JPS628656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a traveling speed control device for automatically controlling the traveling speed of a traveling working vehicle such as an agricultural tractor according to the work load.

That is, for example, in an agricultural tractor that is driven while towing a working machine such as a rotary tiller and performing tasks such as plowing with the working machine, the machine running speed is adjusted depending on whether the load applied to the working machine is small or large. Unless you increase or decrease the amount, it is not possible to perform work under stable conditions, but this invention
In such agricultural tractors, etc., which are equipped with a hydraulic clutch type transmission for changing the running power, the presence of the hydraulic clutch type transmission is skillfully utilized to adjust the machine's running according to the work load. A new traveling speed control device that automatically controls the speed and has a simple structure that can change and control the aircraft traveling speed as necessary regardless of the workload. This is what we are trying to provide.

In order to solve the problems of the invention, the present invention takes the following technical measures in a vehicle equipped with a hydraulic clutch type transmission 14 for changing driving power as illustrated in FIG.

First, as illustrated in FIG. 3, the present invention includes a manually operated switching valve 41 that switches and controls the supply and discharge of hydraulic oil to the plurality of hydraulic clutches 32, 33, 34, and 35 in the hydraulic clutch type transmission 14. , selectively operating the plurality of hydraulic clutches 32, 33, 34 of the forward gear stage by switching and controlling the supply and discharge of hydraulic oil to the plurality of hydraulic clutches 32, 33, 34 of the forward gear stage in the hydraulic clutch type transmission 14; An auto control valve 43 is provided to control the operation. That is, in the illustrated example, three hydraulic clutches for forward gears are provided, whereas the auto control valve 43 is provided with three hydraulic clutches 32, 3.
Hydraulic oil is supplied to each one of the hydraulic clutches 3 and 34, and hydraulic oil is discharged from the other two hydraulic clutches, thereby connecting the three hydraulic clutches 32, 33, and 3.
Three positions F in which 4 is selectively activated
, F, and F.

And this invention is an auto control valve 4
3 is automatically displaced according to the magnitude of the work machine load to obtain a vehicle forward speed commensurate with the work machine load. However, when automatically controlling the vehicle speed, the manually operated switching valve 41 displaces the auto control valve 43. The switching valve 41 and the auto control valve are designed to prevent the automatic control valve 43 from interfering with manual vehicle speed control when manually controlling the vehicle speed using the manually operated switching valve 41. 43 and 43, the following positions will be established respectively.

That is, as similarly illustrated in FIG.
The clutch ports for the hydraulic clutches 32, 33, and 34 of the forward gear in the hydraulic clutch type transmission 14 are all blocked, and the clutch ports for the hydraulic clutch 35 of the reverse gear are connected to the tank. Auto control position AUTO to communicate with port
shall be attached. Therefore, automatic control of the vehicle speed by the auto control valve 43 is performed by moving the switching valve 41 to the auto control position AUTO so that the hydraulic oil from the hydraulic pump 37 is supplied to the pump port P of the valve 43. However, since the clutch ports for the forward gear hydraulic clutches 32, 33, and 34 are all blocked when the same position is AUTO, the forward gear hydraulic clutches 32, 33, and 34 are exclusively used as auto control valves. The supply and discharge of hydraulic oil is controlled only by the switching valve 41.
In the automatic control position AUTO, the clutch port for the hydraulic clutch 35 in the reverse gear is connected to the tank port, so the hydraulic clutch 35 in the reverse gear remains inactive, and the automatic control is activated. Valve 43
The hydraulic clutches 32, 33, 3 of the forward gear are
The switching valve 41 does not cause any trouble when the vehicle speed is automatically controlled by selectively operating the switching valve 4.

Next, as illustrated in FIG. 3, the auto control valve 43 is provided with a function deletion position number that cuts off communication between all the clutch ports C ₁ , C ₂ , C ₃ of the valve 43 and the tank port T. . Therefore, if the auto control valve 43 is moved to the same function deletion position No., the valve 43 will no longer be able to discharge hydraulic oil from the hydraulic clutches 32, 33, 34 of the forward gear, and the auto control valve 43 will not operate. Although the oil supply and discharge control function is eliminated, the automatic control valve 43 functions because the structure is such that such function can be eliminated by stopping the discharge of hydraulic oil from the hydraulic clutches 32, 33, and 34 of the forward gear. In the state moved to erase position No., not only the hydraulic clutch 35 of the reverse gear but also the hydraulic clutches 32, 3 of the forward gear
3 and 34 are also exclusively manually operated switching valves 4.
Hydraulic oil supply and discharge control is carried out only by the hydraulic clutch 32-1 by the switching valve 41.
There is no problem in selectively operating 35.
In the illustrated example, when the vehicle speed is controlled by the switching valve 41, hydraulic oil is supplied to and discharged from one hydraulic clutch 34 in the forward gear stage through the auto control valve 43 located at the function erase position No. Although the structure is simplified, it is of course possible to connect the switching valve 41 and the hydraulic clutch 34 without going through the auto control valve 43.

