JP4136892B2 - Hydraulic control circuit for construction machinery - Google Patents

Description

  The present invention is a hydraulic control circuit for driving a plurality of hydraulic actuators including a pair of traveling actuators provided in a construction machine, and in particular, from a single operation of the traveling actuator to another actuator for traveling. The present invention relates to a hydraulic control circuit for a construction machine provided with means for preventing a rapid decrease in traveling speed accompanying a decrease in the flow rate of pressure oil supplied from a hydraulic pump to a traveling actuator during transition to a combined operation.

  A conventional hydraulic control circuit for a construction machine includes a first hydraulic circuit having a first hydraulic pump and a first directional control valve group connected to the first hydraulic pump, and a second hydraulic pump; A second hydraulic circuit having a second directional control valve group connected to the second hydraulic pump is provided.

  The first directional control valve group sends the flow of pressure oil from the first hydraulic pump to each of the swing motor, arm cylinder, boom cylinder, spare actuator, and first travel motor (one of a pair of travel actuators). It comprises a turning direction switching valve, a first arm direction switching valve, a boom first direction switching valve, a spare direction switching valve, and a first traveling direction switching valve to be controlled. These direction switching valves are the first hydraulic pump in the order of the turning direction switching valve, the arm first direction switching valve, the boom first direction switching valve, the spare direction switching valve, and the first traveling direction switching valve. Are connected in tandem from upstream to downstream of the discharge pipe. That is, in the first hydraulic circuit, the pressure oil is preferentially supplied to the other direction switching valve than the first traveling direction switching valve.

  The second direction switching valve group controls the flow of pressure oil from the second hydraulic pump to each of the second travel motor (the other of the pair of travel actuators), the boom cylinder, the bucket cylinder, and the arm cylinder. It consists of a traveling direction switching valve, a boom second direction switching valve, a bucket direction switching valve, and an arm second direction switching valve. These directional switching valves are arranged in the order of the second traveling directional switching valve, the boom second directional switching valve, the bucket directional switching valve, and the arm second directional switching valve, upstream of the discharge line of the second hydraulic pump. It is connected to the tandem downstream. That is, in the second hydraulic circuit, pressure oil is preferentially supplied to the second travel direction switching valve over the other direction switching valves.

  In addition, a branch pipe that connects the first hydraulic pump and the first travel motor is provided upstream of the turning direction switching valve in the first hydraulic circuit, and the branch pipe includes the branch pipe. A flow rate control valve is provided to vary the flow rate at. On the other hand, upstream of the second travel direction switching valve in the second hydraulic circuit, a branch pipe connecting the first travel direction switching valve and the second hydraulic pump in the first hydraulic circuit, and this branch pipe An opening / closing valve is provided for opening / closing.

  The on-off valve is maintained in a closed position when a direction switching valve other than the first and second traveling direction switching valves is not operating, and a direction switching valve other than the first and second traveling direction switching valves is provided. When operating, it is switched to the open position. That is, when the construction machine travels alone, the branch pipe is closed by the on-off valve, whereby the total discharge flow rate of the first hydraulic pump is transferred to the first travel motor via the first travel direction switching valve. The total discharge flow rate of the second hydraulic pump is supplied to the right travel motor via the second travel direction switching valve. In the combined operation of the first travel motor and the arm cylinder, boom cylinder, etc., the branch pipe is opened by the on-off valve, and a part of the discharge flow rate of the second hydraulic pump is in the first travel direction. It is distributed to the first travel motor via a switching valve.

In addition, when the direction switching valve other than the first and second traveling direction switching valves is operated, the flow rate control valve continuously changes from the open position where the throttle amount is minimum to the closed position where the branch pipe is blocked. It is designed to switch. That is, when shifting to the combined operation of the first travel motor and the arm cylinder, the boom cylinder, etc., the flow rate of the pressure oil supplied from the first hydraulic pump to the first travel motor is rapidly increased by the operation of the flow control valve. A decrease, that is, a rapid decrease in travel speed is prevented.
Japanese Patent Application Laid-Open No. 5-287775

  In the hydraulic control circuit of the conventional construction machine described above, the branch pipe and the flow control valve are provided in the discharge pipe of the first hydraulic pump. That is, the branch pipe and the flow control valve are designed to withstand high pressure and are expensive equipment. For this reason, when these branch pipes and flow control valves are retrofitted to a construction machine that is not equipped with branch pipes and flow control valves, there is a problem that the cost for subsequent installation is too high.

  The present invention has been made in consideration of the above-mentioned circumstances, and the purpose thereof is to be able to configure a function for preventing a rapid decrease in traveling speed at the time of transition from a traveling single operation to a combined operation including traveling at low cost. It is to provide a hydraulic control circuit for a construction machine.

