JPH0333921B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is configured such that a pump port and a back pressure chamber of an unload valve are communicated with each other by a main spool. The main spool is equipped with a mechanism that gradually narrows the oil passage from the pump port to the cylinder port near the end of the stroke from the raised position to the neutral position, which communicates the back pressure chamber of the load valve and supplies pressure oil to the lift cylinder. The present invention relates to a position control valve for a hydraulic lift, in which a flow control relief valve having a back pressure chamber communicated with an oil passage portion on the cylinder port side of the throttle mechanism is connected to a pump port.

[Conventional technology]

The control valve with the above configuration is mainly used to control a hydraulic cylinder for lifting and lowering a working device connected to an agricultural tractor, and after driving the hydraulic cylinder to raise the working device, etc. When returning to the position, the relief valve operates to gradually stop the hydraulic cylinder and has the function of softening the shock that occurs when the lowering stops. Conventionally, this type of control valve has been disclosed, for example, in Japanese Utility Model Application Publication No. 57-53102.

[Problem that the invention seeks to solve]

In the conventional control valve described above, when the hydraulic cylinder is driven upward and stopped, the flow of hydraulic oil through the main spool is gradually restricted by the flat notch in the land, so the back pressure of the control valve is As a result, the hydraulic cylinder is able to perform a good operation of slowly stopping the hydraulic cylinder.

However, when considering forming a flat notch in the land of the main spool, this land is used to control the flow of pressure oil when the main spool is operating, so it is important to ensure that the land stops slowly. If the flat notch is formed too large for the purpose of this, the cylinder may overshoot, and normal control cannot be performed, and if it is formed too small, the above-mentioned slow stop function will be impaired.

Also, considering the slow speed stop function, the flat notch formed in the land functions as a throttle mechanism depending on its relative position with the valve body in which the main spool is housed. When forming a notch in the main spool, processing such as cutting is performed on the main spool while taking into consideration the internal shape of the valve body.

However, the valve body is typically cast and
Since it is manufactured by grinding only the space that accommodates the main spool, etc., as mentioned above, it is difficult to form a flat notch with a predetermined accuracy while taking into consideration the internal shape of the valve body. There is.

Incidentally, if this flat notch is not formed with a predetermined precision in each of the main spool and the valve body, an overshoot may occur when the valve is stopped, or even a shock may occur, so there is room for improvement.

An object of the present invention is to rationally configure a valve that can slowly stop a hydraulic cylinder without performing highly accurate machining.

[Means to solve the problem]

As described at the beginning, the feature of the present invention is that in a control valve formed of an unload valve, a main spool, a throttling mechanism, a relief valve, etc., when the main spool is operated from the raised position to the neutral position, the pump port An orifice for maintaining communication between the main spool and the cylinder port is formed in the main spool so as to act in parallel with the throttle mechanism, and its functions and effects are as follows.

[Effect]

In other words, when the main spool of the valve of the present invention is operated from the raised position to the neutral position, the oil passage between the pump port and the cylinder port is gradually throttled by the throttle mechanism, and the oil passage is Since oil flows through orifices arranged in parallel with the other hand, even if this throttling mechanism reaches a blocked state within a short period of time, the back pressure of the relief valve will not decrease rapidly. None.

In addition, since oil is allowed to flow between the pump port and the cylinder port through the orifice, this oil flow is less likely to become excessive, and the main spool does not reach the neutral position and the throttling mechanism is excessively throttled. In this state, the operation of the cylinder can be stopped.

In other words, in the present invention, not only the throttling mechanism is formed by machining the land of the main spool, but also the orifice that communicates the pump port and the cylinder port is formed. It is formed at a different position so that even if the throttle timing of the throttle mechanism deviates from the normal timing during operation, the slow speed stop operation will not be impaired, and the purpose is to ensure that the slow speed stop operation is performed reliably. There is also no need to form the aperture mechanism in a large notch.

〔Effect of the invention〕

Therefore, with the relatively simple structure of forming an orifice in the main spool along with a throttle mechanism,
A valve has been rationally constructed that can reliably stop a hydraulic cylinder at a slow speed without requiring high-precision machining.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 7, a pair of left and right lift arms 3 which are raised and lowered by a lift cylinder 2 are provided at the rear of the traveling vehicle body 1, and these lift arms 3 are connected to a lift rod 4.
A rotary type ground working device 6 is attached to the rear ends of a pair of left and right lower rings 5 which are connected to each other through a rear part of the vehicle body and are pivotally supported at the rear of the vehicle body, thereby forming a ground working device elevating section A of an agricultural tractor.

