JP2002331956A - Automatic transmission mechanism for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unstable state of equipment of a working vehicle by performing a deceleration to a proper speed while keeping the drive force necessary for a work in the turning of the working vehicle. SOLUTION: In the turning of the working vehicle, the instability degree of equipment is detected by a steering angle sensor 124 and equipment angular sensors 96 and 97, and when the instability degree is larger than a set instability degree, the traveling speed is preliminarily reduced by use of a continuously variable transmission 23 automatically controlled by a controller 110. When the instability degree of equipment is remarkably large, the speed is set to zero to stop the traveling of the working vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control for a work vehicle such as a tractor, which automatically reduces the vehicle speed when the posture of the machine is likely to fall down, and automatically returns to the original speed after avoidance. Regarding the mechanism.

[0002]

2. Description of the Related Art A work vehicle such as a tractor can make a small turn by a brake mechanism that brakes a rear wheel inside a turn or a front wheel speed-up mechanism that makes a driving rotational peripheral speed of a front wheel faster than that of a rear wheel. Techniques are known. When making a small turn in such a work vehicle, the body attitude becomes unstable when turning at a certain speed or more, and in particular, during small turns, the rotational centrifugal force increases and the body instability increases,
By reducing the rotation of the engine and reducing the vehicle speed when turning, the aircraft was kept in a stable posture.

[0003]

However, during turning of a conventional work vehicle, when the body becomes unstable, the operator operates the transmission or the accelerator lever to decelerate, so that the vehicle turns sharply. In some cases, or when the attitude of the machine becomes unstable on a slope, it may be difficult to perform the deceleration operation immediately because the operator must support his or her body. In particular, when deceleration is performed by switching the stepped shift, it is necessary to depress the clutch pedal, and it is necessary to select a shift speed, so that it is difficult to obtain an optimum speed for work, and the driver shifts gears promptly. It was difficult.

[0004]

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

That is, in the first aspect of the present invention, there is provided a hydraulically driven continuously variable transmission mechanism which performs traveling by changing the speed by a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. In the work vehicle, a control means is connected to the control means, the steering angle detection means, the traveling speed detection means, the traveling speed setting means, and the speed changing means of the continuously variable transmission mechanism connected to the control means. When the turning angle becomes equal to or larger than the set angle, the continuously variable transmission mechanism is automatically decelerated.

According to a second aspect of the present invention, there is provided a work vehicle having a hydraulically driven continuously variable transmission mechanism that travels while changing the speed by a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. A means for detecting a steering angle, a means for detecting an attitude of the main body, a means for detecting a traveling speed, a means for setting a traveling speed, and a speed changing means for a continuously variable transmission mechanism connected to a control means. The speed is automatically reduced to a predetermined speed based on the detected traveling speed, the attitude of the machine and the steering angle.

According to a third aspect, in the deceleration state,
When returning to the vehicle speed set by the main shift lever and the auxiliary shift lever, the control means controls the return speed to the set vehicle speed to gradually increase.

According to a fourth aspect of the present invention, the degree of instability is calculated from the attitude of the vehicle, the steering angle and the vehicle speed, and if the degree of instability is equal to or greater than a set value, the driving is automatically stopped. It was done.

[0009]

Next, embodiments of the present invention will be described. 1 is a left side view of a tractor equipped with the automatic transmission mechanism of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a side sectional view of a transmission case, and FIG. 4 is a skeleton view showing a drive transmission mechanism. 5 is a side view of a main transmission lever mounting portion, FIG. 6 is a side view of an auxiliary transmission lever mounting portion, FIG. 7 is a side view of a transmission portion of a transmission case, FIG. 8 is a partially enlarged view thereof, and FIG. 9 is a hydraulic circuit diagram. FIG. 10 is a side view of a turning angle reduction switch mounting portion,
11 is a partially enlarged view of the same, FIG. 12 is a side view of a connecting portion between the gear case and the pitman arm, FIG. 13 is a side view of a cutting angle sensor mounting portion, FIG. 14 is a sectional view of the same, FIG. FIG. 16 is a control block diagram, and FIG.
7 and 18 are flowcharts.

First, a schematic configuration of a tractor which is an embodiment of a work vehicle provided with an automatic transmission mechanism according to the present invention will be described.