In order to achieve the above object, the present invention provides a hydraulic control circuit for driving a plurality of actuators including a pair of first and second travel actuators by a first hydraulic pump and a second hydraulic pump, A first traveling direction switching valve that controls the flow of pressure oil to one traveling actuator, and a first direction switching valve that controls the flow of pressure oil to an actuator different from the first and second traveling actuators. And the first directional control valve is more preferentially supplied to the first directional switching valve than the first directional switching valve. A first hydraulic circuit connected upstream to the first hydraulic pump, wherein the first traveling directional control valve and the first directional switching valve are connected in parallel to the first hydraulic pump;
A second traveling direction switching valve that controls the flow of pressure oil to the second traveling actuator; and a second direction switching valve that controls the flow of pressure oil to the other actuator; The second traveling directional switching valve is upstream of the second directional switching valve to the second hydraulic pump so that pressure oil is supplied to the second traveling directional switching valve preferentially over the switching valve. A second hydraulic circuit connected to the second hydraulic circuit, a branch line branched from the discharge line of the second hydraulic pump, and the branch line connecting the second hydraulic pump and the input port of the first travel direction switching valve; In a hydraulic control circuit for a construction machine, which is provided in a pipeline and includes an on-off valve that opens the branch pipeline when the first directional switching valve is operated, the first directional switching valve reciprocates a pilot pressure. 1st pressure receiving part and 2nd pressure receiving part received from the direction to do Has, when the first travel directional control valve is actuated, the actuation delay means for delaying the operation of the first directional control valve provided, the actuation delay means, said first travel directional control valve Detection means for detecting the operation, and the second pressure receiving portion connected to the first pressure receiving portion of the first direction switching valve, wherein the detection means detects the operation of the first traveling direction switching valve. And a flow rate control valve set so as to delay the rate of pressure decrease in the first pressure-receiving portion when a pilot pressure for instructing a predetermined operation of the another actuator is applied .

  In the present invention configured as described above, when the first direction switching valve is not operating, that is, when another actuator is not operating, the on-off valve is held in the closed position. Therefore, when the first traveling actuator and the second traveling actuator are operated and the construction machine is traveling alone, the total flow rate of the pressure oil discharged from the first hydraulic pump is the first traveling direction switching valve. Is supplied to the first travel actuator, and the entire flow rate of the pressure oil discharged from the second hydraulic pump is supplied to the second travel actuator via the second travel direction switching valve.

  In addition, when the first directional switching valve is operated in order to perform a combined operation of the first traveling actuator and another actuator while the first traveling actuator is operating by the operation of the first traveling directional switching valve. The on-off valve is switched to the open position. Thereby, a part of the pressure oil discharged from the second hydraulic pump is distributed to the first travel actuator via the first travel direction switching valve.

When the first travel directional control valve is operating, the operation of the first travel directional control valve is detected by the detecting means, the flow control valve is actuated. In this state, when a pilot pressure that instructs a predetermined operation of another actuator is applied to the second pressure receiving portion of the first directional switching valve, the rate of pressure decrease in the first pressure receiving portion of the first directional switching valve is controlled by the flow control. Delayed by a valve. As a result, the operation of the first directional control valve is delayed, the rate of increase in the flow rate of the pressure oil distributed from the first hydraulic pump to another actuator is delayed, and at the same time supplied from the first hydraulic pump to the first travel actuator. The rate of decrease in the flow rate of the pressurized oil is also slowed. As a result, it is possible to prevent a sudden decrease in the traveling speed when the traveling single operation including the first traveling actuator is shifted to the combined operation of the traveling including the operation of the first traveling actuator and the operation of another actuator. , Shock associated with a decrease in travel speed can be alleviated.

  In the present invention, the operation delay means controls the operation of the first direction switching valve, and does not control the high pressure oil. Therefore, it is possible to prevent a rapid decrease in the traveling speed at the time of transition from the traveling single operation including the operation of the first traveling actuator to the combined operation of the traveling including the operation of the first traveling actuator and the operation of another actuator. The function can be configured with inexpensive equipment rather than expensive equipment designed to withstand high pressures.

The present invention is also a hydraulic control circuit for driving a plurality of actuators including a pair of first and second travel actuators by a first hydraulic pump and a second hydraulic pump, wherein the pressure applied to the first travel actuator is A first traveling direction switching valve that controls the flow of oil, and a first direction switching valve that controls the flow of pressure oil to an actuator different from the first and second traveling actuators, The first hydraulic pump is located upstream of the first traveling direction switching valve so that the pressure oil is supplied to the first direction switching valve preferentially over the traveling direction switching valve. A first hydraulic circuit in which the first traveling direction switching valve and the first direction switching valve are connected in parallel to the first hydraulic pump, and pressure oil to the second traveling actuator. Control the flow A directional control valve for two travels and a second directional control valve for controlling the flow of pressure oil to the other actuator, and the second directional control valve has priority over the second directional control valve. A second hydraulic circuit in which the second traveling direction switching valve is connected to the second hydraulic pump upstream of the second direction switching valve so as to be supplied with pressure oil; and a discharge of the second hydraulic pump A branch pipe branching from the pipe and connecting the second hydraulic pump and the input port of the first travel direction switching valve; provided in the branch pipe and when the first direction switching valve is operated In addition, in a hydraulic control circuit for a construction machine including an opening / closing valve for opening the branch pipe, the first direction switching valve has a first pressure receiving portion and a second pressure receiving portion that receive the pilot pressure from opposite directions. and, when the first travel directional control valve is in operation The actuation delay means for delaying the operation of the first directional control valve provided, the actuation delay means, detecting means for detecting the operation of said first traveling directional control valve, the second of said first directional control valve A pilot pressure is applied to the second pressure receiving portion to instruct a predetermined operation of the other actuator in a state where the operation of the first traveling direction switching valve is detected by the detecting means connected to the pressure receiving portion. Occasionally, characterized in that it comprises a flow control valve which is set to delay the rate of increase in the pressure in the second pressure receiving portion.

