JPS592210Y2 - Hydraulic circuit of upper swing type hydraulic excavator - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit for an upper swing type hydraulic excavator.

The hydraulic circuit of a conventional top swing type hydraulic excavator is shown in Figure 1. It is a two-pump system, and the operating valves are divided into two groups A and B. Group A operates the left travel motor 1. The left travel motor operation valve 2 that operates the boom cylinder 3, the boom speed increase operation valve 4 that operates the arm cylinder 5, the arm operation valve 6 that operates the arm cylinder 5, and the swing motor operation valve 8 that operates the swing motor 7 are included in group B. includes a right side travel motor operation valve 10 that operates the right side travel motor 9, a bucket operation valve 12 that operates the packet cylinder 11, and a boom operation valve 14 that operates the boom cylinder 3.

The circuit configuration of each operating valve in each group A, B is a parallel circuit.

In a circuit configured in this way, in a combined operation of the arm and swing, which is often performed in the L-section swing type hydraulic excavator, (1) the swing structure does not accelerate when the arm and the swing structure are operated at the same time; (2) If you operate the arm while turning, the turning will stop, but there is a problem with it being extremely slow.

When the arm and rotating body are operated in combination, the pressure to accelerate the rotating body becomes the holding pressure of the arm, but since the holding pressure of the arm is low, sufficient acceleration pressure cannot be obtained to accelerate the rotating body. It's for a reason.

In addition, (3) in order to finish the groove side surface vertically, the packet is applied to the groove side surface with the -L section revolving body, and the arm excavates the groove side surface, which is a problem in that so-called "starting digging" does not go well.

This is because when the arm load decreases during excavation, the pressure in the arm circuit increases.

As a result, the packet escapes due to the horizontal turning force, and the groove cannot be finished vertically.

The above problem is caused by the fact that the arm and the revolving body are in the same operating valve group A, which is configured in a parallel circuit, and are operated by the same pump.

In order to solve this problem, it would be possible to change the hydraulic circuit and configure an independent circuit for turning the revolving structure, and install a hydraulic pump and control valve exclusively for turning, but this would significantly increase costs. I can't escape.

The present invention was conceived in consideration of the above, and attempts to provide a hydraulic circuit for an upper swing type hydraulic excavator that can solve the above-mentioned conventional problems by only slightly changing the conventional hydraulic circuit. It is something to do.

The configuration will be explained below based on the embodiment shown in FIG.

In the B group of operating valves, a switching valve 15 having the same valve structure as the boom operating valve 14 and the other operating valves is connected in a parallel circuit configuration like the other valves.

Note that this switching valve 15 is different from other operating valves in that it is switched from a neutral position 15a to a switching position 15b by pilot pressure acting on a pilot port.

The neutral line 16 at the neutral position 15a is connected to the tank, and the actuator line 17 is connected after the load check valve 18 of the parallel circuit on the inlet side of the swing motor operation valve 8 of the A group. .

Take out the pilot lines from the reciprocating circuits 7a and 7b connected to the swing motor 7, and connect them to the shuttle valve 1.
9. Connected to the pilot port of the switching valve 15 via the switching valve 20.

The switching valve 20 has a drain position 20a for draining the pilot pressure of the switching valve 15, and a communication position 20b on both sides thereof.
, 20b, which are normally located at the drain position 20H, and are set to the communicating position 20b when pilot pressure is applied to either pilot port at both ends.

A throttle valve 21 is interposed in one circuit of the reciprocating circuit connected to the arm cylinder 5. Pilot lines are taken out from before and after this throttle valve 21, and these are connected to the switching valve 20.
Connect to the pilot ports at both ends.

In the above configuration, among the A group of operation valves, the swing motor operation valve 8 and the arm operation valve 6 are operated, and the swing motor 7 is operated.
When the swing body and arm are operated in combination by driving the arm cylinder 5 and the arm cylinder 5, the switching valve 20 is switched to the communication position 20b due to the pressure difference between the throttle valve 21 in the circuit of the arm cylinder 50, and the circuit of the swing motor 7 is switched to the communication position 20b. The pilot pressure acts on the switching valve 15, resulting in switching position 15b.

In this way, the pressure oil flowing to group B of the operation valve is switching valve 1.
5, the actuator circuit 17, and the swing motor operating valve 8, where it is added to drive the swing motor.

Therefore, in this case, the arm cylinder 5 and the swing motor 7 are each operated almost independently by two hydraulic pumps, and each work is performed with sufficient operating force.

