JP5122906B2 - Load-sensing hydraulic control system for construction machinery - Google Patents

Description

  The present invention relates to a hydraulic control device for a construction machine such as a hydraulic excavator, and more particularly to a hydraulic control for a construction machine in which supply of pressure oil to a boom cylinder is given priority over other hydraulic actuators among hydraulic actuators of the construction machine. Relates to the device.

  In a construction machine such as a hydraulic excavator, since the boom is heavy, generally, a large hydraulic pressure is required for a boom-up operation. Therefore, when other hydraulic actuators are operated simultaneously during a boom up operation on the boom cylinder and the load pressure is relatively small, the pressure oil from the pump is given priority over the hydraulic actuator, and the boom is raised. In other cases, the required amount of pressure oil is not supplied to the boom cylinder.

  The construction machine includes various hydraulic actuators for operating operations such as buckets, booms, and arms, or for traveling, and these hydraulic actuators are each supplied via a directional switching valve, preferably a variable displacement pump. It is comprised so that it may drive with the pressure oil from.

  By the way, in such a hydraulic work circuit, when the total required hydraulic oil amount of each hydraulic actuator exceeds the discharge capacity of the hydraulic pump, the oil amount is not distributed well to each hydraulic actuator, so-called hydraulic actuators The combined operability is reduced. As a method for solving such a problem, as shown in FIG. 4 (corresponding to FIG. 10 of Patent Document 1), the supply of pressure oil from the variable displacement pump 100 to the two actuators 102 and 104 is switched in each direction. This is done via valves 106 and 108. Here, auxiliary valves 110 and 112 are provided between the pump 100 and the directional control valves 106 and 108, respectively. With respect to these auxiliary valves, a part of one end portions 110a and 112a thereof is particularly provided. In addition, the pressure in the actuator supply oil passage of each direction switching valve is applied in the auxiliary valve opening direction, and part of the local end portions 110b and 112b are particularly in the pressure in each actuator supply oil passage. The maximum pressure is applied in the auxiliary valve closing direction. Therefore, according to such a circuit, when the actuators 102 and 104 are simultaneously operated, the opening degree of the auxiliary valve with respect to the low load side actuator is limited, so that the combined operability of the actuator is improved.

  However, in the above-described prior art, since the auxiliary valve is disposed between each switching valve and the pump, the supply line from the pump to the low-pressure side actuator is connected to the return of the direction switching valve during the combined operation of the actuator. Regardless of the opening, it is limited by the auxiliary valve. For this reason, when such an auxiliary valve is applied to an actuator such as a hydraulic excavator that requires meter-out control, supply of pressure oil is insufficient with respect to the movement of the actuator, cavitation occurs, Problems with noise and component reliability often occur. In this case, if the maximum opening on the meter-out side of the direction switching valve is limited in order to prevent the cavitation, the speed is reduced when the actuator is operated alone, resulting in a problem of workability.

  Further, in this type of hydraulic work circuit, for example, when the ambient temperature is lowered and the viscosity of the hydraulic oil is increased, or when the pump is driven by the engine and the rotational speed of the engine is reduced, the discharge flow rate of the pump is decreased. However, in the above-mentioned prior art, it is impossible to adjust the decrease in the discharge flow rate of the pump, that is, the fluctuation in the pump flow rate characteristic. Inconveniences such as a decrease (fluctuation) in the driving speed of the hydraulic actuator corresponding to the operation amount cannot be avoided (Patent Document 1).

  As a solution to such inconvenience, as shown in FIG. 5 (corresponding to FIG. 2 of Patent Document 1), in a hydraulic work circuit such as a hydraulic excavator having a plurality of hydraulic actuators, a composite at the time of simultaneous operation of the hydraulic actuators. A hydraulic work circuit having a relatively simple configuration that can improve the operability and prevent the occurrence of cavitation and further adjust the flow rate characteristics of the pump as required is disclosed.

