JPS6125403A - Hydraulic apparatus for controlling three-point link apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a three-point linkage device for a tractor. Specifically, one of the top link and the lift rod is made into a hydraulic cylinder to perform horizontal control and top link control. The present invention relates to a hydraulic system for controlling a three-point linkage device.

(B) Conventional technology Conventionally, in a three-point linkage device, one side of the lift rod is configured to be telescopic and retractable as a hydraulic cylinder, and it is possible to horizontally control a rotary or other work equipment to always maintain it horizontally regardless of the tilt of the machine. The top link is configured to be extendable and retractable as a hydraulic cylinder, and the top link is shortened to increase the lifting height of the work equipment or shorten the plowing time when turning the tractor or plowing in plowing work. There are some that can control top links. However, the conventional three-point link device simply controls expansion and contraction of the hydraulic cylinder using an ordinary switching valve, and its accuracy is not high.

In addition, in the horizontal control of extending and retracting the lift rod, a solenoid valve for pulse width modulation (hereinafter referred to as PWM) control is used. There are some that can control position with precision.

Therefore, when trying to use the 3-position solenoid valve for PWM III, which can be controlled with high precision, for horizontal control and top link control, as shown in FIG. It also communicates via a flow priority valve 5 to an ordinary two-position switching valve 6, and in the switching valve 6, the hydraulic pressure constituting the lift rod via three-position switches 7 and 9 for PWM control, respectively. It is configured to communicate with the cylinder 10 and the hydraulic cylinder 11 that constitutes the top link. That is, when performing horizontal control, the switching valve 6 is switched to the lift rod side, and the switching valve 7 for PWM control is switched to the lift rod side.
The lift rod cylinder 10 is extended and retracted with high precision by the operation of , and when performing top link control, the switching valve 6 is switched to the top link side, and the top link cylinder 1 is moved with high precision by operating the other PWM111II switching valve 9.
Expand/contract 1.

(8) Problems to be solved by the invention For this reason, the hydraulic system that is an extension of the prior art is
It is necessary to use two 3-position solenoid valves for WM control, but the valves for PWM control are larger than ordinary switching valves and are extremely expensive. Using two valves makes space design complicated and increases costs. Furthermore, the hydraulic circuit becomes complicated, especially P.
WM111! There is a possibility that the leakage from the 3-position solenoid valve for III will be large and the pressure loss will increase.

(d) Means for solving the problem The present invention aims to solve the above-mentioned problems, and
As shown in the figure, PWM is first applied to oil path R from pump 3.
A normally open type 2-position switching valve (solenoid valve) 12 for control is arranged in a branched manner, and two ordinary 3-position switching valves 13 and 15 are arranged in parallel in the oil path R. Lift rod cylinder 10 for each switching valve
It is characterized by communicating with the top link cylinder 11.

(→ Operation Based on the above configuration, when horizontal control is performed, the switching valve 15 for the top link m mill is set to the neutral closed position and the PWM
With the IllIII valve 12 closed, the lift rod control switching valve 13 is operated to press oil into or out of the hydraulic cylinder 10 to control the extension of the lift rod. Then, when the work equipment is close to horizontal, P
The solenoid valve 12 for WMllllI is inching controlled by pulse width modulation that intermittently repeats the closing position and the drain position, thereby gradually restricting the amount of oil press-fitted into the hydraulic cylinder 16. The amount of expansion/contraction is gradually reduced, and then it stops at the set position. Similarly, when performing top link control, operate the top link control switching valve 15 with the lift rod control switching valve 13 and the PWM flll II control valve in the wR closed position to control the expansion and contraction of the top link, Furthermore, inching control is performed by a solenoid valve 12 for PWMljllj at the end of the extension/contraction of the top link.

(→ Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 to 4.

As shown in FIG. 2, the tractor 20 has a body 22 supported by wheels 21, and the body 22 has an engine 23 mounted on its front part and an oil tank at its rear part. A Mitsushiron case 24, which also serves as a power supply unit 1, is arranged, and various hydraulic devices are electrically connected. That is, a hydraulic filter 2, a gear pump 3, a flow divider 4, a flow priority valve 5, and a control valve 2.
5, and electromagnetic switching valve 13 for the lift rod cylinder
, electromagnetic switching valve 15 and PW for top link cylinder
A solenoid valve 12 for MIII is provided. Furthermore, left and right lift arms 29 are rotatably disposed in the fuselage 22vk portion by hydraulic cylinders 27 (FIG. 3), and left and right lower links 30 are pivotally supported. The lift arm 29 and the lower link 30 are connected by a lift rod 31°31, and a top link 32 is pivotally supported at the center of the rear part, and these lower links 30 and top links 32 form a three-point link. It constitutes a device 33. And lift rod 31,
One side of the hydraulic cylinder 10 is extendable and retractable, and the top link 32 is also connected to the hydraulic cylinder 11.
It is constructed to be expandable and contractible.

