Patent Description:
Fluid valves include hydraulic valves (control valves), which are used in hydraulic excavators and other construction machines. A construction machine includes a hydraulic actuator for driving an arm and a circling structure, a hydraulic pump for feeding hydraulic oil to the hydraulic actuator, and a hydraulic circuit connecting the hydraulic actuator and the hydraulic pump. The hydraulic actuator is, for example, a hydraulic cylinder or motor. The hydraulic circuit is constituted by a plurality of hydraulic valves.

The hydraulic valves control the flow of the hydraulic oil fed to the hydraulic actuator. Specifically, the flow of the hydraulic oil fed to the hydraulic actuator is controlled by driving the spools provided in the hydraulic valves. The hydraulic circuit includes a filter for preventing foreign objects from entering the hydraulic actuator and valves. The hydraulic oil is fed to the hydraulic actuator and valves after filtered through the filter. <CIT>, <CIT>, <CIT>, <CIT>, <CIT> disclose fluid valves having a housing with a spool hole and a spool movably provided in the spool hole.

The above-described conventional technology requires an independent filter to filter the hydraulic oil. As a result, the hydraulic circuit as a whole has an increased number of parts, which complicates the production management.

The present invention provides a fluid valve that allows a reduced number of parts, thereby facilitating the production management.

The aforementioned object is achieved by a fluid valve having the features of claim <NUM>.

The implementation eliminates the need for a separate filter. No filters are used. The fluid valve thus allows a reduced number of parts, thereby facilitating the production management.

In the invention, the filter has a minute gap provided by the flow channel formed between the spool hole and the outer surface of the spool, and a radial width of the minute gap is sized to inhibit passage of foreign matter of a desired size.

In the invention, the minute gap constitutes a given part of a gap formed between the spool hole and the outer surface of the spool, and the minute gap has a greater radial width than a remaining part of the gap formed between the spool hole and the outer surface of the spool since a corresponding part of the spool hole has a large inner diameter or a corresponding part of the outer surface of the spool has a small outer diameter.

In the implementation, at least one of an inner surface of the spool hole or the outer surface of the spool between which the flow channel is formed may be inclined with respect to an axial direction such that the radial width of the flow channel progressively decreases toward the drain port.

In the implementation, the liaison channel may have: a fluid inlet chamber extending along a central axis of the spool, the fluid inlet chamber being in communication with the connection recess; and a discharge recess defined in the outer surface of the spool, the discharge recess being positioned closer to the drain port than is the connection recess, the discharge recess being in communication with the fluid inlet chamber. The flow channel may extend between the discharge recess and an end of the spool facing the drain port.

In the implementation, the liaison channel may have: a discharge chamber extending along an axis of the spool, the discharge chamber being formed at the end of the spool facing the drain port; and an inlet recess defined in the outer surface of the spool, the inlet recess being positioned closer to the drain port than is the discharge recess, the inlet recess being in communication with the discharge chamber. The flow channel may extend between the discharge recess and the inlet recess.

In the implementation, the fluid valve may include a throttle provided in the discharge chamber, the throttle being configured to regulate an amount of hydraulic fluid discharged from the discharge chamber to the drain port.

In the implementation, the fluid valve may include an elastic member provided in the spool hole and lying between the drain port and the spool, the elastic member being configured to force the spool away from the drain port. The spool may have another connection recess defined in the outer surface, the other connection recess being positioned on an opposite side to the drain port with respect to the connection recess, and the other connection recess may be disconnected from the fluid inlet chamber.

In the implementation, the fluid valve may include an elastic member provided in the spool hole and lying between the drain port and the spool, the elastic member being configured to force the spool away from the drain port, wherein the spool has: another connection recess defined in the outer surface of the spool, the other connection recess being positioned on an opposite side to the drain port with respect to the connection recess, the other connection recess being configured to establish communication between the feeding port and the discharge port; a fluid inlet chamber extending along a central axis of the spool, the fluid inlet chamber being in communication with the connection recess; and a discharge recess defined in the outer surface of the spool, the discharge recess being positioned closer to the drain port than is the connection recess, the discharge recess being in communication with the fluid inlet chamber, wherein, between the discharge recess and an end of the spool facing the drain port, the flow channel is formed.

