Device for spraying fluid on vehicle camera

A device for spraying a fluid on a vehicle camera includes a flow passage for connecting a suction portion with a discharge portion; a cylinder for communicating a pressure chamber in front of a piston with the flow passage; a drive mechanism for the piston including a motor; a first valve located between the suction portion and the pressure chamber, and functioning such that the first valve opens when the piston moves backward and closes when the piston moves forward; a second valve located between the pressure chamber and the discharge portion, and functioning such that the second valve opens when a pressure in the pressure chamber reaches a predetermined value by a forward movement of the piston; and a casing for housing the flow passage, the cylinder, the drive mechanism, the first valve, and the second valve to be combined with the vehicle camera.

FIELD OF TECHNOLOGY

The present invention relates to a device for spraying a fluid.

BACKGROUND ART

As a device for cleaning a lens by spraying a compressed air on the lens of a car-mounted camera, there is a device shown in Patent Document 1, wherein the cleaning device of the Patent Document 1 has a structure such that relative to a nozzle unit to be combined with the car-mounted camera, an air pump which is a separate member from the nozzle unit is connected by a hose. Namely, in the cleaning device of the Patent Document 1, when the cleaning device is attached to a vehicle, a space is required for disposing the air pump in addition to a space for disposing the nozzle unit.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

An object of the present invention is that in this type of device for spraying the fluid (cleaning device), as a unit having all functions for spraying the fluid on a light entrance portion of a vehicle camera, only by combining with the vehicle camera, a function of removing water droplets, dust, or the like attached to the light entrance portion can be easily and reliably added relative to the vehicle camera or the vehicle comprising the vehicle camera.

Means for Solving the Problems

In order to obtain the aforementioned object, in the present invention, a device for spraying a fluid on a vehicle camera comprises a suction portion for a fluid; a discharge portion for the fluid; a flow passage for connecting the suction portion with the discharge portion; a cylinder for communicating a pressure chamber in front of a piston with the flow passage; a drive mechanism for the piston including a motor; a first valve located between the suction portion and a communication portion between the pressure chamber and the flow passage, and functioning such that the first valve opens when the piston moves backward, and closes when the piston moves forward; a second valve located between the communication portion between the pressure chamber and the flow passage and the discharge portion, and functioning such that the second valve opens when a pressure in the pressure chamber reaches a predetermined value by a forward movement of the piston; and a casing for housing the above to be combined with the vehicle camera so that the fluid discharged from the discharge portion is sprayed on a light entrance portion of the vehicle camera.

One of the aspects of the present invention is that the drive mechanism for the piston comprises an urging device for urging the piston in a backward-movement direction; and a rotation member including a cam portion against which a back end portion of the piston abuts by an urging force, and rotation-driven by the motor, wherein when the rotation member rotates, the piston moves forth and back by a shape of the cam portion.

Also, one of the aspects of the present invention is that on a side portion of the piston, there is formed a circumferential groove, and a seal ring is mounted using the circumferential groove. Also, one of the aspects of the present invention is that there is formed a communication path between a front end portion facing the pressure chamber of the piston, and a portion positioned inside the seal ring in the circumferential groove.

Also, one of the aspects of the present invention is that the piston comprises the front end portion facing the pressure chamber; a neck portion positioned behind the front end portion; and a trunk portion positioned behind the neck portion. Also, one of the aspects of the present invention is that in the piston, there is mounted the seal ring using the neck portion, and the communication path is formed between the front end portion and the portion positioned inside the seal ring.

Also, one of the aspects of the present invention is that an inclined face is formed in the front end portion of the piston, and an entrance of the communication path is formed on the inclined face.

Also, one of the aspects of the present invention is that the second valve comprises a body portion including a large diameter chamber positioned in the discharge-portion side and a small diameter chamber positioned in the pressure-chamber side, and having a communication portion with the small diameter chamber inside the large diameter chamber as a valve seat; a valve member positioning a valve head portion inside the large diameter chamber, and inserting a shaft portion extending from the valve head portion into the small diameter chamber; and a holding device holding the valve member in a closing valve position wherein the valve head portion is closely attached to the valve seat until the pressure inside the pressure chamber reaches the predetermined value by the forward movement of the piston. Also, one of the aspects of the present invention is that an outer diameter of the shaft portion of the valve member and a diameter of the small diameter chamber are substantially equal, and one line of groove along a length direction of the shaft portion is formed at a side portion of the shaft portion.