In addition to providing the above-mentioned positions AUTO and No to the switching valve 41 and the auto control valve 43, the present invention also provides load detection means 49, 61-68 (Fig. 4) for detecting the work machine load, The auto control valve 43 is connected to the load detection means 4.
9, 61-68, the auto control valve 43 is connected so as to be displaced to a position where the hydraulic clutch of a lower speed gear is actuated as the load of the working machine increases, and the above-mentioned load detection means 49, 61- 68 and auto control valve 4
3, and a displacement means 47 for moving the auto control valve 43 to the function erasing position No. by disconnection by the disconnection means 41.

In the example shown above, the load detection means 49, 61-68
As will be described later, the system is configured to mechanically detect the rotation speed of the PTO shaft used to drive the work equipment and output the detection result as a hydraulic pressure value. A link for supporting a work machine, such as a load detection means equipped with a tacho generator that outputs a voltage value, or a load detection means used to detect the work machine load for draft control in agricultural tractors. It is also possible to use a load detection means that detects the work machine load from the load applied to the mechanism and outputs the detection result as the amount of link displacement. In addition, in the illustrated example, since the load detection means 49, 61-68 outputs the detection result as a hydraulic pressure value as described above, the auto control valve 43 is connected to the load detection means 49, 61-68. On the other hand, the structure is such that the displacement of the auto control valve 43 is obtained by hydraulic pressure by connecting the auto control valve 43 with a hydraulic circuit. It is also possible to rely on a connection mechanism equipped with an electromagnetic plunger to displace the load detection means, or a linkage mechanism that transmits the mechanical displacement of the output member of the load detection means to the auto control valve 43.

Furthermore, in the example shown, the auto control valve 43
As described above, since the displacement of
At the positions N, F ₁ , F ₂ , F ₃ , R) shown in the figure, the hydraulic circuit 50 for displacing the auto control valve 43
is connected to an oil tank to have a function of no longer applying hydraulic pressure for displacement to the auto control valve 43, thereby connecting the switching valve 41 to the load detecting means 49, 61-68 and the auto control valve 43. It also serves as the above-mentioned manually operated type disconnection means for disconnecting the valves 43, and also serves as a displacement means for moving the auto control valve 43 to the function deletion position No. by disconnection by the connection disconnection means 41. is spring 4
7 is provided. However, in a structure in which the load detection means and the auto control valve 43 are connected by an electrical connection means, the manually operated disconnection means is used as an electric circuit changeover switch, and the auto control valve 43 is moved to the function deletion position No. The displacement means can be an electromagnetic plunger that operates to move the valve 43 to the above position No. by switching the electric circuit by the changeover switch, or a mechanical connection means can be used between the load detection means and the auto control valve 43. In the case of a structure in which the connection is made by manually operating the disconnection means, for example, the connection link mechanism between the load detection means and the auto control valve 43 is displaced so that the auto control valve 43 is moved to the function deletion position No. It shall be equipped with an operating lever that locks with the
can.

According to the traveling speed control device of the present invention configured as described above, when a traveling work vehicle such as a tractor performs work such as plowing, the manually operated switching valve 41 is set to the auto control position.
If you shift to AUTO and proceed with the work, the auto control valve 43 will be automatically displaced to operate the hydraulic clutch at a lower gear as the load increases, depending on the load on the work machine. Automatic vehicle speed control is performed in which the vehicle speed is reduced as the value increases. In addition, when it is preferable for the operator to change the vehicle speed as appropriate rather than changing the vehicle speed frequently due to field conditions, or when driving on the road, the auto control valve 43 is activated to detect the load. The operator can freely change the vehicle speed by using the manually operated switching valve 41 in a state where the vehicle has been moved to the function deletion position No. by disconnecting the vehicle from the vehicle.