When the rotating body is operated independently, the pilot pressure from the swing motor circuit tries to flow from the shuttle valve 19 to the switching valve 15, but since the switching valve 20 in front of it remains neutral, it is blocked here. No pilot pressure acts on the switching valve 15, so that no pressure oil from group B flows to the swing motor circuit.

When the arm cylinder 5 is operated independently, the switching valve 20 is switched to the communication position 20b due to the pressure difference of the throttle valve 21, but since there is no pilot pressure from the swing motor circuit, the switching valve 15 does not operate, and therefore the B group Pressure oil from the rotor does not flow into the swing motor circuit and is drained as is.

Further, when the rotating body, boom, and arm are operated in combination, the acceleration pressure of the swing becomes the holding pressure of the boom, and since the boom holding pressure is considerably larger than the holding pressure of the arm, the rotating body is smoothly accelerated.

The present invention is as described above, and the left and right travel motor operating valves 2
, 10, boom speed increase operation valve 4, arm operation valve 6, swing motor operation valve 8, packet operation valve 12, boom operation valve 14
An upper swing system of a two-pump system in which operating valves such as the above are divided into two groups A and H, each of which is connected to a hydraulic pump, and one group A includes the arm operating valve 6 and the swing motor operating valve 8. In the hydraulic circuit of a type hydraulic excavator,
Group B of operating valves that do not include both operating valves 6.8 above
The valve structure is the same as that of each operating valve included in each group, and the pilot pressure changes from neutral position 15 a to switching position 15.
A switching valve 15 is provided in parallel with other operating valves, and its neutral line 16 is connected to the tank, and the actuator line 17 is connected to the swing motor operating valve 8.
A pilot line from the swing motor circuit is connected to the pilot port of the switching valve 15 after the load check valve 18 in the parallel circuit on the inlet side of the switch valve 15, and a throttle installed in the arm cylinder circuit is connected to this pilot line. The hydraulic circuit of the upper swing type hydraulic excavator is constructed by interposing the switching valve 20 which is operated intermittently depending on the pressure difference between the front and rear of the valve 21, so that the arm and swing can be easily adjusted by just slightly changing the conventional hydraulic circuit. This solves the conventional problem of the rotating body not accelerating, stopping, or becoming extremely slow when the body is operated at the same time or when the arm is operated while turning. By having sufficient pressure oil for both the engine and the swing motor drive, sufficient starting power can be obtained during trench excavation work.
The trench sides can be excavated vertically.

Furthermore, according to the present invention, the switching valve 15 for supplying pressure oil from the other operating valve group B to the swing motor side has the same valve structure as the other operating valves constituting the operating valve group, and is arranged in parallel. This connection requires only minor modifications to conventional hydraulic circuits and components and can be obtained at extremely low cost.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing a conventional example, and FIG. 2 is a hydraulic circuit diagram showing an embodiment of the present invention. 2.10 is the travel motor operation valve, 4 is the boom speed increase operation valve,
6 is an arm operating valve, 8 is a swing motor operating valve, 12 is a bucket 1 to operating valve, 14 is a boom operating valve, 15.20 is a switching valve, 16 is a neutral line, 17 is an actuator line, 1
8 is a load check valve, 21 is a throttle valve.

Claims (1)

[Scope of utility model registration request] Left and right travel motor operation valves 2, 10, boom speed increase operation valve 4
, the arm operation valve 6, the swing motor operation valve 8, the packet operation valve 12, the boom operation valve 14, etc. are divided into two groups A and H, and a hydraulic pump is connected to each group, and the arm operation valve 6 and the swing motor operation valve 14 are divided into two groups A and H, and a hydraulic pump is connected to each group. One group A of the motor operated valve 8
In the hydraulic circuit of an upper swing type hydraulic excavator with a two-pump system, the operating valve group B that does not include the operating valves 6 and 8 has the same operating valve as each operating valve included in each group. A switching valve 1 having a valve structure and switching from a neutral position 15a to a switching position 15b by pilot pressure
5 is provided in parallel with other switching valves, and its neutral line 16 is connected to the tank, and the actuator line 1 is connected to the tank.
7 is connected after the rod check valve 18 of the parallel circuit on the inlet side of the swing motor operating valve 8, and a pilot line from the swing motor circuit is connected to the pilot port of the switching valve 15, and an arm cylinder is connected to this pilot line. 1. A hydraulic circuit for an upper swing type hydraulic excavator, characterized in that a switching valve 20 is interposed in the circuit, and the switching valve 20 is switched on and off depending on the pressure difference before and after a throttle valve 21 installed in the circuit.