JPH0464378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hydraulic circuit for a construction machine having a straight-travel function.

Prior Art A conventional hydraulic circuit is shown in Fig. 2, in which 1 is a swing motor, 2 and 3 are left and right travel motors, and 4, 5, and 6 are boom cylinders for work attachments. , bucket cylinder, arm cylinder, 7, 8, 9 are the first, second and third pumps, 10 is a pilot pump for remote control (hereinafter referred to as remote control), 11 is a swing valve, 12 _L , 12 _R are left and right pumps. Traveling valves 13, 14, and 15 are cylinder valves 1 and 15, respectively.
6 is an oil tank, and 21 is a remote control valve for turning.
In FIG. 2, all the switching valves are in the neutral position, but the left and right travel valves 12 _L and 12 _R are operated by direct operation, and the other switching valves are operated by remote control.

Next, the operating function of the prior art hydraulic circuit shown in FIG. 2 will be described. Among the various hydraulic actuators installed in the construction machine, the actuators other than the swing motor 1 are arranged in parallel and divided into two groups A and B. Therefore, when operating any one of the left traveling motor 2, boom cylinder 4, and bucket cylinder 5 belonging to group A, by switching the left traveling valve _12L and either of the cylinder valves 13, 14, The hydraulic actuator operates because the pressure oil discharged from the first pump 7 is supplied from the switching valve through the oil passage 44. In addition, when operating either the right travel motor 3 or the arm cylinder 6 belonging to group B, the right travel valve 12 _R ,
When one of the cylinder valves 15 is switched, the pressure oil discharged from the second pump 8 is supplied from the switching valve via the oil passage 45, so that the hydraulic actuator is operated. Next, the case of operating the swing motor 1 will be explained. Operation lever 46 of the remote control valve 21 for turning
When the pilot pump 10 is operated to the A or B position, the pilot pressure oil from the pilot pump 10 flows through the oil passage 47, the pilot valve 48 or 49, and the pilot oil passage 50.
Or it acts on the pilot pressure receiving part 29 or 30 of the swivel valve 11 via 51. Then, since the swing valve 11 is switched, the pressure oil discharged from the third pump 9 is supplied to the swing motor 1 via the oil passage 52 and the swing valve 11, causing the swing motor 1 to rotate forward or reverse.

Further, another example of the prior art is a hydraulic circuit having a straight traveling function as shown in FIG. 3, but since it is a two-pump type having a first and second pump, it does not include a third pump. For this purpose, the swivel motor 1 is arranged in group A. Therefore, the various actuators other than the left and right travel motors 2 and 3 are
Switching valves 11, 13, 14, by remote control valve operation.
15. In the figure, an oil passage 5 that communicates the left travel motor 2 and the left travel valve _12L .
3, 54, an on-off valve 55 in parallel with the left travel motor 2
is provided, and when the on-off valve 55 stops the left traveling motor 2, the pilot oil passage 5 is connected to the remote control valves 21 and 24.
When the left travel motor 2 is in operation, the pilot oil passage 56 is shut off, and when the left travel motor 2 is in operation, the pilot oil passage 56 is opened. Therefore, when only the left and right travel valves 12 _L and 12 _R are operated, discharge pressure oil is sent to the left and right travel motors 2 and 3 from the first and second pumps 7 and 8. However, if one of the remote control valves 21 or 24 is operated while the left and right travel valves _12L and _12R are being operated simultaneously, the pilot pressure oil from the pilot pump 10 will flow through the pilot oil passage 56, the on-off valve 55, and the oil passage. 57 and acts on the pilot pressure receiving portion 59 of the straight travel valve 58. For this purpose, the straight travel valve 58 is switched, and the pressure oil discharged from the second pump 7 is transferred to the switching valve 11,
15, 13, and 14, and the pressure oil discharged from the second pump 8 is sent to the left and right travel motors 2 and 3 in parallel. Therefore, the construction machine having this hydraulic circuit travels straight ahead.