Also, one of the aspects of the present invention is that the holding device comprises one of a magnet and a ferromagnetic material, to which the magnet is adsorbed, on the valve-member side, and the other of the magnet and the ferromagnetic material on the body-portion side.

Also, one of the aspects of the present invention is that the fluid is air.

Effect of the Invention

According to the present invention, in the device for spraying the fluid, as a unit having all functions for spraying the fluid on the light entrance portion of the vehicle camera, only by combining with the vehicle camera, a function of removing water droplets, dust, or the like attached to the light entrance portion can be easily and reliably added relative to the vehicle camera or the vehicle comprising the vehicle camera.

BEST MODES OF CARRYING OUT THE INVENTION

Hereinafter, with reference toFIG. 1toFIG. 19, typical embodiments of the present invention will be explained. A fluid spraying device A according to the present embodiment is combined relative to a vehicle camera C provided in a vehicle of a passenger car and the like so as to spray a fluid on a light entrance portion1of the vehicle camera C for removing water droplets, dust, or the like attached to the light entrance portion1by such fluid.

Typically, such fluid spraying device A is combined with the vehicle camera C with the light entrance portion1outside a vehicle interior of an automobile to be used.

In an illustrated example, such fluid spraying device A has a structure suitable for combining with the vehicle camera C forming an electron mirror for monitoring a back side of the automobile in place of a conventional door mirror and the like.

InFIG. 1, the reference C represents the vehicle camera, and the reference A represents the fluid spraying device. In the illustrated example, the vehicle camera C has a structure wherein a camera main member represented by the reference numeral2inFIG. 3is incorporated inside a casing represented by the reference numeral3(incidentally, in each drawing, incorporated components except for the camera main member2in the vehicle camera C are omitted in the drawings). The vehicle camera C is long in a front-and-back direction x, has a thickness of an up-and-down direction z, gradually increases a width in a right-and-left direction y as moving toward a back side B, and comprises the circular light entrance portion1on a back end face4. The light entrance portion1is positioned behind a lens portion2aof the camera main member2, and has a structure wherein a circular hole1ais closed by a shield1bwhich allows a light to pass through (seeFIG. 3). The back end face4includes a first face4apositioned on a vehicle-interior side, and a second face4bpositioned outside the first face4aand in front of the first face4a, and the light entrance portion1is formed in the second face4b. A step face4cis formed between the first face4aand the second face4b. In a portion wherein the step face4cand the second face4bcontact with each other, there is formed a blowing-out hole4dconnected to a discharge portion7of the fluid spraying device A through a tube5, and the fluid discharged from the discharge portion7of the fluid spraying device A is sprayed on the light entrance portion1through the blowing-out hole4d(seeFIG. 3). In a case that there is no shield1bas shown in the drawings, and the lens portion2aof the camera main member2forming the vehicle camera2is exposed at an outside of the casing3, the light entrance portion1becomes the lens portion2aitself.

As shown inFIG. 1toFIG. 4, the fluid spraying device A comprises:

(1) a suction portion6for the fluid;

(2) a discharge portion7for the fluid;

(3) a flow passage8for connecting the suction portion6with the discharge portion7;

(4) a cylinder11for communicating a pressure chamber10(a space inside the cylinder11to change a volume by a movement of a piston9) in front of the piston9with the flow passage8;

(5) a drive mechanism12for the piston9including a motor12a;

(6) a first valve14located between the suction portion6and a communication portion13between the pressure chamber10and the flow passage8, and functioning such that the first valve14opens when the piston9moves backward to open the flow passage8, and the first valve14closes when the piston9moves forward to close the flow passage8;

(7) a second valve15located between the communication portion13between the pressure chamber10and the flow passage8, and the discharge portion7, and functioning such that the second valve15opens when a pressure in the pressure chamber10reaches a predetermined value by a forward movement of the piston9to open the flow passage8; and

(8) a casing17for housing the above to be combined with the vehicle camera so that the fluid discharged from the discharge portion7is sprayed on the light entrance portion1of the vehicle camera C.

