JPS60195236A - Liquid pressure circuit for construction machine - Google Patents

Abstract

PURPOSE:To obtain optional slewing speed by a method in which a variable motor pump is turned at a set slewing speed by a pressure-proportional control valve without dependence on the discharge flow rate of a fixed pump, and the inertial force of the inertial body is converted into liquid pressure and recovered by an accumulator. CONSTITUTION:A fixed pump 8 is mechanically connected to a variable motor pump 3 to turn an inertial body 2, e.g., upper rotor, etc., and pipelines 9 and 10 are connected to the fixed pump 8. The serial circuit of pressure-reducing valves 11 and 11' and variable orifices 12 and 12', the flow directions of which are reversed, is provided between the pipelines 9 and 10. By the variable motor pump 3 through a pressure-proportional control valve 15, a closed circuit is made up of the fixed pump 8, the pressure-reducing valves 11 and 11', and the variable orifices 12 and 12' to a set slewing position. At a time when the discharge pressure of the orifices 12 and 12' exceeds a set pressure, the needle plate of the pump 3 is turned to the opposite direction, the inertial body is controllably driven, and discharged pressure oil is recovered by an accumulator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a hydraulic circuit for a construction machine that recovers the inertial energy of an upper rotating body or the like.

Prior art A conventional hydraulic circuit that recovers the inertial energy of an inertial body driven by a variable displacement motor pump (hereinafter referred to as variable motor pump) and uses it as driving force for the next operation is disclosed in German Patent No. 2739968, for example. The one shown in FIG. 1 described in . In the above hydraulic circuit, when the pressure proportional control valve d supplies υ hydraulic pressure to the servo cylinder C that controls the swash plate of the variable motor pump α, and the swash plate 6 is tilted, the variable pump e causes the swash plate to move into the accumulator f. The accumulated hydraulic pressure flows into the variable motor pump a, and an inertial body (not shown) connected to the variable motor pump α is driven. In addition, the variable motor pump α is provided with a mechanically linked fixed capacity pump (hereinafter referred to as fixed pump) A, which discharges liquid pressure to the servo cylinder C according to the speed as the variable motor pump α rotates. , variable motor pump α
At the same time as adjusting the rotation speed of the inertia body, when the inertia body reaches the operating position, tilt the acid 1 plate C of the variable motor pump α in the opposite direction to the previous rotation direction, and use the inertia of the inertia body to turn the variable motor bong a. It is configured to drive in reverse and collect and recover the hydraulic pressure discharged from the variable motor pump α into the accumulator f.

However, in the conventional hydraulic circuit described above, the discharge pressure of the fixed pump h connected to the variable motor pump a is directly flowed into the variable motor pump α, so the rotational speed of the variable motor pump α is determined by the discharge amount of the fixed pump h. Therefore, when used in construction machinery such as cranes and power shovels, there is a problem that delicate torque control cannot be performed. In addition, vibrations during work affect the output signal of the fixed pump h, so stable operation cannot be obtained, and the rotational speed adjustment of the variable motor pump α is dependent on the discharge amount of the fixed pump h. There was also a problem that the rotation speed of the variable motor pump α could only be adjusted to a speed corresponding to the rotation speed of the fixed pump h.

Purpose of the Invention The present invention was made with the aim of improving such problems, and provides a construction machine in which the capacity adjustment circuit of the variable motor pump and the circuit of the fixed bottom are made independent so that an arbitrary rotation speed can be obtained. The aim is to provide a hydraulic circuit for this purpose.

Structure of the Invention A variable motor pump that drives an inertial body is provided with an identification pump mechanically connected to the variable motor pump, and two pipe lines are connected to this fixed pump, and the flow direction is reversed between these pipes. The fixed pump, the pressure reducing valve and the variable orifice form a closed circuit until the variable motor pump reaches the rotation position set by the pressure proportional control valve. It enables the capacity adjustment of the variable motor pump without relying on a fixed pump, and when the outlet side pressure of the variable orifice reaches the set pressure,
By shutting off the pressure reducing valve and switching the pilot pressure regulating valve.