In the present invention configured as described above, when the operation of the first travel direction switching valve is detected by the detecting means, the flow control valve is operated. In this state, when the pilot pressure is applied to the second pressure receiving portion of the first directional control valve, the rising speed of the pressure in the second pressure receiving portion is delayed by the flow rate control valve. As a result, the operation of the first directional control valve is delayed, the rate of increase in the flow rate of the pressure oil distributed from the first hydraulic pump to another actuator is delayed, and at the same time supplied from the first hydraulic pump to the first travel actuator. The rate of decrease in the flow rate of the pressurized oil is also slowed. As a result, when the traveling single operation including the operation of the first traveling actuator is shifted to the combined operation of the traveling including the operation of the first traveling actuator and the operation of another actuator, the traveling speed is rapidly decreased. Can be prevented.

  Further, the present invention is characterized in that the another actuator includes an arm cylinder, and the predetermined operation is an arm cloud.

  In the present invention configured as described above, the traveling speed is reduced at the time of transition from the traveling single operation including the operation of the first traveling actuator to the combined operation of the traveling including the operation of the first traveling actuator and the arm cloud. Can be prevented. That is, when the traveling single operation including the operation of the first traveling actuator is shifted to the combined operation of the traveling including the operation of the first traveling actuator and the arm cloud, the decrease in the traveling speed becomes particularly large. In the invention, it is possible to prevent a rapid decrease in the traveling speed at this time.

  As described above, according to the present invention, since the operation delay means controls the operation of the first direction switching valve, the operation delay means is not an expensive equipment designed to withstand high pressure, and is inexpensive. It can be configured with various equipment. As a result, it is possible to retrofit at a low cost a function for preventing a rapid decrease in the traveling speed at the time of transition from the traveling single operation to the combined operation including traveling.

  An embodiment of a hydraulic control circuit for a construction machine according to the present invention will be described below with reference to FIG.

  FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic control circuit for a construction machine according to the present invention.

  The present embodiment is provided in a construction machine, for example, a hydraulic excavator, and, as shown in FIG. 1, a plurality of actuators are provided by pressure oil discharged from a first hydraulic pump 41 and a second hydraulic pump 61 driven by an engine 5. For example, a hydraulic control circuit for driving a pair of travel actuators, that is, the first and second travel motors 1 and 2, the arm cylinder 3, and the boom cylinder 4. The hydraulic excavator is provided with a bucket cylinder and a swing motor, and a hydraulic circuit for driving the bucket cylinder and the swing motor. However, in this embodiment, it is omitted for the sake of simplicity. is there.

  The first hydraulic pump 41 is a variable displacement hydraulic pump including a swash plate 41a that tilts to change the displacement volume. A pump regulator 23 is attached to the first hydraulic pump 41. The pump regulator 23 includes a servo actuator 23a that adjusts the tilt angle of the swash plate 41a, and a control valve 23b that controls the pressure supplied from the pilot pump 6 to the servo actuator 23a. Similarly, the second hydraulic pump 61 is a variable displacement hydraulic pump including a swash plate 61 that tilts to change the displacement volume. A pump regulator 24 is attached to the second hydraulic pump 61. The pump regulator 24 includes a servo actuator 24a that adjusts the tilt angle of the swash plate 61a, and a control valve 24b that controls the pressure supplied from the pilot pump 6 to the servo actuator 24a.

  In addition, this embodiment includes a plurality of open center type directional control valves that control the flow rate of the pressure oil supplied to each of the first travel motor 1, the second travel motor 2, the arm cylinder 3, and the boom cylinder 4. Yes. In other words, the first travel motor 1 is connected to the first travel direction switching valve 45, the second travel motor 2 is connected to the second travel direction switching valve 65, and the arm cylinder 3 is the first arm travel direction valve. The direction switching valve 43 and the arm second direction switching valve 63 are connected, and the boom cylinder 4 is connected to the boom first direction switching valve 44 and the boom second direction switching valve 64.

  Further, in the present embodiment, the first traveling direction switching valve 45, the actuator different from the first and second traveling motors 1 and 2, that is, the arm first direction switching valve 43, and the boom first direction switching. A first hydraulic circuit 40 is provided in which a first directional switching valve group including a valve 44 is connected to a first hydraulic pump 41. In the first hydraulic circuit 40, the arm first direction switching valve 43, the boom first direction switching valve 44, and the first traveling direction switching valve 45 are arranged in this order in the discharge line 42 of the first hydraulic pump 41. Is connected in tandem from upstream to downstream. That is, the pressure oil discharged from the first hydraulic pump 41 is preferentially supplied to the arm first direction switching valve 43 and the boom first direction switching valve 44 rather than the first traveling direction switching valve 45. It is.

