JPS6346924A - Power transmission device for off-road running vehicle - Google Patents

Abstract

PURPOSE:To make it possible to rapidly select a two wheel drive mode or a four wheel drive mode, optimumly in accordance with the road surface or running condition, by disposing a viscous coupling in a counter shaft for driving front wheels. CONSTITUTION:A counter shaft 30 of a speed change gear 9 for transmitting power from an engine 7, is bi-split into shaft sections 32, 33. One bevel gear 31 in a bevel gear transmitting mechanism 11 for transmitting power to rear wheels 3 is fixed to the shaft section 32. Another bevel gear 18 in a bevel gear transmitting mechanism 17 for transmitting power to front wheels 2, is fixed to the shaft section 33. A viscous coupling 34 is disposed between the shaft sections 32, 33. With this arrangement it is possible to remarkably enhance the manipulatability and dynamic characteristic of an off-road running vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a power transmission device for an all-terrain vehicle, particularly for an all-terrain vehicle called a straddle-type vehicle.

[Prior art]

FIG. 6 is a perspective view of the straddle-type four-wheel vehicle 1. FIG.

The front wheels 2 and rear wheels 3 of this saddle type four-wheeled vehicle 1 are each equipped with balloon tires with low air pressure for traveling on rough terrain. Further, direction change of the saddle type four-wheeled vehicle 1 is performed by a par handle 4, and when the par handle 4 is operated, a wheel steering mechanism (for example, an Ackermann mechanism) (not shown) disposed inside the vehicle body 5 causes the front wheels to change direction. 2 is steered and the direction changes. Further, a transverse engine 7 is mounted on the body frame 6 of the vehicle body 5, and the crankshaft thereof is arranged at right angles to the traveling direction (arrow A) K.

FIG. 7 is a conceptual cutaway sectional view showing a conventional power transmission device for the above-mentioned straddle-type four-wheel vehicle 1, and particularly shows a transmission device having a four-wheel drive function, and the same parts as in FIG. 6 are designated by the same reference numerals. .

The engine 7 mounted on the straddle-type four-wheel vehicle 1 is located in the center of the vehicle. A transmission device 9 that constitutes a part of the power transmission device is arranged inside. The power of the engine 7 is transmitted to the counter shaft 10 of the transmission ff19 via a crankshaft (not shown) disposed perpendicular to the direction of travel of the vehicle.

The power transmitted to the counter shaft 10 is transmitted to the rear axle shaft 14 through a pair of bevel gear transmission mechanisms 11 and 12, which are always arranged on the left side of the crankcase 8, and a 47-drive mechanism 13 arranged between them. communicated. On the other hand, a shaft 15 is rotatably supported in the counter shaft 10, and a dog clutch 16 for connecting and disconnecting power between the shaft 15 and the counter shaft 10 is mounted on the shaft 15. It is arranged.

Further, one bevel gear 18 constituting the bevel gear transmission mechanism 17 is fixed to the tip of the shaft 15, and this bevel gear 18 is fixed to the rear end of a shaft 19 whose one end protrudes from the tip of the crankcase 8. It meshes with the bevel gear 20. Therefore, when the dog clutch 16 is moved to the left and the counter shaft 10 and the shaft 15 are fixed together, the power transmitted to the counter shaft 10 is transferred to the shaft 19 through the bevel gear transmission mechanism 17 consisting of bevel ears 18 and 20. transmitted to. The tip t of this shaft 19 is the universal joint 2
One end of the propeller shaft 22 is connected to the propeller shaft 22 via the propeller shaft 1, and the other end is connected to a differential device (not shown) in a gear case 23 disposed at the front of the vehicle. Therefore, the power transmitted to the shaft 19 is also transmitted to the differential device in the gear case 23 via the propeller shaft 22.

In FIG. 7, reference numeral 24 is a universal joint that connects the pair of bevel gear transmission mechanisms 11, 12 and the shaft drive mechanism 13, and 25 is a brake device for the rear wheel 3.

According to such a conventional power transmission device for a straddle-type four-wheel vehicle, when the dog clutch 16 described above is moved to the left by an operation means (not shown) and the counter shaft 10 and the shaft 15 are fixed, the engine 7 is stopped. A four-wheel drive system is selected in which power is always transmitted to a rear axle shaft 14 shown in FIG. 7 and a differential device housed in a gear case 23 to simultaneously drive the front wheels 2 and rear wheels 3. Further, when the dog clutch 16 is operated by the operating means to release the fixation between the counter shaft 10 and the shaft 15, the two-wheel drive system that drives only the rear wheels 3 is selected.

