JP3622217B2 - 4WD lock control device for tractor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a four-wheel drive (hereinafter referred to as 4WD) lock control device at the time of tractor work, and can be used for work on sloped terrain.
[0002]
[Background Art and Problems to be Solved by the Invention]
Conventionally, in tractor work on upland fields and slopes, the steering angle of the steering wheel is large and the steering changes are also large. Therefore, in order to stabilize the steering, it is necessary to switch the two-wheel drive (hereinafter referred to as 2WD) traveling to 4WD traveling and lock it.
Therefore, the applicant of the present invention is provided with a front wheel rotation sensor and a rear wheel rotation sensor in order to make the switching operation automatic, and a tractor that automatically switches between 2WD and 4WD by determining a traveling state according to detection of both rotation sensors. An application has been filed (Japanese Patent Application No. 4-252777). However, the 4WD switching device mounted on the tractor has a problem that it is difficult to operate accurately on a traveling surface or a sloping ground with particularly uneven surfaces.
[0003]
[Means for Solving the Problems]
In the present invention, the 4WD lock control device for the tractor is configured as follows to operate more accurately in accordance with the state of the vehicle. That is, as in the first aspect of the invention, the tractor includes the front wheel rotation sensor 8 and the rear wheel rotation sensor 9, and determines the running state according to the detection of both the rotation sensors 8 and 9, and automatically switches between 2WD and 4WD. The lock control device that locks to 4WD by switching between 2WD and 4WD more than a certain number of times in a certain time is provided, and the vehicle body is provided with a sensor 10 that detects the steering angle, and the lock control The 4WD lock control device is characterized in that the 4WD lock state is released by steering at a certain angle or more during operation of the device.
Further, as in the second aspect of the invention, an average value of the steering angle A before the lock operation is set as a reference steering angle B, and the steering more than a certain angle is performed with respect to the reference steering angle B. The 4WD lock control device according to claim 1, wherein the 4WD lock state is released by this.
[0004]
[Operation and effect of the invention]
According to the first aspect of the present invention, during traveling by 4WD by front and rear wheel driving, it is automatically switched to 2WD by rear wheel driving depending on traveling conditions such as a steering angle of the vehicle body and slip, or further from this 2WD to 4WD. Return to. When the switching control between 4WD and 2WD is performed more than a certain number of times within a certain time, the 4WD automatically locks based on this, but when the vehicle body is steered more than a certain angle, the lock The state is released, and it returns to 2WD once again.
[0005]
In the invention of claim 2, the average value of the steering angle for a certain period of time until the 4WD lock control is performed is set as the reference steering angle B, and the 4WD lock control is performed. Then, the 4WD lock is released by performing a certain amount of steering with respect to the reference steering angle.
As a result, the amount of steering wheel operation necessary to always release the lock becomes constant, and excessive switching control between 2WD and 4WD is prevented, and the life of components such as switching clutches between 2WD and 4WD is improved and control is performed. Can be stabilized.
[0006]
【Example】
1 to 3, the transmission mechanism of the tractor vehicle body is transmitted from the engine E to the traveling shaft 2 via the main clutch 1 and the main transmission device, the auxiliary transmission device, and the like. After that, the rear wheel 3 and the front wheel 4 are transmitted. The 4WD clutch 5 is in a transmission path for transmitting the front wheels 4 from the traveling shaft 2 and is constituted by a hydraulic clutch. When the 4WD clutch 5 is in the neutral position, transmission to the front wheels 4 is not performed. However, when the clutch is connected to the normal speed gear 7 side, the front wheel 4 is 4WD that is driven to rotate at the same speed as the rear wheel 3, and when the clutch is connected to the double speed gear 6 side, the front wheel 4 is the rear wheel. Double speed 4WD transmitted at a speed higher than 3 (for example, increased from 1.7 times to 2 times).
[0007]
A controller CPU having a 4WD lock control device for outputting the 4WD clutch 5 has a microcomputer, and a front wheel rotation sensor 9 for detecting the rotation of the normal speed gear 7 and a rear wheel rotation for detecting the rotation of the double speed gear 6. A sensor 8, a steering sensor 10 that detects the steering angle A of the front wheel 4, and the like are input, and a pitching sensor 11 that detects the front-rear tilt angle of the vehicle body, and a rolling sensor that detects the left-right tilt angle of the vehicle body 12, a position lever 13 for operating the lift position of the working device with respect to the vehicle body, a control mode switch 14, and the like. The mode switch 14 can select a 2WD mode, a 4WD mode, and an automatic mode (which may be full-time 4WD control) that automatically switches between 2WD and 4WD.
[0008]
If the automatic mode is selected by the mode switch 14, the vehicle is automatically switched to 2WD according to the traveling condition while traveling at 4WD, and automatically returns to 4WD. For example, if the tractor operation is performed while traveling in the direction along the contour line on the slope θ, the change in the steering angle A is detected by the detection input of the steering sensor 10 as shown in FIG. As for the change in the steering angle A, an average steering angle is calculated every certain time, for example, every 5 seconds. For this reason, for example, when switching between 2WD and 4WD three times or more in 15 seconds is controlled, the average steering angle in 5 seconds immediately before this is set as the reference steering angle B, and at the same time 4WD Therefore, the lock control C is performed and the control to 2WD is restrained.