  In the first hydraulic circuit 40, the arm first direction switching valve 43, the boom first direction switching valve 44, and the first traveling direction switching valve 45 are parallel to the first hydraulic pump 41. Connected. That is, each of the direction switching valves 43 to 45 includes a parallel pipe 46 branched from the discharge pipe 42 upstream of the arm first direction switching valve 43 and pipes 47 to 49 branched from the parallel pipe 46. To the first hydraulic pump 41. That is, the pressure oil discharged from the first hydraulic pump 41 is distributed to the arm first direction switching valve 43, the boom first direction switching valve 44, and the first traveling direction switching valve 45. .

  In the present embodiment, a second direction switching valve group including the second traveling direction switching valve 63, the arm second direction switching valve 64, and the boom second direction switching valve 65 is connected to the second hydraulic pump 61. The second hydraulic circuit 60 is provided. In the second hydraulic circuit 60, the second traveling direction switching valve 63, the arm second direction switching valve 64, and the boom second direction switching valve 65 are arranged in this order in the discharge line 62 of the second hydraulic pump 61. Is connected in tandem from upstream to downstream. That is, the pressure oil discharged from the second hydraulic pump 61 is preferentially supplied to the second traveling direction switching valve 63 rather than the second boom direction switching valve 64 and the arm second direction switching valve 65. It is.

  Further, in the second hydraulic circuit 60, between the second traveling direction switching valve 63 and the boom second direction switching valve 64, and between the boom second direction switching valve 64 and the arm second direction switching valve 65. Are connected by a pipe 66.

  In the present embodiment, the discharge conduit 62 of the second hydraulic pump 61 is provided with a branch conduit 80 that connects the second hydraulic pump 61 and the input port of the first travel direction switching valve 45. The branch pipe 80 is provided with an open / close valve 81. The on-off valve 81 receives a pilot pressure selected by a shuttle valve 18 described later and switches from the closed position to the open position.

  Further, the present embodiment includes a first traveling operation device 10 for applying pilot pressures A and B to the pair of first and second pressure receiving portions 45 a and 45 b of the first traveling direction switching valve 45. Yes. The first travel operation device 10 includes a pair of pilot valves 10a and 10b operated by an operation lever 101. The pilot valve 10a generates the pilot pressure A from the pressure oil supplied from the pilot pump 6 according to the operation of the operation lever. The pilot valve 10b generates the pilot pressure B from the pressure oil supplied from the pilot pump 6 in accordance with the operation of the operation lever 101.

  In the present embodiment, the pilot pressures C and D are applied to the pair of first and second pressure receiving portions 44c and 44d of the boom first direction switching valve 44, and the pair of first and second pressure switching portions 64 of the second direction switching valve 64 is applied. 1 and 2 includes a boom operation device 11 for applying pilot pressures C and D which are opposite to the second pressure receiving portions 64c and 64d. The boom operation device 11 includes a pair of pilot valves 11c and 11d operated by an operation lever 11l. The pilot valve 11c generates a pilot pressure C from the pressure oil supplied from the pilot pump 6 according to the operation of the operation lever 11l. The pilot valve 11d generates the pilot pressure D from the pressure oil supplied from the pilot pump 6 in accordance with the operation of the operation lever 11l.

  Further, in the present embodiment, the pilot pressures E and F are provided to the pair of first and second pressure receiving portions 43e and 43f of the arm first direction switching valve 43, and the pair of first and second pressure switching portions 65 of the second direction switching valve 65 are provided. 1 and 2 includes an arm operating device 12 for applying pilot pressures E and F opposite to the second pressure receiving portions 65e and 65f. The arm operating device 12 includes a pair of pilot valves 12e and 12f operated by an operating lever 121. The pilot valve 12e generates the pilot pressure E from the pressure oil supplied from the pilot pump 6 according to the operation of the operation lever 12l. The pilot valve 12f generates the pilot pressure F from the pressure oil supplied from the pilot pump 6 in accordance with the operation of the operation lever 121.

  Further, the present embodiment includes a second traveling operation device 13 for applying pilot pressures G and H which are opposite to the pair of first and second pressure receiving portions 63g and 63h of the second traveling direction switching valve 63. ing. The second traveling operation device 13 includes a pair of pilot valves 13g and 13h operated by an operation lever 13l. The pilot valve 13g generates the pilot pressure G from the pressure oil supplied from the pilot pump 6 in accordance with the operation of the operation lever 13l. The pilot valve 13h generates the pilot pressure H from the pressure oil supplied from the pilot pump 6 according to the operation of the operation lever 13l.

  Further, in the present embodiment, the shuttle valve 14 that selects the larger one of the pilot pressures A and B, the shuttle valve 15 that selects the larger one of the pilot pressures C and D, and the pilot pressures E and F A shuttle valve 16 for selecting the larger one and a shuttle valve 17 for selecting the larger one of the pilot pressures G and H are provided. Further, a shuttle valve 18 is provided for selecting the larger one of the pilot pressure selected by the shuttle valve 15 and the pilot pressure selected by the shuttle valve 16. Further, the pilot pressure selected by the shuttle valve 18 and the pilot pressure selected by the shuttle valve 14, whichever is greater, and the pilot pressure selected by the shuttle valve 18 and the shuttle valve 17 are selected. And a shuttle valve 21 for selecting the higher pilot pressure.