  That is, when the merging valve 40 shown in the center part of FIG. 5 is arranged and the pressure oil supply to the arm cylinder 14-6 of the right hydraulic work circuit 10b is insufficient, the merging valve 40 and the connection line 54 are used. When pressure oil is supplied from the hydraulic work circuit 10a on the left side and the hydraulic oil supply to the boom cylinder 14-2 and bucket cylinder 14-1 of the hydraulic actuator is insufficient, the pump discharge line connected to the right pump 12b The pressure oil from the right hydraulic work circuit 10b is supplied to the pump discharge line 20a through the connection line 54 and the junction valve 40 from 20b.

Patent No. 3066050

  However, in the said patent document 1, as FIG. 5 shows, the boom cylinder 14-2 and the bucket cylinder 14-1 are connected in parallel from the same pump discharge line 20a, Therefore, these are operated simultaneously. In this case, generally, pressure oil is supplied with priority to the bucket side where the load pressure is lower than that of the boom, and there is a problem that the operation of the boom is not performed according to the operation command of the operator.

  As a result of intensive studies in view of the above-described points, the present inventors have performed a boom-up operation on the pressure oil supply to at least one other hydraulic actuator in order to give priority to the pressure oil supply to the boom cylinder over other hydraulic actuators. It has been found that the above-mentioned difficulties can be basically solved by suppressing sometimes.

  Accordingly, an object of the present invention is to provide a load sensing type hydraulic control device for a construction machine in which the supply of pressure oil to the boom cylinder has priority over other hydraulic actuators among the hydraulic actuators of the construction machine. .

  In order to achieve the above object, a load sensing type hydraulic control device for a construction machine according to the present invention is provided via a switching valve for each hydraulic actuator of a boom cylinder, an arm cylinder, a bucket cylinder, a left and right traveling hydraulic motor, and a swing hydraulic motor. In a load sensing type hydraulic control device for a construction machine that supplies pressure oil from a common pump discharge line and has a compensation valve on the meter-out side, a connection port to the boom cylinder switching valve is connected to the pump discharge line. Further, on the pump discharge line connecting the boom cylinder switching valve and another hydraulic actuator switching valve, when the boom cylinder switching valve is operated in the boom raising direction, at least one other Provided with suppression means for suppressing pressure oil supply to the switching valve for the hydraulic actuator And wherein the door.

  In that case, the suppression means can be composed of a variable throttle valve that acts in a direction to throttle the pump discharge line.

  In this case, two variable throttle valves are provided, and each variable throttle valve is connected to the boom cylinder switching valve with an arm and a bucket cylinder switching valve downstream of one variable throttle valve. The left and right traveling hydraulic motor switching valves and the swing motor switching valve can be connected and arranged downstream of the other variable throttle valve.

  In this case, an arm and bucket cylinder switching valve is disposed downstream of the one variable throttle valve, a swing hydraulic motor switching valve is disposed downstream of the other variable throttle valve, and further between the two variable throttle valves. The switching valve for the boom cylinder and the left and right traveling hydraulic motors can be connected and arranged.

  Furthermore, the opening degree of the variable throttle valve can be increased by the maximum load pressure of the hydraulic actuator located downstream of the variable throttle valve.

  Furthermore, the maximum load pressure of the switching valve located downstream of the one variable throttle valve can be detected, and the detected pressure can be applied to the other variable throttle valve in the throttle direction. .

According to the first aspect of the present invention, pressure oil is supplied from a common pump discharge line via the switching valves for hydraulic actuators of the boom cylinder, arm cylinder, bucket cylinder, left and right traveling hydraulic motor, and swing hydraulic motor. In the load sensing type hydraulic control device of the construction machine that supplies and has a compensation valve on the meter-out side, a connection port to the boom cylinder switching valve is connected to the pump discharge line. On the pump discharge line connecting the switching valve and another hydraulic actuator switching valve, when the boom cylinder switching valve is operated in the boom raising direction, at least one of the other hydraulic actuator switching valves is connected. Since it is configured with suppression means to suppress the pressure oil supply,
Since the hydraulic oil is supplied to the boom cylinder in preference to other simultaneously operated hydraulic actuators during the boom up operation, the boom drive can be performed more faithfully to the operator's operation command during the boom up operation. Therefore, it is possible to eliminate a sense of incongruity in the operation of the operator.

