JPH0470429A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To improve safety of a construction machine and complete work by installing a traveling independent value on the discharge side of the first and second pumps, and also a pilot pressure selective conducting value which leads to the pilot chambers on its right and left and a traveling independent command value. CONSTITUTION:A traveling independent value 32 is installed so that it may lead to the discharge side pipe lines 45, 46 of the first and second pumps 7, 8 and the inlet ports 47, 48 of traveling valves 2L, 2R in groups A, B. Next, a pilot pressure selective command value 35 is provided on a pipe line which communicates a pilot chamber 33 of the traveling independent value 32 with shuttle values 17, 20, and a traveling independent command value 40 is provided on a pipe line which communicates a pilot pump 9 with a pilot chamber 34. When a working attachment is operated at the time of running a hydraulic shovel, the pressure oil from the first pump 7 is supplied to right and left motors in parallel, and the pressure oil from the second pump 8 is supplied to the other actuators.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates primarily to hydraulic circuits for construction machines such as hydraulic excavators.

BACKGROUND OF THE INVENTION FIG. 2 is a circuit diagram of a main part of a conventional hydraulic excavator. In the figure, IL and IR are left and right travel motors, 2L1
2R is a travel pilot switching valve that controls the left and right travel motors IL and IR, respectively, and 3.4 and 5.8 are pilots that respectively control various hydraulic actuators (not shown) installed in work attachments for hydraulic excavators, etc. Switching valve, 7 is the first pump, 8 is the second pump, 9
is a pilot pump. 10L and 10R are travel pilot switching valves 2Ls and 2R (hereinafter referred to as travel valves 2L and 2), respectively.
11.1 Left and right travel remote control valves that operate the
2 is the pilot valve 13 of the travel remote control valve 1OL, respectively.
．． 14 are pilot valves of the travel remote control valve 10R, 15, 18, 17 are shuttle valves for deriving travel pilot pressure, and 18°, 19, 20 are pilot switching valves 3, 4, 5.
21 is a group A shuttle valve for deriving working pilot pressure derived from a remote control valve (not shown) that operates 6;
The center bypass oil passages passing through the neutral positions of the travel valves 2t and t pilot switching valves 3 and 4 forming group B, 22 denote the center bypass oil passages of the travel valves 2Rs and pilot switching valves 5 and 6 forming group B, respectively. A center bypass oil passage passing through the neutral position, 23 and 24 are low pressure relief valves for setting negative control pressure, 25 and 26 are throttle parts, 27 is a straight forward travel valve, 28 is a pilot pressure selection conduction valve,
29 is an oil tank, code 1■, ◎-0.0-O9○-O
Each indicates the connection relationship of the pilot oil passage.

Next, a prior art hydraulic circuit will be described with reference to FIG. Various hydraulic actuators equipped on the hydraulic excavator are divided into two groups A and B, each of which is driven by a first and second pump 7.8. Further, the left and right traveling valves 2L and 2R are arranged in groups AB, and these and other pilot switching valves are connected in tandem, and the pilot switching valves of the above functions are connected in parallel. Also the first
A straight travel valve 27 is provided on the discharge side of the second pump 7.8, and the travel motor IL=IR and other pilot switching valves (3, 4
.
The pressure oil from the second pump 8 is supplied in parallel to the hydraulic actuators for other work attachments. Thereby, when the work attachment is operated while the hydraulic excavator is traveling, the hydraulic excavator can travel straight ahead without meandering. However, the vehicle speed of the hydraulic excavator in the above case is halved compared to the case where the excavator is running alone without operating the work attachments at the same time.

In the hydraulic circuit shown in FIG. 2, the negative control pressure generated at the center bypass most downstream side ratio of the pilot switching valve groups of groups A and B is transferred to the first and second pumps 7.8.
The pump discharge flow rate is adjusted by acting on regulators 30 and 31, respectively. Therefore, when the hydraulic system is working, when the negative control pressure decreases, the pump tilt angle is automatically adjusted and the pump discharge flow rate increases. Conversely, when the negative control pressure increases, the pump discharge flow rate decreases.