To explain the embodiment, as shown in FIG. 1, an engine 1 is mounted on the front of the aircraft body, and the engine 1 drives the left and right rear wheels 2 to rotate the aircraft, and the engine 1 rotates the left and right rear wheels 2. In the illustrated case, the operator seated in the passenger seat 3 rotates the left and right front wheels 5 using the steering handle 4, and is connected to the rear of the aircraft by a coupling device 6 that can be rotated up and down. The engine 1 drives the work implement 7, which is a rotary tiller and is raised and lowered between the illustrated working position and an upper standby position by a hydraulic lift device equipped with a lift arm 8.
In an agricultural tractor, the PTO shaft 9 of this machine is rotationally driven by a flexible transmission shaft 10 and is interlocked with the driving part of the work implement 7. It has been implemented.

That is, as shown in FIG. 2, the illustrated agricultural tractor is provided with a drive shaft 12 that is interlocked and connected to the engine 1 via a main clutch 11, and between the drive shaft 12 and the rear wheels 2, A hydraulic clutch type transmission 14 disposed between the drive shaft 12 and a transmission shaft 13 parallel to the drive shaft 12; and a hollow transmission shaft 15 on the rear extension 12a of the drive shaft 12, which receives input from the transmission shaft 13. A gear transmission 17 disposed between the transmission shaft 15 and another transmission shaft 16 provided on an extension of the transmission shaft 13, and a differential transmission 18 receiving input from the other transmission shaft 16. a differential gear 18 equipped with a deflock device 19;
The left and right output shafts 18a of the differential device 18 are interlocked and connected via the left and right final gear reduction devices 20 disposed between the left and right rear wheel axles 2a, completing a traveling power transmission path, and the drive shaft 12 and PTO axis 9
Between is an intermediate shaft 21 connected to the drive shaft extension 12a and a transmission shaft 2 connected to this intermediate shaft 21.
2 and a gear type work machine power transmission device 23 disposed between the transmission shaft 22 and the PTO shaft 9, the work machine power transmission path is completed by interlocking and connecting to the PTO shaft 9. The hydraulic clutch type transmission 14 constitutes the main transmission for driving power.
Similarly _, as shown in _FIG .
5, the F ₃ speed change gear 26 and the R speed change gear 27, and the F ₁ which is loosely fitted onto the transmission shaft 13 and meshed with the corresponding speed change gears 24-27 on the drive shaft 12 either directly or via the R intermediate gear 27a. Idle gear 28, _F2 idle gear 29, _F3 idle gear 30, and R idle gear 3
1, one friction plate is attached to the clutch housing fixedly provided to the transmission shaft 13, and the other friction plate is attached to each of the above-mentioned free rotating gears 28-31, each of which is slidable only in the direction of the clutch axis. _F1 hydraulic clutch 32 supported and configured as a multi-plate type;
It has a conventional structure comprising an F ₂ hydraulic clutch 33, an F ₃ hydraulic clutch 34, and an R hydraulic clutch 35, and each idler gear 28-31 is controlled by selective operation of each hydraulic clutch 32-35. Selectively coupled to the transmission shaft 13, 1st forward speed F ₁ , 2nd forward speed
It is possible to selectively obtain a gear ratio of F ₂ , 3 forward speeds F ₃ or 1 reverse speed R. Then, the supply and discharge of hydraulic oil to and from the hydraulic clutches 32 to 35 in the hydraulic clutch type transmission 14 are controlled, and each hydraulic clutch 32, 33, 34 or 35 is selectively operated to adjust each of the above-mentioned speed ratios. As shown in FIG. 3, what is selectively obtained is the oil supply circuit 38 which runs from the oil tank 36 through the hydraulic pump 37 to the hydraulic clutches 32-35, and whose oil pressure is set by the pressure regulating valve 39. In circuit 38, passenger seat 3
A switching valve 41 as shown, which is operated by the front main shift lever 40, that is, a fully hydraulic clutch 3
A neutral position N where hydraulic oil is drained from 2-35 toward the tank circuit 42 and all hydraulic clutches 32-35 are inoperative, and one hydraulic clutch 32-3 each.
One hydraulic clutch 32, 33, 34 is supplied with oil only to one hydraulic clutch 32, 33, 34 by draining hydraulic oil from the other three hydraulic clutches toward the tank circuit 42.
This is achieved by providing a switching valve 41 having a forward first speed position F ₁ , a forward second speed position F ₂ , a forward third speed position F ₃ and a reverse first speed position R, which operate only the forward speed position F 5 .