The fluid valve can be used as a timer valve in, for example, a construction machine. The timer valve is used in a brake device provided in a hydraulic actuator, which generates high inertia load. The timer valve no longer needs filters. Since the timer valve allows a reduced number of parts, the production management can be facilitated.

The fluid valves described above allow a reduced number of parts, thereby facilitating the production management.

The embodiments of the present invention will be hereinafter described with reference to the drawings.

<FIG> schematically shows the configuration of a timer valve <NUM>. In the subsequent drawings, the scale is appropriately changed for the sake of better understanding. The timer valve <NUM> is used in a construction machine such as a hydraulic excavator, which is not shown. The timer valve <NUM> may control a mechanical brake <NUM>, which can be provided in the construction machine, such that the mechanical brake <NUM> may operate (apply a braking force) at a point of time later than when an operator manipulates the mechanical brake <NUM>.

The mechanical brake <NUM> applies a braking force to a hydraulic actuator such as a hydraulic motor installed on the construction machine. Although not shown in the drawings, the hydraulic actuator is designed to enable the construction machine to travel or to rotate a circling structure. The mechanical brake <NUM> generates the braking force, for example, by using a constant spring force. The mechanical brake <NUM> stops applying the braking force in response to hydraulic oil fed to the mechanical brake <NUM>. The timer valve <NUM> can keep the hydraulic actuator in operation for a while due to a large inertia force after the flow of the hydraulic oil to the hydraulic actuator is stopped.

As shown in <FIG>, the timer valve <NUM> includes a housing <NUM>, a spool <NUM> provided in the housing <NUM>, and a coil spring <NUM>. The housing <NUM> has a spool hole <NUM>, a feeding port <NUM>, and a discharge port <NUM>. The spool <NUM> and coil spring <NUM> are housed in the spool hole <NUM>, the hydraulic oil (hydraulic fluid) is fed through the feeding port <NUM> and discharged through the discharge port <NUM>.

In the housing <NUM>, a drain chamber <NUM> is continuous from the spool hole <NUM> and formed next to the spool hole <NUM> in a first direction (the left side in <FIG>). The drain chamber <NUM> and spool hole <NUM> are coaxially arranged. The drain chamber <NUM> has a slightly greater inner diameter than the spool hole <NUM> via a step 8a (see <FIG>). A drain port <NUM> is formed at an end of the drain chamber <NUM> facing the first direction. The drain chamber <NUM> is connected to a tank <NUM> through the drain port <NUM>. The spool hole <NUM> is closed by a plug <NUM> at its end facing a second direction (the right side in <FIG>), which is oppositely directed to the first direction (at the end opposite to the end where the drain port <NUM> is formed).

The feeding port <NUM> is formed such that its axial direction is orthogonal to the axial direction of the spool hole <NUM>. The feeding port <NUM> is continuous from the spool hole <NUM>. The feeding port <NUM> is connected to an operating unit <NUM>, which is operated by the operator of the construction machine. The operating unit <NUM> is connected to a hydraulic pump <NUM>. The hydraulic pump <NUM> is used to generate a pressure (pilot pressure) to be applied to the hydraulic oil through the operating unit <NUM>, for example. The pressure resulting from the operation through the operating unit <NUM> acts upon the hydraulic oil fed through the feeding port <NUM>.

The discharge port <NUM> is formed on the opposite side of the feeding port <NUM> with the spool hole <NUM> being sandwiched therebetween. The discharge port <NUM> is continuous from the spool hole <NUM>. The part of the discharge port <NUM> that is near the spool hole <NUM> is coaxially arranged with the feeding port <NUM>. The part of the discharge port <NUM> that is distant from the spool hole <NUM> is connected to the mechanical brake <NUM> provided in the construction machine.

