Patent Description:
Solenoids are used, for example, in solenoid valves. Some solenoid valves are used to vary the damping force of a damper interposed between a vehicle body and a wheel of a vehicle.

Such a damper includes, for example, as disclosed in <CIT>, a main valve body that applies a resistance to a flow of a liquid, the flow occurring during extension and contraction of the damper, a pressure introduction passage that has an orifice partway to reduce a pressure upstream of the main valve body and guide the reduced pressure to a back surface of the main valve body, and a pressure control passage that is connected downstream of the orifice in the pressure introduction passage.

Further, in the damper described above, a solenoid valve is provided partway in the pressure control passage. The solenoid valve includes a valve body that is seated on and separated from a valve seat provided partway in the pressure control passage, a biasing spring that biases the valve body in a direction away from the valve seat, and a solenoid that applies a thrust to the valve body in a direction opposite to that of the biasing force of the biasing spring.

Specifically, the solenoid described above includes a coil, a first fixed iron core and a second fixed iron core that are arranged with a predetermined distance therebetween and are magnetized when the coil is energized, an annular movable iron core that is disposed movably between the first fixed iron core and the second fixed iron core, and a shaft that is fixed to the inner circumference of the movable iron core and abuts against the valve body at its distal end. The solenoid described above is configured such that when the coil is excited, a magnetic path is formed so as to pass through the first fixed iron core, the movable iron core, and the second fixed iron core, and the movable iron core is attracted toward the second fixed iron core to cause the shaft to push the valve body toward the valve seat.

The thrust of the solenoid that biases the valve body so as to be closed is proportional to the amount of current supplied to the solenoid, and thus increases as the amount of supply current increases. As a result, the valve opening pressure of the valve body increases. The back pressure of the main valve body is controlled by the valve opening pressure of the valve body, and the resistance of the main valve body increases as the back pressure increases.

For this reason, when the amount of current supplied to the solenoid is increased to increase the valve opening pressure of the valve body, the resistance of the main valve body increases and the damping force generated by the damper increases accordingly, so that hard damping force characteristics can be achieved. Conversely, when the amount of current supplied to the solenoid is reduced to reduce the valve opening pressure of the valve body, the resistance of the main valve body decreases and the damping force generated by the damper decreases accordingly, so that soft damping force characteristics can be achieved.

Furthermore, the document <CIT>, which is considered the closest prior art, discloses a closed electromagnetic valve with a rod that is supported so as to be able to move in a first direction toward a valve seat as well as in a second direction away from the valve seat. This rod closes off the hydraulic fluid path when seated on the valve seat, and opens up the hydraulic fluid path when away from the valve seat. When current is not being supplied to a coil, a first armature pushes the rod in the first direction using urging force of a first spring. When current is being supplied to the coil, the first armature moves in the second direction, and the second armature pushes the rod in the first direction using electromagnetic force corresponding to the amount of the current.

When the damper described above is used in a vehicle and the riding comfort is desired to be improved when the vehicle normally travels on a good road, it is preferable to achieve soft damping force characteristics. When a solenoid valve including a conventional solenoid is used for the damper, soft damping force characteristics can be achieved when the amount of current supplied to the solenoid is reduced, and thus power consumption can be reduced during normal traveling to save power.

Further, when the portion that controls a valve opening pressure is a pressure control valve portion in a valve body of the solenoid valve described above, the valve body includes an opening/closing valve portion that opens and closes the downstream side of the pressure control valve portion. When the solenoid is de-energized and the pressure control valve portion is opened to the maximum, the opening/closing valve portion closes a pressure control passage. A fail passage is connected between an opening/closing portion of the pressure control valve portion and an opening/closing portion of the opening/closing valve portion in the pressure control passage, and a passive valve is provided in the fail passage.

For this reason, at the time of a failure in which the solenoid is de-energized, the opening/closing valve portion closes the pressure control passage and a liquid passes through the passive valve. Consequently, at the time of a failure, the back pressure of a main valve body is determined by the valve opening pressure of the passive valve. That is, even if the power supply to the solenoid valve is cut off, the main valve body applies a predetermined resistance to a flow of the liquid generated when the damper is extended and contracted, and the damper can thus apply a predetermined damping force, which is fail-safe.

However, since it is necessary to provide a passage for a failure in addition to a passage for pressure control in the configuration described above, the structure of the damper becomes complicated and the cost increases. On the other hand, if the valve body of the solenoid valve is biased by a biasing spring so as to be closed and the solenoid applies a thrust to the valve body so as to open the valve body, it is possible to use a common passage for pressure control and a failure. However, power consumption during normal traveling may increase. This is because it is necessary to increase the amount of current supplied to the solenoid in order to achieve soft damping force characteristics during normal traveling in the configuration described above.

That is, in a solenoid valve or the like used for pressure control, there are some cases where when the amount of current supplied to a solenoid is small, the thrust applied to an object such as a valve body is desired to be reduced, and at the same time, even when the solenoid is not energized, the object is desired to be biased in the same direction as that of the thrust.

The present invention has been made in order to solve such a problem, and an object of the invention is to provide a solenoid, a solenoid valve, and a damper in which when the amount of current supplied to the solenoid is small, the thrust of the solenoid to bias an object in one direction can be made small, and at the same time, even when the solenoid is not energized, the object can be biased in the same direction as that of the thrust.

According to a first aspect, the invention provides a solenoid in accordance with independent claim <NUM>. According to a second aspect, the invention provides a solenoid valve in accordance with independent claim <NUM>. According to a third aspect, the invention provides a damper in accordance with independent claim <NUM>. Further aspects of the invention are set forth in the dependent claims, the drawings, and the following description.

A solenoid that solves the above problem includes a first movable iron core and a second movable iron core that are attracted in a direction away from each other by energizing a coil, a biasing member that biases the first movable iron core toward the second movable iron core, and a first regulation member that restricts approach of the first movable iron core and the second movable iron core.

Like reference symbols in the several drawings indicate like parts.

As illustrated in <FIG>, a solenoid S according to an embodiment of the present invention is used for a solenoid valve <NUM>, and the solenoid valve <NUM> is a member that constitutes a damping valve V of a damper D. The damper D is used for vehicle suspensions in the present embodiment.

As illustrated in <FIG>, the damper D includes a cylinder <NUM>, a piston <NUM> slidably inserted into the cylinder <NUM>, and a piston rod <NUM> having one end connected to the piston <NUM> and the other end projecting outside the cylinder <NUM>.

The cylinder <NUM> is connected to one of a vehicle body and an axle of a vehicle, and the piston rod <NUM> is connected to the other one. In this way, the damper D is interposed between the vehicle body and the axle. Further, when the vehicle travels on an irregular road surface and thus vibrates vertically, the piston rod <NUM> moves into and out of the cylinder <NUM> to extend and contract the damper D, so that the piston <NUM> moves within the cylinder <NUM> vertically (in axial direction) in <FIG>.

