JPS6228501A - Hydraulic control device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an impact at starting and stopping, by a method wherein, in the raising and the lowering stroke of a working machine, an unload valve is actuated according to the opening of a high pressure passage by means of the spool of a switching valve. CONSTITUTION:An unload valve B, partitioning a pump pressure introducing chamber 58 from a pilot chamber 61, is provided in the interior of a switching valve A, annular grooves 14, 17, and 20 are formed in the outer peripheral surface of a spool 27 of the switching valve A, a notch 19 is provided in the edge part of the annular groove 20, and a hole 54 is formed around the pilot chamber 61 of the spool 27. This, at starting and stopping in the rising and the lowering stroke of an actuator 34, enables actuation of the unload valve B according to the opening of a high pressure passage through the working of the spool 27, and control of a flow rate to the actuator 34, resulting in the possibility to prevent the occurrence of an impact at starting and stopping.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention applies to hydraulic pressure 1iII used to maintain a constant plowing depth of a working machine attached to an agricultural tractor, for example. It concerns an Il device.

[Prior Art] Working machines such as plows that are pulled by agricultural tractors are required to maintain a constant plowing depth at all times. A hydraulic control device that automatically controls the position and load of a working machine that affects plowing depth according to a set value is known, for example, from Japanese Patent Application Laid-Open No.
It is disclosed in Japanese Patent Publication No. 2268 and Japanese Patent Publication No. 57-44845. In these conventional techniques, emphasis is placed on reducing power consumption of the hydraulic pump and extending its durability by setting the hydraulic pump in an unloaded state when there is no load on the machine.

However, another important point is the operability of the hydraulic control device, that is, the ability to obtain fine control with little impact due to operation. However, when emphasis is placed on operability, unloading performance is sacrificed to some extent. When unloading performance and operability are compared and explained using the stroke and hydraulic characteristics of the spool, as shown in Figure 2, unloading performance is affected by changes in hydraulic pressure (
The narrower the stroke width So is, the better the stroke width So is. The wider the stroke width So, the better the operability is. Particularly, it is possible to reduce the impact that occurs on the working machine during operation.

[Problems to be Solved by the Invention] An object of the present invention is to operate the unload valve according to the degree of opening of the high pressure passage by the spool of the switching valve during the ascending stroke and descending stroke of the working machine, thereby reducing the flow rate to the actuator. An object of the present invention is to provide a hydraulic control device that can control and prevent impact acting on a working machine during switching.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a high-pressure circuit that supplies pressure oil from a hydraulic source to an actuator via a switching valve and a check valve, and a high-pressure circuit that supplies pressure oil from a hydraulic source to an actuator through a switching valve and a check valve. In a hydraulic control position of an actuator that drives a working machine, the unloader is provided inside the switching valve and partitions the pump pressure introduction point and the pilot chamber. When the unload valve moves against a spring due to pump pressure, a passage connecting the input port of the switching valve to the tank, and when the switching valve is switched in the upward direction of the 7-cut unit, the switching valve opens. A passage connecting the output port to the pilot chamber and moving the unloaded valve in the direction of action of the spring, and a notch provided in the land of the spool that blocks the input port and output port of the switching valve. It is equipped with

[Function] Since the spool 27 is provided with the notch 19 that controls the flow rate in a small stroke range, the spool 25 suppresses a sudden increase in the flow rate during the upward stroke of the work equipment, and at the same time reduces the tank overflow rate of the unload valve. is controlled and starts slowly. When the lifting stroke of the working machine is completed, the unloading valve B brings the working machine into an unloading state, and the check valve C prevents the pressure oil from flowing back from the actuator 34.

During the descending stroke of the working machine, the flow rate of the oil in the actuator 34 is controlled by the throttle 9 within a small stroke range of the descending valve, and the working machine descends slowly without impact.

[Practical Examples of the Invention] The present invention will be explained based on examples. As shown in FIG. 3, the hydraulic control device 80 according to the present invention includes a switching valve A, an unloading valve B, a check valve C, and a lowering valve.

Pressure oil is supplied to the hydraulic control device 80 from the discharge port of the hydraulic pump 65, and is returned to the tank T via the unload valve B and the switching valve A, or is supplied to the actuator 34 via the check valve C. It has become. hydraulic pump 65
A known relief valve 64 is connected between the discharge port of the tank T and the tank T.