Problems to be Solved by the Invention In a hydraulic excavator equipped with a conventional hydraulic circuit, when a work attachment or the like (referred to as another actuator) is operated while the excavator is traveling, the traveling speed is reduced due to the switching operation of the straight traveling valve. Then, when the operation of the other actuators is stopped, the traveling speed suddenly increases again. As a result, the load may swing in a pendulum state when the suspended load is traveling, or may fall out of the packet while the ready-mixed concrete is being transported. Further, if a work attachment or the like is operated while the vehicle is traveling at a slow speed by adjusting the traveling control lever, the pump discharge flow rate increases and suddenly becomes faster for the same reason as above. However, when the operation of the work attachment is stopped, the traveling speed suddenly decreases. Additionally, if you drive while making fine adjustments to the work attachment, the work attachment will operate faster, and
If the above-mentioned traveling is stopped, the operating speed of the work attachment becomes slow.

As mentioned above, when operating travel and other actuators simultaneously, or repeatedly operating travel and other actuators individually, the travel speed and the operating speed of other actuators change each time, causing mutual interference.
It was dangerous to operate and also caused trouble during construction work.

The purpose of this invention is to solve the above-mentioned problems and provide a hydraulic circuit for construction machinery that is improved so that when traveling and other actuators are operated simultaneously or independently, the traveling speed and the operating speed of other actuators do not fluctuate each time. shall be.

Means for Solving the Problems The means of the present invention taken to solve the above-mentioned problems are as follows: (a) The first pump and the second pump are connected to the respective discharge side pipes, and each of the groups A and B is connected to the A traveling independent valve is provided so as to communicate with the inlet boat of the pilot switching valve in the front row, and a pipe that communicates the opening, and the pilot chamber on the straight traveling position side of the traveling independent valve with the traveling pilot pressure deriving means and the working pilot pressure deriving means. (c) A travel independent command valve is interposed in the conduit that communicates the pilot pump and the travel independent position side pilot chamber of the travel independent valve; (2) A travel independent valve; When the valve is in the neutral position, pressure oil from the first pump is directly supplied to group A, and pressure oil from the second pump is supplied to group B via the neutral position of the traveling independent valve. When other actuators such as work attachments are operated while the construction machine is traveling, the work pilot pressure is applied to the pilot chamber on the straight-travel position side of the travel independent valve through the pilot pressure selection conduction valve. The pressure oil from the second
When pressure oil from the pump is supplied to other actuators and the travel independent command valve is operated, the travel independent valve maintains the travel independent position regardless of whether travel and other actuators are operated simultaneously or independently. In addition, the pressure oil from the first pump is supplied in parallel to the left and right travel motors, and the pressure oil from the second pump is supplied to other actuators.

Operation a. When the independent travel valve is in the neutral position, the pressure oil from the first pump is directly supplied to group A, and the pressure oil from the second pump is supplied through the neutral position of the independent travel valve. It can be supplied to group B.

When other actuators such as work attachments are operated while the construction machine is traveling, the pressure from the first pump is reduced by applying the work pilot pressure to the pilot chamber on the straight travel position side of the travel independent valve via the pilot pressure selection conduction valve. By supplying oil to the left and right travel motors in parallel, pressure oil from the second pump can be supplied to other actuators.

C. When the travel independent command valve is operated, the travel independent valve can maintain the travel independent position regardless of whether travel and other actuators are operated simultaneously or independently, and the pressure oil from the first pump can be controlled from side to side. It is possible to supply pressure oil from the second pump in parallel to the traveling motor of the second pump, and to supply pressure oil from the second pump to other actuators.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram of essential parts of a hydraulic circuit according to the present invention. In the figure, the same reference numerals are given to the same components as in the prior art. 32 is an independent travel valve, 33 is a pilot chamber on the straight-travel position side of the travel independent valve 32, 34 is a pilot chamber on the travel independent position side, 35 is a pilot pressure selection conduction valve, and 36, 37, 38, and 39 are pilot opening/closing valves, respectively. 40 is a travel independent command valve, 41 is a solenoid of the travel independent command valve 40, 42 is an electric circuit, 43 is a switch in the electric circuit 42, and 44 is a power source.