A head member <NUM> that has an annular shape and allows insertion of the piston rod <NUM> is attached to one axial end of the cylinder <NUM>. The head member <NUM> slidably supports the piston rod <NUM> and closes one end of the cylinder <NUM>. On the other hand, the other end of the cylinder <NUM> is closed by a bottom cap <NUM>. The cylinder <NUM> is hermetically sealed as described above, and a liquid and a gas are filled in the cylinder <NUM>.

More specifically, a free piston <NUM> is slidably inserted into the cylinder <NUM> so as to be opposite to the piston rod <NUM> with respect to the piston <NUM>. Then, a liquid chamber L filled with a liquid such as a hydraulic oil is formed on a side of the free piston <NUM> facing the piston <NUM>. On the other hand, a gas chamber G filled with a compressed gas is formed on a side of the free piston <NUM> opposite to the piston <NUM>.

The liquid chamber L and the gas chamber G in the cylinder <NUM> are thus partitioned by the free piston <NUM> in the damper D. Further, the liquid chamber L is partitioned by the piston <NUM> into an extension-side chamber L1 closer to the piston rod <NUM> and a compression-side chamber L2 on the opposite side (opposite side to piston rod). The damping valve V is attached to the piston <NUM>. The damping valve V applies a resistance to a flow of a liquid passing between the extension-side chamber L1 and the compression-side chamber L2.

According to the above configuration, when the damper D is extended, the piston <NUM> moves upward in <FIG> in the cylinder <NUM> to compress the extension-side chamber L1, and then a liquid in the extension-side chamber L1 moves through the damping valve V to the compression-side chamber L2, and the damping valve V applies a resistance to the flow of the liquid. The pressure of the extension-side chamber L1 thus increases when the damper D is extended, and the damper D applies an extension-side damping force that hinders the extension operation of the damper D.

Conversely, when the damper D is contracted, the piston <NUM> moves downward in <FIG> in the cylinder <NUM> to compress the compression-side chamber L2, and then a liquid in the compression-side chamber L2 moves through the damping valve V to the extension-side chamber L1, and the damping valve V applies a resistance to the flow of the liquid. The pressure of the compression-side chamber L2 thus increases when the damper D is contracted, and the damper D applies a compression-side damping force that hinders the contraction operation of the damper D.

Further, when the damper D is extended and contracted, the free piston <NUM> is moved to extend and reduce the gas chamber G, thus compensating for the volume of the piston rod <NUM> moving into and out of the cylinder <NUM>.

However, the configuration of the damper D is not limited to that illustrated in the drawing, and can be changed as appropriate. For example, instead of the gas chamber G, a reservoir that stores a liquid and a gas may be provided, and the liquid may be passed between the cylinder and the reservoir when the damper is extended and contracted. Further, the damper D may be a double rod type, and piston rods may be provided on both sides of the piston. In this case, a configuration that compensates for the volume of the piston rod can be omitted.

Next, as illustrated in <FIG>, the damping valve V includes a main passage P1 that causes the extension-side chamber L1 to communicate with the compression-side chamber L2, an annular valve seat member <NUM> through which the main passage P1 passes on its inner circumferential side, a main valve body <NUM> that is seated on and separated from the valve seat member <NUM> to open and close the main passage P1, an extension-side pressure introduction passage P2 that includes an orifice O1 partway to reduce the pressure on a side of the main valve body <NUM> facing the extension-side chamber L1 and guide the reduced pressure to a back surface of the main valve body <NUM>, a compression-side pressure introduction passage P3 that includes an orifice O2 partway to reduce the pressure on a side of the main valve body <NUM> facing the compression-side chamber L2 and guide the reduced pressure to the back surface of the main valve body <NUM>, a pressure control passage P4 that is connected downstream of the orifice O1 in the extension-side pressure introduction passage P2 and includes the solenoid valve <NUM> partway, and an extension-side valve <NUM> and a compression-side valve <NUM> that are provided closer to the compression-side chamber L2 than the main valve body <NUM> in the main passage P1.

Further, the piston <NUM> and the piston rod <NUM> constitute a housing H of the damping valve V together with a cylindrical guide <NUM> connecting these piston <NUM> and the piston rod <NUM>. The piston <NUM> has a cylindrical shape with a bottom, and a cylindrical portion 10a faces the piston rod <NUM>. In addition, a cylindrical case portion 11a with a top is provided at a distal end of the piston rod <NUM>, and the case portion 11a has a cylindrical portion 11b facing the piston <NUM>. The piston <NUM> and the case portion 11a are disposed so that the cylindrical portions 10a and 11b face each other.

The one axial end of the guide <NUM> is screwed into an inner circumference of the distal end of the cylindrical portion 11b in the case portion 11a, and the other axial end of the guide <NUM> is screwed into an inner circumference of the distal end of the cylindrical portion 10a in the piston <NUM>. In this way, the case portion 11a, the guide <NUM>, and the piston <NUM> are integrated to function as the housing H of the damping valve V, and the valve seat member <NUM>, the main valve body <NUM>, the solenoid valve <NUM>, and the compression-side valve <NUM> is housed in the housing H. Further, the extension-side valve <NUM> is attached to the outside of the housing H.

Hereinafter, members that are housed in or attached to the housing H of the damping valve V will be described in detail. In the following description, for convenience of description, upper and lower directions in <FIG> and <FIG> are simply referred to as "upper" and "lower", unless otherwise specified.

A projection 10b is formed on the inner circumference of the cylindrical portion 10a of the piston <NUM>. The outer circumferential portion of the valve seat member <NUM> is sandwiched between the projection 10b and the guide <NUM>, and thus the valve seat member <NUM> is fixed therebetween. As described above, the valve seat member <NUM> is annular, and a first valve seat 2a having an annular shape is formed on an inner circumferential portion of an upper end of the valve seat member <NUM>. The main valve body <NUM> is seated on and separated from the first valve seat 2a. The main valve body <NUM> is divided into upper and lower parts, and thus is constituted by a first valve body member <NUM> on a lower side (closer to valve seat member <NUM>) and a second valve body member <NUM> stacked on the first valve body member <NUM>.

The first valve body member <NUM> has an annular shape, and includes, at its upper end, a second valve seat 30a having an annular shape. The second valve body member <NUM> is seated on and separated from the second valve seat 30a. Moreover, tapered surfaces 30b and 30c are formed on the outer circumference and the inner circumference of the first valve body member <NUM>, respectively. Each of the tapered surfaces 30b and 30c has a truncated cone shape whose diameter gradually decreases toward the lower end. A portion of the first valve body member <NUM> having the tapered surface 30b formed on its outer circumference is inserted into the inside of the valve seat member <NUM>, so that the tapered surface 30b is seated on and separated from the first valve seat 2a.