The above configuration is normal, but the third
As shown in the figure, the switching valve 41 has one position AUTO in addition to the five positions N, F ₁ , F ₂ , F ₃ , and R.
In addition to the four ports connected to the hydraulic clutches 32-35 on the secondary side, there is one more port connected to the hydraulic clutches 32-35.
Ports D are provided. In particular, an auto control valve 43 is provided, the pump port P being connected to the connection port to the forward third speed hydraulic clutch 34 on the secondary side of the switching valve 41. In addition to the pump port P, there is an oil tank 3.
The tank port T connected to 6 and the forward hydraulic clutches 32, 33,
Three connection ports C ₁ , C ₂ , C ₃ connected to 34
The auto control valve 43 connects the pump port P to the connection port.
C ₃ , therefore the function erase position No. which connects to the hydraulic clutch 34 for the third forward speed, connects the pump port P to the connection port C ₁ and connects the connection port C ₂ ,
Auto 1st speed position F that connects C ₃ to tank port T, and auto 2nd speed position F that connects pump port P to connection port C ₂ and connects the other two connection ports C ₁ and C ₃ to tank port T. and an auto 3-speed position F that connects the pump port P to the connection port _C3 and connects the other two connection ports _C1 , _C2 , and the tank port T. . The switching valve 41 is in the AUTO position, the reverse hydraulic clutch 35 is connected to the oil tank 36 via the tank circuit 42, and the connection ports to the hydraulic clutches 32 and 33 for forward 1st speed and forward 2nd speed are blocked. And, the oil supply circuit 38
is connected to the pump port P of the auto control valve 43. The other secondary port D in the switching valve 41 is blocked only in the AUTO position of the switching valve 41, and the tank circuit 42 is blocked in other positions N, F ₁ , F ₂ , F ₃ , R.
It is assumed that it is connected to the oil tank 36 via.

As described above, when the auto control valve 43 is set to the function erase position No., the switching valve 41 is
When selectively switching the shift state to positions N, F ₁ , F ₂ , F ₃ , and R by operating the lever 40, the shift state of the hydraulic clutch type transmission 14 can be changed manually as in the conventional case, and the switching valve Position 41
When the auto control valve 43 is in the auto 1st gear position F, the hydraulic clutch 32 for forward 1st gear is activated, the hydraulic clutch 33 for 2nd forward gear in the auto 2nd gear position F is activated, and the hydraulic clutch 33 for 2nd forward gear is activated in the auto 3rd gear position. In F, the hydraulic clutches 34 for three forward speeds are selectively operated, and the switching valve 41 is set to
The following mechanism is provided to automatically change the position of the auto control valve 43 when it is set to AUTO.

That is, the auto control valve 43 is
The spool is equipped with a spool (not shown) similar to that in a typical switching valve, and the spool is connected to an adjusting screw 45 that is moved forward and backward by a screw turn by operating a handle 44, as shown in FIG. A compression spring 47 whose one end is received by a movable spring receiver 46 is used to slide and urge the spool in the direction of the function erasing position No. The following hydraulic pressure is introduced to the tip of the spool. The spool is designed to be automatically displaced by this hydraulic pressure. That is, as similarly shown in FIG. 3, a control circuit 50 is provided to which pressure oil is supplied from the oil tank 36 by a hydraulic pump 48 and the oil pressure is set by a pressure regulating valve 49. It is connected to the port D of the switching valve 41 and to a pressure oil chamber (not shown) at the tip of the spool of the auto control valve 43 via a connection circuit including a throttle 51 and an accumulator 52. Therefore, at positions N, F ₁ , F ₂ , F ₃ , and R of the switching valve 41, the port D is connected to the oil tank 36 as described above at these positions.
Since the hydraulic pressure is not established in the control circuit 50, the auto control valve 43 is held at the function erase position No. by the pressing force of the compression spring 47. However, the port D is blocked and the control circuit 50 is closed. Hydraulic pressure is established at 50,
When the switching valve 41 is in the AUTO position, the hydraulic pressure setting of the pressure regulating valve 49 is controlled and the control circuit 50
The following mechanism is provided to change the oil pressure of the auto control valve 43 and thereby control the position of the auto control valve 43.

