JPS5830855Y2 - Hydraulic excavator hydraulic circuit - Google Patents

Description

[Detailed description of the invention] This invention relates to a hydraulic circuit for a hydraulic excavator.

FIG. 1 is a front view of the hydraulic excavator, and FIG. 2 is a plan view thereof.

In the figure, 91 and 92 are crawlers, 93 is a revolving body rotatably supported by a traveling body having crawlers 91 and 92, 99 is a boom rotatably supported by the revolving body 93, and 98 is rotatable by a boom 99. 97 is arm 9
A bucket I is rotatably supported at 8, 80 and 90 are travel hydraulic motors for driving crawlers 91 and 92, 50 is a swing hydraulic motor for swinging a swing body 93, and 70 is a swing hydraulic motor for rotating a boom 99. 40 is an arm hydraulic cylinder for rotating the arm 98; 60 is a boom hydraulic cylinder for rotating the arm 98;
Reference numeral 4 indicates a packet hydraulic cylinder for rotating the packet 97, and 4 indicates a prime mover attached to the revolving body 93. This prime mover 4 drives actuators such as the arm hydraulic cylinder 40.

FIG. 3 is a diagram showing a hydraulic circuit of a conventional hydraulic excavator.

In the figure, 1 and 2 are pumps connected to the prime mover 4, and 10
．． 20 is a switching valve group connected to the pumps 1 and 2, respectively, 11 is a left traveling switching valve connected to a traveling hydraulic motor 80, 12 is a bucket 1 to switching valve connected to a packet hydraulic cylinder 60, and 13 is a boom hydraulic pressure The boom switching valve is connected to the cylinder 70, and the switching valves 11 to 13 are connected in parallel.

21 is a swing switching valve connected to the swing hydraulic motor 50;
4 is a right travel switching valve connected to the travel hydraulic motor 90;
3 is an arm switching valve connected to the arm hydraulic cylinder 40, and 22 is a boom switching valve connected to the boom hydraulic cylinder 70. The boom switching valve 22 and boom switching valve 13 can be operated in conjunction with each other. ing.

Moreover, the switching valves 21 to 24 are connected in parallel.

100 is a tank, A and B are relief valves connected to the pumps 1 and 2, respectively, and E is a throttle provided in a pipe S connecting the ground 8 switching valve 23 and the arm hydraulic cylinder 40.

Note that the boom hydraulic cylinder 70, travel hydraulic motor 80.
90 is omitted.

In this hydraulic circuit, each switching valve 11-13, 21-2
4 is not operated, the oil discharged from the pumps 1 and 2 is returned to the tank 100 through the pipes a, e, and pipes f, respectively.

If only the arm switching valve 23 is operated from this state, the oil discharged from the pump 2 will flow through the pipe b, the arm switching valve 23, and the pipe S.
Or it is supplied to the arm hydraulic cylinder 40 via t.

Furthermore, when only the swing switching valve 21 is operated, the oil discharged from the pump 2 is transferred to the pipe b, the swing switching valve 21. It is supplied to the swing hydraulic motor 50 via pipe m or n.

In these cases, the oil discharged from the pump 2 is supplied to only one actuator, so the pump 2 can supply pressure oil at a pressure that corresponds to the load of each actuator.

Next, when the swing switching valve 21 and the arm switching valve 23 are operated simultaneously, pressure oil is supplied to the motor 50 and the cylinder 40, but the swing switching valve 21 and the arm switching valve 23 are connected to parallel connection pipes. Since they are connected in parallel by path 2, the division ratio of the pressure oil flow rate to each actuator is determined by the magnitude of the load on each actuator.

For example, if the load on the cylinder 40 is smaller than the load on the motor 50, the pressure oil of the pump 2 will flow only to the cylinder 40, which has a lower operating pressure, and the motor 50 will be held at the operating pressure of the cylinder 40. This causes the phenomenon that the motor 50 does not operate.

The same applies to the opposite case. This is the first problem with this hydraulic circuit.

The second problem is that when the swing switching valve 21 and the arm switching valve 23 are operated at the same time, it is impossible to apply sufficient force to one of the actuators.

For example, if the motor 50 applies a turning force to the packet 97,
When excavating by moving the arm 98 while pressing the arm against the wall, the cylinder 40 operates because the rotation movement is blocked, but the rotation switching valve 21 and the arm switching valve 23
Since the pump 2 is connected in parallel with the pump 2, the discharge pressure of the pump 2 at this time is determined by the load on the cylinder 40. If the load on the cylinder 40 is large, the discharge pressure of the pump 2 will be high and the turning force will be large. If the load on the cylinder 40 is small, the discharge pressure of the pump 2 will be low and it will not be possible to generate enough force when pressing by turning.

