JP2559240Y2 - Drive switching device for four-wheel drive vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a drive switching device for a four-wheel drive vehicle such as a four-wheel drive tractor.

[Problems to be Solved by Conventional Techniques and Inventions] Generally, in this type of four-wheel drive vehicle, when the vehicle is always driven by four-wheel drive, there are disadvantages such as early wear of tires and an increase in turning radius. For this reason, there is a configuration that can be switched to two-wheel drive when necessary. However, conventionally, the drive switching has been performed by the operator determining whether or not the switching is necessary and manually operating the switching operation tool one by one, so that the operation is troublesome and complicated, and the operability is a problem. In addition, it is impossible to avoid the above-mentioned problems such as early wear of the tire due to forgetting the switching operation.

On the other hand, there is also known an apparatus which can automatically switch between four-wheel drive and two-wheel drive.
There is a problem that the structure is complicated, the number of parts is large, and the cost must be high.

[Means for Solving the Problems] The present invention has been conceived in order to provide a drive switching device in a four-wheel drive vehicle that can eliminate these disadvantages in view of the above situation. In a four-wheel drive vehicle including a front wheel drive mechanism that draws power from the middle of a rear wheel drive mechanism that transmits power to the rear wheels from the engine and transmits the power to the front wheels, the rear wheel drive mechanism transmits the power to the front wheel drive mechanism. The power draw is set by setting the power transmission ratio between the front wheel drive mechanism and the rear wheel drive mechanism such that the front wheel drive peripheral speed is slower than the rear wheel drive peripheral speed, and the one-way rotation provided in the front wheel drive mechanism A drive-side helical gear into which the drawn-out driving force is input, a driven-side clutch gear fixed to a power transmission shaft to a front wheel, and a clutch disposed opposite to the driven-side clutch gear; A drive that is freely rotatable about the shaft and is supported by the power transmission shaft so as to move in a thrust direction toward the driven clutch gear by a thrust force received from the driving helical gear, and meshes with the driven clutch gear as the thrust moves. A movable gear body formed with a side clutch gear, and the drive clutch gear and the driven clutch gear mesh with each other in order to transmit power only in the rotational direction of the movable gear body based on the rotation of the drive helical gear. It is characterized in that it is set to mesh.

According to the present invention, an automatic drive switching operation can be performed by this structure with a simple structure.

Next, an embodiment of the present invention will be described with reference to the drawings.
In the drawings, reference numeral 1 denotes a traveling body of a tractor, and the traveling body 1 includes an engine 3 installed below a bonnet 2.
Of the PTO shaft 5 and the front and rear wheels 6 and 7 via the power transmission mechanism built in the transmission case 4
It is configured to transmit to That is, the engine power is distributed to the PTO transmission shaft 8 and the wheel transmission shaft 9, and the power distributed to the wheel transmission shaft 9 is transmitted to the front wheel transmission shaft 10 and the rear wheel The drive mechanism is distributed to the rear wheel transmission shaft 11, and the power transmission ratio of these drive mechanisms is set so that the drive peripheral speed of the front wheels 6 is lower than the drive peripheral speed of the rear wheels 7.

Reference numeral 12 denotes a drive side helical gear. The drive side helical gear 12 is provided on the rear wheel transmission shaft 11 so as to be rotatable integrally therewith, and is engaged with a movable gear body (driven side helical gear) 13 to be described later. Such power transmission to the front wheel transmission shaft 10 is performed. On the other hand, the movable gear body 13 is externally fitted via a bearing 14 so as to be freely rotatable and movable in the thrust direction with respect to the front wheel transmission shaft 10, but moves forward due to a thrust force received from the drive side helical gear 12. During power transmission and reverse power transmission, they move in opposite thrust directions. Further, driven-side clutch gears 15, 16 located at predetermined intervals on both sides of the movable gear body 13 are spline-fitted to the front wheel transmission shaft 10 so as to be integrally rotatable, and the clutch gears 15, 16
The power transmission is performed by engaging the driving clutch gears 13a and 13b integrally formed on both side surfaces of the movable gear body 13 by moving the movable gear body 13 in opposite thrust directions. The drive-side clutch gear 13a and the driven-side clutch gear 15 meshing with each other during the forward power transmission rotate together only in the rotation in the forward-direction power transmission direction. Are constituted by one-way clutch mechanisms 17 and 18 which rotate integrally only when rotating in the reverse power transmission direction. A is a clearance set between the clutch gears, and B is a bite angle of a rising portion of the meshing tooth in each clutch gear.

In the embodiment of the present invention configured as described above, in the forward state, the movable gear body 13 moves in the direction of the driven clutch gear 15 and the one-way clutch mechanism 17 is connected to transmit the forward power to the front wheel 6. However, when the traveling body 1 is traveling without slipping, since the driving peripheral speed of the front wheels 6 is set lower than the driving peripheral speed of the rear wheels 7, the movable gear body 13 When the rotation speed is lower than the rotation speed of the front wheel transmission shaft 10 receiving the driven rotation of the front wheel 6, the vehicle enters the idling state, whereby the power transmission to the front wheel 6 is cut off and the vehicle is automatically switched to the two-wheel drive state. Also, in the reverse state, the movable gear body 13 moves in the opposite direction to keep the one-way clutch mechanism 18 in the continuous state, but in the non-slip state, the four-wheel drive is automatically performed as in the case of the forward movement. Motorcycle It will be switched on. Further, when the vehicle is turning, the front wheel 6 travels with a larger turning diameter than the rear wheel 7 as shown in FIG. 7, so that the movable gear 13 has a front wheel transmission shaft whose rotation speed is driven to rotate.
The idle rotation is performed at a speed lower than the rotation speed of 10, thereby cutting off the power transmission to the front wheels 6 and automatically switching to the two-wheel drive state.