An operating rod 26 is attached to the spool of the switching valve A, and a rod 7o, which will be described later, is connected to the operating rod 26.
A pair of operation plates 68 are engaged. The pair of operating plates 68 are rotatably supported by pins on rods 69 that are guided in a direction perpendicular to the moving direction of the operating rod 26, respectively. One rod 69 is remotely moved left and right in the figure by a draft setting lever 65, and the other rod is remotely moved left and right by a position setting lever 67. The rod 35 of the actuator 34 is connected to one end of the bell crank 74, while the other end is connected to the link 63.

The bell crank 74 is fixed to the rotating wheel 73, and the position sensor 7 is biased by a cam 72 provided on the rotating shaft 73.
1 is remotely interlocked and connected with one of the aforementioned lots 70 (the one that engages with the lower operation plate 6 in the figure).

A plow 78 serving as a working machine is connected to the machine body via a lower arm 79, and its intermediate portion is connected to a bell crank 74 via a link 63.

Further, the lower arm 79 is connected to the upper arm 76 via a link 77, so that the posture of the plow 78 is maintained horizontally. The inclination of the upper arm 76 is detected by the draft sensor 75, and this mechanical displacement is detected by the front door 0 (
(which is engaged with the upper operation plate 68). The structure of the plow 78 as such a working machine is well known and is not directly related to the gist of the present invention, so it will not be described further.

As shown in FIG. 1, the switching valve A has a hollow spool 27 attached to a cylindrical portion 28 provided in a main body 60 having three mounting screw holes.
It is constructed by mating. The cylindrical portion 28 is formed with an annular groove 18.21 in the center and an annular groove 15.23 on the outside thereof. A large-diameter cylindrical portion 28a having a screw hole is formed at the left end of the cylindrical portion 28, and a cap 49 is screwed into the cylindrical portion 28a.

The right outer end of the spool 27 is operated by the operating rod 26 against the force of a return spring 50 interposed between the cap 49 and the spool 27. The annular groove 21 as an input port is connected to the discharge port of the hydraulic pump, and the annular groove 18 as an output port is connected to the check valve C via the passage 13.
are connected to each. Annular groove 23 and cylindrical portion 28a
is connected to tank T.

On the outer circumferential surface of the spool 27, an annular groove 14 that communicates and blocks communication between the cylindrical portion 28a and the annular groove 15, an annular groove 17 that communicates and blocks communication between the annular groove 15 and the annular groove 18, and an annular groove 18.
An annular groove 20 that communicates with and blocks communication between the annular groove 21 and the annular groove 21 is provided, and a notch 19 is provided at the edge of the annular groove 20 (the land between the annular groove 17 and the annular groove 20).

The unload valve B is constructed as follows. Spool 27
A cylindrical portion 16 is formed in the cylindrical portion 16, into which a plug 25 and a spool 57 having an annular groove 22 are fitted. This spool 57
A pilot v61 and a pump pressure introduction chamber 58 are defined in the cylindrical portion 16 by this.

When the hydraulic pump 65 is stopped, the spool 57 is pressed against the plug 25 by the force of the spring 55 housed in the pilot air 61, and this plug 25 is pressed against the operating rod 26. The spool 27 has an annular groove 20 and an annular groove 2.
2, the pressure oil in the annular groove 21 enters the pump pressure introducing chamber 58 through the passage 4, the annular groove 22, the radial direction passage, and the axial direction passage, and the pressure oil is transferred to the right end of the spool 57. is configured to exert Further, the spool 27 is provided with a radial passage 2 that is always in communication with the annular groove 23 and communicated with/blocked from the pump pressure introduction chamber 58 by the spool 57. A pump pressure introduction chamber 61 accommodating the spring 55 of the cylindrical portion 16 is communicated with the annular groove 15 via a passage 54 .

The arm 45 is fitted into a radial hole 53 provided at the left end of the spool 27, and is fixed with a bolt 51 so as not to come off. This bolt 51 is fastened with a lock nut 52. The arm 45 projects outward from a slit 48 provided in the wall of the cylindrical portion 28a of the main body 60.

The descending valve is constructed by fitting a hollow spool 10 into a cylindrical portion 12 provided in the main body 60, closing the right end portion with a stopper 29, and interposing a spring 3 between the spool 10 and the stopper 29. Ru. At the left end of the cylindrical portion 12, a seedling 41 is formed of a small-diameter cylindrical portion via a conical portion. The spool 10 is also provided with a conical portion that abuts the aforementioned conical portion, and is provided with an annular groove 5 on its outer peripheral surface. A passage having a throttle 9 that communicates between the chamber 7 and the chamber 41 is provided in the inner space of the spool 10, and a check valve 8 that prevents flow from the chamber 7 to the chamber 41 through this passage. Further, a radial passage 6 connecting the passage and the annular groove 5 is provided. The check valve 8 opens when pushed to the right by the bushing rod 42, and when the spool 10 is further pushed directly to the right by the bushing rod 42, the chamber 41 and the annular groove 5 are brought into communication.

