JP3691674B2 - Directional control valve of pump pressure control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a directional control valve of a pump pressure control circuit that drives and controls an inertial load of a construction machine, that is, an actuator for operating a swinging body in a hydraulic excavator, and in particular, pump pressure control at the time of swinging of the swinging body as an inertial load The present invention relates to a directional control valve that enables a smooth operation regardless of the rotation radius of the revolving structure.
[0002]
[Prior art]
In general, as a pump pressure control circuit for driving and controlling an actuator for operating an inertial load, that is, a hydraulic motor, a directional control valve 14 is connected to a discharge line 12 of the hydraulic pump 10 as shown in FIG. Then, a pressure generating means 20 is provided in a tank line 18 communicating with the tank 16 via the direction control valve 14, and a control pressure generated in the pressure generating means 20 is supplied to a pump discharge flow rate control means 24 via a signal line 22. It is known that the discharge flow rate of the hydraulic pump 10 is negatively controlled by applying the voltage to the.
[0003]
However, in this type of conventional pump pressure control circuit, the following three means are known as pump pressure control means when the inertia load is small. (1). Means for regulating spool stroke of directional control valve
(2). Means for providing a bypass passage
(3). Means for switching relief pressure setting of swing motor
Therefore, the means (1) for regulating the spool stroke amount of the directional control valve in the pump pressure control circuit shown in FIG. 2 (a) uses the pilot pressures 30a and 30b for turning when the inertia load is small. The stroke amount of the operation spool of the direction control valve 14 is regulated by reducing the pressure in the pressure-reducing means 34a, 34b by 32a, 32b. With this configuration, the center bypass passage in the throttle passage related to the discharge flow rate control of the hydraulic pump 10 in the directional control valve 14, that is, in the intermediate position I in the symbol diagram of the directional control valve 14 shown in FIG. The bleed-off can suppress the increase in pump discharge pressure.
[0005]
In addition, as shown in FIG. 3, the means for providing the bypass passage (2) connects a bypass passage 36 different from the center bypass passage 12a in the existing pump pressure control circuit to the upstream side of the pressure generating means 20. It is possible to suppress the increase in pump discharge pressure by disposing pressure oil to the throttle passage related to the discharge flow rate control of the hydraulic pump 10 in each direction control valve 14a, 14b, 14c by the external signal pressure 37. It is configured.
[0006]
Further, the means (3) for switching the relief set pressure of the swing motor is a relief valve in the hydraulic circuit 40 of the swing motor 38 for driving and controlling the inertia load connected to the direction control valve 14, as shown in FIG. The turning relief set pressure set by 42a and 42b is reduced by the external signals 44a and 44b so that the pump discharge pressure can be prevented from increasing.
[0007]
[Problems to be solved by the invention]
However, the above-described pump discharge pressure control according to the prior art has various problems to be solved.
[0008]
That is, in the means (1) for restricting the stroke amount of the operation spool of the direction control valve 14, a mechanism (34a, 34b) for reducing the spool switching signal pressure to the direction control valve 14 by the pressure reduction signal (32a, 32b). ) Is not only complicated, but there are also problems such as narrowing the lever operation width by regulating the stroke amount.
[0009]
Further, in the means for providing the bypass passage 36 of the above (2), when the turning operation is performed by the predetermined direction switching valve 14a and the operation spools of the other direction switching valves 14b are operated, those spools are operated. The bypass passage 36 must be blocked by the switching signal, which not only complicates the signal processing operation, but also requires that the bypass passage 36 be provided from the uppermost stream of the center bypass passage 12a to the upstream side of the pressure generating means 20. Therefore, there is a problem that a sufficient installation space is required and the structure is complicated.
[0010]
Further, in the means (3) for switching the relief set pressure of the swing motor 38, when the relief set pressure of the relief valves 42a, 42b is lowered, the movement amount of the operation spool until the relief operation is reduced, As in the case where the stroke amount of the spool is restricted, not only the lever operation width becomes narrow, but also there is a problem that the structure becomes complicated in order to make the relief valve capable of switching the set pressure.