As shown in FIGS. 1 and 2, the working vehicle has an engine 2 disposed in front of the machine, and the engine 2 is covered with a hood 3. A steering handle 5 serving as a steering means is disposed on a dashboard 4 located at a rear portion of the hood 3, and an accelerator lever 18 and a forward / reverse switching lever 8 serving as a forward / reverse switching operation tool are provided on a side of the dashboard 4. It is arranged in a protruding state. Then, below the dashboard 4 and above the step 39, the brake pedal 17 and the accelerator pedal 28
And a clutch pedal 42 is provided on the left side.

A seat 6 is disposed behind the steering handle 5, and a sub-shift lever 10, a PTO shift lever 11, a work implement elevating lever 12, and a working depth setting means are provided near the seat 6 as sub-shift operation tools. And a main transmission lever 7 serving as a main transmission operation tool is disposed on the fenders 21 located on the left and right sides of the seat 6. The main transmission lever 7 and the sub transmission lever 10 serve as a traveling speed setting means. The portion where the seat 6, the steering handle 5, the lever, and the like are centrally arranged is defined as a control section 9 of the machine. The positions of the levers are not limited.
Should be near.

Further, front wheels 13 are supported on both sides of the front of the machine, and rear wheels 14 are supported on both sides of the rear. A mission case 15 is arranged below the seat 6 and a three-point link type working machine mounting device 16 for mounting various working machines 139 to the machine is arranged behind the transmission case 15. . In the present embodiment, a work vehicle equipped with a rotary tilling device as a work machine 139 is illustrated.

A cylinder case 148 is provided below the seat 6, and as shown in FIG. 15, a left / right angle sensor 96 is provided near the cylinder case 148 (front).
The device is provided with a front-rear angle sensor 97 disposed at the rear thereof to detect the left-right and front-rear inclination of the device. The main unit left / right angle sensor 96 and the main unit front / rear angle sensor 97
Is connected to the work implement control controller 109 and the travel control controller which are control means.

Next, the transmission mechanism of the work vehicle will be described with reference to FIG.
This will be described with reference to FIG.

Power is transmitted to the input shaft 33 of a hydraulic pump 51 of an HST (hydraulic continuously variable transmission) 23 disposed in the transmission case 15 via a damper 20 or a clutch at the rear of the output side of the engine 2. You. The input shaft 33
Extends rearward through the hydraulic pump 51,
Through the PTO drive shaft 48 to drive the hydraulic pump 51 and the PTO shaft 27 via the PTO transmission mechanism 26.
Power is transmitted to. An engine speed sensor 113 is disposed near the output shaft of the engine 2 to detect the speed of the engine 2. The engine speed sensor 113 is connected to the travel control controller 110.

The HST 23 comprises a variable displacement type hydraulic pump 51 and a fixed displacement type hydraulic motor 52. A movable swash plate 53 constituting the hydraulic pump 51 has a hydraulic cylinder 67 serving as an actuator as a speed changing means to be described later.
And the hydraulic cylinder 67 is driven by operation of the main shift lever (HST lever) 7 and the like.

In this embodiment, as shown in FIG. 5, the main transmission lever 7 is disposed on the fender 21 of the control section 9, and a lever guide 54 is provided on the fender 21 to form a crank-shaped guide. The main transmission lever 7 is inserted into the groove, and the main transmission lever 7 is provided near the rotation base of the main transmission lever 7.
And a lever sensor 111 composed of an angle sensor serving as a means for detecting the rotational position of the camera. Specifically, the turning shaft 55 of the main transmission lever 7 projects from the hydraulic case 56 on the transmission case 15 and the turning shaft 55
, And a pin protruding from the arm 57 is inserted into a groove formed in the sensor arm 111a of the lever sensor 111 to transmit the rotation of the rotation shaft 55 to the lever sensor 111,
The rotation position of the main transmission lever 7 is detected.
The lever sensor 111 is connected to the travel control controller 110.