The spool <NUM> is slidably housed in the spool hole <NUM>. The outer diameter of the spool <NUM> is slightly smaller than the inner diameter of the spool hole <NUM>. Two connection recesses <NUM> and <NUM> (a first connection recess <NUM> and a second connection recess <NUM>) are formed on the outer surface 3a of the spool <NUM>. The first connection recess <NUM> of the two connection recesses <NUM> and <NUM> is mentioned as an example of a connection recess recited in the claims. The second connection recess <NUM> of the two connection recesses <NUM> and <NUM> is mentioned as an example of another connection recess recited in the claims. The connection recesses <NUM> and <NUM> are annularly formed along the entire outer surface 3a of the spool <NUM>.

Of the two connection recesses <NUM> and <NUM>, the first connection recess <NUM> is located at the center in the axial direction of the spool <NUM>. Of the two connection recesses <NUM> and <NUM>, the second connection recess <NUM> is located on the second direction side with respect to the first connection recess <NUM> (on the opposite side to the drain port <NUM> and drain chamber <NUM>). A first land <NUM> is defined between the two connection recesses <NUM> and <NUM>.

The spool <NUM> has a liaison channel <NUM> formed therein for establishing communication between the first connection recess <NUM> and the drain port <NUM> (drain chamber <NUM>). The liaison channel <NUM> mainly includes a hydraulic oil inlet chamber <NUM> extending along the central axis of the spool <NUM>, and a discharge recess <NUM> and a channel <NUM> formed in the outer surface 3a of the spool <NUM>. The hydraulic oil inlet chamber <NUM> originates at an end 3b of the spool <NUM> facing the second direction and terminates at a site slightly off, toward the first direction, the site where the discharge recess <NUM> is formed. In other words, the hydraulic oil inlet chamber <NUM> is open at the end 3b of the spool <NUM> facing the second direction.

The discharge recess <NUM> is annularly formed along the entire outer surface 3a of the spool <NUM>. The discharge recess <NUM> is located in a half of the spool <NUM> facing the first direction (closer to the drain port <NUM>). A second land <NUM> is defined between the first connection recess <NUM> and the discharge recess <NUM>.

The spool <NUM> has two connection channels <NUM> connecting the first connection recess <NUM> and the hydraulic oil inlet chamber <NUM>. The two connection channels <NUM> are formed such that their axial direction is orthogonal to the axial direction of the spool <NUM>. The two connection channels <NUM> sandwich the hydraulic oil inlet chamber <NUM> and are coaxially arranged.

The spool <NUM> has no connection channels connecting the second connection recess <NUM> and the hydraulic oil inlet chamber <NUM>. This means that the second connection recess <NUM> is completely separated from the hydraulic oil inlet chamber <NUM>. The spool <NUM> has four discharge channels <NUM> connecting the discharge recess <NUM> and the hydraulic oil inlet chamber <NUM>. The four discharge channels <NUM> are formed such that their axial direction is orthogonal to the axial direction of the spool <NUM>. The four discharge channels <NUM> are arranged at equal intervals in the circumferential direction of the spool <NUM>.

<FIG> is an enlarged view of the part II of <FIG>. As shown in <FIG> and <FIG>, a flow channel <NUM> extends between the discharge recess <NUM> and the end 3c of the spool <NUM> facing the first direction. The spool <NUM> has a reduced diameter portion <NUM> originating at the discharge recess <NUM> of and terminating at the end 3c of the spool <NUM> facing the first direction. The outer diameter of the reduced diameter portion <NUM> is slightly less than the outer diameters of the other portion of the spool <NUM>. The flow channel <NUM> is formed between the outer surface 24a of the reduced diameter portion <NUM> and the inner surface 5a of the spool hole <NUM>. The flow channel <NUM> is annularly shaped.

