JP2003028104A - Hydraulic circuit structure of elevation device of working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit structure of a working machine elevation device which uses only a hydraulic cylinder of a double acting piston, capable of pressing the working machine to paddy-fields with a proper ground pressure having a good followup characteristic while the merit of a single acting piston is utilized effectively. SOLUTION: The hydraulic cylinder 9 is formed from a double acting piston partitioned into a pair of oil chambers 9a and 9b, and in the oil passage leading from a pressure oil inlet/outlet 11a of a position control valve 11 to the hydraulic cylinder 9, a single-double motion changeover solenoid control valve 15 is installed which supplies the pressure oil from the inlet/outlet 11a to the contractive input side oil chamber 9a when changing-over into the double acting side is conducted and feeds the pressure oil in the expansion side oil chamber 9b to a pressure oil tank 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a working machine lifting device for lifting and lowering a working machine mounted on a mobile agricultural machine such as a tractor by expanding and contracting a hydraulic cylinder.

[0002]

2. Description of the Related Art Conventionally, there has been known a work machine lifting device in which a lift arm is attached to the rear part of a mobile agricultural machine such as a tractor, and a work machine supported by the lift arm is lifted and lowered by expanding and contracting a hydraulic cylinder. However, this type of work equipment lifting device generally uses a single-acting piston hydraulic cylinder.When raising the work machine, pressure oil is sent to the oil chamber of the hydraulic cylinder to extend the piston rod. In addition, when the working machine descends, the working machine descends by its own weight while circulating the pressure oil in the oil chamber to the pressure oil tank side to release the pressure oil and retracting the piston rod. It was

However, in the construction of the above-mentioned working machine lifting device, since the piston in the hydraulic cylinder expands and contracts only by receiving the pressure of the pressure oil supplied to the oil chamber, the movement of the piston rod particularly in the extension direction is It is free within a predetermined length determined by the volume of the oil chamber and the size of the cylinder case,
In the working state where the working machine attached to the lift arm is grounded in the field, for example, when working in a hard field where the working machine is a rotary tiller and resists its own weight, the tilling reaction force is large and the working machine itself jumps up. Not only will it be impossible to maintain a constant working depth, but when the working machine is a plow, it will fall due to its own weight as described above, so there will be a delay in response and it will not fall to a prescribed depth. That leaves room for improvement.

Therefore, if the working machine lifting device is constituted by a hydraulic cylinder that employs a double-acting piston instead of the single-acting piston hydraulic cylinder, the working machine is forcibly pressed downward by the compression operation of the hydraulic cylinder. As a result, it is possible to keep the tilling depth of the rotary tiller constant, eliminate the response delay of the plow or shorten the time to reach the predetermined depth, etc. When there are stones and other hard foreign matter inside, the downward pressure force causes damage, and the collision of these foreign matter with the working machine tends to cause damage or deformation of the working machine. Therefore, it is proposed that the above-described single-acting and double-acting hydraulic cylinders are provided, and that these are selectively used according to the type of working machine and the hardness of the field. Structure In that case, a hydraulic circuit for each hydraulic cylinder is required, and if the switching control is also included, it is unavoidable that the weight of the entire device increases and the device structure becomes complicated, which causes a problem of high cost. It was

[0005]

SUMMARY OF THE INVENTION The present invention is a study for improving the function of a working machine lifting device in view of the above situation.
It was created in the process of development, and its purpose is to use only the hydraulic cylinder of the double-acting piston, but while making effective use of the advantages of the single-acting piston, Positive pressure is also applied to the lowering direction of the lift arm that supports the work machine to increase the ground pressure of the work machine and prevent the work machine from rising even when the field is hard. It is an object of the present invention to provide a hydraulic circuit structure in a working machine lifting device capable of pressing the working machine to the field with a sufficient ground pressure.

[0006]

In order to solve the problems, a first technical means adopted by the present invention is a position control including a hydraulic cylinder for driving a lift arm and a pressure oil inlet / outlet port for the hydraulic cylinder. In a working machine lifting device configured to lift and lower a working machine, which is provided with a valve and is supported by the lift arm, by expanding and contracting a hydraulic cylinder, the hydraulic cylinder has a double-acting section defined by a pair of oil chambers. Shaped piston, and in the oil passage from the pressure oil inlet / outlet of the position control valve to the hydraulic cylinder, the oil passage connected to the compression side oil chamber of the hydraulic cylinder and the extension side oil chamber of the cylinder. A single-acting / double-acting switching electromagnetic control valve for controlling switching between an oil passage to be connected is provided as a second technical means. When the control valve is switched to the double-acting side, pressure oil is supplied from the pressure oil inlet / outlet of the position control valve to the compression side oil chamber of the hydraulic cylinder, and the pressure oil in the extension side oil chamber of the cylinder is It is characterized in that switching control is performed so that the fluid flows toward the pressure oil tank.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the figure, reference numeral 1 denotes a crawler tractor having a pair of left and right crawler traveling devices 2 and 2 provided at a lower portion of a machine body frame 3. And a driver's seat 6 is provided in a cabin 5 arranged substantially in the center of the body frame 3, and in a space from the rear of the driver's seat 6 to a mounting portion 7 provided at the rear of the body frame 3. Is provided with hydraulic equipment (not shown) including a hydraulic pump P, a work machine transmission, and the like, and a three-point link mechanism 10 including a lift arm 8, hydraulic cylinders 9, 9 and the like is provided on the outer surface of the mounting portion 7.
Is installed and the working machine (not shown) is installed on the crawler tractor 1.
It is configured to be mounted on the rear part of the vehicle so as to be able to move up and down.