Next, the configuration of the hydraulic circuit according to the present invention will be described with reference to FIG. The inlet boats 47 of the travel valves 2L23 in the front row of groups A and B, respectively, communicate with the discharge side pipes 45 and 48 of the first pump 7 and the second pump 8, respectively.
．． A traveling independent valve 32 was provided so as to communicate with the air conditioner 48. In addition, a pilot pressure selection conduit valve is provided in a conduit that communicates the pilot chamber 33 on the straight travel position side of the travel independent valve 32 with the travel pilot pressure deriving means (shuttle valve 17) and the working pilot pressure deriving means (shuttle valve 20). 3S was introduced. Further, an independent travel command valve 40 is interposed in a conduit that communicates the pilot pump 9 with the pilot chamber 34 on the independent travel position side of the independent travel valve 32. When the independent travel valve 32 is in the neutral position, the pressure oil from the first pump 7 is directly supplied to group A, and the pressure oil from the second pump 8 is supplied through the neutral position of the independent travel valve 32. When another actuator (not shown) such as a work attachment is operated while the hydraulic excavator is traveling, the work pilot pressure is supplied to group B via the pilot pressure selection conduction valve 35 and the travel independent valve 32. By acting on the pilot chamber 33 on the straight travel position side of the travel independent valve 32, the pressure oil from the first pump 7 is supplied in parallel to the left and right travel motors, and the pressure oil from the second pump 8 is supplied to the left and right travel motors in parallel. When the travel independent command valve 40 is operated, the travel independent valve 32 can maintain the travel independent position regardless of whether traveling and other actuators are operated simultaneously or independently. The pressure oil from the first pump 7 is supplied in parallel to the left and right travel motors, and the pressure oil from the second pump 8 is supplied to other actuators.

Next, the functions of the hydraulic circuit according to the present invention will be described. First, as a first case, a case will be described in which one of the other actuators, such as a work attachment, is operated while the left and right travel motors are stopped. Since the travel independent command valve 40 is not operated, no pilot pressure acts on the pilot chamber 34 of the travel independent valve 32 on the travel independent position side.

Further, since the pilot pressure selection conduction valve 35 remains in the cutoff oil path position, the working pilot pressure does not act on the pilot chamber 33 of the independent travel valve 32 on the straight travel position side. Therefore, the traveling independent valve 32 remains in the neutral position, so that the pressure oil from the first pump 7 is supplied to group A through line 45, and the pressure oil from the second pump 8 is supplied to group A through line 46, traveling Group B is supplied through an independent valve 32.

Next, as a second case, a case where only the left and right travel motors are operated independently will be described. Since the travel independent command valve 40 is not operated, no pilot pressure acts on the pilot chamber 34 of the travel independent valve 32 on the travel independent position side. Further, the traveling pilot pressure is derived from the shuttle service 17, and is derived from the pipe line 47,
48 and acts on the pilot chamber 49 of the Mylot pressure selection conduction valve 35 to switch the pilot pressure selection conduction valve 35 to the open oil passage position. However, since the working pyro-somatic pressure is not led out from the shuttle valve 20, no pilot pressure acts on the pilot chamber 33 on the straight-travel position side of the travel independent valve 32. Therefore, since the traveling independent valve 32 remains in the neutral position, in this case as well, the pressure oil from the first pump 7 and the second pump 8 is supplied to groups A and B, respectively.
supplied for.