[0011]
Therefore, as a result of extensive research, the present inventor has connected and arranged a directional control valve to the discharge line of the hydraulic pump, and provided pressure generating means on the tank line communicating with the tank via this directional control valve. By applying the control pressure generated in the means to the pump discharge flow rate control means via the signal line, the discharge flow rate of the hydraulic pump for driving the hydraulic motor that operates the inertial load connected to the direction control valve is negative. When the pump pressure control circuit is configured to control, an external signal is provided between an upstream bypass passage and a downstream bypass passage that form a center bypass passage disposed opposite to the operation spool of the directional control valve. A throttle valve that can adjust the flow rate is installed in parallel to simplify the configuration and move the swivel of the excavator as an inertial load. The driving of the actuator, have found that it is possible to smoothly accelerated regardless of the magnitude of the turning radius.
[0012]
Therefore, an object of the present invention is to perform a smooth operation regardless of the rotation radius of the swing body when performing the pump pressure control of the hydraulic pump when the swing body swings as an inertial load. An object of the present invention is to provide a directional control valve of a pump pressure control circuit that can be manufactured at a low cost with a configuration.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the directional control valve of the pump pressure control circuit according to the present invention has a directional control valve connected to the discharge line of the hydraulic pump, and the pressure is applied to the tank line communicating with the tank via the directional control valve. For generating an actuator for driving an inertial load connected to the directional control valve by applying a control pressure generated by the pressure generator to the pump discharge flow rate controller via a signal line. In the direction control valve of the pump pressure control circuit configured to negatively control the discharge flow rate of the hydraulic pump, an upstream bypass passage that forms a center bypass passage disposed opposite to the operation spool of the direction control valve; Between the downstream bypass passage, a throttle valve that can adjust the flow rate by an external signal is provided in parallel.
The directional control valve is a directional control valve for turning a hydraulic excavator, and a throttle valve whose flow rate can be adjusted by an external signal is operated between an upstream bypass passage and a downstream bypass passage forming a center bypass passage. An auxiliary spool is disposed in parallel with the spool, a bypass bleed notch is provided in the auxiliary spool, and the auxiliary spool is operated by a pilot signal pressure corresponding to the turning radius.
When the turning radius is large, the pilot signal pressure is not generated, and the bypass bleed notch of the auxiliary spool is blocked, so that the pump discharge pressure of the hydraulic pump rises, with an acceleration commensurate with the turning relief set pressure, Increase the speed of the revolving body,
When the turning radius is reduced, the pilot signal pressure corresponding to the turning radius is generated so as to increase, and even if the operation spool is moved by a full stroke, the operation of the throttle valve by the bypass bleed notch of the auxiliary spool, The pump discharge pressure of the hydraulic pump based on the control pressure generated in the pressure generating means is kept low, and the movement of the swivel body is accelerated in the same way as when the turning radius is large in terms of acceleration .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the direction control valve of the pump pressure control circuit according to the present invention will be described in detail below with reference to the accompanying drawings.
[0016]
FIG. 1 shows a turning direction control valve for a hydraulic excavator as an embodiment of a direction control valve in a pump pressure control circuit according to the present invention.
[0017]
That is, in FIG. 1, reference numeral 50 indicates a direction control valve. The direction control valve 50 is slidably inserted into a casing 52 so that a turning operation spool 54 is slidable, and a pair of supply / discharge oil passages 56 a and 56 b. A supply / discharge port 58a, 58b connected to the supply / discharge oil passages 56a, 56b, an inverted U-shaped supply oil passage 60 disposed inside the supply / discharge oil passages 56a, 56b, and the supply / discharge port. Discharge oil passages 62a and 62b connected to the tank 61 are provided outside the oil discharge passages 56a and 56b, respectively.
[0018]
A supply oil passage 65 and an upstream bypass passage 66 communicating with the hydraulic pump 64 are provided at the center of the supply oil passage 60, and downstream bypass passages 68 a and 68 b are provided on both outer sides of the upstream bypass passage 66. Is provided. The supply oil passage 60 and the supply oil passage 65 are connected via a check valve 70. On the other hand, the upstream bypass passage 66 is connected to the downstream bypass passages 68 a and 68 b by a bypass cut notch 55 provided in the operation spool 54.
