JPH0624448Y2 - Hydraulic circuit of hydraulic shovel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic circuit of a hydraulic excavator having excellent workability.

Prior Art FIG. 4 is a hydraulic circuit diagram of the prior art.
1L and 1R are left and right traveling motors, 2 is a swing motor, and 3,
4 and 5 are hydraulic cylinders for work attachments,
6 is a first pump, 7 is a regulator for adjusting the tilt angle of the first pump 6, 8 is a second pump, 9 is a regulator for the second pump 8, 10 is a pilot pump, 11L and 11R are left and right traveling valves, and 12 is Swirling valve, 13, 14 and 15 are cylinder valves, 16 is a straight traveling valve, 17 is a straight traveling valve 16
Pilot pressure receiving part, 18 is an opening / closing valve, 19 is a shuttle valve, 20 is a traveling relief valve, 21L and 21R are work attachment relief valves, 22L and 22R are left and right foot relief valves, and 23L and 23R are left and right throttle parts. , 24 is a remote control valve for switching the swivel valve 12, 25 is a cylinder valve 15
Remote control valves for switching, 26, 27 and 28 are shuttle valves, and 29 and 30 are check valves.

Next, a conventional hydraulic circuit will be described with reference to FIG. The various hydraulic actuators equipped in the hydraulic excavator are divided into two groups A and B, the left and right traveling valves 11L and 11R are provided in the front row of each group, respectively, and this and other actuator switching valves are all connected in parallel. Group A, B
The actuator of is operated via each switching valve. The actuators 2, 3, 4, 5 other than the left and right traveling motors 1L, 1R are operated by the remote control valve operation via the switching valves 12, 13, 14, 15, respectively. In FIG. 4, as an example, only the remote control valve 24 for switching the swirl valve 12 and the remote control valve 25 for switching the cylinder valve 15 are shown. Although both the first pump 6 and the second pump 7 are variable displacement hydraulic pumps, the negative control pressures from the upstream oil passages 31L and 31R of the foot relief valves 22L and 22R act on the regulators 9 and 7, respectively. The turning angle can be adjusted. The relief set pressure of the traveling relief valve 20 is the same as that of the work attachment relief valve 2
Since the pressure is set higher than 1L and 21R, the relief valves 21L and 21R on the side of each actuator 2, 3, 4, 5
When the vehicle is relieved by the load, the traveling relief valve 20 does not relieve. On the other hand, the traveling valve 11L and the swing valve 1
2, a center bypass oil passage 32 penetrating the cylinder valve 15
A low pressure foot relief valve 22L and a throttle portion 23L are connected in parallel to the outlet side of L, and an upstream oil passage 31L thereof communicates with a regulator 9 of the second pump 8 via an oil passage 33L. Similarly, a low pressure foot relief valve 22R and a throttle portion 23R are connected in parallel on the outlet side of a center bypass oil passage 32R that penetrates the traveling valve 11R and the cylinder valves 13 and 14, and the upstream oil passage 31R is an oil passage. It communicates with the regulator 7 of the first pump 6 via 33R. Then, the outlet side oil passages 33L, 33 of the center bypass oil passages 32L, 32R
The negative control pressures derived to R act on the regulators 9 and 7, respectively, and adjust the tilt angles of the second pump 8 and the first pump 6. In the negative control system of this hydraulic circuit, when the negative control pressure is increased, the pump discharge oil amount decreases in accordance with the command pressure, and conversely, when the negative control pressure is decreased, the pump discharge oil amount increases. Further, in this hydraulic circuit, the second pump 8 discharge side oil passage 34 and the first pump 6 discharge side oil passages 35, 36 are provided.
Is provided on the downstream side of the vehicle, and on the other hand, in the oil passages 37 and 38 that connect the left traveling motor 1L and the left traveling valve 11L,
An opening / closing valve 18 is provided in parallel with the left traveling motor 1L, and the opening / closing valve 18 is a remote control valve 24 when the left traveling motor 1L is stopped.
The pilot oil passage 39 from 25 is cut off, and the pilot oil passage 39 is opened when the left traveling motor 1L is operated. Therefore, when only the left and right travel valves 11L and 11R are operated and the other actuator remote control valves are not operated, the pilot pressure oil from the pilot pump 10 is not sent to the oil passage 39, so the travel straight valve 16 is set to the a position. The left and right traveling motors 1L and 1R are connected to the second and first
Discharge pressure oil is separately supplied from the pumps 8 and 6, respectively. However, when both the left and right traveling valves 11L and 11R are operated and, for example, the remote control valve 25 among the work attachment remote control valves is simultaneously operated, the pilot pressure oil from the pilot pump 10 is supplied to the oil passage 40 and the remote control valve 2.
5, the shuttle valve 27, the oil passage 41, the shuttle valve 28, the oil passage 39, the opening oil passage position of the opening / closing valve 18, and the oil passage 42, and acts on the pilot pressure receiving portion 17. Therefore, the traveling straight valve 1
6 is switched from the a position to the b position, the pressure oil discharged from the first pump 6 is supplied in parallel to the left and right traveling motors 1L and 1R, and the pressure oil discharged from the second pump 8 is swung valve 12,
Oil is sent to the cylinder valves 13, 14, 15 side. It should be noted that the throttle portion 43 is provided between the parallel open oil passages in the position B of the traveling rectilinear valve 16.
Is provided, the discharge-side oil passage 36 of the first pump 6 and the discharge-side oil passage 34 of the second pump 8 communicate with each other via the throttle portion 43 when the straight travel valve 16 is switched to the low position. .