On the other hand, the second valve body member <NUM> includes a head portion 31a, a body portion 31b that is connected to the lower side of the head portion 31a and has an outer diameter larger than the outer diameter of the head portion 31a, and an annular leg portion 31c that is connected to the lower side of the body portion 31b and has an outer diameter smaller than the outer diameter of the body portion 31b. The second valve body member <NUM> is slidably inserted into the inside of the guide <NUM>, so that the leg portion 31c is seated on and separated from the second valve seat 30a of the first valve body member <NUM>.

More specifically, the inner diameter of an upper end of the guide <NUM> is smaller than the inner diameter of a lower portion thereof. In the guide <NUM>, a portion having a small inner diameter at the upper end is referred to as "small inner diameter portion 7a", and a portion having a large inner diameter on the lower side is referred to as "large inner diameter portion 7b". The head portion 31a of the second valve body member <NUM> slide-contacts an inner circumference of the small inner diameter portion 7a, and the body portion 31b of the second valve body member <NUM> slide-contacts an inner circumference of the large inner diameter portion 7b.

As illustrated in <FIG>, on the outer circumference of the leg portion 31c of the second valve body member <NUM> and the first valve body member <NUM>, an annular gap K is formed under the body portion 31b extending radially outward from the leg portion 31c. The annular gap K communicates with the extension-side chamber L1 through a communication hole 7c formed in the guide <NUM>, and the pressure in the annular gap K is thus substantially equal to the pressure in the extension-side chamber L1. The pressure of the extension-side chamber L1 acts on the tapered surface 30b on the outer circumferential side of the main valve body <NUM>, a lower surface of the body portion 31b extending from the leg portion 31c, and the like, and thus the first valve body member <NUM> and the second valve body member <NUM> are biased upward by the pressure of the extension-side chamber L1.

More specifically, the outer diameter of a contact portion of the tapered surface 30b of the first valve body member <NUM> and the first valve seat 2a is referred to as "diameter a", and the outer diameter of a slide contact portion of the body portion 31b of the second valve body member <NUM> and the large inner diameter portion 7b is referred to as "diameter b". The diameter b is larger than the diameter a (b > a), and the pressure receiving area of the main valve body <NUM> that receives the pressure of the extension-side chamber L1 is the area obtained by removing the area of a circle with the diameter a from the area of a circle with the diameter b. The main valve body <NUM> is then biased in a direction (opening direction) to separate the first valve body member <NUM> from the first valve seat 2a by a force obtained by multiplying the pressure of the extension-side chamber L1 by the pressure receiving area.

Consequently, when the pressure of the extension-side chamber L1 increases at the time of the extension of the damper D, the first valve body member <NUM> and the second valve body member <NUM> are pushed up by the pressure, and the first valve body member <NUM> is opened, a liquid in the extension-side chamber L1 passes between the first valve body member <NUM> and the first valve seat 2a toward a bottom portion 10c (<FIG>) of the piston <NUM>. The first valve body member <NUM> then applies a resistance to the flow of the liquid.

As illustrated in <FIG>, the bottom portion 10c of the piston <NUM> includes an extension-side passage 10d and a compression-side passage 10e that vertically penetrate the bottom portion 10c. That is, when the area between the body portion 31b of the second valve body member <NUM> and the bottom portion 10c of the piston <NUM>, the area being surrounded by the leg portion 31c, the first valve body member <NUM>, the valve seat member <NUM>, and the cylindrical portion 10a of the piston <NUM>, is referred to as "central chamber L3", the extension-side passage 10d and the compression-side passage 10e allow the central chamber L3 to communicate with the compression-side chamber L2.

An inlet of the extension-side passage 10d always communicates with the central chamber L3, whereas an outlet of the extension-side passage 10d is opened and closed by the extension-side valve <NUM> stacked under the bottom portion 10c. This extension-side valve <NUM> is opened when the damper D is extended to apply a resistance to a flow of a liquid from the central chamber L3 to the compression-side chamber L2 in the extension-side passage 10d, and is closed when the damper D is contracted to block a flow in the opposite direction.

On the other hand, an inlet of the compression-side passage 10e always communicates with the compression-side chamber L2, whereas an outlet of the compression-side passage 10e is opened and closed by the compression-side valve <NUM> stacked on the bottom portion 10c. This compression-side valve <NUM> is opened when the damper D is contracted to apply a resistance to a flow of a liquid from the compression-side chamber L2 to the central chamber L3 in the compression-side passage 10e, and is closed when the damper D is extended to block a flow in the opposite direction. The liquid having flown from the compression-side chamber L2 into the central chamber L3 when the damper D is contracted then flows toward the main valve body <NUM>.

The pressure of the central chamber L3 acts on a lower surface of the leg portion 31c of the second valve body member <NUM> and the like, and the second valve body member <NUM> is biased upward by the pressure of the central chamber L3. Further, the pressure of the central chamber L3 also acts on the tapered surface 30c on the inner circumferential side of the first valve body member <NUM> and the like, and the first valve body member <NUM> is biased downward by the pressure of the central chamber L3. As described above, the first valve body member <NUM> and the second valve body member <NUM> are biased in opposite directions by the pressure of the central chamber L3.

More specifically, as illustrated in <FIG>, an upper side of the head portion 31a of the second valve body member <NUM> and the central chamber L3 are communicated with each other by a vertical hole 31f to described later, and the pressures thereof are equal. The outer diameter of a slide contact portion of the head portion 31a of the second valve body member <NUM> and the small inner diameter portion 7a is referred to as "diameter c", and the inner diameter of a contact portion of the leg portion 31c of the second valve body member <NUM> and the second valve seat 30a is referred to as "diameter d". The diameter d is larger than the diameter c (d > c), and the pressure receiving area of the second valve body member <NUM> that receives the pressure of the central chamber L3 is the area obtained by removing the area of a circle with the diameter c from the area of a circle with the diameter d. The second valve body member <NUM> is then biased in a direction (opening direction) to separate from the second valve seat 30a by a force obtained by multiplying the pressure of the central chamber L3 by the pressure receiving area.

When the inner diameter of a contact portion of the tapered surface 30b on the outer circumferential side of the first valve body member <NUM> and the first valve seat 2a is referred to as "diameter e", the diameter d is larger than the diameter e (d > e), and the pressure receiving area of the first valve body member <NUM> that receives the pressure of the central chamber L3 is the area obtained by removing the area of a circle with the diameter e from the area of the circle with the diameter d. The first valve body member <NUM> is then biased in a direction (closing direction) to be seated on the first valve seat 2a by a force obtained by multiplying the pressure of the central chamber L3 by the pressure receiving area.

Consequently, when the compression-side valve <NUM> (<FIG>) is opened at the time of the contraction of the damper D, a liquid flows from the compression-side chamber L2 into the central chamber L3 and the pressure in the central chamber L3 increases accordingly, and the second valve body member <NUM> is pushed up by this pressure to be separated from the first valve body member <NUM>, the liquid in the central chamber L3 then passes between the second valve body member <NUM> and the second valve seat 30a toward the extension-side chamber L1. The second valve body member <NUM> then applies a resistance to the flow of the liquid.