An auxiliary transmission 24 is disposed behind the HST 23, that is, downstream of the power transmission path. HST2
Power is transmitted from the output shaft 25 of the third hydraulic motor 52 to the auxiliary transmission 24, and the auxiliary transmission 24 slides the sliding gear 31 to enable three-speed shifting. The sliding gear 31 slides with a shifter (not shown) connected to a sub-transmission operation shaft 69 shown in FIG.
Is fixed. One end of a sub-transmission lever link 59 is rotatably connected to the tip of the sub-transmission arm 58, and the other end of the sub-transmission lever link 59 is connected to an end of the sub-transmission lever 10. In this way, the sub-transmission lever 10 is connected to and linked with the sliding gear 31 of the sub-transmission 24 via the link mechanism including the sub-transmission arm 58 and the sub-transmission lever link 59 and the like.

The sub-transmission lever 10 is disposed on the side of the hydraulic case 56 opposite to the main transmission lever 7 and has a fulcrum shaft 60 protruding from the side of the hydraulic case 56 on the auxiliary transmission lever 1.
The lower part of 0 is pivoted. And, the sub-shift lever 10
, Ie, near the fulcrum shaft 60,
6, the sensor arm 116a of the sub-transmission position sensor 116 is arranged to abut on a pin protruding from the sub-transmission lever 10 to detect the rotational position of the sub-transmission lever 10. However, the sub-shift position sensor 116
May be arranged on the fulcrum shaft 60. Further, the sub-transmission lever 10 and the main transmission lever 7 can be disposed on the dashboard 4 or the like, and the positions are not limited.

The output shaft of the auxiliary transmission 24 is used as a drive shaft 30, and the power after being shifted by the auxiliary transmission 24 is transmitted through a drive pinion 32 provided at the rear end of the drive shaft 30. The power is transmitted to the wheel differential device 34, and the left and right differential yoke shafts 35 from the rear wheel differential device 34.
L / 35R, rear wheel 14 via final reduction mechanism 36/36
・ 14 is driven. The rotation speed of the rear wheel 14 is detected by an axle rotation speed sensor 112 to detect the actual traveling speed. In this embodiment, the rotation of the differential yoke shaft 35L is detected, but the rotation of the gear of the final reduction mechanism 36, the rotation of the axle to which the rear wheel 14 is fixed, and the rotation of the drive shaft 30 are detected. You can also.

A front wheel drive gear 40 is fixed on the drive shaft 30 and transmitted from the front wheel drive gear 40 to the front wheel transmission 29 via a double counter gear 41. The front wheel transmission 29 is an occlusal four-wheel drive clutch 3.
7 and the front wheel speed-increasing clutch 38, and both clutches are OF
In the case of F, it is a two-wheel drive with only the rear wheels, and is operated for traveling on the road. When the four-wheel drive clutch 37 is turned on, the front wheels 13, 13 and the rear wheels 14, 14 are driven at the same speed, and are activated at the time of work or the like. The front wheel speed increasing clutch 38 is turned on when the steering wheel 5 is rotated by a predetermined angle or more during operation.
Thus, the driving speed of the front wheels 13 is increased more than that of the rear wheels 14 so that the front wheels 13 are driven at approximately twice the speed.

The power that has been shifted by the front wheel transmission 29 is transmitted from the output shaft via the transmission shaft 19 to the front differential device 43 in the front axle case.
Diff yoke shafts 44L on both sides of the front differential device 43
The front wheels 13 are driven via 44R and the final deceleration mechanism 45.

As shown in FIG. 10, a steering hydraulic cylinder 98 is attached to the front differential device 43, and an angle sensor shaft is attached to a piston rod of the steering hydraulic cylinder 98 via a sensor plate 90. 91 are provided. As shown in FIG.
Two cutting angle detection notches 92 are provided on the outer periphery of the center of the cutting angle sensor shaft 91.
Reference numeral 2 denotes a detection surface cut so as to be parallel to a tangent line, and a surface formed by the two cutouts 92 for detecting a cutting angle is substantially V-shaped. Then, from the outside of the support case 93 toward the left and right central portions of the two cutting angle detection notches,
Toward the substantially axis of the sensor shaft, the mounting holes 93a and 9
3b is bored and communicated with the inside of the support case 93. The line connecting the centers of the mounting holes 93a and 93b is the sensor shaft 9
1 is perpendicular to the axial direction.
Thus, the steering angle switch 94 is arranged in a compact and concentrated manner. The mounting hole 93
a and 93b each having one or more balls 95.9
After inserting the steering angle switch 5, the steering angle switch 94 is attached, the balls 95 and 95 respectively contact the two cut angle detection notches 92, and the detecting portions of the angle reduction switch contact the balls 95 and 95, respectively. To be installed in Thus, when the turning angle of the steering handle 5 becomes greater than or equal to the set value, the sensor shaft 91 slides via the sensor plate 90, the ball 95 is pushed out from the notch 92 for detecting the turning angle, and the steering turning angle switch 94 is turned on. Input to the travel control controller 110,
It is controlled to decelerate. It should be noted that the two cut-off angle detecting notches 92 can be configured to have different lengths so that the cut-off angle of the steering handle 5 can be detected in two stages. The timing of deceleration can be selected based on the difference, the height of the work equipment, and the like. For example, at high speeds, when the tilt angle of the machine is large, or when the working machine is raised, the vehicle is decelerated with a small steering angle.

