JPS591858Y2 - Speed change control device for agricultural tractors, etc. - Google Patents

Description

[Detailed description of the invention] This invention connects a variable displacement hydraulic pump and a constant displacement hydraulic motor by a pair of oil supply and drainage circuits that together with the hydraulic pump and hydraulic motor constitute a closed circuit. An agricultural tractor or the like is provided with a hydraulic transmission device configured to change and control the drive rotation speed of the hydraulic motor by the hydraulic pump by changing the swash plate angle of the hydraulic pump, thereby changing and controlling the gear ratio. , relates to a speed change control device for controlling the speed change state by the hydraulic transmission device.

That is, when changing and controlling the gear ratio of the hydraulic transmission device by changing and adjusting the swash plate angle of a variable displacement hydraulic pump in the hydraulic transmission device, if you try to obtain a neutral state by setting the swash plate angle to 0 degrees using the operating means. However, this invention aims to provide a new speed change control device for agricultural tractors, etc., which can reliably achieve a neutral state of the hydraulic transmission device with a simple structure.

Regarding the illustrated embodiment, the configuration of the speed change control device for an agricultural tractor or the like according to this invention will be explained. In FIG. A spacer plate 3 is sandwiched between the clutch housing 1 and the transmission case 2, and a variable displacement hydraulic pump 4 and a constant displacement hydraulic motor 5 are installed on the back surface of the gap plate 3. are arranged vertically in the transmission case 2 to form a hydraulic transmission device.

A spacer plate 3 is provided between the hydraulic pump 4 and the hydraulic motor 5.
It is connected by two sets of oil supply and drainage circuits 6゜7 drilled in the oil supply and drainage circuits 6 and 7, and is connected to the hydraulic pump 4 through one of the oil supply and drainage circuits 6 and 7. By supplying pressure oil to the hydraulic motor 5 and returning hydraulic oil from the hydraulic motor 5 to the hydraulic pump 4 via the other oil supply/discharge circuit 7 or 6, the pump 4 can rotate the motor 5 in the forward or reverse direction. The drive is performed.

Controlling changes in gear ratio, including switching between forward and reverse,
This is done by controlling the angle of the swash plate 4a of the hydraulic pump 4 by rotating the gear shift lever 8. It is provided.

In the operating mechanism housing 9, an operating cylinder (not shown) and a servo control valve are connected via a feedback link, and a rotating arm 10, which is rotatably displaced by the operating cylinder, is operated. The rotating arm 10 is fixed at its lower end to a swash plate shaft 4b that extends from the inside of the mechanism housing 9 into the mission case 2 and serves as a pivot point for the rotating arm 10, and is rotated by operating the gear shift lever 8. The rotational displacement of the arm 1Q is obtained, thereby rotationally displacing the swash plate shaft 4b, thereby changing the angle of the pump swash plate 4a.

The above explanation is as usual except for the provision of the intervening board 3 and the layout of various parts. Oil passages 11 and 12 respectively connected to the oil supply and discharge circuits 6 and 7 formed in 3.
The ends of the oil passages 11 and 12 are opened at the lower end surface of the intervening plate 3.

The valve case 13a is fixed to the lower end surface of the spacer plate 3, and the following short circuit valve 13 is mounted thereon.

That is, this short-circuit valve 13 has the above-mentioned valve cake 13a,
A port 14 communicating with the oil passage 11 and a port 15 communicating with the oil passage 12 are formed, and a rotor 13b, which is a valve body, is rotatably inserted into the valve case 13a, and a rotor 13b is connected to the rotor 13b in the axial direction. The oil passage 16 along the rotor
A radial oil passage 17 that constantly communicates between the port 14 and the oil passage 16 via an annular groove 17a on the circumferential surface of 13b, and a radial small-diameter oil passage 1B that selectively communicates between the port 15 and the oil passage 16. , respectively, and are composed of the following.

The small diameter oil passage 18 is connected to the rotor 13 as shown in FIG.
The port 15 is opened within the range of a constant rotational displacement angle θ of b, and the port 15 and the oil passage 16 are communicated only within the range of the angle θ.

The rotor 13b of the short circuit valve 13 is connected to the swash plate shaft 4b.
The rotor 13 b
A rotating arm 20 fixed to the base end is connected via a connecting link 21, so that the rotor 13b can be rotated by changing the angle of the pump swash plate 4a using the gear shift lever 8 as described above. As if forced to
It's a plan.

The range of the angle θ mentioned above is approximately centered around
It is set to correspond to the zero angle of the pump swash plate 4a.