Problems to be Solved by the Invention When the construction machine of the prior art shown in FIG. 2 is caused to travel straight ahead, the left travel motor in group A and the right travel motor in group B are rotated at the same time. However, A to which the left travel motor belongs
The hydraulic circuit is configured such that the group is supplied with discharge pressure oil from the first pump, and the B group to which the right travel motor belongs is supplied with discharge pressure oil from the second pump.
Therefore, in groups A and B, the left and right travel motors and other work attachment actuators are connected in parallel. For this reason, when any other actuator is activated while the construction machine is traveling straight, part of the supplied hydraulic oil is used through the parallel oil path that communicates with that actuator. The amount of oil supplied to the motor decreases. Therefore, the rotational speed of the traveling motor on the side where the amount of supplied oil is decreased is reduced, and the construction machine begins to travel in a curved direction.

Next, problems with conventional construction machines having a straight-travel function as shown in FIG. 3 will be described. When traveling straight in this hydraulic circuit, when only the left and right travel motors are operated and the other actuators are not operated, discharge pressure oil is supplied to the left travel motor from the first pump and to the right travel motor from the second pump. Ru. However, when any other actuator is operated while traveling straight, the straight travel valve is switched, so the discharge oil passage of the second pump communicates with the left and right travel valves in parallel, and the discharge oil passage of the first pump communicates with other actuator switching valves. For this reason, construction machinery equipped with this circuit can operate the other actuators simultaneously while traveling straight.
Continue driving straight on flat, normal soil. However, if this construction machine is located on soft ground, for example, and a large load is applied to the travel motor on either the left or right side, and a small load is applied to the travel motor on the other side,
The traveling motor on the side with the larger load stopped rotating, making it difficult to travel, which was a problem.

Means for Solving the Problem The means of the present invention taken to solve the above problem are as follows: (a) Among the various hydraulic actuators installed in the construction machine, other actuators except the swing motor are divided into two groups A and B. A circuit is constructed in which group A is operated by the first pump, group B is operated by the second pump, and the swing motor is operated by the third pump via each switching valve, and the left and right travel valves are operated by the groups A and B, respectively. on the most upstream side and in tandem with other actuator switching valves on the downstream side; (b) Also, an on-off valve is provided in each of the two oil passages branching from the middle of the oil passage between the third pump and the swivel valve; (c) An electric circuit having a limit switch that closes the electric circuit in conjunction with the switching operation of the left and right travel valves is provided, and (d) an electromagnetic on-off valve that can be switched by a solenoid is installed at the outlet of the shuttle valve for deriving the pilot pressure of various remote control valves. (e) Connect the pilot pressure receiving part of one of the two on-off valves and the pilot pressure receiving part of the swivel valve via a shuttle valve, and connect the pilot pressure receiving part to the shuttle valve, It is connected to the shuttle valve on the outlet side of various remote control valves via an electromagnetic on-off valve, so that the tank communication oil passage on the discharge side of the third pump can be switched on and off. Each of the valves is connected to a parallel oil passage port, and the pilot pressure receiving part of the on-off valve is connected to the outlet side of the electromagnetic on-off valve, so that the oil passage can be switched on and off.

Operation (a) When only the left and right traveling valves are switched and the other remote control valves for actuator operation are not operated, no pilot pressure is derived from those remote control valves. For this reason, the on-off valve in this circuit does not switch, so the left and right travel motors are supplied with discharge pressure oil from the first and second pumps, respectively.

(b) When the left/right travel valve and the swing remote control valve are operated at the same time, the pilot pressure from the swing remote control valve acts on one of the on-off valves and switches the tank communication path branched from the third pump discharge oil path. Close. For this purpose, the swing motor is supplied with discharge pressure oil from the third pump and rotates.
On the other hand, in conjunction with the switching operation of the left and right travel valves, the limit switch in the electric circuit closes the electric circuit. The electric circuit is then energized, and the solenoid acts on the electromagnetic on-off valve to switch the electromagnetic on-off valve to the oil passage open position. However, since the remote control valves for the work actuators are not operated, no pilot pressure is derived from each remote control valve. Therefore, the left and right travel motors are supplied with discharge pressure oil from the first and second pumps, respectively.