Problems to be Solved by the Invention In the above-mentioned conventional hydraulic circuit, when the work attachment relief valves 21L, 21R are relieved, the relief hydraulic oil is supplied to the upstream oil passages 31L, 31R of the foot relief valves 22L, 22R. And a negative control cutoff function for reducing the amount of oil discharged from the second pump 8 or the first pump 6 when the relief set pressure is reached. In other words, since the hydraulic oil that is relieved and returned to the return circuit causes energy loss, the pump discharge capacity is minimized from the viewpoint of energy saving. Therefore, if the work attachment relief valve does not relieve while the hydraulic excavator is operating the work attachment at the same time, the negative control cut-off function will not work, so a sufficient amount of discharge oil will be supplied to each actuator. Does not happen.

However, the hydraulic excavator may travel to climb a plate with a large inclination angle or to escape from the mud. At that time, when one of the work attachments is operated at the same time and the work attachment relief valve, for example, 21L is relieved by the load applied to the work attachment, it becomes a negative control cut-off command, which acts on the regulator 9 of the second pump 8. The amount of oil discharged from the pump 8 is reduced. Further, since the traveling straight valve is switched to the parallel opening oil passage position having the throttle portion during the traveling, the pressure oil on the traveling motor side flows out to the work attachment side oil passage through the throttle portion, and the traveling motor side The hydraulic pressure drops to the relief set pressure of the work attachment relief valve. As a result, the operating speed of the work attachment of the hydraulic excavator is reduced, and the traveling speed and traveling force are also reduced, resulting in difficulty in work.

The present invention solves the above problems and provides a hydraulic circuit that can continue reliable operation without deteriorating its operability even when a large load is applied to both the running and work attachments at the same time. The purpose is.

Means for solving the problems a. In the hydraulic circuit of the present invention, various hydraulic actuators mounted on the hydraulic excavator are divided into two groups A and B,
The left and right traveling valves are arranged in tandem on the most upstream side of each group A and B, and the other switching valves on the downstream side are arranged in parallel, and the above hydraulic actuators are used to switch each switching valve by the first and second pumps. The pilot pressure from the pilot pump from the remote control valve to act on the pilot pressure receiving portion of the switching valve of the actuator, and to the discharge side oil passages of the first and second pumps. The first and second pumps are driven by the left and right traveling motors alone to the position of the oil passage leading from one pump to the one traveling valve during the independent traveling, and by the pilot pressure derived from the remote control valve when the traveling and the work attachments are simultaneously operated. In a hydraulic circuit provided with a straight traveling valve that can be switched to an oil passage position that allows the pressure oil from each to pass separately, Between the pressure oil supply side oil passage and the center bypass downstream side oil passage of the work attachment changeover valve in the groups A and B, a boost relief valve and a tank communication pilot changeover valve are provided in series, respectively. ． The boost pilot pressure receiving portion of each boost relief valve and the pilot pressure receiving portion of each pilot switching valve are configured to communicate with the pilot pressure receiving portion of the traveling straight valve.

