JPH0735108A - Priority circuit type flow dividing valve - Google Patents

Abstract

PURPOSE:To decrease a load on a pressure oil supply port side when an oil supply quantity is very small. CONSTITUTION:An operational oil supply port 3, a priority discharge port 4, an excessive oil discharge port 5 and a spool 6 for dividing flow are provided at a priority circuit type flow dividing valve 1. For the spool 6 for dividing the flow, a bleed-off passage 30 with its small diameter is provided in a position from which a part of supply oil is discharged to excessive oil discharge port side when the flow-in quantity of the oil pressure oil from a supply port is small, but which is shut off from an excessive oil discharge port, following the transfer of the spool for dividing the flow, after the supplied oil quantity reaches a specific oil quantity. Consequently, a part of supply oil from the bleed-off passage 30 is discharged when the supply quantity of the operational oil is small, and then a load on the operational oil supply port side is decreased. The bleed-off passage 30 is shut off and is operated as the priority circuit type dividing flow valve when the supplied operational oil supply quantity is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a priority circuit type shunt valve used in a hydraulic steering device for construction machines, cargo handling machines and the like.

[0002]

2. Description of the Related Art Generally, this type of steering apparatus has a structure in which a single hydraulic pump supplies hydraulic oil necessary for cargo handling or other work together with steering. In this case, a priority circuit type flow dividing valve is used as a means for preferentially supplying a constant specified flow rate to the steering device side irrespective of cargo handling and other work and supplying the remaining amount to the cargo handling machine and the like. An example thereof is shown in FIG.

The priority circuit type shunt valve 50 includes a valve body 51.
Is provided with a spool hole 57 and a hydraulic oil supply port 5
2, a priority delivery port 53, a surplus oil delivery port 54, and a diversion spool 55. The spool 55 is housed in a bottomed spool hole 57 together with the pressing spring 56.
The supply port 52 and the surplus oil delivery port 54 are both connected to the spool hole 57 and are normally blocked by the main land 58 formed on the spool 55. The priority delivery port 53 is also connected to the spool hole 57. 60 and 61
Are the priority delivery port 53 and the surplus oil delivery port 5, respectively.
4 is a relief valve, and 62 is a throttle hole formed in the upper land 63 of the diversion spool 55.
The pressurizing chamber 64 formed between the upper cap 65 and the spool 55 communicates with the spool hole 57.

Reference numeral 70 designates a hydraulic circuit for connecting the surplus oil delivery port 54 and the working cylinder CL, and 71 designates a switching valve provided in the circuit. The cutoff valve 71 is a two-position manual switching valve, and the hydraulic circuit 70 is normally open to the tank T via the switching valve 71.

In the above structure, an engine (not shown)
The pressure of the hydraulic oil supplied to the supply port 52 is small at the time of starting the engine, so that the spool 55 is pushed upward by the pressure of the spring 56, and the surplus oil delivery port 54 and the main land 5
The oil is cut off by 8 and is supplied to the priority delivery port 53 side through a small hole 59 communicating with the inner hole of the flow dividing spool 55. When the hydraulic oil pressure rises as the supply amount increases, the pressure oil flows into the pressurizing chamber 64 through the throttle hole 62,
The pressure in the chamber 64 rises, and the pressure pushes the spool 55 downward, whereby the main land 58 descends and the supply port 52 and the surplus oil delivery port 54 communicate with each other, and the pressure oil flows from the delivery port 54. It is supplied to an operating mechanism such as a lift mechanism.

[0006]

The spool 55 has the following structure.
When pressure oil is not supplied from the hydraulic oil supply port 52, it is cut off from the excess oil delivery port 54 and communicated only with the priority delivery port 53. Therefore, when the engine is started when the steering wheel is turned to one side, or when the priority brake outlet side is connected to a power brake and the priority brake outlet side is in the closed state, the load on the engine Is added, and there is a problem that the engine is not running properly. In view of these points, the present invention has an object to reduce the load on the hydraulic oil supply port side when the amount of supplied oil is small.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, a priority circuit type flow dividing valve of the present invention is provided with a hydraulic oil supply port, a priority feeding port, a surplus oil feeding port, and a diversion spool, and has a constant oil amount. Priority to supply to the priority delivery port,
In the priority circuit type flow dividing valve that supplies the pressure oil supplied to the surplus oil delivery port side by moving the flow dividing spool when the supply pressure oil rises to a constant pressure, the flow dividing spool has When a small amount of pressure oil flows in, a small diameter bleed-off passage is formed to discharge a part of the supply oil to the surplus oil delivery port side. The gist is that it is provided at a position where it is cut off from the surplus oil delivery port.

[0008]

[Operation] No pressure is applied to the diversion spool when the inflow is low from the hydraulic oil supply port side, so the bleed-off passage communicates with the surplus oil delivery port side. This reduces the load on the hydraulic oil supply port side. Further, when the hydraulic pressure on the hydraulic oil supply port side after the start-up increases, the hydraulic pressure is applied to the diversion spool, whereby the diversion spool moves to a position where it blocks the bleed-off passage,
After that, it operates as a normal priority circuit type shunt valve.