By the way, according to the conventional power transmission device described above, switching between the four-wheel drive system and the two-wheel drive system must be performed manually by moving the side dog clutch 16 from side to side, which is troublesome and difficult to do. In particular, in an off-road vehicle whose main purpose is to drive on rough terrain, it is almost impossible to quickly respond to rapidly changing road conditions and manually select an optimal drive system. Furthermore, according to the conventional power transmission device described above, the circumferential speeds of the front and rear wheels are the same during four-wheel drive, and therefore, when a straddle-type four-wheel vehicle turns around a curve, the front wheels' turning radius A braking phenomenon occurred due to the difference in the turning radius of the rear wheels, leading to uneven tire wear, loss of airflow, and reduced maneuverability.

[Purpose of the invention]

This invention solves the above-mentioned problems [i.
A straddle-type four-wheel vehicle that can quickly switch between a two-wheel drive system and a four-wheel drive system, and further reduces as much as possible the braking phenomenon that occurs during turning during four-wheel drive. Provides a power transmission device.

[Structure of the invention]

In order to achieve the above-mentioned object, this invention uses an engine mounted on a vehicle to drive the rear wheels, and a portion of the power that drives the rear wheels is transmitted to the front of the vehicle via a countershaft to drive the front wheels. In the power transmission device for an all-terrain vehicle, the counter shaft is divided into two, and a viscous joint is interposed between the two divided counter shafts to reduce the difference in rotation between the two divided counter shafts. It is designed to increase the power that drives the front wheels as the vehicle increases.

[Example] Hereinafter, an example of the power transmission device according to the present invention will be described in detail.

1 and 2 are a cutaway cross-sectional view and a side view of main parts showing a power transmission device for an all-terrain vehicle according to the present invention, particularly an all-terrain vehicle called a straddle-type four-wheel vehicle, and FIG. The same parts as in FIGS. 6 and 7 are designated by the same reference numerals.

In this power transmission device, a counter shaft 30 (FIG. 1) of a transmission 9 that transmits power from an engine 7 is connected to a shaft portion 32 to which one bevel gear 31 of a bevel gear transmission mechanism 11 that transmits power to a rear wheel 3 is fixed. and a shaft portion 33 to which the other bevel gear 18 of the bevel gear transmission mechanism 17 that transmits power to the front wheel 2 is fixed.
A viscous joint 34 is interposed between the three. This viscous coupling 34 has a housing 35 and a hub 36, as shown in FIG.
, an outer plate 37 supported by the housing 35, an inner plate 38 supported by the hub 36, and a high viscosity silicone oil filled between these plates 37 and 38.
5, one shaft portion 32 of a counter shaft 30 is fixed by a spline, and the other shaft portion 33 is fixed to a hub 36. This viscous joint 34 is connected to the housing 35
and the rotation difference between the hub 36, in other words, the counter shaft 30
This is a joint that increases the transmission torque (coupling force) from one shaft part to the other shaft part in response to an increase in the rotational difference between one shaft part 32 and the other shaft part 33, and the graph shown in FIG. 4 As shown by curve B, as the rotational difference M increases, the transmission torque T increases, and when the rotational difference M disappears, the transmission torque T becomes approximately O, cutting off the transmission of power.

In FIG. 3, reference numeral 39 is a damper device, and this damper device 39 connects one bevel gear 31 to the other bevel gear 4 of the bevel gear transmission mechanism 11 that transmits power to the rear wheels.
This is to absorb sudden torque fluctuations to 0. Further, in FIG. 3, reference numeral 41 indicates one shaft portion 3 of the counter shaft 30.
2, a dog clutch is slidably installed, and by operating this dog clutch 41, one of the drip gears 42 and 34 is selected to switch the gear ratio. In FIG. 1, the reference numeral 44 is a gear case housing a differential device, which will be described in detail below. Inside this gear case 44, there are three types of power cutoff, differential, and differential lock as shown in FIG. A differential device 45 is housed therein which performs two functions.

In this differential device 45, the right wheel drive shaft 4 that drives the front wheels
6, a side gear 49 fixed to the left wheel drive shaft 48, and these side gears 4
A ring gear 53 is rotatably supported by a toothed portion 52 & of a differential case 52 that supports a pinion 50.51 that meshes with 7,49 IC. And this ring gear 53
An operating means 54 for selecting the three functions of the differential gear 45 is arranged on the side of the differential gear 45. This operating means 54 is
Consisting of a dog clutch member 55, a shifter fork 56 for operating this member 55, and a shifter cam 57, the shifter cam 57 is manually rotated via a cable (not shown), and the dog clutch member 55 is moved by the shifter fork 56 as shown in the drawing. When the dog clutch member 55 is moved to the right side by a predetermined stroke, the differential and differential lock functions of the differential gear 45 are selected, and when the dog clutch member 55 is still moved to the left side in the drawing, the ring gear is moved relative to the differential case 52. 53 rotates freely, and the power of the drive pinion 58 connected to the shaft 22 shown in FIG. 1 is cut off.