  According to the second aspect of the present invention, since the suppressing means is constituted by a variable throttle valve that acts in the direction of restricting the pump discharge line, the suppressing means can be realized by a relatively simple hydraulic circuit element. .

  According to the third aspect of the present invention, two variable throttle valves are provided, and each variable throttle valve is downstream of one variable throttle valve with respect to the connection port with the boom cylinder switching valve. The switching valve for the arm and bucket cylinder is connected and arranged, and the switching valve for the left and right traveling hydraulic motors and the switching valve for the swing motor are connected and arranged downstream of the other variable throttle valve. The supply of pressure oil to the boom cylinder can be prioritized for all hydraulic actuators.

According to the fourth aspect of the present invention, two variable throttle valves are provided, the arm and bucket cylinder switching valve are provided downstream of the one variable throttle valve, and the downstream of the other variable throttle valve. Since the switching valve for the swing hydraulic motor and the switching valve for the boom cylinder and the left and right traveling hydraulic motors are connected between the two variable throttle valves, the boom up operation and the simultaneous operation can be performed. The supply of pressure oil to the boom cylinder can be prioritized for hydraulic actuators other than the left and right traveling hydraulic motors, which are rarely performed.

  According to the fifth aspect of the present invention, since the opening of the variable throttle valve is caused to act by the maximum load pressure of the hydraulic actuator located downstream of the variable throttle valve, the variable throttle The degree of throttle of the valve can be relaxed by the maximum load pressure of the hydraulic actuator located downstream, and the pressure oil supply to the hydraulic actuator can be increased accordingly.

  According to the present invention as set forth in claim 6, the maximum load pressure of the switching valve located downstream of the one variable throttle valve is detected, and the detected pressure is throttled against the other variable throttle valve. Since there is no boom up operation command, the pressure oil supply to the switching valve located downstream of the one variable throttle valve is switched to the downstream of the other variable throttle valve. Prioritizing the supply of pressure oil to the valve can be selected according to the load pressure of each switching valve located downstream.

  Hereinafter, examples based on the embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3 of the accompanying drawings.

  FIG. 1 shows a schematic configuration of an entire hydraulic excavator as a typical construction machine to which the present invention is applied. In FIG. 1, an excavator SHV has an upper swinging body 12 mounted on a lower traveling body DRV driven by a hydraulic motor via a swinging mechanism RM. The upper swing body 12 is provided with a cab 14 at one front side portion thereof, and a boom 16 is attached to the front center portion so as to be able to be raised and lowered. An arm 20 is attached to the tip of the boom 16 so as to be rotatable up and down, and a bucket 24 is attached to the tip of the arm 20. Reference numeral BCY is a hydraulic cylinder for driving the boom, 18 is a hydraulic cylinder for driving the arm, and 22 is a hydraulic cylinder for driving the bucket. As is clear from FIG. 1, when the boom 16 is operated from the horizontal posture, the load pressure on the boom cylinder BCY becomes very large.

  FIG. 2 is a hydraulic circuit diagram for explaining a hydraulic control apparatus according to the present invention. In FIG. 2, reference numeral 30 is a variable displacement pump, which is rotationally driven by a motor (not shown). The discharge flow rate of the variable displacement pump 30 supplied to the discharge line L1 is determined by the tilt angle of the swash plate 30a. The tilt angle of the swash plate 30a is controlled via the flow rate adjusting mechanism 32 by a load sensing signal LS given from the line L3.

