JP2781031B2 - Hydraulic circuit device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a hydraulic circuit device for a construction machine such as a hydraulic shovel or the like, and more particularly, to a hydraulic circuit device with a pressure compensation comprising a directional control valve and a pressure compensation valve. Hydraulic circuit device.

[Conventional technology]

FIG. 6 shows a conventional hydraulic circuit device using a flow control valve with pressure compensation. FIG. 6 shows a hydraulic circuit device used for turning the hydraulic excavator and driving the boom. A directional switching valve 4 is provided between the hydraulic pump 1 and the turning motor 10 and between the hydraulic pump 1 and the boom cylinder 11. , 5 and pressure compensating valves 6, 7 are provided. Operating devices 12 and 13 are provided for the direction switching valves 4 and 5, respectively.
When the operation lever 14 is operated, the pressure of the proportional pressure reducing valve 14a or 14b increases in proportion to the operation amount, and the spool of the direction switching valve 4 is moved according to the operation amount. Further, the pressure difference between the front and rear of the direction switching valve 4 is guided to the pressure compensating valve 6, and the pressure difference between the front and rear is controlled so as to be balanced with the spring 6a. For this reason, the flow rate flowing through the direction switching valve 4 is controlled so as to correspond to the opening area determined by the above-mentioned amount of movement of the spool, that is, the operation amount of the operation lever 14.

In addition, the discharge amount of the hydraulic pump 1 is controlled by the pump control device 18 of the load sensing control method so that the pump discharge pressure becomes higher than the maximum load pressure by a certain value.

[Problems to be solved by the invention]

In such a hydraulic circuit device, when the operation lever 50 is operated to drive the turning of the hydraulic excavator, the flow control valve 8 with pressure compensation attempts to secure a flow rate proportional to the operation amount. However, since the turning has a large inertia, the turning motor
10 cannot quickly reach the speed corresponding to the flow rate, the pressure of the circuit rises to the set pressure of the relief valve 55 or 56, and the excess oil escapes through the relief valve 55 or 56.

For this reason, regardless of the operation amount of the operation lever,
At the time of driving, the relief pressure which is the maximum pressure of the circuit becomes the driving pressure and is rapidly accelerated.

In addition, the flow escaping from the relief valve 55 or 56 does not drive the actuator, resulting in a useless flow and energy loss.

Further, the hydraulic pump 1 is load-sensing controlled and its discharge amount is limited. Therefore, when performing a combined operation of turning and other actuators, the hydraulic pump 1 is driven by another actuator by an unnecessary flow rate generated by the turning motor 10. Since the flow rate for driving 11 is insufficient, the work cycle time is slowed, and the work efficiency is deteriorated.

An object of the present invention is to provide a hydraulic circuit device that enables acceleration control of an actuator in accordance with an operation amount of an operation lever, minimizes energy loss, and enables efficient combined operation.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a directional switching valve between a hydraulic pump and each of a plurality of actuators for controlling a flow rate and a flow direction of pressure oil in accordance with an operation amount of an operation means, A pressure compensating flow control valve comprising a pressure compensating valve for controlling a pressure difference before and after the switching valve is provided, and a circuit pressure between at least one of the direction switching and an actuator corresponding thereto is supplied to a circuit pressure on a high pressure side. In a hydraulic circuit device provided with a pressure control valve for controlling a pressure below a set pressure, a first control means for controlling a setting input of the pressure control valve according to the operation amount, and a low pressure circuit for controlling a flow escaping from the pressure control valve. And a second control means for controlling the compensation differential pressure of the pressure compensating valve in accordance with the flow rate detected by the flow rate detection means.

Here, preferably, the first control means is maximum when the operation amount is smaller than a predetermined value near zero,
The set pressure is controlled so that the operation amount becomes minimum at the predetermined value, and increases when the operation amount becomes higher than the predetermined value, in proportion to the increase in the operation amount.

[Action]

In the present invention configured as described above, by providing the first control means for controlling the set pressure of the pressure control valve according to the operation amount, the set pressure of the pressure control valve decreases when the operation amount is small. The actuator is driven at a small acceleration corresponding to the low set pressure. When the operation amount increases, the set pressure increases correspondingly, and the drive acceleration of the actuator also increases.

