JPH02217529A - Hydraulic circuit construction of full swiveling type operation car - Google Patents

Abstract

PURPOSE:To control cavitation in oil supply lines by connecting a suction oil line between the oil supply lines of a swivel base hydraulic motor controlling valve and an oil discharge line through check valves and, at the same time, providing a throttle means to the lower part of the oil discharge line. CONSTITUTION:An oil discharge line 16 of a swivel controlling valve V8 and pressure oil supply lines 17 and 17 are connected to a suction oil line 19 through check valves 18 and 18. Then, a throttle section 20 and an operating fluid cooling oil cooler 21 are provided to the lower part of a connection point X on the oil discharge line 16. A by-pass circuit A of the throttle section 20 and oil cooler 21 is also provided. Pressure is increased at the connection point X by the throttle section 20, even if the oil supply lines 17 and 17 become negative pressure in case the swivel base stops, the pressure oil is absorbed from the oil line 19, the generation of cavitation is controlled and, at the same time, in case oil discharge pressure reaches above a setting point, the oil is discharged from the by-pass circuit A. Accordingly to the constitution, damage to the oil cooler 21 can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic circuit structure for a full swing type work vehicle such as a backhoe. Concerning the hydraulic circuit structure of a full swing type work vehicle.

[Prior Art] In the conventional hydraulic circuit structure, a dedicated valve mechanism was provided in the oil supply path for the hydraulic motor to prevent free rotation due to the inertia of the swivel base during a rotation stop operation. (For example, see Japanese Patent Laid-Open No. 62-146327).

(Problem to be Solved by the Invention) However, in a structure in which a dedicated valve mechanism is provided as described above, when the swivel table is turned and then stopped, due to the action of the valve mechanism, This has the drawback of causing a large impact as the heavy swivel base comes to a sudden stop, and pressurized oil is suddenly supplied after a short time delay when the lever is operated at the start of a swivel. It had the disadvantage of starting to turn suddenly and causing a recoil impact.

Therefore, in order to eliminate the above-mentioned drawbacks, a structure was devised in which the valve mechanism was omitted and a suction oil passage was formed which communicated with the inside of the tank via a check valve from the middle of the oil supply passage to the hydraulic motor.

This improved structure eliminates the problem of overrun caused by the inertia of the swivel table when the swivel stops, causing negative pressure in the oil supply line and causing cavitation, which can cause damage to the pipe line. The idea is to prevent this by sucking out the oil in the tank.

By the way, even with the above-mentioned improved structure, it is difficult to prevent the pressure inside the conduit from becoming negative in an instant when the swivel table is stopped.

An object of the present invention is to alleviate the shock at the time of starting and stopping the above-mentioned swing operation, and to suppress the occurrence of cavitation in the oil supply passage when the swing operation is stopped.

[Means to solve the problem]

A feature of the present invention is that a swivel base is mounted on the traveling machine base, which is fully rotatable by the drive of a hydraulic motor; A suction oil passage is connected to an intermediate part of the pressure oil supply passage to the drain passage through a check valve, and a throttling means is provided at a part of the drainage passage downstream of the drain oil flow from the connection point of the suction oil passage. In addition to installing an oil cooler in that order, a bypass circuit is provided that bypasses the throttle means and the oil cooler to drain oil when the exhaust pressure on the upper side of the throttle means exceeds a set value. The actions and effects are as follows.

[For production]

That is, when the hydraulic motor is being driven, the hydraulic oil flows from the pressure oil supply path through the hydraulic motor control valve and the oil drain path, passes through the throttle means and the oil cooler, cools down, and then becomes a floating oil. Ru.

At this time, oil does not flow into the suction oil passage with the check valve interposed therebetween.

If the swivel table overruns due to inertia when the slewing stops, the pressure is increased by the throttling means at the connection point between the suction oil passage and the oil discharge passage, so if the inside of the pressure oil supply passage starts to become negative pressure, At the same time, oil is immediately sucked in from the suction oil passage via the check valve. Moreover, when the temperature of the hydraulic oil drops and its viscosity increases, causing the pressure on the upper side of the throttle means to become too high, or when a blockage occurs in the oil cooler, the The oil will be diverted and drained.

C Effects of the Invention] Therefore, according to the present invention, by providing a throttling means in the oil drain path, the oil pressure on the upper side of the suction oil path can be increased from a state of approximately zero pressure to a set value. When the engine overruns, the suction pressure difference due to negative pressure becomes larger than before, making it possible to suppress the occurrence of cavitation as much as possible. Moreover, damage to the oil cooler can be prevented by rationally arranging a bypass circuit that reduces pressure loss caused by changes in oil viscosity by providing a throttle means.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a full swing type working vehicle according to the present invention. This work vehicle is equipped with a hydraulically driven swivel base (2) on a crawler traveling machine base (1), and the swivel base (2) has a driving part (3), a driving part (4), and a swing base. A backhoe device (6) that can swing and retract around the vertical axis is attached via a bracket (5), and a dozer device (24) is connected to the front part of the traveling machine base (1).