Next, the operation of the power transmission device described above will be explained, and the configuration will also be explained in detail.

When the straddle-type four-wheel vehicle travels normally, that is, when traveling straight on a flat road surface, the operating means 54 shown in FIG. 5 is operated to set the actuating device 45 to carry out its normal operating function. do. During such normal running, the circumferential speeds of the front wheels 2 and rear wheels 3 shown in FIG. Therefore, the transmission torque of the viscous joint 34 becomes 0, and the power of the engine 7 is not transmitted to the front wheels via one shaft portion 33 of the counter shaft 30, but is transmitted only to the rear wheels 3. Become. That is, during normal driving, the two-wheel drive system with only the rear wheels is selected.

On the other hand, if the load applied to the rear wheels 3 suddenly decreases when driving on rough terrain, etc., causing the wheels to spin (an example of such a case is when the rear wheels slip on a muddy or frozen road surface). In this case, the difference in rotation between the shaft portions 32 and 33 of the counter shaft 30 shown in FIG.
Since the torque transmitted to the rear wheels is large, part of the power of the ennon 7 that drives the rear wheels is transmitted to the front wheels 2 via the counter shaft 30. That is, when driving on rough terrain, etc., the four-wheel drive system is selected depending on the necessity.

Furthermore, when the vehicle turns around a curve or the like, the front wheel turning radius and the rear wheel turning radius are different, so the circumferential speed of the front wheels and the circumferential speed of the rear wheels are different, and the counter shaft 30 shown in FIG. A rotation difference is given between the shaft portion 32 and the shaft portion 33, and therefore the viscous joint 3
4, the power of the engine 7 is transmitted to the front wheels to make the peripheral speeds of the front and rear wheels the same, but in this case, the difference in rotation is small and the transmitted torque is also small, so the front wheels' The circumferential speed is not synchronized with the rear wheels, and each circumferential speed is maintained according to the turning radius. Therefore, no braking phenomenon occurs during turns.

Note that the power cutoff function of the actuating device 45 (FIG. 6) is as follows:
In particular, it can be used to prevent power loss during normal two-wheel driving, and the differential lock function transmits power evenly to the front two wheels to stabilize the vehicle when driving on rough terrain. You can use it if you want to secure it.

Incidentally, in the above-mentioned embodiment, an actuation device having the above-mentioned power cutoff, differential, and differential lock functions is used as the actuation device, but the present invention is of course not limited to the above-mentioned embodiment. An actuation device having only normal actuation functions may also be used.

〔Effect of the invention〕

This invention uses a simple configuration in which a viscous joint is interposed on the countershaft that drives the front wheels, so that the optimal two-wheel or four-wheel drive system can be quickly and automatically selected depending on the road surface and driving conditions. Since braking phenomena during turns are prevented as much as possible, the maneuverability and dynamic characteristics of the vehicle traveling on rough terrain can be significantly improved. Further, since there is no need for an operating means for manually selecting a drive system as in the past, the number of parts and assembly steps can be reduced, and a straddle-type four-wheel vehicle can be provided at a low cost.

[Brief explanation of drawings]

1 and 2 are conceptual diagrams and side views of the power transmission device according to the present invention, and FIG. 3 is an enlarged sectional view of the main parts of FIG.
FIG. 4 is a graph showing the characteristics of a viscous joint, FIG. 5 is an enlarged sectional view of a differential, and FIG. 6 is a perspective view of a straddle-type four-wheel vehicle.
FIG. 7 is a conceptual diagram showing a conventional power transmission device. 1...Saddle type four-wheel vehicle, 2...Front wheel, 3...Rear wheel,
7... En Shin, 30... Counter axis, 34.
...Viscous joint. Figure 6

Claims (2)

[Claims] (1) Power for an all-terrain vehicle in which the rear wheels are driven by an engine mounted on the vehicle, and part of the power from the engine is transmitted to the front of the vehicle via a countershaft to drive the front wheels. A power transmission device for an all-terrain vehicle, characterized in that the counter shaft is divided into two, and a viscous joint is interposed between the two divided counter shafts. (2) The power transmission device for an all-terrain vehicle according to claim (1), wherein the all-terrain vehicle is a straddle-type four-wheel vehicle.