JPH0511414Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a flushing valve used in hydrostatic transmissions and the like.

[Prior Art] As schematically shown in FIG. 3, a hydrostatic transmission is a system in which a variable displacement hydraulic pump 1 and a constant displacement hydraulic motor 2 are connected in a closed circuit. 3 drives the hydraulic pump 1, and the flow rate of hydraulic oil discharged from the hydraulic pump 1 transmits power to the hydraulic motor 2. In such a hydrostatic transmission, a flushing valve 4 is known as a means for cooling the hydraulic oil.

As can be understood from the flushing valve 4 in FIG. 3, the flushing valve 4 changes its position based on the pressure difference between both ports 5 and 6 of the hydraulic motor 2, and always supplies hydraulic oil from the low-pressure side circuit. The hydraulic oil is taken out and guided to an oil cooler 7.

There have been various types of such flushing valves 4, and a typical configuration thereof is shown in FIG. 4.

That is, in FIG. 4, the flushing valve 4
The valve chamber 8 is formed in the housing 9 of the hydraulic motor 2, and oil introduction passages 10 and 11 communicating with the ports 5 and 6 of the hydraulic motor 2 are located at the left and right end sides of the valve chamber 8, respectively. An oil outlet passage 12 is opened at the center of the side surface of the valve chamber 8 and communicated with an oil cooler (not shown) in the drain circuit. Both ends of the valve chamber 8 are plugs 1
3, 14, and this plug 13,
Sleeve 15, 1 fixed to the valve chamber side end surface of 14
6, the end of the shaft 17 is slidably supported. Poppets 18 and 19, which are valve bodies, are slidably fitted onto the shaft 17 located between each of the oil introduction passages 10 and 11 and the oil outlet passage 12, and are inserted into the central portion of the valve chamber 8. The poppets 18 and 19 are brought into contact with the stepped portions 8a and 8b formed by reducing the diameter of the poppets 18 and 19 by means of compression springs 20 and 21, thereby blocking the outlet passage 12 and each of the introduction passages 10 and 11. There is.

Small gaps 22, 23 are formed in the fitting portions of the sleeves 15, 16 and the shaft 17, and the sleeve 1 is inserted through these gaps 22, 23.
The pressure in the spaces 24, 25 in 5, 16 becomes equal to the ports 5, 6 of the hydraulic motor 2 on the corresponding side.
Also, since the gaps 22 and 23 provide a throttle effect, the spaces 24 and 25 in the sleeves 15 and 16
functions as a damper chamber that is unaffected by minute pulsations of hydraulic pressure. Hereinafter, these spaces 24 and 25 will be referred to as damper chambers 24 and 25, respectively. When hydraulic oil is discharged from one port of the hydraulic pump 1, a pressure difference is generated between the ports 5 and 6 of the hydraulic motor 2, and this causes a pressure difference between the ports 5 and 6 of the hydraulic motor 2. For example, when the pressure in the damper chamber 25 becomes low and the pressure in the damper chamber 24 becomes high, the shaft 17 moves to the low pressure side, that is, to the right, and the shoulder 26 formed on the shaft 17 moves toward the poppet, as shown in FIG. 19 to connect the low pressure side oil inlet path 11 and oil outlet path 12. Further, the oil introduction path 10 and oil outlet path 12 on the high pressure side are maintained in a disconnected state. In this way, hydraulic oil is guided to the oil cooler only from the low-pressure side, which has little bearing on power transmission, so that the hydraulic oil can be cooled.

[Problems to be solved by the invention] In the conventional configuration as described above, the axial length of the gap between the shaft and sleeve changes depending on the positional relationship between them, so the throttling effect due to this gap changes greatly. Therefore, the time from when a pressure difference occurs between the ports of the hydraulic motor until the shaft starts moving (so-called switching time) and the moving speed of the shaft have become unstable. Especially the fifth
When the axial length of the gap is very long, as in the relationship between the shaft 17 and the sleeve 16 in the figure, if the hydraulic oil becomes highly viscous due to the low temperature, this gap can be replaced by hydraulic oil. There was a problem that almost no flow occurred and it took a long time to switch.

The purpose of this invention is to solve these problems.

[Means for Solving the Problems] This invention, in the flushing valve of the conventional configuration described above, connects the valve chamber around each sleeve and the damper chamber within this sleeve with a flow having a throttling effect formed in a plug. They are characterized by being connected by roads.

[Function] In the flushing valve according to this invention, the hydraulic oil flows through the channel formed in the plug, so the throttling effect that occurs when the hydraulic oil enters and exits the damper chamber is almost eliminated. becomes constant.

[Embodiments] Hereinafter, preferred embodiments of the flushing valve according to this invention will be described in detail with reference to the drawings.

Note that the same or equivalent parts as in the conventional configuration will be described using the same reference numerals.