As can be seen from the above, the communication hole 7c, the annular gap K, the central chamber L3, and the extension-side passage 10d and the compression-side passage 10e are a part of the main passage P1 that causes the extension-side chamber L1 to communicate with the compression-side chamber L2. The main passage P1 is opened and closed by the main valve body <NUM>. Furthermore, a portion of the main passage P1 closer to the compression-side chamber L2 than an opening/closing portion of the main valve body <NUM> branches into the extension-side passage 10d and the compression-side passage 10e, and the extension-side valve <NUM> and the compression-side valve <NUM> are disposed in the extension-side passage 10d and the compression-side passage 10e, respectively (<FIG>). In other words, the extension-side valve <NUM> and the compression-side valve <NUM> are connected in parallel to the side of the main valve body <NUM> facing the compression-side chamber L2.

When the damper D is extended, the first valve body member <NUM> and the extension-side valve <NUM> apply a resistance to the flow of the liquid from the extension-side chamber L1 to the compression-side chamber L2 in the main passage P1, and the damper D applies an extension-side damping force due to the resistance. Conversely, when the damper D is contracted, the second valve body member <NUM> and the compression-side valve <NUM> apply a resistance to the flow of the liquid from the compression-side chamber L2 to the extension-side chamber L1 in the main passage P1, and the damper D applies a compression-side damping force due to the resistance.

Further, in the present embodiment, a cut-away portion 31d (<FIG>) is formed at a lower end of the leg portion 31c of the second valve body member <NUM>. An orifice is formed by the cut-away portion 31d. Consequently, even when the main valve body <NUM> is closed, that is, even when both the first valve body member <NUM> and the second valve body member <NUM> are closed, the extension-side chamber L1 communicates with the central chamber L3 through the orifice.

An annular back pressure chamber L4 is formed between the head portion 31a of the second valve body member <NUM> and the large inner diameter portion 7b of the guide <NUM> on the body portion 31b extending radially outward from the head portion 31a. The pressure of the back pressure chamber L4 acts on the upper surface of the body portion 31b that is the back surface of the main valve body <NUM>, and the first valve body member <NUM> and the second valve body member <NUM> are biased downward by the pressure of the back pressure chamber L4.

More specifically, as illustrated in <FIG>, the pressure receiving area of the main valve body <NUM> that receives the pressure of the back pressure chamber L4 is the area obtained by removing the area of the circle with the diameter c from the area of the circle with the diameter b. The main valve body <NUM> is then biased in a direction (closing direction) to respectively seat the first valve body member <NUM> and the second valve body member <NUM> on the first valve seat 2a and the second valve seat 30a by a force obtained by multiplying the pressure of the back pressure chamber L4 by the pressure receiving area.

Further, the second valve body member <NUM> includes a mounting hole 31e in a central portion from the head portion 31a to the body portion 31b. The second valve body member <NUM> also includes the vertical hole 31f that is located on an outer circumferential side of the mounting hole 31e and causes the upper side of the head portion 31a to communicate with an inner circumferential side of the leg portion 31c, a horizontal hole <NUM> whose one end is open to the back pressure chamber L4 and whose other end is open to the mounting hole 31e, a first inclined hole <NUM> that causes the mounting hole 31e to communicate with the annular gap K, and a second inclined hole 31i that causes the back pressure chamber L4 to communicate with the central chamber L3.

A cylindrical valve case <NUM> is attached to the mounting hole 31e, and the valve case <NUM> is disposed with its axial end facing upward. An annular groove 8a is formed on an outer circumference of the valve case <NUM> along a circumferential direction, and with the annular groove 8a, an annular gap with the top and bottom closed is formed on the outer circumference of the valve case <NUM>. The horizontal hole <NUM> and the first inclined hole <NUM> are open to this gap.

The back pressure chamber L4 thus communicates with the extension-side chamber L1 through the horizontal hole <NUM>, the gap formed on the outer circumference of the valve case <NUM> by the annular groove 8a, the first inclined hole <NUM>, the annular gap K, and the communication hole 7c. Since the orifice O1 is disposed partway in the first inclined hole <NUM>, the pressure of the extension-side chamber L1 is reduced and the reduced pressure is guided to the back pressure chamber L4.

In the second valve body member <NUM>, a check valve <NUM> that opens and closes the outlet of the second inclined hole 31i is attached to the upper side of the body portion 31b that extends radially outward from the head portion 31a. This check valve <NUM> is opened when the damper D is contracted to allow a flow of a liquid from the central chamber L3 to the back pressure chamber L4 in the second inclined hole 31i, and is closed when the damper D is extended to block a flow in the opposite direction. Since the orifice O2 is disposed partway in the second inclined hole 31i, the pressure of the central chamber L3 is reduced and the reduced pressure is guided to the back pressure chamber L4.

The valve case <NUM> includes, in its upper part, a tapered portion 8b whose inner diameter gradually increases toward the upper end and an annular valve seat portion 8c that projects upward from an upper end of the tapered portion 8b. The tapered portion 8b includes a communication hole 8d that causes the annular gap formed on the outer circumference of the valve case <NUM> by the annular groove 8a to communicate with an inner circumferential side of the tapered portion 8b. Further, a valve body <NUM> of the solenoid valve <NUM> is seated on and separated from the valve seat portion 8c of the valve case <NUM>.

The valve body <NUM> includes a sliding portion 9a that is slidably inserted into the inside of the valve case <NUM>, a small-diameter portion 9b that projects above the valve case <NUM> from the sliding portion 9a and has an outer diameter smaller than the outer diameter of the sliding portion 9a, an opening/closing portion 9c that projects horizontally from the upper end of the small-diameter portion 9b extending to the outside of the valve case <NUM> to be seated on and separated from the valve seat portion 8c, and a shaft portion 9d that projects upward from the opening/closing portion 9c.

The solenoid valve <NUM> includes the solenoid S that applies a thrust to the valve body <NUM> in a downward direction, that is, in a direction to seat the opening/closing portion 9c on the valve seat portion 8c, when the solenoid valve <NUM> is energized. When the valve body <NUM> receives the thrust of the solenoid S to be moved downward, the opening/closing portion 9c is seated on the valve seat portion 8c. Further, an annular gap is formed between an outer circumference of the small-diameter portion 9b of the valve body <NUM> and the valve case <NUM>, and the pressure of the back pressure chamber L4 is transmitted to this gap through the communication hole 8d. The valve body <NUM> is thus biased upward by the pressure of the back pressure chamber L4.

Consequently, when the force due to the pressure of the back pressure chamber L4 that biases the valve body <NUM> upward exceeds the thrust of the solenoid S that acts in the direction to push down the valve body <NUM>, the opening/closing portion 9c of the valve body <NUM> is separated from the valve seat portion 8c. Then, when the valve body <NUM> is opened in this way, a liquid passes between the opening/closing portion 9c and the valve seat portion 8c to be flown into the upper side of the head portion 31a of the second valve body member <NUM>. The liquid then flows from the upper side of the head portion 31a to the central chamber L3 through the vertical hole 31f.