Action a. In the second case where the left and right traveling valves and one of the other actuator switching valves are in operating positions other than the neutral position, the pilot switching valves connected to the downstream side of the work attachment relief valves of groups A and B are both tanks. The pressure is switched to the communication oil passage position, and at the same time, the pilot pressure acts on the boost pilot pressure receiving portion of the boost relief valve, and the relief set pressure of the boost relief valve changes to the boost relief set pressure.

B. As described above, when the pressure relief valve that has changed to the boost relief set pressure is relieved, the relief hydraulic oil returns to the oil tank, so that it does not act on the regulators of the first and second pumps. Therefore, since the negative control cutoff command is not issued, the amount of oil discharged from the first and second pumps does not decrease.

C. Therefore, if the hydraulic excavator climbs up a plate with a large inclination angle or activates the work attachment while escaping from mud, the pressure relief valve changes to high pressure relief pressure. Can be boosted. In addition, even when the pressure relief valve is relieved due to the work load, the first, second
The amount of oil discharged from the pump does not decrease, and the work can be continued.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of this invention. In the figure, 1L and 1R are left and right traveling motors, 2 is a swing motor,
3, 4 and 5 are hydraulic cylinders for work attachments, 6 is a first pump, 7 is a regulator for adjusting the tilt angle of the first pump 6, 8 is a second pump, 9 is a regulator of the second pump 8, and 10 is Pilot pump, 11L, 11R
Is a left-right traveling valve, 12 is a swing valve, 13 is a cylinder valve, 13 is a straight valve, 16 is a traveling straight valve, 17 is a pilot pressure receiving portion of the traveling straight valve 16, 18 is an opening / closing valve, 19 is a shuttle valve, 20 is a Travel relief valves, 44L and 44R are pilot switching valves, 62L and 62R are boost relief valves,
Reference numerals 63L and 63R denote boost pilot pressure receiving portions of the boost relief valves 62L and 62R, respectively. Here, the relief setting pressure of the traveling relief valve 20 is set to be higher than the pressure setting relief pressures of the pressure relief valves 62L and 62R. Further, the configuration of the hydraulic circuit of the present invention is different from that of the prior art hydraulic circuit in that the pressure relief valves 62L and 62R of the prior art are replaced by pressure relief valves 62L and 62R instead of the work attachment relief valves 21L and 21R of FIG. Pilot switching is provided between the oil passage on the oil supply side and the regulators 9 and 7 for the second and first pumps, and between the regulators 9 and 7 on the downstream side of the pressure relief valves 62L and 62R. The valves 44L and 44R are provided, and the pilot pressure receiving portions 45L and 45R of the pilot switching valves 44L and 44R and the boost relief valve 6 are provided.
2L, 62R boost pilot pressure receiving part 63L, 63R
Are connected to each other and are communicated with the pilot pressure receiving portion 17 of the straight travel valve 16.