Next, a steering angle sensor serving as a means for detecting a steering angle will be described with reference to FIGS. 12, 13 and 14. FIG. By rotating the steering handle 5, the handle shaft 5 of the steering handle 5 is moved.
a from the gear case 12 via the universal joint
0, the transmission direction is changed in the gear case 120 and transmitted to the pitman arm 121. The pitman arm 121 is integrally fixed to a rotation shaft 122 protruding from the gear case 120 and is rotatable. Further, an arm 123 protruding upward in FIG. 13 is fixed to the pitman arm 121. A turning angle sensor 124 is disposed above the pitman arm 121, and a pin 125 protruding from the arm 123 is inserted into a groove formed in the sensor arm 124 a of the cutting angle sensor 124, and the turning operation of the turning shaft 122 is performed. Cut angle sensor 124
To detect the turning angle of the steering wheel 5. Note that the turning angle sensor 124 is connected to a traveling control controller 110 described later.

As shown in FIG. 7, a trunnion shaft (shift shaft) 61 is connected to the movable swash plate 53 of the hydraulic pump 51 of the HST 23, and the trunnion shaft 61 projects from the HST storage case 62, and Shift arm 6 at the tip
3 is fixed. One end of the shift arm 63 (63
In a), a pin 63ab fixed to the shift arm 63 is engaged with an engagement groove 64ab formed in the sensor arm 64a of the angle sensor 64, and the shift arm 63 and the sensor arm 64a of the angle sensor 64 are engaged. I agree. The angle sensor 64 is connected to the HST storage case 6 above the trunnion shaft 61.
2 and the shift arm 63 (trunnion shaft 6
The rotation angle of 1) is detected. That is, the angle sensor 64
Detects the shift position of the HST 23 and is connected to a travel control controller 110 described later. The angle sensor 64 is constituted by a potentiometer, a rotary switch, a rotary encoder, or the like, and is not limited.
The angle sensor 64 may be disposed on or around the trunnion shaft 61, and the mounting position is not limited.

The other end (63b) of the shift arm 63 extends downward and is pivotally supported by one end (65b) of the connecting link 65. The other end (65a) of the connection link 65 extends rearward and is pivotally supported by one end (66a) of the connection arm 66, and the other end (66b) of the connection arm 66 is a piston rod of a hydraulic cylinder 67 serving as an actuator. 67a is pivotally supported at the tip. The connecting arm 66 has a fulcrum bracket 6 whose middle part is fixed to the side surface of the transmission case 15.
8 and is pivotally supported by a pin 66c standing upright. Therefore, when the piston rod 67a of the hydraulic cylinder 67 expands and contracts,
The connection arm 66 rotates about the pin 66c, and the connection link 65 slides back and forth in conjunction with the rotation of the connection arm 66, thereby rotating the shift arm 63 about the trunnion shaft 61. At this time, the trunnion shaft 61 rotates with the rotation of the shift arm 63. That is, the trunnion shaft 61 is rotated by the expansion and contraction of the piston rod 67a of the hydraulic cylinder 67, and the movable swash plate 53 of the hydraulic pump 51 of the HST 23 is controlled.