On the other hand, at this time, by further providing the second control means for controlling the compensation differential pressure of the pressure compensating valve in accordance with the flow rate escaping from the pressure control valve, when the flow rate increases, the pressure compensating valve causes the front-rear difference of the direction switching valve to increase. Since the pressure is controlled to decrease, the flow rate through the directional control valve decreases. For this reason,
At the same time as the flow rate escaping from the pressure control valve is reduced, the discharge flow rate of the hydraulic pump that can be used by another actuator is increased, and the work cycle time of the actuator is shortened during combined operation with another actuator, thereby improving work efficiency.

〔Example〕

One embodiment of the present invention will be described with reference to FIG. The present embodiment is an example in which the present invention is applied to turning of a hydraulic shovel and driving of a boom.

In FIG. 1, reference numeral 1 denotes a variable displacement hydraulic pump whose displacement is controlled by a displacement displacement mechanism, that is, a swash plate 2. Hydraulic oil discharged from the hydraulic pump 1 passes from the discharge line 3 through flow control valves 8 and 9 with pressure compensation composed of directional switching valves 4 and 5 and pressure compensating valves 6 and 7, respectively, and a hydraulic motor as a load. These are supplied to 10, 11 to drive these.

An operation device 12 is provided for the direction switching valve 4. When the operation lever 14 is operated, the operation device 12 increases the pressure of the proportional pressure reducing valve 14a or 14b in proportion to the amount of operation of the operation lever 14. The spool 4 is moved according to the operation amount. Further, the pressure difference between the front and rear of the direction switching valve 4 is guided to the pressure compensating valve 6, and the pressure difference between the front and rear is controlled so as to be balanced with the spring 6a. For this reason,
The flow rate flowing through the direction switching valve 4 is controlled so as to correspond to the opening area determined by the above-described amount of movement of the spool, that is, the amount of operation of the operation lever 14.

The directional control valve 5 is also provided with an operating device 13 comprising an operating lever 15 and proportional pressure reducing valves 15a and 15b, and the pressure compensating valve 7 is provided with a spring 7A for controlling the pressure difference between the front and rear of the directional control valve 5. Have been. Reference numeral 16 denotes a pilot pump that supplies pilot pressure to the proportional valve pressure valves 14a, 14b, 15a, and 15b.

The load pressure of the swing motor 10 and the boom cylinder 11 is guided to the shuttle valve 17, and the high pressure side of both is selected as the maximum load pressure PLmax. The hydraulic pump 1 is guided to the pump control device 18 of the hydraulic pump load sensing control system, and the hydraulic pump 1 is controlled by the control device 18 so that the discharge amount of the hydraulic pump 1 is controlled so that the pump discharge pressure Ps becomes higher than the maximum load pressure PLmax by a constant value.

A pilot relief valve 22 is provided in circuits 20, 21 between the directional control valve 4 and the swing motor 10, and the pilot relief valve 22 measures the pressure on the high pressure side of the circuits 20, 21 via a check valve 23 or 24. The flow introduced and escaping from the low pressure side of the pilot relief valve 22 is returned to the low pressure side of the circuits 20, 21 via the check valve 25 or 26.

The pilot relief valve 22 is loaded with the hydraulic pressure on the high pressure side of the proportional pressure reducing valve 14a or 14b operated by the operation lever 14 via the shuttle valve 27 and the pilot line 27A, and the pilot relief valve 22 The set pressure is configured to increase. That is, the set pressure of the pilot relief valve 22 increases in proportion to the operation amount of the operation lever 14.

A throttle 28 is provided in a flow path between the pilot relief valve 22 and the check valves 25 and 26. Therefore, this diaphragm 28
Upstream increases in accordance with the flow rate passing through the pilot relief valve 22. A spring 6a of the pressure compensating valve 6 is provided between the pilot relief valve 22 and the throttle 28 through a pilot line 29.
The pressure obtained by the throttle 28 acts on the pressure compensating valve 6 via the pilot line 29 as an urging force in the direction of shutting off the circuit.

The circuits 20, 21 between the direction switching valve 4 and the swing motor 10 are also provided with the same relief valves 55, 56 as those in the related art, and further, prevent the swing motor 10 from running off on a downhill slope and rotating backward on an uphill slope. A counterbalance valve 57 for prevention is provided.

Next, the operation of this embodiment configured as described above will be described.

When the operation lever 14 for turning is operated and the operation amount is small, the output pressure of the proportional pressure reducing valve 14a or 14b is small, and thus the set pressure of the pilot relief valve 22 is low. The valve 22 is driven at a low set pressure. That is, the swing motor 10 is driven with a small acceleration and a small torque according to the set pressure.