As can be seen from the above, the first inclined hole <NUM>, the gap formed on the outer circumference of the valve case <NUM> by the annular groove 8a, and the horizontal hole <NUM> constitute the extension-side pressure introduction passage P2 that includes orifice O1 to reduce the pressure on the side of the main valve body <NUM> facing the extension-side chamber L1 and guide the reduced pressure to the back surface of the main valve body <NUM>.

Further, the second inclined hole 31i constitutes the compression-side pressure introduction passage P3 that includes the orifice O2 to reduce the pressure on the side of the main valve body <NUM> facing the compression-side chamber L2 and guide the reduced pressure to the back surface of the main valve body <NUM>. The compression-side pressure introduction passage P3 is one-way because of the check valve <NUM>, and allows only a flow of a liquid from the side of the compression-side chamber L2 to the back surface of the main valve body <NUM>.

Moreover, the communication hole 8d, the gap formed on the outer circumference of the small-diameter portion 9b of the valve body <NUM>, the upper side of the head portion 31a of the second valve body member <NUM>, and the vertical hole 31f constitute the pressure control passage P4 connected downstream of the orifice O1 in the extension-side pressure introduction passage P2, and the solenoid valve <NUM> is disposed partway in the pressure control passage P4.

Then, when the damper D is extended, in which the pressure of the extension-side chamber L1 increases, a liquid flows from the extension-side chamber L1 into the back pressure chamber L4 through the extension-side pressure introduction passage P2, and thus the pressure of the back pressure chamber L4 increases. Further, when the valve body <NUM> of the solenoid valve <NUM> is opened by the pressure of the back pressure chamber L4, the liquid flows from the back pressure chamber L4 to the central chamber L3 through the pressure control passage P4 to join a flow of a liquid from the extension-side chamber L1 to the compression-side chamber L2 in the main passage P1.

Consequently, when the damper D is extended, the pressure of the back pressure chamber L4 is controlled by the valve opening pressure of the valve body <NUM> of the solenoid valve <NUM>. As the amount of current supplied to the solenoid valve <NUM> is adjusted to adjust the thrust of the solenoid S, the valve opening pressure of the valve body <NUM> is adjusted. In a normal state where the solenoid valve <NUM> is energized, the pressure of the back pressure chamber L4 at the time of the extension of the damper D can thus be controlled. As described above, in the present embodiment, the solenoid valve <NUM> functions as a pressure control valve that controls the back pressure of the main valve body <NUM> when the damper D is extended.

Conversely, when the damper D is contracted in which a liquid flows from the compression-side chamber L2 into the central chamber L3, the check valve <NUM> is opened, and the liquid flows from the central chamber L3 to the back pressure chamber L4 through the compression-side pressure introduction passage P3. The liquid then flows from the back pressure chamber L4 to the extension-side chamber L1 through the extension-side pressure introduction passage P2.

At this time, the pressure on the downstream side of the solenoid valve <NUM> in the pressure control passage P4 is equal to the pressure of the central chamber L3 and is higher than the pressure of the back pressure chamber L4 on the upstream side of the solenoid valve <NUM>, and thus the valve body <NUM> of the solenoid valve <NUM> is kept closed. As a result, in the present embodiment, when the damper D is contracted, the pressure control of the back pressure chamber L4 by the solenoid valve <NUM> does not work effectively.

As illustrated in <FIG>, the solenoid S is housed in the case portion 11a of the piston rod <NUM>. The solenoid S includes a molded stator M in which a coil <NUM> and a harness <NUM> for energizing the coil <NUM> are integrated with a molding resin, a first fixed iron core <NUM> and a second fixed iron core <NUM> that are magnetized when the coil <NUM> is energized, and a filler ring <NUM> that is interposed between the first fixed iron core <NUM> and the second fixed iron core <NUM> to form a magnetic gap between these fixed iron cores.

The molded stator M is housed in the case portion 11a. The first fixed iron core <NUM> includes a base portion 42a and an annular flange portion 42b extending radially outward from one end of the base portion 42a. The first fixed iron core <NUM> is inserted into the molded stator M with the flange portion 42b facing upward. On the other hand, the second fixed iron core <NUM> has a substantially disc shape and is stacked under the molded stator M.

The filler ring <NUM> has a cylindrical shape and has one end abutting against the flange portion 42b of the first fixed iron core <NUM> and the other end abutting against the second fixed iron core <NUM>. Consequently, at the time of assembly, the molded stator M is firstly inserted into the case portion 11a of the piston rod <NUM>, the first fixed iron core <NUM> and the filler ring <NUM> are then inserted into the inside of the molded stator M in this order, the second fixed iron core <NUM> is placed under the molded stator M, and the guide <NUM> is screwed into the case portion 11a. As a result, the second fixed iron core <NUM> is fixed to a distal end of the cylindrical portion of the molded stator M, and the first fixed iron core <NUM> is fixed to a ceiling portion inside of the case portion 11a.

In this way, the first fixed iron core <NUM> and the second fixed iron core <NUM> are arranged with a predetermined distance therebetween. The solenoid S includes a first upper (closer to first fixed iron core <NUM>) movable iron core <NUM> and a second lower (closer to second fixed iron core <NUM>) movable iron core <NUM> that are disposed between the first fixed iron core <NUM> and the second fixed iron core <NUM> so as to be movable vertically (toward first fixed iron core <NUM> and toward second fixed iron core <NUM>), and a coil spring <NUM> that biases the first movable iron core <NUM> downward (toward second movable iron core <NUM>).

Both the first movable iron core <NUM> and the second movable iron core <NUM> have a cylindrical shape with a bottom, and are disposed with their bottom portions 45a and 46a facing downward. The first movable iron core <NUM> is inserted into the inside of the second movable iron core <NUM> so as to be movable in the axial direction. The coil spring <NUM> is further inserted into the inside of the first movable iron core <NUM>, and the coil spring <NUM> is interposed between the bottom portion 45a of the first movable iron core <NUM> and the first fixed iron core <NUM> in a compressed state to bias the first movable iron core <NUM> toward the second movable iron core <NUM>.

As described above, the coil spring <NUM> is used as a biasing member that biases the first movable iron core <NUM> toward the second movable iron core <NUM> in the present embodiment. However, the configuration of the biasing member is not limited to this, and can be changed as appropriate. For example, a non-claimed fehe biasing member may be a spring other than a coil spring or may be an elastic member such as rubber, and the arrangement of the biasing member can be changed according to the configuration of the biasing member.