  The pilot pressure selected by the shuttle valve 18 acts on the pressure receiving portion of the on-off valve 81 as described above. The pilot pressure selected by the shuttle valve 20 acts on the pressure receiving portion of the control valve 23b provided in the pump regulator 23. The pilot pressure selected by the shuttle valve 21 acts on the pressure receiving portion of the control valve 24b provided in the pump regulator 24.

  In FIG. 1, reference numeral 7 denotes a main relief valve that regulates the maximum discharge pressure of the first hydraulic pump 41 and the second hydraulic pump 61. 8 is a pilot relief valve that regulates the maximum discharge pressure of the pilot pump. A hydraulic oil tank 9 stores hydraulic oil sucked up by the first hydraulic pump 41 and the second hydraulic pump 61 and collects return oil.

  In particular, in the present embodiment, when the first travel direction switching valve 40 is operating, an operation delay means for delaying the operation of the first direction switching valve, for example, the arm first direction switching valve 43 is provided.

  The operation delay means is detection means for detecting the operation of one of the first traveling direction switching valve 45 and the second traveling direction switching valve 63, that is, the shuttle valve 19 and the first traveling direction switching by the shuttle valve 19. A flow control valve, that is, a shockless valve 90, is set so that when the operation of the valve 45 is detected, the rate of pressure decrease in the pressure receiving portion 43e of the arm first direction switching valve 43 is delayed.

  The shuttle valve 19 selects the pilot pressure A or B output from the first travel operation device 10 and the pilot pressure G or H output from the second travel operation device 13 and selects a larger pilot pressure. The shockless valve 90 is acted upon. That is, the pilot pressure selected by the shuttle valve 19 causes the detection signal indicating that the operation of the first traveling direction switching valve 45 or the second traveling direction switching valve 63 is detected, and the shockless valve 90 to be detected. It functions as an activation signal to be activated.

The shockless valve 90 is located between the output port of the pilot valve 12e of the arm operating device 12 and the first pressure receiving portion 43e of the arm first direction switching valve 43, that is, the pilot pressure E (arm A dump signal) is provided in the arm dump signal passage 94 for supplying the first pressure receiving portion 43e of the arm first direction switching valve 43 to the first pressure receiving portion 43e. The shock-less valve 90 is provided with a pressure receiving portion 90c which receives the pilot pressure selected by the shuttle valve 19 receives the pilot pressure at the pressure receiving portion 90c, the open position 90 b to fully open the arm dumping signal path 94 From the first pressure receiving portion 43e, the return to the pilot valve 12e is switched to the throttle position 90a for squeezing the return oil.

  The shockless 90 includes a shockless mechanism that stably squeezes the return oil from the first pressure receiving portion 43e of the arm first direction switching valve 43 to the pilot valve 12e when switched to the throttle position 90a. Yes. The shockless mechanism section includes a check valve 91 that blocks the flow of return oil in the arm dump signal passage 94, a throttle section 93 that is provided in parallel with the check valve and throttles the return oil, and a return that passes through the throttle section 93. A pressure compensation valve 92 that adjusts the flow rate of the pressure oil supplied to the throttle portion 93 according to the differential pressure before and after the check valve 91 is provided so that the oil flow rate is stabilized.

  The present embodiment configured as described above operates as follows.

<Driving alone operation>
When the hydraulic excavator travels, for example, moves forward, the operation levers 101 and 13l of both the first travel operation device 10 and the second travel operation device 13 are tilted in a direction corresponding to the forward movement of the hydraulic excavator.

  At this time, in the first travel operating device 10, for example, the pilot valve 10a is operated by the operating lever 101, and the pilot pressure A is output from the pilot valve 10a. When the pilot pressure A acts on the first pressure receiving portion 45a of the first traveling direction switching valve 45, the first traveling direction switching valve 45 is switched from the neutral state shown in FIG. 1 to the left position. That is, the first travel direction switching valve 45 forms an oil passage for rotating the first travel motor 1 in the rotational direction corresponding to the forward movement of the hydraulic excavator between the discharge pipe 42 and the first travel motor 1. Then, the pressure oil from the first hydraulic pump 41 is guided to the first traveling motor 1 by this oil passage. Thereby, the 1st travel motor 1 rotates in the rotation direction corresponding to advance of a hydraulic excavator.

  The pilot pressure A acts on the first travel direction switching valve 45 as described above, while being guided to the shuttle valves 14 and 20 and acting on the control valve 23b of the pump regulator 23. Then, the control valve 23b is switched according to the magnitude of the pilot pressure A, the pressure acting on the servo actuator 23a from the pilot pump 6 is adjusted, and the servo actuator 23a is driven according to the adjusted pressure. Thereby, the tilt angle of the swash plate 41a of the first hydraulic pump 41 is adjusted to the tilt angle corresponding to the operation amount of the operation lever 10l. That is, the first hydraulic pump 41 discharges the pressure oil at a flow rate corresponding to the operation amount of the operation lever 10l.