A minute gap G is provided by the flow channel <NUM> and extends in the radial direction. The radial width of the minute gap G, in other words, the size of the minute gap G formed between the outer surface 24a of the reduced diameter portion <NUM> and the inner surface 5a of the spool hole <NUM> is approximately equal to a filter pore size of <NUM>, for example. The flow channel <NUM> thus serves as a filter <NUM> for filtering out foreign objects from the hydraulic oil flowing through the liaison channel <NUM>. Stated differently, the flow channel <NUM> serves as the filter <NUM> to stop intrusion of foreign matter through the drain port <NUM>. At the same time, the flow channel <NUM> also serves as an orifice (throttle) <NUM> for regulating the flow rate of the hydraulic oil from the discharge recess <NUM> to the drain port <NUM> (this will be described in detail below).

In the drain chamber <NUM>, a coil spring <NUM>, which is slightly compressed, is housed. The spring force of the coil spring <NUM> forces the spool <NUM> toward the second direction. With no load being applied in the timer valve <NUM>, the coil spring <NUM> causes the end 3b of the spool <NUM> facing the second direction to abut the plug <NUM>. The expression "no load being applied" means that no pressure is applied by the hydraulic oil to the hydraulic oil inlet chamber <NUM> (this will be described in detail below).

In this case, the feeding and discharge ports <NUM> and <NUM> of the housing <NUM> are aligned in the radial direction with the first connection recess <NUM> of the spool <NUM>. In other words, the feeding and discharge ports <NUM> and <NUM> are in communication with the first connection recess <NUM>. Since the first connection recess <NUM> is annularly formed along the entire outer surface 3a of the spool <NUM>, the feeding port <NUM> is connected to the discharge port <NUM> via the first connection recess <NUM>.

The following now describes how the timer valve <NUM> works. As shown in <FIG>, with no hydraulic oil being fed to the timer valve <NUM> (no load being applied), the mechanical brake <NUM> applies a braking force onto the hydraulic actuator, which is not shown. If the operating unit <NUM> is operated, the hydraulic oil is fed to the feeding port <NUM>. The hydraulic oil then flows through the first connection recess <NUM>, to flow into the discharge port <NUM>. The hydraulic oil further flows into the mechanical brake <NUM>. The pressure of the hydraulic oil can stop the braking force applied by the mechanical brake <NUM>.

<FIG> shows how the timer valve <NUM> works. <FIG> corresponds to <FIG>. As shown in <FIG> and <FIG>, the hydraulic oil fed to the feeding port <NUM> flows through the first connection recess <NUM> and connection channels <NUM>, and then finally flows into the hydraulic oil inlet chamber <NUM> (see the arrow Y1 in <FIG>). This results in raising the pressure in the hydraulic oil inlet chamber <NUM>. Here, the hydraulic oil inlet chamber <NUM> is open at the end 3b of the spool <NUM> facing the second direction. The increased pressure overcomes the spring force of the coil spring <NUM>, so that the spool <NUM> can slide in the first direction (see the arrow Y2 in <FIG>).

As a result, the feeding port <NUM> is connected to the discharge port <NUM> via the second connection recess <NUM>. Since the second connection recess <NUM> is completely separated from the hydraulic oil inlet chamber <NUM>, the hydraulic oil does not flow into the hydraulic oil inlet chamber <NUM>. Meanwhile, the hydraulic oil keeps flowing into the mechanical brake <NUM> via the discharge port <NUM>, so that the braking by the mechanical brake <NUM> remains stopped.

The hydraulic oil flowing into the hydraulic oil inlet chamber <NUM> also flows into the discharge channels <NUM> and discharge recess <NUM>, passes through the flow channel <NUM>, and flows into the drain chamber <NUM> (see the arrow Y3 in <FIG>). The hydraulic oil in the drain chamber <NUM> is fed back to the tank <NUM> through the drain port <NUM>. Since the hydraulic oil in the hydraulic oil inlet chamber <NUM> is fed back, the pressure in the hydraulic oil inlet chamber <NUM> drops.

