JPH11165549A - Four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a free running distance by providing a friction transmission route having friction torque set smaller than friction torque generated between a road surface and a second driving wheel and a direct transmission route bypassing the route to be freely switched and selected in the transmission system of the second driving wheel branched by the transmission system of a first driving wheel. SOLUTION: A friction transmission device 19 is provided with the inner tooth 17a of a transmission gear 17, a friction plate 19a stacked by being engaged with a spline cut in an output shaft 18 and a spring 19b adhered and engaged with the friction plate 19a. The friction torque of the friction transmission device 19 is set by the urging force selection of the spring 19b so as to be smaller than friction torque generated between a road surface and a front wheel. A sleeve 20 is selectively switched to a friction transmission mode where the sleeve is positioned in the front more than the inner tooth 17a and a direct transmission mode where the same is positioned in a rear side to enter the boss part of the transmission gear 17 and a clutch tooth 20a is engaged with the inner tooth 17a. Thus, a free running distance until a vehicle makes a complete stop is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel drive vehicle such as a tractor having a transmission system to a second drive wheel (front wheel) branched from a transmission system of a first drive wheel (rear wheel) having a braking device. About.

[0002]

2. Description of the Related Art A four-wheel drive type can easily obtain a large propulsion force compared to a two-wheel drive type, and exerts its power when traveling uphill or when work such as wet fields requires horsepower. However,
Because it is a four-wheel drive type, when driving on flat roads such as asphalt with low road resistance, it is useless to continue driving the front wheels that require propulsion as described above, and the turning radius during work is small. To avoid this, the peripheral speed of the front wheel is set to be slightly faster than that of the rear wheel. . Therefore, when traveling on the road, it is general that the operator performs a cutting operation on the transmission system of the front wheels and travels in a two-wheel drive state in which only the rear wheels are driven.

[0003]

However, when the rear wheels are braked while traveling on the road in a two-wheel drive state, frictional resistance against the road surface occurs only on the rear wheels. If the rear wheel is applied, the braking force of the rear wheel extends to the front wheel, causing frictional resistance on all four wheels. However, compared to this case, there is a problem that the idle running distance until the vehicle completely stops is longer.

[0004]

The present invention uses the following means in order to solve the above problems. First, the means according to the first aspect of the present invention is based on the fact that friction generated between the road surface and the second drive wheel is provided in the transmission system to the second drive wheel branched from the transmission system of the first drive wheel having the braking device. A friction transmission path set to a friction torque smaller than the torque and a direct connection transmission path bypassing the path are provided so as to be selectively switched.

A second aspect of the present invention is to provide a transmission system for a second drive wheel branched from a transmission system for a first drive wheel having a braking device. A friction transmission path that is set so as to cause slippage when it is received, and a direct connection transmission path that bypasses the friction transmission path are provided so as to be selectively switched.

A third aspect of the present invention is directed to a first drive system when the braking device is actuated in a transmission system to a second drive wheel branched from a transmission system of a first drive wheel having a braking device. A friction transmission path set to a friction torque capable of transmitting a braking torque acting on a wheel as a braking torque of a second drive wheel, and a direct-connection transmission path bypassing the path are provided so as to be selectively switched.

According to a fourth aspect of the present invention, a transmission gear, which is branched and driven from a transmission system of a first driving wheel having a braking device, is loosely disposed on an output shaft for a second driving wheel. Between the output shaft and the transmission gear, a friction transmission device set so as to cause slippage when the second drive wheel receives road surface resistance, and a direct-coupled transmission device are juxtaposed and provided to be selectively switched. is there.

According to a fifth aspect of the present invention, a transmission system for a second driving wheel branched from a transmission system of a first driving wheel having a braking device is provided with a road surface resistance when the second driving wheel travels. A friction transmission device is provided which can be changed between a state of a small friction torque in which slippage occurs when received and a state of a large friction torque in which slippage does not occur.

[0009] In the invention according to the first, second, third, fourth or fifth aspect, the means adopted by the invention according to the sixth aspect is that the second drive wheel is a steering wheel.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a side view of a tractor which is a four-wheel drive vehicle adopting the structure of the present invention, FIG. 2 is a side cross-sectional view of a front wheel power take-out part in a four-wheel drive vehicle, and FIG. FIG. 4 is a side sectional view showing another embodiment.

First, the general structure of the tractor shown in FIG. 1 will be described. An engine E, a battery, and the like are mounted on an engine frame 1, covered with a hood 2, a dashboard 3 is provided at a rear end of the bonnet 2, and a handle 4 is protruded above the dashboard 3. I have. The clutch housing 5 is disposed behind the lower end of the dashboard 3 and its front end is connected to the rear end of the engine E.
The rear end is connected to the transmission case 6. A rear wheel differential mechanism is provided in the transmission case 6, and rear axles 7 are extended on both left and right sides, and rear wheels 8.8, which are always driving wheels, are attached to respective left and right outer ends. The rear wheels 8.8 are provided with braking devices BL and BR as usual, and a braking force is applied to the rear wheels 8.8 by an operator depressing a brake pedal arranged on the floor of the driving unit. It works to.