The bushing rod 42 is slidably supported by the main body 60,
A spring 43 is interposed between the flange 44 provided at the outer end and the wall of the main body 60, and is biased in a direction away from the spool 10 and is applied to the sensitivity adjustment bolt 47 of the arm 45 mentioned above. will be combined. Sensitivity rIJ adjustment bolt 47 is screwed into arm 45 so as to be adjustable, and this adjusted position is fixed by lock nut 46. A passage 32 communicating with the annular groove 5 is opened in the cylindrical portion 12, and this passage 32 is connected to the chamber 62 of the actuator 34 and to the valve chamber 39 of the check valve C. v41 is connected to tank T.

The check valve C has a spring 3 in a passage 13 that opens at the end of the valve chamber 39.
It is provided with a poppet 40 that is pressed by 7. The guide portion 36 of the poppet 40 is fitted into the valve chamber 39 so as to vibrate. The chamber housing the spring 37 is connected to the tank T.

Next, the operation of the hydraulic control device according to the present invention will be explained. When the work machine is raised by the rod 35 of the actuator 34, when the spool 27 in the neutral position shown in FIG. 1 is moved to the left by the operating rod 26, the notch 1
The annular groove 21 and the annular groove 28 communicate with each other through the annular groove 9, and the annular groove 18 and the annular groove 15 communicate with each other through the annular groove 17, and pressure oil enters the pilot chamber 61 of the cylindrical portion 16 from the passage 54,
Push the spool 57 back to the right as shown.

However, if the stroke of the spool 27 is small,
On the other hand, the pressure oil in the annular groove 21 enters the pump pressure introduction chamber 58 through the passage 4 and the annular groove 22, exerts a force that pushes the spool 57 to the left, and the pressure oil flows from the pump pressure introduction chamber 58 into the passage 2.
and flows out into the tank T via the annular groove 23. Therefore, the amount of pressure oil sent to the annular groove 18 is reduced. As the stroke amount of the spool 27 to the left increases, the space between the passage 4 and the annular groove 23 is gradually closed, the pressure of the pressure oil in the annular groove 18 gradually increases, and the poppet 40 of the check valve C is transferred from the passage 13 to the annular groove 18. is pushed open, enters the chamber of the actuator 34 through the valve chamber 39 and passage 33, and raises the working machine via the rod 35. In this way, when the spool 27 moves to the left, the pressure oil flowing from the annular groove 21 to the annular groove 18 is initially throttled by the notch 19, so that the actuator 34
As the oil pressure increases gradually, the rod 35 rises slowly without impact, and the speed gradually increases as the oil pressure increases.

When the spool 27 rises to a predetermined height, the spool 27 is pushed back to the right by a feedback mechanism consisting of the position sensor 71, the cable, the rod 70, and the operation plate 68, resulting in the neutral state shown in FIG.

When the spool 27 is returned to the right, the pressure of the pressure oil flowing from the annular groove 21 to the annular groove 18 is throttled by the notch 19 and gradually becomes lower, and the oil pressure sent from the passage 13 to the actuator 34 via the check valve C also decreases. As the speed of the rod 35 decreases, the speed of the rod 35 gradually decreases, and the rod 35 slowly stops without any impact.

At this time, the poppet 40 of the check valve C closes the passage 13, so the rod 35 of the actuator 34 stops at that position.

Further, since the pump pressure introducing chamber 61 and the cylindrical portion 28a are communicated with each other through the passage 54 and the annular groove 15.14, the oil pressure in the pump pressure introducing chamber 61 becomes atmospheric pressure, and the force pushing the spool 57 to the right becomes weak. The spool 5 is caused by the hydraulic pressure applied from the annular groove 21 to the pump pressure introducing chamber 58 via the passage 4.
3 is pushed to the left, and at the same time, the pressure oil in the pump pressure introduction chamber 58 is returned to the tank T via the passage 2 and the annular groove 23, and the hydraulic pump 65 becomes unloaded.

When raising the work machine as described above, the spool 27
The arm 45 moves to the left from the illustrated state and returns to the illustrated state by the feedback mechanism, but during this time, the check valve 8 and the spool 10 do not operate, and the annular groove 5 and! 141
There is a cutoff between them.