That is, as shown in FIG. 4, the rear oil chamber 5
The hydraulic pressure of the pump port 54 acting on the pump port 54 is moved forward as shown in the imaginary line against the spring force of the pressure setting compression spring 55, thereby communicating the pump port 54 with the tank port 56 to perform a relief operation. In the above pressure regulating valve 49 including the valve body 57, the pressure setting compression spring 55
is received at its tip by a movable spring receiver 59 that can freely slide forward and backward within the valve case 58, and is connected to the compression spring 55 and another compression spring 6 provided within the valve case 58.
On the rear surface of the movable spring receiver 59, which is biased to move in the backward direction by the valve 0, is brought into contact with a retractable rod 61 which is supported so as to be freely retractable and has its tip facing inside the valve case 58. A hollow shaft 62 is provided on the advancing/retracting rod 61 so as to freely rotate.
A gear 63 fixed to the PTO shaft 9 is meshed with a gear 64 fixed to the PTO shaft 9, so that the hollow shaft 62 is rotated as the PTO shaft 9 rotates. Also, a flange 62a formed at the tip of the hollow shaft 62
A plurality of curved arms 67 are supported rotatably around a pin 66 by a bracket 65 protruding from the front surface of the arm, and a weight 68 is fixed to one end of each curved arm 67. Curved arm 6
The other end of 7 is applied to the back surface of a large diameter flange 61a formed in the middle of the reciprocating rod 61, and the centrifugal force acting on the weight 68 as the hollow shaft 62 rotates causes the weight 68 to be displaced in the outer circumferential direction. The curved arm 67 is arrow S
When the curved arm 67 is rotated in the direction, the collar 61 is attached to the curved arm 67.
The retractable lever 61 is designed so that it can be moved forward by pressing a. As described above, the advancing/retracting rod 61 which is biased to move in the backward direction via the movable spring receiver 59 by the compression springs 55 and 60 is as follows.
A position is taken where the centrifugal force acting on the weight 68 in proportion to the rotational speed of the PTO shaft 9 and the forces of the springs 55 and 60 described above are balanced, and the movable spring receiver 59 is positioned in accordance with the position of the advance/retreat rod 61. The higher the rotation speed of the PTO shaft 9, the higher the set oil pressure of the pressure regulating valve 49, and conversely, the lower the rotation speed of the PTO shaft 9. The set oil pressure becomes low. Therefore,
Control circuit 5 when switching valve 41 is in position AUTO
The hydraulic pressure that becomes 0 is due to an increase in the load on the work machine 7.
The rotation speed of the PTO shaft 9 is so low as to be reduced.
Conversely, as the load on the work machine 7 decreases and the rotation speed of the PTO shaft 9 increases, the rotation speed of the PTO shaft 9 increases. Due to the balance between the hydraulic pressure of the valve 43 and the force of the compression spring 47 attached to the valve 43, the auto control valve 43 or its spool is in the auto 1st speed position F, which is the rightmost position in the figure, in the high range of the work machine 7 load above a certain value. In the middle range of the work machine load, the auto control valve 43 or its spool takes the intermediate auto 2nd speed position F, and in the low range of the work machine 7 load, the auto control valve 43 or its spool takes the auto position on the left end side in the figure. The spring constants of the compression spring 55 of the pressure regulating valve 49 and the compression spring 47 of the auto control valve 43 are set so that the third speed position F is taken.

In the illustrated case, as shown in FIG. 3, a tank circuit 69 is provided to connect the control circuit 50 toward the oil tank 36,
Insert an unload valve 70 as shown in the figure, which has an inoperative position in which it blocks the tank circuit 69 and an unload operative position in which it unblocks the block and unloads the hydraulic pressure in the control circuit 50. , the lift arm 8 is attached to the unload valve 70 which is normally in an inoperative position energized by a compression spring 71, and when the lift arm 8 is brought to the lift position of the working machine 7, the unload valve 70 is unloaded. The actuating arm 72 and the roller 72a at its tip are connected to each other so as to assume the actuating position. Therefore, when the working machine 7 is lifted to the upper standby position, the auto control valve 43 is automatically brought to the function deletion position No. by hydraulic unloading of the control circuit 50.