As shown in FIG. 1, the flushing valve 30 of this invention has a cylindrical valve chamber 8 formed in a housing 9 of a hydraulic motor 2 in a hydrostatic transmission, similar to the conventional configuration described above. Each port 5 of the hydraulic motor 2,
Oil introduction passages 10 and 11 communicating with the valve chamber 6 are opened at the left and right end sides of the side surface of the valve chamber 8, respectively, and
An oil outlet path 12 opened at the center of the side surface is led to an oil cooler (not shown) in a drain circuit. Both ends of the valve chamber 8 are closed by plugs 31, 32, and sleeves 15, 16 are fixed to the end surfaces of the plugs 31, 32 on the valve chamber side. An end portion of a shaft 17 is slidably fitted into each of the sleeves 15 and 16. The spaces within the sleeves 15 and 16 are communicated with the outside through gaps 22 and 23 between the fitting portions of the sleeves 15 and 16 and the shaft 17, forming damper chambers 24 and 25. , 25, the shaft 17 moves to the low pressure side. Poppets 18 and 19 are fitted into the shaft 17, and when there is no pressure difference between the damper chambers 24 and 25, compression springs 20 and 21 are inserted into the stepped portions 8a and 8b formed in the valve chamber 8. The oil inlet passages 10, 11 and the oil outlet passage 12 are thereby cut off.

In this invention, as clearly shown in FIG.
4, the valve chamber 8 around the sleeves 15, 16
and the damper chambers 24, 25 are communicated with each other with a throttling effect.

In such a configuration, the operation of the flushing valve according to this invention will be explained next.

FIG. 1 shows a case where there is no pressure difference between both ports of the hydraulic motor, and at this time both oil inlet passages 10 and 11 are blocked off from oil outlet passage 12 by poppets 18 and 19.

Here, when the pressure at port 5 of the hydraulic motor 2 increases and the pressure at the other port 6 decreases, the gap 2
2, 23 and the grooves 33, 3 on the plugs 31, 32
4, the pressure in each damper chamber 24, 25 becomes equal to the port 5, 6 on each side, and the shaft 17 moves toward the damper chamber 25 on the low pressure side due to the pressure difference between the damper chambers 24, 25. do. The movement operation is exactly the same as that of the conventional structure described above. Referring to FIG. It communicates with the oil outlet path 12.

At this time, the sleeve 16 and shaft 17 on the low pressure side
The length of the gap 23 in the axial direction becomes longer as the shaft 17 moves, and the throttling effect increases. As a result, the flow of hydraulic oil in and out through the gap 23 is reduced, but since the throttling effect of the groove 34 formed in the plug 32 is constant, the pressure inside the damper chamber 25 is reduced to the outside in a nearly constant time. is equal to the pressure of Therefore, even if the port 6 side of the hydraulic motor 2 is switched to high pressure, the hydraulic oil is introduced into the damper chamber 25 mainly through the groove 34, and the shaft 17 immediately starts moving toward the damper chamber 24. .

In this embodiment, radial grooves 33 and 34 are formed in the plugs 31 and 32, and these grooves are connected to the damper chamber 24,
25, one end opens into the valve chamber 8 around the sleeves 15, 16, and the other end opens into the damper chambers 24, 25, respectively. The plugs 31 and 32 may also be bored.

In this embodiment, the flushing valve is built into the hydraulic motor 2, but
It will be easily understood that it may be built into the hydraulic pump 1, or may be provided separately and independently.

[Effects of the invention] As described above, according to this invention, by forming the flow path in the plug, the damper chamber and the valve chamber communicate with each other with a certain throttling effect, reducing the switching time and the shaft. The movement speed of is stabilized. Particularly, even when the viscosity of the hydraulic oil is high at low temperatures, the delay in switching time can be minimized.

Furthermore, if the flow path is provided in the plug, the shaft can be moved until its end face abuts on the plug, so the overall length of the flushing valve can be shortened and the flushing valve can be made more compact.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of a flushing valve according to this invention, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figure 3 is a hydrostatic transformer in which the flushing valve is installed. The transmission circuit diagrams, Figures 4 and 5, are schematic explanatory diagrams of conventional flushing valves. Figure 4 shows the case where the pressures at both ports of the hydraulic motor are equal, and Figure 5 shows the case where the pressure is equal between the ports. This shows a case where a pressure difference occurs. In the figure, 4, 30... Flushing valve, 8... Valve chamber, 10, 11... Oil inlet path, 12... Oil outlet path, 13, 14, 31, 32... Plug, 15,
16...Sleeve, 17...Shaft, 18,1
9...Poppet, 22, 23...Gap, 24,2
5... Damper chamber, 33, 34... Groove.

Claims (1)

[Scope of utility model registration request] A valve chamber in which two oil introduction passages are opened at each end of the side surface and one oil discharge passage is opened at the center of the side surface, and a plug that closes both ends of the valve chamber. , a sleeve fixed to the valve chamber side end surface of each of the plugs, a shaft whose end is fitted into each of the sleeves and is slidably supported within the valve chamber, and within each of the sleeves. When the shaft moves to the low pressure side due to the pressure difference between the damper chamber, which is formed and communicates with the outside through a gap between the fitting portion of the sleeve and the shaft, In the flushing valve, the flushing valve includes a valve body configured to communicate the inlet passage and the outlet passage on the low pressure side with movement, and the valve chamber around each sleeve and the damper chamber in the sleeve. and a flushing valve that communicates with the plug through a flow path having a throttling effect formed in the plug.