As shown in FIG. 2, each of the hydraulic cylinders 9 and 9 is formed of a double-acting piston partitioned into a pair of compression side oil chamber 9a and extension side oil chamber 9b. The position control valve 11 that moves the rods 9c and 9c in and out by controlling the flow of pressure oil into and out of the chambers 9a and 9b, and moves the pressure oil into and out of the hydraulic cylinders 9 and 9 includes a lower solenoid valve 12 and a lower switching valve. The valve 12 ', the upper solenoid valve 13 and the upper switching valve 13' are provided, and the lower or upper solenoid valves 12 and 13 are provided.
By switching each of them, the rods 9c, 9c of the hydraulic cylinders 9, 9 are synchronously moved in and out. Reference numeral 14 is a pressure oil tank.

In the present invention, the oil connected to the compression-side oil chamber 9a is provided in the oil passage extending from the pressure oil inlet / outlet port 11a of the position control valve 11 to the oil chambers 9a and 9b of the hydraulic cylinders 9 and 9, respectively. A single-action / double-action switching electromagnetic control valve 15 for switching control between the passage A and the oil passage B connected to the extension side oil chamber 9b is interposed together with the flow control valve 16.

That is, in the single-acting / double-acting switching electromagnetic control valve 15, the upper solenoid valve 13 is switched in the direction of the thick solid line arrow at the switching position on the single-acting side shown in FIG. Then, the upper switching valve 13 'is also switched in conjunction with this, the pressure oil from the hydraulic pump P is pumped in the direction of the solid line arrow, and each hydraulic cylinder 9, via the flow control valve 16 and the oil passage B.
By supplying the pressure oil 9 to the extension side oil chambers 9b and 9b, the rods 9c and 9c respectively extend to drive the working machine supported by the lift arm 8 upward. Further, when the lower solenoid valve 12 is switched in the direction of the thick dotted arrow by turning on a lowering switch (not shown), the lower switching valve 12 'is interlocked with the switching operation of the lower switching valve 12' to receive the weight of the working machine and retract the rod. The pressure oil supplied to the extension side oil chambers 9b, 9b by 9c, 9c circulates in the oil passage B in the direction of the dotted arrow, and is pressurized via the flow control valve 16 and the single-action / double-action switching electromagnetic control valve 15. Oil tank 1
The pressure oil is returned to 4, and the work machine supported by the lift arm 8 is lowered by its own weight due to the compression of the rods 9c and 9c. For example, when the work machine is a rotary cultivator, when the work machine is a rotary tiller, Even when the working machine collides with stones or other hard foreign matter, the working machine itself can be prevented from being damaged or deformed by jumping up.

The lifting and lowering drive of the working machine via the lift arm 8 described above uses the hydraulic cylinders 9, 9 formed of double-acting pistons in the same retracting / moving operation as a conventional single-acting piston. However, in the present invention, by performing the switching control of the single-action / double-action switching electromagnetic control valve 15 in particular, the following working machine descending drive, which cannot be achieved by a hydraulic cylinder having only a single-action piston, is performed. You can

That is, in the case where the crawler tractor 1 is used for running the working machine in the field, as shown in FIG. 2, the single-acting / double-acting switching electromagnetic control valve 15 is switched to the single-acting position.
When the crawler tractor 1 starts to travel, and is switched to the double-acting side indicated by a white arrow in FIG. 3, and then the upper solenoid valve 13 is switched in the direction of the thick solid line arrow, the upper switching valve 13 'interlocked with this is switched. In the switching operation, as shown in the figure, the pressure oil from the hydraulic pump P is pressure-fed in the direction of the solid line arrow and is supplied to the compression-side oil chambers 9a and 9a of the hydraulic cylinders 9 and 9 via the oil passage A. By doing the rod 9
c and 9c respectively retract and operate, and the working machine supported by the lift arm 8 positively moves downward with respect to the lift arm 8 in cooperation with its own weight and the retracting operation of the rods 9c and 9c. Even when pressure is applied and the field is hard, the working machine can reach the required lowered position in a short time. The pressure oil supplied to the extension-side oil chambers 9b and 9b when the rods 9c and 9c are respectively retracted and operated is the oil passage B, the flow control valve 16 and the single-action / double-action switching electromagnetic control. It will be returned to the pressure oil tank 14 via the valve 15.

After that, the upper solenoid valve 13
If the upper switching valve 13 'interlocked therewith is returned to the original switching position, and the single-action / double-action switching electromagnetic control valve 15 is again switched to the single-action side shown in FIG. 2 to continue the field traveling work. , Hydraulic cylinders 9, 9 formed of double-acting pistons
Is in a normal control state of a working machine that uses a conventional single-acting piston, and as described above, the working machine collides with stones and other hard foreign matter in the soil of the field while the crawler tractor 1 is traveling in the field. Even if the working machine itself jumps up, it is possible to prevent the working machine from being damaged or deformed.