C. When either the left/right travel valve or the remote control valve for operating the work actuator is operated simultaneously, the limit switch closes the electric circuit in conjunction with the switching operation of the left/right travel valve as described in item (B) above, so the solenoid operates as an electromagnetic on/off valve. and switches the solenoid on-off valve to the oil passage open position. For this purpose, the pilot pressure derived from any of the remote control valves for operating the work actuator will cause the on-off valve provided in the middle of the tank communication oil passage on the third pump discharge side to be in the oil passage closed position, and from the third pump discharge side. The on-off valves provided in the middle of the oil passages communicating with the parallel oil passages of the various switching valves are switched to the oil passage open position. For this purpose, the left and right travel motors are supplied with discharge pressure oil from the first and second pumps, respectively, and the work actuator that communicates with the operated remote control valve is supplied with discharge pressure oil from the third pump.

D. If the left/right travel valve, the swing remote control valve, and any other switching valve remote control valve are operated at the same time, due to the reasons stated in items (b) and (c) above, the left and right travel motors will be operated from the first and second pumps, respectively.
The swing motor and operated work actuator cause delivery pressure oil to be supplied from the third pump.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on FIG. In the figure, 1 is a swing motor;
2 and 3 are left and right travel motors, 4, 5 and 6 are work actuator cylinders, 7 is a first pump, 8 is a second pump, 9 is a third pump, 10 is a pilot pump, 11 is a swivel valve, 12 _L , 12 _R are left and right traveling valves, 13, 14, 15 are cylinder valves, 16 is an oil tank, 17 is an electric circuit, 18 is an electromagnetic shut-off valve, 19 and 20 are shut-off valves, 21
are remote control valves for operating the swing motor 1, 22, 23,
24 is a remote control valve for operating the cylinders 13, 14, 15. This hydraulic circuit divides the actuators other than the swing motor 1 into two groups A and B, and places the left and right traveling valves 12 _L and 12 _R on the most upstream side of groups A and B, respectively, and the other actuators on the downstream side. It is installed in tandem with the actuator switching valve. Then, on-off valves 19 are provided in oil passages 26 and 27 branched from the middle of the oil passage 25 between the third pump 9 and the swing valve 11, respectively.
20 was established. Further, an electric circuit 17 is provided which has a limit switch 40 that closes the electric circuit in conjunction with the switching operation of the left and right travel valves 12 _L and 12 _R. , 23, 24 on the outlet side of the pilot pressure deriving shuttle valve 33. On the other hand, the pilot pressure receiving section 28 of the on-off valve 19 and the pilot pressure receiving section 29, 3 of the swing valve 11
0 through the shuttle valves 31 and 32, and the pilot pressure receiving part 28 is connected to the shuttle valve 3.
1. The above-mentioned shuttle valve 33 via the electromagnetic on-off valve 18
connected to. Also, the on-off valve 20 is a check valve 34,
35 to the parallel oil passages 36, 37, and 38 of the switching valves 13, 14, and 15, respectively, and the pilot pressure receiving portion 43 of the on-off valve 20 was connected to the outlet side of the electromagnetic on-off valve 18.

The hydraulic circuit of the present invention is constructed as described above, and its operating functions will now be described. First of all
Next, a case will be described in which only the left and right travel motors 2 and 3 are operated. In this hydraulic circuit, actuators other than the swing motor 1 among various hydraulic actuators are arranged in parallel and divided into two groups A and B. When no pilot pressure acts on the on-off valves 19 and 20, the actuators are divided into two groups A and B. B is connected to the first and second pumps 7 and 8, respectively, and the swing motor 1.
The discharge pressure oil is supplied from the third pump 9. In the first case, the left and right travel valves _12L ,
Since only _12R is switched and operated, the limit switch 40 closes the circuit in conjunction with this. For this purpose, the electric circuit 17 is energized by the DC power supply 42, and the solenoid 41 in the electric circuit 17 is operated to act on the electromagnetic actuating portion 39 of the electromagnetic on-off valve 18. Therefore, the electromagnetic on-off valve 18 is switched from the oil passage closed position to the oil passage open position, but since the work actuator remote control valves 22, 23, and 24 are not operated, the pilot pressure from the pilot pump 10 is not derived. Furthermore, since the remote control valve for turning 21 is not operated, the on-off valves 19 and 20 do not perform switching operations. Therefore, the on-off valve 19 is in the oil passage open position, and the on-off valve 20 is in the oil passage closed position, so the third pump 9
The discharged pressure oil returns to the oil tank 16 via the oil passage 25 and the on-off valve 19. Therefore, the left and right traveling valve 12
When only _L and _12R are operated, the pressure oil discharged from the first and second pumps 7 and 8 is supplied to the left and right travel motors 2 and 3 via the left and right travel valves _12L and _12R , respectively.