The hydraulic cylinder 2 is of a single-acting type, and the lift cylinder 2 includes:
An oil passage is formed so that hydraulic oil is supplied through a lift position control valve V provided in a transmission case M at the rear of the vehicle body, and this valve V will be described in detail below.

As shown in FIG.
a main spool 7 that controls the hydraulic oil supplied to the cylinder 2 and the oil drained from the cylinder 2 when the cylinder 2 is lowered; a check valve 8 that suppresses the oil drained from the cylinder 2;
A poppet valve 9 that opens only when the cylinder 2 goes down, an unload valve 10 that closes only when the cylinder 2 goes up, a flow control relief valve 11 that opens only when the cylinder 2 stops going up, etc. are provided. The unload valve 10 and the relief valve 11 are provided on both sides of an oil drain passage 12 formed in the casing of the valve V.

Moreover, this oil drain path 12 and the relief valve 11
This oil drain path 12 and a first oil drain path _B1 provided on the outer surface of the valve communicate with each other via an oil passage 12a.
It communicates with the unload valve 10 so as to be closable.

The casing of the valve V includes a pump port P located above the oil drain passage 12 and on the side of the main spool 7, a cylinder port C located approximately on the side of the check valve 8, and a poppet valve 9. A second oil drain port B ₂ is opened at a position substantially on the side of the pump port P, and pressure oil is always supplied to the pump port P, and the cylinder port C has an oil passage connected to the cylinder 2. Further, the second oil drain port _B2 is configured such that drain oil from the cylinder 2 flows only when the poppet valve 9 is opened.

The main spool 7 and the poppet valve 9
One side is provided with a bracket 14 that extends to the outside of the casing of the valve V, has one end fixed to the main spool 7 side with a nut 13, and has the other end abuttable to the poppet valve 9 side. There is.

The main spool 7 can be operated in three positions: a neutral position indicated by N in the same figure, a lift arm upward operating position indicated by U, and a lift arm descending operating position indicated by D. Only then will the bolt 15 attached to the bracket 14 come into contact with the end of the poppet valve 9 and open the poppet valve 9.

Next, the flow of hydraulic oil when operating the main spool 7 and the operation of the valve will be explained.

The main spool 7 has first large diameter portions 7 at two locations on the left and right.
a. A hole 16a is formed in the axial direction of the main spool 7 so that the second large diameter portion 7b is formed, and the pump port P and the oil passage portion Ca on the cylinder port side are always in communication. Communicating holes 16b, 1
An orifice 16 consisting of 6c is formed.

In the middle of operating the main spool 7 to the ascending operating position U shown in FIG. without being hindered by
It is supplied to the back pressure chamber 10a of the unload valve 10 through the oil passage 17, and the back pressure of the unload valve 10 and the pressure applied to this valve 10 through the oil drain passage 12 are balanced, and the back pressure of the valve 10 is The valve 10 is closed by a coil spring 18 provided in the valve.

At the same time as the valve 10 is closed, hydraulic oil flows through the orifice 16 into the oil passage 19 communicating with the check valve 8, presses the check valve 8, and resists the coil spring 20 provided on the back of the check valve 8. to open valve 8. Further, as the main spool 7 approaches the ascending operating position U, the hydraulic oil from the pump port P flows into the second large diameter portion 7b.
The air is supplied to the cylinder 2 via the open check valve 8.