From the clutch housing 5 to the transmission case 6, a power transmission mechanism from the output shaft of the engine E to the rear wheel differential mechanism is provided therein, and a front wheel power take-out case 9 is provided at the lower end of the clutch housing 5. And a transmission mechanism that branches off from a power transmission mechanism for the rear wheels in the clutch housing 5 and extracts power for driving the front wheels is provided internally. An output shaft 18 extends forward of the front wheel power take-out case 9, and a front end of the output shaft 18 is connected via a universal joint 10 to a front wheel differential mechanism in a front axle case 11 disposed below the engine frame 1. Front axles 11a are protruded from left and right sides of the front axle case 11, and front wheels 12, 12 which are steered wheels are disposed at respective outer ends thereof. Front wheel 12
12 is steered by operating the steering wheel 4. A lever or a switch is provided in the dashboard, near the seat, or the like, which can select one of two types of four-wheel drive modes described later.

In the above-described four-wheel drive vehicle, the present invention relates to the configuration of the transmission mechanism in the front wheel power take-out case 9. This embodiment will be described with reference to FIG. In the clutch housing 5, a front wheel power take-out gear 14 is disposed on a rear wheel drive transmission shaft (a transmission shaft connected to a rear wheel differential mechanism) 13, and the front wheel power take-out gear 14 is provided with a front wheel power take-out gear. It meshes with a first counter gear 16a that is rotatably fitted on a counter shaft 15 provided horizontally on the upper part in the case 9. An output shaft 18 for the front wheel 12 is supported in the front wheel power take-out case 9, and the front end thereof is connected to the universal joint 10. A transmission gear 17 is freely rotatably fitted to the output shaft 18 and meshes with a second counter gear 16b rotating on the counter shaft 15 integrally with the first counter gear 16a.

A boss portion extends from one side surface of the transmission gear 17, and internal teeth 17a are formed on an inner peripheral surface of the boss portion.
In the boss portion, a friction transmission device 19 is interposed between the output shaft 18 and the internal teeth 17a. In this embodiment, the friction transmission 19 is provided with internal teeth 17 a of the transmission gear 17.
And a plurality of friction plates 19a engaged and superimposed on respective splines engraved on the outer peripheral surface of the output shaft 18 so as to be relatively non-rotatable.
And a spring 19b for bringing the friction plates 19a into close contact with each other and constantly engaging them with a predetermined urging force. Here, a four-wheel drive vehicle such as a tractor is attached to the front wheels 12 with respect to the rear wheels 8 in consideration of turning performance during work traveling.
Is set so as to be slightly faster, so that when traveling on a flat road surface in the four-wheel drive state, a friction torque is generated between the road surface and the front wheels 12 due to the peripheral speed difference. The friction torque of the friction transmission device 19 according to the present invention is
The friction torque is set by selecting the biasing force
The friction torque is set to be smaller than the friction torque generated between the asphalt road surface and the front wheels 12.

In front of the transmission gear 17, a sleeve 20, which is relatively non-rotatable and spline-engaged slidably in the axial direction, is provided on the output shaft 18,
A rotary arm 22 is pivotally supported on the outer wall of the front wheel power take-out case 9 and is linked to the four-wheel drive mode selection lever and the like. The sleeve 20 is located in front (left side in the drawing) of the internal teeth 17a shown in FIG. 2 and in the boss portion of the transmission gear 17 located rearward (right in the drawing) of the position shown in FIG. The mode can be selectively switched to a direct drive mode in which the teeth 20a mesh with the internal teeth 17a.
A detent spring 23a and a detent ball 23b for positioning the mode of the sleeve 20 are fitted inside the output shaft 18. When the sleeve 20 is in the direct connection interlock mode, the transmission gear 17 is directly connected to the output shaft 18 and
Is rotated in synchronization with the rotation of the transmission shaft 13 to enter a four-wheel drive state.

The sleeve 20 is operated in a friction transmission mode by an operator when traveling on a flat road surface such as asphalt. When the vehicle runs in the four-wheel drive state, the front wheels 12 are dragged by the road surface resistance due to the peripheral speed difference between the front and rear wheels, and a friction torque is generated between the front wheels 12 and the road surface.
In the present invention, slippage occurs in the friction transmission device 19 set to a friction torque smaller than this friction torque, so that the front wheel 12 is not dragged as described above.
It is no different from running in two-wheel drive. Similarly, when the vehicle turns, the front wheels 12 are not dragged, so that a small turn is possible. Moreover, in the present invention, the power to the front wheel 12 is not cut off,
When the rear wheel 8 is braked, the braking force is applied to the front wheels 12 so that frictional resistance can be generated in all four wheels, and until the vehicle is completely stopped. Can be reduced as compared with the case where the rear wheels are braked in the two-wheel drive state.

