JPS6157212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel agricultural tractor equipped with a mechanism that automatically controls the traveling speed of the machine according to the work load.

Draft control is load control that is commonly performed on agricultural tractors. In other words, when the traction resistance or load of a rotary tiller, plow, or other work equipment being towed by an agricultural tractor becomes excessive, the work equipment is automatically controlled by a hydraulic lift device. The control is to raise the traction load by an appropriate amount and keep the traction load constant.
This is a load control method that protects the work equipment from damage by keeping the load constant, but at the expense of maintaining constant work results such as plowing depth. Therefore, the applicant of this application first developed a control method that balances the load of the work equipment and the vehicle speed as a load control method that keeps the work result constant while preventing the work equipment from being overloaded, and filed a patent application (patent application). Akira
52-78420 and Japanese Patent Application Laid-Open No. 1983-12070).

This control system allows for easy gear change control because the gears can be switched and controlled by valve displacement.In agricultural tractors equipped with a hydraulic clutch type transmission, it is possible to supply and drain hydraulic oil to multiple hydraulic clutches in the hydraulic clutch type transmission. In addition to the manually operated control valve, an auto control valve is provided to automatically control the supply and discharge of hydraulic fluid to multiple hydraulic clutches in forward gears in a hydraulic clutch type transmission. The load and vehicle speed are balanced by displacement according to the load detected by the sensor. The manually operated control valve is equipped with an auto control position that guides hydraulic fluid to the primary side of the auto control valve, and the auto control valve also cancels its automatic control function and allows the manually operated control valve to control the speed change. A function release position is provided to enable this function.

Therefore, when performing work such as plowing, where it is desirable to protect the work equipment from overload while maintaining a constant work result, the manually operated control valve is moved to the auto control position and the auto control is activated. The vehicle speed in the forward direction of the vehicle is automatically controlled by a valve to a value commensurate with the load of the work equipment, and rather than having to change the vehicle speed frequently when driving on the road or depending on field conditions, the operator can When it is desired to change the vehicle speed depending on the working condition, the auto control valve is moved to the function release position and the vehicle speed is changed using the manually operated control valve.

The prior art described above has a special auto control valve for automatic vehicle speed control, and a manually operated control valve with the above auto control position, so that the structure of the valve is not a normal human control valve. Since it is more complex than an operated control valve, there remains a problem in terms of production cost.

Therefore, the present invention provides a control valve for automatic vehicle speed control in a structure that balances the work machine load and vehicle speed using a hydraulic clutch type transmission device that can easily control the speed change, similar to the prior art described above. The present invention aims to provide a new agricultural tractor that eliminates the need for a separate control valve and also avoids complicating the structure of the control valve itself.

Regarding the illustrated embodiment, the structure of the agricultural tractor according to the present invention will be explained. In the first embodiment shown in FIGS. 1-6, the illustrated agricultural tractor is, as usual, As shown in the figure, an engine 1 is mounted on the front of the aircraft, and the engine 1 drives the left and right rear wheels 2 to rotate the aircraft, and the aircraft is steered by sitting on a passenger seat 3. A working machine 7, which in the illustrated case is a rotary tiller, is operated by an operator by turning left and right front wheels 5 using a control handle 4, and is connected to the rear part of the machine by a coupling device 6 that can be moved up and down. The PTO shaft 9 of this machine, which is rotatably driven by the engine 1, drives the work implement 7, which 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. It is configured to perform this by interlockingly connecting to the drive section of the working machine 7 via a flexible transmission shaft 10.

As shown in FIG. 2, the illustrated agricultural tractor is provided with a drive shaft 12 that is interlocked with the engine 1 via a main clutch 11. A hydraulic clutch type transmission 14 disposed between the shaft 12 and a transmission shaft 13 parallel thereto, and a rear extension 12 of the drive shaft 12.
A gear transmission device which is a hollow transmission shaft 15 on a and is disposed between the hollow transmission shaft 15 which receives input from the transmission shaft 13 and another transmission shaft 16 provided on an extension line of the transmission shaft 13. 17 and the other transmission shaft 1 mentioned above.
A differential device 18 which is input from 6 and is equipped with a deflock device 19, the left and right output shafts 18a of this differential device 18, and the left and right rear wheel axles 2
They are interlocked and connected via the left and right final gear reduction gears 20 disposed between the two wheels, thereby completing a traveling power transmission path. Also, between the drive shaft 12 and the PTO shaft 9,
Intermediate shaft 21 connected to the drive shaft extension 12a
and a transmission shaft 22 connected to this intermediate shaft 21,
The transmission shaft 22 and a PTO transmission device 23 for changing the power of the work machine disposed between the power transmission shaft 22 and the PTO shaft 9 are interlocked to complete a work machine power transmission path to the PTO shaft 9.

