JPH11141501A - Hydraulic motor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic motor control circuit capable of maintaining the normal start position of the free piston of a shockless cylinder at all times, and capable of miniaturizing the shockless cylinder. SOLUTION: One pair of relief valves 14, 15 are connected to between main paths 5, 6 linking a hydraulic motor 4 and a switching valve 3, and one pair of shockless cylinders 31, 32 are provided. Absorption chambers 18, 19 of the shockless cylinders 31, 32 communicate with the secondary pressure chambers 26, 27 of the relief valves 14, 15 respectively. The spring chamber 20 of the shockless cylinder 31 communicates with the absorption chamber 19 of the shockless cylinder 32 via a path 23, and the spring chamber 21 of the shockless cylinder 32 communicates with the absorption chamber 18 of the shockless cylinder 31 via a path 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic motor control circuit having a shockless function when a hydraulic motor in a construction machine such as a hydraulic shovel is stopped.

[0002]

2. Description of the Related Art A conventional hydraulic motor control circuit of this type is disclosed in Japanese Utility Model Laid-Open Publication No. Sho 62-2804, the contents of which will be described with reference to FIG.

The hydraulic motor 4 and the switching valve 3 are connected through a pair of main passages 5 and 6. The switching valve 3 is connected to the hydraulic pump 1 and the oil tank 2.

For example, when the switching valve 3 is switched from the illustrated neutral position to the left position L, the discharge oil of the hydraulic pump 1 flows into the hydraulic motor 4 through one main passage 5 and returns from the hydraulic motor 4. The oil flows into the other main passage 6
And flows into the oil tank 2 to rotate the hydraulic motor 4 forward.

Conversely, when the switching valve 3 is switched to the right position R, the oil discharged from the hydraulic pump 1 flows into the hydraulic motor 4 through the main passage 6 and the return oil from the hydraulic motor 4 flows through the main passage 5. After that, the oil flows into the oil tank 2 to reverse the hydraulic motor 4.

The upstream passages 7 and 8 of the pair of relief valves 14 and 15 are connected to the main passages 5 and 6, respectively. The passages 9 and 10 on the downstream side of the relief valves 14 and 15 are joined to each other. A makeup passage 11 is connected to the passages 9 and 10, and the makeup passage 11 is connected to the main passages 5 and 6 via check valves 12 and 13, respectively.

A pair of shockless cylinders 31 and 32 arranged in parallel with the relief valves 12 and 13 are connected to absorption chambers 18 and 19 and spring chambers 20 and 21 by free pistons 16 and 17 inserted therein. Each is partitioned. Springs are stored in the spring chambers 20 and 21, respectively. Each of the absorption chambers 18 and 19 has an orifice 2
They are connected to passages 7 and 8 connected to the upstream side of the relief valves 14 and 15 via passages provided with 4 and 25, respectively. The spring chambers 20 and 21 are connected to passages 9 and 10 connected to the downstream side of the relief valves 14 and 15, respectively.

As described above, in the state where the switching valve 3 is switched to the left position L and the hydraulic motor 4 is normally rotated, the switching valve 3
Is returned to the neutral position, the two main passages 5 and 6 are shut off by the switching valve 3. In addition, since the hydraulic motor 4 continues to rotate due to its inertia and performs a pumping operation, the pressure on the other main passage 6 side increases.

The pressure oil in the main passage 6 whose pressure has been increased in this way flows into the absorption chamber 19 of the shockless cylinder 32 through the orifice 25 and slides the free piston 17. As the free piston 17 slides, the volume of the absorption chamber 19 increases. And the absorption chamber 19
While the volume of the relief valve 1 is increasing, the pressure in the secondary pressure chamber 27 of the relief valve 15 is maintained low.
The set pressure of 5 is maintained at a low pressure. The time for setting the low pressure is determined by the increase in the volume of the absorption chamber 19 and the diameter of the orifice 25.

As described above, since the low pressure setting time of the relief valve 15 is kept short for a predetermined time after the hydraulic motor 4 starts pumping, a strong braking force does not suddenly act. That is, in the early stage of braking, the braking force is weak, so that no shock occurs in the hydraulic motor 4 as the inertial body.

When the free piston 17 reaches the stroke end from the above-described state, the pressure in the secondary pressure chamber 27 of the relief valve 15 increases, and accordingly, the relief valve 15 is set to the high pressure. Therefore, the braking force on the hydraulic motor 4 also increases.

When the hydraulic motor 4 is reversed, the same operation is performed by the shockless cylinder 31 and the relief valve 14.

[0013]

However, when the back pressure on the return side of the main passage 6 rises, for example, when the hydraulic motor 4 is rotating forward, the free piston 17 moves by the pressure action. I will. As described above, the free pistons 16, 17
Has moved, during braking, the volume increase time of each of the shockless cylinders 32 and 31 is shortened by the amount of the movement, so that there is a problem that the shock cannot be reliably absorbed.

