JPH0547722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic control device used to maintain a constant plowing depth of a working implement attached to, for example, an agricultural tractor.

[Prior Art] Working machines such as plows that are pulled by agricultural tractors are required to maintain a constant plowing depth at all times. Hydraulic control devices that automatically control the position and load of a working machine that affect plowing depth relative to set values are disclosed, for example, in Japanese Patent Laid-Open No. 54-2268 and Japanese Patent Publication No. 57-44845. In these conventional technologies,
When there is no load on the working machine, emphasis is placed on reducing the power consumption of the hydraulic pump by setting the hydraulic pump in an unloaded state and extending its durability.

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. Comparing and explaining the unloading performance and operability using the stroke and hydraulic characteristics of the spool, the second
As shown in the figure, the unloading performance is better as the stroke width S ₀ with respect to oil pressure changes is narrower, and the operability is better as the stroke width S ₀ is wider, and the impact that occurs when operating the work equipment can be alleviated.

[Problems to be Solved by the Invention] An object of the present invention is to provide first and second unloading valves integrally with the switching valve, and to initially operate the switching valve during the upward stroke of the working machine under hydraulic pressure. To provide a hydraulic control device in which hydraulic pressure supplied from a source to an actuator is throttled, first and second unload valves operate in stages to gradually rise, and do not give a shock to a working machine.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention connects a switching valve between a hydraulic power source and an actuator,
Oil is applied to the land of the spool that blocks and communicates between the first annular groove connected to the inlet and the second annular groove connected to the outlet provided in the valve chamber of the switching valve, according to the stroke of the spool from the neutral position to one side. An axial notch is provided to gradually increase the flow rate, and the axial distance between the second annular groove and the annular groove of the spool that communicates with and blocks the oil tank is made shorter than the notch, and the cylindrical shape of the spool is A valve body is inserted into the inner cavity of the valve body to partition a first chamber connected to the second annular groove and a second chamber connected to the first annular groove, and the oil pressure of the first chamber and the force of the spring are A valve hole is provided in the peripheral wall of the second chamber to gradually reduce the flow rate of oil flowing from the second chamber to the oil tank according to the stroke of the valve body.

[Function] The spool is equipped with a notch that controls the oil amount in a small stroke range from the neutral position.
A sudden increase in the amount of oil to the actuator during the upward stroke of the work equipment is suppressed, and the amount of oil returned to the oil tank of the first and second unload valves, which operate in stages, is reduced, allowing the actuator to move slowly. Start.
When the lifting stroke of the work equipment is completed, the inlet passage is
The unloading state is set by the unloading valve.

[Embodiments of the Invention] As shown in FIG. 3, a hydraulic control device 80 according to the present invention includes a switching valve A, an unloading valve B integrated with the switching valve A, a check valve C, and a descending valve D. We are prepared. Pressure oil is supplied to the hydraulic control device 80 from the discharge port of the hydraulic pump 65, and is returned to the oil 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's summery. A known relief valve 64 is connected between the discharge port of the hydraulic pump 65 and the oil tank T.

An operating rod 26 is attached to the spool of the switching valve A, and a pair of operating plates 68 are engaged between the operating rod 26 and a pair of rods 70, which will be described later.
The pair of operation plates 68 each have a pair of rods 6 guided in a direction perpendicular to the direction of movement of the operation rod 26.
9 by a pin. One rod 69 is remotely moved left and right in the figure by a draft setting lever 66 via a cable, and the other rod is remotely moved left and right in the figure by a position setting lever 67. Rod 35 of actuator 34 is connected to one end of bell crank 74. The other end of the bell crank 74 is connected to the link 63.

The bell crank 74 is fixed to a rotating shaft 73, and the displacement of the position sensor 71, which is biased and engaged with a cam 72 provided on the rotating shaft 73, is controlled by one of the aforementioned rods 70 (lower operation plate 68 in the figure). (which engages with)
transmitted remotely by cable to

A plow 78 serving as a working machine is connected to the machine body via a lower arm 79, while an intermediate portion of the lower arm 79 is connected to a bell crank 74 via a link 63.
connected to. Also, the lower arm 79 is connected to the link 7
The plow 78 is connected to the upper arm 76 via the plow 7, thereby maintaining the posture of the plow 78 horizontally. The inclination of the upper arm 76 is detected by the draft sensor 75, and the mechanical displacement of the draft sensor 75 is detected by the rod 70 (which is engaged with the upper operation plate 68).
transmitted to. 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.