The hydraulic clutch type transmission 14, which constitutes the main transmission for driving power, has an _F1 speed change gear 2 fixed to the drive shaft 12, as similarly shown in FIG.
4, the _F2 speed change gear 25, the _F3 speed change gear 26, and the R speed change gear 27, and the corresponding speed change gears 24-27 on the drive shaft 12, which are loosely fitted to the transmission shaft 13, directly or R intermediate gear 27a. _F1 idler gear 28, _F2 idler gear 29, and _F3 idler gear 30 are intermeshed with each other.
and R free rotating gear 31, and one friction plate is attached to the clutch housing fixed to the transmission shaft 13,
In addition, the _F1 hydraulic clutch 32 and _F2 hydraulic clutch 33 are configured as multi-plate type in which each of the free rotating gears 28-31 supports the other friction plate so as to be able to slide freely along the clutch axis direction. , _F3 hydraulic clutch 34 and R hydraulic clutch 35, each idler gear 2 is selectively operated by each hydraulic clutch 32-35.
8-31 is selectively connected to the transmission shaft 13, and the forward movement 1
Speed _F1 , forward 2nd speed _F2 , forward 3rd speed _F3 or reverse 1st speed R
It is now possible to selectively obtain the following gear ratios. And this hydraulic clutch type transmission 1
4, the supply and discharge of hydraulic oil to and from the hydraulic clutches 32 to 35 are controlled, and each hydraulic clutch 32, 33, 3
In order to selectively operate the clutches 4 or 35 to selectively obtain the respective gear ratios described above, as shown in FIG. 38, and a tank circuit 40 that discharges the hydraulic oil from the direction of the hydraulic clutches 32 to 35 to the oil tank 36.
Two position solenoid valves 41 and 42 are provided. Among these, the solenoid valve 41 on the front stage has two ports on the primary side, a pump port and a tank port, as shown in the figure.
The valve is configured as a 5-port switching valve, which has one oil supply port in addition to two clutch ports on the secondary side, and the oil supply port is connected to the pump of the solenoid valve 42 on the downstream side. connect to the port,
It has a function of connecting the oil supply circuit 39 toward the rear solenoid valve 42 at the neutral position N. The solenoid valve 42 on the rear stage side is a four-port valve having a pump port and a tank port on the primary side, and two clutch ports on the secondary side. The 2 clutch port of the solenoid valve 41 is the F ₂ hydraulic clutch 3
3 and _F4 hydraulic clutch 34,
This solenoid valve 41 is displaced by the excitation of the solenoid 41a to supply oil to the _F2 hydraulic clutch 33, and to the forward second speed position _F2 , which is displaced by the excitation of the solenoid 41b to supply oil to the _F3 hydraulic clutch 34. In addition to the neutral position N, a third forward speed position _F3 is provided. Further, the two clutch ports of the solenoid valve 42 are connected to the _F1 hydraulic clutch 32 and the R hydraulic clutch 35, and this solenoid valve 42 is displaced by the excitation of the solenoid 42a to supply oil to the _F1 hydraulic clutch 32. Forward 1st gear position F ₁ and
In addition to the neutral position N, there is also a reverse first speed position R which is displaced by the excitation of the solenoid 42b and supplies oil to the R hydraulic clutch 35. In addition, solenoid valve 4
The oil supply port 1 is designed to be blocked at each operating position F ₂ , F ₃ of the solenoid valve 41 .

As described above, the control valves that control the supply and discharge of hydraulic oil to the plurality of hydraulic clutches 32-35 in the hydraulic clutch type transmission 14 control the hydraulic oil supply and discharge in series with each other in the oil supply direction to the plurality of hydraulic clutches 32-35. It is composed of two connected three-position solenoid valves 41, 42, and solenoids 42a, 41a, 41b, 42b.
The solenoid valves 41 and 42 are moved to each operating position by selective excitation of
By selectively shifting to F ₁ , F ₂ , F ₃ or R, the gear ratio is changed by the hydraulic clutch type transmission 14.

