JPH054246B2 - - Google Patents

Description

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

(Prior Art) Four-wheel drive vehicles that simultaneously drive front and rear wheels are well known. In the case of four-wheel drive, it is desirable that the vehicle speeds of the front and rear wheels be equal when driving straight ahead. However, when turning, as shown in Fig. 12, the turning radius R of the front wheels 50 is larger than the turning radius r of the rear wheels 51, so the turning radius will become larger unless the vehicle speed of the front wheels is made faster than the vehicle speed of the rear wheels. .

In this way, with four-wheel drive, it is necessary to change the vehicle speed of the front and rear wheels when traveling straight and when turning.

However, since the four-wheel drive system that distributes engine power between the front and rear wheels usually consists of a gear transmission, it is extremely difficult to change the vehicle speed of the front and rear wheels to the optimum speed each time. Ta.

Therefore, conventionally, the vehicle speed of the front wheels is set faster than the vehicle speed of the rear wheels, and when traveling straight, the vehicle is driven with slippage between one of the wheels (the front wheel for a tractor) and the ground, and when turning, the vehicle speed is set faster than the rear wheels. Vehicles that allow the front wheels to rotate at high speed and turn with a small turning radius have already been proposed.

In addition, the front/rear wheel speed ratio is approximately 1, and a one-way clutch is inserted in the middle of the front wheel power transmission shaft to transmit power only from the engine side, so that when driving straight,
A four-wheel drive vehicle has already been proposed that uses a one-way clutch to cut off power transmission when turning, allowing the front wheels to idle and reducing the turning radius.

In addition, there have already been proposals that operate the four-wheel drive system on and off in order to drive only the rear wheels when driving straight ahead, and use four-wheel drive when turning or when the rear wheels slip.

(Problems to be solved by the invention) The above-mentioned vehicle in which the front/rear wheel speed ratio is 1 or more,
When driving straight, there is a problem of slipping between the front wheels and the ground, which causes wire wear.Moreover, with a one-way clutch, there is a problem that the engine brake is not effective, and with two-wheel drive or four-wheel drive The devices that turn on and off had problems such as being troublesome to operate and having poor drivability.

Therefore, the present invention automatically switches between two-wheel drive and four-wheel drive when necessary, and not only eliminates the hassle of lever operation by the driver, but also solves problems such as earth pushing when turning and tire wear when driving straight. To provide a four-wheel drive device which can realize economical fuel consumption as a two-wheel drive system, and also has engine braking on the front wheels.

(Means for Solving the Problems) In order to achieve the above object, the present invention takes the following measures. That is, the present invention is characterized in that the center portion of the no-spin differential device is interlocked and connected to the engine power transmission shaft that transmits engine power to the rear wheels, and the front wheel power transmission shaft is connected to one side portion of the no-spin differential device. , a rotational resistance imparting means is provided on the other side portion, a rear wheel power transmission shaft is connected to the engine power transmission shaft, and the front wheel speed due to engine power is set lower than the rear wheel speed, so that the rotational resistance of the one side portion during engine braking is set. The reason is that the rotation speed is set higher than that of the other side.

(Operation) According to the present invention, engine power is transmitted to the center portion of the no-spin differential device via the engine power transmission shaft, and is transmitted to the rear wheels via the rear wheel power transmission shaft. Engine power transmitted to the center portion is transmitted to one side portion through engagement of clutch teeth, and from the side portion to the front wheels via a front wheel power transmission shaft.

In the above state, both the front wheels and the rear wheels are driven, resulting in four-wheel drive. In this state, the front/rear wheel speed ratio is set to be smaller than 1, so when the vehicle is traveling straight, the front wheels are pushed by the rear wheels and try to rotate faster than the set value. That is, since the front wheels receive driving force from the ground side and rotate at high speed, the number of rotations at the side portions tends to be higher than the number of rotations at the center portion. In this state, the side part on the front wheel side moves relative to each other within the circumferential play of the clutch teeth, causing the cam teeth to run over each other and disengaging the clutch teeth, and the power is transferred between the side part and the center part on the front wheel side. Transmission is disconnected.

Therefore, the front wheels follow the ground and rotate at the same vehicle speed as the rear wheels, and no slip occurs between the front wheels and the ground.
That is, in this case, only rear wheel drive is available.

Furthermore, even when turning under the above conditions, the front wheels rotate at a higher speed than the set value, so the power between the front wheel side parts and the center part is cut off, resulting in rear wheel drive.

On the other hand, if the rear wheels slip for some reason and the vehicle speed decreases, the front wheel rotational speed also decreases, until the side and center rotational speeds become the same, and the cam teeth engage and the clutch teeth engage. , power is transmitted between the side parts and the center part, and the front wheels are driven by engine power, resulting in four-wheel drive, allowing the rear wheels to escape from slippage.

