JPH0352271Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of the hydraulic circuit of a construction machine, such as a hydraulic excavator.

The hydraulic circuit of a conventional construction machine is explained with reference to Fig. 1. 1 is the other pump, 2 is the one pump,
A is the other control valve, B is one control valve, 3 on the B side of the control valve is the arm operation valve, 4 is the boom operation valve, 5 is the swing motor operation valve, 6 is the travel motor operation valve, 7 on the control valve A side is a travel motor operation valve, 8 is a bucket operation valve, 9 is a boom operation valve, 10 is an arm operation valve, 11 and 12 are left and right travel motors, 13
is the swing motor, 14 is the hydraulic cylinder for the arm, 1
5 is a hydraulic cylinder for the bucket, 16 is a hydraulic cylinder for the boom, 18 is a prime mover that drives the pumps 1 and 2, 19 is a shuttle valve that is switched by the driving hydraulic pressure to the swing motor 13, and 20 is the shuttle valve 19.
In an attempt to simultaneously rotate the swing motor 13, extend or contract the arm cylinder 14, and extend the boom cylinder 16 using the tandem parallel switching valve connected to the When the boom operation valves 4 and 9 are operated simultaneously, in one control valve B, the swing motor operation valve 5 and the arm operation valve 3 are operated in tandem, and each operation valve 5 and 3 is operated from the upstream side. Since they are connected to the downstream side in that order, if the swing motor operating valve 5 is fully operated, pressure oil cannot be supplied from the arm operating valve 3 to the arm hydraulic cylinder 14. On the other hand, since the swing motor operating valve 5 and the boom operating valve 4 are connected in parallel, the swing motor 13 is driven by the lifting pressure of the boom hydraulic cylinder 16, which is at a relatively high pressure. Also, the other control valve A
In this case, pressure oil is supplied from the boom operation valve 9 to the boom hydraulic cylinder 16, and the shuttle valve 19 is switched by the driving oil pressure to the swing motor 13, and the driving oil pressure is applied to the tandem parallel switching valve 2.
0, the tandem parallel switching valve 2
0 is switched to parallel position. Therefore, the arm hydraulic cylinder 14 is
Pressure oil is supplied to. Rotating motor 13 during actual work
The case where the arm hydraulic cylinder 14 and the boom hydraulic cylinder 16 are operated simultaneously is explained with reference to FIG. 2. As described above, the swing motor 13, the arm hydraulic cylinder 14, and the boom hydraulic cylinder 1
6 must be operated at the same time by piling the excavated earth and sand on the bucket a, extending the boom hydraulic cylinder 16, lifting the bucket a, arm b, and boom c, and driving the swing motor 13 at the same time. The bucket truck a is brought close to a dump truck (not shown) that is stopped at a predetermined position, and at this time,
This occurs during a dump truck loading operation in which the arm hydraulic cylinder 14 is extended or contracted, the arm b is raised or raised, and the attitude of the bucket truck a is corrected.
In this dump loading work, focusing on the extension stroke of the boom hydraulic cylinder 16 and the drive process of the swing motor 13, the swing motor 13 lifts the bucket a, arm b, and boom c, so the boom hydraulic cylinder is under relatively high pressure. Since it is driven by the lifting pressure of 16, the drive shaft torque becomes large, and the acceleration torque of the hydraulic excavator rotating body d also becomes large.
In other words, the rotational speed of the hydraulic excavator rotating body d increases. At this time, in one control valve B, the pressure oil from the pump 2 is transferred to the operating valve 5 for the swing motor.
The hydraulic pressure is supplied to the boom hydraulic cylinder 16 through the boom operation valve 4 connected in parallel with the boom control valve A, but the following situation occurs in the other control valve A.
That is, the arm hydraulic cylinder 14 is in the air and is expanding or contracting, and the pressure inside the arm hydraulic cylinder 14 is lower than that inside the boom hydraulic cylinder 16. Therefore, the pressure oil that has reached the upstream side of the tandem-parallel switching valve 20 from the pump 1 is
A large amount of flow passes through the tandem-parallel switching valve 20 to the arm operating valve 10, and only a small amount is supplied from the upstream side of the tandem-parallel switching valve 20 to the boom operating valve 9, so that the extension speed of the boom hydraulic cylinder 16 is reduced. Become slow. The relationship between the rotation angle θ of the rotation motor 13 and the extension amount of the boom hydraulic cylinder 16 at this time is shown by a curve () in FIG.
As is clear from the curve (), the rotation angle θ of the rotation motor 13 is large relative to the extension amount of the boom hydraulic cylinder 16, so during dump loading work, the bucket can be detoured before it becomes higher than the dump truck platform. There was a problem in that the bucket truck A collided with the side of the dump truck's loading platform when the truck reached the dump truck position.