The third problem is that the horsepower of the prime mover 4 cannot be used effectively.

That is, in the hydraulic circuit shown in FIG. 3, when the discharge pressure of the pump 1.2 reaches the set pressure of the relief valves A and B, the horsepower of the prime mover 4 is fully used. When each actuator of a switching valve group connected to one pump is operated in a Chinese-German or combined manner, only half of the horsepower of the prime mover 4 can be used with one pump, so the horsepower of the prime mover 4 cannot be used effectively.

The fourth problem is that the speed of the arm hydraulic cylinder 40 cannot be increased.

That is, the arm hydraulic cylinder 40 needs to have a large cylinder inner diameter in order to increase the excavation force, and it is necessary to increase the cylinder stroke in order to increase the movable range of the arm 98, so one pump is required. In the hydraulic circuit shown in FIG. 3, which drives the arm hydraulic cylinder 40, the speed of the arm hydraulic cylinder 40 cannot be increased, resulting in poor workability.

FIG. 4 is a diagram showing a hydraulic circuit of another conventional hydraulic excavator.

This hydraulic circuit includes an arm speed increasing switching valve 1 connected in tandem with the boom switching valve 13 downstream of the boom switching valve 13.
4 is additionally provided, the arm speed increasing switching valve 14 and the arm switching valve 23 are interlocked by a double pulling mechanism It is connected to paths s and t.

In this hydraulic circuit, when the switching valve 14.23 is operated by the double pull mechanism X, the pressure oil of the pump 1 is transferred to the pipe a, the switching valve 14.23. The cylinder 40 is supplied via the pipe U or V, and the pressure oil of the pump 2 is supplied to the cylinder 40 via the pipe b, the switching valve 23, and the pipe S or t.

Therefore, since the cylinder 40 operates at twice the speed as in the case of the hydraulic circuit shown in FIG. 3, the prime mover 4 also performs twice the work, and the third and fourth problems mentioned above are solved. There is.

However, since the switching valves 21 and 23 are connected in parallel, when the cylinder 40 and motor 50 are operated at the same time, only the actuator with lower operating pressure is operated, the other actuator is not operated, and one actuator is not operated. The operating pressure cannot be increased.

That is, the first and second problems mentioned above have not been solved.

FIG. 5 is a diagram showing a hydraulic circuit of another conventional hydraulic excavator.

In the figure, 3 is a pump connected to the prime mover 4, 30 is a switching valve group connected to the pump 3, and 31 is a swing switching valve connected to a swing hydraulic motor 50. This corresponds to the swing switching valve 21.

32 is an arm speed increasing switching valve connected to the arm hydraulic cylinder 40, and the arm speed increasing switching valve 32 corresponds to the arm speed increasing switching valve 14 in FIG.

The swing switching valve 31 and the arm speed increasing switching valve 32 are connected in tandem, and the arm speed increasing switching valve 32 and the arm switching valve 23 are interlocked by a double pulling mechanism Y.

Further, D is a relief valve connected to the pump 3.

In this hydraulic circuit, the switching valves 23, 32 and 31
When these are operated simultaneously, the pressure oil of the pump 2 is supplied to the cylinder 40 via the pipe b, the switching valve 23, and the pipe S or t, while the pressure oil of the pump 3 is supplied to the cylinder 40 via the pipe C1, the switching valve 31, and the pipe m. or n, the entire amount of discharge pressure oil is supplied to the motor 50.

In this case, the switching valve 32 allows only return oil from the cylinder 40 to pass through the pipe U or V, and serves only to reduce the back pressure of the cylinder 40.

In this way, the cylinder 40 and the motor 50 are completely independently controlled when operated simultaneously, so only the actuator with the lower operating pressure is not operated, and the operating pressure of one actuator can be increased. .

That is, the above-mentioned 1. The second problem has been resolved.

However, when the cylinder 40 and motor 50 are operated simultaneously, the speed of the cylinder 40 (arm 98) cannot be increased.

Furthermore, if the horsepower of the prime mover 4 is made the same as in the circuit shown in Figure 3, it is necessary to reduce the capacity of pumps 1 and 2 or lower the set pressure of relief valves A and B by the amount that pump 3 is provided. .

For this reason, the output of each actuator connected to pump 1.2 must be lower than in the circuit of FIG. 3.