An object of the present invention is to provide a control circuit which can easily prevent the free pistons of the respective shockless cylinders from moving due to the action of the back pressure when the hydraulic motor is driven.

[0015]

According to the present invention, there is provided a hydraulic motor control circuit having a shockless function as described above.
Each is characterized in that the spring chamber of one shockless cylinder is connected to the absorption chamber of the other shockless cylinder.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a system diagram of a control circuit, and FIG. 2 is a sectional view of a valve body including a check valve, a relief valve, and a shockless cylinder.

As shown in FIG. 1, the spring chamber 20 of the shockless cylinder 31 is connected to the absorption chamber 19 of the shockless cylinder 32 by a passage 23, and the spring chamber 21 of the shockless cylinder 32 is shockproof by a passage 22. It is suspended in the absorption chamber 18 of the cylinder 31. Other configurations are the same as those of the conventional control circuit shown in FIG.

In the valve body 33 shown in FIG.
6, Passage 7.8, Passage 9/10, Makeup passage 11
Are formed, and check valves 12 and 13 and relief valves 14 and 15 connected to the main passages 5 and 6, respectively, are closed. However, the passages 7 and 8 are not shown in the figure. Since the configurations of the relief valves 14 and 15 are the same, only one relief valve 15 will be described.

The relief valve 15 is provided with a poppet 29 on which the pressure on the side of the main passage 6 acts. The poppet 29 has an orifice 25 formed therein. The main passage 6 and the secondary pressure chamber 27 communicate with each other through the orifice 25. The free piston 17 is provided on the outer periphery of the secondary pressure chamber 27, and the secondary pressure chamber 27 and the absorption chamber 19 of the shockless cylinder 32 are connected through a communication hole 30.

As described in the control circuit, the spring chamber 20 of the shockless cylinder 31 is connected to the absorption chamber 19 of the shockless cylinder 32 by the passage 23.
The spring chamber 21 of the shockless cylinder 32 is connected to the absorption chamber 18 of the shockless cylinder 31 by a passage 22.

One main passage 5 communicates with the hydraulic pump 1 and the other main passage 6 communicates with the oil tank 2.
When the hydraulic motor 4 is rotated forward, the high-pressure oil in the main passage 5 on the supply side is supplied to the absorption chamber 18 of the shockless cylinder 31.
Through the passage 22 into the spring chamber 21 of the shockless cylinder 32. The back pressure of the main passage 6 on the return side acts on the absorption chamber 19 of the shockless cylinder 32. Therefore, since the pressure in the spring chamber 21 is higher than the pressure in the absorption chamber 19, the free piston 17 is pushed toward the absorption chamber 19 and is maintained at the normal start position.

The same applies to the case where the hydraulic motor 4 is reversely rotated by connecting the main passage 6 to the hydraulic pump 1 and the main passage 5 to the oil tank 2.

[0023]

As described above, according to the present invention, since the free piston of the shockless cylinder is always kept at the normal start position, the free piston can be moved through the entire stroke. Therefore, a sufficient time for maintaining the relief valve at a low pressure can be sufficiently obtained, and the shock of the hydraulic motor, which is the inertial body, can be reliably absorbed. In addition, by connecting the absorption chamber of one shockless cylinder to the spring chamber of the other shockless cylinder, the volume increase of the absorption chamber when pressure oil acts is doubled because the other free piston also moves. become. Therefore, in order to obtain the same effect as the initial shockless time, the moving distance of the free piston may be halved, and the shockless cylinder can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a hydraulic motor control circuit of the present invention.

FIG. 2 is a sectional view showing an embodiment of the valve body according to the present invention.

FIG. 3 is a system diagram showing a conventional hydraulic motor control circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Oil tank 3 Switching valve 4 Hydraulic motor 5 Main passage 6 Main passage 7 Passage 8 Passage 9 Passage 10 Passage 11 Makeup passage 12 Check valve 13 Check valve 14 Relief valve 15 Relief valve 16 Free piston 17 Free piston 18 Absorption Chamber 19 Absorption chamber 20 Spring chamber 21 Spring chamber 22 Passage 23 Passage 24 Orifice 25 Orifice 30 Communication hole 31 Shockless cylinder 32 Shockless cylinder 33 Valve body

Claims (1)

[Claims] A pair of main passages connected to a hydraulic motor are connected to a switching valve, and the switching valve is switched to any position to supply hydraulic oil from a hydraulic pump to drive the hydraulic motor. When the switching valve is returned to the neutral position, a pair of relief valves are connected between the main passages so as to exert a braking action on the hydraulic motor, and further, an absorption chamber and a spring chamber are partitioned by a free piston. A hydraulic motor control having a shockless function in which a pair of shockless cylinders is provided, and an absorption chamber of the shockless cylinder communicates with a secondary pressure chamber of the relief valve and communicates with a main passage through an orifice. An oil characterized in that, in each of the circuits, a spring chamber of one shockless cylinder is connected to an absorption chamber of the other shockless cylinder. Pressure motor control circuit.