This proposal deals with the above-mentioned problems, and includes a swing motor operation valve 5 and an arm operation valve 3 in which the pressure oil from one pump 2 is connected to the tandem circuit of one control valve B. B
The swing motor 13 and the arm hydraulic cylinder 14 are connected to the boom operation valve 4 connected to the parallel circuit of
and the boom hydraulic cylinder 16, and the pressure oil from the other pump 1 is connected to the boom operation valve 9 of the other control valve A and the tandem circuit downstream of the boom operation valve 9. operation valve 1
0 to the boom hydraulic cylinder 16 and the arm hydraulic cylinder 14, and operates based on the detected driving hydraulic pressure to the swing motor 13. By switching the tandem circuit of the boom operation valve 9 and the arm operation valve 10 to a parallel circuit, it is possible to supply and discharge pressure oil from both the pumps 1 and 2 to the boom hydraulic cylinder 16 and the arm hydraulic cylinder 14. In a hydraulic circuit of a construction machine, a sequence valve 20a or a throttle 20a' is provided inside the tandem parallel switching valve 20, and branched oil branched from the middle of the oil path from the one pump 2 to the one control valve B is provided. Road 22, 23
is connected to the oil passage on the downstream side of the tandem parallel switching valve 20, and a logic valve 21a or an on-off valve 21a' that is switched by the operating pressure of the boom hydraulic cylinder 16 is provided in the middle of the branch oil passages 22 and 23. The purpose of the present invention is to provide an improved hydraulic circuit for construction machinery that can prevent a bucket from colliding with a dump truck during dump truck loading work. .

Next, the hydraulic circuit of the construction machine of the present invention will be explained using an example shown in FIG.
0A and B are the same parts as above, one pump 2
Pressure oil from the swing motor is connected to the tandem circuit of one control valve B through the swing motor operation valve 5, and the arm operation valve 3 is connected to the boom operation valve 4 which is connected to the parallel circuit of the same control valve B. The motor 13, the arm hydraulic cylinder 14, and the boom hydraulic cylinder 16 are supplied and discharged, and the other pump 1
The pressure oil is transferred to the boom hydraulic cylinder 16 and the arm hydraulic pressure through the boom operating valve 9 of the other control valve A and the arm operating valve 10 connected to the tandem circuit downstream of the boom operating valve 9. The other control valve A
The tandem circuit of the boom operation valve 9 and the arm operation valve 10 is switched to a parallel circuit, and the pressure oil from both pumps 1 and 2 is transferred to the boom hydraulic cylinder 1.
6 and the arm hydraulic cylinder 14. Next, the most distinctive feature of the present invention will be described. Reference numeral 20a is a sequence valve, which is provided within the tandem-parallel switching valve 20.
Further, 22 and 23 are branch oil passages branched from the middle of the oil passage from the one pump 2 to the one control valve B, which are connected to the downstream oil passage 25 of the tandem-parallel switching valve and the same. A logic valve 21a that is switched by the operating pressure of the boom hydraulic cylinder is provided in the middle of the branch oil path. 2
1 is a switching valve including a logic valve 21a and a pilot valve 21b, and the pilot valve 21b is switched when pressure is built up in the oil passage 26 upstream of the check valve 27. Note that 24 is a check valve provided in the branch oil passage 23.