This idea was made in order to solve the above-mentioned problems. When the swing hydraulic motor and the arm hydraulic cylinder are operated simultaneously, the swing movement can be performed even when the load on the arm is small, and it is possible to To provide a hydraulic circuit for a hydraulic excavator that can obtain a required turning force of a certain level or more without any problems, can effectively utilize the horsepower of the prime mover, and has a high speed when the arm is operated independently. purpose.

In order to achieve this purpose, in this invention, a plurality of pumps driven by one prime mover are provided, a switching valve group having a plurality of switching valves is connected to each pump, and each switching valve is connected to each of the hydraulic excavators. In the hydraulic circuit of the hydraulic excavator connected to the actuator, an additional pump driven by the above-mentioned one prime mover is additionally provided, the switching valves of one switching valve group are connected in parallel, and the switching valve of the most downstream of the switching valve group is connected in parallel. A valve is connected to the first actuator, a second switching valve from the most downstream is connected to the second actuator, and an additional switching valve that is switched to the operating position when the second actuator is activated is connected to the additional pump. A priority switching valve that switches to the operating position when the first actuator is activated and has a throttle in a circuit connected to the second actuator is connected to the upstream side of the additional switching valve; ．． When actuating the second actuator, the pressure oil of the additional pump is returned to the tank;
When actuator 1 is operated, the pressure oil of the additional pump is supplied to the second actuator, and the first actuator of ±7 is supplied to the second actuator. When the second actuator is activated at the same time, the pressurized oil of the additional pump described in Section 1. The second actuator is configured to be supplied with the second actuator.

FIG. 6 is a diagram showing the hydraulic circuit of the hydraulic excavator according to this invention.

In the figure, 3a is an additional pump additionally connected to the prime mover 4, 30a is an additional switching valve group connected to the additional pump 3a, and 32a is an additional switching valve.
The switching is controlled by the differential pressure before and after the throttle 1).

31a is a priority switching valve connected to the upstream side of the additional switching valve 32a, and the priority switching valve 31a is connected to the swing hydraulic motor 50.
A circuit connected to the switching valve 23 (cylinder 40) of the priority switching valve 31a through switching control by the operating pressure of the motor 50 via the shaft valve F provided between the pipes m and n of the circuit. An aperture K is provided at t+-.

Moreover, the switching valves 21 to 24 of the switching valve group 20 are connected in parallel by the parallel pipe line 2, and the switching valve group 2
11. A swing switching valve 21 is connected to the lowest flow of 0. The day 18 switching valve 23 is connected to the second from the most downstream position.

A check valve J is provided in the parallel circuit 2 that connects the switching valve 21 and the switching valve 23, and a parallel pipe Z connects the switching valve 23 and the boom speed increasing switching valve 22 located upstream thereof. A check valve G is provided.

Furthermore, 41 is a switching valve that operates using the additional pressure of the hydraulic pressure of the pipes a, l) as a pilot pressure, 42 is an unload valve connected to the additional pump 3a, and the unload valve 42 is the switching valve 4.
Activates when 1 is activated.

Next, the operation will be explained.

First, when the switching valves 11-13 and 21-24 are not operated, the pressure oil of the pumps 1, 2, 3a is returned to the tank 100 via the switching valve groups 10, 20, 30a, respectively.

Next, when only the switching valve 23 is operated, the pressure oil of the pump 2 is sent to the switching valve 23 via the pipe S, and the pressure oil is sent to the switching valve 23 via the pipe S or t.
It is supplied to the cylinder 40 through the.

In this case, since a differential pressure is generated before and after the throttle E due to the operation of the cylinder 40, the additional switching valve 32a is switched to a position other than the neutral position, that is, the operating position, and the pressure oil of the pump 3a is switched via the pipe p. The oil is sent to the valve 23 and joins with the pressure oil of the pump 2, thereby increasing the speed of the cylinder 40.

Note that the additional switching valve 32 a is a three-position switching valve with the same structure in the left and right positions, and the pipe C and the pipe P are connected regardless of whether it is switched to the left or right position. Therefore, the expansion and contraction of the cylinder 40 Both image operations are accelerated by the pressure oil of the pump 3a.

Further, while the additional switching valve 32a is controlled by the movement of the cylinder 40, the switching valve 23 returns to the neutral position and the movement of the cylinder 40 stops, or the relief valve B is activated and the movement of the cylinder 40 slows down. In this case, the differential pressure before and after the curvature E becomes zero or becomes a small differential pressure that falls within the control range of the spring force of the additional switching valve 32a, and the additional switching valve 32a returns to the neutral position, and the pump 3a The pressure oil is in pipe g
Return to tank 100 via .

