JPH0749042Y2 - Pilot valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a push rod seal device in a pilot valve for controlling the operation of a variable displacement pump, a control valve and the like by pilot pressure.

[Conventional technology]

This type of pilot valve is designed to generate a pilot pressure at its output port according to the operating angle of the operating lever. This will be described with reference to the conventional valve shown in FIG. 2, for example. The casing 6 is provided with a high pressure port 4 connected to a pilot pressure source, a tank port 5 and two output ports 2, and the spools 1, 1 for changing the communication state of the output port 2 with respect to the high pressure port 4 and the tank port 5 are symmetrical. Install vertically. A cam 20 is tiltably attached to the top of the casing 6 by a shaft 22, and a plug 1 fixed to the casing 6 is attached.
Push rods 8 and 8 are installed on 6 and 16 so as to be slidable on the spool axis. The tops of the push rods 8, 8 are spherical, and the lower end planes of the adjusting screws 23, 23 screwed downward to the cam portions on both sides of the shaft 22 are brought into contact with this. A recess 9 is formed at the lower end of the push rod 8, and the spool 1 is placed in this recess.
The head 7 of is movably inserted. Then, a spring 14 is interposed between a spring seat 12 that abuts against the lower end of the head portion 7 via a contact plate 11 and a lower end of a spring chamber 13 of the casing 6, and a flange that projects from the lower end portion of the push rod 8 is provided. In the illustrated state in which the portion 15 is in contact with the lower end surface of the plug 16 and the spring 17 is interposed between the spring seat 12 and the intermediate step portion of the spool 1, the operating lever 21 of the cam 20 is in the neutral position, The annular groove 3 of the spool 1 is disconnected from the high pressure port 4 so as to communicate with the tank port 5. The annular groove 3 is always in communication with the output port 2 through the through holes 18 and 19.

Now, when the operating lever 21 is tilted to the right in the figure, the right push rod 8 is spring-loaded by the right adjusting screw 23.
Push down against 14. When the annular groove 3 descends to a position where it opens to the high pressure port 4, pressure oil is supplied from the high pressure port 4 to the right output port 2 and the pilot pressure rises. Since this pilot pressure acts on the end face of the spool 1 on the output port 2 side, the spring 17 is pushed up by the spool pressing force obtained by multiplying the pressure receiving area of the end face by the pilot pressure to push up the spool 1 to the annular groove 3. An attempt is made to cut off the communication with the high pressure port 4 and communicate with the tank port 5. However, since the push rod 8 tries to push down the spool 1 via the spring 17, the spring 17 is pinched and the spring load gradually increases, while the spool pushing force increases as the pilot pressure increases. Counter the spring load. That is, the pilot pressure guided to the output port 2 rises in proportion to the operating angle of the operating lever 22.

[Problems to be solved by the device]

However, since the adjusting screw 23 abuts on the spherical portion of the push rod 8 at the plane of the lower end thereof and pushes down the push rod 8 while tilting, the push rod 8 tilts under a lateral load. As a result, as shown by the arrow in FIG. 3, the push rod 8 may slide against the upper and lower edge portions 36 and 31 of the push rod guide surface 26, causing abrasion powder. In this case, since the abrasion powder from the edge portion 31 at the lower end falls downward, it does not enter the oil seal 29,
The abrasion powder from the edge portion 36 at the upper end is blocked by the dust seal 27 at the upper side and there is no escape, so that it enters the sliding gap between the push rod 8 and the push rod guide surface 26, and the push rod guide surface 26 As a result, the abrasion powder enters the oil seal 29, impairs the adhesion of the seal lip, and damages the seal lip portion to deteriorate the sealing function.

The present invention has been made in view of the above points, and an object thereof is to improve the durability of an oil seal arranged on a push rod guide surface of a pilot valve by a simple means.