Next, as a third case, a case where either the left or right travel motors or another actuator are operated simultaneously will be described. The running pilot pressure is led out from the shuttle valve 17 and acts on the pilot chamber 49 of the pilot pressure selection conduction valve 35 via lines 47 and 48. Pilot pressure selection conduction valve 3
5 is switched to the open oil passage position, the working pilot pressure derived from the shuttle valve 20 is changed to the open oil passage position of the pipe line 50, 51, the pilot pressure selection conduction valve 35, and the check valve 5.
2. Pilot chamber 3 of travel independent valve 32 via pipe 53
It acts on 3. On the other hand, since the independent travel command valve 40 is not operated, no pilot pressure acts on the pilot chamber 34 of the independent travel valve 32. The travel independent valve 32 is then switched from the neutral position to the straight travel position. Pressure oil from the first pump 7 passes through a conduit 45, one through a conduit 54, and the other through a traveling valve 2.
The other part branches off at the pipe line 45, passes through the pipe line 55, the straight travel position of the travel independent valve 32, and the pipe line 56, and is supplied to the travel valve 2R. Moreover, the pressure oil from the second pump 8 is
Conduit 46, straight traveling position of independent travel valve 32, conduit 57
One is supplied to the pilot switching valves 3 and 4 for the other actuators of group A via a check valve 58 and a pipe 59, and the other is branched at a pipe 57 and supplied to a check valve 60 and a pipe 61. After that, it is supplied to the pilot switching valves 5 and 6 for other actuators in group B.

That is, the first. Since pressure oil is supplied from the second pump 7.8 to the travel motor and other actuators separately, straight-line travel and operability of work attachments are guaranteed regardless of the respective loads on both of the above. Ru.

And number one. The pressure oil discharged from the second pump 7.8 can supplement each other in the constricted portion (62) passage of the independent travel valve 32 at the straight travel position T, depending on the opening degree and load of each pilot switching valve. In addition, if only the pilot switching valve for other actuators belonging to either group A or group B is operated while operating the travel valves 2L and 2R, the center bypass most downstream outlet on the opposite side (return to code, e) Pilot on-off valve 37 or 32 installed in
Since the second pump 8 is switched to the cutoff oil path position, the pressure oil from the second pump 8 is prevented from flowing into the oil tank 29.

Next, in the fourth case, when engaging in work where the running speed of the hydraulic excavator is kept at a constant speed regardless of whether other actuators are not operated or operated simultaneously, such as precision work or complicated work, it is necessary to switch Turn on 43. Since the solenoid 41 is energized, the travel independent command valve 40 is switched from the R position to the N position. The pilot pressure from the pilot pump 9 passes through lines 63, 64, 65, the null position of the travel independent command valve 40, and the line 66, 67, and then reaches the travel independent valve 3.
It acts on the pilot chamber 34 on the traveling independent position side of No. 2. At the same time, the pilot pressure branches off at a line 66, passes through a line 68, a check valve 69, lines 70, 71, and 53, and also acts on the pilot chamber 33 of the travel independent valve 32. The independent travel valve 32 is switched to the independent travel position by applying a bias force to the built-in spring 72 or the like. Pressure oil from the first pump 7 is supplied to the travel valve 2L from the pipe 45 through a pipe 54, and the other branched through the pipe 45 to the pipe 55.
, the traveling independent position of the traveling independent valve 32 passes through the conduit 56,
It is supplied to the travel valve 2R. Further, the pressure oil from the second pump 8 passes through the pipe 46, the independent travel position of the travel independent valve 32, and the pipe 57, and one passes through the check valve 58 and the pipe 59.
Pilot switching valve 3 for actuators other than group A,
4, and the other branched off at a pipe line 57, passes through a check valve 60 and a pipe line 61, and is supplied to the pilot switching valves 5 and 6 for other actuators in group B. That is, 1st. Pressure oil is supplied to the travel motor and other actuators independently from the second pumps 7.8. Therefore, in this case, the running speed of the hydraulic excavator remains unchanged with respect to the constant opening degrees of the running valves 2L and 2R, and stable running operation can be obtained.