[0009]
Therefore, during the 4WD lock control, the steering wheel neutral position is set to the reference steering angle B and the steering control is performed. Therefore, when the steering angle A is within the region from the left side (upward side) α to the right side (downward side) β with respect to the reference steering angle B, the 4WD control is locked and the 4WD control is maintained. It is difficult to perform detailed steering control. However, when the steering angle A exceeds the allowable range α to β, D, and the 4WD lock is released from the point D at which the steering angle A exceeds the range. Therefore, for example, when the turning angle A of the steering wheel becomes larger than a certain value depending on the traveling condition, the driving wheel is switched to 2WD. The same control is performed thereafter.
[0010]
In the case of running in the contour direction on the slope, in the case of FIG. 2, the steering wheel is tilted upward to the left, so the steering angle of the steering wheel is a forced turning angle, and the right steering angle is the neutral position (straight forward position). ) Is the return angle to return to.
It should be noted that during traveling by the 4WD lock control in the normal straight traveling state in the automatic mode, switching control is performed so that the 4WD lock is released by detection of the steering sensor 10 during turning. The front wheel rotation sensor 8, the rear wheel rotation sensor 9, and the like can detect the traveling speed of the vehicle body and the slip of the front and rear wheels. When the wheels 3 and 4 have a lot of slip, 4WD travel is performed.
[0011]
In FIG. 4, in the automatic switching control between 4WD and 2WD, a runaway check of the control program is performed by a watchdog timer, and when it is determined that runaway occurs, the program is reset. The initial output of this program is 4WD. As a result, the program runaway is prevented by being reset by the watchdog timer, and the initial output when the reset is applied is set to 4WD, thereby ensuring the stability of the vehicle running.
[0012]
5 to 8, the present invention relates to a configuration of a hydraulic pressure switching valve 15 that performs switching operation between 2WD and 4WD for operating the 4WD clutch 5 (FIG. 1) by the output from the controller CPU. The switching valve 15 for controlling the 4WD clutch 5 is a three-way switching valve including a neutral position. In the neutral position (FIG. 5), the two output ports C6 and C7 are tank ports via orifices (throttles) 16 and 17, respectively. When communicating with T and switching to either C7 (FIG. 6), the other output port C6 is dropped directly to the tank port T without passing through the orifice 16.
[0013]
The switching valve 15 shown in FIGS. 5 to 7 has a spool 20 that is actuated by electromagnetic solenoids 18 and 19, a pump port P, a tank port T, and an output port on the normal speed gear 7 side of the 4WD clutch 5. The orifices 16 and 17 are provided between the spool area of each of the output ports C6 and C7 and the spool area of the tank port T.
[0014]
The relationship between the oil pressure of the 4WD clutch 5 working cylinder and the rotational speed of the front wheel 4 when the throttle is not provided in the tank port is as shown in (1) and (2) of FIG. Here, assuming that the port that is not always in the output state is communicated with the tank port via the orifice, when the output port is instantaneously switched from one output port to the other output port (particularly at low temperatures), the output is cut off. Since it takes time for the oil pressure to drop, the 4WD clutch in the meantime is in a state of simultaneous operation, and the clutch life is shortened (as shown in (3) of FIG. 8).
[0015]
Further, when front wheel drive control is performed based on the front and rear wheel peripheral speed ratios, when the vehicle is in a 4WD traveling state, the front and rear wheel peripheral speed ratios need to be temporarily set to the 2WD state. At this time, the tank port of the hydraulic pressure switching valve is throttled and the hydraulic pressure is gradually lowered to suppress a sudden change in the rotation of the front wheels, but when the two-way output port between 4WD and the front wheel double speed is instantaneously switched, Although it is a short time, the simultaneous operation state of the 4WD clutch occurs, and the above problem occurs.
[0016]
In the present invention, the effect of the orifices 16 and 17 is maintained as shown in FIG. 8 (4), and the oil in one 4WD clutch 5 is dropped directly into the tank port T when one side 4WD clutch 5 is operated. Thus, simultaneous operation of the clutch 5 is prevented.
[Brief description of the drawings]
FIG. 1 is a control diagram of a traveling transmission system.
FIG. 2 is a graph showing a relationship between a steering angle of a steering wheel and 4WD lock control.
FIG. 3 is a graph showing a steering angle range of a steering handle.
FIG. 4 is a flowchart of runaway check control.
FIG. 5 is a plan view of a 4WD clutch switching valve.
FIG. 6 is a plan view showing the operation.
FIG. 7 is a hydraulic circuit diagram thereof.
FIG. 8 is a pressure diagram thereof.
[Explanation of symbols]
4 Front wheel 5 4WD clutch 10 Steering sensor 15 Switching valve A Steering angle B Reference steering angle CPU controller (4WD lock control device)

Claims (2)

In a tractor that includes a front wheel rotation sensor 8 and a rear wheel rotation sensor 9 and that automatically determines between 2WD and 4WD based on detection of both rotation sensors 8 and 9 , 2WD more than a certain number of times within a certain time. steering and with switching between 4WD constitute a lock control device that locks the 4WD by carried out, the sensor 10 for detecting the steering angle to the vehicle body is provided, over a certain angle during operation of the lock control device The 4WD lock control device releases the 4WD lock state by performing. An average value of the steering angle A before the lock operation is set as a reference steering angle B, and the steering of a predetermined angle or more with respect to the reference steering angle B is performed to release the 4WD lock state. The 4WD lock control apparatus according to claim 1.

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