Next, the operation function of the hydraulic circuit of this invention will be described with reference to FIG. A case will be described in which any other actuator (for example, the hydraulic cylinder 5) is operated while the hydraulic excavator is running. When the left traveling valve 11L is simultaneously operated to the c position and the right traveling valve 11R is simultaneously operated to the two position, and the remote control valve 25 is operated to the e position, a part of the pressure oil for operating the left traveling motor 1L is transferred to the oil passage 38, It acts on the pilot pressure receiving portion 48 of the opening / closing valve 18 via 47 and switches the opening / closing valve 18 to the open oil passage position, and the pilot pressure oil from the pilot pump 10 is changed to the oil passage 49, the remote control valve 25, the pilot oil. Via path 50, cylinder valve 15 is switched to the F position.
At the same time, the pilot pressure oil from the pilot pump 10 receives the remote control valve 25, the shuttle valve 27, the oil passage 41,
It acts on the pilot pressure receiving portion 17 of the traveling rectilinear valve 16 via the shuttle valve 28, the oil passage 39, the opening oil passage position of the opening / closing valve 18, and the oil passages 51 and 52, and moves the traveling rectilinear valve 16 from the position a to the position b. Switch. At the same time, the pilot pressure oil branches in the oil passage 51, passes through the oil passages 53, 54 and the oil passage 64, and receives the pilot pressure receiving portion 45R of the pilot switching valve 44R and the boost pilot pressure receiving pressure of the boost relief valve 62R. The pilot pressure oil acting on the portion 63R is further branched at the oil passage 53, passes through the oil passages 55 and 65 and the oil passage 66, and then the pilot pressure receiving portion 45L of the pilot switching valve 44L and the boost relief valve 62L. It acts on the boost pilot pressure receiving portion 63L. Therefore, the pilot switching valves 44L and 44R are both switched to the tank communication oil passage position, and at the same time, the relief setting pressures of the boost relief valves 62L and 62R are both changed to the boost relief setting pressure. Further, the discharge pressure oil from the first pump 6 is supplied to the discharge side oil passage 35,
One of them branches from it to the left traveling motor 1L via the oil passage 36, the position of the traveling straight valve 16, the oil passage 56, and the left position of the left traveling valve 11L, and the other branches from the discharge side oil passage 35. The right travel motor 1R is reached through the oil path 57 and the two positions of the right travel valve 11R, and the left and right travel motors 1L and 1R are simultaneously rotated. Then, the discharge pressure oil of the second pump 8 passes through the discharge side oil passage 34, the low position of the straight travel valve 16, the oil passage 58, the check valve 29, the oil passages 59 and 60, and the cylinder valve 15 to the hydraulic cylinder 5 and then to the hydraulic cylinder 5. Activate. And in that case,
Even if an excessive load is applied to the hydraulic cylinder 5, the pressure relief type relief valve 62L has its relief set pressure increased,
The hydraulic cylinder 5 does not relieve until its operating pressure rises to the boost relief setting pressure. Therefore, when the pressure relief valve 62L is relieved, the pressure relief valve 62L from the upstream side oil passage 59 of the cylinder valve 15, the tank communication oil passage position of the pilot switching valve 44L, the oil passage 61,
The relief hydraulic oil returns to the oil tank 46. As described above, in the hydraulic circuit of the present invention, when the work attachment is operated while the hydraulic excavator is running, the relief set pressure of the boost relief valve is increased, so that the work attachment operating pressure can be made higher. it can. Further, even if the pressure relief valve is relieved, the relief hydraulic oil returns to the oil tank. Therefore, the relief hydraulic oil does not act on the regulator. In this case, the negative control cutoff function does not work, and therefore the discharge oil amounts of the first and second pumps do not decrease.

Next, FIG. 3 shows another embodiment according to the present invention.
It is a hydraulic circuit diagram which is not a negative control system. The pressure relief valves 67L and 67R are provided between the pressure oil supply side oil passages 68L and 68R and the center bypass downstream side oil passages 69L and 69R of the work attachment switching valve, and the pressure relief relief valves 67L and 67R are provided. The pilot pressure receiving portions 70L and 70R are communicated with the pilot pressure receiving portion 17 of the straight-travel valve 16. So, the left and right traveling valve 11
When L and 11R are simultaneously switched and the remote control valve for work attachment (for example, remote control valve 25) is operated, the pilot pressure oil from the pilot pump 10 acts on the pilot pressure receiving portion 17 of the straight travel valve 16. , The traveling straight valve 16 is switched from the a position to the b position. At the same time, the pilot pressure oil passes from the oil passage 51 through the oil passages 71, 72, 73, and then the pressure relief valves 67L, 6L.
The 7R act on the pilot pressure receiving portions 70L and 70R, respectively. Therefore, since the relief set pressures of the pressure relief valves 67L and 67R are increased, the working pressure of the work attachment can be increased.