  Variable throttle valves 34 and 36 are arranged at each end of the discharge line L1 as shown in the figure. Reference numeral c is a connection port with a switching valve 46 for supplying and discharging pressure oil to and from the boom cylinder BYC, and communicates with a pressure oil supply port P of the boom switching valve 46. Reference numeral 54 is a compensation valve, the inlet side of which is connected to the tank port T of the switching valve 46, and the outlet side of which is connected to the tank line L2. The supply and discharge of the pressure oil to and from the boom cylinder BYC is performed by the pipe line PL via the ports PA and PB of the switching valve 46.

  Reference numeral 60 is a check valve provided on a line Ld for detecting the load pressure of the boom cylinder BYC. The line L4 is connected to the load pressure detection line Ld, and check valves 56 and 58 are arranged in opposite directions at both ends thereof to select the maximum load pressure of the hydraulic control device. That is, the pressure on the left side line L4a of the check valve 56, the pressure on the right side line L4b of the check valve 58, and the highest pressure among the pressures on the line L4 are loaded through the connection port d. A sensing signal pressure is applied to the line L3.

  The compensation valve 54 arranged on the meter-out side with respect to the boom cylinder BYC is supplied with a load pressure detection signal from the lower pressure oil signal receiving portion via the line L6, whereby the return flow rate to the tank line L2. Further, the maximum load pressure from the connection port d is given from the upper pressure oil signal receiving portion, and thereby the return flow rate to the tank line L2 is reduced.

  On the left side of the switching valve 46 for the boom cylinder BYC, an arm switching valve 44, a bucket switching valve 42, and optional switching valves 38, 40 are arranged corresponding to the range of the line L4a. Has been. Further, on the right side of the switching valve 46 for the boom cylinder BYC, switching valves 48 and 50 for left and right traveling and a switching valve 52 for turning are arranged corresponding to the range of the line L4b. . Each of these switching valves is provided with a compensation valve and a check valve for detecting load pressure, as in the case of the boom switching valve 46. (Each switch valve and compensation valve are shown in a simplified manner)

  The variable throttle valve 34 is disposed on the downstream side of the connection port c on the discharge line L1, and the upper pressure receiving portion R1 includes the pressure of the line L4a, that is, an arm, a bucket hydraulic cylinder (not shown), and The highest load pressure among the load pressures of the optional hydraulic actuator is given from the line L7. The lower pressure receiving portion R2 is given the pressure of the line L4b, that is, the highest load pressure among the load pressures of the left and right traveling hydraulic motors and the swing hydraulic motor (not shown) from the line L5.

  The pressure of the line L4a given from the line L7 via the pressure receiving portion R1 acts to increase the flow rate of pressure oil to the discharge line L1a on the downstream side (left side in the figure) from the connection port c. The pressure of the line L4b given from the line L5 via the pressure receiving portion R2 acts to reduce the flow rate of pressure oil to the discharge line L1a downstream from the connection port c.

  Reference sign BUP is an operation pressure signal given when the operator at the driver's seat performs a boom-up operation (not shown), and is given to the switching valve 46 and the variable throttle valves 34 and 36 via the line L8.

  The operation pressure signal BUP given to the compensation valve 34 via the line L8 acts to reduce the pressure oil flow rate to the discharge line L1a downstream from the connection port c. Further, the operation pressure signal BUP given to the variable throttle valve 36 via the line L8 acts to throttle the pressure oil flow rate to the line L1b on the downstream side of the line L1, that is, the turning switching valve 52.

  The left and right traveling switching valves 48 and 50 connected to the discharge line L1 are arranged in the same manner with respect to the boom switching valve 46 and the pressure oil supply. This is due to the fact that the left and right traveling operation and the boom-up operation are rarely commanded at the same time, and the required pressure oil amount and pressure of the left and right traveling hydraulic motors are relatively small compared to the boom-up operation.