The gear transmission 17 disposed in the running power transmission path is fixed on the hollow transmission shaft 15, which receives input from the transmission shaft 13 through meshing of gears 73 and 74, as shown in FIG. A plurality of transmission gears 75, 76, 77 and another transmission gear 79 on the drive shaft extension 12a, which is input from the hollow transmission shaft 15 through the gear reduction mechanism 78, are spline-fitted to the transmission shaft 16. a plurality of shift gears 80,
81, 82, and a dog clutch 83 interposed between the transmission shafts 13, 16. By selective sliding displacement of the shift gears 80-82 on the transmission shaft 16, 1st speed (very low speed) when gears 79 and 90 mesh, 2nd speed when gears 75 and 80 mesh, 3rd speed when gears 76 and 81 mesh, 4th speed when gears 77 and 82 mesh, and meshing clutch 8
Through the direct connection between the shafts 13 and 16, a five-speed gear ratio can be obtained. Further, the above-mentioned PTO transmission 23 includes a plurality of speed change gears 84, 85, 86, 87 fixed on the transmission shaft 22, as similarly shown in FIG.
A plurality of shift gears 88, 89, 90 spline-fitted to the PTO shaft 9, and an idle gear 91 on the PTO shaft 9, and the speed change gear 8 on the transmission shaft 22.
Idle gear 91 meshed with 4 and the shift gear 8
8 and a dog clutch 92 interposed between the PTO shaft 9 and the shift gears 88 to 90.
1st speed by actuation of dog clutch 92, gears 85, 88
A gear ratio of 2nd speed can be obtained by meshing between gears 86 and 89, 3rd speed by meshing between gears 87 and 90, and 4th gear by meshing between gears 87 and 90. In FIG. 2, reference numeral 93 denotes left and right brakes for the left and right rear wheels 2, which are arranged at the ends of the differential output shaft 18a.

The traveling speed control device shown in FIG. 1-4 is configured as described above, so that when cultivating in the field, the speed change ratio and the working machine 7 are controlled by the gear transmission 17, which is the traveling power sub-transmission device. PTO for power shifting
If the speed change ratio of the transmission device 23 is set appropriately according to the field conditions, etc., and the changeover valve 41 is set to the AUTO position and the work is proceeded, the changeover valve 41 will be set automatically according to the magnitude of the load acting on the work equipment 7. When the load is high, the auto control valve 43 takes the auto 1st gear position F and the hydraulic clutch 3 for forward 1st gear is activated.
2 is activated and the aircraft is made to travel at the forward first speed _F1 , and at an intermediate load, the auto control valve 43 is set to the auto second speed position F, and the hydraulic clutch 33 for forward second speed is activated, causing the aircraft to move forward. The aircraft is made to travel at the speed of _2nd gear F2, and when the load is low, the auto control valve 43 takes the auto 3rd gear position F, and the hydraulic clutch 34 for forward 3rd gear is operated, causing the aircraft to travel at the speed of 3rd forward gear _F3 . In this way, the vehicle speed is automatically controlled depending on the magnitude of the load on the working machine 7, so that stable and constant tilling work can be carried out at all times. When the model of the working machine 7 towed by the illustrated agricultural tractor is changed, or when the field conditions change drastically, the spring force of the compression spring 47 of the auto control valve 43 can be adjusted by operating the handle 44. Change and adjust work equipment 7 load auto control valve 43
The relationship with the position can be adjusted as appropriate. From this state, the switching valve 41 is moved to another position N,
When shifting to F ₁ , F ₂ , F ₃ , R, the auto control valve 43 is unloaded by hydraulic pressure of the control circuit 50 via port D of the switching valve 41.
is automatically displaced to the function deletion position No. As in the normal case, the hydraulic clutch type transmission 14 can be shifted by manual operation of the switching valve 41, and the work implement 7 is moved to the standby position. Even in the lifted state, the unload valve 70 is activated.
When the control circuit 50 is hydraulically unloaded, the auto control valve 43 automatically moves to the function erase position.
Since the shift is made to No., the hydraulic clutch type transmission 14 can be manually shifted in the same manner.

According to this invention, when proceeding with work such as plowing with a traveling work vehicle such as an agricultural tractor with the manually operated switching valve 41 moved to the auto control position AUTO, the auto control valve 41 is moved to the auto control position AUTO.
Accordingly, the traveling speed of the machine is automatically changed and controlled in a direction to keep the work constant according to the magnitude of the load on the working machine such as a power tiller, and work can be automatically performed under stable constant conditions. And load detection means 4
9, 61-68 and auto control valve 43
By cutting off the connection between the two and moving the auto control valve 43 to the function deletion position No., the machine running speed can be freely changed and controlled by operating the manually operated switching valve 41. When performing work where a constant work result can be obtained by keeping the speed constant, or rather than having to change the vehicle speed frequently automatically depending on field conditions, the operator can change the machine running speed as appropriate depending on the work conditions. While doing work, when traveling on the road, the machine's running speed can be changed freely regardless of the workload.