As described above, the vehicle in which the present invention is implemented is configured such that the vehicle can be switched to the two-wheel drive as necessary, but when traveling on the road where two-wheel drive is desirable (non-slip state) or when turning the vehicle. In, the automatic switching from four-wheel drive to two-wheel drive is performed. Therefore, the switching between the two-wheel drive and the four-wheel drive can be performed without the operator having to manually perform the switching operation after each time the operator determines whether or not the switching is necessary as in the related art. In addition, operability can be improved by eliminating a complicated switching operation. In addition, since the switching operation is not forgotten, troubles such as early wear of the tire due to the forgetting of the switching operation can be avoided, which can contribute to the improvement of the durability of the four-wheel drive vehicle.

In addition, the switching between the four-wheel drive state and the two-wheel drive state is performed when the front-wheel drive peripheral speed is slower than the set front-wheel drive peripheral speed that is slower, but otherwise equal or faster. In this case, the movement can be automatically performed by the movement of the movable gear body 13 due to the change in the thrust force. As a result, the automatic two-wheel-four-wheel drive can be switched, but the switching is performed by the helical meshing. Can be achieved by utilizing the thrust force based on the above, the number of parts is small and the structure can be simple.

Further, this apparatus is configured to perform drive switching based on slip or body turning, but is configured without using any rotation sensor for detecting wheel rotation, angle detection sensor for detecting steering angle, or the like. So
This is convenient without complicating the structure and increasing the number of parts.

The present invention is, of course, not limited to the above-described embodiment, and the position of the drive switching mechanism including, for example, a helical gear and a one-way clutch can be freely set as long as the position is within the front wheel drive mechanism. Can be. It goes without saying that the present invention can be applied not only to tractors but also to four-wheel drive vehicles such as riding rice transplanters.

[Effects] In summary, since the present invention is configured as described above, it is possible to switch between two-wheel drive and four-wheel drive.
If the front wheel drive peripheral speed, which is set by pulling power from the rear wheel drive mechanism to the front wheel drive mechanism, becomes slower than the slowdown, the one-way rotating clutch will be in the continuous state and will be in the four-wheel drive state, If the front wheel drive peripheral speed is about the same as or faster than the rear wheel drive peripheral speed during non-slip, airframe turning, etc., the two-wheel drive state in which the one-way rotating clutch idles and power transmission to the front wheels is cut off Automatically switches to Therefore, the automatic switching to the driving state suitable for traveling is performed without the operator having to manually operate the switching operation tool after each time the operator determines whether the switching is necessary as in the conventional case. Performance can be improved.

In addition, the automatic switching between the two-wheel and four-wheel drive states is performed when the front wheel drive peripheral speed is slower than the set front wheel drive peripheral speed is slowed down and when the front wheel drive peripheral speed is not slower. It is performed by making good use of the change in the thrust force received by the body.
While the four-wheel drive can be switched, the number of parts is small and the structure can be simple.

[Brief description of the drawings]

1 shows an embodiment of a drive switching device in a four-wheel drive vehicle according to the present invention. FIG. 1 is a side view of a tractor, FIG. 2 is a transmission circuit diagram of a power transmission mechanism of the same, and FIG. FIG. 4 is a cross-sectional view of the same main part, FIG. 4 is a side view of the same main part, and FIG.
6B is a side view of the tractor showing the operation at the time of forward movement, FIGS. 6A and 6B are plan views of the tractor showing the operation at the time of turning, and FIGS. In the figure, 1 is a traveling body, 6 is a front wheel, 7 is a rear wheel, 10 is a front wheel transmission shaft, 12 is a driving helical gear, 13 is a movable gear body, 13
Reference numerals a and 13b denote driving clutch gears, reference numerals 15 and 16 denote driven clutch gears, and reference numerals 17 and 18 denote one-way clutch mechanisms.

Claims (1)

(57) [Scope of request for utility model registration] 1. A four-wheel drive vehicle comprising a front wheel drive mechanism that draws power from a midway of a rear wheel drive mechanism that transmits power from an engine to a rear wheel and transmits the power to a front wheel. Power is drawn to the drive mechanism by setting the power transmission ratio between the front wheel drive mechanism and the rear wheel drive mechanism so that the front wheel drive peripheral speed is slower than the rear wheel drive peripheral speed. A driven helical gear to which the extracted driving force is input, a driven clutch gear fixed to a power transmission shaft to a front wheel, and a driven clutch gear disposed opposite to the driven clutch gear. The power transmission shaft is freely rotatable and is supported by the power transmission shaft so as to be thrustly moved toward the driven clutch gear by a thrust force received from the driving helical gear. And a movable gear body formed with a drive-side clutch gear for meshing with the side-side clutch gear. A drive switching device for a four-wheel drive vehicle, wherein the drive switching device is set to engage so as to transmit power only in the direction.