Next, the hydraulic circuit structure will be explained.

Figure 1 shows the hydraulic circuit of the work vehicle. That is, the service port operation valve (S), the arm operation valve (Vl) for the arm cylinder (7), the merging spacer (8), the merging valve for the boom (V2), the left and right travel motor (Ml), and the (gate 2)
) for one of the traveling substitute valves (V3) and the merging valve (V4
) is formed into a center bypass type multiple valve, and is connected to the first hydraulic pump (P, ) so as to be supplied with pressure oil via the first oil supply path (9). Left and right travel motor (Ml)
, (Traveling operation valve (V,) for the other side of M, boom operation valve (V8) for the boom cylinder (10), and
Packet operated valve (V) for packet cylinder (11)
, ) is formed into a center bypass type multiple valve, and the second valve is formed into a center bypass type multiple valve.
It is connected to the second hydraulic pump (P2) so as to be supplied with pressure oil through the oil supply passage (12) and to be supplied with pressure oil through the second oil supply passage (12). Hydraulic motor for swing (H3)
Swing operation valve (V,), swing cylinder (13
) and the dozer operation valve (Lo) for the dozer cylinder (14) are formed into center bypass type multiple valves, and the third oil supply path (15)
A third hydraulic pump (P3) to be supplied with pressure oil via
It is connected to.

The travel control valves (V, ) and Kuri, ) are configured to be switched and operated individually by a pair of control levers (not shown),
The boom operation valve (V6) and the packet operation valve (V7) are configured to be switched and operated by a single operation lever (not shown) that can freely swing in a cross direction. The swing operation valve (V8) and the swing operation valve (V,) are alternatively linked to one operation lever (not shown), and the arm operation valve (V+) and the swing operation valve (V8) are connected to one operation lever (not shown) or The arm operation valve (vl) and the swing operation valve (V,) are configured to be switched and operated by a single operation lever that can freely swing in a cross direction.

An intermediate portion of the oil drain path (16) from the swing operation valve (V8) as a control valve for the swing hydraulic motor (M3) and a pressure oil supply path from the swing operation valve (V6) to the hydraulic motor 0+*). (17) and (1, 7) are connected by a suction oil passage (19) via a pair of check valves (1B) and (18), and the suction oil passage (16) is connected to the suction oil passage (19) through a pair of check valves (1B) and (18). A constriction part (20) as a throttling means is formed at the downstream side of the drain oil flow from the connection point (χ) of the oil passage (19), and a constriction part (20) is formed on the downstream side of this constriction part (20) to cool the hydraulic oil. A 2-piece oil cooler is installed.

When the pressure on the upstream side of the drained oil flow of the throttle part (20) exceeds a set value, the throttle part (20) and the oil cooler (21
) is provided with a bypass circuit (A) that bypasses and drains oil. In other words, the upper side of the throttle part (20) and the oil cooler (20)
1) A bypass circuit equipped with a check valve (22) that allows oil to flow in the discharge direction when the pressure on the upper side exceeds a set value determined by the spring biasing force. Connect at (23).

With this configuration, it is possible to smoothly start and stop the rotation of the swivel base (2) by operating the control valve (Vl), and it is possible to soften the impact, and even if there is an overrun when the rotation is stopped. The suction oil passage (19) starts from the part where the pressure has been increased in advance by the throttle part (20).
, check valve (18).

Oil is immediately sucked through ( ] 8), making it possible to suppress the occurrence of cavitation.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the hydraulic circuit structure of a full swing type work vehicle according to the present invention, and FIG. 1 is a hydraulic circuit diagram, and FIG. 2 is an overall side view of the work vehicle. (1)...Traveling machine base, (2)...Swivel base, (16)...Drainage path, (17)...
・Pressure oil supply path, (18)...Check valve, (1
9)...Suction oil path, (20)...
Throttle part, (21)...Oil cooler, (V,)
...Control valve/lube, (M,)...Hydraulic motor, (A)...Bypass circuit.

Claims (1)

[Claims] A swivel base (2) is mounted on the traveling machine base (1) and is fully rotatable by the drive of a hydraulic motor (M_3). ) and the midway part of the pressure oil supply path (17) from the control valve (V_8) to the hydraulic motor (M_3) are connected to the suction oil path ( 19), and a throttling means (20) and an oil cooler (21) are connected in that order to a portion of the oil drain path (16) on the downstream side of the drain oil flow from the connection point of the suction oil path (19). In addition, a bypass circuit (A) is provided which bypasses the throttle means (20) and the oil cooler (21) and drains oil when the exhaust pressure on the upper side of the throttle means (20) exceeds a set value. Hydraulic circuit structure of a fully rotating work vehicle.