As a result, the spring force of the coil spring <NUM> overcomes the pressure in the hydraulic oil inlet chamber <NUM>, so that the spool <NUM> again slides toward the second direction. This again connects the first connection recess <NUM> with the feeding and discharge ports <NUM> and <NUM>, thereby allowing the hydraulic oil to flow into hydraulic oil inlet chamber <NUM>. The flow channel <NUM> functions as the orifice <NUM>, which can regulate the flow rate of the hydraulic oil from the hydraulic oil inlet chamber <NUM> into the drain chamber <NUM>. The flow channel <NUM> also serves as the filter <NUM>. The flow channel <NUM> inhibits the passage of foreign matter, which effectively filters out foreign objects from the hydraulic oil flowing from the hydraulic oil inlet chamber <NUM> into the drain chamber <NUM>.

As described above, while the hydraulic oil is fed through the feeding port <NUM>, balance is established between the hydraulic oil fed from the hydraulic oil inlet chamber <NUM> back to the tank <NUM> and the hydraulic oil fed to the hydraulic oil inlet chamber <NUM>, thereby enabling the spool <NUM> to stay at a predetermined position. When the spool <NUM> is at the predetermined position, the first land <NUM> is approximately aligned with the feeding and discharge ports <NUM> and <NUM>.

In order to allow the mechanical brake <NUM> to apply a braking force again, the operating unit <NUM> is operated to suspend the flow of the hydraulic oil into the feeding port <NUM>. This does not immediately result in application of the braking force by the mechanical brake <NUM>. Specifically, if the flow of the hydraulic oil into the feeding port <NUM> is suspended, the hydraulic oil no longer flows into the hydraulic oil inlet chamber <NUM> of the spool <NUM>. The hydraulic oil left in the hydraulic oil inlet chamber <NUM> is thus gradually discharged into the drain chamber <NUM> through the discharge channels <NUM>, discharge recess <NUM>, and flow channel <NUM>.

The first connection recess <NUM> is then connected to the feeding and discharge ports <NUM> and <NUM>. This causes the hydraulic oil in the mechanical brake <NUM> to flow back into the hydraulic oil inlet chamber <NUM>. The hydraulic oil in the mechanical brake <NUM> is also gradually discharged into the drain chamber <NUM> through the hydraulic oil inlet chamber <NUM>, discharge channels <NUM>, discharge recess <NUM> and flow channel <NUM>. As a result, the hydraulic oil pressure no longer acts on the mechanical brake <NUM>, allowing the mechanical brake <NUM> to regenerate a braking force. In the above-described manner, the timer valve <NUM> may control the mechanical brake <NUM> such that the mechanical brake <NUM> may generate a braking force at a point of time later than when the operator operates the operating unit <NUM>.

In the above-described embodiment, the flow channel <NUM>, which serves as the filter <NUM>, constitutes part of the liaison channel <NUM> formed in the timer valve <NUM>. Therefore, no independent filters are needed to filter out foreign objects from the hydraulic oil fed back to the tank <NUM>. The timer valve <NUM> can be made up by a reduced number of parts, so that its production can be managed in a simplified manner.

The flow channel <NUM> is defined as the minute gap G so that foreign matter included in the hydraulic oil flowing through the flow channel <NUM> is caught between the outer surface 3a of the spool <NUM> and the inner surface 5a of the spool hole <NUM>. In this way, the space between the outer surface 3a of the spool <NUM> and the inner surface 5a of the spool hole <NUM> (flow channel <NUM>) can certainly serve as the filter <NUM>. The flow channel <NUM> is defined by the reduced diameter portion <NUM> of the spool <NUM>, which is formed between the discharge recess <NUM> and the end 3c of the spool <NUM> facing the first direction and has a slightly smaller outer diameter than the other portion of the spool <NUM>. The minute gap G serving as the filter <NUM> can be obtained in such a simple manner.