[0019]
The downstream bypass passages 68a and 68b are connected via a pressure generating means 76 to a tank line 74 that is connected to the tank 61 led out to the outside, and a control generated in the pressure generating means 76. The pressure is supplied to the pump discharge flow rate control means 78 of the hydraulic pump 64 via the pump control signal line 77. With this configuration, the pump discharge flow rate discharged to the discharge line 81 of the hydraulic pump 64 is negatively controlled when the swing motor 80 as an actuator externally connected to the supply / discharge ports 58a and 58b is driven. In FIG. 1, reference numerals 82a and 82b denote protective members of the turning motor 80, respectively.
[0020]
In the present invention, however, an auxiliary spool 72 is disposed in parallel with the operation spool 54 between the upstream bypass passage 66 and the downstream bypass passage 68b forming the center bypass passage. A bypass bleed notch 73 is provided so that the auxiliary spool 72 is operated by a pilot signal pressure corresponding to the turning radius of the turning body.
[0021]
As described above, the configuration is such that only the front and rear of the center bypass passage of the operation spool 54 are bypassed by the bypass bleed notch 73 provided in the auxiliary spool 72, so that the other directional control valve (not shown) When operating the operation spool (other than the above), there is an advantage that a simple structure eliminates the need to block the bypass passage.
[0022]
Therefore, the direction control valve 50 according to the present embodiment having the above-described configuration increases the drive speed of the swing motor 80 as an actuator that moves the swing body of the hydraulic excavator as an inertia load. Without generating the pilot signal pressure Psp, the auxiliary spool 72 is held at the right position in the figure by the elastic force of the weak spring 75b with the oil chamber 75a at the tip being the tank pressure. That is, in this case, since the bypass bleed notch 73 of the auxiliary spool 72 is blocked, the pump discharge pressure of the hydraulic pump 64 increases as before, and the movement of the swinging body is increased at an acceleration commensurate with the swing relief set pressure. You can make it faster.
[0023]
Contrary to the above, when the turning radius is reduced, the pilot signal pressure Psp corresponding to the turning radius is generated so as to increase, and the auxiliary spool 72 moves in the left direction as shown in the figure by overcoming the elasticity of the spring 75b. To do. In this case, even if the operation spool 54 is moved to the right as shown in the drawing, the pressure oil in the supply oil passage 65 remains in the upstream bypass passage 66, the bypass bleed notch 73 of the auxiliary spool 72, and the downstream bypass passage 68b. Bleed on the route. Therefore, the pump discharge pressure of the hydraulic pump 64 based on the control pressure generated in the pressure generating means 76 is kept low by the action of the throttle valve by the bypass bleed notch 73 of the auxiliary spool 72, and the turning radius is large in terms of acceleration. The movement of the revolving structure can be increased at the same time.
[0024]
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention.
[0025]
【The invention's effect】
As is clear from the above-described embodiment, the direction control valve of the pump pressure control circuit according to the present invention is a tank line connected to the tank via the direction control valve by connecting the direction control valve to the discharge line of the hydraulic pump. A pressure generating means is provided in the actuator, and a control pressure generated in the pressure generating means is applied to the pump discharge flow rate control means via a signal line, thereby driving an actuator for operating an inertial load connected to the direction control valve. In the direction control valve of the pump pressure control circuit configured to negatively control the discharge flow rate of the hydraulic pump for the purpose, an upstream bypass that forms a center bypass passage disposed opposite to the operation spool of the direction control valve Between the passage and the downstream bypass passage, a throttle valve whose flow rate can be adjusted by an external signal is provided in parallel.
The directional control valve is a directional control valve for turning a hydraulic excavator, and a throttle valve whose flow rate can be adjusted by an external signal is operated between an upstream bypass passage and a downstream bypass passage forming a center bypass passage. An auxiliary spool is disposed in parallel with the spool, a bypass bleed notch is provided in the auxiliary spool, and the auxiliary spool is operated by a pilot signal pressure corresponding to the turning radius.