The illustrated example has a structure for sucking an air as the fluid from the suction portion6and spraying on the light entrance portion1from the discharge portion7. The fluid can be a cleaning liquid, and can be a fluid in which the cleaning liquid is mixed with the air as well.

In the illustrated example, the fluid spraying device A is formed by incorporating the aforementioned elements (1) to (7) into the flat casing17which is long in the front-and-back direction x, is short in the right-and-left direction y, and has the thickness of the up-and-down direction z.

In the illustrated example, the fluid spraying device A is combined with the vehicle camera C such that one thickness-side side face17alocated along a length direction of the casing17thereof comes into contact with a side face3apositioned on the vehicle-interior side in the casing of the vehicle camera C (seeFIG. 2andFIG. 3).

Also, in the illustrated example, the casing17of the fluid spraying device A is formed by combining a lower portion17bwith an upper portion17c, which are separable approximately at a middle position in a thickness direction thereof.

The piston9moves along the front-and-back direction x.

As shown inFIG. 4, the suction portion6is provided on a side opposite to a side where the vehicle camera C is combined by sandwiching a virtual center line L1including a center shaft of the piston9, and in an area which becomes the back side B more than a virtual straight line L2orthogonal to the center line L1and passing the communication portion13between the pressure chamber10and the flow passage8.

The discharge portion7is provided on the side where the vehicle camera C is combined by sandwiching the center line L1, and in the area which becomes the back side B more than the straight line L2.

The flow passage8includes a center flow passage8aalong the center line L1. A cross-sectional area of the center flow passage8ais smaller than a cross-sectional area of the pressure chamber10, and the center flow passage8acommunicates with the pressure chamber10at a front end thereof. Namely, the front end of the center flow passage8abecomes the communication portion13between the pressure chamber10and the flow passage8.

The suction portion6is formed in a back end face17dof the casing17(seeFIG. 1). The suction portion6and the center flow passage8acommunicate by a first lateral flow passage8b(seeFIG. 4). In the first lateral flow passage8b, a back end thereof becomes the suction portion6, and a front end8cthereof communicates with the center flow passage8ain a position located slightly on the back side B more than the front end (communication portion13) of the center flow passage8a(seeFIG. 4).

The first valve14is formed inside the first lateral flow passage8b. A body portion14aforming the first valve14is an enlarged-diameter chamber which becomes one portion of the first lateral flow passage8b, and a valve member14cforming the first valve14is housed inside the body portion14ato be movable forth and back. A through hole formed between a back inner wall14bin the body portion14aand the back end face17dof the casing17functions as the suction portion6, and the back inner wall14bin the body portion14afunctions as a valve seat. The valve member14cincludes a head portion14dhaving a disk shape, and a leg portion14eprotruding forward from a center on a front side of the head portion14. In a state wherein the head portion14dhaving a diameter larger than that of the through hole as the suction portion6is positioned inside the body portion14a, and the leg portion14eis inserted into a small diameter portion8dof the first lateral flow passage8blocated between the body portion14aand the front end8cof the first lateral flow passage8b, the valve member14cis positioned inside the first lateral flow passage8b. In case the piston9moves backward, in the illustrated example, when the piston9moves to a front side F so as to enlarge the volume of the pressure chamber10, by a pressure change in the pressure chamber10, the valve member14cforming the first valve14moves to the front side F, and separates from the back inner wall14bas the valve seat of the body portion14aso as to open the suction portion6, so that an external air is sucked into the pressure chamber10through the first lateral flow passage8band the center flow passage8a. On the other hand, In case the piston9moves forward, in the illustrated example, when the piston9moves to the back side B so as to reduce the volume of the pressure chamber10, by the pressure change in the pressure chamber10, the valve member14cforming the first valve14moves to the back side B, and is closely attached to the back inner wall14bas the valve seat of the body portion14aso as to close the suction portion6. Namely, the first valve14is a one-way valve.

The cylinder11is provided in an area which becomes the front side F more than the straight line L2.

