JPH04208645A - Four wheel drive car - Google Patents

Abstract

PURPOSE:To automatically change over from a four wheel drive state to a two wheel drive state and vice versa and smoothly carry out turning and slope driving by providing a lock device to fix a one-way clutch always in the transmission state and others as well as providing the one-way clutch in a front wheel drive system. CONSTITUTION:Rotational motive power of an engine is transmitted from a front wheel drive primary shaft 37 to a front wheel drive secondary shaft 49 through a one-way clutch 50. At this time, if the front wheel drive primary shaft 37 is rotated, a drive cam 51 is rotated and a center cam 53 is rotated. Whereupon, a frictional force is generated between a resistance arm 57 and a brake shoe 60, and a resistance force by this friction resists against a resiliency of a return spring 56 and moves a driven cam 53 forward. Consequently, tooth 57 of the center cam 53 and tooth 58 of the driven cam 52 are engaged with each other, and the motive power is transmitted. Accordingly, at the time of normal driving such as straight driving and others, the one-way clutch comes to be on and a car comes to be in a four wheel drive state. Subsequently, at the time of turning and others, an inclined face of the center cam 53 is separated from an inclined face of the drive cam 51, and the car come to be a two wheel drive state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power transmission system in a four-wheel drive vehicle such as a tractor.

[Prior Art] When turning a four-wheel drive tractor in a field, if both the front and rear wheels are kept in drive, just like when moving straight,
The rotation of the front wheels cannot follow the rotation of the rear wheels, resulting in a large turning radius. Therefore, a high/low speed switching device is installed to arbitrarily or automatically switch the transmission state of the front wheel drive system between high speed transmission and low speed transmission, so that the front wheel drive system is in the low speed transmission state when driving straight, and the front wheel drive system is in the high speed transmission state when turning. By this,
Tractors are designed to increase the circumferential speed of the front wheels when turning, and an automatic switching mechanism is installed in the front wheel transmission system that cuts off power transmission when the speed of the front wheels is higher than a certain level than the speed of the rear wheels. 2. Description of the Related Art Tractors have been proposed that are configured to automatically switch from a wheel drive state to a rear wheel drive state so that the rotation of the front wheels can follow the rotation of the rear wheels when turning.

[Problems to be Solved by the Invention] However, although the tractor equipped with the high-low speed switching device can reduce the turning radius of the machine body, there are problems in that a shock occurs when the high-low speed switching device switches; Alternatively, there is a problem in that when the high/low speed switching device is switched to the high speed side, the front wheels whose circumferential speed has increased pull the rear wheels and roughen the ground. Furthermore, although tractors equipped with the automatic switching mechanism can turn well in fields with relatively hard ground, there is a problem in that the front wheels may slip in fields with soft ground.

[Means for Solving the Problems] In order to solve the above problems, the present invention has the following configuration.

That is, the four-wheel drive vehicle according to the present invention is a four-wheel drive vehicle in which a front wheel drive system that drives the front wheels is transmitted by branching from a rear wheel drive system that drives the rear wheels, and in which the front wheel drive system that drives the front wheels is transmitted. , a one-way clutch is provided that can transmit power only in one direction from the driving side to the driven side, and that cuts off the transmission from the driving side to the driven side when the rotational speed of the driven side is higher than the rotational speed of the driving side by a certain amount. The present invention is also characterized in that it includes a locking device that always fixes the one-way clutch in a transmission state, and an actuator that operates the locking device.

[Function 1: When the rotational speed of the driven side is faster than the rotational speed of the driving side by a certain amount, such as when turning, the one-way clutch becomes non-transmitting and power transmission to the front wheels is cut off, so the rotation of the front wheels is reduced. can smoothly follow the rotation of the rear wheels, allowing for good turning. In soft fields that require a large propulsion force, by fixing the one-way clutch in the transmission state with a locking device, the four-wheel drive state can be maintained and smooth running can be achieved. In addition, since the locking device is operated by a suitable actuator such as a motor,
The operation of the locking device is reliable.

[Example] The embodiments shown in the drawings will be described below.

Fig. 1 is a side view of an agricultural tractor, which is an example of a four-wheel drive vehicle. is mounted, a clutch housing 6 is fixed to the rear of the clutch housing 6, and a transmission case 5 is further provided behind the clutch housing 6.

A universal joint 1 is installed between an output shaft 8 extending rearward from the rear of the housing 6 and an input shaft 10 extending forward from the transmission case 5.
1 are detachably connected. The protrusions of the output shaft 8 and input shaft 10 and the upper and lateral sides of the universal joint 11 are covered with a saddle-shaped housing 9 that connects the clutch housing 6 and the transmission case 5.

Next, mission case 5 shown in Figures 3 and 4.
Explain the structure inside.

A gear I2 integrally provided at the rear end of the input shaft 1O is always engaged with an input gear 15 attached to the front end of the speed change shaft 14. The transmission shaft 14 has an L speed gear 16, an R speed gear 17, a second speed gear 18, and a third speed gear 1 having a large diameter gear portion 19a and a small diameter gear portion 19b as main transmission drive gears.
9 are rotatably fitted into each other, and on the other hand, a main transmission driven gear 21 having a large diameter gear part 21a, a medium diameter gear part 21b and a small diameter gear part 21c is rotatably attached to the drive shaft 20 facing the transmission shaft 14. The first gear 16 is always engaged with the large diameter gear part 21a of the driven gear, and the second
The speed gear 18 is always meshed with the medium diameter gear portion 21b of the driven gear, and the large diameter portion 19a of the third speed gear is in mesh with the small diameter gear portion 21b of the driven gear.
It is always engaged with c.

Further, the R speed gear 17 meshes with the medium diameter portion 21b of the driven gear via the pack idle gear 22.

■A shifter 24 is located between the speed gear 16 and the R speed gear 17.
A shifter 25 is located between the second gear 18 and the third gear 19.
All of them are spline-fitted to the transmission shaft 14, and these chics 24 and 25 are moved in the axial direction to selectively spline-fit them to the main transmission drive gears 16 to 19. The main speed change is performed by transmission-locking the speed change drive gear and the speed change shaft 14, that is, 1
When the transmission of the transmission gear 16 is integrally stopped, the front When the transmission is stopped, it becomes reverse speed.

In addition to the main transmission driven gear 21, an auxiliary transmission low speed gear 27 having a large diameter gear portion 27a and a small diameter gear portion 27b is rotatably fitted into the drive shaft 20 at a fixed position. Low speed gear 27 and main shift driven gear 2
An auxiliary transmission gear 29 is provided at the interval 1 so as to be slidable in the axial direction.

Note that the large diameter gear portion 27a of the low speed gear is always meshed with the small diameter gear portion 19b of the third speed gear. When the auxiliary transmission gear 29 is spline-fitted to the main transmission driven gear 21, power is directly transmitted from the main transmission driven gear 21 to the auxiliary transmission gear 29, and high-speed transmission is performed.

Furthermore, when the auxiliary transmission gear 29 is spline-fitted to the low speed gear 27, power is transmitted from the main transmission driven gear 21 to the auxiliary transmission gear 29 via the 3rd speed gear 29 and the low speed gear 27.
Low speed transmission is performed.

Further, a fixed shaft 31 is provided parallel to the drive shaft 20, and a creep gear 32 can be rotatably attached to the fixed shaft. When the creep gear 32 is installed with the auxiliary transmission gear 29 in the neutral position, its large diameter portion 32a is connected to the small diameter 112 of the low speed gear.
7b, and its small diameter portion 32b meshes with the sub-transmission gear 29, making it possible to further reduce the speed compared to the low-speed transmission state. Note that this creep transmission mechanism does not necessarily need to be provided, and may be provided as desired.

The rotational power of the drive shirt 20 is transmitted to the rear differential device 34, and from the rear differential device to the left and right rear wheels 3, 3 via a rear axle (not shown) or the like. Furthermore, a front wheel power extraction gear 35 is attached to the drive shaft 20.

The rotational power of the drive shaft 20 is transmitted from this power take-off gear 35 to the rear end of the front wheel drive-next shaft 37 via a counter gear 36 that rotatably fits into the rear end of the third speed gear 19. The power is also transmitted to the front wheel power intake gear 38.

Further, the rear end portion of the speed change shaft 14 is connected to a PTO speed change shaft 40. This PTO transmission shaft 40 has a first gear having a different number of teeth.
, second and third drive gears 41, 42 and 43 are integrally provided. PTO supported parallel to PTO gear shift shaft 40
The shaft 45 has a first. A second driven gear 46 that constantly meshes with the driving gear 41 is non-rotatably fitted in a fixed position, and a second driven gear 47 having a large diameter gear portion 47a and a small diameter gear portion 47b is slidable in the axial direction. and is provided so as to be non-rotatable. Claw 46a of first driven gear 46 and second driven gear 4
When the pawl 470 of No. 7 is engaged, the speed is low; when the second drive gear 42 and the large diameter gear portion 47a of the second slave gear are engaged, the speed is medium;
When the third drive gear 43 and the small diameter gear portion 47b of the second driven gear are meshed, high speed is achieved, and the transmission ratio can be selectively switched to three stages. In addition, PTO
The rear end of the shaft 45 protrudes from the back of the body to the outside of the case.

A front wheel drive secondary shaft 49 is coaxially supported in front of the front wheel drive secondary shaft 37, and a one-way clutch 50 is provided at the connection portion of both shafts 37 and 49. The one-way clutch 50 is rotatable between a drive cam 51, which is integrally attached to the front end of the secondary shaft 37, a driven cam 52, which is integrally attached to the rear end of the secondary shaft 49, and both cams 51 and 52. A center cam 53 that is movable back and forth, a rotating drum 54 that accommodates each of the cams, and a lock sleeve 55 for a lock device. The resistance arm 57 in FIG. 1 is a plate-shaped resistance arm extending rearward from the outer peripheral surface of the center cam 53, which is provided with a return spring 56 etc. that biases the center cam 53 toward the drive cam 51. It is inserted through a through hole 58. Also, 60 is a brake shoe,
As shown in FIG. 5, a spring 61 provided on the outer periphery of the
The arm 57 is biased in a direction that provides resistance.

A center cam 53 is provided on the outer periphery of the front end surface of the drive cam 51.
a convex portion 63 having an inclined surface 63a that transmits rotational power to;
Concave portions 64 that do not transmit rotational power are provided alternately, and on the other hand, an inclined surface 6 that receives rotational power from the drive cam 51 is also provided on the outer periphery of the rear end surface of the center cam 53 opposite to the recessed portions 64.
Recessed portions 65 having 5a and flat portions 66 not involved in power transmission are alternately provided. The convex portion 63 of the drive cam 51 and the concave portion 65 of the center cam 53 also have inclined surfaces 63b and 65b that transmit rotational power in the reverse rotation direction from the center cam 53 to the drive cam 51. Further, teeth 67 having a trapezoidal cross section are provided on the outer periphery of the opposing surfaces of the center cam 53 and the driven cam 52.

68, .
The transmission is stopped when the center cam 53 moves slightly rearward and disengages.

When the driven cam 52 rotates, the front and rear wheels 2, 2, 3.
When the driven cam 52 is stopped, a two-wheel drive state occurs where only the rear wheels 3 and 3 are driven. Note that the pressure angle θ1 of the transmission part between the drive cam 51 and the center cam 53 is smaller than that of the center cam 53.
The pressure angle θ2 of the transmission portion of the driven cam 52 is greater than the pressure angle θ2 (θ1>θ2).

The lock sleeve 54 is a cylindrical portion 51a of the drive cam 51.
It is slidably fitted to the outer periphery of the lock sleeve 5
A lock pin 70 protruding from the front surface of 4. ... is a through hole 71. bored in the hub 51b of the drive cam 51.・・・
・Protrudes forward through the center cam 5.
It faces the rear of 3. The lock sleeve 54 is provided with an annular engagement groove 72, and the distal end of the arm 73a of the lock operating member 73 attached to the arm support shaft 74 is engaged with the engagement groove 72. The lock operation member 73 is slidably provided on the arm support shaft 74.
The lock sleeve 5 is opened by the operation member 73 using the operating means described later.
4 forward, the lock pin 70. The center cam 53 is pushed forward by the center cam teeth 67,... of the driven cam. ... and now they are constantly engaged.

Fixed in four-wheel drive.

