Hydraulic circuit for construction machine

Abstract

To provide a hydraulic circuit of a construction machine for reducing a shock caused by switching of a work switching valve.SOLUTION: The hydraulic circuit 10 of the construction machine is provided with a straight traveling valve 11 for switching a first unload passage 14 and a second unload passage 15 and a first parallel passage 12 and a second parallel passage 13 according to the operation of a traveling motor and a work actuator, a first signal passage 18 for supplying control pressure from a third pump 6 to the straight traveling valve 11 and reaching a tank 7 through signal passage parts 22A, 22A of traveling switching valves, and a second signal passage 19 branched from the first signal passage 18 and reaching the tank 7 through signal passage parts 25A, 25A, 25A of work switching valves. The signal passages 25A, 24A, and 23A of the work directional control valve are switched between a communication position and a closed position, and when the signal passages 25A, 24A, and 23A of the work directional control valve are switched according to the switching of the work directional control valve, the signal passages 25A, 24A, and 23A are switched after a predetermined time elapses.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydraulic circuit for a construction machine. [Background technology]

[0002] The hydraulic circuit of the construction machine described in Patent Document 1 is equipped with a travel switching valve that controls the supply of hydraulic oil that drives the travel hydraulic actuator, a work switching valve that controls the supply of hydraulic oil that drives the work hydraulic actuator, and a travel switching valve that switches the flow path of hydraulic oil to the travel switching valve and the work switching valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-156135 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the hydraulic circuit of the construction machine described in Patent Document 1, a shock may occur when the work changeover valve is switched. For this reason, there is a need to reduce the shock that occurs when the work changeover valve is switched. [Means for solving the problem]

[0005] The hydraulic circuit for a construction machine that solves the above problem is a hydraulic circuit for a construction machine that is equipped with left and right travel motors and work actuators, and includes a hydraulic oil pump that supplies hydraulic oil to the travel motors and the work actuators, a travel switching valve that controls the supply of hydraulic oil that drives the travel motors, a work switching valve that controls the supply of hydraulic oil that drives the work actuators, a first passage that runs from the hydraulic oil pump to a tank via the travel switching valve and the work switching valve, a second passage that runs from the hydraulic oil pump to a tank via the work switching valve, and the first signal passage that supplies control pressure from the control pressure pump to the traveling / straightening valve and leads to a tank via a signal passage portion of the traveling switching valve; and the second signal passage that branches off from the first signal passage and leads to a tank via a signal passage portion of the work switching valve, wherein the signal passage portion of the work switching valve is switched between a communicating position and a closed position, and when the signal passage portion of the work switching valve switches in accordance with the switching of the work switching valve, the signal passage portion of the work switching valve switches after a predetermined time has elapsed.

[0006] According to the above configuration, when the signal passage portion of the work changeover valve is switched in response to switching of the work changeover valve, the signal passage portion of the work changeover valve is switched after a predetermined time has elapsed. Therefore, when the work changeover valve is switched, the signal passage portion of the work changeover valve can be switched gradually, thereby reducing the shock associated with switching of the work changeover valve.

[0007] In the hydraulic circuit of the above-described construction machine, it is preferable that the signal passage portion of the work changeover valve is provided with a throttle between the communicating position and the closed position, and when the signal passage portion of the work changeover valve is switched, the signal passage portion of the work changeover valve is switched by the throttle after a predetermined time has elapsed.

[0008] In the hydraulic circuit of the construction machine, it is preferable that the signal passage portion of the travel switching valve be switchable between a communicating position and a closed position. In the hydraulic circuit of the above-described construction machine, it is preferable that the signal passage portion of the travel switching valve has a throttle between the communication position and the closed position, and when the signal passage portion of the travel switching valve is switched, the signal passage portion of the travel switching valve is switched by the throttle after a predetermined time has elapsed.