In this way, the movable swash plate 53 is linked and interlocked with the hydraulic cylinder 67 serving as an actuator via the link mechanism, and the hydraulic cylinder 67 is expanded and contracted by switching a control valve 86, which will be described later, according to a control signal of the traveling control controller 110. Then, the connection arm 66, the connection link 6
5. By rotating the trunnion shaft 61 via the shift arm 63, the movable swash plate 53 can be tilted, and the speed can be controlled by changing the speed. As shown in FIG. 8, the tilt angle (current trunnion shaft angle T ) Is detected by the angle sensor 64 and fed back to the travel control controller 110.

Next, the hydraulic circuit will be described with reference to FIG.

When the engine 2 is driven, the first pump 71
, Second pump 72, charge pump 73, and hydraulic pump 5
1 is driven to suck the working oil in the transmission case 15 through a filter, and the pressure oil from the second pump 72 is sent to a hydraulic cylinder for lifting and lowering the work implement 139 and a hydraulic cylinder for horizontal control of the work implement 139 (not shown). It can be driven after being lubricated. A diverting valve 74 is connected to the discharge side of the first pump 71, and the diverting valve 74 is a priority valve. The diverting valve 74 is connected to the HST 23 and a control hydraulic cylinder 67 in a diverting oil passage on the priority side. Power steering control valve 75 and power steering cylinder 7
6 is connected.

A relief valve 77 for setting the control pressure of the hydraulic cylinder 67 and a control valve 86 are connected to the priority side output oil passage of the flow dividing valve 74. The control valve 86 includes an electromagnetic valve 78 for controlling expansion and contraction of the hydraulic cylinder 67, an electromagnetic valve 79 for controlling contraction, and an electromagnetic valve 80 for controlling the amount flowing to the charge pump 73. However, the electromagnetic valves 78, 79, and 80 can be constituted by one electromagnetic valve. The electromagnetic valve 80 controls the opening and closing by adjusting the duty ratio by PWM control.
By controlling the flow rate, the hydraulic pressure to the hydraulic cylinder 67 is controlled.

The electromagnetic valve 78 or the electromagnetic valve 79 is switched by an operation described later, and the hydraulic cylinder 67 is switched.
Extend or contract, change the tilt angle of the movable swash plate 53 to change the discharge amount and discharge direction of the hydraulic pump 51, rotate the output shaft 25 of the hydraulic motor 52 forward or backward, and move the machine forward. Or it can be moved backwards. HST23
Are oil passages 81.8 between hydraulic pump 51 and hydraulic motor 52.
2 to form a closed circuit, the oil pressure in the oil passages 81 and 82 is detected by pressure sensors 114 and 115, and the pressure sensors 114 and 115
0 is connected. Pressure oil from the charge pump 73 is connected to the closed circuit via a filter 83, a throttle 84, and a check valve 85 so as to be replenishable.

Next, the control configuration will be described with reference to FIG. The traveling control controller 110 includes a main shift lever sensor 11 for detecting a rotation position (shift position) of the main shift lever 7.
1. A sub-shift position sensor 116 for detecting the turning position (shift position) of the sub-shift lever 10, an angle sensor 64 for detecting the turning angle of the trunnion shaft 61, and a turning position of the forward / reverse switching lever 8. Direction change switch 102, axle speed sensor 112 for detecting the speed of the axle, engine speed sensor 113 for detecting the speed of engine 2, HST
Pressure sensor 11 for detecting the pressure of oil passages 81 and 82 of 23
4.115, brake non-connection switch 105, steering angle sensor 12 for detecting angle of steering 5
4. A steering angle switch 94 for detecting the angle of the steering wheel 5 is connected. In addition, the traveling control controller 110 includes the electromagnetic valves 78 and 79.
Solenoids 78a and 79a are connected, and the electromagnetic valve 78 is controlled by a control signal from the travel control controller 110.
By switching 79, the hydraulic cylinder 67 is driven to expand and contract to change the angle of the trunnion shaft 61 (movable swash plate 53).

