JPH01247002A - Hydraulic lifter for agricultural working machine - Google Patents

Abstract

PURPOSE:To prevent maloperation of a hydraulic lifter at low temperatures, by providing a returning mechanism for returning only a hydraulic oil having high viscous resistance to a tank in an oil passage at a position before a pilot valve for lifting and lowering. CONSTITUTION:An oil in a mission case 12 serving also as a hydraulic tank is passed through a hydraulic pump 2 and respectively fed through a flow dividing valve 4 to a hydraulic cylinder 7 for lifting arms and a hydraulic cylinder 8 for lifting rod. At this time, viscous resistance of the oil is sensed by a negative pressure sensor (or temperature) sensor 36. If the viscous resistance is high, a changeover valve 37 is changed over to a port (A) to return the oil to the tank 12. Thereby, since the viscous resistance is high, maloperation due to no changeover of a pilot valve in the hydraulic circuit is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic lift device for a mobile agricultural machine, and more specifically, a hydraulic lift device for a mobile agricultural machine that does not malfunction even at low temperatures when the viscous resistance of hydraulic oil is large. It is related to.

[Traditional technique]

In the conventional hydraulic circuit diagram shown in FIG. 8, hydraulic oil flows in the order of filter 1 - pump 2 - relief valve 3 - diversion valve 4 - control device 5 - descent speed adjustment valve 6 - hydraulic cylinder 7 for lifting and lowering the work equipment. , the lift device will rise. The control mechanism 5 is provided with an ascending pilot valve IO connected to the ascending solenoid valve 14 and a descending pilot valve 15 connected to the descending solenoid valve 16. The solenoid valve 16 is configured to operate in response to a command signal from a microcomputer 35, as shown in FIG.

[Problem that the invention seeks to solve]

By the way, in the above-mentioned conventional hydraulic circuit, there is a problem that the lift device 30 rises even though the t command signal from the microcomputer 35 is in the neutral state or in the descending state at low temperatures when the viscous resistance of the hydraulic oil is large. was there.

In other words, in the neutral state, the lift solenoid valve 14 is switched to the neutral position, so it is normal for the hydraulic oil that has passed through the valve head, which is opened when the pilot valve 10 is pushed down, to escape to the tank 12 through the drain circuit 11. However, if the viscosity of the hydraulic oil is high, even if you try to push down valve IO, valve 1
The disadvantage is that the oil remaining below 0 cannot be removed and the valve IO cannot be pushed down, so the hydraulic oil pushes up the check valve 13 from the oil path A and flows toward the hydraulic cylinder 7, causing the lift device 30 to rise. was there.

In the descending state, the descending solenoid valve 16 is switched to the descending position, so normally the hydraulic oil that has passed through the valve head which is pushed up and opened by the pilot valve 15 escapes to the tank 12 through the drain circuit 17. However, if the viscosity of the hydraulic oil is high, even if you try to push up the valve 15, the valve 1
Since the valve 15 remaining above the valve 5 is not removed and the valve 15 is not pushed up, the hydraulic oil that pushes up the check valve 13 under the influence of the lifting solenoid valve 14 in the neutral position flows into the hydraulic cylinder 7.
There was a drawback that the liquid flowed to the side and the lift device 30 rose.

This drawback does not occur if a heavy work machine is attached to the lift device and the load on the lift device is greater than the viscous resistance of the hydraulic oil, but it may occur if the load on the lift device is small. There was a problem.

Therefore, the present invention has been devised in view of the above-mentioned conventional situation and to eliminate the drawbacks, and is a hydraulic lift device for mobile agricultural machinery that prevents the hydraulic lift device from malfunctioning at low temperatures when the viscous resistance of hydraulic oil is large. The purpose of this project is to provide the following information.

[Means to solve the problem]

The present invention achieves the above object by replacing a rising pilot valve and a descending pilot valve arranged in an oil path between a hydraulic cylinder and a pump with a rising solenoid valve and a descending solenoid valve controlled by a microcomputer. A return mechanism is disposed in the oil path upstream of both the pilot valves and allows only the hydraulic oil with high viscous resistance to flow back into the tank.

[Created for]

Therefore, the ascending pilot valve IO and descending pilot valve 15, which are arranged in the oil passage between the hydraulic cylinder 7 and the pump 2, are controlled by the ascending solenoid valve 14 and the descending solenoid valve 16, which are controlled by the microcomputer 35. Even in the case of a lift device for agricultural machinery that controls both pilot valves, a return mechanism 37 that allows only the hydraulic oil with high viscous resistance to flow back to the tank 12 is provided in the oil path upstream of both pilot valves. Since the hydraulic oil with high viscous resistance is not sent to both pilot valves, the pilot valve 10 or 15 as the control mechanism 5 may malfunction at low temperatures where the viscous resistance of conventional hydraulic oil is high, resulting in a neutral or downward command. However, the problem that the lift device 30 rises despite this can be solved.