[0009] In the hydraulic circuit of the construction machine, it is preferable to provide a throttle at the branch point between the first signal passage and the second signal passage. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce shocks that accompany switching of the operation changeover valve. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an embodiment of a hydraulic circuit of a construction machine. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Present embodiment) An embodiment of a hydraulic circuit for a construction machine will be described below with reference to Fig. 1. The hydraulic circuit is provided in a hydraulic drive unit that drives the construction machine.

[0013] (Hydraulic drive unit 1) As shown in FIG. 1, a hydraulic drive system 1 is mounted on a construction machine such as a hydraulic excavator. The hydraulic drive system 1 includes a plurality of hydraulic actuators 2. The hydraulic actuators 2 are driven by a hydraulic circuit 10. The hydraulic circuit 10 includes a plurality of switching valves 3 and a traveling valve 11. The plurality of hydraulic actuators 2 include, for example, a first hydraulic motor 2A that drives the right crawler (traveling device), a second hydraulic motor 2B that drives the left crawler (traveling device), a first hydraulic cylinder 2C that drives the arm, a second hydraulic cylinder 2D that drives the boom, and a third hydraulic cylinder 2E that drives an attachment such as a bucket. The first hydraulic motor 2A and the second hydraulic motor 2B correspond to traveling motors. The first hydraulic cylinder 2C, the second hydraulic cylinder 2D, and the third hydraulic cylinder 2E correspond to work actuators.

[0014] The switching valve 3 receives hydraulic oil from the first pump 4 and the second pump 5 and controls the supply of hydraulic oil to the hydraulic actuator 2. The direct travel valve 11 is a hydraulic pilot type spool valve whose spool position is switched by hydraulic oil supplied from the third pump 6. The direct travel valve 11 has a direct travel spool 26. The first pump 4 and the second pump 5 correspond to hydraulic oil pumps. The third pump 6 corresponds to a control pressure pump.

[0015] (Switching valve 3) The switching valve 3 can be switched to multiple positions by sliding a spool. FIG. 1 shows a spool provided in the switching valve 3. The switching valve 3 is a hydraulic pilot type spool valve in which the spool position is switched by a control pressure output from an electromagnetic proportional valve (not shown). A switching valve 3 is provided for each hydraulic actuator 2. The supply of hydraulic oil to the first hydraulic motor 2A is controlled by the first switching valve 3A. The supply of hydraulic oil to the second hydraulic motor 2B is controlled by the second switching valve 3B. The supply of hydraulic oil to the first hydraulic cylinder 2C is controlled by the third switching valve 3C. The supply of hydraulic oil to the second hydraulic cylinder 2D is controlled by the fourth switching valve 3D. The supply of hydraulic oil to the third hydraulic cylinder 2E is controlled by the fifth switching valve 3E. The first switching valve 3A and the second switching valve 3B correspond to travel switching valves. The third switching valve 3C, the fourth switching valve 3D, and the fifth switching valve 3E correspond to the work switching valves.

[0016] The first switching valve 3A has a first spool 21 and a first signal passage portion 21A. The second switching valve 3B has a second spool 22 and a second signal passage portion 22A. The third switching valve 3C has a third spool 23 and a third signal passage portion 23A. The fourth switching valve 3D has a fourth spool 24 and a fourth signal passage portion 24A. The fifth switching valve 3E has a fifth spool 25 and a fifth signal passage portion 25A.

[0017] (Hydraulic circuit 10) The hydraulic circuit 10 includes a traveling / direction valve 11, multiple switching valves 3, a first parallel passage 12, a second parallel passage 13, a first unloading passage 14, a second unloading passage 15, a first signal passage 18, and a second signal passage 19. The first spool 21 and the second spool 22 are traveling section spools. The third spool 23, the fourth spool 24, and the fifth spool 25 are working section spools. The traveling section spools receive hydraulic oil preferentially over the working section spools. The traveling / direction valve 11 switches between the first unloading passage 14 and the second unloading passage 15 and the first parallel passage 12 and the second parallel passage 13 in response to the operation of the traveling motor and the working actuator. The first parallel passage 12 and the second parallel passage 13 correspond to the second passage that runs from the hydraulic oil pump to the tank via the working switching valve. The first unloading passage 14 and the second unloading passage 15 correspond to a first passage extending from the hydraulic oil pump to the tank via the travel switching valve and the work switching valve.

[0018] The first pump 4 is connected to the third spool 23, fourth spool 24, and fifth spool 25, which are working section spools, via the traveling valve 11 and the first parallel passage 12. The first pump 4 branches off just before the traveling valve 11 and passes through the first spool 21 and second spool 22, which are traveling section spools, and the third spool 23, fourth spool 24, and fifth spool 25, which are working section spools, via the first unloading passage 14, and is connected to the tank 7A.

[0019] The second pump 5 is connected to the tank 7A via the traveling valve 11 and the second unloading passage 15, passing through the first spool 21 and the second spool 22, which are traveling section spools, and the third spool 23, the fourth spool 24, and the fifth spool 25, which are working section spools. The second pump 5 also branches off just before the traveling valve 11 and is connected via the second parallel passage 13 to the third spool 23, the fourth spool 24, and the fifth spool 25, which are working section spools.

[0020] The third pump 6 is connected to a first signal passage 18 and a second signal passage 19 branching from the first signal passage 18. The first signal passage 18 has a first orifice 16 and a second orifice 17 and is connected to the pressure-receiving surface of the straight-traveling spool 26. The first signal passage 18 passes through a first signal passage portion 21A of the first spool 21 and a second signal passage portion 22A of the second spool 22 and is connected to a tank 7B. The second signal passage 19 branches within the first signal passage portion 21A of the first spool 21 and is connected to a tank 7C. The second signal passage 19 branches from the first signal passage 18 between the first orifice 16 and the second orifice 17 and passes through a third signal passage portion 23A of the third spool 23, a fourth signal passage portion 24A of the fourth spool 24, and a fifth signal passage portion 25A of the fifth spool 25 and is connected to a tank 7D. Because the hydraulic oil supplied from the third pump 6 is supplied via the first orifice 16 and the second orifice 17, sudden pressure changes can be reduced. The tanks 7A, 7B, 7C, and 7D may be a common tank or may be different tanks.

[0021] The direct-travel valve 11 can be switched to three positions. When the direct-travel spool 26 is in the neutral position, hydraulic oil passes through the first selector valve 3A with the flow rate restricted by the throttle, and is supplied to the working spool. When the direct-travel spool 26 is in the first operating position on the left, hydraulic oil from the first pump 4 is supplied to the first selector valve 3A, and hydraulic oil from the second pump 5 is supplied to the working spool. When the first spool 21 is in the second operating position on the right, hydraulic oil from the first pump 4 is supplied to the working spool, and hydraulic oil from the second pump 5 is supplied to the first selector valve 3A. The neutral position corresponds to the communication position.

[0022] The first switching valve 3A can be switched to three positions. When the first spool 21 is in the neutral position, hydraulic oil passes through and is supplied to the second switching valve 3B. When the first spool 21 is in the first operating position on the left, hydraulic oil is supplied to the first hydraulic motor 2A in a first direction. When the first spool 21 is in the second operating position on the right, hydraulic oil is supplied to the first hydraulic motor 2A in a second direction. The first signal passage portion 21A can be switched to three positions in conjunction with the movement of the first spool 21. When the first signal passage portion 21A is in the neutral position, hydraulic oil is supplied to the second signal passage portion 22A and discharged to the tank 7C. When the first signal passage portion 21A is in the left or right operating position, hydraulic oil is supplied to the second signal passage portion 22A. The neutral position corresponds to the communication position.

[0023] The second switching valve 3B can be switched to three positions. When the second spool 22 is in the neutral position, hydraulic oil passes through and is supplied to the fifth switching valve 3E. When the second spool 22 is in the first operating position on the left, hydraulic oil is supplied to the second hydraulic motor 2B in a first direction. When the second spool 22 is in the second operating position on the right, hydraulic oil is supplied to the second hydraulic motor 2B in a second direction. The second signal passage portion 22A can be switched to three positions in conjunction with the movement of the second spool 22. When the second signal passage portion 22A is in the neutral position, hydraulic oil is discharged to the tank 7B. When the second signal passage portion 22A is in the left or right closed position, the supply of hydraulic oil is cut off. The neutral position corresponds to the communication position.

[0024] The fifth switching valve 3E can be switched to three positions. When the fifth spool 25 is in the neutral position, hydraulic oil passes through and is supplied to the fourth switching valve 3D. When the fifth spool 25 is in the first operating position on the left side, hydraulic oil is supplied to the third hydraulic cylinder 2E in a first direction. When the fifth spool 25 is in the second operating position on the right side, hydraulic oil is supplied to the third hydraulic cylinder 2E in a second direction. The fifth signal passage portion 25A can be switched to three positions in conjunction with the movement of the fifth spool 25. The fifth signal passage portion 25A has throttles 25B provided between the neutral position and left and right closed positions. Note that the throttles 25B are illustrated schematically. When the fifth signal passage portion 25A is in the neutral position, hydraulic oil is supplied to the fourth signal passage portion 24A. When the fifth signal passage portion 25A is in the left or right closed position, the supply of hydraulic oil is cut off. When the fifth signal passage portion 25A is switched from the neutral position to the closed position, the fifth signal passage portion 25A is switched after a predetermined time has elapsed. That is, the fifth signal passage portion 25A is gradually switched by the throttle 25B. The neutral position corresponds to the communicating position.

[0025] The fourth switching valve 3D can be switched to three positions. When the fourth spool 24 is in the neutral position, hydraulic oil passes through and is supplied to the third switching valve 3C. When the fourth spool 24 is in the first operating position on the left side, hydraulic oil is supplied to the second hydraulic cylinder 2D in a first direction. When the fourth spool 24 is in the second operating position on the right side, hydraulic oil is supplied to the second hydraulic cylinder 2D in a second direction. The fourth signal passage portion 24A can be switched to three positions in conjunction with the movement of the fourth spool 24. The fourth signal passage portion 24A has throttles 24B provided between the neutral position and left and right closed positions. Note that the throttles 24B are illustrated schematically. When the fourth signal passage portion 24A is in the neutral position, hydraulic oil is supplied to the third signal passage portion 23A. When the fourth signal passage portion 24A is in the left or right closed position, the supply of hydraulic oil is cut off. When the fourth signal passage portion 24A is switched from the neutral position to the closed position, the fourth signal passage portion 24A is switched after a predetermined time has elapsed. That is, the fourth signal passage portion 24A is gradually switched by the orifice 24B. The neutral position corresponds to the communicating position.

[0026] The third switching valve 3C can be switched to three positions. When the third spool 23 is in the neutral position, hydraulic oil passes through and is discharged into the tank 7A. When the third spool 23 is in the first operating position on the left side, hydraulic oil is supplied to the first hydraulic cylinder 2C in a first direction. When the third spool 23 is in the second operating position on the right side, hydraulic oil is supplied to the first hydraulic cylinder 2C in a second direction. The third signal passage portion 23A can be switched to three positions in conjunction with the movement of the third spool 23. The third signal passage portion 23A has a throttle 23B provided between the neutral position and the left and right closed positions. Note that the throttle 23B is illustrated schematically. When the third signal passage portion 23A is in the neutral position, hydraulic oil is discharged into the tank 7A. When the third signal passage portion 23A is in the left and right closed positions, the supply of hydraulic oil is cut off. When the third signal passage portion 23A is switched from the neutral position to the closed position, the third signal passage portion 23A is switched after a predetermined time has elapsed. That is, the third signal passage portion 23A is gradually switched by the orifice 23B. The neutral position corresponds to the communicating position.