Also, when applying engine braking, be sure to
The rear wheels receive driving force from the ground. At this time, since the front/rear wheel speed ratio is set to be smaller than 1, if the rear wheels rotate at the set value, the front wheels rotate faster than the set value. That is, the side portions tend to rotate faster than the center portion. In this case, there is no relative rotation between the clutch teeth and the cam teeth do not run over, so power transmission is maintained and engine braking also acts on the front wheels.

Furthermore, if for some reason the front wheels slip without receiving braking force from the ground, the front wheel rotational speed will be lower than the rear wheel rotational speed, so the clutch teeth will be disconnected and engine braking will only apply to the rear wheels.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

What is shown in FIG. 1 is a four-wheel drive device 2 provided within a transmission case 1 of a tractor. In the figure, reference numeral 3 denotes an engine power transmission shaft, and the transmission shaft 3 is operatively connected to the engine via a transmission and a clutch (not shown).

Reference numeral 4 denotes a front wheel power transmission shaft, and the transmission shaft 4 is interlocked and connected to the front wheels via a front wheel differential device (not shown) or the like.

Reference numeral 5 denotes a rear power transmission wheel oil, and the transmission shaft 5 is interlocked and connected to a rear wheel (not shown) via a rear wheel differential device 9.

The above-mentioned rear wheel power transmission shaft 5 and engine power transmission shaft 3
is integrally molded.

The engine power transmission shaft 3 and the front wheel power transmission shaft 4
are interlocked and connected via a no-spin differential device 10. That is, a no-spin differential device 1 is attached to an engine power transmission shaft 3 that transmits engine power to the rear wheels.
0 center portions 27 are interlocked and connected.

The front wheel no-spin differential device 10 has a pair of left and right cases 11 and 12, and a center clutch portion 13 made of an annular body is sandwiched between both cases 11 and 12 and integrally fixed with bolts 14. Both ends of each case 11, 12 have bearings 15,
16 to the partition wall 17,1 of the mission case 1
It is rotatably supported by 8. One case 11
The end of the front wheel power transmission shaft 4 is relatively rotatably inserted into the rotational center of the other case 12, and the end of the inertial shaft 7 is relatively rotatably inserted into the rotational center of the other case 12. . That is, the front wheel power transmission shaft 4 and the inertial shaft 7 are arranged on the same axis, and their respective ends face each other within the cases 11 and 12 of the no-spin differential device 10.

A spline is formed at each end of the front wheel power transmission shaft 4 and the inertia shaft 7, and flanged spline sleeves 19 and 20 are spline-fitted to the spline. The flanges 21, 22 of the spline sleeves 19, 20 abut against the inner surfaces of the cases 11, 12, and are restricted from moving outward in the axial direction.

A propeller 8 (rotational resistance imparting means) is fixed to the outer end of the inertial shaft 7 and stirs the lubricating oil within the mission case 1.

Rectangular clutch teeth 23 are formed on both end surfaces of the center clutch portion 13, which is an annular body, at equal intervals in the circumferential direction (see FIG. 2).

A center cam portion 24 made of an annular body is disposed concentrically with the center clutch portion 13 on the inner peripheral surface side of the center clutch portion 13.
and the center cam portion 24 are connected via a snap spring 25 so as to be relatively rotatable by a predetermined amount in the circumferential direction.

Trapezoidal cam teeth 26 are formed on both end surfaces of the center cam portion 24 at equal intervals in the circumferential direction, corresponding to the clutch teeth 23 (see FIG. 3).

The center clutch portion 13 and center cam portion 24
A center portion 27 is formed by
Side portions 28 and 29 are provided on both sides of.

Clutch teeth 30 that mesh with the clutch teeth 23 with a predetermined gap S in the circumferential direction (see FIG. 2) are formed on the end faces of the side portions 28 and 29 facing the center portion 27, and the cam Cam teeth 31 are formed that closely mesh with the teeth 26 in the circumferential direction.

The side portions 28 and 29 are spline-fitted to the spline sleeves 19 and 20 so as to be movable in the axial direction.

A biasing means consisting of a compression coil spring 32 is interposed between the flange 21 of the spline sleeve 19 located at the end of the front wheel power transmission shaft 4 and the side portion 28, and the side portion 28 is pressed toward the center portion 27. Clutch teeth 23, 30 and cam teeth 2
6 and 31 are maintained.

A biasing means consisting of a spring 33 is also interposed between the spline sleeve 20 located at the end of the inertial shaft 7 and the side portion 29, and presses the side portion 29 against the center portion 27.

An input gear 34 is fixed to the case 11, and the input gear 34 is always meshed with a gear 35 provided on the engine power transmission shaft 3.

Thus, the engine power is transmitted to the engine power transmission shaft 3 → gear 35 → gear 34 → case 11 → center part 27, and then the power is divided into two parts, one of which is divided into two parts: center part 27 → side part 28 → The power is transmitted from the spline sleeve 19 to the power transmission shaft 4 to drive the front wheels, and the other power is transmitted from the center portion 27 to the side portions 29 to the spline sleeve 20 to the inertia shaft 7 to rotate the propeller 8. Further, the power of the engine power transmission shaft 3 is directly transmitted to the rear wheel power transmission shaft 5.
is transmitted to drive the rear wheels.