Further, in this invention, a hydraulic pump 37 for supplying hydraulic oil is connected to the switching valve 41 for manual control of the vehicle speed in the direction of the auto control valve 43, and hydraulic oil is supplied from the hydraulic clutches 32, 33, 34 of the forward gear stage. Discharge is prevented and the hydraulic oil is discharged from the hydraulic clutch 35 of the reverse gear, that is, the hydraulic clutch 35 of the reverse gear is discharged.
The auto control valve 43 for automatic vehicle speed control is equipped with an auto control position AUTO that maintains the non-operating state of 5.
A function erasing position number is provided to prevent direct discharge of hydraulic fluid through the auto control valve 43, and when the vehicle speed is automatically controlled by the auto control valve 43, the multiple hydraulic clutches 32, 33, and 34 of the forward gear are selectively operated. Hydraulic oil supply and discharge control by the control valve 43 is not inhibited, and on the other hand, when the vehicle speed is artificially controlled by the switching valve 41, the auto control valve 43 controls the hydraulic clutch 32 of the forward gear,
Two types of valves 41 and 34 are used for artificial control and automatic control of the vehicle speed, provided that the hydraulic oil is not discharged from the switching valves 33 and 34 and the control of supply and discharge of hydraulic oil by the switching valve 41 is not obstructed. 43, the desired vehicle speed control can be achieved with a simple structure.

[Brief explanation of the drawing]

FIG. 1 is a side view of an agricultural tractor equipped with an embodiment of the present invention, FIG. 2 is a mechanical diagram of the power transmission mechanism in the agricultural tractor, FIG. 3 is a circuit diagram of the hydraulic circuit of the embodiment, and FIG. The figure is a longitudinal sectional view of only the main parts of the same embodiment. 1...Engine, 7...Work equipment, 9...PTO
Shaft, 14... Hydraulic clutch type transmission, 32, 3
3, 34, 35...Hydraulic clutch, 41...Switching valve, 43...Auto control valve, 47...
... Compression spring, 48 ... Hydraulic pump, 49 ... Pressure regulating valve, 50 ... Control circuit, 55 ... Compression spring for pressure setting, 59 ... Movable spring receiver, 61 ... Advance/retreat rod, 62 ... Hollow shaft, 67...Curved arm, 6
8... Weight.

Claims (1)

[Claims] 1. In an agricultural tractor or the like equipped with a hydraulic clutch type transmission for changing traveling power, a manual operation for switching and controlling the supply and discharge of hydraulic oil to the plurality of hydraulic clutches 32, 33, 34, and 35 in the hydraulic clutch type transmission 14. In addition to the type switching valve 41, the hydraulic clutches 32, 33, and 34 of the forward gear in the hydraulic clutch type transmission 14 are selectively controlled to supply and discharge hydraulic oil to the multiple hydraulic clutches 32, 33, and 34 of the forward gear. 33 and 34 are provided, and the switching valve 41 is located at an auto control position ( AUTO) and the hydraulic clutches 32, 3 of the forward gear in the hydraulic clutch type transmission 14.
All the clutch ports for hydraulic clutches 35 and 34 in the reverse gear are blocked, and the clutch port for the hydraulic clutch 35 in the reverse gear is provided with an auto control position (AUTO) that communicates with the tank port. A function erasing position No. is added to cut off the communication between all clutch ports C ₁ , C ₂ , C ₃ and the tank port T, and a load detection means 4 for detecting the work machine load is provided.
9, 61-68 are provided, and the auto control valve 43 is connected to the load detecting means 49, 61-68.
On the other hand, the auto control valve 43 is connected so as to be displaced to a position where the hydraulic clutch of the lower gear is operated as the load of the working machine increases, and the above-mentioned load detection means 49, 61-6 are connected.
8 and the auto control valve 43, and a displacement means 47 for moving the auto control valve 43 to the function erasing position No. by the disconnection by the disconnection means 41. The driving speed control device is characterized by the following features: