JP2015014345A - Hydraulic circuit of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine which can efficiently prevent the generation of cavitation without causing the lowering of a drive speed of an actuator.SOLUTION: A hydraulic circuit 1 comprises: a drive circuit 4 which drives a hydraulic motor 101 and a hydraulic cylinder 102 by using the hydraulic pressure of a lubricant supplied from a drive pump 3; a control device 7 which controls the supply of the lubricant to the drive circuit 4 by using a pilot pump 71; and a return conduit 5 which returns the lubricant discharged from the drive circuit 4 to an oil tank 2. A makeup circuit 6 for replenishing the lubricant to the drive circuit 4 is connected to the drive circuit 4 independently of the return conduit 5. The makeup circuit 6 comprises a makeup tank 68, and a back-pressure setting valve 64 which sets pressure in the makeup circuit 6 higher than pressure in the return conduit 5.

Description

  The present invention relates to a hydraulic circuit of a construction machine such as a hydraulic excavator.

  A construction machine such as a hydraulic excavator has a hydraulic circuit for driving an actuator such as a hydraulic motor that drives a revolving body and a front working unit such as a boom provided on the front side of the revolving body. It is used.

  This hydraulic circuit generally controls a drive circuit that drives an actuator using hydraulic pressure of hydraulic oil supplied from a drive pump, and controls supply of the hydraulic oil to the drive circuit using a pilot pump. A control device, and a return pipe for returning the hydraulic oil discharged from the drive circuit to an oil tank.

  The hydraulic circuit drives the actuator when hydraulic oil is supplied from the drive pump to the drive circuit, and stops when the control device cuts off the supply of hydraulic oil to the drive circuit.

  However, in this hydraulic circuit, the actuator cannot be stopped immediately even if the supply of hydraulic oil to the drive circuit is cut off due to the large inertial force of the revolving unit and the operating part of the front working unit.

  For example, in the case of a hydraulic motor that drives a swivel body, the hydraulic motor continues to rotate without supplying hydraulic oil until the hydraulic motor is completely stopped. become. Therefore, a phenomenon in which bubbles are generated from the hydraulic oil existing in the pipe line, that is, cavitation occurs, which causes noise and erosion.

  Also, in the case of a hydraulic cylinder that drives the front working part, if an operation with a large inertia such as when the boom is lowered or an operation that causes the load on the cylinder to reverse suddenly is performed, the pressure in the cylinder is negative. And cavitation occurs. As a result, if air bubbles are mixed in the hydraulic oil in the cylinder and the compressibility of the hydraulic oil is increased, the operability is adversely affected, such as a decrease in pressure response of the hydraulic cylinder, breathing, and rocking.

  Therefore, as a method for solving these problems, for example, a hydraulic circuit shown in Patent Document 1 has been proposed. In the hydraulic circuit of Patent Document 1, surplus oil from the pilot pump is merged with the return line, and the pressure in the return line is set to a certain level or more by the back pressure check valve.

  In such a hydraulic circuit, when the supply line to the actuator in the drive circuit becomes negative pressure, the hydraulic oil stored in the oil tank is passed through the return line and the makeup valve into the supply line. Introduced to eliminate negative pressure and prevent cavitation.

Japanese Patent No. 2765718

  However, in the case of a hydraulic motor that drives the swivel body, the amount of hydraulic oil supplied is large, so that the negative pressure generated in the supply pipe also increases. Therefore, in order to eliminate the negative pressure, it is necessary to introduce a large amount of hydraulic oil into the supply pipeline. Therefore, when using the hydraulic circuit of Patent Document 1, the pressure set in the return pipe must be set high. As a result, the driving speed of the actuator is reduced.

  The reason for this is that the upper limit is set for the pressure in the supply line of the drive circuit. Therefore, if a high pressure is applied in the return line, the pressure difference between the supply line and the discharge line of the drive circuit is small. Become. As a result, the amount of hydraulic oil supplied to the actuator decreases, and the driving speed of the actuator decreases. When the driving speed of the actuator is lowered, the operability is deteriorated particularly when the driving speed of the actuator is required, such as during full operation.

  Further, when a high pressure is applied in the return pipe line, the drive pump supplies the hydraulic oil under a high load. Therefore, even if the occurrence of cavitation can be prevented, the energy loss is increased and the fuel consumption is deteriorated, so that the efficiency is not good.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic circuit for a construction machine that can efficiently prevent the occurrence of cavitation without reducing the driving speed of an actuator.

  As a result of intensive studies, the present inventors have employed the following construction machine hydraulic circuit in order to solve the above problems.

The hydraulic circuit of the construction machine according to the present invention controls a drive circuit that drives an actuator using hydraulic pressure of hydraulic oil supplied from a drive pump, and controls the supply of the hydraulic oil to the drive circuit using a pilot pump. In a hydraulic circuit of a construction machine, comprising: a control device that performs control; and a return pipe that returns the hydraulic oil discharged from the drive circuit to an oil tank;
The drive circuit further includes a makeup circuit that replenishes the hydraulic oil, and the makeup circuit sets the hydraulic oil supply source and the pressure in the makeup circuit higher than the pressure in the return line. And a pressure control valve that is connected to the drive circuit separately from the return pipe.