In the tractor having the four-wheel drive device 2 configured as described above, the ratio of the front wheel speed to the rear wheel speed is (front wheel speed)/(rear wheel speed)<1.

That is, when the front wheel power transmission shaft 4 and the rear wheel power transmission shaft 5 rotate at a constant speed of 1:1, the vehicle speed of the front wheels is set to be slower than the vehicle speed of the rear wheels.

Therefore, as shown in FIGS. 2 and 3, when the center portion 27 is driven in the direction of the bold arrow by the engine power, both clutch teeth 23, 23 of the center portion 27
The clutch teeth 30, 30 of each side portion 28, 29 are engaged to transmit power, and both cam teeth 26, 26 of the center portion 27 are engaged with the clutch teeth 30, 30 of each side portion 28, 29.
1 and 31 to maintain the fitted state.

However, since the front wheel speed is set slower than the rear wheel speed, the front wheels are pushed by the rear wheels, and driving force is applied from the ground, causing the front wheels to rotate faster than the set value. Then, as shown in FIGS. 4 and 5, the side portion 28 on the side of the front wheel power transmission shaft 4
tries to rotate quickly within the circumferential gap S between the clutch teeth 23 and 30, and due to this relatively high speed rotation, the cam teeth 26 and 3 of the side portion 28 and the center portion 27
1 rides up against the spring 32, the clutch teeth 23 and 30 are disengaged, and the front wheels are now in an idle state. At this time, the inertial shaft 7 acts as a resistance to the cam-out and facilitates the cam-out.

That is, in the above-mentioned state, when the tractor is traveling straight with the engine driven, only the rear wheels are driven, and the front wheels rotate to follow the ground. This condition is the same even when turning.

However, in the above condition, if the rear wheels fall into muddy ground and slip, the vehicle will stop moving and the front wheels will no longer receive driving force from the ground, so the rotational speed of the front wheel power transmission shaft 4 will decrease and the rear wheels will not move forward. When the speed becomes the same as that of the wheel power transmission shaft 5, the clutch portion 37 is engaged as shown in FIGS. 2 and 3, and engine power is transmitted to the front wheels.

In other words, when the rear wheel is in a spring state,
Both the front and rear wheels are engine driven, making it a four-wheel drive vehicle.

On the other hand, when applying engine braking, the 6th
As shown in FIGS. 7 to 7, power is transmitted from the side portions 28 to the center portion 27. At this time, since the front/rear wheel speed ratio is smaller than 1, the rotation speed of the front wheel power transmission shaft 4 tends to be higher than that of the rear wheel power transmission shaft 5.

However, since there is no gap S between the clutch teeth in this direction, the clutch teeth 23 and 30 are still
The conditions shown in Figs. 6 and 7 are maintained, and engine braking is applied to both the front and rear wheels.

Therefore, during engine braking, slipping occurs between the rear wheels or the front wheels and the ground.

During this engine braking, if the front wheels slip for some reason and the rotational speed of the front wheel power transmission shaft 4 becomes lower than the rotational speed of the rear wheel power transmission shaft 5, as shown in Figs. Part 27
Relative rotation occurs between the side portion 28 and the cam tooth 2.
6, 31 rides up and releases the engagement of the clutch teeth 23, 30, and the engine brake acts only on the rear wheels.

Note that the present invention is not limited to the above embodiment, and the inertial shaft may be a PTO shaft (rotating device).

(Effects of the Invention) According to the present invention, the front wheels are rotated freely when the engine drive is running straight or when turning, and the front wheels are driven without lever operation when the rear wheels slip, and then when the engine brake is applied, even when turning In addition, the no-spin differential device can be used by simply adding rotational resistance imparting means to a commercially available device, and is extremely simple to manufacture. Can be used to drive.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Figs. 2 to 11 are explanatory views showing the disengaged state of the clutch teeth and cam teeth, and Fig. 12 shows the difference in wheel speed when turning. It is an explanatory diagram to explain. 3...Engine power transmission shaft, 4...Front wheel power transmission shaft, 5...Rear wheel power transmission shaft, 10...No spin differential device, 13...Center clutch portion, 23...
...Clutch tooth, 24...Center cam part, 26...
Cam tooth, 27... Center portion, 28, 29... Side portion, 30... Clutch tooth, 31... Cam tooth, 3
2, 33...Biasing means.

Claims (1)

[Claims] 1. The center part of the no-spin differential device is interlocked and connected to the engine power transmission shaft that transmits engine power to the rear wheels, the front wheel power transmission shaft is connected to one side part of the no-spin differential device, and the rotational resistance imparting means is attached to the other side part. The rear wheel power transmission shaft is connected to the engine power transmission shaft, and the front wheel speed due to engine power is set lower than the rear wheel speed, and the rotational speed of one side part during engine braking is set higher than the other side part. A four-wheel drive device that is characterized by: