JP2005343419A - Front wheel rotation control device for four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front wheel rotation control device for a four-wheel drive vehicle capable of controlling a rotation speed to be in accordance with a theoretical speed ratio with the usage of a clutch having a simple structure and capable of transmitting torque whenever it is rotated in working. <P>SOLUTION: Power from an engine 2 is transmitted to a rear wheel 15 and a front wheel 14 steerable through the front wheel rotation control device 29, the front wheel rotation control device 29 is constituted by a first jointing device 51 and a second jointing device 52 in such a manner of capable of being selectively jointed, the first jointing device 51 can directly connect an input means from a rear wheel driving part and an output shaft 55 transmitting the power to the front wheel 14, the second jointing device 52 can vary the transmission torque between the input means and the output shaft 55, a rotational frequency detection means is arranged on the rear wheel driving part and a front wheel driving part respectively, a steering angle detection means is arranged on a steering mechanism, a transmission torque varying means is arranged on the second jointing device and is connected to a control part 64, the transmission torque varying means is controlled so that the speed change ratio of the front wheel and the rear wheel at the time of rotation is the speed change ratio in accordance with a steering angle, and the transmission torque varying means is constituted by an electromagnetic valve 63 and a hydraulic cylinder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for a front wheel rotation control device for a four-wheel drive vehicle, and more particularly to a technique for increasing the speed of a front wheel in proportion to the turning angle when a tractor or the like turns more than a set angle during work.

Conventionally, when turning in a four-wheel drive vehicle such as a tractor, the front wheel is turned off and the vehicle is turned by driving the rear two wheels so that the front wheel is not dragged at high speeds. When traveling at a low speed, there is a vehicle that turns while increasing the average peripheral speed of the front wheels to about twice that of the rear wheels so as not to roughen the farm scene.
Conventionally, when steering a four-wheel drive vehicle, as shown in FIG. 5, the turning radii R1, R2, R3, R4 of the front and rear wheels are different depending on the inner wheel difference. If the ratio of the running speed (actual speed ratio) does not match the running speed ratio (theoretical speed ratio) when both of them are turning without slipping, the front wheel slips and the turning radius increases. In the case of an agricultural tractor, there is a problem that the ground of the field is roughened by the slip.

Therefore, as shown in FIG. 6, a speed increasing mechanism 75 capable of shifting in two stages is interposed between a transmission 72 connected to the prime mover 71 and a front wheel differential 74 connected to the front axle 73, so that the front wheel 76 When the steering angle increases, the speed increasing mechanism 75 is shifted to the high speed side to prevent the slip. (For example, refer to Patent Document 1).
However, although the theoretical speed ratio increases steplessly as the steering angle of the front wheel increases, the actual speed ratio is stepwise as shown in FIG. Therefore, the slip prevention is incomplete.
Therefore, a technique in which a continuously variable transmission is disposed between the transmission and the front wheel differential so that the peripheral speed of the front wheels matches the above-described logical speed ratio (for example, see Patent Document 2), or a technique in which an electromagnetic powder clutch is disposed. (See, for example, Patent Document 3).
Japanese Patent Laid-Open No. 6-107011 Japanese Utility Model Publication No. 5-7526 JP 2001-315542 A

However, in the technique of Patent Document 2, when a turn is performed, a theoretical speed ratio is calculated from the steering angle, and a control signal based on the theoretical speed ratio is output to the continuously variable transmission so that the speed ratio is obtained. However, since the continuously variable transmission is configured to shift using HST, CVT, etc., it is difficult to incorporate in a limited space inside the mission case, and even if it is arranged outside the mission case, May interfere with other parts, and the arrangement position is limited. Furthermore, the number of parts increases, and an increase in cost is inevitable. Moreover, in the technique of Patent Document 3, a differential device is required, which increases the cost. When turning by driving the torque by transmitting torque to the front wheels, it can be close to the theoretical speed ratio, but when turning sharply with a small turning radius or turning downhill, the rotational force of the front wheels is greater than that of the engine. It exceeds the rotational force transmitted and driven, and is faster than the theoretical speed ratio.
In view of the above, the present invention uses a clutch capable of transmitting torque with a simple structure so as to achieve a turning speed that matches the theoretical speed ratio at any turning time during work.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, according to the first aspect, the power from the engine is transmitted to the rear wheels and the front wheels which can be steered via the front wheel rotation control device after shifting, and the front wheel rotation control device is transmitted to the first connection device and the second connection device. The first connecting device can transmit power from the rear wheel drive unit to the front wheel at a constant speed, and the second connecting device can transmit power by increasing speed from the rear wheel drive unit, Each of the one coupling device and the second coupling device is provided with a transmission torque changing means and connected to the control unit. The rear wheel driving unit and the front wheel driving unit each have a rotational speed detection unit, and the steering mechanism has a steering angle. Each of the detecting means is arranged and connected to the control unit, and the transmission torque changing means is controlled so that the gear ratio between the front wheels and the rear wheels at the time of turning becomes a gear ratio corresponding to the turning angle.

  According to a second aspect of the present invention, when the front wheel is driven by engine power during turning, the control unit sets the speed ratio between the front wheel and the rear wheel to a speed ratio corresponding to the turning angle. The transmission torque changing means of the two-coupled device is controlled.

  According to a third aspect of the present invention, the control unit, when turning, if the rotational force of the front wheels exceeds the rotational force that rotates the front wheels from the engine, the speed ratio of the front wheels and the rear wheels according to the turning angle. The transmission torque changing means of the first coupling device is controlled so that

As effects of the present invention, the following effects can be obtained.
By configuring as in claim 1, the front wheels are controlled to an appropriate turning speed during turning, and the front wheels can be prevented from slipping. Therefore, the turning radius caused by slip increases, tire wear is promoted, and in the case of an agricultural tractor, the field scene is not damaged by slip, and various adverse effects caused by slip can be prevented. .

  By controlling as in claim 2, when the front wheels are driven by the power from the engine, the transmission torque changing means of the second coupling device causes the front and rear wheels to move at a constant speed and the front wheels to the rear wheels. Thus, the power can be reliably transmitted up to about twice the set speed, and the speed can be changed according to the turning angle, so that the tires can be prevented from wearing or slipping.

  By controlling as in claim 3, when the vehicle turns suddenly with a small turning radius or when turning on a downhill, the rotational speed of the front wheels tends to be faster than the theoretical speed ratio. By actuating the means, it acts like an engine brake and can turn at a speed substantially close to the theoretical speed ratio, and tire wear and slip can be prevented.

Next, embodiments of the invention will be described.
The problems and means to be solved by the present invention are as described above. Next, an embodiment of the present invention shown in the accompanying drawings will be described. 1 is a side view of a tractor equipped with a front wheel rotation control device of the present invention, FIG. 2 is a skeleton diagram showing a drive transmission path, FIG. 3 is a control block diagram of the front wheel rotation control device of the present invention, and FIG. It is.

First, a schematic configuration of a tractor which is an embodiment provided with a front wheel rotation control device according to the present invention will be described.
In FIG. 1, an engine 2 is arranged on an engine frame 1, the engine 2 is covered with a bonnet 3, and a handle 5 serving as a steering means protrudes on a dashboard 4 at the rear of the bonnet 3. A seat 6 is disposed behind the handle 5, a main transmission lever 7 is disposed on the side of the seat 6, and a portion where the seat 6, the handle 5, and the like are disposed serves as a control unit 9. Yes.

A clutch housing 10 is connected to the rear portion of the engine 2, and the clutch housing 10 houses a main clutch 11, and a transmission case 13 is connected to the rear portion via a transmission case 12. A rear wheel 15 is supported on both sides of the vehicle 13 via a rear axle case. Further, a three-point link type work machine mounting device 16 for mounting various work machines is provided at the rear part of the mission case 13, and the PTO shaft projects from the rear surface of the mission case 13 to It can be driven.
A front wheel power take-out case 17 is provided at the front lower part of the transmission case 13, and power is transmitted to the front axle case 20 through the transmission shaft 19 in front of the front wheel power take-out case 17 and supported by the front axle case 20. The front wheel 14 can be driven.

Next, the drive transmission system of the tractor will be described with reference to FIG.
A forward / reverse switching mechanism 22 is provided at the rear of the output shaft of the engine 2 via the main clutch 11, a main transmission mechanism 23 is provided behind the forward / reverse switching mechanism 22, and a sub-transmission mechanism 24 is provided at the rear thereof. Further, a creep transmission mechanism 25 is provided at the rear portion thereof, and driving power after the transmission is transmitted to the drive shaft 30. On the other hand, the power of the output shaft of the engine 2 is also transmitted to the transmission shaft 32 in the pipe shaft 31, and the PTO shaft provided at the rear end of the transmission case 13 through the PTO transmission mechanism 26 from the rear end of the transmission shaft 32. 27 can transmit power.

A drive pinion 33 provided at the rear end of the drive shaft 30 to which the power after the shift is transmitted is transmitted to a ring gear provided in the rear wheel differential device 34, and the left and right differential yoke shafts 35L are transmitted from the rear wheel differential device 34. The rear wheels 15 and 15 are driven via the 35R and final speed reduction mechanisms 36 and 36.
Further, a front wheel drive gear 40 and a front wheel speed increasing gear 41 are fixed on the drive shaft 30, and the front wheel driving gear 40 or the front wheel speed increasing gear 41 is connected to the output shaft 55 via the front wheel rotation control device 29 of the present invention. The power is transmitted to the transmission shaft 19 and power is transmitted from the front end of the electric shaft 19 to the front differential device 43 in the front axle case 20, and the final reduction mechanism 45 · is transmitted from the front differential device 43 via differential yoke shafts 44L and 44R on both sides. The front wheels 14 and 14 are driven via 45.

Next, the front wheel rotation control device 29 of the present invention will be described.
As shown in FIG. 3, the front wheel rotation control device 29 includes a front first connecting device 51, a rear second connecting device 52, a means for detecting the rotational speed, a means for driving the connecting device, that is, a transmission torque. It comprises a changing means, a control unit 64 and the like. The first connecting device 51 and the second connecting device 52 are composed of a multi-plate hydraulic clutch. In the first coupling device 51, a friction plate provided in the clutch case 56 and a friction plate provided on the outer periphery of the boss portion of the first input gear 57 serving as input means are alternately arranged, and a hydraulic cylinder provided in the clutch case 56 is arranged. Pressure oil is fed and the piston is slid to bring the friction plate into pressure contact, so that the output shaft 55 can be driven from the first input gear 57 through the clutch case 56 at the same speed as the rear wheel.

  The second coupling device 52 has substantially the same configuration as the first coupling device 51, and the friction plate provided on the clutch case 56 and the friction plate provided on the outer periphery of the boss portion of the second input gear 58 serving as input means are alternately arranged. The transmission torque is changed by sending pressure oil to a hydraulic cylinder provided in the clutch case 56 and sliding the piston to press the friction plate, thereby changing the transmission torque from the second input gear 58 to the clutch case. The output shaft 55 can be driven at a speed higher than that of the rear wheels via 56. In the state where the second coupling device 52 is completely connected, that is, in the state where the output shaft 55 and the second input gear 58 rotate integrally, the peripheral speed of the front wheel is approximately twice the peripheral speed of the rear wheel. Further, the number of teeth of the front wheel speed increasing gear 41 and the second input gear 58 is set.