Next, as shown in FIGS. 3 and 6, when the main spool 7 is operated from the ascending operating position U to the neutral position N, near the neutral position, the relief valve 11 is operated and the lift arm 3. Reduces impact when stopped. In other words, the oil passage 19 communicating with the cylinder port C of the second large diameter portion 7b of the main spool 7
A tapered land portion serving as the throttling mechanism L is formed on the side edge, and when this tapered land portion approaches the edge formed by the perforation Va in which the main spool 7 is housed and the oil drain path 12, the oil path The pressure in the back pressure chamber 11a of the relief valve 11, which communicates with another oil passage 21 from the upper side of the oil passage 19 through an orifice 22 formed in the casing, decreases, and the pressure in the back pressure chamber 11a of the relief valve 11 is reduced, and The pressure applied to the relief valve 11 increases, and this pressure oil opens the relief valve 11 against the coil spring 23 provided on the back surface of the relief valve 11.
The pressure oil from No. 2 is at the third oil drain port B ₃ outside the relief valve.
The pressure oil discharged through the cylinder 2 and supplied to the cylinder 2 gradually decreases. Subsequently, when the main spool 7 is operated to the neutral position N, the pressure of the hydraulic oil supplied to the cylinder port C via the oil passage 19 decreases, and the check valve 8 is closed, as shown in FIG. At the same time, the pressures applied to the relief valve 11 via the oil passage 21 and the oil passage 12a are balanced, and the relief valve 11 is closed by the biasing force of the coil spring 23. Also, at approximately the same time, the pressure oil on the back surface of the unload valve 10, which had been blocked by the first large diameter portion 7a, is discharged to the outside of the valve through the fourth oil drain port _B4 , so that the unload valve 10
In this case, the side pressure of the oil drain passage 12 is higher than the back pressure, and the opening operation is performed.

Next, as shown in FIG. 4, when the main spool 7 is operated to the lowering operating position D, the poppet valve 9 opens with this operation, and the hydraulic oil from the cylinder 2 flows through the cylinder port C and the oil passage 24. 2 oil drain port
B ₂ is reached and the lift cylinder 2 descends.
At this time, check valve 8, unload valve 1
0, the relief valve 11 maintains the state when the main spool 7 is operated in neutral.

The lift arm 3 and the main spool 7 are linked together via a position setting lever 27 so that the return of the main spool 7 to the neutral position is performed by a link mechanism (not shown) linked to the lift arm 3. , the lifting and lowering of the working device 6 is stopped at the operating position of the position setting lever.
Also, a spring 25 attached outside the case of the main spool 7
is for assisting the main spool 7 in returning to neutral.

A hydraulic circuit diagram of the aforementioned control valve V and its accompanying oil passage is shown in FIG. 5. In other words, the valve V corresponds to a block surrounded by an imaginary line, and the casing of the valve V has
A pump port P, a cylinder port C, etc. are formed, and a main spool 7, a check valve 8, a poppet valve 9, etc. are arranged inside the valve V, and
A drain oil passage 12, an oil passage 17, etc. are formed, and an oil passage from a hydraulic pump 26 is connected to the pump port P, an oil passage from the lift cylinder 2 is connected to the cylinder port C, and furthermore, an oil passage from the lift cylinder 2 is connected to the cylinder port C. A position setting lever 27 for operating the spool 7 and the lift arm 3 are linked.

[Another example]

Further, the present invention can be applied to various types of lift devices other than agricultural tractors, such as those for raising and lowering the reaping section of a combine harvester.

[Brief explanation of drawings]

The drawings show an embodiment of the hydraulic lift position control valve according to the present invention, in which FIG. 1 is a vertical cross-sectional view of the valve in the main spool neutral state, and FIGS. 2 to 4 show the valve in the main spool operating state. 5 is a hydraulic circuit diagram for driving the lift cylinder, FIG. 6 is an enlarged view of the main part of the main spool during operation, and FIG. 7 is a perspective view of the rear of the agricultural tractor. 2...Lift cylinder, 7...Main spool, 1
0... Unload valve, 10a... Back pressure chamber of unload valve, 11... Relief valve, 11
a...Relief valve back pressure chamber, C...cylinder port, P...pump port, L...throttle mechanism,
N: Neutral position of the main spool, U: Raised position of the main spool.

Claims (1)

[Claims] 1 The main spool 7 is configured to communicate and cut off the communication between the pump port P and the back pressure chamber 10a of the unload valve 10, and the main spool 7 connects the pump port P and the back pressure chamber 10a of the unload valve 10.
The main spool is connected to a mechanism L that gradually narrows the oil passage from the pump port P to the cylinder port C near the end of the stroke from the rising position U to the neutral position N, which communicates pressure oil to the lift cylinder 2. 7, and a flow control relief valve 1 in which a back pressure chamber 11a is communicated with an oil passage portion on the cylinder port side from the throttle mechanism L.
1 is connected in communication with a pump port P, and the pump port P and cylinder port C are in communication when the main spool 7 is operated from a raised position U to a neutral position N. This is a position control valve for hydraulic lift, in which an orifice 16 for maintaining the pressure is formed in the main spool 7 in a state where it acts in parallel with the throttle mechanism L.