According to the above embodiment, the radial width of the minute gap G between the outer surface 24a of the reduced diameter portion <NUM> and the inner surface 5a of the spool hole <NUM> is approximately equal to a filter pore size of <NUM>, for example. The present embodiment, however, is not limited to such, and the width of the minute gap G can be sized in any manner as long as the minute gap G can prevent foreign matter of a desired size.

<FIG> schematically shows the configuration of the timer valve <NUM> relating to a first modification example. <FIG> corresponds to <FIG> referred to in the above (this applies to the following modification examples). In the above-described embodiment, the flow channel <NUM> is defined by the reduced diameter portion <NUM> of the spool <NUM>. The reduced diameter portion <NUM> originates at the discharge recess <NUM> and terminates at the end 3c of the spool <NUM> facing the first direction and has a slightly smaller outer diameter than the other portion of the spool <NUM>.

The present embodiment, however, is not limited to such. As shown in <FIG>, the spool hole <NUM> may have an increased diameter portion <NUM> in a half of the spool hole <NUM> facing the first direction. The increased diameter portion <NUM> has a slightly larger inner diameter than the other portion. The flow channel <NUM> may be formed between the inner surface 27a of the increased diameter portion <NUM> and the outer surface 3a of the spool <NUM>. The increased diameter portion <NUM> is positioned or sized depending on the range within which the spool <NUM> can move. According to this modification example, the minute gap G serving as the filter <NUM> can be obtained in a simple manner.

<FIG> schematically shows the configuration of the timer valve <NUM> relating to a second modification example. As shown in <FIG>, the reduced diameter portion <NUM> of the spool <NUM> may be inclined such that its outer diameter gradually increases toward the first direction. Thus, the radial width of the minute gap G forming the flow channel <NUM> becomes progressively smaller toward the first direction (drain port <NUM>).

In this manner, foreign objects of different sizes are trapped at different sites in the filter <NUM> (flow channel <NUM>). In this way, foreign objects of various sizes can avoid being trapped at the same site in the flow channel <NUM>. This can prevent the flow channel <NUM> from being clogged by the foreign objects.

In the second modification example, the reduced diameter portion <NUM> of the spool <NUM> is inclined. The present embodiment, however, is not limited to such. Alternatively, a portion of the inner surface 5a of the spool hole <NUM> that corresponds to the flow channel <NUM> may be inclined, so that the radial width of the minute gap G forming the flow channel <NUM> may be progressively decreased toward the first direction (drain port <NUM>). Alternatively, the reduced diameter portion <NUM> and the inner surface 5a of the spool hole <NUM> may be both inclined.

The inclination mentioned in the second modification example is not necessarily provided by a flat inclined surface. The inclination can be achieved in any manner as long as the radial width of the minute gap G forming the flow channel <NUM> gradually decreases toward the first direction (drain port <NUM>). For example, the reduced diameter portion <NUM> of the spool <NUM> and/or the inner surface 5a of the spool hole <NUM> may be curved.

<FIG> schematically shows the configuration of the timer valve <NUM> relating to a third modification example. According to the above-described embodiment, the spool <NUM> has the discharge recess <NUM> and discharge channels <NUM>, and the flow channel <NUM> (filter <NUM> and orifice <NUM>) extends on the outer surface 3a of the spool <NUM> between the discharge recess <NUM> and the end 3c of the spool <NUM> facing the first direction (see <FIG> and <FIG>). The present embodiment, however, is not limited to such. As shown in <FIG>, the spool <NUM> may not necessarily have the discharge recess <NUM> and discharge channels <NUM>.