In the present invention, from the speed ratio at which the peripheral speed of the front wheel 14 and the rear wheel 15 is constant, the speed ratio at which the peripheral speed of the front wheel 14 is approximately twice the peripheral speed of the rear wheel 15 is When the rotational force is transmitted from the drive shaft 30 serving as the rear wheel drive unit to the output shaft 55 serving as the front wheel drive unit, the transmission torque of the second coupling device 52 is changed. When the engine 2 is rotated by the rotational force of the front wheels 14, the transmission torque of the first coupling device 51 is changed so that the engine brake is applied so that the rotational speed of the front wheels 14 is reduced. .
In this embodiment, a hydraulic clutch is used as the transmission torque changing means, and the hydraulic pressure supplied to the hydraulic clutch via an electromagnetic proportional valve is adjusted, or the electromagnetic valve is adjusted by PWM control to adjust the hydraulic pressure. However, it is also possible to use an electromagnetic clutch, a powder clutch or the like instead of the hydraulic clutch, and from the input means of the rear wheel part to the output shaft 55 of the front wheel drive part. Any means can be used as long as it can change the transmission torque.

  The first input gear 57 is always meshed with the front wheel drive gear 40, and the second input gear 58 is always meshed with the front wheel speed increasing gear 41. The clutch case 56 is fixed on an output shaft 55, and the front end of the output shaft 55 is connected to the transmission shaft 19 via a universal joint. A sensor 60 for detecting the rotation (speed) of the rear wheel 15 is disposed in the vicinity of the drive shaft 30 as a means for detecting the rotation speed (speed) of the rear wheel 15, and as a means for detecting the rotation speed (speed) of the front wheel 14 in the vicinity of the output shaft 55. A sensor 61 for detecting the rotation is disposed. The sensors 60 and 61 are connected to the control unit 64 to calculate the speed ratio. However, the sensor 60 can be disposed on the differential yoke shafts 35L and 35R, the final reduction mechanism 36, and the like, and the sensor 61 can be disposed on the differential yoke shafts 44L and 44R, the final reduction mechanism 45, and the like.

  Further, the control unit 64 operates the solenoid 62a of the electromagnetic valve 62 serving as transmission torque changing means for operating the hydraulic cylinder of the first coupling device 51 and the hydraulic cylinder of the second coupling device 52 via the drive circuit 65. The switch 63 is connected to the solenoid 63a of the electromagnetic valve 63 serving as a transmission torque changing means, and a switch 59 is further connected to the control unit 64 so as to be able to switch between two-wheel drive, four-wheel drive, and front wheel shift. 59 is arranged in the vicinity of the control unit 9. The control unit 64 is connected to an angle sensor 69 as means for detecting the steering angle of the handle 5, and the angle sensor 69 is disposed on the handle shaft portion of the handle 5. However, this steering angle detection means may be any means that can detect the steering angle of the front wheel 14, and can also be disposed in a rotating shaft portion of the front wheel 14 or a steering mechanism between the front wheel 14 and the handle 5.

  In the above configuration, when the changeover switch 59 is switched to the two-wheel (rear wheel) drive, the first connecting device 51 and the second connecting device 52 are not connected to each other, that is, the first connecting device 51 and the second connecting device 52 are connected. The solenoids 62a and 63a of the electromagnetic valves 62 and 63 in the device 52 are not actuated, and only the rear wheel 15 in which power is not transmitted from the drive shaft 30 to the output shaft 55 is in a two-wheel drive state, and the front wheel 14 is rotatable. It has become.

  Further, when the changeover switch 59 is switched to four-wheel drive, the first coupling device 51 is connected, and the first input gear 57 and the output shaft 55 have the same rotational speed (the circumferential speed of the front wheels 14 and the circumferential speed of the rear wheels 15 are the same). ). That is, when the changeover switch 59 is switched to the four-wheel drive, the solenoid 62a is operated via the drive circuit 65, the pressure oil is sent to the cylinder, and the friction plate is pressed against the first input gear 57 and the clutch case. 56 is integrally rotated and transmitted to the output shaft 55, and the front wheel 14 and the rear wheel 15 are driven at the same peripheral speed.