Effect of the Invention As described above, the hydraulic circuit according to the present invention supplies pressure oil to the both of the left and right traveling motors and the other actuators simultaneously when they are simultaneously operated by separate first and second pumps. In the hydraulic circuit that can switch the traveling straight valve, a boost relief valve and a tank switching pilot switching valve are installed between the pressure oil supply side oil passage of the work attachment switching valve and the center bypass downstream oil passage. The boost pressure pilot pressure receiving portion of each boost relief valve and the pilot pressure receiving portion of each pilot switching valve are connected in series to the pilot pressure receiving portion of the above-described straight-travel valve.

In the conventional hydraulic circuit, when the left and right traveling motors and other actuators are simultaneously operated, for example, the hydraulic excavator operates one of the work attachments while traveling, and the work attachment relief valve is operated by the load on the work attachment. When the relief is performed, it becomes a negative control cutoff command, which acts on the regulator of the second pump and reduces the amount of oil discharged from the second pump. For this reason, for example, when the hydraulic excavator escapes from climbing sloping land or from mud, if the work attachment is used to relieve the work attachment relief valve, the pump discharge oil volume will decrease, so the work attachment will operate. The speed and traveling speed decreased, and the above-mentioned work became difficult.

However, in the hydraulic circuit according to the present invention, when the hydraulic excavator uses the work attachment when climbing up sloping ground or exiting mud, the working pressure of the work attachment increases because the relief set pressure of the pressure relief valve increases. Can be at a higher pressure. Further, even if the boost relief valve is relieved when the load of the work attachment is large, the pump discharge oil amount does not decrease.

Therefore, the hydraulic circuit according to the present invention does not increase the relief set pressure of the work attachment and does not reduce the pump discharge oil amount when the other work attachment is operated during traveling. In addition, the workability of the hydraulic excavator can be improved by performing a reliable operation without reducing the operating force, the traveling speed, and the traveling force.

[Brief description of drawings]

1 and 2 are hydraulic circuit diagrams according to the present invention, FIG. 3 is a hydraulic circuit diagram of another embodiment of the present invention, and FIG. 4 is a hydraulic circuit diagram of the prior art. 1L, 1R …… Left and right traveling motors 3, 4, 5 …… Hydraulic cylinders 6,6 ′ …… First pump 7,7 ′, 9,9 ′ …… Regulator 8,8 ′ …… Hydraulic pump 16 …… Traveling Linear valve 18 …… Open / close valve 44L, 44R …… Pilot switching valve 62L, 62R, 67L, 67R …… Boosted relief valve

Claims (1)

[Scope of utility model registration request] 1. Various hydraulic actuators mounted on a hydraulic excavator are divided into two groups A and B, and the left and right traveling valves are arranged on the most upstream side of each group A and B, and another traveling valve is arranged in series with the traveling valve. The actuator switching valve is arranged, and the other actuator switching valve on the downstream side is arranged in parallel so that the hydraulic actuator can be operated by the first and second pumps through the respective switching valves. Of the pilot pressure of the actuator switching valve to act on the pilot pressure receiving portion of the actuator switching valve, and the pressure from the second pump when only the traveling valve is operated in the discharge side oil passages of the first and second pumps. When oil is introduced to one travel valve and the travel valve is operated and another actuator switching valve is operated, pressure oil from the first pump is applied to the left and right travel valves and pressure oil from the second pump is applied. In the hydraulic circuit in which the traveling straight valve that can be switched to the oil passage position that leads to the actuator switching valve is disposed, the pressure oil supply side oil passage and the center bypass downstream side oil passage of the work attachment changeover valves in groups A and B are arranged. A boost relief valve and a pilot switching valve for tank communication are installed in series between the two, and the boost pilot pressure receiving portion of each boost relief valve and the pilot pressure receiving portion of each pilot switching valve are connected to the pilot of the straight-ahead valve. A hydraulic circuit for a hydraulic excavator, which is configured to communicate with a pressure receiving portion.