Next, as shown in FIG. 4, the crankshaft of the engine 1 and the
A load detection means is provided for detecting the work machine load by detecting the rotational speed of any one transmission shaft (the transmission shaft 22 in the illustrated case) including the PTO shaft 9. This load detection means has a gear 4 on the transmission shaft 22.
3, 44 Hollow rotating shaft 4 interlocked and connected by transmission
5 is provided on the reciprocating rod 46, and is rotatably supported around the pin 48 by a bracket 47 protruding from the front surface of a flange 45a formed at the tip of the hollow rotating shaft 45, so that a plurality of curved arms 49 are supported. A weight 50 is fixed to one end of the curved arm 49. The other end of each curved arm 49 is formed in the middle of the advancing/retracting rod 46 with a large diameter collar portion 46.
a, and as the hollow rotating shaft 45 rotates, the weight 5
When the curved arm 49, on which the weight 50 is displaced in the outer circumferential direction due to the centrifugal force acting at zero, rotates in the direction of arrow A, the collar portion 46a is pushed by the curved arm 49, and the advancing and retracting rod 46 moves forward and backward. The rod 46 is designed to be moved forward against the force of the compression spring 52 between the spring receiving plate 51 on the outer periphery of the rod 46 and the flange 46a that urges the rod 46 backward. Therefore, the reciprocating rod 46 takes a position where the centrifugal force acting on the weight 50 and the spring force of the compression spring 52 are balanced, and since the above centrifugal force is proportional to the rotation speed of the transmission shaft 22, , the number of revolutions of the transmission shaft 22, and therefore the work machine load, are detected at the forward and backward positions of the advance/retreat lever 46. A rotary switch device 56 is shown in FIGS. 4 and 5, and is equipped with a rotating shaft 55 on which a pinion 54 is fitted. It is set up like this. The rotary switch device 56 has a movable contact that is displaced by the rotational displacement of the rotary shaft 55, and gradually changes the working machine load L ₁ -L ₂ , L 2 -L 3 , L ₂ -L ₃ to a certain range.
Three sensor switches SF _' 1 , SF' ₂ , SF _' 3 detect L 3 _- L ₄ (L ₁ > L ₂ > L ₃ > L ₄ ) by on operation.
(Figure 6). Therefore, in a constant high range of work equipment load L ₁ - L ₂ , the sensor switch
SF' ₁ is on, sensor switch SF' ₂ is on in the range L ₂ - _{L 3} where the work machine load is medium, and sensor switch SF' ₃ is on in a certain range where the work machine load is relatively low. It's on. The gear 44 is capable of sliding displacement on the hollow rotating shaft 46, and when the gear 44 is displaced to disengage from the gear 43 and stop the rotation of the hollow rotating shaft 45, the gear 44 moves forward or backward. All sensors are switched by retracting the rod 46.
The arrangement is such that a non-active state of the load detection means is obtained in which SF' ₁ , SF' ₂ and SF' ₃ remain off.

Next, the solenoids 42a, 41a, 41
b, 42b are selectively excited to activate the solenoid valves 41, 42b.
In order to selectively displace 42 into active positions F ₁ , F ₂ , F ₃ , R, an electrical control circuit as shown in FIG. 6 is provided. This electric control circuit is configured such that solenoids 42a, 41a, 41b, and 42b are connected in parallel to both terminals of a power source B via a power switch S, and each solenoid 42a, 41a , 41b, 42
b and connect in series with each other to operate the manual switch.
SF ₁ , SF ₂ , SF ₃ , and SR are provided. These manual switches SF ₁ , SF ₂ , SF ₃ , and SR may be provided with a main shift lever 57 as shown in FIG. 1, and may be selectively turned on by rotating the lever 57. However, it may also be a push button type. And the sensor switch SF′ ₁ ,
SF' ₂ and SF' ₃ are connected in parallel with the manual switch SF ₁ for 1st forward speed, the manual switch SF ₂ for 2nd forward speed, and the manual switch SF ₃ for 3rd forward speed, respectively, as shown in FIG. Inserted into the electrical control circuit.