Second, a case will be described in which the left and right travel motors 2, 3 and the swing motor 1 are operated simultaneously. When the operation lever 60 of the swing remote control valve 21 is operated to the A position or the B position, the pilot pressure oil from the pilot pump 10 is transferred to the pilot valve 61 or 6.
2. Acting on the pilot pressure receiving portion 29 or 30 of the swivel valve 11 via the pilot oil passage 63 or 64 to switch the swivel valve 11;
It acts on the pilot pressure receiving portion 28 of the on-off valve 19 via the shuttle valves 32 and 31. For this purpose, the on-off valve 19 is operated to close the tank communication oil passage 26 on the discharge side of the third pump 9. On the other hand, since no pilot pressure acts on the pilot pressure receiving portion 43 of the on-off valve 20, the on-off valve 20 remains in the oil passage closed position. For this purpose, the discharge pressure oil from the first and second pumps 7 and 8 is supplied to the left and right travel motors 2 and 3 via left and right travel valves 12 _L and 12 _R , respectively, and to the third pump 9.
Pressure oil discharged from is supplied to the swing motor 1 via the swing valve 11.

Third, left and right travel motors 2, 3, swing motor 1
A case will be described in which the cylinders (any one of cylinders 13, 14, and 15) are operated simultaneously.
By operating the swing remote control valve 21, the swing motor 1
The function for activating is as explained in the second case. Further, since the left and right traveling valves 12 _L and 12 _R are switched from the neutral position to the operating position, the limit switch 40 in the electric circuit 17 is linked to close the circuit and energize the electric circuit 17. So solenoid 41
acts on the electromagnetic on-off valve 18 and switches the electromagnetic on-off valve 18 from the oil passage closed position to the oil passage open position. For this purpose, the remote control valve 2 for operating the work actuator is
The pilot pressure derived from any one of 2, 23, and 24 is applied to the shuttle valve 33,
5. It acts on the pilot pressure receiving portion 28 of the on-off valve 19 via the oil passage opening position of the on-off valve 18, the pilot oil passages 66 and 68, and the shuttle valve 31. On the other hand, the pilot pressure is also sent from the pilot oil passage 66 to the pilot pressure receiving portion 43 of the on-off valve 20 via the pilot oil passage 67. Therefore, the on-off valve 19 is switched to the oil passage closed position, and the on-off valve 20 is switched to the oil passage open position, so that the pressure oil discharged from the third pump 9 is transferred to the oil passage 27,
The oil is supplied to the cylinder through the oil passage opening position of the on-off valve 20, the check valve 34 or 35, and the cylinder valve (one of 13, 14, and 15). Therefore, in the third case, the pressure oil discharged from the first and second pumps 7 and 8 is delivered to the left and right traveling valves 12 _L and 12 _R, respectively.
Pressure oil discharged from the third pump 9 is supplied to the swing motor 1 and cylinder via a swing valve 11 and a cylinder valve, respectively.

Effects of the Invention As described above, in the hydraulic circuit having the straight running function of the present invention, various actuators are divided into two groups A and B, and the left and right travel motors are arranged in tandem on the most upstream side of each group A and B. death,
A limit switch is provided that closes the electric circuit in conjunction with the switching operation of the left and right travel motors. Therefore, the electromagnetic on-off valve was switched to the oil passage open position by the action of the solenoid in the electric circuit, and the pilot pressure from the remote control valve for the work attachment was applied to the pilot pressure receiving portions of the two switching valves. Therefore, one of the two on-off valves is switched to the oil passage closed position by the pilot pressure from the swing and work actuator remote control valves.
The other on-off valve is configured to be switched to the oil passage open position by pilot pressure from the remote control valve for the work actuator.