In the third modification example, the first connection recess <NUM> extends farther toward the first direction than in the embodiment. The flow channel <NUM> (filter <NUM>, orifice <NUM>) thus extends between the first connection recess <NUM> and the end 3c of the spool <NUM> facing the first direction. This modification example can produce the same effects as the above-described embodiment. In addition, the length of the hydraulic oil inlet chamber <NUM> can be reduced, and the discharge recess <NUM> and discharge channels <NUM> are no longer necessary. Therefore, the manufacturing cost of the timer valve <NUM> can be reduced.

<FIG> schematically shows the configuration of the timer valve <NUM> relating to a fourth modification example. As shown in <FIG>, the liaison channel <NUM> may include a discharge chamber <NUM> formed at the end 3c of the spool <NUM> facing the first direction and an inlet recess <NUM> (inlet channel <NUM>) in communication with the discharge chamber <NUM>. The discharge chamber <NUM> and hydraulic oil inlet chamber <NUM> are coaxially arranged. The discharge chamber <NUM> is not in communication with the hydraulic oil inlet chamber <NUM>.

The inlet recess <NUM> is annularly shaped and extends along the entire outer surface 3a of the spool <NUM>. The inlet recess <NUM> is aligned, in the radial direction of the spool <NUM>, with a half of the discharge chamber <NUM> that faces the hydraulic oil inlet chamber <NUM>. The spool <NUM> has four inlet channels <NUM> connecting the inlet recess <NUM> and the discharge chamber <NUM>. The four inlet channels <NUM> are formed such that their axial direction is orthogonal to the axial direction of the spool <NUM>. The four inlet channels <NUM> are arranged at equal intervals in the circumferential direction of the spool <NUM>. The flow channel <NUM> (filter <NUM> and orifice <NUM>) extends between the inlet recess <NUM> and the discharge recess <NUM>.

According to this modification example, the hydraulic oil flowing into the flow channel <NUM> is discharged into the discharge chamber <NUM> through the inlet recess <NUM> and inlet channels <NUM> (see the arrow Y4 in <FIG>). The hydraulic oil further flows through the discharge chamber <NUM> and goes back to the tank <NUM> through the drain chamber <NUM> and drain port <NUM>.

The fourth modification example described above thus produces the same effects as the foregoing embodiment. In addition, since the discharge chamber <NUM> and inlet recess <NUM> (inlet channels <NUM>) are provided, the flow channel <NUM> can be shifted (offset) toward the second direction from the end 3c of the spool <NUM> facing the first direction. In other words, it is no longer necessary to define the flow channel <NUM> at the end 3c of the spool <NUM> facing the first direction. When the spool <NUM> is inserted into the spool hole <NUM>, the periphery of the end 3c of the spool <NUM> may collide with the housing <NUM> and get damaged. This modification example can avoid such a collision. The damaged periphery may impair the role of the minute gap G as the filter <NUM>. According to the fourth modification example, the flow channel <NUM> (minute gap G) can reliably and satisfactorily serve as the filter <NUM> and orifice <NUM>.

<FIG> schematically shows the configuration of the timer valve <NUM> relating to a fifth modification example. As shown in <FIG>, an orifice <NUM> may be additionally provided in the discharge chamber <NUM> relating to the fourth modification example described above. According to the present modification example, the orifice <NUM> is separately provided, and the flow channel <NUM> is thus required to serve only as the filter <NUM>. According to the above-described embodiment, the flow channel <NUM> is required to serve both as the filter <NUM> and the orifice <NUM>. It may be difficult to successfully satisfy both of the required functions. The fifth modification example, however, can allow the flow channel <NUM> to serve as the filter <NUM> more appropriately. Additionally, the flow rate of the hydraulic oil discharged from the hydraulic oil inlet camber <NUM> to the drain port <NUM> can be controlled more appropriately.