On the other hand, in a side portion9aof the piston9, there is formed a circumferential groove9bsurrounding the center shaft x, and there is mounted a seal ring9cto seal between the piston9and the cylinder11using the circumferential groove9b(seeFIG. 7andFIG. 8).

Therewith, there are formed communication paths9f(ventilation paths) between a front end portion9dfacing the pressure chamber10of the piston9and a portion9epositioned inside the seal ring9cin the circumferential groove9b(seeFIG. 8).

In the illustrated example, the piston9is formed by a short column-shaped portion9hhaving a diameter slightly smaller than an inner diameter of the cylinder11on a front-end-portion9dside thereof. The circumferential groove9bis formed in a side portion of the short column-shaped portion9h. An outer diameter of the seal ring9cis substantially equal to the inner diameter of the cylinder11, and an inner diameter of the seal ring9cis slightly smaller than an outer diameter of the short column-shaped portion9h.

Three communication paths9fare provided at equal intervals between adjacent communication paths9fin a direction surrounding the center shaft of the piston9. All of the respective communication paths9fare through holes continuing in such a way so as to be in parallel with the center line L1.

When the piston9moves forward (moves forth), a pressure inside the circumferential groove9bon an inner side of the seal ring9cis increased as well in a manner similar to the pressure chamber10by the communication paths9f, so that the seal ring9cis elastically deformed in a direction of enlarging the outer diameter so as to enhance a sealing property between the piston9and an inner wall11aof the cylinder11.

On the other hand, when the piston9moves backward (moves back), the pressure inside the circumferential groove9bon the inner side of the seal ring9cis reduced as well in a manner similar to the pressure chamber10by the communication paths9f, so that the seal ring9cis elastically returned in a direction of reducing the outer diameter, and when the piston9moves backward, there is no resistance generated between the seal ring9cand the inner wall11aof the cylinder11as little as possible. Thereby, an excessive force is not required for a backward movement of the piston9.

Also, in the present embodiment, in the front end portion9dof the piston9, there is formed an inclined face9i, and in the inclined face9i, there are formed entrances9gof the communication paths9f. In the illustrated example, the front end portion9dincludes a top face9jorthogonal to the center shaft of the piston9at a center, and the inclined face9ihaving a circumference shape in which a side of the top face9jis located as an inclination top is located between the top face9jand the side portion9aof the piston9. Thereby, an area of each entrance9gof the communication path9fis made larger than a cross-sectional area of the other portions, so that when the piston9moves forward, the communication path9fcan effectively take in the air.

The drive mechanism12for the piston9comprises an urging device12burging the piston9in a backward-movement direction; and a rotation member12ccomprising a cam portion12dagainst which a back end portion9kof the piston9abuts by the urging force to be rotation-driven by the motor12a(seeFIG. 4andFIG. 5). Then, when the rotation member12crotates, the piston9is set so as to move forth and back by a shape of the cam portion12d.

In the illustrated example, the motor12aforming the drive mechanism12is disposed in such a way so as to line up with the piston9on the side opposite to the side where the vehicle camera C is combined by sandwiching the center line L1(seeFIG. 4).

The rotation member12cis disposed such that a rotation shaft S thereof is located along the up-and-down direction z on the center line L1between the back end portion9kprotruding to the front side F from the cylinder11in the piston9and a front end face17eof the casing17(seeFIG. 2toFIG. 4).

In the illustrated example, by engaging a gear12kengaging a worm12jintegrated with an output shaft of the motor12awith a gear12mengaging a gear portion12hformed on an outer periphery of the rotation member12c, the rotation member12crotates by driving the motor12a(seeFIG. 3andFIG. 4)

On one face of the rotation member12c, in the illustrated example, on a lower face12i, there is formed the cam portion12d. The cam portion12dhas a structure of protruding from the lower face12iof the rotation member12c, and there is formed a cam face12eas a circumferential step face between the cam portion12dand the lower face12iof the rotation member12c. The cam face12eincludes a first portion12fhaving a maximum distance from the rotation shaft S of the rotation member12c; and a second portion12gpositioned on a side opposite to the first portion12fby sandwiching the rotation shaft of the rotation member12c.