Hydraulic pressure for construction machinery is achieved by tilting the swash plate of the variable motor pump in the opposite direction to the rotation in I-11 to brake the inertial body and at the same time recovering the hydraulic pressure discharged from the variable motor pump to the accumulator. circuit.

Embodiment An embodiment of the present invention will be described in detail with reference to the drawing shown in FIG. 2. The figure shows a hydraulic circuit of a construction machine with an upper rotating body such as a power shovel as an inertial body (load). An inertial body 2, such as an upper revolving body, is rotatably supported on a vehicle body 1 having a leg turret (not shown), and one or more variable motor pumps 3 are mounted on the side of the inertial body 2. is installed. Each of the variable moke bombs 3 has a servo cylinder 4, and the swash plate 3 is controlled by the servo cylinder 4.
The tilting angle of α is controlled, and the servo cylinder 4 has a pilot switching valve 6 which is switched by the bilot pressure supplied from the capacity adjustment circuit 5.
Hydraulic pressure is supplied from the hydraulic pressure source 7 via the hydraulic pressure source 7.

On the other hand, the capacity adjustment circuit 5 is connected to a fixed pump 8 which is mechanically linked to the variable motor pump 3, and is configured as follows.

Pipe lines 9 and 10 are connected to the suction and discharge ports of the fixed pump 8, and between these pipe lines 9 and 10 there are pressure reducing valves 11 and 1bi whose flow directions are reversed, and variable orifices +2, +.
2' series circuits are provided over two rows. Each pressure reducing valve + 1, l +' and variable orifice + 2
, +2' is the spring II (E, +2α side, the pressure downstream of the variable orifice +2, +2' is introduced, and the pressure reducing valve +1, l 1' is on the opposite side from the spring IIZ, Pressure reducing valve 11, 1bi and variable orifice 12, 1
2' pressure is introduced. And the opposite side of the variable orifices +2, +2' to the springs 124 is connected to the conduit 1.
3, , + 4 are connected to a pilot pressure supply source 16 via a pressure proportional control valve 15, and from this pilot pressure supply source 16, a pilot pressure proportional to the operation amount of the pressure proportional control valve 15 is applied to a variable orifice. +2, +2'
As a result, each variable orifice + 2 , + 2' is opened and closed at an opening proportional to the operation amount of the pressure proportional control valve 15 .

On the other hand, reference numeral 17 is a hydraulic pressure source for the capacity adjustment circuit, and the hydraulic pressure from this hydraulic pressure source 17 is transmitted through the pipe 9. The IO pressure is supplied as a pilot pressure to both ends of the pilot switching valve 6 via pilot pressure regulating valves 18 and lg' introduced at both ends and pilot pipes 20 and 21. Further, on one end side of the pilot pressure regulating valve 18°+8', the pressure from the pressure proportional control valve 15 is further transmitted to the pipes +3', +4' branched from the pipe line 13.14 and the pilot switching valve 22°22'.
At the end of f111 opposite to the spring 22α of the pilot switching valves 22 and 22', a low pressure side is connected from a hydraulic pressure source 27 that supplies hydraulic pressure to the servo cylinder 26 of the variable pump 25. Hydraulic pressure is introduced via a cut-off valve 34.

The variable pump 25 is driven by the engine 29, and the liquid pressure discharged from the variable pump 25 is transferred to the pipe line 3.
0 through the check valve 31 and the variable motor pump 3
is being supplied to.

Further, a plurality of accumulators 32, two cut-off valves 33, 34, and an unload valve 35 are connected in the middle of the pipe line 30 connecting the check valve 31 and the variable motor pump 3. 2 cut-off valves 33.34
Among them, the cant-off valve 33 has, for example, 300 Ks+/
cm high pressure.