Next, when lowering the work machine, when the operating rod 26 is moved to the right, the spool 57 follows the operating rod 26 under the force of the spring 55, and the spool 27 also follows under the force of the spring 50. Therefore, no relative movement occurs between the spool 57 and the spool 27. The land of the spool 27 blocks the annular rI 421 and the annular groove 18, and the pressure oil in the annular groove 21 enters the pump pressure introduction chamber 58 via the passage 4 and the annular groove 22, and the spool 57 is moved by the spring 5.
5 to the left to open a passage 2 from which it is returned to the tank T via an annular groove 23. In this way, it is brought into an unloaded state.

On the other hand, the rod 35 of the actuator 34 is pushed down by the load of the working machine, and the oil in the chamber 62 flows through the passage 33 and the passage 32 into the annular groove 5 of the descending valve. Before this, the bushing rod 42 is pressed against the check valve 8 by the arm 45 of the spool 27 and opened, so that the chamber 7 and the chamber 41 are connected to the throttle 9.
communicated via. Therefore, the oil returned to the annular groove 5 enters the cavity 7 via the passage 6, is calibrated by the calibrator 9, and is returned from the chamber 41 to the tank T.

In this way, the oil from the actuator 34 to 42 is slowly returned to the tank T while the stroke of the spool 27 from the neutral position to the right is small. When the stroke of the spool 27 increases, the bushing rod 42 directly pushes the spool 10 of the descending valve to the right. When the spool 10 is pushed to the right against the force of the spring 3, the annular groove 5 and the chamber 41 are brought into direct communication and the oil in the passage 32 is returned to the tank r via the annular groove 5 and the cavity 41.

At this time, since the flow from the actuator 34 to the tank T is suppressed by the throttle 9, the rod 35 of the actuator 34 slowly descends without receiving any impact.

[Effects of the Invention] As described above, the present invention provides an unload valve that is provided inside a switching valve that supplies pressure oil from a hydraulic pump to an actuator that drives a working machine, and that partitions a pump pressure introduction chamber and a pilot chamber. When the unloading valve moves against a spring due to pump pressure, a passage connects the input port of the switching valve to the tank; and: When the switching valve is switched in the upward direction of the actuator, the output port of the switching valve opens. and a passage for connecting the unloading valve to the pilot seedling and moving the unloading valve in the direction in which the spring acts; and a notch provided in the land of the spool for blocking the input port and the output port of the switching valve. Because of this, the amount of oil is controlled when starting and stopping the actuator in its upward and downward strokes, resulting in smooth acceleration and deceleration of the actuator, preventing impact during starting and stopping, and improving operability. In other words, the amount of overlap between the high pressure circuit (passage connected to the hydraulic pump) and the low pressure circuit (passage connected to the tank T) in the notch provided in the land of the spool increases, and the amount of oil in the throttle area is reduced, so that the actuator Shocks during starting and stopping are alleviated, thus extending the lifespan of the operating parts of the working machine.

After the actuator is raised, the unloading valve built into the switching valve ensures that the actuator is in the unloaded state, reducing the load on the hydraulic pump.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a hydraulic control device according to the present invention, and FIG.
The figure is a scale diagram for explaining the operation of the hydraulic control device, and FIG. 3 is a schematic diagram of a working machine equipped with the hydraulic control device. A: Switching valve B: Unloading valve C: Check valve D = Downward valve 10 Varnish spool 17.20: Annular groove 1B, 21:
Annular groove 19: Notch 25: Plug 27: Spool 34
: Actuator 42: Push rod 47: Sensitivity adjustment bolt 57: Spool 58: Pump pressure introduction chamber
60: Main body 61: Pilot room

Claims (1)

[Claims] An operation comprising a high-pressure circuit that supplies pressure oil from a hydraulic source to an actuator via a switching valve and a check valve, and a low-pressure circuit that connects the actuator to a tank via a descending valve. In a hydraulic control device for an actuator that drives a machine, the unload valve is provided inside the switching valve and partitions a pump pressure introduction chamber and a pilot chamber, and the unload valve is moved against a spring by the pump pressure. Then, a passage connecting the input port of the switching valve to the tank, and switching the switching valve in the upward direction of the actuator,
connecting an output port of the switching valve to the pilot chamber;
Driving a working machine characterized by comprising: a passage for moving the unloading valve in the direction in which the spring acts; and a notch provided in a land of a spool for blocking an input port and an output port of the switching valve. Actuator hydraulic control device.