[0009]

Embodiments FIGS. 1 to 3 relate to an embodiment of the present invention. The priority circuit type flow dividing valve 1 has a hydraulic fluid supply port 3, a preferential delivery port 4, a surplus oil delivery port 5, and a spool hole 8 communicating with each of them, which are bored in a valve body 2, and a diversion spool 6 is provided therein. Equipped with. This spool 6 is a pressing spring 7
Together with it, it is stored in the bottomed spool hole 8. Both the supply port 3 and the surplus oil delivery port 5 open in the spool hole 8 and are normally blocked by the main land 6a formed in the spool 6. Similarly, the priority delivery port 4 also has a spool hole 8
Is connected to the small hole 9 communicating with the inner hole of the spool 6.
Communicates with the supply port 3. Relief valves provided for the priority delivery port 4 and the surplus oil delivery port 5, and 12
Indicates a throttle hole formed in the upper land 6b of the diversion spool 6, and communicates with the pressurizing chamber 14 formed between the upper cap 13 and the spool hole 8 and the hydraulic oil supply port 3.

Reference numeral 20 denotes a hydraulic circuit for connecting the surplus oil delivery port 5 and the working cylinder CL, and 21 denotes a two-position manual switching valve provided in the circuit. Since these structures and their functions are the same as those described above, the description thereof will be omitted.

According to the present invention, in the above construction, when the supply of the hydraulic oil from the hydraulic oil supply port 3 side is small at the time of engine starting and the flow dividing spool 6 is stopped without applying pressure, the operation from the supply port is performed. A part of the oil is allowed to be released, and the release is shut off as the pressure of the supplied oil rises. The diverting spool 6 is opened to the surplus oil delivery port 5, but when the spool 6 moves. Has a small-diameter bleed-off passage 30 communicated with the spool inner hole 31 and punched at a position where it moves into the sliding portion 2a with the valve body 2 and is blocked. The state is shown in FIG.

In the above structure, when the engine is started, the inflow amount of the pressure oil into the hydraulic oil supply port 3 is small and the pressure is low. Therefore, the diversion spool 6 does not move, and the bleed-off passage 30 opens to the surplus oil delivery port 5.
Therefore, a part of the supplied pressure oil flows out to the surplus oil delivery port 5 side through the bleed-off passage 30 through the small hole 9 communicating with the spool inner hole 31, and the hydraulic circuit 20 and the switching valve 2 are provided.
It is discharged to the tank T via 1.

Next, as the engine speed increases and the amount of pressure oil supplied increases, the pressure in the spool hole 8 increases, which causes the pressure oil to flow from the supply port 3 through the throttle hole 12 into the pressure chamber. 14 and pushes the diversion spool 6 downward. As a result, the bleed-off passage 30 moves to a position where it is blocked by the sliding portion 2a, and thereafter, the supply port 3 communicates only with the priority delivery port 4 and is shut off from the surplus oil delivery port 5 at a fixed position. It operates as a normal priority circuit type shunt valve. The state is shown in FIG.

[0014]

As described above, according to the present invention, the shunting spool has a bleed that opens toward the surplus oil delivery port side when the amount of hydraulic fluid supplied to the supply port is small and therefore the hydraulic oil pressure is low. Since the off passage is formed and a part of the pressure oil is discharged from the passage to the surplus oil delivery port side, the load on the hydraulic oil supply port side is reduced even when the priority delivery port side is closed at startup. Can be measured. Also, as the amount of supplied hydraulic oil increases, the supplied hydraulic pressure rises, which shifts the diversion spool, moves the bleed-off passage from the surplus oil delivery port side to the cutoff position, and cuts off the discharge of the supplied oil. , Can operate as a normal priority circuit type shunt valve.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a priority circuit type flow dividing valve according to the present invention.

FIG. 2 is an explanatory diagram of a mounting position of a bleed-off passage when pressure oil supply is stopped.

FIG. 3 is an explanatory diagram of a position of a bleed-off passage accompanying a shift of a flow dividing spool accompanying supply of pressure oil.

FIG. 4 is a vertical cross-sectional view of a prior art priority circuit type flow dividing valve.

[Explanation of symbols]

 1 Priority circuit type shunt valve 3 Hydraulic oil supply port 4 Priority delivery port 5 Surplus oil delivery port 6 Shunting spool 30 Bleed-off passage

Claims (1)

[Claims] 1. A hydraulic oil supply port, a priority delivery port, a surplus oil delivery port, and a shunting spool, and a fixed amount of oil is preferentially supplied to the priority delivery port, so that the supply pressure oil rises to a constant pressure. In the priority circuit type flow dividing valve that shifts the flow dividing spool to supply the supplied pressure oil to the surplus oil delivery port side, the flow dividing spool is configured to supply the pressure oil from the supply port when the flow amount of the pressure oil is low. A small-diameter bleed-off passage is formed to discharge a part of the excess oil to the outlet side, and the passage is located at a position where the supply oil amount reaches a predetermined oil amount and is cut off from the excess oil outlet as the diversion spool moves. A priority circuit type shunt valve characterized by being provided.