Although the embodiments of the present invention have been described using a negative control type hydraulic circuit, the present invention can be similarly applied to a positive control type hydraulic circuit.

Effects of the Invention In a hydraulic excavator equipped with a conventional hydraulic circuit, when another actuator (for example, a work attachment, etc.) is operated while the excavator is running, the traveling speed is reduced by the switching operation of the straight-travel valve. Then, when the other actuator operations mentioned above are stopped, the traveling speed suddenly increases again. As a result, the load may swing in a pendulum state when the suspended load is traveling, or may fall out of the packet while the ready-mixed concrete is being transported. That is,
When traveling and operating other actuators simultaneously or independently repeatedly, the traveling speed and operating speed of other actuators change each time, which is dangerous for driving.
It also caused problems during construction work.

However, in the hydraulic circuit according to the present invention, an independent travel valve is provided on the discharge side of the first and second pumps, and a pilot pressure selection conduction valve and an independent travel command valve are provided which communicate with the left and right pilot chambers of the independent travel valve, respectively. Ta. As a result, when the hydraulic excavator repeatedly travels and operates other actuators at the same time, or travels and operates each actuator independently, the traveling speed and operating speed of other actuators do not change each time, which would cause mutual interference. Ta.

Therefore, in the construction machine equipped with the hydraulic circuit according to the present invention, when performing precise or complicated work, the hydraulic pumps for traveling and work attachment are completely divided into two systems, so that the hydraulic pumps for the above-mentioned work can be easily separated. Safety and work reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram according to the present invention, and FIG. 2 is a hydraulic circuit diagram of the prior art. IL, IR---1 travel motor 2t, 2R- (for travel) pilot switching valve 3, ~, 6
- (for other actuators) Pilot switching valve 7, 8 - 1st. Second pump 9
-11--Pilot pump 10L, 10F+
-Travel remote control valve 32-----One-travel independent valve 35
- Pilot pressure selection conduction valves 36, ~, 39 - Pilot on-off valves 40 - - Travel independent command valve and beyond
Up

Claims (1)

[Claims] (1) Various hydraulic actuators installed on construction machinery 2
They are divided into groups A and B, each driven by the first and second pumps, and the pilot switching valves for left and right travel are placed in each group, and the pilot switching valves for operating other actuators such as work attachments are placed in each group. They are connected in parallel, so that when the travel motor and other actuators are operated simultaneously, pressure oil from the first pump is supplied in parallel to the left and right travel motors, and pressure oil from the second pump is supplied to the other actuators. In the hydraulic circuit, the traveling independent valves are connected to the discharge side pipes of the first pump and the second pump, and to the inlet ports of the pilot switching valves in the front row of groups A and B, respectively. In addition, a pilot pressure selection communication valve is interposed in a conduit that communicates the straight-travel position side pilot chamber of the travel independent valve with the travel pilot pressure derivation means and the work pilot pressure derivation means, and the pilot pump and the travel An independent travel command valve is interposed in a pipe that communicates with the pilot chamber on the independent travel position side of the independent valve, and when the independent travel valve is in the neutral position, pressure oil from the first pump is directly supplied to group A. In addition, the pressure oil from the second pump is supplied to group B through the neutral position of the travel independent valve, and when other actuators such as work attachments are operated while the construction machine is traveling, the work pilot pressure is set to the above level. Pressure oil from the first pump is supplied in parallel to the left and right travel motors by acting on the pilot chamber on the straight travel position side of the travel independent valve via the pilot pressure selection conduction valve, and from the second pump. Pressure oil is supplied to other actuators, and when the travel independent command valve is operated, the travel independent valve can maintain the travel independent position even if the travel and other actuators are operated simultaneously or independently. A hydraulic circuit for construction machinery, characterized in that the pressure oil from the first pump is supplied in parallel to left and right travel motors, and the pressure oil from the second pump is supplied to other actuators. .