Further, the hydraulic circuit structure in the working machine lifting device having the above-mentioned structure is as shown in FIG.
The position control valve 11 including the lower solenoid valve 12, the lower switching valve 12 ', the upper solenoid valve 13, and the upper switching valve 13', and the hydraulic circuit such as the hydraulic pump P are not changed at all.
A hydraulic cylinder formed by a single-acting piston is changed to a hydraulic cylinder 9, 9 consisting of a double-acting piston, and a portion X surrounded by a dotted line of an oil passage from the pressure oil inlet / outlet 11a to the hydraulic cylinders 9, 9 The advantages of the single-acting type piston and the double-acting type piston were effectively utilized only by adding the extremely simple hydraulic circuit of adding the single-action / double-action switching electromagnetic control valve 15 and the flow control valve 16. It is possible to obtain a circuit structure, and it is possible to contribute to a reduction in manufacturing cost while improving the function of the working machine lifting device.

In summary, according to the present invention, the working machine supported by the lift arm is equipped with a hydraulic cylinder for driving the lift arm and a position control valve having a pressure oil inlet / outlet port for the hydraulic cylinder. In a working machine lifting device configured to be lifted and lowered by the expansion and contraction operation of a cylinder, the hydraulic cylinder is formed of a double-acting piston partitioned into a pair of oil chambers, and from the pressure oil inlet / outlet of the position control valve. Single-action / double-action switching that controls switching between the oil passage connected to the compression-side oil chamber of the hydraulic cylinder and the oil passage connected to the extension-side oil chamber of the hydraulic cylinder in the oil passage leading to the hydraulic cylinder. The solenoid control valve for the single-action / double-action switching is installed in the pressure control port of the position control valve when it is switched to the double-action side. Is supplied pressure oil to the reduced entry side oil chamber of the hydraulic cylinder, and because the pressurized oil expansion side oil chamber of the cylinder is switchable controlled to flow towards the hydraulic fluid tank,
At the start of work traveling in the field, pressure can be positively applied also in the descending direction of the lift arm, increasing the ground pressure of the working machine supported by the lift arm and lifting the working machine even when the field is hard. It is possible to reduce the variation of the working depth caused by it as much as possible, and without changing the conventional hydraulic circuit such as the position control valve and hydraulic pump, the hydraulic cylinder formed by the single-acting piston is used. By changing to a hydraulic cylinder consisting of a double-acting piston and adding a few hydraulic members including a solenoid valve for single-acting / double-acting switching, the advantages of the single-acting piston and double-acting piston were effectively utilized. It is possible to obtain a circuit structure, and it is possible to construct a hydraulic circuit structure that can switch between single-action and double-action while suppressing the manufacturing cost. You can press the working machine with the force field, in which exhibits an extremely useful new effect that.

[Brief description of drawings]

FIG. 1A is a plan view of a crawler tractor.
(B) is a whole side view same as the above.

FIG. 2 is a hydraulic circuit diagram showing connections of a position control valve, a single-action / double-action switching electromagnetic control valve, and a hydraulic cylinder.

FIG. 3 is a hydraulic circuit diagram showing connections of a position control valve, a single-action / double-action switching electromagnetic control valve, and a hydraulic cylinder.

FIG. 4 is a conventional hydraulic circuit diagram showing a connection between a position control valve and a hydraulic cylinder.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2B304 KA13 LA02 LA05 LB05 MA02                       PD07 PD17 PD19 PD20 PD33                       RA03 RA09                 3F333 AA12 AB01 FH08                 3H089 AA10 BB14 BB15 CC01 DA02                       DB12 DB46 DB48 GG02 JJ01                       JJ17

Claims (2)

[Claims] 1. A working machine supported by the lift arm, which comprises a hydraulic cylinder for driving a lift arm and a position control valve having a pressure oil inlet / outlet port for the hydraulic cylinder, is lifted and lowered by expanding and contracting the hydraulic cylinder. In the working machine lifting device configured as described above, the hydraulic cylinder is formed of a double-acting piston partitioned into a pair of oil chambers, and in the oil passage from the pressure oil inlet / outlet of the position control valve to the hydraulic cylinder. In addition, a single-action / double-action switching electromagnetic control valve for switching control between an oil passage connected to the compression-side oil chamber of the hydraulic cylinder and an oil passage connected to the extension-side oil chamber of the cylinder is installed. The hydraulic circuit structure in the working machine lifting device characterized by the above. 2. The single-action / double-action switching electromagnetic control valve supplies pressure oil from the pressure oil inlet / outlet of the position control valve to the compression side oil chamber of the hydraulic cylinder when the solenoid control valve is switched to the double acting side. The hydraulic circuit structure in the working machine lifting device according to claim 1, wherein the switching control is performed so that the pressure oil in the extension side oil chamber of the cylinder flows toward the pressure oil tank.