  When the changeover switch 59 is switched to the front wheel speed change, the peripheral speed of the front wheel 14 is increased to the theoretical speed ratio with respect to the peripheral speed of the rear wheel 15 in proportion to the turning angle of the handle 5. That is, in the straight traveling state, the first connecting device 51 is operated to drive the front wheels 14 and the rear wheels 15 at the same speed. For example, when the handle 5 is rotated to rotate at the end of the field, the rotation is performed. The angle is detected by the angle sensor 69, and the detected value is input to the control unit 64, and the control unit 64 outputs a signal to the drive circuit 65 in accordance with the rotation angle (steering angle). And the transmission torque of the second coupling device 52 is controlled. Specifically, when the electromagnetic valves 62 and 63 are subjected to PWM control, the connection time between the first coupling device 51 and the second coupling device 52 is adjusted to control the rotational speed of the front wheels 14. Further, when the electromagnetic valves 62 and 63 are constituted by electromagnetic proportional valves, the number of rotations of the front wheels 14 is controlled by controlling the pressure oil to the hydraulic cylinder.

Next, specific control by the control unit 64 in a state where the front wheel shift is switched according to the flowchart shown in FIG. 4 will be described. The control unit 64 includes a CPU, a ROM, a RAM, an interface, and the like.
First, when the changeover switch 59 is switched to the front wheel shift (S100), the drive shaft 30 disposed in the middle of the power transmission path from the engine to the rear wheel 15 in order to detect the rotational speed (circumferential speed) of the rear wheel 15. Is detected by the sensor 60, and the detected value is read and stored in the memory. Further, in order to detect the rotation speed (circumferential speed) of the front wheel 14, the rotation speed of the output shaft 55 arranged in the middle of the power transmission path to the front wheel 14 is detected by the sensor 61, and the detected value is read into the memory. Remember. Further, in order to detect the steering angle, the rotation angle of the handle 5 is detected by the angle sensor 69, and the detected value is read and stored in the memory (S101). The current speed ratio α1 is calculated from the speed of the rear wheel 15 detected by the sensor 60 and the speed of the front wheel 14 detected by the sensor 61 (S102). At this time, since it is not necessary to increase the speed in the substantially straight traveling state, that is, when the speed ratio α1 is smaller than α3 (α3 = 1 + threshold value as a dead zone), the front wheel 14 and the rear wheel 15 have the same peripheral speed. The set speed ratio α3 and the actual speed ratio α1 are compared so as to be driven (S103). When the ratio is less than α3, the electromagnetic valve 62 of the first coupling device 51 is operated to be in a directly connected state (104).
When the actual speed ratio is larger than α3, the theoretical speed ratio α2 is calculated from the detected value θ1 of the angle sensor 69 from the map shown in FIG. 7 (S105). Then, a difference β1 between the actual speed ratio α1 and the theoretical speed ratio α2 is obtained (106).

When the difference β1 between the actual speed ratio α1 and the theoretical speed ratio α2 is smaller than the threshold value β2 within the allowable range (S107), the front wheel speed is appropriate, and this state is maintained (S108).
When β1 is smaller than β2 (S109), the actual speed ratio α1 is smaller than the theoretical speed ratio α2, that is, in a state where the steering wheel is turned to turn, a resistance is received from the ground during turning, etc. When the peripheral speed of the front wheel 14 is slower than the peripheral speed determined by the steering angle, it is necessary to increase the speed, and the transmission torque of the second coupling device 52 is controlled to increase. That is, the torque according to the difference between the actual speed ratio α1 and the theoretical speed ratio α2 is increased, and the second coupling device 52 is connected so that the theoretical speed ratio α2 is obtained (S110). In order to control the transmission torque, the electromagnetic valve 63 supplies pressure oil to the hydraulic cylinder to increase the pressure in the hydraulic cylinder, and the piston presses the friction plate to increase the transmission torque. At this time, if the first coupling device 51 is operating, the transmission torque is decreased (not shown).