The embodiments described herein are not intended to necessarily limit the present invention to any specific embodiments. Various modifications can be made to these embodiments without departing from the scope of the present invention, which is defined by the appended claims. In the above-described embodiment, the timer valve <NUM> has the flow channel <NUM>, which serves as the filter <NUM> and orifice <NUM>. The present invention, however, is not limited to such. The flow channel <NUM> serving both as the filter <NUM> and orifice <NUM> can be formed in various other valves (control valves) than the timer valve <NUM>.

According to the above-described embodiment, the timer valve <NUM> is used in hydraulic excavators and other construction machines. However, the present invention is not limited to such, and the above-described timer valve <NUM> can be applied for various construction machines. According to the above-described embodiment, the timer valve <NUM> using hydraulic oil is described as an example of a fluid valve. The present invention, however, is not limited to such, and the above-described configuration can be employed in various other fluid valves using a fluid. The fluid is not limited to hydraulic oil, but can be a variety of liquids and gases.

In the above-described embodiment, the reduced diameter portion <NUM> is formed directly in the spool <NUM>, or the increased diameter portion <NUM> is formed directly in the spool hole <NUM>. The present invention, however, is not limited to such, and the reduced diameter portion <NUM> of the spool <NUM> and the increased diameter portion <NUM> of the spool hole <NUM> may be sized larger than the designed values to receive tubular bushings. The outer and inner surfaces of the bushings may be accurately processed, so that the radial width of the minute gap G formed by the flow channel <NUM> can be easily and highly accurately controlled.

The above-described embodiment uses the coil spring <NUM> as the elastic member for forcing the spool <NUM> toward the second direction. The present invention, however, is not limited to such, and the elastic member may be configured in any manner as long as it can force the spool <NUM> toward the second direction. The coil spring <NUM> may be replaced with other elastic members such as rubber members. The rubber members may be only required not to close the drain chamber <NUM>.

Claim 1:
A fluid valve (<NUM>) comprising:
a housing (<NUM>) having a spool hole (<NUM>), a feeding port (<NUM>) and a discharge port (<NUM>), the spool hole (<NUM>) being in communication with a drain port (<NUM>), the feeding port (<NUM>) being configured to receive a hydraulic fluid fed thereto, and the discharge port (<NUM>) being configured to discharge the hydraulic fluid; and
a spool (<NUM>) movably provided in the spool hole (<NUM>),
wherein the spool (<NUM>) has:
a connection recess (<NUM>) defined in an outer surface of the spool (<NUM>), the connection recess (<NUM>) being configured to establish communication between the feeding port (<NUM>) and the discharge port (<NUM>); and
a liaison channel (<NUM>) establishing communication between the connection recess (<NUM>) and the drain port (<NUM>), and
wherein, within the liaison channel (<NUM>), a flow channel (<NUM>) is formed between the spool hole (<NUM>) and the outer surface (3a) of the spool (<NUM>), the flow channel (<NUM>) serves as a filter (<NUM>) to stop foreign matter from entering into the drain port (<NUM>),
wherein a radial width of the flow channel (<NUM>) is sized to inhibit passage of foreign matter of a desired size,
wherein the flow channel (<NUM>) constitutes a given part of a gap formed between the spool hole (<NUM>) and the outer surface (3a) of the spool (<NUM>), and characterized in that
the flow channel (<NUM>) has a greater radial width than a remaining part of the gap formed between the spool hole (<NUM>) and the outer surface (3a) of the spool (<NUM>) since a reduced diameter portion (<NUM>) is formed directly in the spool (<NUM>) and the flow channel (<NUM>) is formed between an outer surface (24a) of the reduced diameter portion (<NUM>) and an inner surface (5a) of the spool hole (<NUM>), or since an increased diameter portion (<NUM>) is formed directly in the spool hole (<NUM>) and the flow channel (<NUM>) is formed between an inner surface (27a) of the increased diameter portion (<NUM>) and the outer surface (3a) of the spool (<NUM>).