In this embodiment, a motor 75 is used as the actuating means for the locking device. This motor 75 is provided in front of the -L section of the mission case 5, and a worm gear 77 provided in front of the arm support shaft 72 meshes with a pinion 76 attached to its output shaft.
A male threaded portion 80 formed on the extension shaft 79 of the arm support shaft 72 is screwed into the female threaded portion 78 of the arm support shaft 72 . The locking operation member 73 is biased toward the extension shaft 79 by the spring 81, and the two parts 73 and 79 are in abutment against each other, and the axial pressing force is transmitted from the extension shaft 79 to the locking operation member 73. , rotational force is not transmitted. When the motor 75 is rotated in a predetermined direction, the worm gear 77 that meshes with the pinion 76 rotates in a fixed direction, and the extension shaft 7
9 moves forward. Along with this, spring 81
The lock operation member 73 also moves forward due to the repulsive force of
As described above, the one-way clutch 50 is fixed in the "on" position, and the four-wheel drive state is maintained. From this state, the motor 75
When the lock operation member 73 is rotated in the opposite direction, the extension shaft 79 presses the lock operation member 73 backward, and the lock operation member 7
3 is released, and the one-way clutch 50 becomes free.

In FIG. 1, 85 is a steering handle, 86 is a fender, and 87 is a front axle housing. A front wheel differential device (not shown) is provided inside the front axle housing 87, and the rotational power of the front wheel drive secondary shaft 49 is transmitted to the front wheel differential device via a universal joint 88. Driving shaft mounted horizontally (not shown)
The front wheels 2, 2 are rotationally driven through.

Next, the operation of the power transmission system of this tractor I will be explained.

In this power transmission system, the rotational power of the engine 4 is
After the main transmission and the auxiliary transmission perform the main shift and the auxiliary shift, the transmission is transmitted to the drive shaft 20 of the rear wheel drive system, and is branched from this drive shaft 20 to the front wheel drive - next shaft 37 of the front wheel drive system. It is further transmitted from the front wheel drive secondary shaft 37 to the front wheel drive secondary shaft 49 via the one-way clutch 50. This one-way clutch 50 is capable of transmitting power only in one direction from the secondary shaft 37 to the secondary shaft 49, and can be automatically switched on/off as appropriate depending on the running resistance of the front wheels 2.2. There is.

When the engine is stopped or when the main transmission or sub-transmission is in the neutral position, no power is transmitted to either the rear wheel drive system or the front wheel drive system, and at this time the one-way clutch 50
As shown in FIG. 6(a), the return spring 5
6, the center cam 53 is pressed against the drive cam 51 side, and the center cam 53 and the driven cam 52 are separated from each other.

When the front wheel drive-following shaft 37 rotates, the drive cam 51 rotates and the center cam 53 also rotates, but as the center cam rotates, a frictional force is generated between the resistance arm 57 and the brake shoe 60, and this The resistance force due to friction moves the center cam 53 forward against the repulsive force of the return swing 56, and the teeth 57. of the center cam 53 move as shown in FIG. 6(b). ... and the teeth 58 of the driven cam 52, ... mesh with each other, and power is also transmitted from the center cam 53 to the driven cam 52.

That is, during normal driving, such as when driving straight, the one-way clutch 50 is turned on, resulting in a four-wheel drive state.

When turning, etc., the front wheels 2.2 try to rotate quickly due to push by the aircraft body, so that the driven cam 52 causes the center cam 53 to rotate. As a result, as shown in FIG. 6(c), the inclined surface 65a of the center cam 53 separates from the inclined surface 63a of the drive cam 51, resulting in a two-wheel drive state.

Furthermore, the pressing action of the return spring 56 and the tooth 58
, -... pushes the center cam 53 back toward the drive cam 51, and as shown in FIG. 6(d), the center cam 53 and the driven cam 52 are also disengaged, and each cam
1, 52, and 53 are each free. In this state, the front wheels 2, 2 can overrun the rear wheels 3, 3, so that turning can be performed smoothly. center cam 53
When the rotational speed of the drive cam 51 becomes lower than the rotational speed of the drive cam 51, the inclined surfaces 63a and 65a of the two come into contact again, and the drive cam 51 and the center cam 53 are connected by transmission.
Accordingly, the center cam 53 moves forward, and the center cam 53 and the driven cam 52 are also transmission-coupled, resulting in a four-wheel drive state. If the front wheels 2.2 are still being pushed by the aircraft at this point, the same operation as described in L is performed to return to the two-wheel drive state. In other words, during overrun, the
), (c), and (d) are repeated in order, and when the turning is completed and the rotational speed of the front wheels 2.2 falls below a certain level, the four-wheel drive state is automatically fixed.