〔Example〕

Hereinafter, drawings showing the present invention as an embodiment will be described while avoiding duplication with FIG. 8 described above.

As shown in FIG. 5, reference numeral 20 is an agricultural tractor having an engine 21 disposed at the front, a position lever 24 with a potentiometer setting device 23 attached to the side of the driver's seat 22, and a rotary tiller at the rear. A working machine (not shown) such as a section is connected to be able to rise and fall by an upper link 25 and a pair of left and right lower links 26, and a lift arm 29 of a lift mechanism 30 is connected to the lower link 26 by a pair of left and right lift rods 27. A lift sensor 33 for detecting the angle of the lift arm 29 is attached to the lift shaft 32 which rotates together with the lift arm 29 and the passive arm 31.

As shown in FIG. 6, when the passive arm 31 comes into contact with the rear wall of the hydraulic case 34, the increased pressure in the oil passage is returned to the tank 12 by the relief valve 3. The lift shaft 32 is supported near the rear of the hydraulic case 34, and its passive arm 31 is connected to a piston rod 7a in a hydraulic cylinder 7 that expands and contracts when the ascending solenoid valve 14 and the descending solenoid valve 16 are turned on and off. ing. Further, the set value of the setting device 23 and the detected value of the lift sensor 33 are input to the microcomputer 35 as shown in FIG. ON at 16,
Command the OFF signal.

Therefore, when the position lever 24 is operated fully upward, the set value is greater than the detected value of the lift sensor 33, so the lifting solenoid valve 14 is turned ON, and the stop circuit 11 leading to the pilot valve 10 is closed, and the operation is activated. Oil pushes up the check valve 13 from the passage X and is supplied to the hydraulic cylinder 7, thereby extending the piston rod 7a and lifting the lift arm 29.

Also, when the position lever 24 is operated downward, the set value is larger than the detected value of the foot sensor 33, so
The descending solenoid valve 16 is turned ON, the drain circuit 17 leading to the pilot valve 16 is opened, and the hydraulic oil flowing upward by the check valve 13 and the hydraulic oil in the hydraulic piston 7 are returned to the tank 12 from the drain circuit 17. As a result, the piston rod 7a is pushed back and the lift arm 29 is lowered.

As shown in FIG. 1, a negative pressure sensor 36 is disposed in the oil passage between the filter 1 and the pump 2, and this negative pressure sensor 36 detects that the negative pressure flowing through the oil passage is, for example, -0.3 kg/cod or more. In this case, the electromagnetic switching valve 37 serving as a return mechanism is switched to the A port, so that the hydraulic oil from the pump 2 is returned to the transmission case 12 which also serves as a tank before reaching the diversion valve 4. Due to this reflux, at low temperatures when the viscous resistance of the hydraulic oil is large, the circuit leading to the pump 2 becomes negative pressure, so that the hydraulic oil reaches the hydraulic cylinder 7 via the pilot valve IO, and the lift device 30 rises. You can eliminate the malfunction caused by

The hydraulic oil whose viscous resistance has been reduced by the above-mentioned reflux action to the tank 12 has a negative pressure of -0 in the circuit leading to the pump 2,
3kg/co? Below, the electromagnetic switching valve 37 is
Since the switch is automatically made to the boat, the state is switched to the normal state in which the hydraulic oil flows to the lift pilot valve 10.

However, even when the negative pressure is as high as -0.3 kg/ca1 or more, if the lifting solenoid valve 14 is turned on by the microcomputer 35, the solenoid switching valve 37 is automatically switched to the B port, and the lift arm 29 is -L can be elevated.

In the example shown in FIG. 1, the electromagnetic switching valve 37 is disposed in the oil path between the pump 2 and the relief valve 3 and before the diversion valve 4, but the diversion valve 4 and the control valve 5 are It suffices if the oil passage is placed between the control valve 5 and the oil passage before entering the control valve 5. Further, although not shown, the negative pressure sensor 36 may be a temperature sensor. If a temperature sensor is used, the electromagnetic switching valve 37 will be switched to the A boat when the temperature of the hydraulic oil flowing in the oil passage is below +10°C, and to the B boat when the temperature is above +10°C. When the temperature is below +10°C and a raise signal is output from the microcomputer 35, the port is automatically switched to B, and the lift arm 29 can be raised. When a temperature sensor is used, there is an advantage that malfunctions due to dust clogging in the hydraulic oil can be reduced.