When the turning radius is large, the pilot signal pressure is not generated, and the bypass bleed notch of the auxiliary spool is blocked, so that the pump discharge pressure of the hydraulic pump rises, with an acceleration commensurate with the turning relief set pressure, Increase the speed of the revolving body,
When the turning radius is reduced, the pilot signal pressure corresponding to the turning radius is generated so as to increase, and even if the operation spool is moved by a full stroke, the operation of the throttle valve by the bypass bleed notch of the auxiliary spool, The pump discharge pressure of the hydraulic pump based on the control pressure generated in the pressure generating means can be kept low, and in terms of acceleration, the structure is such that the movement of the swinging body is increased as in the case where the turning radius is large. When controlling the pump pressure of the hydraulic pump during turning of the swinging body as an inertial load, it is possible to operate smoothly regardless of the turning radius of the rotating body, and to manufacture with a simple configuration at low cost Can do.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram showing a connection state between a main-part sectional structure and a hydraulic system showing an embodiment of a direction control valve of a pump pressure control circuit according to the present invention.
2A is a hydraulic system diagram showing an example of the configuration of a conventional pump pressure control circuit, and FIG. 2B is a main part symbol diagram of the directional control valve shown in FIG.
FIG. 3 is a hydraulic system diagram showing another configuration example of a conventional pump pressure control circuit.
FIG. 4 is a principal hydraulic system diagram showing still another configuration example of a conventional pump pressure control circuit.
[Explanation of symbols]
50 Direction control valve 52 Casing 54 Operation spool 55 Bypass cut notches 56a, 56b Supply / discharge oil passages 58a, 58b Supply / discharge port 60 Supply oil passage 61 Tanks 62a, 62b
64 Hydraulic pump 65 Supply oil passage 66 Upstream bypass passages 68a and 68b Downstream bypass passage 70 Check valve 72 Auxiliary spool 73 Bypass bleed notch 74 Tank line 75a Tip oil chamber 75b Spring 76 Pressure generating means 77 Pump control signal line 78 Pump Discharge flow rate control means 80 Swing motor 81 Discharge lines 82a and 82b Protective member

Claims (1)

A directional control valve is connected to the discharge line of the hydraulic pump, pressure generating means is provided in the tank line that communicates with the tank via this directional control valve, and the control pressure generated in this pressure generating means is pumped via the signal line. Direction control of a pump pressure control circuit configured to negatively control the discharge flow rate of a hydraulic pump for driving an actuator that operates an inertial load connected to the direction control valve by applying to a flow control means In the valve, a throttle valve whose flow rate can be adjusted by an external signal is arranged in parallel between an upstream bypass passage and a downstream bypass passage forming a center bypass passage disposed opposite to the operation spool of the directional control valve. Provided,
The directional control valve is a directional control valve for turning a hydraulic excavator, and a throttle valve whose flow rate can be adjusted by an external signal is operated between an upstream bypass passage and a downstream bypass passage forming a center bypass passage. An auxiliary spool is disposed in parallel with the spool, a bypass bleed notch is provided in the auxiliary spool, and the auxiliary spool is operated by a pilot signal pressure corresponding to the turning radius.
When the turning radius is large, the pilot signal pressure is not generated, and the bypass bleed notch of the auxiliary spool is blocked, so that the pump discharge pressure of the hydraulic pump rises, with an acceleration commensurate with the turning relief set pressure, Increase the speed of the revolving body,
When the turning radius is reduced, the pilot signal pressure corresponding to the turning radius is generated so as to increase, and even if the operation spool is moved by a full stroke, the operation of the throttle valve by the bypass bleed notch of the auxiliary spool, A pump characterized in that the pump discharge pressure of the hydraulic pump based on the control pressure generated in the pressure generating means is kept low, and the movement of the rotating body is accelerated at the same acceleration as when the turning radius is large. Directional control valve for pressure control circuit.

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