In FIG. 1, reference numeral 22 denotes a charge pump installed in the clutch housing 1 and attached to the front surface of the spacer plate, and is used to supply hydraulic oil to the closed circuits 6 and 7.

Since the illustrated speed change control device according to this invention is configured as described above, the small diameter oil passage 18 of the rotor 13b opens to the port 15 as described above.
Within the range of the rotation angle θ, the short-circuit valve 1 is connected between the oil passages 11 and 12.
3, i.e. the port 14 of the short-circuit valve, the annular groove 17
a, the oil passage 17, the oil passage 16, the small-diameter oil passage 1B, and the ports 1 to 15 are connected and connected, thereby short-circuiting both oil supply and discharge circuits 6 and 7, so that Moyo 5 is activated. is stopped, and a neutral state of the hydraulic transmission system is obtained.

That is, the short-circuit valve 13 is inserted into a short-circuit oil passage 11.12 that short-circuits both the oil supply and discharge circuits 6 and 7, and the short-circuit valve 13 is inserted into a short-circuit oil passage 11.
3. Outside the range of rotational displacement angle θ of b, the short-circuit oil path 11.1
2 is blocked, and within the range of the displacement angle θ, the hydraulic transmission device is placed in a neutral state by releasing the block, and the range of the above angle θ becomes the neutral region of the hydraulic transmission device.

As described above, the speed change control device for agricultural vehicles, tractors, etc. of this invention forms a closed circuit between the variable displacement hydraulic pump 4 and the fixed displacement hydraulic motor 5 together with the hydraulic pump 4 and the hydraulic motor 5. By changing the angle of the swash plate 4a of the hydraulic pump 4, the driving rotation speed of the hydraulic motor 5 by the hydraulic pump 4 is changed and controlled, thereby changing the gear ratio. In agricultural tractors, etc., equipped with a hydraulic transmission device configured to control
A short-circuit oil path 11.12 is provided to short-circuit the two oil supply/discharge circuits 6.7 that connect the hydraulic pump 4 and the hydraulic motor 5 in the hydraulic transmission device described above, and this short-circuit oil path 11
．． 12 for selectively blocking and unblocking the oil passage 11.12, the valve body 13 thereof;
A short-circuit valve 13 is provided to release the block within a certain displacement range of b, and the valve body 13b of this short-circuit valve 13 is operatively connected to the swash plate angle changing operation means 8 of the hydraulic pump 4. The unblocking range is set to the neutral range of the hydraulic transmission device, and it has a simple structure that does not use a relief valve, etc., and a short circuit between both oil supply and discharge circuits ensures that the hydraulic transmission device is in the neutral state. It's a good deal.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the main parts of an agricultural tractor equipped with an embodiment of this invention, Fig. 2 is a vertical side view and hydraulic circuit diagram of the main parts of the same embodiment, and Fig. 3 is the same as Fig. 2. FIG. 3 is a cross-sectional view taken along line III. DESCRIPTION OF SYMBOLS 1...Clutch housing, 2...Mission case, 3...Interval plate, 4...Hydraulic pump, 4a...Pump swash plate, 4b...Swash plate shaft, 5...Hydraulic motor ,6
, 7... Oil supply/drainage circuit, 8... Gear shift lever, 10...
・Rotating arm, 11° 12... Oil path, 13... Short circuit valve, 13a... Valve case, 13 b... Rotor,
14.15...Port, 16...Oil passage, 17...
- Oil passage, 17 a... Annular groove, 1B... Small diameter oil passage, 19... Rotating arm, 20... Rotating arm, 2
1... Connection link.

Claims (1)

[Scope of utility model registration request] between a variable displacement hydraulic pump and a fixed displacement hydraulic motor.
1 constituting a closed circuit together with the hydraulic pump and hydraulic motor;
The hydraulic transmission is connected by a pair of oil supply/drainage circuits, and is configured to change and control the drive rotation speed of the hydraulic motor by the hydraulic pump by changing the swash plate angle of the hydraulic pump, thereby changing and controlling the gear ratio. The device is installed in an agricultural tractor, etc., by providing a short-circuit oil path that short-circuits both the oil supply and discharge circuits that connect the hydraulic pump and the hydraulic motor in the hydraulic transmission device, and by inserting the device into the short-circuit oil path. A short-circuit valve that selectively blocks and unblocks the oil passage is provided, and the short-circuit valve performs the blocking within a certain displacement range of the valve body, and the valve body of the short-circuit valve is connected to the swash plate of the hydraulic pump. What is claimed is: 1. A speed change control device characterized in that it is operatively connected to an angle changing operation means and sets the unblocking range of the short circuit valve to a neutral region of a hydraulic transmission device.