In the hydraulic control apparatus according to the present invention configured as shown in FIG. 2, for example, a boom up operation with respect to the boom cylinder BYC, the bucket cylinder 22 and / or the arm cylinder 18.
Are simultaneously operated, the signal pressure BUP is supplied to the variable throttle valve 34 via the line L8 in response to the boom-up operation, so that the flow rate of pressure oil from the discharge line L1 to the discharge line L1a is reduced, and the bucket cylinder 22 In addition, since the pressure oil supply to the arm cylinder 18 is suppressed, the pressure oil supply to the boom cylinder BYC is ensured to a necessary and sufficient level. That is, the boom-up operation is prioritized in the pressure oil supply.

  In that case, the higher load pressure of the bucket cylinder 22 and / or the arm cylinder 18 is applied to the pressure receiving portion R1 via the line L7, and acts to relieve the restriction of the variable throttle valve 34. The pressure oil supply to is never stopped.

Further, when the boom up operation for the boom cylinder BYC and the swing hydraulic motor are simultaneously operated, the signal pressure BUP is supplied to the variable throttle valve 36, so that the flow rate of pressure oil from the discharge line L1 to the discharge line L1b is reduced. Since the pressure oil supply to the swing hydraulic motor via the switching valve 52 is suppressed, the pressure oil supply to the boom cylinder BYC is ensured to a necessary and sufficient level also in this case. That is, priority is given to the boom-up operation.

  Furthermore, when the bucket cylinder 22 and / or the arm cylinder 18 and the swing hydraulic motor are operated simultaneously, the swing hydraulic motor load pressure on the line L4b is transmitted via the line L5 (regardless of the boom up operation). Since the pressure is applied to the pressure receiving portion R2, when the load pressure of the line L5 is higher than the load pressure of the bucket cylinder 22 and / or the arm cylinder 18 of the line L7, the supply of pressure oil to the discharge line L1a is throttled by the variable throttle valve 34. The pressure oil supply to the swing hydraulic motor is prioritized over the bucket cylinder 22 and / or the arm cylinder 18.

  In FIG. 3, the arrangement of the variable throttle valve 36 of FIG. 2 is arranged as a variable throttle valve 36a between the switching valves 46 and 48, and further, the line L4b is connected to the pressure receiving portion R3 of the variable throttle valve 36a via the line L5. This is an example of a hydraulic control apparatus that applies the load pressure of the line L4a to the pressure receiving part R4 via the line L7. In this example, the left and right switching valves 48 and 50 are connected to the discharge line L1b on the downstream side of the variable throttle valve 36a.

  In FIG. 3, when the boom-up signal pressure BUP is applied, the priority of the pressure oil supply during the simultaneous operation is secured by the variable throttle valves 34 and 36a for all the other hydraulic actuators. . In FIG. 3, a high load pressure in the detected load pressure by the switching valves 48, 50, 52 on the right side of the boom switching valve 46 is applied to the pressure receiving portion R3 and to the pressure receiving portion R2 via the line L5. A high load pressure in the detected load pressure by the switching valves 38, 40, 42, 44 on the left side of the switching valve 46 is applied to the pressure receiving portion R1 and to the pressure receiving portion R4 via the line L7.

  Therefore, even when the boom-up operation is not performed, when the switching valve 48, 50, 52 on the right side and the switching valve 38, 40, 42, 44 on the left side are operated simultaneously, the load pressure detection line L4a In this manner, priority is given to the supply of pressure oil to the hydraulic actuator having the higher load pressure by restricting the variable throttle valve 34 or 36a having the lower pressure on L4b.

  Although the preferred embodiments of the present invention have been described with reference to FIGS. 2 and 3, those skilled in the art can make various modifications based on these examples. For example, an electromagnetic flow control valve is used in place of the variable throttle valve to control the flow rate with an electrical signal corresponding to the signal pressure BUP, and pressure receiving portions R1, R2, R3, and R4 are provided in FIGS. The case where there is no can be mentioned.