In FIG. 1, reference numeral 18 denotes a hydraulic cylinder for horizontal posture control of a working machine, which is installed approximately in the longitudinal direction of the lift rod 127 on one side of the lift rods 27 installed on the left and right sides. Even when the machine is tilted, the working machine can be maintained in a horizontal position by expanding and contracting the hydraulic cylinder 18, but this hydraulic cylinder 18 is controlled by switching the electromagnetic switching valve 19.

Further, as shown in FIG. 7, the pump 2 is attached to the side of a timing case 41 installed at the front of the engine 21, and a pump gear 43 is spline-fitted to the pump shaft 2a.
is driven by an intermediate gear 44 that meshes with a timing gear (not shown). Ball bearings 45 and 46, whose inner diameters fit into both ends of the pump gear 43, have their outer diameters supported by the support portion of the timing case 41, and are sealed ball bearings.

Even if the internal pressure of the pump 2 becomes abnormally high and the pump shaft oil seal 47 comes off, the hydraulic oil is transferred to the ball bearing 4 with the seal.
5 and 46 to prevent it from entering the engine 21 through the timing case 41. At the same time, the safety device 55 is activated and the engine 2 is automatically shut down.
1 can be stopped. In this safety device 55, the pressure of the hydraulic oil flowing out through the spline fitting portion in the direction of the arrow shown by the dotted line is increased in the space 49, and due to this pressure increase, the pressure sensor 50 facing the space 49 is turned ON. Activated relay 5
1 switches the contact 52 and turns the start switch 53 OFF.
At the same time, the solenoid 54 is energized and the fuel injection pump 56 stops supplying fuel to the engine 21.
automatically stop.

Furthermore, the pressure sensor 50 may be used to warn of abnormal conditions using an alarm lamp, a buzzer, or the like.

This pump 2 is connected to the transmission case 12 which also serves as a tank through a suction pipe 57, and to the hydraulic case 34 through a pressure vibe 59.

〔Effect of the invention〕

As explained above, the present invention provides an ascent pilot valve and a descending pilot valve disposed in an oil passage between a hydraulic cylinder and a pump, respectively, which are controlled by a microcomputer, and which are controlled by a microcomputer. Even in lift devices for agricultural machinery that are controlled by valves, by installing a return mechanism in the oil path in front of both pilot valves that allows only the hydraulic oil with high viscous resistance to flow back into the tank. At low temperatures, the hydraulic oil with high viscous resistance is not sent to both pilot valves, so the ascending pilot valve or descending pilot valve as a control mechanism malfunctions due to the low Au & high viscous resistance of conventional hydraulic oil, causing the neutral or descending pilot valve to malfunction. This solves the problem of the lift device rising despite a descending command.

Therefore, it is possible to provide a hydraulic lift device for agricultural machinery that does not malfunction at low temperatures when the viscous resistance of the hydraulic oil is large.

[Brief explanation of the drawing]

Fig. 1 to Fig. 7 show one embodiment of the present invention, Fig. 1 is a hydraulic circuit diagram of the main part, Fig. 2 is a control circuit of the main part, Fig. 3 is a flow chart diagram, and Fig. 4 is a diagram of other parts. FIG. 5 is a schematic side view of the agricultural tractor, FIG. 6 is a cross-sectional view showing the lift device in the ascending position, and FIG. 7 is a detailed view of the pump mounting portion. FIG. 8 is a hydraulic circuit diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1... Filter, 2... Pump, 5... Control mechanism, 7... Hydraulic cylinder, 10... Pilot valve, 15... Pilot valve, 14... Solenoid valve for lift, 16 ... Solenoid valve for lowering, 35 ... Microcomputer, 3
6... Negative pressure sensor, 37... Solenoid switching valve (return mechanism). Applicant Mitsubishi Agricultural Machinery Co., Ltd. Agent Patent Attorney Shin Ogawa −

Claims (1)

[Claims] An ascending pilot valve and a descending pilot valve arranged in the oil passage between the hydraulic cylinder and the pump are connected to an ascending solenoid valve and a descending solenoid valve controlled by a microcomputer, respectively. A hydraulic lift device for agricultural machinery that is equipped with a return mechanism in the front oil path that allows only hydraulic oil with high viscous resistance to flow back into the tank.