A feature of the present invention is that the first and second unload valves are integrated into the switching valve A. As shown in FIG. 1, the switching valve A is constructed by fitting a hollow spool 27 into a cylindrical valve chamber 28 provided in a main body 60 having three mounting screw holes. First and second annular grooves 21 and 18 are formed in the center of the valve chamber 28, and annular grooves 15 and 23 are formed on the outside, respectively. Valve chamber 2
A large diameter cylindrical part 28a having a screw hole at the left end of 8.
is formed, and a cap 49 is screwed onto the cylindrical portion 28a. The right 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 left end of the spool 27.

The discharge port of the hydraulic pump 65 communicates with the annular groove 21 via the inlet passage 11, and the annular groove 18 communicates with the outlet passage 13.
It communicates with check valve C through. The first unload valve is constituted by an annular groove 15 and an annular groove 14. The axial distance s between the annular groove 15 and the annular groove 14 is made shorter than a notch 19, which will be described later. The annular groove 23 and the cylindrical portion 28a communicate with the oil tank T.

On the outer peripheral surface of the spool 27, there is an annular groove 14 that communicates and blocks communication between the cylindrical portion 28a and the annular groove 15, an annular groove 17 that blocks and communicates between the annular groove 15 and the annular groove 18, and an annular groove 18 and an annular groove. An annular groove 20 that blocks and communicates between the grooves 21 is provided, and a notch 19 is provided at the edge of the annular groove 20 (a part of the land between the annular groove 17 and the annular groove 20). The annular groove 15 and the annular groove 18 may be formed integrally, and the annular groove 17 may be omitted.

The second unload valve B is constructed as follows. A cylindrical inner cavity 16 is formed in the spool 27, and a valve body 57 having a plug 25 and an annular groove 22 is fitted into the inner cavity 16. Inner cavity 16 by valve body 57
A first chamber 61 and a second chamber 58 are divided. When the hydraulic pump 65 is stopped, the force of the spring 55 housed in the first chamber 61 presses the valve body 57 against the plug 25, and the plug 25 is pressed against the operating rod 26. An annular groove 20 and an annular groove 2 on the spool 27
A radial passage 4 connecting the annular groove 2 and the annular groove 2 is provided.
The pressure oil of No. 1 has a passage 4, an annular groove 22, a radial passage,
It enters the second chamber 58 via the axial passage and the valve body 5
7 is configured to exert pressure on the right end of the 7. Further, a valve hole 2 is provided in the spool 27 to communicate and cut off the second chamber 58 with the annular groove 23. Inner cavity 16
A first chamber 61 accommodating a spring 55 communicates with the annular groove 15 via a radial passage 54 .

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

The descending valve D is constructed by fitting a hollow spool 10 into a cylindrical portion 12 provided in a main body 60, closing the right end of the spool 10 with a plug 29, and interposing a spring 3 between the spool 10 and the plug 29. configured. Cylindrical part 12
The left end portion of the chamber 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 passageway having a throttle 9 communicating the chamber 7 and the chamber 41 in the inner space of the spool 10;
A check valve 8 is provided to prevent flow from chamber 7 to chamber 41. Further, a radial passage 6 connecting the chamber 7 and the annular groove 5 is provided in the spool 10. Check valve 8
is opened when pushed to the right by the push rod 42, and when the spool 10 is pushed directly to the right by the push rod 42, the chamber 41 and the annular groove 5 are brought into communication.

The push rod 42 is slidably supported by the main body 60 and is biased away from the spool 10 by a spring 43 interposed between a flange 44 provided at the outer end of the push rod 42 and a wall of the main body 60. , and is abutted against the sensitivity adjustment bolt 47 of the arm 45. The sensitivity adjustment bolt 47 is adjustably screwed into the arm 45, and its adjusted position is fixed by a lock nut 46. A passage 32 communicating with the annular groove 5 is opened in the cylindrical part 12, and the passage 32 is connected to the actuator 3.
4 and the valve chamber 39 of the check valve C. The chamber 41 is communicated with the oil tank T.