The cut-off valves 34 are each set to a low pressure of, for example, 200 KV'ctn, and the hydraulic pressure from the hydraulic pressure source 27 is applied to the servo cylinder 26 of the variable pump 25 via the pipe line 45 from the cut-off valves 33 and 34. A solenoid valve 37 is provided in the middle of the pipe line 45 and is supplied to a pilot switching valve 36 to be controlled. This solenoid valve 37 is connected to the pressure proportional control valve I5 in the pipe line 13゜1.
4 and is electrically connected to a pressure detector 38 operated by the pressure in these pipes 13 and 14, and this pressure detector 38 detects the pressure in the pipes 13 and 14 and turns on. In other words, while the inertial body is being driven by the variable motor pump 3, the stain magnetic valve 37 is set to position 37□ by the signal from the pressure detector 38, and the variable pump 25 is switched from the cut-off valve 34 with the lower set pressure to the variable pump 25. When the pilot switching valve 36-\pilot pressure for controlling the servo cylinder 26 and the pressure detector 38 are off, that is, when the inertial body is stopped, the solenoid valve 37 is in position 37□, and the pressure is lower than the cant-off valve 33 with a higher set pressure. Pilot pressure is supplied to the pilot switching valve 36.

Further, the pressure detector 38 is connected to the rotary shaft 3b of the brake electromagnetic stop variable motor bong 3, which is braked by a brake 40.

Next, to explain the operation, variable motor pump 3
When the pressure proportional control valve 15 is operated to drive the inertial body from the neutral position of the swash plate 3α, a pressure proportional to the operation amount is varied from the pilot hydraulic pressure source 12 via one of the pipes 1, for example 13. Orifice 12 and pilot pressure regulating valve 1g
supplied to. As a result, the pilot pressure regulating valve 18 is switched from position 181 to position 181.

Pilot pressure is supplied from the capacity adjustment hydraulic pressure supply source 17 to the right side of the servo cylinder 4 via the pipe 2I, and the servo cylinder 4 is switched from the neutral position 4 to the horizontal position 48. Since the pilot pressure is supplied to the accumulator 32, the hydraulic pressure accumulated in the accumulator 32 flows into the variable motor pump 3 through the conduit, and the variable motor pump 3 rotates, causing an inertial body (not shown) to rotate, for example, to the right. Fixed pump ε directly connected to variable motor pump 3 at the same time
is rotated and liquid pressure is discharged to the pipe line 9. After this liquid pressure is reduced by the pressure reducing valve 11, it flows into the conduit 10 through the variable orifice 12 opened by the pilot pressure from the pressure proportional control valve 15, and reaches the suction side of the fixed pump 8. As a result, the variable motor pump 3 is rotated at a speed proportional to the amount of operation of the pressure proportional control valve 15, so that a rotational torque proportional to the amount of operation can be obtained.

On the other hand, when the rotational speed of the variable motor bomb 3 reaches a constant speed, the discharge amount of the fixed pump 8 increases, and the discharge rate of the fixed pump 8 increases. , pressure reducing valve 11. The pressure in the closed circuit leading to the variable orifice 12 and the pipe line 10 increases, and the variable orifice 12 is shut off.As a result, the pressure between the pressure reducing valve 11 and the variable orifice 12 suddenly increases, and the pressure reducing valve 11 is shut off. Therefore, the pressure in the pipe line 9 is also high, and the pilot pressure regulating valve 18 returns to position 18+, and the pilot pressure in the pilot pipe line 21 is drained.

At the same time, the other pilot pressure regulating valve 18' is switched from position +81 to position +182, so the pilot pressure regulating valve 18' is switched from position +81 to position +182.
Pilot pressure is supplied to the left side of the servo cylinder 4, and the pilot switching valve 6 is at position 6°, and pilot pressure is supplied to the left side of the servo cylinder 4. As a result, the swash plate 3α of the variable motor pump 3 is tilted from the right turning side to the left turning side, so that a braking force is applied to the inertial body, and the variable motor pump 3 is reversely driven by the inertia of the inertial body. , discharges hydraulic pressure to the pipe line 30. This hydraulic pressure is stored in the accumulator 32 and becomes the next power source.