Next, the operation of the hydraulic circuit of the construction machine will be explained. When the swing motor operating valve 5 is switched in an attempt to drive the swing motor 13, the arm operating valve 3 on the downstream side is not supplied with pressure oil from the bypass passage 28 because it is connected in tandem. On the other hand, even if the arm operating valves 3 and 10 are simultaneously switched in an attempt to operate the arm hydraulic cylinder 14, the arm operating valves 3 are connected in tandem as described above, so pressure oil is supplied through the bypass passage 28. However, the arm operation valve 10 receives pressure oil from the pump 1 and supplies it to the arm hydraulic cylinder 14. In other words, the swing motor 13 is connected to the pump 2, and the arm hydraulic cylinder 14 is connected to the pump 1.
Pressure oil is supplied from the hydraulic shovel to prevent a situation in which the side pressing force of the swing motor 13 becomes insufficient due to load fluctuations in the arm hydraulic cylinder 14 during excavation work of the hydraulic excavator. Once the excavation work is complete, the work will move on to dump truck loading. At that time, the swing motor 13 is driven, the boom hydraulic cylinder 16 is extended, and the arm hydraulic cylinder 1 is extended.
A three-linked operation is performed to extend or contract 4. At this time, the operating valve 5 for the swing motor, the operating valves 3 and 10 for the arm, and the operating valve 49 for the boom are switched at the same time, but on the control valve B side, the operating valve 3 for the arm is switched to the operating valve 5 for the swing motor. Since they are connected in tandem on the downstream side, they do not receive pressure oil supply. However, since the swing motor operating valve 5 and the boom operating valve 4 are connected in parallel, the pressure oil of the pump valve 2 tends to be supplied to each actuator. On the other hand, the shuttle valve 19 is switched by the drive oil pressure of the swing motor 13, the drive oil pressure is transmitted to the tandem-parallel switching valve 20, the tandem-parallel switching valve 20 is switched, and the oil passages 29 and 25 are switched in sequence. It is connected via valve 20a. Also, since the boom operation valve 4 is switched to extend the boom hydraulic cylinder 16, pressure is built up in the oil passage 26, the pilot valve 21b opens, the logic valve 21a opens, and the branch oil passages 22 and 23 are opened. A portion of the pressure oil from the pump 2 is supplied to the arm operation valve 10 through communication via the valve 24 . Also, arm hydraulic cylinder 1
Of the arm operation valves 3 and 10 that control the operation of boom 4, 3 is connected in tandem and does not receive pressure oil supply as described above, and 10 is operated by the boom operation valve 9 on the upstream side. However, if the pressure in the oil path 29 exceeds the set pressure of the sequence valve 20a, excess oil from the boom operation valve 9 will flow to the sequence valve 20a.
It is supplied to the arm operating valve 10 via a. At this time, since the swing motor operating valve 5, the boom operating valve 4, and the arm operating valve 10 are connected in parallel via the oil passages 22 and 23, the pump 2 can be operated for each of the above operations. Supplying pressure oil to each actuator 13, 16, 14 through the valves 5, 4, 10 at the following pressure, that is, at the pressure of the arm hydraulic cylinder 14, which is in the air and has the lowest operating pressure. become. At this time, the pump 1 supplies pressure oil to the boom hydraulic cylinder 16 with a large load pressure via the boom operation valve 9. In the above state, the driving hydraulic pressure of the swing motor 13 becomes the operating pressure (low pressure) of the arm hydraulic cylinder 14. Also, the oil passage 25 is connected to the arm hydraulic cylinder 1.
Although the pressure is low due to the operating pressure of 4, the oil line 29
Since the sequence valve 20a exists between the oil passage 25 and the oil passage 25, the pressure in the passage 29 is maintained at the set pressure of the sequence valve 20a. Therefore, if the set pressure of the sequence valve 20a is set to exceed the operating pressure when the boom hydraulic cylinder 16 is extended, the boom operation valve 9
The supply of pressure oil to the boom hydraulic cylinder 16 becomes more sufficient. In this case, the boom operation valve 9
Surplus oil from the boom operation valve 9 is not supplied from the boom operation valve 9 to the arm hydraulic cylinder 14 via the arm operation valve 10, but a portion of the pressure oil from the pump 2 is supplied to the branch oil passages 22, 23 and the arm operation valve 14. As already mentioned, the oil is supplied to the arm hydraulic cylinder 14 via the valve 10. In addition, the sequence valve 20
As shown in FIG. 5, the aperture a may be replaced with a low-cost aperture 20a' whose opening is limited to such an extent that the supply of pressure oil to the boom cylinder 16 is functionally insufficient. Furthermore, the logic valve 21a may be replaced with an on-off valve 21a' as shown in FIG.