In the illustrated example, the urging device12bis a compression coil spring (seeFIG. 3andFIG. 4). Obviously, it is sufficient that such urging device12bcan urge the piston9in the backward-movement direction, and various types of springs in addition to the compression coil spring, or an elastic member providing a repulsive force in a fashion similar to the springs, may be used. One end of the spring is pressed against a step11bformed in a portion surrounding an opening opposite to a pressure-chamber10side of the cylinder11, and the other end of the spring is pressed against a flange portion9mformed between the front end portion9dand the back end portion9kof the piston9(seeFIG. 4,FIG. 7, andFIG. 8).

In the illustrated example, the back end portion9kof the piston9has a plate shape having the thickness of the up-and-down direction z, and enters beneath the lower face12iof the rotation member12cso as to always press against the cam face12eof the cam portion12dby the urging force of the urging device12b(seeFIG. 5andFIG. 7).

When the rotation member12cis located in a rotation position wherein the second portion12gof the cam face12epresses against the back end portion9kof the piston9, the piston9comes to a position wherein the piston9is moved backward most by the urging force of the compression coil spring. On the other hand, when the rotation member12cis located in a rotation position wherein the first portion12fof the cam face12epresses against the back end portion9kof the piston9, the piston9comes to a position wherein the piston9is moved forward most, so that the compression coil spring comes to a most compressed state.

The forward movement of the piston9is carried out by an operation of the cam portion12dby a rotation of the rotation member12c, and the backward movement of the piston9is carried out by an operation of the urging device12baccompanied by the rotation of the rotation member12c. When the piston9reciprocates, comparing with a case using a crank shaft, there are no top and bottom dead centers, and even when the rotation member12cis located at any rotation position, at the same time when the motor12ais driven, the piston9can be smoothly operated. Also, since the excessive force for the backward movement of the piston9is not required by the communication paths9fof the piston9, the urging force of the urging device12bcan be minimized. Therefore, a load of the motor12awhen the piston9moves forward can be minimized as well.

Also, the second valve15is formed inside the center flow passage8a(seeFIG. 4andFIG. 5).

As shown inFIG. 11andFIG. 12, the second valve15comprises a body portion15′ including a large diameter chamber15apositioned on the discharge-portion7side and a small diameter chamber15bpositioned on the pressure-chamber10side, wherein a communication portion with the small diameter chamber15binside the large diameter chamber15ais a valve seat15c; a valve member15hpositioning a valve head portion15iinside the large diameter chamber15a, and inserting a shaft portion15jextending from the valve head portion15iinto the small diameter chamber15b; and a holding device16holding the valve member15hin a closing valve position wherein the valve head portion15iis closely attached to the valve seat15cuntil the pressure in the pressure chamber10reaches the predetermined value by the forward movement of the piston9.

Also, an outer diameter of the shaft portion15jof the valve member15hand a diameter of the small diameter chamber15bare substantially equal, and one line of groove15k(ventilation groove) is formed across a whole length thereof along a length direction of the shaft portion15jat a side portion of the shaft portion15j.

As shown inFIG. 11andFIG. 12, in the illustrated example, the body portion15′ is formed by combining a main member portion15dwith a cap15e. The main member portion15dincludes the small diameter chamber15bformed along the center line L1at the front side F, and the large diameter chamber15aat the back side B thereof. Also, at a side portion of the large diameter chamber15a, there is communicated a tube portion15fextending in a direction orthogonal to the center line L1, and a tip of the tube portion15ffunctions as the discharge portion7. The valve seat15cbecomes a step face inside the main member portion15d, which is formed by a size difference between the large diameter chamber15aand the small diameter chamber15b, and surrounds an opening facing the large diameter chamber15afor communicating the large diameter chamber15aand the small diameter chamber15b. After the valve member15his housed inside the main member portion15din such a way so as to form the large diameter chamber15abetween the valve member15hand the valve seat15c, the cap15eis combined with the main member portion15d.