[Means and Actions for Solving the Problems]

In order to achieve this object, the present invention provides a spool for guiding the push rod 8 slidably, a dust seal 27 on the uppermost portion of a bush rod guide surface 26, an oil seal 29 in the middle, and a spool for switching oil passages. In the pilot valve, 1 and the push rod 8 are arranged in series via a spring 17 so as to generate a pilot pressure according to an operating angle of an operating lever 21 contacting the push rod 8.
The push rod guide surface 26 is characterized in that a recess 28 for contacting the lower surface of the dust seal 27 and accumulating wear powder is formed.

When the push rod 8 slides under the lateral load due to the tilting operation of the operation lever 21, the push rod 8 comes into partial contact with the lower end edge portion 30 of the recess 28. The abrasion powder generated by this is accumulated in the concave portion 28 which is wider and has no resistance compared to the sliding gap between the push rod guide surface 26 and the push rod 8, so that the abrasion powder can be prevented from entering the sliding gap. In addition, the oil seal therebelow can be protected from abrasion powder.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. The structure and operation of the pilot valve shown in FIG. 2 have been described above. In this embodiment, a dust seal 27 is arranged at the uppermost portion of the push rod guide surface 26 of the plug 16 shown in FIG. 2 as shown in FIG.
An annular recess 28 is formed on the push rod guide surface 26 in contact with the lower surface of the dust seal 27. The oil seal 29 is arranged below the annular recess 28 at an appropriate interval. In such a configuration, when the push rod 8 is pushed downward by a lateral load due to the tilting of the operation lever 21, the push rod guide surface 26 and the one-sided portion are pushed with the lower end edge portion 30 of the annular recess 28. Rod guide surface 26
Is the bottom edge portion 31 of the. Then, the wear powder generated by the one-sided friction between the edge portion 30 and the push rod 8 is accumulated in the annular recess 28, and the wear powder generated by the one-sided friction between the edge portion 31 and the push rod 8 falls down and enters the oil seal 29. There is nothing to do.

Incidentally, the annular recess 28 may be formed only at a position where the push rod 8 is in one-side contact.

[Effect of device]

As described above, according to the present invention, the recess is provided in contact with the lower surface of the dust seal provided on the uppermost part of the push rod guide surface of the pilot valve, and the friction is generated between the lower end edge of the recess and the push rod. Since the abrasion powder is prevented from entering the sliding gap, the durability of the oil seal located below can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a push rod sealing device for a pilot valve according to an embodiment of the present invention, FIG. 2 is a vertical sectional view of a conventional pilot valve, and FIG. 3 is a vertical sectional view of a push rod sealing device for a conventional pilot valve. It is a side view. 1 ... Spool, 8 ... Push rod, 17 ... Spring,
20 …… Cam, 21 …… Operating lever, 26 …… Push rod guide surface, 27 …… Dust seal, 28 …… Concave, 29 …… Oil seal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisaaki Nishimune 234 Matsumoto, Higashiya-cho, Nishi-ku, Kobe-shi, Hyogo Kawasaki Saki Heavy Industries Co., Ltd.Nishi-Kobe factory (72) Inventor Nagahiro Mizoda 234 Matsumoto, Higashi-ku, Nishi-ku, Kobe-shi, Hyogo Address Kawasaki Heavy Industries, Ltd. Nishi-Kobe Plant (56) Reference JP 60-132180 (JP, A) Actual opening 61-156707 (JP, U) Actual opening Sho 61-182402 (JP, U) Actual opening 61-26693 (JP, Y2)

Claims (1)

[Scope of utility model registration request] 1. A dust seal is provided at the top of a push rod guide surface for slidably guiding a push rod, and an oil seal is provided in the middle, and a spool for switching an oil passage and the push rod are provided via a spring. In a pilot valve that is arranged in series to generate pilot pressure according to the operating angle of the operating lever that is in contact with the push rod, the push rod has a recess for contacting the lower surface of the dust seal and accumulating wear powder. Pilot valve characterized by being formed on the guide surface.