The work machine controller 109 includes a steering angle switch 94 for detecting the angle of the steering 5, a work machine vertical lever sensor 147 for detecting the position of the up and down levers of the work machine 139, and detecting the elevation of the work machine 139. Work machine elevating sensor 106, lift angle sensor 107 for detecting the lift angle of work machine 139, work machine 139
Machine angle sensor 108 for detecting the angle of the machine, the machine left / right angle sensor 96 for sensing the machine angle in the horizontal direction, the machine front-rear angle sensor 97 for sensing the machine angle in the front-rear direction, and the angular velocity of the machine 139 Position setting dial 13 for setting the rising position of the work machine 139
1. Work implement inclination setting dial 132 for setting the inclination of work implement 139, tillage setting dial 133 for setting the plowing depth by work implement 139, work changeover switch 134 for detecting switching of work implement 139, control of work implement 139 And a control content selection switch 136 for switching the control content of the work implement 139 are connected. The work machine control controller 109 is connected with a work machine lift (lift arm) cylinder 137 and a work machine lift (lift rod) cylinder 138.

In such a configuration, control by the automatic transmission mechanism according to the present invention will be described with reference to flowcharts shown in FIGS.

The work vehicle normally travels at a set speed determined by the auxiliary shift lever 10 for shifting gears and transmissions, the main shift lever 7 for determining the angle of the trunnion shaft 61 of the HST 23, and the accelerator lever. ,
When turning at a certain speed or more or when making a small turn, the machine may be tilted due to the rotational centrifugal force and become unstable. In the automatic transmission mechanism according to the present invention, in order to prevent the above-mentioned unstable state of the machine, the traveling control controller 110 and the work machine control controller 109 use the actual values of the machine according to the values detected by the machine angle sensors 96 and 97. The stability is calculated, and the main shift lever sensor 111, the auxiliary shift position sensor 116, the axle speed sensor 112, the engine speed sensor 113, the trunnion shaft angle sensor 64, the HST pressure sensors 114 and 115,
In addition, the detection information of the steering angle sensor 124 is compared with a set value to detect the actual degree of instability, and when the degree of instability exceeds a predetermined degree, deceleration is performed.

First, the current rotation position of the main transmission lever 7, the rotation position of the auxiliary transmission lever 10, and the trunnion shaft 61
Are read by the sensors 111, 116, and 64, respectively. Next, the signal of the direction changeover switch 102 is input to the traveling controller 110 to determine the position of the forward / reverse changeover lever 8 Then, the travel controller 110 calculates the basic set value Tb of the trunnion axis angle T (151). In this case, the basic set value T
b is the main shift lever sensor 111 and the sub shift position sensor 11
5 is the basic value of the trunnion axis angle T set based on the information from No. 5, and when the vehicle speed control is not performed, this value becomes the control target value of the trunnion axis angle T as it is.

Next, it is determined by a steering angle sensor provided on the pitman arm whether or not the steering angle exceeds a set angle based on information from the angle sensor. (152).

If the steering angle exceeds the set angle (153), the turning deceleration target value Tt, which is the target value of the trunnion shaft angle T for reducing the vehicle speed, is calculated (154). The turning deceleration target value Tt is a target value for decelerating in advance from the basic set value Tb, and includes a main transmission lever sensor value 111, an auxiliary transmission lever sensor value 116, an engine speed sensor value, and an axle speed sensor. It is determined by a predetermined formula using the value, the HST pressure sensor value, and the cutting angle sensor value.

After calculating the deceleration target value Tt, the attitude instability Qc of the machine is calculated (155). The machine attitude instability Qc is used to check the degree of instability of the machine at the time of turning. The turning speed deceleration target value Tt, the turning angle sensor value, the main shift lever sensor value 111, and the sub shift lever sensor value 116 are used.
・ Engine speed sensor value ・ Axle speed sensor value ・ HS
It is determined by a predetermined calculation formula based on the T pressure sensor value.
Alternatively, it is determined by deriving from a map stored in a memory in advance. In this map, the vehicle speed, the inclination of the machine and the degree of instability with respect to the steering wheel turning angle are determined.

Next, it is determined whether or not the posture of the main unit is unstable beyond a preset control range, based on the information of the degree of posture instability Qc of the main unit. (156). If the aircraft attitude instability Qc exceeds a preset control range,
The work vehicle is stopped (157). The preset control range is a range in which the vehicle speed can be reduced by the automatic transmission mechanism according to the present invention so that the work can be performed substantially at the target traveling speed, and the traveling is performed in advance using the automatically controlled continuously variable transmission mechanism. This is to reduce the speed and prevent the posture of this machine from becoming unstable. Therefore, when the inclination of the attitude of the apparatus is so great that it cannot be prevented by the automatic control, the trunnion axis angle T is set to the neutral position (T = Tn). That is, when the degree of instability of the vehicle body becomes extremely large, a safety mechanism is provided for stopping the traveling of the work vehicle by setting the target speed to zero and urgently avoiding danger.