As shown in FIG. 2, the gear transmission 17 includes transmission gears 60, 61, 62 fixed on the hollow transmission shaft 15, and hollow transmission gears 60, 61, 62, which receive input from the transmission shaft 13 through engagement of gears 58, 59. Transmission shaft 15
The transmission gear 64 on the drive shaft extension 12a and the transmission shaft 1
a plurality of shift gears 6 spline-fitted to 6;
5, 66, 67, and a meshing clutch 68 interposed between the transmission shafts 13, 16, the shift gears 65-67 can be selectively slidably displaced on the transmission shaft 16. Therefore, the meshing between gears 64 and 65 is 1st speed (very low speed), the meshing between gears 62 and 65 is 2nd speed, and the meshing between gears 61 and 66 is 3rd speed.
4 speed due to meshing between gears 60 and 67, and 5 speed due to direct connection between shafts 13 and 16 by actuation of meshing clutch 68.
It is said that it is possible to obtain the respective speed change ratios. In FIG. 2, reference numeral 69 denotes left and right brakes for the left and right rear wheels 2, which are provided at the ends of the differential output shaft 18a.

Further, the above-mentioned PTO transmission 23 similarly has a second
As shown in the figure, a plurality of transmission gears 70, 71, 72, 73 fixed on the transmission shaft 22 and a PTO
A plurality of shift gears 74, 75, 76 spline-fitted to the shaft 9 and an idler gear 7 on the PTO shaft 9
7, which includes an idler gear 77 meshed with the speed change gear 70 on the transmission shaft 22 and a dog clutch 78 interposed between the shift gear 74 and the PTO shaft. Selective sliding displacement of shift gears 74-76 on gear 9 results in first gear with actuation of dog clutch 78, second gear with meshing between gears 71 and 74, and third gear with meshing between gears 72 and 75.
It is said that a four-speed gear ratio can be obtained by meshing between the gears 73 and 76.

The traveling speed control device shown in FIG. 1-6 is configured as described above, so that when cultivating in the field, the speed change ratio by the gear transmission 17, which is the traveling power sub-transmission device, and the working machine 7 are controlled. PTO for power shifting
The gear ratio of the transmission 23 is set appropriately according to the field conditions, and the gear ratio of the gear 4 described above is set in advance.
3 and 44 to put the working machine load detection means into the operating state, and the main shift lever 57
With this in the neutral position, manually switch SF ₁ ,
If you proceed with work such as plowing with SF ₂ , SF ₃ , and SR in the OFF state, the sensor switch SF' will be automatically switched off depending on the magnitude of the load acting on the work implement 7 for large loads L ₁ - L ₂ . ₁ is turned on and the solenoid 42a is energized to move the solenoid valve 42 to the forward 1st speed position F ₁
When the load is medium, _L2 - _L3 , the sensor switch _SF'2 turns on and the solenoid 41a is turned on.
With the excitation of , the solenoid valve 41 assumes the second forward speed position _F2 ,
At small loads _L3 - _L4 , the solenoid 41b is energized and the solenoid valve 41 assumes the third forward speed position _F3 . Therefore, the greater the load applied to the working machine 7, the lower the running speed of the machine automatically becomes, and a constant working state is obtained. In addition, when manually changing the aircraft's traveling speed during work, when moving the aircraft backwards, or when driving on the road, use gear 4.
4, the gear 44 is disengaged from the gear 43, and the load detection means is switched to the sensor switch.
By keeping SF′ ₁ , SF′ ₂ , and SF′ ₃ in the inactive state in which they maintain the off state, manual switches SF ₁ ,
By selectively manipulating SF ₂ , SF ₃ , and SR, the transmission state of the transmission by the hydraulic clutch type transmission 14 can be controlled.

Next, the second embodiment shown in Figures 7-10 will be explained. In this second embodiment, first, the PTO
The transmission 23' is configured as a hydraulic clutch type transmission as described below. That is, the PTO transmission 23', as shown in FIG.
A first speed change gear 79, a second speed change gear 80, a third speed change gear 81, which are fixedly provided to
1-speed idle gear 82 meshed with 9, 80, 81,
2nd speed idler gear 83, 3rd speed idler gear 84, and PTO
One friction plate is attached to a clutch housing fixed to the shaft 9, and each of the above-mentioned free rotating gears 82-8
A first-speed hydraulic clutch 85, a second-speed hydraulic clutch 86, and a third-speed hydraulic clutch 87 are each configured as a multi-plate type in which the other friction plate is supported by the other friction plate in the clutch axis direction so as to be slidable only. In addition, each idler gear 82-84 is selectively operated by selectively operating each hydraulic clutch 85-87.
It is connected to the PTO shaft 9, so that a gear ratio of 1st speed, 2nd speed, or 3rd speed can be selectively obtained. Note that between the transmission shaft 21 and the transmission shaft 22,
A PTO clutch 88 is provided, as described above.
The points that constitute the PTO transmission 23' and the provision of the PTO clutch 88, and the hydraulic clutch 85-8 of the PTO transmission 23' together with the hydraulic pump 37.
The transmission mechanism is the same as in the previous embodiment, except that a hydraulic pump 89 for supplying oil to the pump 7 is provided.