A communication hole (not illustrated) penetrating in the axial direction is formed in each of the bottom portion 45a of the first movable iron core <NUM> and the bottom portion 46a of the second movable iron core <NUM>. It is thus possible to prevent a pressure difference between the inside of the first movable iron core <NUM> and the second movable iron core <NUM> and the outside of the first movable iron core <NUM> and the second movable iron core <NUM> from hindering smooth movements of these iron cores. The position and number of the communication holes are not limited to those illustrated in the figure, and can be changed as appropriate.

The solenoid S also includes a leaf spring <NUM> disposed between the bottom portion 45a of the first movable iron core <NUM> and the bottom portion 46a of the second movable iron core <NUM> and a leaf spring <NUM> disposed between the bottom portion 46a of the second movable iron core <NUM> and the second fixed iron core <NUM>. Hereinafter, for convenience of description, the leaf spring <NUM> closer to the first movable iron core <NUM> is referred to as "first leaf spring <NUM>", and the leaf spring <NUM> closer to the second fixed iron core <NUM> is referred to as "second leaf spring <NUM>".

When the bottom portion 45a of the first movable iron core <NUM> and the bottom portion 46a of the second movable iron core <NUM> come close to each other to some extent, the first leaf spring <NUM> prevents the first movable iron core <NUM> and the second movable iron core <NUM> from further approaching, thus avoiding adsorption of the first movable iron core <NUM> to the second movable iron core <NUM>. Similarly, when the bottom portion 46a of the second movable iron core <NUM> and the second fixed iron core <NUM> come close to each other to some extent, the second leaf spring <NUM> prevents the second movable iron core <NUM> and the second fixed iron core <NUM> from further approaching, thus avoiding adsorption of the second movable iron core <NUM> to the second fixed iron core <NUM>.

As described above, the first and second leaf springs <NUM> and <NUM> function as regulation members that restrict the approach amount of the first movable iron core <NUM> and the second movable iron core <NUM> or of the second movable iron core <NUM> and the second fixed iron core <NUM> to prevent these contacts. However, if the regulation member can prevent the iron cores from approaching each other more than a predetermined distance, the configuration of the regulation member can be changed as appropriate.

For example, one or both of the first leaf spring <NUM> and the second leaf spring <NUM> may be replaced with a ring made of rubber, synthetic resin or the like, and the ring may be used as the regulation member. Further, the minimum gap amount between the first movable iron core <NUM> and the second movable iron core <NUM> and the minimum gap amount between the second movable iron core <NUM> and the second fixed iron core <NUM>, which are determined by the regulation member, can be changed as appropriate.

In the solenoid S, when the coil <NUM> is excited, a magnetic path is formed so as to pass through the first fixed iron core <NUM>, the first movable iron core <NUM>, the second movable iron core <NUM>, the second fixed iron core <NUM>, and the case portion 11a, and the first movable iron core <NUM> is attracted to the first fixed iron core <NUM>, whereas the second movable iron core <NUM> is attracted to the second fixed iron core <NUM>. In other words, when the coil <NUM> is excited, the first movable iron core <NUM> and the second movable iron core <NUM> are attracted in a direction away from each other.

There is no regulation member such as the first leaf spring <NUM> and the second leaf spring <NUM> between the first movable iron core <NUM> and the first fixed iron core <NUM>. For this reason, when the amount of current supplied to the solenoid S is larger than or equal to a predetermined value, the first movable iron core <NUM> moves upward against the biasing force of the coil spring <NUM> to be adsorbed to the first fixed iron core <NUM>. In such a state, the biasing force of the coil spring <NUM> is not transmitted to the second movable iron core <NUM>.

However, in the present embodiment, the biasing force of the coil spring <NUM> is transmitted via the first movable iron core <NUM> and the first leaf spring <NUM> to the second movable iron core <NUM> until the first movable iron core <NUM> is adsorbed. In other words, the second movable iron core <NUM> is biased downward by the biasing force of the coil spring <NUM> until the first movable iron core <NUM> is adsorbed.

An insertion hole 43a is formed in a central portion of the second fixed iron core <NUM> so as to axially penetrate the second fixed iron core <NUM>. A shaft portion 9d of the valve body <NUM> of the solenoid valve <NUM> is movably inserted into the insertion hole 43a, and a distal end of the shaft portion 9d abuts against a lower end of the second fixed iron core <NUM>. Consequently, when the second movable iron core <NUM> is biased downward by the biasing force of the coil spring <NUM>, or when the second movable iron core <NUM> is attracted downward (to second fixed iron core <NUM>) when the solenoid S is energized, a downward force acts on the valve body <NUM>, that is, a force acts in a direction to push down the valve body <NUM>.

<FIG> illustrates a relationship between the amount of current supplied to the solenoid S and a force applied by the solenoid S in a direction to push down the valve body <NUM>. In <FIG>, Ia indicates the minimum amount of current required to adsorb the first movable iron core <NUM>, which is separated from the first fixed iron core <NUM>, to the first fixed iron core <NUM>. In addition, lb indicates the minimum amount of current required to keep the first movable iron core <NUM> adsorbed to the first fixed iron core <NUM>.

When the solenoid S is not energized, the biasing force of the coil spring <NUM> acts via the first movable iron core <NUM> and the second movable iron core <NUM> to push down the valve body <NUM>. Consequently, as illustrated in <FIG>, the valve body <NUM> can be biased downward by the solenoid S even when the solenoid S is not energized.

When the amount of current supplied to the solenoid S is increased from such a state, the force of attracting the first movable iron core <NUM> upward and the second movable iron core <NUM> downward increases. In a region where the amount of current supplied to the solenoid S is less than Ia, the biasing force of the coil spring <NUM> is transmitted to the valve body <NUM>, but a part of the force of the coil spring <NUM> that biases the first movable iron core <NUM> downward is offset by the force that attracts the first movable iron core <NUM>. As a result, in the region where the amount of current supplied to the solenoid S is less than Ia, the downward force applied by the solenoid S to the valve body <NUM> decreases as the amount of current supplied increases.

On the other hand, when the amount of current supplied to the solenoid S larger than or equal to Ia, the first movable iron core <NUM> is adsorbed to the first fixed iron core <NUM> and the biasing force of the coil spring <NUM> is not transmitted to the second movable iron core <NUM>. In such a state, only the force to attract the second movable iron core <NUM> acts in the direction to push down the valve body <NUM>. Since the force to attract the second movable iron core <NUM> increases in proportion to the amount of current supplied, in the region where the amount of current supplied to the solenoid S is larger than or equal to Ia, the downward force applied by the solenoid S to the valve body <NUM> increases as the amount of current supplied increases.

Conversely, as the amount of current supplied to the solenoid S is reduced, the force to attract the first movable iron core <NUM> upward and the second movable iron core <NUM> downward is reduced. In a region where the amount of current supplied to the solenoid S is larger than or equal to Ib, the first movable iron core <NUM> is kept adsorbed to the first fixed iron core <NUM>. As a result, in the region where the amount of current supplied to the solenoid S is larger than or equal to Ib, the downward force applied by the solenoid S to the valve body <NUM> is reduced as the amount of current supplied decreases.