On the other hand, when the degree of body posture instability does not exceed the control range, the maximum safe speed Ss during turning is determined by the degree of body posture instability, the main body posture left / right angle sensor, the main body posture front / rear angle sensor, and the turning angle. The value is calculated from the sensor value, the auxiliary transmission lever, and the axle rotation speed sensor value (158), and the trunnion axis target value is set to the safe speed using the safe maximum speed (15).
9).

The output parameter Gtg to the hydraulic cylinder 67, which is the drive actuator for the trunnion shaft 61, is set based on the trunnion shaft target value at the time of speed recovery (16).
0).

On the other hand, when the steering angle is within the set range, the turning deceleration target value Tt, the steering angle sensor value,
Main transmission lever sensor value 111 / Sub transmission lever sensor value 1
16. Engine speed sensor value / axle speed sensor value
Based on the HST pressure sensor value, the attitude instability Qc of the machine is calculated (162), and the degree of instability of the machine at the time of turning is checked.

The maximum safe speed Ss at the time of turning is determined by the body posture instability, the machine posture left / right angle sensor value, the machine posture front / rear angle sensor value, the turning angle sensor value, the auxiliary transmission lever position, and the axle rotation speed sensor value. Calculate (163) and set the trunnion axis target value to the safe speed using the safe maximum speed (1).
64).

When the steering angle returns from the deceleration range to the normal range or when the inclination of the machine becomes equal to or smaller than the set angle, the output parameter to the hydraulic cylinder 67 as the drive actuator of the trunnion shaft 61 is changed. The target value is set to the trunnion axis target value at the time of speed return (166), and the speed is gradually increased so that the speed does not suddenly increase and a shock does not occur. If the steering angle has not returned to the normal range from the deceleration range, the output parameter to the hydraulic cylinder 67, which is the drive actuator for the trunnion shaft 61, is set to the normal trunnion shaft target value (167).

As described above, the automatic speed change mechanism is configured to prevent the machine from becoming unstable during turning, so that the operator can automatically change the vehicle speed without performing any special operation, and the machine is not operated during turning. A stable state can be prevented. Also,
Since the speed is automatically changed to the target speed even when the unstable state of the machine at the time of turning converges, the operator simply operates the work vehicle with the control unit 9 as usual, The regulation of the vehicle speed becomes stricter than before, and the target vehicle speed can be maintained. In addition, when the machine is extremely unstable during turning, if the vehicle speed of the work vehicle changes suddenly, the operator tends to be in a panic. As a result, there is no danger of the work vehicle running out of control or suddenly changing the posture, which contributes to the improvement of the stability and safety of the machine.

[0048]

The present invention is configured as described above.
The following effects are obtained.

That is, as set forth in claim 1, there is provided a hydraulically driven continuously variable transmission mechanism that travels while changing the speed by a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. In the working vehicle, a means for detecting a steering angle, a means for detecting a traveling speed, a means for setting a traveling speed, and a speed changing means for a continuously variable transmission mechanism are connected to a control means and a control means, When the steering angle exceeds the set angle, the continuously variable transmission is automatically decelerated, so that proper speed reduction can be performed while maintaining the driving force required for work, and stable running is possible. It is.

According to a second aspect of the present invention, a work provided with a hydraulically driven continuously variable transmission mechanism that travels at a variable speed by means of a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. In the vehicle, a means for detecting a steering angle, a means for detecting a body attitude, a means for detecting a traveling speed, a means for setting a traveling speed, and a speed changing means of a continuously variable transmission mechanism are connected to a control means. Then, by automatically decelerating to a predetermined speed from the detected traveling speed, the attitude of the machine and the steering angle, a speed change at the time of turning without generating a shock can be performed. It can be obtained without depending on the change of the gear position and the engine speed, and the vehicle can turn at the optimum speed.