As shown in FIG. 8, the hydraulic oil supply/discharge control circuit to the plurality of hydraulic clutches 85, 86, 87 in the PTO transmission 23' supplies the hydraulic oil at the hydraulic pressure set by the pressure regulating valve 90 by the hydraulic pump 89. Connected to an oil supply circuit 91 leading toward the hydraulic clutches 85-87 and a tank circuit 92 discharging hydraulic oil from the direction of the hydraulic clutches 85-87 to the oil tank 36,
It is configured to be provided with two electromagnetic valves 93 and 94. Among these, the solenoid valve 93 on the front stage side is
Like the electromagnetic valve 41, it is a 3-position, 5-port valve, and has the function of connecting the oil supply circuit 91 in the direction of the subsequent electromagnetic valve 94 at the neutral position N, and the 2-speed hydraulic clutch 86 and the 3-speed hydraulic clutch 87. In other words, in the 2nd speed position displaced by the excitation of the solenoid 93a, the 2nd speed hydraulic clutch 88 is supplied with oil, and in the 3rd speed position displaced by the energization of the solenoid 93b, the 3rd speed hydraulic clutch 87 is supplied with oil. It is said to be equipped with the function of refueling. The rear solenoid valve 94 is configured as a 2-position, 3-port valve, and supplies oil to the 1st-speed hydraulic clutch 85 when the solenoid 94a is energized from the neutral position N to the 1st-speed position. It is said that In this other embodiment as well, the hydraulic oil supply and discharge control circuit for the hydraulic clutches 32-35 of the hydraulic clutch type transmission 14 is almost the same as in the previous embodiment, but the solenoid valve 42 is different from that in the previous embodiment. Unlike the case of the embodiment, the valve is a five-port valve, and valves having the same structure can be used as the solenoid valves 41, 42, and 93.

Next, the load detection means of the working machine 7 in this embodiment is configured to directly detect the load of the working machine 7, as shown in FIG. That is, this load detection means connects the top link 6a of the coupling device 6 to a bracket 95 that is rotatable around a fulcrum 95a and is biased to rotate in the opposite direction of arrow B by a tension spring 96. The bracket 95, which is pivotally supported and rotatably displaced in the direction of arrow B through the top link 6a against the biasing force of the spring 96 due to an increase in the load L acting on the work implement 7, is connected via a link device 97 in the same manner as described above. The load L is connected to the rotating shaft 55 of the rotary switch device 56 to directly detect the load L.

In this embodiment, as shown in FIG. 10, the solenoids 42a, 94a, 41a, 93a, 41b, 93
b, 42b and manual switch SF ₁ , S for it
, SF ₂ , S, SF ₃ , S, and SR are connected in series, and the power supply S is connected via the power switch S.
Each set of solenoid and manual switch is connected to both terminals of the Furthermore, in this embodiment, the three sensor switches SF' ₁ , SF' ₂ , SF' ₃ built into the rotary switch device 56 (FIG. 9) are as follows:
As shown in Fig. 10, the sensor switch _SF'1 , which is configured with double contacts and detects the load of the working machine in a high range, is a manual switch _SF1 for forward 1st speed and a manual switch for PTO 1st speed. In parallel with S, the sensor switch SF' ₂ that detects the work machine load in the medium range is a manual switch for two forward speeds.
A sensor switch SF' 3 for detecting the work machine load in a low range is connected in parallel with _the manual switch S for SF ₂ and PTO 2nd speed, respectively, and the manual switch SF ₃ for forward 3rd speed and
In parallel with the PTO 3-speed manual switch S,
It is connected and incorporated into the electric control circuit shown in FIG.

