
It may be meshed with the transmission gear 15, and the disposition may be on the side of the bevel pinion shaft 5 but above it. Further, a band brake or the like can be used instead of the friction plate type brake, and the structure of the brake and the brake operating means 49, the shape of the brake shaft, etc. can be variously modified.

(Effect of the Invention) According to the present invention described in detail above, even if the vehicle is parked for a long time, a reduction in braking force due to a decrease in hydraulic pressure does not occur like in a hydraulic brake, and it is necessary to newly provide a transmission gear with which a brake gear meshes. It is also possible to use the transmission gear on the rear-wheel drive system transmission shaft for switching the front wheels between high and low speeds, thereby making it unnecessary to lengthen the transmission shaft or newly install an arrangement space.
The number of members between the parking brake means and the rear wheels is small, the braking efficiency can be maintained at a high level, and the device can be incorporated simply by attaching the lid that closes the opening of the mission case to the mission case. It can be easily and easily attached and detached without affecting the structure, and can be manufactured compactly and inexpensively.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a sectional explanatory view, FIG. 2 is a sectional front view of a main portion, and FIG. 3 is a diagram showing the entire transmission of a tractor. 1 ... transmission, 5 ... bevel pinion shaft (transmission shaft), 7 ... transmission mechanism, 13 ... hydraulic brake device, 15 ... transmission gear, 16 ... transmission shaft, 17 ... transmission gear,
18 …… hydraulic clutch, 26 …… parking brake device, 31 ……
Brake shaft, 35 ... Brake gear, 36 ... Friction braking means.

Claims (1)

[Claims] Claim: What is claimed is: 1. A transmission in a transmission case has a rear wheel drive system and a front wheel drive system, wherein the front wheel drive system has a front wheel peripheral speed which is substantially the same as the rear wheel peripheral speed and a high speed which is a high speed. A transmission mechanism for switching is provided, a pair of transmission gears constituting the transmission mechanism are fixed to a rear wheel drive system transmission shaft, a brake shaft is provided in parallel with the transmission shaft, and one of the transmission gears is provided on the brake shaft.
A mechanical parking brake means for loosely fitting a brake gear meshing with the sheet and for braking the brake gear is provided, and the opening of the mission case is opened and closed so as to insert the brake gear into the mission case from the outside. A parking brake device for a four-wheel drive vehicle, wherein the lid shaft supports the brake shaft, and the lid member supports operating means for operating the parking brake means.