On the other hand, at this time, the pressure immediately before the throttle 28 increases due to the flow rate discharged from the pilot relief valve 22, and the pressure is urged to the pressure compensating valve 6 via the pilot line 29. The differential pressure is controlled to decrease by the urging force. For this reason, regardless of the operation amount of the operation lever 14, the pressure difference between the front and rear of the direction switching valve 23 becomes small, the passing flow rate decreases, and the passing flow rate of the pilot relief valve 22 also decreases. As a result, the flow rate that can be used on the circuit side of the boom cylinder 11 increases, and when the capacity of the hydraulic pump 1 reaches the maximum during the combined operation of turning and boom, the required amount of pressure oil is also supplied to the boom cylinder 11 It is possible to prevent the work cycle time from being delayed.

When the operation amount of the turning operation lever 14 is large, the output pressure of the proportional pressure reducing valve 14a or 14b is also large and the set pressure of the pilot relief valve 22 is high, so that the turning motor 10 operates at the high set pressure of the pilot relief valve 22. It is driven with a large acceleration, that is, a large torque. At this time, the pressure immediately before the throttle 28 rises due to the flow rate discharged from the pilot relief valve 22, but since the discharge flow rate is small, the rise amount of the pressure is small, and the differential pressure across the directional control valve 4 is reduced by the spring 6a. It is controlled to a normal value close to the set value. For this reason, the operating lever
A desired flow rate according to the manipulated variable 14 can be supplied to the swing motor 10.

As described above, according to the present embodiment, the acceleration of the actuator and the motor torque of the swing motor 10 can be controlled in accordance with the operation amount of the operation lever 14, and when the operation amount of the operation lever is small, the pilot relief valve
It is possible to reduce the amount of flow that wastefully escapes from 22, reduce the energy loss, and use excess pressurized oil in the swivel system for the boom cylinder 11, so that the work cycle time of the combined operation can be prevented from becoming slow, and work efficiency can be reduced. Can be improved.

Another embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is realized by electric control.

In FIG. 2, the operation device 40 has an electric operation lever 41, and the operation lever 41 has displacement sensors 41a, 41a according to the operation amount.
The voltage is generated from b. Displacement sensor 41
a, 41b are sent to a controller 42, and the controller 42 generates an electromagnetic proportional valve so that the pressure shown in FIG. 3 is generated according to the voltage, that is, the operation amount of the operation lever 41.
Output command signal to 43 or 44. In FIG. 3, X
Ro and XLo are boundary values that define the dead zone of the operation amount, and XRm, X
Lm is the pressure Pa, Pb of the proportional solenoid valves 43, 44 (in FIG. 2, for convenience,
Command values Pa and Pb are added to the command signal). In the range where XR and XL exceed XRo and XLo and XRm and XLm, the pressures Pa and Pb are proportional to the amount of operation. And the pressures Pa and Pb gradually increase to the maximum values in order to reliably press the spool of the directional control valve 4 to the maximum position with the operation amounts XRm and XLm. The position of the spool of the direction switching valve 4 is determined in accordance with this pressure, and the flow rate is controlled in combination with the pressure compensating valve 6.

An electromagnetic proportional valve 45 is connected to the pilot relief valve 22. The controller 42 simultaneously operates the electromagnetic proportional valve 45 so that the pressure shown in FIG.
Outputs a command signal to 45. That is, when the manipulated variables XR and XL are in the range from XLp to XRp including the manipulated variable 0, the electromagnetic proportional valve 45
The pressure PR (in FIG. 2, the command signal is denoted by PR for convenience) becomes the maximum pressure, the minimum pressure becomes XLp and XRp, and the pressure PR becomes proportional to the operation amount increases from XLp and XRp. Control to ascend.

By controlling the pressure PR in this manner, when the manipulated variable is between XLp and XRp, that is, when the directional control valve 4 is in the neutral position, the set pressure of the pilot relief valve 22 is maintained at the maximum pressure. When parking on a slope,
It is possible to prevent the turning from rotating due to the pressure from the load side. Further, with an operation amount of XRp or XLp or more, the circuits 20 and 21 can be controlled at a set pressure corresponding to the operation amount,
Achieve the intended purpose. Here, in general, XLp and XRp are set to values smaller than the operation amounts XLo and XRo for operating the directional control valve 4, so that the swing motor 10 moves independently of the operation amount by driving from the load side at the start of operation. Can be prevented.