It is a figure showing the schematic structure of the whole typical hydraulic excavator as a construction machine to which the present invention is applied. It is a hydraulic circuit diagram for demonstrating the hydraulic control apparatus by this invention. FIG. 3 is a hydraulic circuit diagram when the arrangement of the variable throttle valve in FIG. 2 is changed. It is a conventional hydraulic work circuit diagram. It is another conventional hydraulic work circuit diagram.

Explanation of symbols

12 Upper swivel base 14 Cab 16 Boom 18 Arm cylinder 20 Arm 22 Bucket cylinder 24 Bucket 30 Variable capacity pump 30a Swash plate 32 Flow rate adjusting mechanisms 34, 36 Variable throttle valves 38, 40, 42, 44, 46, 48, 50, 52 Switching valve 54 Compensation valve 56, 58, 60 Check valve BCY Boom cylinder BUP Boom-up operation signal pressure c, d Connection port DRV Undercarriage RM Swivel platform SHV Hydraulic excavators L1, L1a, L1b Discharge line L2 Tank line L3 Load sensing Lines L4, L5, L6, L7, L8, Ld Lines L4a, L4b Load pressure detection lines R1, R2, R3, R4

Claims (4)

Construction machinery that supplies pressure oil from a common pump discharge line via a switching valve for each hydraulic actuator of the boom cylinder, arm cylinder, bucket cylinder, left and right traveling hydraulic motor, and swing hydraulic motor, and has a compensation valve on the meter-out side In the load sensing type hydraulic control device,
A connection port to the boom cylinder switching valve is connected to the pump discharge line, and further, on the pump discharge line connecting the boom cylinder switching valve and another hydraulic actuator switching valve, A suppression means for suppressing pressure oil supply to at least one of the other hydraulic actuator switching valves when the boom cylinder switching valve is operated in the boom raising direction ;
The suppression means is a variable throttle valve that acts in a direction to throttle the pump discharge line,
Two variable throttle valves are provided, and each variable throttle valve has an arm and a bucket cylinder switching valve connected to a connection port with the boom cylinder switching valve downstream of one variable throttle valve, and the other A load sensing type hydraulic control device for a construction machine, wherein a switching valve for a left and right traveling hydraulic motor and a switching valve for a swing motor are connected and arranged downstream of the variable throttle valve . Construction machinery that supplies pressure oil from a common pump discharge line via a switching valve for each hydraulic actuator of the boom cylinder, arm cylinder, bucket cylinder, left and right traveling hydraulic motor, and swing hydraulic motor, and has a compensation valve on the meter-out side In the load sensing type hydraulic control device,
A connection port to the boom cylinder switching valve is connected to the pump discharge line, and further, on the pump discharge line connecting the boom cylinder switching valve and another hydraulic actuator switching valve, A suppression means for suppressing pressure oil supply to at least one of the other hydraulic actuator switching valves when the boom cylinder switching valve is operated in the boom raising direction;
The suppression means is a variable throttle valve that acts in a direction to throttle the pump discharge line,
Two variable throttle valves are provided, an arm and bucket cylinder switching valve downstream of one variable throttle valve, a swing hydraulic motor switching valve downstream of the other variable throttle valve, and the two variable throttle valves construction machinery of the load sensing hydraulic control system you characterized by being configured to connect placement boom cylinder and the left, the switching valve for a right traveling hydraulic motor between the throttle valve. The load sensing type hydraulic pressure for a construction machine according to claim 1 or 2, wherein the hydraulic actuator is operated in a direction to increase an opening degree of the variable throttle valve by a maximum load pressure of a hydraulic actuator located downstream of the variable throttle valve. Control device. The maximum load pressure of the switching valve located downstream of the one variable throttle valve is detected, and the detected pressure is applied to the other variable throttle valve in the throttle direction. Item 4. A load-sensing hydraulic control device for a construction machine according to Item 3 .

Images