The valve member15hincludes a valve head portion15ihaving a disk shape, and a shaft portion15jhaving a cylinder shape protruding to the front side F from a center on one face side of the valve head portion15i. An outer diameter of the valve head portion15ihas a size which can be housed in the large diameter chamber15a, and cannot be housed in the small diameter chamber15b. In a state wherein the valve head portion15iis positioned inside the large diameter chamber15a, and the shaft portion15jis inserted into the small diameter chamber15b, the valve member15his held inside the body portion15′ to be movable forth and back. Also, in the illustrated example, in a base portion of the shaft portion15j, there is fitted a seal ring15mforming one portion of the valve head portion15i, and the seal ring15mcontacts the valve seat15c.

In the present embodiment, until the pressure in the pressure chamber10reaches the predetermined value by the forward movement of the piston9, the valve member15his held by the holding device16in the closing valve position wherein the valve head portion15iis closely attached to the valve seat15c.

When the pressure in the pressure chamber10reaches the predetermined value, the holding by the holding device16is released, the valve member15hmoves to an opening valve position, in the illustrated example, to the back side B, and a compressed air is blown out through the discharge portion7. In such opening valve state, an air-passing portion of the small diameter chamber15bof the body portion15′ is substantially limited to one line of groove15kformed in the shaft portion of the valve member15hso as to effectively enhance a flow speed of the air blowing out.

In the present embodiment, the holding device16comprises one of a magnet and a ferromagnetic material, to which the magnet is adsorbed, on the valve-member15hside, and the other of the magnet and the ferromagnetic material on the body-portion15′ side.

In the illustrated example, a first columnar member16afits into the shaft portion15jof the valve member15hsuch that an end face of the first columnar member16abecomes the same face with a tip of the shaft portion15j.

Also, inside the small diameter chamber15bof the body portion15′, there is fitted a second columnar member16b. In the illustrated example, inside the small diameter chamber15b, there are formed three ribs15gcontinuing in a direction along the center line L1in such a way so as to become a communication path forming one portion of the center flow passage8abetween adjacent ribs15gin a direction surrounding the center line L1(seeFIG. 13). Using tips of the three ribs15g, the second columnar member16bfits into the small diameter chamber15b. An end face of the second columnar member16bis positioned at a portion wherein the tip of the shaft portion15jof the valve member15his positioned in the closing valve position.

One of the first columnar member16aand the second columnar member16bis the magnet, and the other is the ferromagnetic material.

Thereby, in the present embodiment, until the pressure in the pressure chamber10reaches the predetermined value by the forward movement of the piston9, the valve member15his held by the holding device16in the closing valve position wherein the valve head portion15iis closely attached to the valve seat15c. Then, at the moment when the pressure in the pressure chamber10exceeds the predetermined value, the valve member15hmoves in the opening valve position so as to blow the air inside the pressure chamber10from the discharge portion7with a predetermined flow speed. Also, when the first blowing of the air is completed, the valve member15hcan move to the closing valve position immediately by an adsorption force of the magnet.

The fluid spraying device A according to the present embodiment has a structure wherein the load of the motor12awhen the piston9moves forward is minimized, and the flow speed of the air blowing out is effectively enhanced as mentioned above, so that the piston9, the cylinder11, and the motor12acan be downsized as small as possible without any difficulty. Accordingly, the fluid spraying device A according to the present embodiment has characteristics providing the downsizing of the fluid spraying device A as a whole.

The fluid spraying device A according to the present embodiment is a unit having all functions for spraying air on the light entrance portion1of the vehicle camera C inside the casing, and by combining with the vehicle camera, a function of removing the water droplets, the dust, or the like attached to the light entrance portion1can be easily and reliably added relative to the vehicle camera C or the vehicle comprising the vehicle camera C.

An example shown inFIG. 14toFIG. 16is a structural modified example (hereinafter, called a second example) of the piston in the example shown inFIG. 1toFIG. 13. In the second example, four communication paths9f′ corresponding to the communication paths9fin the example shown inFIG. 1toFIG. 13are provided at equal intervals between adjacent communication paths9f′ in the direction surrounding the center shaft of the piston9. All of the respective communication paths9f′ are the through holes continuing in such a way so as to be parallel to the center line L1.