The check valve C has a poppet 40 pressed by a spring 37 to the outlet passage 13 that opens at the end of the valve chamber 39.
It is equipped with Poppet 40 is connected to piston 36 which is slidably fitted into valve chamber 39. Spring 3
The chamber housing 7 is connected to the oil 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, which is in the neutral position shown in FIG.
communicates with the annular groove 18, and at the same time, the annular groove 17 communicates the annular groove 18 with the annular groove 15. Then,
The annular groove 15 and the cylindrical portion 28a are cut off. Pressure oil flows from the annular groove 15 through the passage 54 to the first chamber 61.
and push the valve body 57 to the right as shown.

However, while the stroke of the spool 27 is small, the pressure oil in the annular groove 21 flows through the passage 4 and into the annular groove 2.
The oil enters the second chamber 58 through the valve hole 2 and exerts a force pushing the valve body 57 to the left, and flows out from the second chamber 58 through the valve hole 2 and the annular groove 23 to the oil tank T. As the stroke of the spool 27 to the left increases, the space between the second chamber 58 and the valve hole 2 is gradually narrowed, the oil pressure in the annular groove 18 gradually increases, and the poppet of the check valve C is removed from the outlet passage 13. 40 is pushed open and enters the chamber of the actuator 34 via the valve chamber 39 and passage 33, and the working machine is raised via the rod 35.

In this way, when the spool 27 moves to the left,
Initially, from the annular groove 21 to the annular groove 18 by the notch 19.
Since the pressure oil flowing to the outlet 13 is throttled, there is less impact, and when the gap s between the annular groove 15 and the annular groove 14 closes, the oil pressure from the annular groove 18 to the outlet 13 gradually increases. When the pressure oil reaches the actuator 34, the oil pressure at the outlet 13 temporarily increases due to the load on the actuator 34, and the oil pressure in the annular groove 21 is released to the oil tank T through the second chamber 58 and the valve hole 2, and suddenly This suppresses the increase in hydraulic pressure to the actuator 34. At the same time, the oil pressure at the outlet 13 is applied to the annular groove 18, the annular groove 17,
The oil acts on the chamber 61 through the annular groove 15 and the passage 54 and pushes the valve body 57 to the right, so that the valve hole 2 is finally closed and the entire amount of oil from the hydraulic pump 65 is thereafter supplied to the actuator 34. The rod 35 of the actuator 34 rises slowly without impact, and the speed gradually increases as the oil pressure increases.

When the work equipment rises to a predetermined height, the spool 27 is pushed back to the right along with the operating rod 26 by the feedback mechanism consisting of the position sensor 71, cable, rod 70, and operating plate 68, resulting in the neutral state shown in FIG. Become.

When the spool 27 is returned to the right, the annular groove 21
The pressure oil flowing from the outlet passage 13 to the annular groove 18 is throttled by the notch 19 and the pressure gradually decreases, and the hydraulic pressure sent from the outlet passage 13 to the actuator 34 via the check valve C also decreases, so that the rising speed of the rod 35 gradually decreases. It lowers and comes to a slow stop without any shock. At this time, the poppet 40 of the check valve C closes the outlet passage 13, so the rod 35 of the actuator 34 stops at that position.

Further, the first chamber 61 includes the passage 54, the annular groove 15,
14 to the cylindrical portion 28a, the first
The oil pressure in the chamber 61 becomes atmospheric pressure, and the force pushing the valve body 57 to the right becomes weaker. The valve body 57 is pushed to the left by the hydraulic pressure applied from the annular groove 21 to the second chamber 58 via the passage 4 and the annular groove 22, and at the same time, the pressure oil in the second chamber 58 passes through the valve hole 2 and the annular groove 23. The oil is returned to the oil tank T, and the hydraulic pump 65 is placed in an unloaded state.

When raising the work machine as described above, the arm 45 of the spool 27 moves to the left from the state shown in the figure, and returns to the state shown in the figure by the feedback mechanism, but during this time, the check valve 8 and the spool 10 do not operate. Instead, the annular groove 5 and the chamber 41 are cut off.