Next, a case will be described in which only the switching valve 21 is operated.

In this case, the pressure oil of the pump 2 is sent to the switching valve 21 via the pipe line 1, and is supplied to the motor 50 via the pipe line 1n or n.

Then, the operating pressure of the motor 50 is sent to the priority switching valve 31a via the shaft valve F and the pilot valve 1-pipe q,
Priority switching valve 31a is sent to priority switching valve 31a.
is switched to the right position, that is, the operating position.

However, the additional switching valve 32a is in the neutral position when the tank 100
The additional switching valve 32 is connected to the pipe g that leads oil to the
The pressure oil of the pump 3a is returned to the tank 100 unless the pump 3a is operated to either the left or right position, that is, the operating position, that is, unless the cylinder 40 is operated.

In this way, when the arm is operated alone, the speed of the cylinder 40 is increased by the pressure oil of the pump 3a, but when the arm is operated alone, the rotation speed is the same as in the conventional hydraulic circuit.

Note that the pressure oil sent to the switching valves 21 and 23 via the pipe O9p is not controlled by the switching valves 22 and 22 because of the check valves J and G.
. The flow rate does not change.

Next, when the switching valve 21 and the switching valve 23 are operated simultaneously, the pressure oil of the pump 2 is transferred to the motor 50 and the cylinder 40.
supplied to

Then, the priority switching valve 31 a and the additional switching valve 32 a are switched to the operating position, so the pipe C and the pipe P are connected via the throttle K, and the pipe C and the pipe O are connected to each other through the throttle. The pipes p and 0 are connected in parallel with the pipe C.

Therefore, when the operating pressure of the motor 50 is low, the pressure oil of the pump 3a flows to the conduit O with low resistance, and the motor 50
is supplied to

When the operating pressure of the motor 50 becomes greater than the pressure corresponding to the resistance of the throttle K, the speed of the cylinder 40 can be increased using the pressure oil of the pump 3a while holding the motor 50 at a pressure corresponding to the resistance of the throttle K. can.

Therefore, digging can be performed by operating the arm 98 while pressing the packet 97 against the wall surface.

Next, effective use of the horsepower of the prime mover will be explained.

When the pressure obtained by adding the discharge pressures of pumps 1 and 2 reaches a predetermined value, the switching valve 41 is activated and the pressure oil of pumps 1 and 2 is transferred to the pipe l.
1. l 2. Switching valve 41. Since the unload valve 42 is operated through the pipe 1, the pressure oil of the pump 3a is transferred to the pipe d,
It returns to the tank 100 via the unload valve 42 and the pipeline, and the pump 3a is unloaded.

Further, when the pressure that is the sum of the discharge pressures of pumps 1 and 2 is less than a predetermined value, the switching valve 41 does not operate, so the unloading valve 42 does not operate, and the pressure oil of the pump 3a is transferred to the switching valve group 30. supplied to a.

Therefore, each actuator connected to the pumps 1 and 2 can use the pressure oil of the pump 3a without degrading the conventional function and if there is a surplus in the output of the prime mover 4. Conventional functions can be improved, and the motor output can be used more effectively than in conventional circuits.

For example, if the discharge flow rate of pumps 1 and 2 is 100 l/m
in, the discharge pressure of pumps 1 and 2 is 100 kg/cm2
When the horsepower of the prime mover 4 is full, the discharge flow rate is 501/min and the discharge pressure is 100 kg/min when the unload valve 42 etc. are not provided as in a conventional hydraulic circuit.
When adding cm2 pump 3a, pumps 1 and 2
It is necessary to reduce the discharge pressure of the pump 1 to 75 kg/cm2, but when the unload valve 42 etc. is provided and the set pressure of the switching valve 41 is set to 150 kg/cm2, the discharge pressure of the pump 1,
If the discharge pressure of pump 3a (set pressure of relief valves A and B) can be kept at 100 kg/cm2 as before, and the added pressure of the discharge pressures of pumps 1 and 2 does not reach 150 kg/cm2, then Pressure oil can be used effectively.

In the hydraulic circuit shown in FIG. 6, when the sum of the discharge pressures of pumps 1 and 2 exceeds a predetermined value, pump 3
Although the pump 3a is unloaded, the pump 3a may be unloaded when the discharge pressure of the pump 1 or the pump 2 exceeds a predetermined value, as shown in FIGS. 7 and 8.