  Further, when the actual speed ratio α1 is larger than the theoretical speed ratio α2, the speed of the front wheels 14 is higher than the theoretical value, so it is necessary to reduce the peripheral speed of the front wheels 14. Control to increase transmission torque. In other words, when returning straight after turning, when turning sharply with a small turning radius, or when turning downhill, the peripheral speed of the front wheels 14 is faster than the peripheral speed determined by the steering angle. Need to slow down. Therefore, the torque of the first coupling device 51 is increased according to the difference between the actual speed ratio α1 and the theoretical speed ratio α2, so that the rotational force of the front wheels 14 is transmitted to the engine 2 via the first coupling device 51. Then, the front wheel 14 is decelerated by applying a braking force so that the theoretical speed ratio α2 is obtained by applying the engine brake (S111). In order to control the transmission torque, the electromagnetic valve 62 supplies pressure oil to the hydraulic cylinder to increase the pressure in the hydraulic cylinder, and the piston presses the friction plate to increase the transmission torque. At this time, if the second connecting device 52 is operating, the transmission torque is decreased (not shown).

By controlling in this way, the front wheels 14 and the rear wheels 15 are rotationally driven at the same peripheral speed when going straight, and the gripping force is also increased and stable running is possible. Then, the front wheels are controlled to an appropriate peripheral speed of the theoretical speed ratio when turning, and the front wheels can turn without slipping. Therefore, the turning radius due to slip, running resistance, and the like does not increase and tire wear is not promoted. In particular, in the case of an agricultural tractor, the field scene is not damaged by slipping and can be finished finely. In particular, even if the handle 5 is rotated quickly during turning, or is quickly returned to make it go straight, the peripheral speed of the front wheels is controlled to a speed that matches the theoretical speed ratio without any delay in response. Conventionally, the front wheel acceleration clutch is merely “disengaged”, so when the vehicle is returned to the straight traveling state, the peripheral speed of the front wheels is decelerated due to running resistance, resulting in a response delay.
Further, since the transmission torque changing means is configured to operate the hydraulic cylinder by switching the electromagnetic valves 62 and 63, the hydraulic clutch conventionally used in the transmission mechanism can be used, and with a simple configuration, It can be arranged compactly in the mission case, the types of parts can be unified, and assembly, control, management, etc. can be easily performed.

The side view of the tractor equipped with the front-wheel rotation control apparatus of this invention. The skeleton figure which shows a drive transmission path | route. The control block diagram of the front-wheel rotation control apparatus of this invention. FIG. The figure which shows the turning radius of four wheels at the time of turning. The skeleton figure which shows the conventional turning acceleration mechanism. The figure which shows the theoretical speed ratio between the front and rear wheels with respect to the steering angle during turning.

Explanation of symbols

2 Engine 14 Front wheel 15 Rear wheel 29 Front wheel rotation control device 51 First connection device 52 Second connection device 55 Output shaft 60/61 sensor 63 Electromagnetic valve 64 Control unit 69 Angle sensor

Claims (3)

  The power from the engine is transmitted to the rear wheels and the front wheels that can be steered via the front wheel rotation control device after shifting, and the front wheel rotation control device is constituted by a first connection device and a second connection device, and the first connection The device can transmit power from the rear wheel drive unit to the front wheel at a constant speed, and the second coupling device can transmit power by increasing the speed from the rear wheel drive unit, and the first coupling device and the second coupling device The transmission torque changing means is arranged and connected to the control part respectively, and the rear wheel driving part and the front wheel driving part are respectively provided with the rotation speed detecting means, and the steering mechanism is provided with the steering angle detecting means. A front wheel rotation control device for a four-wheel drive vehicle, characterized in that the transmission torque changing means is controlled so that the transmission ratio between the front wheels and the rear wheels during turning is a gear ratio according to the turning angle.   When the front wheel is driven by engine power during turning, the control unit transmits the transmission torque of the second coupling device so that the speed ratio of the front wheel and the rear wheel becomes a speed ratio corresponding to the turning angle. The front wheel rotation control device for a four-wheel drive vehicle according to claim 1, wherein the changing means is controlled. When turning, when the turning force of the front wheels exceeds the turning force of rotating the front wheels from the engine, the control unit first sets the speed ratio of the front wheels and the rear wheels to a speed ratio corresponding to the turning angle. 2. The front wheel rotation control device for a four-wheel drive vehicle according to claim 1, wherein transmission torque changing means of the coupling device is controlled.

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