Therefore, in the second embodiment shown in Figures 7-10, manual switches SF ₁ , SF ₂ , SF ₃ , SR
and S, S, and S are kept in the OFF state, and when the work is carried out under load detection by the load detection means, the sensor switch _SF'1 is turned on in a certain high range of work equipment load, and the solenoid 4 is turned on.
With the excitation of 2a and 94a, the solenoid valve 42 moves to the forward 1st speed position.
F ₁ and the solenoid valve 94 is set to the first speed position I, the machine body is caused to travel at the first speed forward speed, and the work implement 7 is driven at the rotation speed of the first speed. Similarly, in a medium load range of the work machine, the sensor switch _SF'2 is turned on, and the solenoid valve 41 moves forward by the excitation of the solenoids 41a and 93a.
speed position _F2 , and the solenoid valve 93 changes the second speed position,
In each case, the machine is made to travel at the forward speed of the second speed, and the work implement 7 is driven at the rotation speed of the second speed, and in a certain low range of work machine load, the sensor switch SF' ₃ is turned on. Solenoid valve 4 is activated by energizing solenoids 41b and 93b.
1 assumes the 3rd forward speed position F ₃ and the solenoid valve 93 takes the 3rd speed position, so that the machine body is driven at the 3rd forward speed, and the work implement 7 is driven at the rotational speed of the 3rd speed. becomes. In this way, as the load applied to the work implement 7 becomes larger, not only the traveling speed of the machine is automatically reduced, but also the drive rotational speed of the work implement 7 is reduced. A more constant working state is achieved. Also in this second embodiment, the load detecting means detects the sensor by, for example, locking the bracket 95 in a specific rotational posture, locking one link in the link device 97, or releasing the link connection. switch
SF′ ₁ , SF′ ₂ , SF′ ₃ are configured to be in a non-operating state in which they maintain an off state, and in the non-operating state of this load detection means, manual switches SF ₁ ,
The aircraft running speed can be controlled manually by operating SF ₂ , SF ₃ , and SR, and manual switches S and S
, S allows manual control of the drive rotation speed of the working machine 7. Further, with the PTO clutch 88 disengaged, only the aircraft is allowed to travel, and its traveling speed is manually controlled.

Next, FIG. 11 shows a modification of the second embodiment described above, in which the configuration of the electric control circuit is simplified. That is, in this modification, the solenoids 42a, 41a, 41b that control the forward speed of the machine body, and the solenoids 94a, 93a, 93a,
93b, respectively, are connected in series as shown in the figure, and for each set of two solenoids connected in series, the corresponding manual switch SF ₁ , SF ₂ , or
Sensor switches SF _{' 1 ,} SF' ₂ , or SF' ₃ corresponding to SF 3 are connected in parallel and then in series. Therefore, the sensor switch SF′ ₁ ,
By selectively operating SF' ₂ and SF' ₃ , as in the case of the second embodiment, the machine running speed and the work machine driving rotation speed are automatically changed and controlled according to the work machine load, and the sensor switch When SF′ ₁ , SF′ ₂ , and SF′ ₃ remain in the off state and the load detection means is inactive, manual switches SF ₁ , SF ₂ , and SF ₃ can be used to control the machine's forward traveling speed and work implement drive rotation speed. It is possible to manually change and control the PTO at the same time.
If the clutch 88 is disengaged, manual changes in the traveling speed of the aircraft, including reversing the aircraft, can be performed by operating manual switches SF ₁ , SF ₂ , SF ₃ , and SR.

As is clear from the above description, the agricultural tractor of the present invention is an agricultural tractor equipped with a hydraulic clutch type transmission 14 for changing traveling power, and the plurality of hydraulic clutches 32 in the hydraulic clutch type transmission 14, The control valves that control the supply and discharge of hydraulic oil to 33, 34, and 35 are set to respective operating positions _F1 , _F2 , and _F2 by selectively turning on multiple manual switches _SF1 , SF2, _SF3 , and SR. The solenoid valves 41 and 42 are configured to be displaced to F ₃ and R, and are load detection means for detecting the load of the working machine, and are equipped with a plurality of sensor switches that detect the load in a certain range in stages by turning on each one. SF′ ₁ ,
A load detection means comprising SF' ₂ and SF' ₃ is provided, and in the electric control circuit for controlling the position switching of the electromagnetic valves 41 and 42, manual switches SF _{1 and 3} for the forward gear of the manual switches are provided. SF ₂ , SF ₃ 1
Individual and above sensor switches SF′ ₁ , SF′ ₂ , SF′ ₃
The manual switch on the lower gear side is connected in parallel with the sensor switch on the higher load detection side of the work machine, and the hydraulic clutch type transmission By skillfully utilizing the existence of the device and installing the solenoid valve and two types of switches as described above, it is possible to automatically control the machine running speed according to the work machine load and proceed with work under stable and constant conditions. , in addition to manual aircraft travel speed control, it is possible to perform
In contrast to No. 52-78420, the structure has been simplified as follows.