[0027] (Action of this embodiment) When the first spool 21 and the second spool 22, which are the traveling spools, are switched from the neutral position to the operating position, the first signal passage 21A and the second signal passage 22A are switched to the closed position, blocking the passages from the third pump 6 to the tanks 7B and 7C. At this time, if at least one of the working spools, the third spool 23, the fourth spool 24, and the fifth spool 25, is switched, the opening area of ​​the signal passage of the working spool decreases according to the amount of switching of the working spool. Therefore, the pressure upstream of the working spool in the second signal passage 19 increases. However, the pressure acting on the pressure-receiving portion of the straight-traveling spool 26 increases gradually due to the first orifice 16 and the second orifice 17, allowing the straight-traveling spool 26 to be switched gradually.

[0028] Furthermore, when the first signal passage 18 from the third pump 6 to the tanks 7B, 7C is blocked, the pressure in the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the working spool increases. At this time, when at least one of the working spools, the third spool 23, the fourth spool 24, and the fifth spool 25, is switched, the working spool can be switched gently by the orifices 23B, 24B, and 25B provided in the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the working spool.

[0029] (Effects of this embodiment) Next, the effects of this embodiment will be described. (1) When the corresponding third signal passage portion 23A, fourth signal passage portion 24A, and fifth signal passage portion 25A are switched in association with the switching of at least one of the third switching valve 3C, fourth switching valve 3D, and fifth switching valve 3E, the corresponding third signal passage portion 23A, fourth signal passage portion 24A, and fifth signal passage portion 25A are switched after a predetermined time has elapsed. Therefore, when at least one of the third switching valve 3C, fourth switching valve 3D, and fifth switching valve 3E is switched, the corresponding third signal passage portion 23A, fourth signal passage portion 24A, and fifth signal passage portion 25A can be switched gradually. Therefore, it is possible to reduce shocks associated with the switching of the third switching valve 3C, fourth switching valve 3D, and fifth switching valve 3E.

[0030] (2) The throttles 23B, 24B, 25B are provided between the communicating position and the closed position of the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the work switching valve. Therefore, when the third switching valve 3C, the fourth switching valve 3D, and the fifth switching valve 3E are switched, the corresponding third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A can be switched gradually by the throttles 23B, 24B, 25B.

[0031] (3) When the second signal passage portion 22A of the second selector valve 3B is in the closed position, the signal pressure in the first signal passage 18 is no longer discharged to the tank 7B, and the signal pressure in the second signal passage 19 increases. At this time, even if the signal pressure in the second signal passage 19 increases, the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the work selector valve can be switched gradually by the orifices 23B, 24B, and 25B provided between the communicating position and the closed position of the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the work selector valve.

[0032] (4) The first and second orifices 16 and 17 are provided at the branch point between the first signal passage 18 and the second signal passage 19. Therefore, the increase in control pressure caused by the closure of the first signal passage portion 21A and the second signal passage portion 22A of the travel switching valve or the third signal passage portion 23A, the fourth signal passage portion 24A, and the fifth signal passage portion 25A of the work switching valve can be made to change gradually.

[0033] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0034] In the above embodiment, a throttle may be provided between the open position and the closed position of the signal passage portion of the travel switching valve. That is, a throttle may be provided between the neutral position and the closed position of the first signal passage portion 21A of the first switching valve 3A and the second signal passage portion 22A of the second switching valve 3B. With this configuration, when the first switching valve 3A and the second switching valve 3B are switched, the first signal passage portion 21A and the second signal passage portion 22A of the travel switching valve can be switched gradually by the throttle.

[0035] In the above embodiment, the first and second throttles 16 and 17 are provided at the branch points of the first and second signal paths 18 and 19. However, the first and second throttles 16 and 17 may be omitted.

[0036] In the above embodiment, a third hydraulic motor may be provided as the hydraulic actuator for rotating the main body of the excavator including the cab relative to the traveling device, etc. In this case, a switching valve for controlling the hydraulic oil supplied to the third hydraulic motor is provided, and the spool of this switching valve is included in the working unit spool.

[0037] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved. [Explanation of symbols]

[0038] 1...Hydraulic drive unit 2...Hydraulic actuator 2A...First hydraulic motor (travel motor) 2B: Second hydraulic motor (travel motor) 2C...First hydraulic cylinder (work actuator) 2D...Second hydraulic cylinder (work actuator) 2E...Third hydraulic cylinder (work actuator) 3...Switching valve 3A...First switching valve (travel switching valve) 3B...Second switching valve (travel switching valve) 3C...Third switching valve (operation switching valve) 3D...4th switching valve (operation switching valve) 3E...5th switching valve (operation switching valve) 4...First pump (hydraulic oil pump) 5...Second pump (hydraulic oil pump) 6...Third pump (controlled pressure pump) 7. Tank 10...Hydraulic circuit 11...Straight-travel valve 12...1st parallel passage (2nd passage) 13...Second parallel passage (Second passage) 14...First unloading aisle (first aisle) 15...Second unloading aisle (first aisle) 16...First aperture 17...Second aperture 18...First signal passage 19...Second signal passage 21...First spool (running spool) 21A…1st signal passage section 22...Second spool (running spool) 22A…Second signal passage section 23...Third spool (working spool) 23A...Third signal passage section 23B...Aperture 24...Fourth spool (working spool) 24A…4th signal passage section 24B...Aperture 25...5th spool (working spool) 25A...5th signal passage section 25B...Aperture 26...Straight running spool

Claims

1. A hydraulic circuit for a construction machine equipped with left and right travel motors and a work actuator, a hydraulic oil pump that supplies hydraulic oil to the travel motor and the work actuator; a travel switching valve that controls the supply of hydraulic oil that drives the travel motor; a work switching valve that controls the supply of hydraulic oil that drives the work actuator; a first passage extending from the hydraulic oil pump to a tank via the travel switching valve and the work switching valve; a second passage extending from the hydraulic oil pump to a tank via the operation changeover valve; a traveling direct valve that switches between the first passage and the second passage in response to operations of the traveling motor and the work actuator; a control pressure pump for supplying a control pressure for controlling the traveling valve; a first signal passage that supplies control pressure from the control pressure pump to the traveling direction valve and leads to a tank via a signal passage portion of the traveling direction switching valve; a second signal passage branching from the first signal passage and leading to a tank via a signal passage portion of the work changeover valve, The signal passage portion of the work changeover valve is switched between a communicating position and a closed position, and when the signal passage portion of the work changeover valve is switched in accordance with the switching of the work changeover valve, the signal passage portion of the work changeover valve is switched after a predetermined time has elapsed. Hydraulic circuits for construction machinery.

2. the signal passage portion of the operation changeover valve has a restriction between the communicating position and the closed position, When the signal passage portion of the work changeover valve is switched, the signal passage portion of the work changeover valve is switched after a predetermined time has elapsed due to the restriction.

2. A hydraulic circuit for a construction machine according to claim 1.

3. The signal passage portion of the travel switching valve is switched between a communicating position and a closed position.

3. A hydraulic circuit for a construction machine according to claim 2.

4. the signal passage portion of the travel switching valve is provided with a throttle between the communicating position and the closed position, When the signal passage portion of the travel switching valve is switched, the signal passage portion of the travel switching valve is switched after a predetermined time has elapsed due to the throttle.

4. A hydraulic circuit for a construction machine according to claim 3.

5. A restriction is provided at the branch point between the first signal path and the second signal path. The hydraulic circuit for a construction machine according to any one of claims 1 to 4.

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