JPH0221008A - hydraulic circuit - Google Patents

Abstract

PURPOSE:To obtain an normal action at the time of a low temperature and clogging by fitting an oil filter at a return oil passage and fitting a temperature/ pressure detecting switching valve mechanism between the upper stream side of the oil filter and a suction oil passage. CONSTITUTION:An oil filter 8 is fitted at a return oil passage switching valve mechanism A is provided between the upper stream side of the oil filter 8 and a suction oil passage 3. The switching valve mechanism A consists of the first spring 11 made of a shape memory alloy member for urging a valve body 10 in a direction to be closed and the secondary spring 12 for urging the valve body 10 in a direction to be opened. In case that pressure is risen higher than a predetermined level caused by the clog of the oil filter 8, or in case that oil temperature is lower than a predetermined level, the switching valve mechanism A is operated to be opened. Accordingly, at the time of the clog of the oil filter 8 and the low temperature of the oil temperature, operation oil can be circulated so that a normal action can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic circuit, and more particularly, to a hydraulic circuit in which an oil filter is interposed in a return oil path for returning waste oil from a hydraulic system to a storage section. Regarding improvements.

[Conventional technology]

In the past, for example, in a hydraulic circuit for driving a hydraulic actuator, there is a system in which an oil filter is installed in the return oil path to prevent the hydraulic oil from contaminating the reservoir. In a hydraulic circuit in which an oil filter is installed in the return oil path, when the pressure of the oil filter increases, the upstream and downstream sides are It is common to provide a relief valve to switch the communication state.

[Problem to be solved by the invention]

Considering the properties of the hydraulic circuit, the hydraulic oil used in the hydraulic circuit has high viscosity at low temperatures, so there is a large pressure loss in the hydraulic path at low temperatures, and even if the control valve is operated a predetermined amount, , the hydraulic actuator may not operate as much as needed.

In addition, if the temperature of the hydraulic oil is low, normal operation cannot be expected, so when using a work vehicle with a hydraulic actuator, such as a backhoe or wheel loader, in a low-temperature environment, the engine After starting the system, do not perform any work for a predetermined period of time, and take measures such as forcibly sending the hydraulic oil to a path with high flow resistance to raise the temperature of the hydraulic oil in the entire storage group before starting work. may also start.

However, when trying to raise the oil temperature in the entire storage area in this way, it takes time and leads to a decrease in work efficiency.

An object of the present invention is to make a rational improvement of a hydraulic circuit in which an oil filter is installed in the return oil passage, so that when the oil filter becomes clogged, the hydraulic oil can be circulated without being stagnated. The object of the present invention is to configure a hydraulic circuit that ensures normal operation by raising the oil temperature in as short a time as possible even when the temperature of the hydraulic oil is low.

[Means to solve the problem]

A feature of the present invention is that an oil filter is interposed in the return oil path for returning waste oil from the hydraulic system to the storage section, and hydraulic oil from the upstream side of the oil filter and the storage section is sent to the hydraulic pump. A temperature-sensitive pressure switching valve mechanism is interposed between the suction oil passage and the valve that opens to allow hydraulic oil to flow when the oil temperature is below a predetermined value or when the pressure in the return oil passage reaches a predetermined value or higher. The functions of the system are as follows:
The effects are as follows.

[For production]

If the above characteristics are configured as shown in FIG. 1, for example, the oil filter (8) will become clogged and the oil filter (8)
When the pressure in the return oil passage (6) rises above a predetermined value, the temperature-sensitive pressure switching valve mechanism (A) opens and sends the hydraulic oil in the return oil passage (6) to the suction oil passage (3). Even when the oil temperature in step 6) is lower than the predetermined value, the hydraulic oil in the return oil path (6) is sent to the suction oil path (3).

In other words, when the oil temperature is low, the hydraulic oil in the return oil passage (6) is sent to the suction oil passage (3) instead of being returned to the reservoir (2), so the hydraulic oil sent in this way flows through the circuit. While circulating, the temperature will rise.

〔Effect of the invention〕

Therefore, by improving the structure of the valve and the structure of the oil passage,
If the oil filter becomes clogged, the hydraulic oil is allowed to flow without stagnation, and if the temperature of the hydraulic oil is low, the hydraulic oil in the return oil path is circulated without returning to the reservoir. , to raise the oil temperature in a short time,
A hydraulic circuit was constructed to ensure normal operation.

〔Example〕

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

FIG. 1 shows a hydraulic circuit for controlling a hydraulic actuator (1). In this hydraulic circuit, hydraulic oil in a reservoir (2) is passed through a suction oil path (3) to a hydraulic pump (4).
), and the hydraulic oil from the hydraulic pump (4) is sent to the hydraulic actuator (1) via the control valve (5). Further, the drained oil from the hydraulic actuator (1) is sent to the return oil path (6) via the control valve (5) and returned to the storage section (2).

As shown in the figure, the storage section (
An oil filter (7) is provided in each of the suction oil passage (3) and the return oil passage (6) on the side of 2).

(8) is interposed, and furthermore, the upstream side of the oil filter (8) of the return oil path (6) and the downstream side of the oil filter (7) of the suction oil path (3) (the side of the hydraulic pump (4) )
A temperature-sensitive pressure switching valve mechanism (A) is interposed between the two.

As shown in Fig. 2, this temperature-sensitive pressure switching valve mechanism (A) includes a valve body (10) that opens and closes an oil passage (9), and a shape memory alloy material that biases this valve body (10) in the closing direction. The first spring consisting of (
11) and a second bias spring (12) that biases the valve body (10) in the opening direction. If the oil temperature rises to a certain level, the first spring (11) opens against the urging force of the first spring (11), and if the oil temperature is below a predetermined value, such as when starting an engine (not shown), the second spring (11) opens. 12
) is configured to open with the urging force of.

The shape of the first spring (11) when restored is set so that the biasing force is strengthened when the temperature reaches a set temperature or higher, so when the oil temperature reaches a set temperature or higher, the valve body ( 10) is designed to be closed.

[Another example]

In addition to the embodiment described above, the present invention has a hydraulic circuit configured to send hydraulic oil from the return oil passage (6) to the upstream side of the oil filter (7) of the suction oil passage (3), as shown in FIG. 3, for example. Alternatively, the second spring may be removed from the structure shown in FIG. 2 to configure the temperature-sensitive pressure switching valve, or bimetal or thermal expansion of liquid may be used.

Further, the present invention can be applied to hydraulic systems of various work vehicles such as backhoes and wheel loaders.

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 a hydraulic circuit according to the present invention, FIG. 1 is a hydraulic circuit diagram, FIG. 2 is a sectional view of a temperature-sensitive pressure switching valve mechanism, and FIG. 3 is a hydraulic circuit diagram showing another embodiment. It is. (2)...Storage part, (3)...Suction oil path, (4)...Hydraulic pump, (6)...
... Return oil path, (8) ... Oil filter, (A) ... Temperature-sensitive pressure switching valve mechanism

Claims (1)

[Claims] An oil filter (8) is interposed in the return oil passage (6) for returning waste oil from the hydraulic system to the storage part (2), and an oil filter (8) is installed on the upstream side of this oil filter (8) and the storage part (2).
If the oil temperature is below a predetermined value between the suction oil passage (3) that sends hydraulic oil from the
A hydraulic circuit equipped with a temperature-sensitive pressure switching valve mechanism (A) that opens when the pressure in the return oil passage (6) reaches a predetermined value or higher to allow hydraulic oil to flow.