In the prior art, left and right travel motors and other work actuators are connected in parallel in groups A and B, respectively. Therefore, if one of the other actuators is operated while the construction machine is traveling straight ahead, a portion of the supplied hydraulic oil is used by that actuator, so the traveling motors belonging to the used group are supplied with oil. quantity decreases. Therefore, the rotational speed of the traveling motor on the side where the amount of supplied oil is decreased is reduced, and the construction machine begins to travel in a curved direction. As another example of the prior art, in a two-pump type construction machine, when the left and right travel motors and other work actuators are operated simultaneously, the left and right travel motors are connected to the left and right travel motors from one of the second pumps in parallel by the switching operation of the on-off valve. Discharge pressure oil is supplied to the first pump, and other actuators are supplied from the other first pump. For this reason, if a construction machine is on soft ground, for example, and a large load is applied to the travel motor on either the left or right side, and the load on the travel motor on the other side is small, the travel motor on the side with the higher load will stop rotating, making it difficult to run. There was a problem next door.

However, in the present invention, when the left and right travel motors and other work actuators are operated simultaneously, the pressure oil discharged from the first and second pumps is transferred to the left and right travel motors, and from the third pump by the opening and closing operation of the on-off valve. The extruded pressure oil can be supplied to the swing motor and other work actuators. Therefore, the construction machine having the hydraulic circuit of the present invention can travel straight even when other actuators are operated when traveling straight, or even when a large load is applied to one of the left and right travel motors. Driving performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of the present invention, FIG. 2 is a hydraulic circuit diagram of a conventional technique, and FIG. 3 is a hydraulic circuit diagram of another conventional technique. 1... Swivel motor, 2, 3... Left and right travel motors, 4, 5, 6... Cylinder (work actuator), 7, 8, 9... 1st, 2nd, 3rd pump,
10... Pilot pump, 11... Swivel valve, 1
2 _L , 12 _R ...Left, right travel valve, 13, 14, 15
... Cylinder valve, 17 ... Electric circuit, 18 ... Solenoid on-off valve, 19, 20 ... On-off valve, 40 ... Limit switch, 41 ... Solenoid.

Claims (1)

[Claims] 1 Among the various hydraulic actuators installed in construction machinery, the actuators other than the swing motor are divided into two groups A and B, and the actuators are operated by multiple hydraulic pumps via respective switching valves in a hydraulic circuit. The valves 12 _L and 12 _R 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, while the oil passage 25 between the third pump 9 and the swing valve 11
Oil passages 26 and 27 branched from the middle are provided with on-off valves 19 and 20, respectively, and left and right travel valves _12L and 1
2. An electric circuit 17 having a limit switch 40 that closes the electric circuit in conjunction with the switching operation of _R is provided,
The electromagnetic on-off valve 18 which can be switched by the solenoid 41 in the electric circuit 17 is connected to various remote control valves 22, 23,
The pilot pressure receiving portion 28 of the on-off valve 19 and the pilot pressure receiving portions 29, 3 of the swivel valve 11 are provided on the outlet side of the pilot pressure deriving shuttle valve 33 of No. 24.
0 through the shuttle valves 31 and 32, and the pilot pressure receiving part 28 is connected to the shuttle valve 3.
1. Connected to the above-mentioned shuttle valve 33 via the electromagnetic on-off valve 18, and connected to the third pump 9 discharge side tank communication oil passage 2.
6 can be switched on and off, and on the other hand, the on-off valve 20 is connected to the switching valves 13, 14, 1 via check valves 34, 35.
5 are connected to parallel oil passages 36, 37, and 38, respectively, and the pilot pressure receiving part 43 of the on-off valve 20 is connected to the outlet side of the electromagnetic on-off valve 18 to enable oil passage switching. When 2, 3 and other actuators are operated simultaneously, the discharge pressure oil from the first and second pumps 7 and 8 is sent to the left and right travel motors 2 and 3, respectively, and the discharge pressure oil from the third pump 9 is sent to the swing motor 1. A hydraulic circuit for construction machinery, characterized in that the hydraulic circuit is configured to be able to be supplied to other actuators.