FIG. 3 shows another embodiment of a transmission mechanism for taking out front wheel power in a four-wheel drive vehicle, in which the output is provided at the rear of the transmission gear 17 meshing with the counter gear 16 (on the side opposite to the sleeve 20). A friction transmission 19 is interposed between the shaft 18. At the front of the transmission gear 17, the internal teeth 1
Clutch gear 1 capable of meshing with sleeve 20 in place of 7a
7b is formed to constitute a direct-coupled transmission. Sleeve 2
0 is switched between a friction transmission mode in which the clutch gear 17b is not engaged and a direct connection transmission mode in which the transmission gear 17 is directly connected to the output shaft 18 by engaging with the clutch gear 17b. In the friction transmission mode, the transmission gear 17 and the output shaft 18 are connected to each other with a predetermined friction torque via the friction transmission device 19, and the effect in this case is described in FIG. Same as the example.

In the first and second embodiments of the present invention, the front wheel 1
In the transmission system to the second embodiment, a direct coupling transmission is provided in addition to the friction transmission 19, but in the third embodiment of the present invention shown in FIG. 4, one friction transmission 19 'has the function of the direct coupling transmission. It is configured as follows. That is, the friction transmission device 19 ′ includes a plurality of friction plates 19 a which are engaged with and overlapped with the clutch cylinder 19 c fixedly installed on the output shaft 18 and the transmission gear 17 loosely fitted on the output shaft 18. , Spring chamber 1 formed in clutch cylinder 19c
9e, a spring 19b disposed in the spring chamber 19e,
The hydraulically actuated multi-plate clutch includes a piston 19c that presses the friction plate 19a by receiving the urging force of the spring 19b. The friction torque of the friction transmission device 19 'is set to the same value as in the first and second embodiments by the spring 19b, and the friction transmission device 19' is always engaged in the state of the friction torque.

Further, the spring chamber 19e in the clutch cylinder 19c can be supplied with oil from an oil pump 24 via a mode switching valve 25. 26 is a piston 19c
This is a relief valve for setting a hydraulic pressure acting on the frictional transmission device 19 '. By supplying this hydraulic pressure, a friction torque larger than the friction torque is set in the friction transmission device 19'. As the mode switching valve 25, a two-position switching valve of an electromagnetic solenoid switching type is used, and when a four-wheel drive mode selection lever (not shown) provided in the driving unit is set to a friction transmission mode, the position becomes the illustrated position and the oil in the spring chamber 19e is set. And friction transmission 1
9 'is set to a state in which a small friction torque is set only by the spring 19b, and when the mode is switched to the direct coupling transmission mode, it shifts to the right position on the drawing and refuels the spring chamber 19e. The large friction torque due to the pressure is automatically changed to the set state.

In the third embodiment, the spring 19b and the mode switching valve 25 are omitted from the clutch cylinder 19c, and a variable relief type is used for the relief valve 26. When the friction lever is set in the friction transmission mode, the urging force of the relief spring is reduced and the piston 19c is moved.
, The hydraulic pressure applied to the friction transmission 19 '
Is set to a state of small friction torque, and when the mode is switched to the direct connection transmission mode, the urging force of the relief spring is increased to increase the piston 19c.
The hydraulic pressure applied to the friction transmission 19 'is increased.
May be configured to be changed to a state of large friction torque.

The friction transmissions 19 and 19 'may be of a viscous clutch type or a cone clutch type in addition to the friction multi-plate clutch type shown in the embodiment.
The direct-coupled transmission shown in the second embodiment may be a pawl clutch type or a ball clutch type in addition to the meshing clutch type.

[0022]

As described above, the present invention has the following advantages. First, according to the first to third aspects, the operator can arbitrarily select any one of the friction transmission path and the direct coupling transmission path in the transmission system of the second drive wheel,
When a direct-connection transmission path is selected during work traveling, the vehicle enters a four-wheel drive state and can travel with a strong propulsive force. Further, when the friction transmission path is selected during traveling on the road, when the second drive wheel receives a road surface resistance and generates a friction torque with the road surface, the friction set to a smaller friction torque than the friction torque is generated. Since slippage occurs in the transmission path, abnormal wear of the tire can be reduced as much as possible without dragging the second drive wheel as in two-wheel drive travel. In addition, since the power to the second drive wheel is constantly transmitted via the friction transmission path, when braking the first drive wheel, the braking force reaches the second drive wheel, and all four wheels are braked. , Frictional resistance can be generated, and the idle running distance until the vehicle completely stops can be reduced as compared with the case where the rear wheels are braked in the two-wheel drive state.