Further, a flow meter 46 is arranged downstream of the pilot relief valve 22, and an output signal of the flow meter 46 is taken into the controller 42. The controller 42 outputs a command signal to the electromagnetic proportional valve 47 so that the pressure shown in FIG. 6 is generated according to the signal, that is, the flow rate QR escaping from the pilot relief valve 22. That is, when the flow rate QR exceeds QRo, control is performed so that the pressure Pp of the electromagnetic proportional valve 47 (in FIG. 2, the command signal is indicated by Pp for convenience) increases in proportion to the increase in the flow rate. The electromagnetic proportional valve 47 is connected to the pressure compensating valve 6,
When the pressure Pp of the electromagnetic proportional valve 47 rises, it acts to cancel the force of the spring 6a, so that the differential pressure across the directional control valve 4 decreases, and the flow rate passing through the directional control valve 4 decreases. That is, the pilot pressure of the pressure compensating valve 6 is controlled by the electromagnetic proportional valve 47 so that the flow rate of the directional control valve 4 decreases as the flow rate of the pilot relief valve 22 increases. For this reason, as the flow rate escaping from the pilot relief valve 22 increases, the flow rate flowing to the swing motor 10 is reduced, the escape of useless flow rate is reduced, and a flow rate that can flow to the boom cylinder 11 (see FIG. 1) can be secured.

As described above, according to this embodiment, the same effect as that of the first embodiment can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the acceleration of the actuator can be controlled in accordance with the operation amount of the operation means, and when the operation amount is small, the amount of wastefully escaping from the pressure control valve can be reduced, and the energy loss can be reduced. In addition, since excess pressure oil in the actuator can be used for other actuators, it is possible to prevent a work cycle time of the combined operation from being delayed, and to improve work efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a hydraulic circuit device according to one embodiment of the present invention, and FIG. 2 is a diagram showing an overall configuration of a hydraulic circuit device according to another embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the manipulated variable and the pressure of the electromagnetic proportional valve given to the directional switching valve, and FIG. 4 is a diagram showing the relationship between the manipulated variable and the pressure of the solenoid proportional valve given to the pilot relief valve. FIG. 5 is a diagram showing the relationship between the flow rate escaping from the pilot relief valve and the pressure of the electromagnetic proportional valve applied to the pressure compensating valve, and FIG. 6 is a diagram showing a conventional hydraulic circuit device. Explanation of reference numerals 1 ... Hydraulic pump 4,5 ... Direction switching valve 6,7 ... Pressure compensation valve 8,9 ... Flow control valve with pressure compensation 10,11 ... Actuator 22 ... Pilot relief valve (pressure control) Valve) 12,13; 40 Operating means 20,21 Circuit 27 Shuttle valve (First control means) 27A Pilot line (First control means) 28 Throttle (Flow rate detecting means) 29 Pilot line (second control means) 42 Controller (first and second control means) 45 Electromagnetic proportional valve (first control means) 46 Flow meter (flow detection means) 47 ... Electromagnetic proportional valve (second control means)

Claims (2)

(57) [Claims] 1. A directional control valve between a hydraulic pump and each of a plurality of actuators for controlling a flow rate and a flow direction of pressure oil in accordance with an operation amount of an operation means, and a pressure before and after the directional control valve. A pressure compensating flow rate control valve comprising a pressure compensating valve for controlling a difference is provided, and a circuit between at least one of said directional switching valves and a corresponding actuator is controlled to a circuit pressure on a high pressure side to a set pressure or less. In a hydraulic circuit device provided with a pressure control valve, a first control unit that controls a set pressure of the pressure control valve according to the operation amount; and a flow path that returns a flow escaping from the pressure control valve to the low pressure circuit. A hydraulic circuit device comprising: a flow rate detecting means disposed; and a second control means for controlling a compensation differential pressure of the pressure compensating valve according to a flow rate detected by the flow rate detecting means. 2. The hydraulic circuit device according to claim 1, wherein said first control means is maximum when said operation amount is smaller than a predetermined value near zero, and said first control means is a predetermined value of said operation amount. And the set pressure is controlled so as to increase in proportion to an increase in the operation amount when the operation amount becomes higher than the predetermined value.