The hydraulic circuit of the construction machine of the present invention is configured as described above, and during the triple-linked operation of driving the swing motor 13, extending the boom hydraulic cylinder 16, and extending or contracting the arm hydraulic cylinder 14, The motor operation valve 5, the boom operation valve 4, and the arm operation valve 10 are connected in parallel, and the pump 2 is connected to each of the above operation valves 5, 4, 1.
0 to each of the actuators 13, 16, 1
4 at the following pressure, that is, at the pressure of the arm hydraulic cylinder 14, which is in the air and has the lowest operating pressure. At this time, the pump 1 supplies pressure oil to the boom hydraulic cylinder 16 with a large load pressure via the boom operation valve 9.
The above describes the pressure oil required to lift the boom hydraulic cylinder 16 and the arm hydraulic cylinder 14.
While securing the pressure oil required for expansion or contraction of
This means that the rotation speed of the rotation motor 13 can be slowed down (as shown by the curve () in FIG. 3, the rotation angle θ of the rotation motor 13 can be made small relative to the amount of extension of the boom hydraulic cylinder 16) ), during dump truck loading work, turning bucket truck A reaches the dump truck position before bucket truck a is higher than the dump truck platform, and the situation where bucket truck a collides with the side of the dump truck truck platform is avoided. This can be prevented by slowing down the speed, increasing the amount of extension of the arm hydraulic cylinder, and lifting the bucket sufficiently.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing the hydraulic circuit of a conventional construction machine, Fig. 2 is a side view showing a hydraulic excavator, Fig. 3 is an explanatory diagram of the operation of the conventional hydraulic circuit and the hydraulic circuit of the present invention, and Fig. 4 is A hydraulic circuit diagram showing one embodiment of the hydraulic circuit of a construction machine according to the present invention, and FIGS. 5 and 6 are hydraulic circuit diagrams showing other embodiments. 1...Other pump, 2...One pump, A
...Other control valve, B...One control valve, 3,10...Arm operation valve, 4,9
...Boom operation valve, 5...Swivel motor operation valve, 6, 7...Travel motor operation valve, 8...Bucket operation valve, 11, 12...Travel motor, 13
...Swivel motor, 14...Hydraulic cylinder for arm, 15...Hydraulic cylinder for bucket, 16...
Hydraulic cylinder for boom, 20... Tandem-parallel switching valve, 20a... Sequence valve, 20a'...
... Throttle, 21a... Logic valve, 21a'... Open/close valve, 22, 23... Branch oil passage, 25... Tandem-parallel switching valve, downstream oil passage of 20.

Claims (1)

[Scope of utility model registration request] Pressure oil from one pump 2 is connected to the tandem circuit of one control valve B. A swing motor operation valve 5 is connected to the arm operation valve 3 and the same control valve B is connected to a parallel circuit of the boom operation valve 4. The pressure oil from the other pump 1 is supplied to and discharged from the swing motor 13, the arm hydraulic cylinder 14, and the boom hydraulic cylinder 16 through the boom operating valve 9 of the other control valve A and the boom operating valve 9 of the other control valve A. The boom hydraulic cylinder 16 is connected to the arm operation valve 10 connected to the tandem circuit on the downstream side of the boom hydraulic cylinder 16.
The tandem parallel switching valve 20 operates based on the detected driving hydraulic pressure to the swing motor 13, and controls the boom operation valve 9 and the arm operation of the other control valve A. In a hydraulic circuit of a construction machine in which the tandem circuit of the valve 10 is switched to a parallel circuit, pressure oil from both the pumps 1 and 2 can be supplied and discharged to the boom hydraulic cylinder 16 and the arm hydraulic cylinder 14. A sequence valve 20a or a throttle 20a' is provided inside the mu parallel switching valve 20, and the branch oil passages 22 and 23 branched from the middle of the oil passage from the one pump 2 to the one control valve B are connected to the tandem parallel switching valve 20. Switching valve 20
It connects to the downstream oil passage of the same branch oil passage 2.
A hydraulic circuit for construction machinery, characterized in that a logic valve 21a or an on-off valve 21a', which is switched by the operating pressure of a boom hydraulic cylinder 16, is provided in the middle of the boom hydraulic cylinder 16.