Next, when lowering the work machine, when the operating rod 26 is moved to the right, the valve body 57 follows the operating rod 26 under the force of the spring 55, and the spool 26 is moved to the right.
7 also follows the force of the return spring 50, so no relative movement occurs between the valve body 57 and the spool 27. The annular groove 21 and the annular groove 18 are blocked by the land of the spool 27, and the pressure oil in the annular groove 21 enters the second chamber 58 via the passage 4 and the annular groove 22, and the valve body 57 is moved by the spring 55. It moves to the left against the force, fully opens the valve hole 2, and returns to the oil tank T via the valve hole 2 and the annular groove 23. In this way, it is placed in 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 enters the annular groove 5 of the descending valve D via the passage 33 and the passage 32. Before this, the push rod 42 is pushed by the arm 45 of the spool 27 and the check valve 8 is opened, so that the chamber 7 and the chamber 41 are communicated through the throttle 9.
Therefore, the oil returned to the annular groove 5 enters the chamber 7 through the passage 6, and is returned to the oil tank T through the throttle 9 and the chamber 41.

In this way, while the stroke of the spool 27 from the neutral position to the right is small, the actuator 34
The oil in the chamber 62 is slowly returned to the oil tank T. As the rightward stroke of spool 27 increases,
The spool 10 is connected to the spring 3 by the push rod 42.
The annular groove 5 and the chamber 41 are pushed to the right against the force of
The oil is then returned to the oil tank T.

[Effects of the Invention] As described above, the present invention connects a switching valve between a hydraulic power source and an actuator, and has a first annular groove connected to an inlet and a second annular groove connected to an outlet provided in a valve chamber of the switching valve. On the land of the spool that blocks and communicates with the groove,
An axial notch is provided that gradually increases the oil flow rate as the spool strokes from the neutral position to one side.
The distance in the axial direction between the second annular groove and the annular groove of the spool that communicates and blocks the second annular groove with the oil tank is made shorter than the notch, and the valve body is inserted into the cylindrical inner space of the spool. A first chamber connected to the second annular groove and a second chamber connected to the first annular groove are divided, and the second chamber is divided into a first chamber connected to the second annular groove and a second chamber connected to the first annular groove. Since a valve hole is provided in the peripheral wall of the second chamber to gradually reduce the flow rate of oil flowing from the oil tank to the oil tank, the oil amount is controlled at the start and stop of the actuator's upward stroke, and smooth acceleration and deceleration of the actuator can be achieved. , there is no impact when starting and stopping, improving operability and extending the life of the operating parts of the work equipment.

That is, due to the notch in the land of the spool, the amount of overlap between the annular groove connected to the inlet and the annular groove connected to the outlet gradually increases, and then the first unload valve configured between the valve chamber of the switching valve and the spool closes. , and then a second
The unload valve is gradually throttled, and the oil pressure at the outlet slowly rises.

According to the present invention, since the first unloading valve is configured between the valve chamber of the switching valve and the spool, and the second unloading valve is configured inside the spool, machining is required between the valve chamber and the spool. The cost is reduced and the overall size is reduced.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a hydraulic control device according to the present invention, Fig. 2 is a line diagram explaining the action of the hydraulic control device, and Fig. 3 is a schematic configuration diagram of a working machine equipped with the hydraulic control device. be. A: Switching valve, B: Unload valve, C: Check valve,
D: descending valve, 2: valve hole, 10: spool, 14:
Annular groove, 16: Inner cavity, 17, 20: Annular groove, 1
8, 21: second and first annular grooves, 19: notch, 2
7: Spool, 28: Valve chamber, 34: Actuator, 55: Spring, 57: Valve body, 58: Second chamber,
60: Main body, 61: First chamber.

Claims (1)

[Claims] 1 A switching valve A is connected between a hydraulic power source and an actuator, and a first annular groove 21 connected to an inlet and a second annular groove 1 connected to an outlet are provided in a valve chamber 28 of the switching valve.
In the land of the spool 10, which blocks and communicates with the spool 8,
An axial notch 19 is provided to gradually increase the oil flow rate as the spool strokes from the neutral position to one side, and the second annular groove 18 is connected to the oil tank.
Axial distance s between the spool to be blocked and the annular groove 14
is shorter than the notch, and a valve body 57 is inserted into the cylindrical inner space 16 of the spool to form a first chamber 61 connected to the second annular groove and a second chamber 58 connected to the first annular groove. The peripheral wall of the second chamber has a valve hole 2 that gradually reduces the flow rate of oil flowing from the second chamber to the oil tank in accordance with the stroke of the valve body due to the oil pressure in the first chamber and the force of the spring 55. A hydraulic control device for an actuator that drives a working machine, characterized in that it is provided in a section.