In other words, this invention is a manual switch for one
SF ₁ , SF ₂ , SF ₃ and sensor switch SF′ ₁ ,
SF′ ₂ , SF′ ₃ are connected in parallel to each other, and solenoid valves 41 , 42 which are control valves for changing the gear stage of the hydraulic clutch type transmission 14 are connected to the manual switches SF ₁ , SF ₂ , The solenoid valve 41 can be displaced to each operating position F ₁ , F ₂ , F ₃ in the forward direction of the vehicle both by SF 3 and by each sensor switch SF _{′ 1} , SF ₂ , SF′ ₃ . , 42 is used both as a control valve for controlling the vehicle speed by human operation and as a control valve for automatically controlling the vehicle speed according to the load of the work equipment, eliminating the need to separately install a control valve for automatically controlling the vehicle speed. Therefore, the solenoid valves 41 and 42 can have the same structure as the solenoid valves used when vehicle speed is controlled only by manual operation.

According to an embodiment of the present invention, the control valve is connected to the plurality of hydraulic clutches 3.
When configuring a plurality of solenoid valves 41 and 42 that are connected in series in the direction of oil supply to 2, 33, 34, and 35, as shown in the embodiment, the solenoid valves are arranged in three positions or less. In a solenoid valve with up to 3 positions, the solenoid can be constructed by winding a coil around a core integrated with the spool, which simplifies the solenoid valve structure. These strengths have been further enhanced.

Further, in accordance with another embodiment of the invention, a second hydraulic clutch type transmission 2 for power transmission of the work machine is provided, as in the second embodiment of Figures 7-10.
3', and multiple hydraulic clutches 85, 86, 8 in this second hydraulic clutch type transmission 23'.
A control valve for controlling the supply and discharge of hydraulic oil to and from 7 is constituted by electromagnetic valves 93 and 94 that can be displaced to respective operating positions by selectively turning on a plurality of manual switches S, S, S, The above manual switches S, S for this solenoid valve 93, 94
, S and one of the sensor switches SF' ₁ , SF' ₂ , SF' ₃ of the load detection means mentioned above,
When a manual switch on the low-speed gear side is connected in parallel with a sensor switch on the high-load detection side of the work equipment, the work equipment drive speed can be automatically controlled at the same time as the machine running speed is automatically controlled according to the work equipment load. As automatic control becomes possible, the accuracy of the automatic control that stabilizes the working conditions of the work equipment will be greatly improved, and the machine running speed and work equipment drive rotation speed can be controlled independently and manually. Changes can be controlled by operation, making it convenient for operation.