When the amount of current supplied to the solenoid S is less than Ib, the first movable iron core <NUM> is separated from the first fixed iron core <NUM>. As a result, in the region where the amount of current supplied to the solenoid S is less than Ib, the downward force applied by the solenoid S to the valve body <NUM> increases as the amount of current supplied decreases.

In the present embodiment, the minimum amount Ib of current required to keep the adsorption of the first movable iron core <NUM> is less than the minimum amount Ia of current required for the adsorption (<FIG>). The characteristics of the force with respect to the amount of current supplied to the solenoid S are thus characteristics with hysteresis. Note that a region where the amount of supply current is small is exaggerated in <FIG>. Further, in a normal state where the solenoid valve <NUM> is energized, the amount of supply current is adjusted within the range of Ic or more, and Ic is set to be larger than or equal to Ib in the present embodiment.

In the normal state, once energization with la or more is performed to adsorb the first movable iron core <NUM> to the first fixed iron core <NUM>, and then the amount of current is set to a current value that is not less than or equal to lb. Consequently, in the normal state, the thrust of the solenoid S acting in the direction to push down the valve body <NUM> increases in proportion to the amount of supply current, and the valve opening pressure of the valve body <NUM> increases as the amount of supply current increases. Further, in a state where the valve body <NUM> is seated on the valve seat portion 8c, the thrust force of the solenoid S acts in a direction to close the main valve body <NUM> via the valve body <NUM> and the valve case <NUM>.

When the amount of current supplied to the solenoid valve <NUM> is increased in the normal state, the thrust of the solenoid S acting in the direction to close the main valve body <NUM> increases. At the same time, the valve opening pressure of the valve body <NUM> increases when the damper D is extended, and the pressure of the back pressure chamber L4 also increases, and the force to bias the main valve body <NUM> in the closing direction due to the pressure in the back pressure chamber L4 increases accordingly. When the damper D is contracted, the pressure control of the back pressure chamber L4 by the solenoid valve <NUM> does not work effectively, but if the amount of current supplied to the solenoid valve <NUM> is increased, the thrust force of the solenoid S acting in the direction to close the main valve body <NUM> is increased.

Consequently, when the amount of current supplied to the solenoid valve <NUM> is increased in the normal state, the first valve body member <NUM> and the second valve body member <NUM> are difficult to be opened, and the resistance when a liquid passes through these valve body members increases. As a result, when the amount of current supplied to the solenoid valve <NUM> is increased in the normal state, the damping force on the extension side and the compression side, which is generated by the damper D, increases, and thus hard damping force characteristics can be achieved.

Conversely, when the amount of current supplied to the solenoid valve <NUM> is reduced in the normal state, the thrust of the solenoid S acting in the direction to close the main valve body <NUM> decreases. At the same time, the valve opening pressure of the valve body <NUM> decreases when the damper D is extended, and the pressure of the back pressure chamber L4 also decreases, and the force to bias the main valve body <NUM> in the closing direction due to the pressure of the back pressure chamber L4 decreases accordingly. When the damper D is contracted, the pressure control of the back pressure chamber L4 by the solenoid valve <NUM> does not work effectively, but if the amount of current supplied to the solenoid valve <NUM> is reduced, the thrust force of the solenoid S acting in the direction to close the main valve body <NUM> is also reduced.

Consequently, when the amount of current supplied to the solenoid valve <NUM> is reduced in the normal state, the first valve body member <NUM> and the second valve body member <NUM> are easy to be opened, and the resistance when a liquid passes through these valve body members decreases. As a result, when the amount of current supplied to the solenoid valve <NUM> is reduced in the normal state, the damping force on the extension side and the compression side, which is generated by the damper D, decreases, and thus soft damping force characteristics can be achieved.

On the other hand, at the time of a failure in which the solenoid valve <NUM> is de-energized, the first movable iron core <NUM> is separated from the first fixed iron core <NUM> and the coil spring <NUM> functions, and thus a downward force due to the biasing force of the coil spring <NUM> acts on the valve body <NUM>.

When the damper D is extended at the time of a failure, the pressure of the back pressure chamber L4 is determined by the valve opening pressure of the valve body <NUM>. The valve opening pressure of the valve body <NUM> can be freely set by the characteristics of the coil spring <NUM>. In the state where the valve body <NUM> is seated on the valve seat portion 8c, the downward force due to the biasing force of the coil spring <NUM> acts in the direction to close the main valve body <NUM> via the valve body <NUM> and the valve case <NUM>.

Consequently, if the coil spring <NUM> that can apply a large biasing force is used, for example, a force to bias the main valve body <NUM> in the closing direction by the solenoid S itself can be increased, and the valve opening pressure of the valve body <NUM> can be set high. As a result, the resistance applied by the main valve body <NUM> to a flow of a liquid passing through the main passage P1 can be increased and the damping force on the extension side and the compression side of the damper D at the time of a failure can be increased.

More specifically, when the state where the amount of current supplied to the solenoid valve <NUM> in the normal state is set to the minimum amount (Ic) is referred to as "full soft state", the damping force on the extension side and the compression side of the damper D at the time of a failure can be set larger than a damping force in a full soft state. It is thus possible to prevent the damping force at the time of a failure from becoming insufficient.

Further, even if the damping force at the time of a failure is made larger than the damping force in the full soft state, the biasing force of the coil spring <NUM> can be canceled when the solenoid valve <NUM> is energized. The damping force does not become excessive in the full soft state. In addition, in the normal state, only a small amount of current supplied to the solenoid valve <NUM> is required when soft damping force characteristics are achieved, and thus when soft damping force characteristics are achieved during a normal traveling of a vehicle having the damper D mounted thereon, the power consumption can be reduced. Moreover, heat generation of the solenoid S can be reduced and a change in the liquid temperature of the damper D can be made small, so that the change in damping force characteristics due to the change in the liquid temperature can be made small.

Hereinafter, the operations and effects of the solenoid S, the solenoid valve <NUM> including the solenoid S, and the damper D that has the solenoid valve <NUM> including the solenoid S according to the present embodiment will be described.

In the present embodiment, the solenoid S includes the coil <NUM>, the first movable iron core <NUM> and the second movable iron core <NUM> that are attracted in a direction away from each other by energizing the coil <NUM>, the coil spring (biasing member) <NUM> that biases the first movable iron core <NUM> toward the second movable iron core <NUM>, and the first leaf spring (regulation member) <NUM> that restricts the approach of the first movable iron core <NUM> and the second movable iron core <NUM>.

According to the above configuration, the biasing force of the coil spring <NUM> can be canceled by the force to attract the first movable iron core <NUM> when the solenoid S is energized, and an object such as the valve body <NUM> can be biased in one direction by the force to attract the second movable iron core <NUM>. Since the force to attract the second movable iron core <NUM> becomes smaller as the amount of current supplied to the solenoid S becomes smaller, the thrust applied to the valve body <NUM> can be made small when the amount of current supplied to the solenoid S is small.