  Similarly, in the second travel operation device 13, for example, the pilot valve 13h is operated by the operation lever 13l, and the pilot pressure H is output from the pilot valve 13h. When the pilot pressure H acts on the second pressure receiving portion 63h of the second traveling direction switching valve 63, the second traveling direction switching valve 63 is switched from the neutral state shown in FIG. In other words, the second travel direction switching valve 63 forms an oil passage between the discharge pipe 62 and the second travel motor 2 for rotating the second travel motor 2 in the rotational direction corresponding to the forward movement of the hydraulic excavator. Then, the pressure oil from the second hydraulic pump 61 is guided to the second traveling motor 2 by this oil passage. Thereby, the 2nd traveling motor 2 rotates in the rotation direction corresponding to advance of a hydraulic excavator.

  The pilot pressure H acts on the second travel direction switching valve 63 as described above, while being guided to the shuttle valves 17 and 21 and acting on the control valve 24 b of the pump regulator 24. Then, the control valve 24b is switched according to the magnitude of the pilot pressure H, the pressure acting on the servo actuator 24a from the pilot pump 6 is adjusted, and the servo actuator 24a is driven according to the abutted pressure. Thereby, the tilt angle of the swash plate 61a of the second hydraulic pump 61 is adjusted to the tilt angle corresponding to the operation amount of the operation lever 13l. That is, the second hydraulic pump 61 discharges the pressure oil at a flow rate corresponding to the operation amount of the operation lever 13l.

  In addition, for the purpose of traveling alone, only the first traveling operation device 10 and the second traveling operation device 13 are operated, and the boom operation device 11 and the arm operation device 12 are operated. Therefore, the pilot pressure C or D output by the boom operation device 11 and the pilot pressure E or F output by the arm operation device 12 are not performed. Accordingly, since the pilot pressure does not act on the on-off valve 81, the on-off valve 81 does not operate and is held in the closed position shown in FIG. 1, and is located between the second hydraulic pump 61 and the first travel direction switching valve 45. Is blocked. Thus, during the traveling single operation, the pressure oil is not distributed from the second hydraulic pump 61 to the first traveling direction switching valve 45, and the total flow rate of the pressure oil discharged from the second hydraulic pump 61 is the second. The total flow rate of the pressure oil supplied to the second travel motor 2 through the travel direction switching valve 63 and discharged from the first hydraulic pump 41 is transferred to the first travel motor 1 through the first travel direction switching valve 45. Supplied.

<At the time of transition from single driving operation to combined operation of arm cloud>
When the pilot valve 12f is operated by the operating lever 12l of the arm operating device 12 in the state where traveling is performed independently as described above, the pilot pressure F that instructs the arm cloud is output from the pilot valve 12f. The When the pilot pressure F acts on the second pressure receiving portion 43f of the arm first direction switching valve 43, the arm first direction switching valve 43 switches from the neutral state shown in FIG. 1 to the left position. In other words, an oil passage for extending the arm cylinder 3 is formed by the arm first direction switching valve 43 between the discharge pipe 42 and the arm cylinder 3, and the pressure from the first hydraulic pump 41 is formed by the oil passage. Oil is guided to the arm cylinder 3. As a result, the arm cylinder 3 extends and arm crowding is performed.

  The pilot pressure F acts on the arm first direction switching valve 43 as described above, while being guided to the shuttle valves 16 and 18 and acting on the on-off valve 81. Then, the on-off valve 81 is switched to the open position, and the branch pipe 80 is opened. As a result, the second hydraulic pump 61 and the first travel direction switching valve 45 communicate with each other, and the pressure oil discharged from the second hydraulic pump 61 is distributed to the second travel motor 2 and the first travel motor 1.

  Further, the pilot pressure F acts on each of the arm first direction switching valve 43 and the on-off valve 81 and is also led to each of the shuttle valves 20 and 21. The shuttle valve 20 selects the larger one of the pilot pressures A and F, and the shuttle valve 21 selects the larger one of the pilot pressures H and F.

  The pilot pressure selected by the shuttle valve 20 acts on the control valve 23 b of the pump regulator 23. Then, the control valve 23b is switched according to the magnitude of the pilot pressure, the pressure supplied from the pilot pump 6 to the servo actuator 23a is adjusted, and the servo actuator 23a is driven according to the adjusted pressure. Thus, the tilt angle of the swash plate 41a of the first hydraulic pump 41 is adjusted to a tilt angle corresponding to the operation amount of the operation lever 10l or 12l. That is, the first hydraulic pump 41 discharges the pressure oil at a flow rate corresponding to the operation amount of the operation lever 10l or 12l. Then, the pressure oil discharged from the first hydraulic pump 41 is distributed to the first traveling motor 1 and the arm cylinder 3 as described above.

  Similarly, the pilot pressure selected by the shuttle valve 21 acts on the control valve 24 b of the pump regulator 24. Then, the control valve 24b is switched according to the magnitude of the pilot pressure, the pressure supplied from the pilot pump 6 to the servo actuator 24a is adjusted, and the servo actuator 24a is driven according to the adjusted pressure. Accordingly, the tilt angle of the swash plate 61a of the second hydraulic pump 61 is adjusted to a tilt angle corresponding to the operation amount of the operation lever 13l or 12l. That is, the second hydraulic pump 61 discharges pressure oil at a flow rate corresponding to the operation amount of the operation lever 13l or 12l. The pressure oil discharged from the second hydraulic pump 61 is distributed to the first travel motor 1 and the second travel motor 2 as described above.