As shown in FIG. 3, the position sensor 35 and the depth sensor 36 are connected to a master controller 37a in the control box 37, and further output from the controller 37a to the control valve 25 of the lift arm 29J11 pressure cylinder 27. ing. In addition, the right lift rod length sensor 39 or the left lift rod length sensor 40
and the MN angle sensor 41 are connected to the level controller 37b in the box 37, and the controller 37b further connects the lift rod 3-position electromagnetic switching valve 13 and the PWMfl
Normal open type 2nd place m for III use! It is output to the solenoid valve 12. Further, the top link length sensor 42 is connected to the top link controller 37 in the box 37.
c, and output is further output from the controller 37c to the 3-position electromagnetic switching valve 15 for the top link and the solenoid valve 12 for PWM control.

Since this embodiment has the above configuration, based on the signal from the body sensor 35 or the depth sensor 36,
Master controller 37 of control box 37
Processing such as arithmetic operations is performed at a, and the control valve 25 is controlled by a rising or falling signal from the controller, and the hydraulic cylinder 27 is controlled to expand and contract to lift the lift arm 29.
rotates, and the position of the work equipment is controlled to move up and down using position control or depth control. In addition, the signal from the top link length sensor 42 is processed by the top link controller 37c, which is switched by the contraction signal or extension signal of the controller 37c to control the expansion and contraction of the hydraulic cylinder 11 provided on the top link 32, and at the same time. The cylinder 1
The change in the length of the top link 32 due to the expansion and contraction of the sensor 4
2 to the controller 37b. At this time, the lift rod switching valve 13 is in the neutral closed position, and the PWM control solenoid valve 12 is in the closed position, thus FIG. 4(a).

As shown in (b), based on the elongation signal, the top link 3
The period from 0 to y time when the top link 32 extends to the a''-c position is controlled to be the shortest time.When the top link 32 reaches the position C, which is slightly short of the preset extended position, , an inching signal is issued from the controller 37C, and the solenoid valve 12 for PWM control repeats opening and closing so that the pulse width becomes gradually shorter, and in the open position, the pressure oil from the pump 3 is drained into the tank 1. The switching valve 15 is therefore not sent to the hydraulic cylinder 11, but is sent to the cylinder 11 only in the closed position of the valve 12, and the top link 32 slowly extends with its extension speed gradually decreasing (y = x). link 32
When the controller 37c reaches the predetermined extended position, the extension signal and inching signal from the controller 37c are cut off, and the switching valve 15
becomes the neutral closed position, the PWM III valve 12 is returned to the open position, and the top link 32 is accurately positioned and stopped. In addition, signals from the left and right lift rod length sensors 39° 40 and the tilt angle sensor 41 are processed by the level controller 37c, and the controller 3
The switching valve 13 is operated by a rising signal or a falling signal from 7b to control the expansion and contraction of the hydraulic cylinder 10 provided on one of the lift rods 31, and at the same time, the change in the length of the lift rod 31 due to the expansion and contraction of the hydraulic cylinder 10 is controlled. An inching signal is sent to the controller 37b by the sensors 39 and 40, and similarly to the above-mentioned top link control, an inching signal is issued from the troller 37b at the extension/retraction end portion of the cylinder 10, and the PWM control solenoid valve 12 performs pulse width modulation. The working machine is controlled to be accurately horizontal by repeating the opening and closing operations and gradually decreasing the amount of expansion and contraction of the hydraulic cylinder 10.

(g) As described in detail, according to the present invention, the lift rod 31
The switching valve 13 for operating the hydraulic cylinder 10 of the top link 32 and the switching valve 15 for operating the hydraulic cylinder 11 of the top link 32,
Using an ordinary 3-position switching valve not for PWM control,
The valve for M control wholesale is a normally open type 2-position switching valve 1
Since only one unit 2 is required, the storage space can be reduced, and it can be easily installed in a crowded place at the rear of the tractor 1. It is also significantly advantageous in terms of cost, and the hydraulic circuit is simplified. , even more leaky pw
M111! Since the I switching valve 12 is normally drained, leakage from the valve can be significantly reduced and pressure loss can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing a hydraulic system for controlling a three-point linkage device according to the present invention, FIG. 2 is an overall side view showing a tractor to which the present invention can be applied, and FIG. 3 is a diagram showing an embodiment of the present invention. A control block diagram shown in FIG. 4(a). (b) is a diagram showing its operation, and FIG. 5 is a hydraulic circuit diagram that is an extension of the conventional device.

Claims (1)

[Claims] (1) In a three-point linkage device 33 in which at least one of the left and right lift rods 31 is composed of a hydraulic cylinder 10 and the top link 32 is composed of a hydraulic cylinder 11, a normally open type two-position switching valve 12 for pulse width modulation control is used.
is branched into the oil path R from the pump 3, and furthermore, two ordinary three-position switching valves 13 are installed in parallel in the oil path from the pump.
15, and a hydraulic cylinder 10 of a lift rod and a hydraulic cylinder 11 of a top link are connected to these ordinary switching valves, respectively, for controlling a three-point linkage device.