In the second example, the piston9comprises the front end portion9dfacing the pressure chamber10; a neck portion9opositioned behind the front end portion9d; and a trunk portion9ppositioned behind the neck portion9o. Then, using the neck portion9o, the seal ring9cis mounted on a side portion of the piston9.

In the second example, the neck portion9oconnects the front end portion9dwith the trunk portion9p, and comprises four support portions9qof the seal ring9cpositioned on a circular arc of a virtual circle r having a diameter slightly smaller than an outer diameter of the front end portion9dand the trunk portion9pat intervals between adjacent support portions9qin the direction surrounding the center shaft of the piston9. The respective support portions9qare formed by outer ends9sof rib-shaped portions9rprotruding in a radial direction from a center of the neck portion9o, and between adjacent support portions9q, there is respectively formed a space9ubetween the seal ring9cand the center of the neck portion9o. Four spaces9uare formed, and each space9uhas the same width.

In the second example, the communication paths9f′ are formed in such a way so as to range between the front end portion9dand the space9u, and four spaces9urespectively communicate with the pressure chamber10through the communication paths9f′.

Thereby, in the second example, when the piston9moves forward (moves forth), a pressure in the space9uon the inner side of the seal ring9cis increased by the communication paths9f′ with small disparity at each position in a circumferential direction of the seal ring9c, and the outer diameter of the seal ring9ccan be enlarged with the small disparity at each position in the circumferential direction of the seal ring9c.

An example shown inFIG. 17toFIG. 19is a further modified example (hereinafter, called a third example) of the structure of the piston9in the example shown inFIG. 1toFIG. 13. In the third example, the communication path9f′ corresponding to the communication path9fin the first example is formed in a center shaft position of the piston9.

In the third example, the piston9comprises the front end portion9dfacing the pressure chamber10; the neck portion9opositioned behind the front end portion9d; and the trunk portion9ppositioned behind the neck portion9o. Then, using the neck portion9o, the seal ring9cis mounted on the side portion of the piston9.

In the third example, inside the communication path9f′, there is positioned a column portion9vwherein an outer diameter is reduced more than a diameter of the communication path9f′. The column portion9vis formed in such a way so as to integrate a base portion9wwith the trunk portion9pand protrude to the pressure-chamber10side along the center shaft of the piston9. The column portion9vhas a needle shape having a circular shape in a cross section and gradually narrowing the outer diameter as approaching a tip9x, and between the column portion9vand an inner face of the communication path9f′, there is formed an interval approximately equal at each position surrounding the center shaft of the piston9.

In the third example, the neck portion9oconnects the front end portion9dwith the trunk portion9p, and comprises four support portions9qof the seal ring9cpositioned on the circular arc of the virtual circle r having the diameter slightly smaller than the outer diameter of the front end portion9dand the trunk portion9pat the intervals between the adjacent support portions9qin the direction surrounding the center shaft of the piston9. The respective support portions9qare formed by the outer ends9sof the rib-shaped portions9rprotruding in the radial direction from the column-portion9vside. Between an inner end9tof each rib-shaped portion9rand the column portion9v, there is formed a gap. Between adjacent rib-shaped portions9r, respectively, there is formed the space9ubetween the seal ring9cand the column portion9v. Four spaces9uare formed, and each space9uhas the same width.

In the third example, by the communication paths9f′ formed as mentioned above, the four spaces9urespectively communicate with the pressure chamber10.

Thereby, in the third example, when the piston9moves forward (moves forth), the pressure in the space9uon the inner side of the seal ring9ccan be increased by the communication paths9f′ with the small disparity at each position in the circumferential direction of the seal ring9c, and the outer diameter of the seal ring9ccan be enlarged with the small disparity at each position in the circumferential direction of the seal ring.

Incidentally, obviously, the present invention is not limited to the embodiments explained in the above, and includes all embodiments which can obtain the object of the present invention.

EXPLANATION OF SYMBOLS

Incidentally, all contents of the specifications, claims, drawings, and abstracts of Japanese Patent Applications No. 2017-008155 filed on Jan. 20, 2017, and No. 2017-182228 filed on Sep. 22, 2017 are cited in their entireties herein and are incorporated as a disclosure of the specification of the present invention.