<Preventing sudden drop in running speed>
Particularly in the present embodiment, the shockless valve 90 is used when shifting from the traveling single operation including the operation of the first traveling motor 1 to the combined operation of the traveling including the operation of the first traveling motor 1 and the arm cloud as described above. As a result, a rapid decrease in travel speed is prevented.

  That is, as described above, the larger one of the pilot pressure A for operating the first travel direction switching valve 45 and the pilot pressure H for operating the second travel direction switching valve 63 is selected by the shuttle valve 19. , Acting on the pressure receiving portion 90c of the shockless valve 90. As a result, the shockless valve 90 switches from the open position 90b shown in FIG. 1 to the throttle position 90a, and the return oil of the pilot valve 12e can be throttled from the first pressure receiving portion 43e of the arm first direction switching valve 43. Retained.

  When the pilot pressure F for instructing the arm claid acts on the second pressure receiving portion 43f of the arm first direction switching valve 43 as described above with the shockless valve 90 thus operated, The return oil that returns from the pressure receiving portion 43e to the hydraulic oil tank via the pilot valve 12e is throttled by the shockless valve 90.

  That is, in the shockless valve 90, the flow of return oil in the arm dump signal passage 94 is restricted by the check valve 91, whereby the return oil is guided to the throttle portion 93 and throttled. At this time, the flow rate of the pressure oil supplied to the throttle portion 93 is adjusted by the pressure compensation valve 92 according to the differential pressure before and after the check valve 91, and thereby the return oil is stably throttled.

  When the return oil from the first pressure receiving portion 43e of the arm first direction switching valve 43 is throttled in this way, the pressure decreasing rate in the first pressure receiving portion 43e is slowed down, and the arm first direction switching valve 43 is reduced. Is delayed. As a result, the increase in the flow rate distributed from the first hydraulic pump 41 to the arm cylinder 3 via the arm first direction switching valve 43 is delayed, and at the same time, the first hydraulic pump 41 is supplied to the first travel motor 1. The rate of decrease in the flow rate of pressurized oil is also slowed down. As a result, it is possible to prevent a rapid decrease in the traveling speed when shifting from the traveling independent operation including the operation of the first traveling motor 1 to the traveling operation including the operation of the first traveling motor 1 and the combined operation of the arm cloud.

  According to this embodiment, the following effects can be obtained.

  In the present embodiment, the operation delay means, that is, the shuttle valve 19 and the shockless valve 90 are equipment provided in the pilot pressure signal passage and not expensive equipment designed to withstand high pressure, so that the construction is inexpensive. it can. As a result, it is possible to retrofit at a low cost a function for preventing a rapid decrease in the traveling speed at the time of transition from the traveling independent operation including the first traveling motor 1 to the traveling including the first traveling motor 1 and the combined operation of the arm cloud. .

  In the above-described embodiment, the shockless valve 90 as the operation delay means is provided in the arm dump signal passage 94 that guides the pilot pressure E to the first pressure receiving portion 43e of the first directional switching valve 43 for the arm. Thus, the return oil from the first pressure receiving portion 43e of the arm first direction switching valve 43 is throttled, but the present invention is not limited to this. That is, a shockless valve is provided in the arm cloud signal path that guides the pilot pressure F to the second pressure receiving portion 43f of the arm first direction switching valve 43, and the pilot pressure oil that acts on the second pressure receiving portion 43f by this shockless valve. You may make it squeeze.

  The shockless valve in this case includes, for example, a check valve for blocking the flow of pilot pressure oil from the pilot valve 12f to the second pressure receiving portion 43f in the arm cloud signal path, and a pilot pressure oil provided in parallel with the check valve. And a pressure compensation valve that adjusts the flow rate of the pilot pressure oil supplied to the throttle portion according to the differential pressure before and after the check valve so that the flow rate of the pilot pressure oil passing through the throttle portion is stabilized. I have.

  In the operation delay means including the shockless valve, the operation of the arm first direction switching valve 43 can be delayed by delaying the rate of pressure increase in the second pressure receiving portion 43f. As a result, similar to the above-described embodiment, the traveling speed at the time of transition from the traveling single operation including the operation of the first traveling motor 1 to the combined operation of the traveling including the operation of the first traveling motor 1 and the arm cloud is rapid. Decline can be prevented. Further, since this operation delay means is also provided in the signal path for guiding the pilot pressure, it can be constructed at low cost.

  Further, in the above-described embodiment, it is possible to prevent a rapid decrease in the traveling speed at the time of transition from the traveling single operation including the operation of the first traveling motor 1 to the combined operation of the traveling including the first traveling motor and the arm cloud. Was configured. This is because the traveling speed is greatly reduced especially when shifting from the traveling alone including the operation of the first traveling motor 1 to the combined operation of the traveling including the operation of the first traveling motor 1 and the arm cloud. Because it occurs. However, the present invention is not limited to this. In addition to the transition from the traveling single operation including the operation of the first traveling motor 1 to the combined operation of the traveling including the first traveling motor and the arm cloud, the first traveling is performed. You may make it the structure which prevents the rapid fall of the traveling speed at the time of transfer to combined operation | movement with each of driving | running | working including a motor and arm dumping, boom raising, and boom lowering.