On the other hand, with the construction as described in claim 4, the vehicle can travel with a strong propulsive force which becomes a four-wheel drive state when the transmission gear and the output shaft are directly connected by the direct transmission during the work traveling. it can. Further, when traveling on the road, when the transmission gear and the output shaft are coupled via a friction transmission device, when the second drive wheel receives road surface resistance and generates friction torque with the road surface, the frictional torque is smaller than the friction torque. Since slippage occurs in the friction transmission path set to a small friction torque, abnormal wear of the tire can be reduced as much as possible without dragging the second drive wheel as in the case of two-wheel drive traveling.
In addition, since the power to the second drive wheel is constantly transmitted via the friction transmission, when the first drive wheel is braked, the braking force reaches the second drive wheel and is applied to all four wheels. Friction resistance can be generated, and the idle running distance until the vehicle completely stops can be reduced as compared with the case where the rear wheels are braked in the two-wheel drive state. In addition, since the direct-coupled transmission and the friction transmission are arranged side by side on the output shaft, the switching section can be shared, and the mechanism can be simplified and downsized.

According to the fifth aspect of the present invention, when the friction torque of the friction transmission device is set to a large friction torque state at the time of work traveling, a four-wheel drive state is established and the vehicle can travel with a strong propulsive force. Also, when traveling on the road, the friction torque of the friction transmission device is set to a small friction torque state, and when the two-wheel drive wheels receive the road surface resistance and the friction torque is generated with the road surface, slippage occurs in the friction transmission device. As in the case of two-wheel drive traveling, abnormal wear of the tire can be reduced as much as possible without dragging the second drive wheel.
Moreover, since the power to the second drive wheel is constantly transmitted through the friction transmission set to the small friction torque, when the first drive wheel is braked, the braking force reaches the second drive wheel. As a result, friction resistance can be generated on all four wheels, and the idle running distance until the vehicle completely stops can be reduced as compared with the case where the rear wheels are braked in the two-wheel drive state. And
Since this single friction transmission device can make the four-wheel drive state appear, the mechanism can be simplified and made compact.

Further, in the four-wheel drive vehicle according to any one of the first to fifth aspects, when the vehicle turns while traveling on a road, the vehicle according to the sixth aspect has the configuration described above.
Since the second drive wheel is not dragged, it is possible to make a sharp turn without breaking the road.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor that is a four-wheel drive vehicle that employs the configuration of the present invention.

FIG. 2 is a side sectional view of a front wheel power take-out portion in a four-wheel drive vehicle.

FIG. 3 is a side sectional view showing another embodiment.

FIG. 4 is a side sectional view showing another embodiment.

[Explanation of symbols]

 Reference Signs List 8 rear wheel (first driving wheel) 9 front wheel take-out case 12 front wheel (second driving wheel / steering wheel) 17 transmission gear 17a internal teeth 17b clutch gear 18 output shaft 19 friction transmission device 20 sleeve

Claims (6)

[Claims] A transmission system for a second drive wheel branched from a transmission system for a first drive wheel having a braking device is set to a friction torque smaller than a friction torque generated between a road surface and a second drive wheel. A four-wheel-drive vehicle, wherein the selected friction transmission path and a directly-connected transmission path bypassing the path are provided so as to be selectively switched. 2. A transmission system for a second driving wheel branched from a transmission system of a first driving wheel having a braking device is set so that slippage occurs when the second driving wheel receives road surface resistance during traveling. A four-wheel-drive vehicle, wherein the friction transmission path and a direct-connection transmission path bypassing the path are provided so as to be selectively switched. 3. A transmission system for a second driving wheel branched from a transmission system for a first driving wheel having a braking device, the braking torque acting on the first driving wheel when the braking device is activated being applied to a second driving wheel. A four-wheel drive vehicle characterized in that a friction transmission path set to a friction torque that can be transmitted as a braking torque of a drive wheel and a direct transmission path that bypasses the friction transmission path are switchably provided. 4. A transmission gear branched and driven from a transmission system of a first drive wheel having a braking device is loosely disposed on an output shaft for a second drive wheel, and a transmission gear is connected to the output shaft and the transmission gear. A four-wheel drive vehicle comprising a friction transmission device set so that slippage occurs when the second drive wheel receives road surface resistance, and a direct-coupled transmission device arranged side by side so as to be selectively switched. 5. A small friction torque, in which slippage occurs when the second drive wheel receives road surface resistance during traveling, in a transmission system to a second drive wheel branched from a transmission system of the first drive wheel having a braking device. A four-wheel drive vehicle provided with a friction transmission device that can be changed between a state and a state of large friction torque that does not cause slippage. 6. The four-wheel drive vehicle according to claim 1, wherein the second drive wheel is a steering wheel.