In this case, the circuit becomes simpler than the hydraulic circuit shown in FIG.

Further, by the operation of the unload valve 42, the cylinder 40,
Although the speed of the motor 50 changes, the operation of the unload valve 42 occurs near the horsepower limit of the prime mover 4, so the operator senses the operation of the unload valve 42 by the change in the sound generated by the prime mover 4 corresponding to the load. and can be appropriately controlled.

In addition, in the above-mentioned embodiment, the case was explained in which the pump 3a was added to the two pumps 1 and 2.
It goes without saying that it is also possible to attach a.

Further, in the above embodiment, the arm hydraulic cylinder 40 and the swing hydraulic motor 50 have been described, but similar effects can be obtained with other actuators.

Furthermore, in the above embodiment, an example was described in which the switching valves 11 to 13 of the switching valve group 10 were connected in parallel, but they may be connected in series or in tandem.

As explained above, in the hydraulic circuit of the hydraulic excavator according to this invention, when the swing hydraulic motor and the arm hydraulic cylinder are operated simultaneously, the swing operation is performed even when the load on the arm is small, and the load on the arm is Regardless,
A required turning force above a certain level can be obtained, the horsepower of the prime mover can be used effectively, and the speed when the arm is operated independently is high.

In this way, the effects of this invention are remarkable.

[Brief explanation of the drawing]

Figure 1 is a front view of a hydraulic excavator, Figure 2 is a plan view, Figures 3 to 5 are diagrams each showing a hydraulic circuit of a conventional hydraulic excavator, and Figure 6 is a diagram showing a hydraulic circuit according to this invention. , 7 and 8 are diagrams showing a part of the hydraulic circuit of another hydraulic excavator according to this invention, respectively. 1.2...Pump, 3a...Additional pump, 4...Motor, 10.20...Switching valve group, 21... Swivel switching valve, 23...
...Arm switching valve, 30 a...Additional switching valve group, 31 a...Priority switching valve, 32
a...Additional switching valve, 40...Arm hydraulic cylinder, 41...Switching valve, 42...
・Unload valve, 50...Swivel hydraulic motor, E
, K... Throttle, F... Shuttle valve, G
, J...Check valve.

Claims (5)

[Scope of utility model registration request] (1) Provide multiple pumps driven by one prime mover,
In the hydraulic circuit of a hydraulic excavator in which a switching valve group having a plurality of switching valves is connected to each pump, and each of the switching valves is connected to each actuator of the hydraulic excavator, an additional pump driven by the one prime mover is added. The switching valves of one switching valve group are connected in parallel, the most downstream switching valve of the switching valve group is connected to the first actuator, and the second switching valve from the most downstream is connected to the second actuator. An additional switching valve is connected to the additional pump and is switched to the operating position when the second actuator is activated, and an additional switching valve is connected to the additional pump, and the additional switching valve is connected to the upstream side of the additional switching valve and is switched to the operating position when the first actuator is activated. When a priority switching valve having a throttle is connected to the circuit connected to the second actuator and the first actuator is operated, the pressure oil of the additional pump is returned to the tank, and the second actuator is operated. When the 1st additional pump operates, the pressure oil of the 1st additional pump is supplied to the 2nd actuator, and when the 14th and 2nd actuators are operated simultaneously, the pressure oil of the additional pump is supplied to the 1st and 12th actuators. A hydraulic circuit for a hydraulic excavator, characterized in that the hydraulic circuit is configured to be supplied to the hydraulic circuit. (2) Hydraulic IE'jl path of a hydraulic excavator according to claim 1, wherein the first actuator is a swing hydraulic motor, and the second actuator is a Day 18 hydraulic cylinder. . (3) A parallel pipe connecting the first actuator switching valve to the second actuator switching valve, and a parallel pipe connecting the second actuator switching valve and the switching valve located upstream thereof. Claim 1 or 2 of the utility model registration claim characterized in that a check valve is provided in the road.
Hydraulic circuit of the hydraulic excavator described in section. (4) A restriction is provided in the pressure oil supply line of the second actuator, and switching control of the additional switching valve is controlled by a pressure difference before and after the restriction, A hydraulic circuit for a hydraulic excavator according to item 2 or 3. (5) Utility model registration claims 1 and 2, characterized in that an unload valve is provided to unload the additional pump when the discharge pressure of the pump exceeds a predetermined value.
A hydraulic circuit for a hydraulic excavator according to item 1, 3 or 4.