  In the hydraulic circuit of the construction machine of the present invention, a make-up circuit for replenishing hydraulic fluid to the drive circuit is connected to the drive circuit separately from the return line, and the make-up circuit includes a supply source, a pressure control valve, Equipped with. As a result, when the supply line of the actuator of the drive circuit or the inside of the actuator becomes negative pressure, hydraulic oil is replenished from the makeup circuit to the drive circuit, and the negative pressure is eliminated.

  Moreover, since the hydraulic fluid is replenished to the drive circuit using the makeup circuit, it is not necessary to set the pressure in the return line high. Therefore, the drive pump does not supply hydraulic oil in a state where it receives a high load, and energy loss increases and fuel consumption does not deteriorate. Therefore, the hydraulic circuit of the construction machine of the present invention can efficiently prevent cavitation.

  In addition, since it is not necessary to set the pressure in the return line high, the pressure difference between the supply line and the discharge line of the drive circuit is not reduced, and a decrease in the supply flow rate to the actuator can be suppressed. Therefore, the hydraulic circuit of the construction machine according to the present invention does not cause a decrease in the driving speed of the actuator.

It is a figure which shows the hydraulic circuit of the hydraulic excavator of the 1st Embodiment of this invention. It is a figure which shows the hydraulic circuit of the hydraulic excavator of the 2nd Embodiment of this invention. It is a figure which shows the hydraulic circuit of the hydraulic shovel of the 3rd Embodiment of this invention. It is a figure which shows the hydraulic circuit of the hydraulic excavator of the 4th Embodiment of this invention. It is a figure which shows the hydraulic circuit of the hydraulic shovel of the 5th Embodiment of this invention. It is a figure which shows the hydraulic circuit of the hydraulic excavator of the 6th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a hydraulic circuit 1 according to a first embodiment of the present invention. The hydraulic circuit 1 includes a hydraulic motor 101 (swing motor) that drives a swinging body provided in a hydraulic excavator, and three hydraulic cylinders 102 that drive a front working unit such as a boom provided on the front side of the swinging body. Used to drive.

  The hydraulic circuit 1 includes an oil tank 2 in which hydraulic oil is stored, two drive pumps 3, a drive circuit 4 connected to the two drive pumps 3, a return line 5 connected to the drive circuit 4, and a make-up. An up circuit 6 and a control device 7 connected to one drive pump 3 are provided.

  The two drive pumps 3 supply hydraulic oil to the drive circuit 4. The two drive pumps 3 are connected to the oil tank 2 (not shown). The two drive pumps 3 are driven by the engine 100, thereby sucking up the hydraulic oil from the oil tank 2 and supplying the hydraulic oil to the drive circuit 4.

  The drive circuit 4 is a circuit that drives the hydraulic motor 101 and the hydraulic cylinder 102 using the hydraulic pressure of the hydraulic oil supplied from the two drive pumps 3. The drive circuit 4 includes four direction switching valves 42 each having a supply side connected to a discharge side of two drive pumps 3 via a supply circuit 41.

  A main relief valve 40 is connected to the supply circuit 41 between the two drive pumps 3 and the direction switching valve 42. The discharge side of the main relief valve 40 is connected to a main line 61 (described later) of the makeup circuit 6 through a discharge line 40a. The main relief valve 40 prevents the hydraulic oil from being discharged to the main pipeline 61 when the pressure in the supply circuit 41 becomes equal to or higher than a predetermined pressure, thereby preventing the pressure from exceeding the predetermined pressure.

  The four direction switching valves 42 are connected to the hydraulic motor 101 and the respective hydraulic cylinders 102 via a supply line 43 and a discharge line 44, respectively.

  The supply line 43 and the discharge line 44 connected to the hydraulic motor 101 are connected by two connection lines 45 and 46. The two connection pipes 45 and 46 are connected by a communication pipe 47.

  Make-up valves 60 a and 60 b provided in the connection line 45 supply hydraulic oil when the supply line 43 and the discharge line 44 become negative pressure via the communication line 47.

  Relief valves 48 and 49 provided in the other connection pipe 46 allow the hydraulic oil to flow out to the communication pipe 47 when the pressure in the supply pipe 43 or the discharge pipe 44 becomes a predetermined pressure or higher. This is to prevent the above.

  The return line 5 is a line that returns the hydraulic oil discharged from the drive circuit 4 to the oil tank 2. The upstream side of the return line 5 is connected to each direction switching valve 42 via a discharge line 51. The downstream end of the return pipe 5 is connected to the oil tank 2.

  The makeup circuit 6 is a circuit for supplying hydraulic fluid to the drive circuit 4. The makeup circuit 6 is connected to the drive circuit 4 separately from the return line 5. The makeup circuit 6 is configured around a main pipeline 61 connected to the oil tank 2.

  A cylinder supply line 62 is connected to the upstream side of the main line 61. Each cylinder supply line 62 is provided with a makeup valve 60, and the discharge side thereof is connected to the supply line 43 and the discharge line 44 of each hydraulic cylinder 102. Each makeup valve 60 supplies hydraulic oil when the supply line 43 or the discharge line 44 becomes negative pressure.

  Further, the upstream side of the main pipeline 61 is connected to a communication pipeline 47 on the hydraulic motor 101 side via a motor supply pipeline 63. The two makeup valves 60a, 60b on the hydraulic motor 101 side also constitute the makeup circuit 6 together with the makeup valve 60 on each hydraulic cylinder 102 side.

  A back pressure setting valve 64 (the pressure control valve of the present invention) is provided in a portion of the main pipeline 61 that is downstream of the connection portion with the motor supply pipeline 63 and close to the oil tank 2. The back pressure setting valve 64 sets the pressure in the makeup circuit 6 higher than the pressure in the return pipe 5. Both ends of the branch pipe 65 are connected to the upstream side and the downstream side across the back pressure setting valve 64. The branch pipe 65 is provided with a check valve 66.

  A hydraulic oil supply pipe 67 is connected to the upstream side of the main pipe 61 with respect to the upstream end of the branch pipe 65. A supply tank 68 (replenishment source of the present invention) for temporarily storing hydraulic oil is connected to the downstream end of the supply pipe 67.

  The control device 7 switches the flow path of each direction switching valve 42 and controls the supply of hydraulic oil to the drive circuit 4. The control device 7 includes a pilot pump 71 connected to one drive pump 3 and an operation signal control unit 73 connected to the pilot pump 71 via a pilot pipe line 72.

  The pilot pump 71 is connected to the oil tank 2 (not shown). The pilot pump 71 is driven by the engine 100, thereby sucking the hydraulic oil from the oil tank 2 and supplying the hydraulic oil to the operation signal control unit 73 via the pilot pipe line 72.

  The operation signal control unit 73 is connected to an operation unit (not shown) provided in the cab of the hydraulic excavator. The operation signal control unit 73 switches each direction switching valve 42 by the hydraulic oil supplied from the pilot pump 71 in accordance with the drive signal of the hydraulic motor 101 and each hydraulic cylinder 102 input from the operation unit. .

  The pilot line 72 is connected to the main line 61 of the makeup circuit 6 via a discharge line 74. A pilot relief valve 70 is provided in the discharge conduit 74. The pilot relief valve 70 prevents the hydraulic oil from being discharged to the main pipeline 61 when the pressure in the pilot pipeline 72 becomes equal to or higher than a predetermined pressure, thereby preventing the pressure from exceeding the predetermined pressure.

Further, the magnitude relation among the set pressures of the pilot relief valve 70, the back pressure setting valve 64 of the makeup circuit 6 and the check valve 66 is as follows.
Pilot relief valve 70> back pressure setting valve 64> check valve 66

  Next, the operation of the hydraulic circuit 1 in the hydraulic circuit 1 configured as described above will be described. When driven by the engine 100, the two drive pumps 3 suck up the hydraulic oil from the oil tank 2 and supply the hydraulic oil to each direction switching valve 42 via the supply circuit 41. Further, when driven by the engine 100, the pilot pump 71 sucks up the hydraulic oil from the oil tank 2 and supplies the hydraulic oil to the operation signal control unit 73 through the pilot pipe line 72.

  When the drive signal of the hydraulic motor 101 or each hydraulic cylinder 102 is not input to the operation signal control unit 73, the hydraulic oil supplied to each direction switching valve 42 is oil through the discharge pipe 51 and the return pipe 5. Returned to tank 2.

  Further, since the operating oil is not supplied from the operation signal control unit 73 to each direction switching valve 42, the operating oil in the pilot line 72 is discharged to the main line 61 of the makeup circuit 6 through the pilot relief valve 70. The

  Further, the hydraulic oil discharged from the main relief valve 40 is discharged to the main line 61 through the discharge line 40a.

  The hydraulic oil (surplus oil) discharged from the pilot relief valve 70 and the main relief valve 40 to the main pipeline 61 is stored in the supply tank 68 via the supply pipeline 67. When the hydraulic oil in the replenishing tank 68 is full and the pressure in the makeup circuit 6 reaches the pressure set by the back pressure setting valve 64, the hydraulic oil in the main line 61 is back pressure setting valve 64. Flows to the oil tank 2 via

  When a drive signal for the hydraulic motor 101 is input to the operation signal control unit 73, the operation signal control unit 73 opens the flow path of the direction switching valve 42. As a result, the direction switching valve 42 causes the hydraulic oil from the supply circuit 41 to flow to the supply line 43 to drive the hydraulic motor 101. The hydraulic oil discharged from the hydraulic motor 101 is returned to the oil tank 2 through the discharge pipe 44, the direction switching valve 42, the discharge pipe 51, and the return pipe 5.

  Next, when the input of the drive signal of the hydraulic motor 101 to the operation signal control unit 73 is stopped, the flow path of the direction switching valve 42 is closed. As a result, the hydraulic oil from the supply circuit 41 does not flow to the supply line 43 of the hydraulic motor 101.

  However, the hydraulic motor 101 continues to rotate by its own inertia force until it completely stops even when hydraulic oil does not flow through the supply pipeline 43, so the pressure in the discharge pipeline 44 becomes high. As a result, the hydraulic oil flows from the relief valve 48 (49) to the motor supply line 63 via the connection line 46 and the communication line 47.

At the same time, the hydraulic oil in the supply conduit 43 is continuously rotated by the hydraulic motor 101.
Since the oil is sucked into the hydraulic motor 101, the pressure in the supply pipe 43 becomes negative. Then, the hydraulic oil in the motor supply line 63 is supplied into the supply line 43 via the communication line 47, the connection line 45, and the makeup valve 60a (60b). Further, the hydraulic oil stored in the supply tank 68 is supplied into the supply line 43 via the motor supply line 63 and the makeup valve 60a (60b). Thereby, the negative pressure in the supply pipeline 43 is eliminated.

  Such hydraulic oil supply operation is performed in the same manner in the case of the hydraulic cylinder 102. This will be specifically described below.

  When a drive signal for the hydraulic cylinder 102 is input to the operation signal control unit 73, the operation signal control unit 73 opens the flow path of the direction switching valve 42. The direction switching valve 42 drives the hydraulic cylinder 102 by flowing hydraulic oil from the supply circuit 41 to the supply line 43. The hydraulic oil discharged from the hydraulic cylinder 102 is returned to the oil tank 2 through the discharge pipe 44, the direction switching valve 42, the discharge pipe 51, and the return pipe 5.

  If an operation with a large inertia such as when the boom is lowered during the operation of the hydraulic cylinder 102 or an operation in which the load applied to the hydraulic cylinder 102 is suddenly reversed, more hydraulic oil is discharged from the hydraulic cylinder 102 than usual. Thus, the pressure in the hydraulic cylinder 102 becomes negative. Then, the hydraulic oil in the cylinder supply line 62 is supplied into the hydraulic cylinder 102 from the supply line 43 and the discharge line 44 via the makeup valve 60. Thereby, the negative pressure in the hydraulic cylinder 102 is eliminated.

  Further, when the full operation is repeatedly performed in the turning operation and the boom raising / lowering operation, the amount of replenishment may be insufficient because the hydraulic oil is not sufficiently stored in the replenishment tank 68. In such a case, the negative pressure is eliminated by supplying hydraulic oil from the oil tank 2 to the drive circuit 4 via the check valve 66.

  As described above, in the hydraulic circuit 1 according to the present embodiment, the makeup circuit 6 for supplying hydraulic fluid to the drive circuit 4 is connected to the drive circuit 4 separately from the return line 5. Includes a replenishment tank 68 and a back pressure setting valve 64. As a result, when the supply circuit 43 to the hydraulic motor 101 or the inside of the hydraulic cylinder 102 becomes negative pressure in the drive circuit 4, the negative pressure is eliminated by supplying hydraulic oil from the makeup circuit 6 to the drive circuit 4. The

  Further, since the hydraulic fluid is replenished to the drive circuit 4 using the makeup circuit 6, it is not necessary to set the pressure in the return line 5 high. Therefore, the drive pump 3 does not supply hydraulic oil in a state of receiving a high load, and energy loss increases and fuel consumption is not deteriorated. Therefore, the hydraulic circuit 1 of the present embodiment can efficiently prevent the occurrence of cavitation.

  In addition, since it is not necessary to set the pressure in the return line 5 high, the pressure difference between the supply line 43 and the discharge line 44 of the drive circuit 4 is not reduced, and the pressure to the hydraulic motor 101 and each hydraulic cylinder 102 is not reduced. Reduction in supply flow rate is suppressed. Therefore, the hydraulic circuit 1 of the present embodiment does not cause a decrease in the driving speed of the hydraulic motor 101 or each hydraulic cylinder 102.

  Further, in the hydraulic circuit 1 of the present embodiment, since the surplus oil from the drive pump 3 and the pilot pump 71 is used as the hydraulic oil stored in the replenishing tank 68, energy can be used effectively, which is unnecessary. Energy loss can be reduced. The hydraulic oil stored in the replenishing tank 68 may be only the surplus oil from the pilot pump 71. Further, regardless of the supply tank 68, another supply source such as an accumulator may be used.

(Second Embodiment)
FIG. 2 is a diagram showing a hydraulic circuit 201 of a hydraulic excavator showing a second embodiment of the present invention. In the hydraulic circuit 201 of the present embodiment, the same reference numerals are given to the same parts as those of the hydraulic circuit 1 of the first embodiment, and different parts are mainly described.

  In the hydraulic circuit 201 of the present embodiment, a make-up circuit for supplying hydraulic oil to the drive circuit 4 supplies a motor make-up circuit 206 for supplying hydraulic oil to the hydraulic motor 101 and hydraulic oil to each hydraulic cylinder 102. The cylinder make-up circuit 216 is configured separately.

  The motor make-up circuit 206 is a make-up circuit according to the present invention. In the motor make-up circuit 206, the upstream end of the main line 261 connected to the oil tank 2 is connected to the motor supply line 63.

  In the cylinder makeup circuit 216, each cylinder supply line 62 is connected to the return line 5. The return line 5 is provided with a back pressure setting valve 264 that sets the pressure in the return line 5.

The magnitude relationship among the set pressures of the pilot relief valve 70, the back pressure setting valve 64 and check valve 66 of the motor make-up circuit 206, and the back pressure setting valve 264 of the return line 5 is as follows.
Pilot relief valve 70> back pressure setting valve 64> back pressure setting valve 264> check valve 66
That is, the pressure in the motor make-up circuit 206 is set higher than the pressure in the return line 5.

  In the hydraulic circuit 201 configured as described above, hydraulic oil is replenished into the hydraulic cylinder 102 by the cylinder make-up circuit 216 when the pressure in the hydraulic cylinder 102 becomes negative.

  Specifically, the hydraulic oil stored in the oil tank 2 passes through the return line 5, the cylinder supply lines 62 and 62, the make-up valves 60 and 60, the supply line 43 and the discharge line 44. Thus, the hydraulic cylinder 102 is replenished. Thereby, the negative pressure in the hydraulic cylinder 102 is eliminated.

  Further, the hydraulic oil discharged from the main relief valve 40 and the pilot relief valve 70 to the main pipeline 61 of the motor make-up circuit 206 is stored in the replenishment tank 68 via the supply pipeline 67.

  Therefore, when the pressure in the supply pipe 43 of the hydraulic motor 101 becomes negative, the hydraulic oil stored in the supply tank 68 is supplied to the supply pipe 67, the main pipe 261, the motor supply pipe 63, and the communication. The supply pipe 43 is replenished via the pipe 47, the connection pipe 45, and the makeup valve 60a (60b). Thereby, the negative pressure in the supply pipeline 43 is eliminated.

  Here, since the negative pressure generated in the supply line 43 of the hydraulic motor 101 becomes larger than the negative pressure generated in the hydraulic cylinder 102, a large amount of hydraulic oil is instantaneously applied to the supply line 43. Replenishment is required.

  Therefore, in the hydraulic circuit 201 of the present embodiment, the makeup circuit (motor makeup circuit 206) of the present invention is applied to the hydraulic motor 101. Therefore, the hydraulic oil stored in the supply tank 68 can be concentrated and supplied into the supply pipe 43. Therefore, the hydraulic circuit 201 of the present embodiment can prevent cavitation more efficiently.

  Further, in the hydraulic circuit 201 of the present embodiment, the hydraulic oil in the supply tank 68 is supplied only to the hydraulic motor 101. Therefore, the capacity of the replenishment tank 68 can be made smaller than that of the hydraulic circuit 1 of the first embodiment in which the hydraulic oil in the replenishment tank 68 is replenished to the hydraulic motor 101 and each hydraulic cylinder 102. , Space can be saved. The other effects are as described in the first embodiment.

(Third embodiment)
FIG. 3 is a diagram showing a hydraulic circuit 301 of a hydraulic excavator showing a third embodiment of the present invention. In the hydraulic circuit 301 of the present embodiment, the same reference numerals are given to the same parts as those of the hydraulic circuit 1 of the first embodiment, and different parts will be mainly described.

  In hydraulic circuit 301 of the present embodiment, makeup circuit 306 for supplying hydraulic fluid to drive circuit 4 includes two accumulators (first accumulator 311 and second accumulator 312) as hydraulic oil supply sources of the present invention. ing.

  The first accumulator 311 is connected to the downstream end of the supply pipeline 67 connected to the main pipeline 61.

  The second accumulator 312 is connected to the vicinity of the discharge side of the makeup valve 60 a (60 b) on the motor supply line 63 via the supply line 313. The size (capacity) of the second accumulator 312 is set smaller than the size of the first accumulator 311.

In addition, the magnitude relationship among the set pressures of the pilot relief valve 70, the back pressure setting valve 64 and the check valve 66 of the makeup circuit 306, the first accumulator 311, and the second accumulator 312 is as follows.
Pilot relief valve 70> back pressure setting valve 64 = first accumulator 311 = second accumulator 312> check valve 66

  In the hydraulic circuit 301 configured as described above, the hydraulic oil discharged from the main relief valve 40 and the pilot relief valve 70 to the main pipeline 61 is stored in the first accumulator 311 via the supply pipeline 67. And is stored in the second accumulator 312 via the motor supply line 63 and the supply line 313.

  When the pressure in the hydraulic cylinder 102 becomes negative, the hydraulic oil stored in the first accumulator 311 is supplied to the supply pipe 67, the main pipe 61, the cylinder supply pipes 62 and 62, the makeup valve 60, 60, the hydraulic cylinder 102 is replenished through the supply pipe 43 and the discharge pipes 44. Thereby, the negative pressure in the hydraulic cylinder 102 is eliminated.

  Further, when the inside of the supply pipe 43 of the hydraulic motor 101 becomes negative pressure, the hydraulic oil stored in the first accumulator 311 is supplied to the supply pipe 67, the main pipe 61, the motor supply pipe 63, The supply line 43 is replenished via the communication line 47, the connection line 45, and the makeup valve 60a (60b).

  However, since the negative pressure generated in the supply pipe 43 is larger than the negative pressure generated in the hydraulic cylinder 102, a large amount of hydraulic oil needs to be replenished instantaneously. Therefore, the hydraulic oil stored in the second accumulator 312 disposed in the vicinity of the discharge side of the makeup valve 60a (60b) is also connected from the supply line 313 to the motor supply line 63, the communication line 47, and the connection. The supply line 43 is replenished via the line 45 and the makeup valve 60a (60b).

  As described above, in the hydraulic circuit 301 of the present embodiment, a new accumulator is disposed near the discharge side of the makeup valve 60a (60b), so that even if the supply line 43 of the hydraulic motor 101 becomes negative pressure, It is possible to immediately supply hydraulic oil sufficient to eliminate the negative pressure to the supply line 43. Therefore, the hydraulic circuit 301 according to the present embodiment can eliminate the delay in the replenishment of the hydraulic oil due to the pressure loss of the supply pipe 43 and the like, and can more efficiently prevent the occurrence of cavitation.

  Further, in the hydraulic circuit 301 of the present embodiment, since the accumulator is divided into a plurality of units, the size of each accumulator can be reduced, so that space can be saved, and the hydraulic pressure can be reduced. The layout of the circuit 301 can be liberalized.

  The other effects are as described in the first embodiment. The second accumulator 312 is not necessarily arranged in the vicinity of the discharge side of the makeup valve 60a (60b), and may be arranged at an arbitrary position. In addition to the accumulator, another form of supply source such as the supply tank shown in the first embodiment may be used.

(Fourth embodiment)
FIG. 4 is a diagram showing a hydraulic circuit 401 of a hydraulic excavator showing a fourth embodiment of the present invention. In the hydraulic circuit 401 of the present embodiment, the same reference numerals are given to the same parts as those of the hydraulic circuit 1 of the first embodiment, and different parts will be mainly described.

  In the hydraulic circuit 401 of the present embodiment, a makeup circuit 406 that supplies hydraulic oil to the drive circuit 4 includes a hose 411 as a hydraulic oil supply source of the present invention. The hose 411 is provided in the vicinity of the discharge side of the makeup valve 60a (60b) in the motor supply line 63.

  In the hydraulic circuit 401 configured as described above, the hydraulic oil discharged from the main relief valve 40 and the pilot relief valve 70 to the main pipeline 61 is stored in the hose 411 via the motor supply pipeline 63. The

  When the pressure in the supply line 43 of the hydraulic motor 101 becomes negative, the hydraulic oil stored in the hose 411 is supplied to the motor supply line 63, the communication line 47, the connection line 45, and the makeup valve 60a. The supply line 43 is replenished via (60b). Thereby, the negative pressure in the supply pipeline 43 is eliminated.

  When the pressure in the hydraulic cylinder 102 becomes negative, the hydraulic oil stored in the hose 411 is supplied to the motor supply pipe 63, the main pipe 61, the cylinder supply pipes 62 and 62, the makeup valve 60, 60, the hydraulic cylinder 102 is replenished via the supply line 43 and the discharge line 44. Thereby, the negative pressure in the hydraulic cylinder 102 is eliminated.

  As described above, in the hydraulic circuit 401 according to the present embodiment, the use of the hose 411 as a hydraulic oil supply source eliminates the need for a special tank such as the supply tank 68 according to the first embodiment, thereby saving space. Can be achieved. Moreover, by using the hose 411, cost reduction can be achieved and attachment property can be improved.

  Further, in the hydraulic circuit 401 according to the present embodiment, the hose 411 is disposed in the vicinity of the discharge side of the makeup valve 60a (60b), so that the operating oil is supplied to the supply line even if the supply line 43 has a negative pressure. It becomes possible to eliminate the negative pressure by replenishing into 43 immediately. Therefore, the hydraulic circuit 401 according to the present embodiment can eliminate the delay in the replenishment of the hydraulic oil due to the pressure loss of the supply pipeline 43, and can more effectively prevent the occurrence of cavitation.

  The other effects are as described in the first embodiment. The hose 411 is not necessarily arranged near the discharge side of the makeup valve 60a (60b), and may be arranged at an arbitrary position.

(Fifth embodiment)
FIG. 5 is a diagram showing a hydraulic circuit 501 of a hydraulic excavator showing a fifth embodiment of the present invention. In the hydraulic circuit 501 of the present embodiment, the same reference numerals are given to the same parts as those of the hydraulic circuit 1 of the first embodiment, and different parts will be mainly described.

  In the hydraulic circuit 501 of the present embodiment, a makeup circuit 506 for supplying hydraulic fluid to the drive circuit 4 is provided with an inflow check valve 561 (the hydraulic fluid of the present invention upstream of the supply pipeline 67 of the main pipeline 61). The return pipe 5 is connected via an inflow device).

In addition, the magnitude relationship among the set pressures of the pilot relief valve 70, the back pressure setting valve 64 and the check valve 66 of the makeup circuit 506, and the check valve 561 for inflow is as follows.
Pilot relief valve 70> back pressure setting valve 64> inflow check valve 561> check valve 66

  In the hydraulic circuit 501 configured as described above, when the pressure in the return line 5 becomes larger than the pressure in the makeup circuit 506, the inflow check valve 561 opens and the makeup circuit 506 and the return pipe are opened. Communicate with Road 5. As a result, the hydraulic oil in the return line 5 flows into the main line 61 via the inflow check valve 561.

In addition, when the pressure in the return line 5 becomes larger than the pressure in the makeup circuit 506, there are the following two cases.
(1) A case where the pressure in the makeup circuit 506 suddenly decreases when a large amount of hydraulic oil is supplied to the hydraulic motor 101 or the hydraulic cylinder 102.
(2) A case where a large amount of hydraulic oil is discharged from the hydraulic motor 101 or the hydraulic cylinder 102 and the pressure in the return pipe 5 suddenly increases due to pipe pressure loss or the like.

  Therefore, in the hydraulic circuit 501 of the present embodiment, even if the pressure in the make-up circuit 506 is suddenly reduced as in (1) above, the hydraulic oil flows into the make-up circuit 506 from the return line 5 side. As a result, the amount of hydraulic oil used to eliminate the negative pressure does not become insufficient. Therefore, the hydraulic circuit 501 of the present embodiment can reliably eliminate the negative pressure generated in the supply conduit 43 and the hydraulic cylinder 102 of the hydraulic motor 101, and can reliably prevent the occurrence of cavitation.

  Further, in the hydraulic circuit 501 of the present embodiment, even when the pressure in the return line 5 suddenly increases as described in (2) above, the hydraulic oil flows from the return line 5 side into the makeup circuit 506. Since it flows in, it becomes possible to return the pressure in the return line 5 to the original state. Therefore, the hydraulic circuit 501 of the present embodiment can suppress a decrease in the driving speed of the hydraulic motor 101 and the hydraulic cylinder 102 due to a rapid increase in the pressure in the return pipe 5, and unnecessary energy. Loss can be reduced. The other effects are as described in the first embodiment.

(Sixth embodiment)
FIG. 6 is a diagram showing a hydraulic circuit 601 of a hydraulic excavator showing a sixth embodiment of the present invention. In the hydraulic circuit 601 of the present embodiment, the same reference numerals are given to the same parts as those of the hydraulic circuit 1 of the first embodiment, and different parts will be mainly described.

  In the hydraulic circuit 601 of the present embodiment, the make-up circuit 606 for supplying hydraulic oil to the drive circuit 4 is a return pipe via the hydraulic oil inflow device 661 on the upstream side of the branch pipe 65 of the main pipe 61. Connected to path 5.

  The inflow device 661 includes an accommodating portion 662, a hydraulic oil filling portion 663 (replenishment source of the present invention) provided in the accommodating portion 662, and a piston 664 slidably disposed in the hydraulic oil filling portion 663. I have.

  The accommodating portion 662 is connected to the main pipeline 61 and the return pipeline 5 by connection pipelines 660a and 660b. The hydraulic oil filling portion 663 is located on the main pipeline 61 side in the housing portion 662. The hydraulic oil filling portion 663 is formed to extend in the connecting direction (the left-right direction in FIG. 6) between the main pipeline 61 and the return pipeline 5.

  The piston 664 is disposed on the return conduit 5 side. The piston 664 includes a small diameter portion 664a disposed in the hydraulic oil filling portion 663 and a large diameter portion 664b coupled to the tip of the small diameter portion 664a (the end on the return conduit 5 side). The large diameter portion 664b is set to have a larger diameter than the small diameter portion 664a.

  A drain portion 666 is provided between the accommodating portion 662 and the small diameter portion 664 a of the piston 664. The drain portion 666 is a portion that stores hydraulic oil that leaks from clearances due to dimensional tolerances between the accommodating portion 662 and the piston 664, and is connected to the oil tank 2 via a drain conduit 665.

The magnitude relationship among the set pressures of the pilot relief valve 70, the back pressure setting valve 64 of the makeup circuit 606, and the check valve 66 is as follows.
Pilot relief valve 70> back pressure setting valve 64 = pressure in main pipeline 61> check valve 66

  In the inflow device 661 configured as described above, the diameter of the piston 664 is different at both ends, that is, the piston 664 has an area difference, so that the piston 664 has a pressure in the return line 5 or a makeup circuit 606 (main circuit). The moving direction (the left-right direction in FIG. 6) is determined by the product of the pressure in the pipe line 61) and the area (pressure-receiving area), that is, the forces applied to the small diameter portion 664a and the large diameter portion 664b.

  More specifically, when the force generated by the pressure in the return line 5 acting on the piston 664 is smaller than the force generated by the pressure in the makeup circuit 606, the piston 664 is on the return line 5 side. Pressed against. The pressure in the return line 5 is substantially equal to the back pressure setting valve 64 = the pressure in the main line 61> the pressure in the return line 5 except in the cases described in (1) and (2) of the fifth embodiment. It is related to pressure. Further, the force acting on the piston 664 in this pressure relationship is set in advance so as to increase on the makeup circuit 606 side, that is, on the small diameter portion 664a side. As a result, the hydraulic oil discharged from the main relief valve 40 or the pilot relief valve 70 to the main pipeline 61 flows into the hydraulic fluid filling portion 663 via the connection pipeline 660a, and the piston 664 moves toward the return pipeline 5 side. It is stored while moving.

  Next, in the case corresponding to (1) of the fifth embodiment, that is, when the supply pipe 43 of the hydraulic motor 101 has a negative pressure, the force acting on the piston 664 is the return pipe 5 side. Therefore, the hydraulic oil stored in the hydraulic oil filling section 663 is connected to the connection pipeline 660a, the main pipeline 61, the motor supply pipeline 63, the communication pipeline 47, the connection pipeline 45, and the makeup. The supply line 43 is replenished via the up valve 60a (60b). Thereby, the negative pressure in the supply pipeline 43 is eliminated.

  When the inside of the hydraulic cylinder 102 becomes negative pressure, the hydraulic oil stored in the hydraulic oil filling unit 663 is connected to the connection pipeline 660a, the main pipeline 61, the cylinder supply pipelines 62 and 62, and the makeup valve 60. , 60, the supply line 43 and the discharge line 44 are supplied into the hydraulic cylinder 102. Thereby, the negative pressure in the hydraulic cylinder 102 is eliminated.

  Further, in the case corresponding to (2) of the fifth embodiment, that is, the pressure in the return pipe 5 that has risen rapidly due to the discharge of a large amount of hydraulic oil is larger than the pressure in the makeup circuit 606. When this happens, as long as the force generated in the pressure in the return pipe 5 is larger than the force generated by the pressure in the makeup circuit 606, the piston 664 is pushed toward the makeup circuit 606, and the piston 664 Move to a position where the forces acting on the whole balance. As a result, the hydraulic oil stored in the hydraulic oil filling unit 663 is replenished by being pushed into the main pipeline 61.

  Therefore, in the hydraulic circuit 601 of the present embodiment, even if the pressure in the makeup circuit 606 drops suddenly, the hydraulic oil flows into the makeup circuit 606 from the return line 5 side, so that the negative pressure is eliminated. There is no shortage of the amount of hydraulic oil used. Therefore, the hydraulic circuit 601 according to the present embodiment can reliably eliminate the negative pressure generated in the supply pipe 43 of the hydraulic motor 101 and the hydraulic cylinder 102, and can reliably prevent the occurrence of cavitation.

  Further, in the hydraulic circuit 601 of the present embodiment, even if the pressure in the return line 5 suddenly increases, the working oil flows into the makeup circuit 606 from the return line 5 side, so the return line 5 It becomes possible to return the internal pressure to the original state. Therefore, the hydraulic circuit 601 of the present embodiment can suppress a decrease in the driving speed of the hydraulic motor 101 and the hydraulic cylinder 102 due to a rapid increase in pressure in the return pipe 5 and can reduce unnecessary energy loss. Can be reduced. The other effects are as described in the first embodiment.

  As mentioned above, although embodiment concerning this invention was illustrated, said embodiment does not limit the content of this invention. Various modifications can be made without departing from the scope of the claims of the present invention.

  For example, in the hydraulic circuits described in the second to sixth embodiments, when the replenishment amount is insufficient as in the hydraulic circuit 1 of the first embodiment, the check valve 66 is used. Then, hydraulic oil may be supplied from the oil tank 2 to the drive circuit 4.

  Further, the configuration of each hydraulic circuit of the third to sixth embodiments may be combined with the hydraulic circuit 201 of the second embodiment.

DESCRIPTION OF SYMBOLS 1 Hydraulic circuit of hydraulic excavator 2 Oil tank 3 Drive pump 5 Return line 6 Make-up circuit 7 Controller 64 Back pressure setting valve (pressure control valve)
68 Supply tank (Supply source)
71 Pilot pump 101 Hydraulic motor (actuator)
102 Hydraulic cylinder (actuator)
201 Hydraulic Circuit of Hydraulic Excavator 206 Makeup Circuit for Motor 301 Hydraulic Circuit of Hydraulic Excavator 306 Makeup Circuit 311 First Accumulator (Supply Source)
312 Second accumulator (supply source)
401 Hydraulic circuit of excavator 406 Make-up circuit 411 Hose (replenishment source)
501 Hydraulic circuit of hydraulic excavator 506 Make-up circuit 561 Check valve for inflow (inflow device)
601 Hydraulic circuit of hydraulic excavator 606 Make-up circuit 661 Inflow device 663 Hydraulic oil filling section (supply source)

Claims (3)

A drive circuit that drives an actuator using hydraulic pressure of hydraulic oil supplied from a drive pump, a control device that controls supply of the hydraulic oil to the drive circuit using a pilot pump, and a discharge from the drive circuit A hydraulic circuit of a construction machine comprising a return pipe that returns the hydraulic oil to the oil tank,
The drive circuit further includes a makeup circuit that replenishes the hydraulic oil, and the makeup circuit sets the hydraulic oil supply source and the pressure in the makeup circuit higher than the pressure in the return line. And a pressure control valve that is connected to the drive circuit separately from the return pipe. In the hydraulic circuit of the construction machine according to claim 1,
The make-up circuit is connected to the return line via the hydraulic oil inflow device, and the inflow device is configured such that the pressure in the return line is greater than the pressure in the make-up circuit. A hydraulic circuit for a construction machine, wherein the hydraulic oil is caused to flow into the makeup circuit from a return pipe side. In the hydraulic circuit of the construction machine according to claim 1 or 2,
The make-up circuit has a plurality of hydraulic oil supply sources.