As mentioned above, the variable cheetah pump 3 does not depend on the discharge flow rate from the fixed pump 8, and uses the pressure proportional control valve 15 to rotate the inertial body to the desired rotation position according to the set rotational speed. At the same time, when the target turning position is reached, the inertial body is braked, and at the same time, the inertial force of the inertial body is converted into hydraulic pressure, which is recovered to the accumulator 32.

The above is the operation of a power shovel, for example, when working on level ground, but when working on a slope, gravitational inertia always acts on the inertial body, trying to rotate the variable motor pump 3 and the fixed pump 8. . However, by making the pressure proportional control valve 15 neutral, each pilot pressure regulating valve 1
No pilot pressure is supplied to 2° 12', and the pilot pressure regulating valves +2 and +2' remain closed. Press this to position 18. will be switched to. As a result, pilot pressure is supplied from the capacity adjustment circuit hydraulic pressure source 17 to the pilot switching valve 6 in order to turn the inertial body in the opposite direction to the direction in which it is intended to rotate due to gravitational inertia, so the turning force due to gravitational inertia is braked by this, and the natural rotation of the inertial body due to one gravitational inertia is suppressed.

Effects of the Invention As detailed above, the present invention provides a variable motor pump with a rotating torque proportional to the operation amount of the pressure proportional control valve, and since the capacity adjustment of the variable motor pump does not depend on the fixed pump, fine speed adjustment is possible. etc. can be easily performed simply by operating the pressure proportional control valve. In addition, while adjusting the capacity of the variable motor pump, the fluid pressure reduction is independent of that of the fixed pump, so even if there is a disturbance in the discharge amount of the fixed pump due to vibration, etc., it will not be affected. Since any rotational speed can be easily obtained, operability is further improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional hydraulic circuit, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 3 is a variable motor boiler, 8 is a fixed pump, 9°10 is a pipe, II, +1 is a pressure reducing valve, +2. +2t is a variable orifice, 15 is a pressure proportional control valve, 17 is a hydraulic pressure source for the capacity adjustment circuit, 18, +8' are pilot pressure regulating valves, 30 is a pipe, 32 is an accumulator 0 Applicant: Komatsu Ltd. Attorney Masaaki Yonehara Patent Attorney Tadashi Hamamoto

Claims (1)

[Claims] A fixed pump 8 is connected to a variable motor pump 3 that drives an inertial body, and as the variable motor pump 3 rotates, the fixed pump 8
The tilting angle of the variable motor pump 3 is controlled by the hydraulic pressure discharged from above, and the hydraulic pressure is supplied to the variable motor pump 3 through a conduit 30 connected to the variable motor pump 3. Also, a variable motor pump 3 driven by the inertia of an inertial body
In the device provided with an accumulator 32 for accumulating the discharge pressure from the fixed bonder 8, at least two pressure reducing valves 11 and 11 with opposite flow directions are provided between the two pipe lines 9 and 10 connected to the fixed bonder 8. ′ and variable orifice l 2 , +
2', a series circuit is provided, and the above pressure reducing valve + 1,
+ 1' own downstream pressure and variable orifice + 2
, +2' downstream pressure is introduced as pilot pressure,
Further, the variable orifices +2 and +2' introduce a pressure proportional to their own downstream pressure and the operation amount from the pressure proportional control valve 15 as a pilot pressure, and the variable orifices +2 and +2'
Pilot pressure regulating valves 18 and Ig' are provided, which introduce zero pressure at both ends and the pressure from the pressure proportional control valve 15 as pilot pressure at one end, and the capacity is adjusted through these pilot pressure regulating valves 18 and 18'. A hydraulic circuit for construction machinery in which the tilting angle of the swash plate of the variable motor pump 3 is controlled by supplying four pressures from a circuit hydraulic pressure source 17.