In addition, in fields where the ground is soft, even if two-wheel drive is activated during a turn, the front wheels 2.2 will not rotate sufficiently due to road resistance, and the rear wheels 3.3 will go to sleep, but due to slipping, When the moving speed of the aircraft decreases, the number of rotations of the drive cam 51 becomes higher than the number of rotations of the driven cam 52, and the four-wheel drive state is immediately restored, making it possible to easily escape from the slip.

The above operation also applies when the aircraft moves backwards. In that case, power is transmitted from the drive cam 51 to the center cam 53 through the inclined surface 63b and the inclined surface 65b, and the surfaces of the teeth 57 and 58 on the opposite side. Transmission between the center cam 53 and the driven cam 52 is performed through the center cam 53 and the driven cam 52.

In addition, this one-way clutch 50 is effective even on slopes, etc. 1. For example, when the rotation speed of the front wheels 2.2 is higher than the speed at which the front wheels rotate due to the forced driving force on a downhill slope, it becomes a two-wheel drive state, and vice versa. When the rear wheels 3.3 slip and the rotational speed of the front wheels 2.2 drops to a predetermined rotational speed, the four-wheel drive state is restored to improve the propulsion force. ' Thus, by providing the one-way clutch 50, the vehicle can be automatically switched between the four-wheel drive state and the two-wheel drive state as appropriate, and it is possible to smoothly perform turns and running on slopes. Depends on the type of work equipment to be installed! ! When a large amount of propulsion is required, or when engine braking is required for the front wheels, a locking device can be used to lock the one-way club.
The function of the vehicle 50 can be fixed to a four-wheel drive state.

Since this locking device is driven by a motor 75, its operation is reliable. Note that as a driving means for the locking device, a device other than a motor, such as a solenoid, may be used.

[Effects of the Invention] As is clear from the above description, the four-wheel drive vehicle according to the present invention can turn smoothly and easily by automatically switching between the four-wheel drive state and the two-wheel drive state using the one-way clutch. This can be done in a small radius, and also eliminates the problem of shocks occurring when the front wheels switch between high and low speeds, which is the case with conventional vehicles. Additionally, a locking device is provided to keep the one-way clutch in the "on" state at all times and maintain the four-wheel drive state, so it can easily handle situations where large propulsive force is required.

[Brief explanation of the drawing]

Fig. 1 is a side view of an agricultural tractor which is an embodiment of a four-wheel drive vehicle according to the present invention, Fig. 2 is a front view of a transmission case, Fig. 3 is a sectional view taken along line A-A in Fig. The figure is a sectional view taken along the line B-B in FIG. 2, FIG. 5 is a sectional view taken along the line C-C in FIG. 4, and FIGS. . 1- Tractor (four-wheel drive vehicle), 2... Front wheels, 3.
...Rear wheel, 5...Mission case, 20...Drive shaft, 37...Front wheel drive - next shaft, 49...
Front wheel drive secondary shaft, 50... One-way clutch, 51
...Drive cam, 52...Driven cam, 53.
...Centa cam, 54...Lock sleeve, 73...
- Lock operation member, 75... motor (actuator).

Claims (1)

[Claims] (1) In a four-wheel drive vehicle in which the front wheel drive system that drives the front wheels is transmitted by branching from the rear wheel drive system that drives the rear wheels, there is a system in the front wheel drive system that runs from the driving side to the driven side. In addition to providing a one-way clutch that can transmit power only in the direction, and cuts off transmission from the driving side to the driven side when the rotational speed of the driven side is higher than the rotational speed of the driving side by a certain amount,
A four-wheel drive vehicle, comprising: a lock device that permanently fixes the one-way clutch in a transmission state; and an actuator that operates the lock device.