Furthermore, according to another embodiment of the invention, as in the variant of FIG. The control valves for controlling the supply and discharge of hydraulic oil to the plurality of hydraulic clutches 85, 86, 87 in the device 23' are constituted by electromagnetic valves 93, 94, and the electromagnetic valves 93, 94 are moved to each operating position by selective excitation. By selectively energizing one of the plurality of solenoids 94a, 93a, 93b and the solenoid valves 41, 42 for the hydraulic clutch type transmission 14 for changing the driving power, each forward speed change operation position is set. When connecting one of the plural solenoids 42a, 41a, 41b to be displaced to F ₁ , F ₂ , F ₃ in series so that the traveling speed and the rotation speed of the work machine correspond to each other, It has become possible to automatically control the machine running speed according to the work machine load, and at the same time automatically control the work machine drive rotation speed, making the precision of automatic control that stabilizes the work machine working condition much higher. In addition, as shown in the embodiment, the manual switch for both hydraulic clutch type transmission devices 14, 23' can be made common, and the structure of the electric control circuit can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a side view of the first embodiment of the present invention, FIG. 2 is a mechanical diagram of the transmission mechanism in the same embodiment, and FIG.
The figure is a circuit diagram of the hydraulic circuit in the same embodiment, FIG. 4 is a longitudinal side view showing the load detection means in the same embodiment, and FIG. 5 is a perspective view of one member of the load detection means.
Fig. 6 is a circuit diagram of an electric control circuit in the same embodiment, Fig. 7 is a mechanical diagram showing a transmission mechanism in a second embodiment of the invention, and Fig. 8 is a circuit diagram of a hydraulic circuit in the second embodiment. FIG. 9 is a schematic side view showing the load detection means in the second embodiment, and FIG.
FIG. 0 is a circuit diagram of an electric control circuit in the second embodiment, and FIG. 11 is a circuit diagram of an electric control circuit in a modified example. DESCRIPTION OF SYMBOLS 1...Engine, 2...Rear wheel, 6...Connection device, 6a
…Top link, 7…Work equipment, 9…PTO axis, 1
2... Drive shaft, 13... Transmission shaft, 14... Hydraulic clutch type transmission, 15... Hollow transmission shaft, 16... Transmission shaft,
17...Gear transmission, 21...Intermediate shaft, 22...Transmission shaft, 23, 23'...PTO transmission, 32... _F1 hydraulic clutch, 33... _F2 hydraulic clutch, 34... _F3 hydraulic clutch, 35...R hydraulic pressure Clutch, 39... Oil supply circuit, 40... Tank circuit, 41, 42... Solenoid valve,
41a, 41b, 42a, 42b...Solenoid,
43, 44...Gear, 45...Hollow rotating shaft, 45a...
Flange section, 46...Advancing/retracting rod, 46a...Large diameter collar section, 48...
Pin, 49... Curved arm, 50... Weight, 52... Compression spring, 53... Rack tooth, 54... Pinion,
55... Rotating shaft, 56... Rotary switch device,
85... 1st speed hydraulic clutch, 86... 2nd speed hydraulic clutch, 87... 3rd speed hydraulic clutch, 88... PTO clutch, 91... Oil supply circuit, 92... Tank circuit, 9
3, 94...Solenoid valve, 93a, 93b, 94a,...
Solenoid, 95...bracket, 95a...fulcrum,
96...Tension spring, 97...Link device, B...Power supply, S...Power switch, _SF1 , _SF2 , _SF3 , SR...
Manual switch, _SF'1 , _SF'2 , _SF'3 ...Sensor switch, S, S, S...Manual switch.

Claims (1)

[Scope of Claims] 1. An agricultural tractor equipped with a hydraulic clutch type transmission for changing traveling power, comprising: a control valve for controlling supply and discharge of hydraulic oil to a plurality of hydraulic clutches in the hydraulic clutch type transmission; It is configured as a solenoid valve that can be moved to each operating position by selectively turning on multiple manual switches, and is also a load detection means for detecting the load on the work machine, which turns on each load in a certain range in stages. A load detecting means having a plurality of sensor switches for detecting by operation is provided, and in the electric control circuit for controlling the position switching of the solenoid valve, one of the manual switches for the forward gear stage is provided. and one of the above-mentioned sensor switches are connected in parallel to each other in combination with a manual switch on a lower speed gear side and a sensor switch on a higher load detection side of the working machine. 2. The agricultural tractor according to claim 1, wherein the control valve is configured as a plurality of electromagnetic valves connected in series with each other in the direction of oil supply to the plurality of hydraulic clutches. . 3. A second hydraulic clutch type transmission for changing the working machine power is provided, and a control valve for controlling the supply and discharge of hydraulic oil to the plurality of hydraulic clutches in the second hydraulic clutch type transmission is connected to a plurality of manual switches. The electromagnetic valve is configured to be displaced to each operating position by an alternative ON operation, and one of the manual switches for this electromagnetic valve and one of the sensor switches of the load detection means described above are connected to a low speed shift. 3. The agricultural tractor according to claim 1, wherein the manual switch on the step side is connected in parallel with the sensor switch on the work machine high load detection side. 4. A second hydraulic clutch type transmission device for power shifting of the working machine is provided, and a control valve for controlling the supply and discharge of hydraulic oil to the plurality of hydraulic clutches in the second hydraulic clutch type transmission device is configured as a solenoid valve,
One of the plurality of solenoids displaces the solenoid valve to each operating position by selective excitation, and the solenoid valve for the hydraulic clutch type transmission for changing the traveling power is selectively energized. A patent claim characterized in that one of a plurality of solenoids for displacing the forward speed change operating position is connected in series so that the travel displacement and the rotation speed of the work machine correspond to each other. The agricultural tractor according to item 1 or 2.