It is a hydraulic circuit diagram showing one embodiment of the hydraulic control circuit of the construction machine of the present invention.

Explanation of symbols

1 First traveling motor (first traveling actuator)
2 Second traveling motor (second traveling actuator)
3 Arm cylinder (another actuator)
4 Boom cylinder 10 First traveling operation device 11 Boom operation device 12 Arm operation device 13 Second traveling operation device 19 Shuttle valve (operation delay means)
40 First Hydraulic Circuit 41 First Hydraulic Pump 42 Discharge Pipe 43 First Directional Switching Valve for Arm 44 First Directional Switching Valve for Boom 45 First Directional Switching Valve for Traveling 46 Parallel Pipeline 47 Pipeline 48 Pipeline 49 Pipe Path 60 second hydraulic circuit 61 second hydraulic pump 62 discharge pipe 63 second traveling direction switching valve 64 second direction switching valve for boom 65 second direction switching valve for arm 80 branch pipe 81 on-off valve 90 shockless valve (Operation delay means)
94 Arm dump signal passage

Claims (3)

A hydraulic control circuit for driving a plurality of actuators including a pair of first and second traveling actuators by a first hydraulic pump and a second hydraulic pump,
A first traveling direction switching valve that controls the flow of pressure oil to the first traveling actuator, and a first direction that controls the flow of pressure oil to an actuator different from the first and second traveling actuators. And the first directional control valve is supplied to the first directional control valve preferentially to the first directional switching valve rather than the first directional switching valve. A first hydraulic circuit connected to the first hydraulic pump upstream of the first hydraulic directional switching valve and the first directional switching valve connected in parallel to the first hydraulic pump;
A second traveling direction switching valve that controls the flow of pressure oil to the second traveling actuator; and a second direction switching valve that controls the flow of pressure oil to the other actuator; The second traveling directional switching valve is upstream of the second directional switching valve to the second hydraulic pump so that pressure oil is supplied to the second traveling directional switching valve preferentially over the switching valve. A connected second hydraulic circuit;
A branch line branched from the discharge line of the second hydraulic pump and connecting the second hydraulic pump and an input port of the first travel direction switching valve;
In a hydraulic control circuit for a construction machine provided with an opening / closing valve provided in the branch pipe and opening the branch pipe when the first direction switching valve is operated,
The first direction switching valve has a first pressure receiving portion and a second pressure receiving portion that receive pilot pressure from opposite directions,
An operation delay means is provided for delaying the operation of the first direction switching valve when the first travel direction switching valve is operating, and the operation delay means detects the operation of the first travel direction switching valve. And the second pressure receiving portion is connected to the first pressure receiving portion of the first direction switching valve, and the second pressure receiving portion is connected to the second pressure receiving portion in a state where the detection means detects the operation of the first traveling direction switching valve. A flow control valve set so as to delay the rate of pressure decrease in the first pressure receiving portion when a pilot pressure is given to instruct a predetermined operation of the actuator. Hydraulic control circuit for the machine. A hydraulic control circuit for driving a plurality of actuators including a pair of first and second traveling actuators by a first hydraulic pump and a second hydraulic pump,
A first traveling direction switching valve that controls the flow of pressure oil to the first traveling actuator, and a first direction that controls the flow of pressure oil to an actuator different from the first and second traveling actuators. And the first directional control valve is supplied to the first directional control valve preferentially to the first directional switching valve rather than the first directional switching valve. A first hydraulic circuit connected to the first hydraulic pump upstream of the first hydraulic directional switching valve and the first directional switching valve connected in parallel to the first hydraulic pump;
A second traveling direction switching valve that controls the flow of pressure oil to the second traveling actuator; and a second direction switching valve that controls the flow of pressure oil to the other actuator; The second traveling directional switching valve is upstream of the second directional switching valve to the second hydraulic pump so that pressure oil is supplied to the second traveling directional switching valve preferentially over the switching valve. A connected second hydraulic circuit;
A branch line branched from the discharge line of the second hydraulic pump and connecting the second hydraulic pump and an input port of the first travel direction switching valve;
In a hydraulic control circuit for a construction machine provided with an opening / closing valve provided in the branch pipe and opening the branch pipe when the first direction switching valve is operated,
The first direction switching valve has a first pressure receiving portion and a second pressure receiving portion that receive pilot pressure from opposite directions,
An operation delay means is provided for delaying the operation of the first direction switching valve when the first travel direction switching valve is operating, and the operation delay means detects the operation of the first travel direction switching valve. And the second pressure receiving portion is connected to the second pressure receiving portion of the first direction switching valve, and the second pressure receiving portion is connected to the second pressure receiving portion in a state where the detection means detects the operation of the first traveling direction switching valve. of when the pilot pressure for instructing a predetermined operation of the actuator is given, the construction equipment you anda flow control valve which is set to delay the rate of increase in the pressure in the second pressure receiving portion Hydraulic control circuit. The hydraulic control circuit for a construction machine according to claim 1 or 2, wherein the another actuator is an arm cylinder, and the predetermined operation is an arm cloud .

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