As described in claim 3, from the deceleration state,
When returning to the vehicle speed set by the main shift lever and the auxiliary shift lever, the control means controlled the return speed to the set vehicle speed to gradually increase, so that the operator did not perform any special operation. Therefore, the vehicle speed is restored at an appropriate return speed, and the operation burden on the operator can be reduced.

According to a fourth aspect of the present invention, the degree of instability is calculated from the attitude of the vehicle, the steering angle and the vehicle speed, and if the degree of instability is equal to or greater than a set value, the traveling drive is automatically stopped. Since the control is performed, even in an emergency or the like, the work vehicle does not suddenly change its posture, and it is possible to provide a safety mechanism that improves the stability and safety of the machine and avoids danger.

[Brief description of the drawings]

FIG. 1 is a left side view of a tractor equipped with the automatic transmission mechanism of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a side sectional view of a transmission case.

FIG. 4 is a skeleton diagram showing a drive transmission mechanism.

FIG. 5 is a side view of a main transmission lever mounting portion.

FIG. 6 is a side view of a sub-transmission lever mounting portion.

FIG. 7 is a side view of a transmission section of the transmission case.

FIG. 8 is a partially enlarged view of FIG.

FIG. 9 is a hydraulic circuit diagram.

FIG. 10 is a side view of a turning angle reduction switch mounting portion.

FIG. 11 is a partially enlarged view of FIG.

FIG. 12 is a side view of a connection portion between a gear case and a pitman arm.

FIG. 13 is a front view of a cutting angle sensor mounting portion.

FIG. 14 is a side view of the same.

FIG. 15 is a side view of a mounting portion of the inclination deceleration sensor.

FIG. 16 is a control block diagram.

FIG. 17 is a flowchart.

FIG. 18 is a flowchart.

[Explanation of symbols]

 2 Engine 16 Work implement mounting device 17 Brake pedal 17L Left pedal 17R Right pedal 23 HST 51 Hydraulic pump 52 Hydraulic motor 53 Movable swash plate 67 Hydraulic cylinder 61 Trunnion shaft 88 Connecting plate 96 Main machine left / right angle sensor 97 Main machine front / rear angle sensor 109 Work implement control controller 110 Travel control controller 111 Main shift lever sensor 112 Axle speed sensor 113 Engine speed sensor 114 HST pressure sensor 115 HST pressure sensor 116 Secondary shift position sensor 124 Secondary shift position sensor 139

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Hagiwara 1-1-1, Ishiba, Matsumoto-shi, Nagano Prefecture Inside the Matsumoto Plant of Shibaura Machinery Co., Ltd. (72) Inventor Tetsuo Kubota 1-1-1, Ishiba, Matsumoto-shi, Nagano Prefecture No. Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto Factory F-term (reference) DA23 DA26 EA05

Claims (4)

[Claims] 1. A work vehicle equipped with a hydraulically driven continuously variable transmission mechanism that travels while changing the speed by a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. A means for detecting the angle, a means for detecting the traveling speed, a means for setting the traveling speed, and a speed changing means for the continuously variable transmission mechanism are connected to the control means, and when the steering angle becomes equal to or larger than the set angle, An automatic transmission mechanism for a work vehicle, wherein the continuously variable transmission mechanism is automatically decelerated. 2. A work vehicle equipped with a hydraulically driven continuously variable transmission mechanism that travels at a variable speed by means of a hydraulic continuously variable transmission having a variable displacement hydraulic pump and a fixed displacement hydraulic motor. A means for detecting an angle, a means for detecting a body posture, a means for detecting a traveling speed, a means for setting a traveling speed, and a speed changing means for a continuously variable transmission mechanism are connected to a control means, and the detected An automatic transmission mechanism for a work vehicle, which automatically reduces a speed to a predetermined speed based on a traveling speed, a posture of the machine and a steering angle. 3. When returning to the vehicle speed set by the main shift lever and the auxiliary shift lever from the deceleration state, the control means controls the return speed to the set vehicle speed to be gradually increased. The automatic transmission mechanism for a work vehicle according to claim 1 or 2, wherein 4. An instability is calculated from an attitude of the machine, a steering angle and a vehicle speed, and when the instability is equal to or greater than a set value, the driving of the vehicle is automatically stopped. The automatic transmission mechanism for a working vehicle according to claim 1 or 2, wherein