Further, according to the above configuration, the attraction of the first movable iron core <NUM> is released when the solenoid S is not energized, and the biasing force of the coil spring <NUM> is transmitted via the first movable iron core <NUM>, the first leaf spring <NUM>, and the second movable iron core <NUM> to the valve body <NUM>. The direction in which the biasing force of the coil spring <NUM> acts on the valve body <NUM> is the same as the direction of the force that attracts the second movable iron core <NUM>, and thus the valve body <NUM> can be biased in the same direction as the direction of the thrust at the time of energization even when the solenoid S is not energized.

That is, according to the above configuration, when the amount of current supplied to the solenoid S is small, the thrust of the solenoid S that biases the valve body (object) <NUM> in one direction can be made small, and the valve body (object) <NUM> can be biased in the same direction as the direction of the thrust even when the solenoid S is not energized.

Moreover, the solenoid S according to the present embodiment includes the first fixed iron core <NUM> and the second fixed iron core <NUM> that are arranged with a predetermined distance therebetween. The predetermined distance is a distance at which the first movable iron core <NUM> and the second movable iron core <NUM> can approach or be separated from each other between the first fixed iron core <NUM> and the second fixed iron core <NUM>, and can be freely set. The first movable iron core <NUM> and the second movable iron core <NUM> are disposed between the first fixed iron core <NUM> and the second fixed iron core <NUM> so as to be able to approach or be separated from each other.

Further, the first movable iron core <NUM> is disposed on a side of the second movable iron core <NUM> facing the first fixed iron core <NUM>, and is attracted to the first fixed iron core <NUM> by energizing the coil <NUM>. On the other hand, the second movable iron core <NUM> is disposed on a side of the first movable iron core <NUM> facing the second fixed iron core <NUM>, and is attracted to the second fixed iron core <NUM> by energizing the coil <NUM>. For this reason, it is easy to attract the first movable iron core <NUM> and the second movable iron core <NUM> in a direction away from each other by energizing the coil <NUM>.

Furthermore, in the solenoid S according to the present embodiment, both the first movable iron core <NUM> and the second movable iron core <NUM> have a cylindrical shape with a bottom, and the respective bottom portions 45a and 46a face the second fixed iron core <NUM>. The first movable iron core <NUM> is movably inserted into the inside of the second movable iron core <NUM>. The biasing member that biases the first movable iron core <NUM> toward the second movable iron core <NUM> is the coil spring <NUM>. The coil spring <NUM> is inserted into the inside of the first movable iron core <NUM> and is interposed between the bottom portion 45a of the first movable iron core <NUM> and the first fixed iron core <NUM>.

According to the above configuration, when the coil <NUM> is excited, a magnetic path is formed so as to pass through the first fixed iron core <NUM>, the first movable iron core <NUM>, the second movable iron core <NUM>, and the second fixed iron core <NUM>. It is thus easy to attract the first movable iron core <NUM> to the first fixed iron core <NUM> and attract the second movable iron core <NUM> to the second fixed iron core <NUM>. Since the coil spring <NUM> functioning as the biasing member is housed inside the first movable iron core <NUM>, it is possible to prevent the solenoid S from extending in the axial direction.

However, if the first movable iron core <NUM> and the second movable iron core <NUM> are attracted in the direction away from each other by energizing the coil <NUM>, any fixed iron core may be provided, and the configurations of the first movable iron core <NUM> and the second movable iron core <NUM> can be changed as appropriate. Further, the configuration of the biasing member is not limited to a coil spring, and can be changed as appropriate.

Moreover, the solenoid S according to the present embodiment includes the leaf spring <NUM> that is a first regulation member that restricts the approach of the first movable iron core <NUM> and the second movable iron core <NUM> and the leaf spring <NUM> that is a second regulation member that restricts the approach of the second movable iron core <NUM> and the second fixed iron core <NUM>. It is thus possible to prevent the first movable iron core <NUM> from being adsorbed to the second movable iron core <NUM> and the second movable iron core <NUM> from being adsorbed to the second fixed iron core <NUM>.

However, the configurations of the first and second regulation members are not limited to the leaf springs <NUM> and <NUM>, and can be changed as appropriate. Such changes can be made regardless of the arrangement of a fixed iron core in order to attract the first movable iron core <NUM> and the second movable iron core <NUM> in the direction away from each other, the configurations of the first movable iron core <NUM> and the second movable iron core <NUM>, and the configuration of the biasing member.

In the solenoid S according to the present embodiment, the first movable iron core <NUM> is set to be adsorbed to the first fixed iron core <NUM> by energizing the coil <NUM>. The minimum amount la of current required to adsorb the first movable iron core <NUM> to the first fixed iron core <NUM> is larger than the minimum amount Ib of current required to keep the first movable iron core <NUM> adsorbed to the first fixed iron core <NUM>.

The characteristics of the thrust of the solenoid S with respect to the amount of current supplied to the coil <NUM> have characteristics with hysteresis. Furthermore, in a state where the first movable iron core <NUM> is adsorbed to the first fixed iron core <NUM>, the biasing force of the coil spring <NUM> is not transmitted to the second movable iron core <NUM>. When the first movable iron core <NUM> is adsorbed to the first fixed iron core <NUM>, it is possible to stably keep such a state.

However, if the second movable iron core <NUM> is configured not to receive the biasing force of the coil spring <NUM> when the amount of current supplied to the coil <NUM> is larger than or equal to a predetermined amount, the first movable iron core <NUM> is not necessarily adsorbed to the first fixed iron core <NUM>. Further, the minimum amount la of current required to adsorb the first movable iron core <NUM> and the minimum amount Ib of current required to keep the adsorption of the first movable iron core <NUM> can be freely set.

Moreover, in the present embodiment, the solenoid S is used for the solenoid valve <NUM> disposed partway in the pressure control passage P4, and the solenoid valve <NUM> includes the valve body <NUM> that opens and closes the pressure control passage P4. The valve body <NUM> is biased in the closing direction by the force to attract the second movable iron core <NUM> due to energization of the coil <NUM>, and the valve opening pressure of the valve body <NUM> is adjusted by the solenoid S. The pressure on the upstream side of the solenoid valve <NUM> is controlled by the valve opening pressure of the valve body <NUM>, and the solenoid valve <NUM> can function as a pressure control valve.

Further, in the present embodiment, the solenoid valve <NUM> is used for the damper D, and the damper D includes the cylinder <NUM>, the piston <NUM> that is slidably inserted into the cylinder <NUM> and partitions the inside of the cylinder <NUM> into the extension-side chamber L1 and the compression-side chamber L2, the main passage P1 that causes the extension-side chamber L1 to communicate with the compression-side chamber L2, the annular valve seat member <NUM> through which the main passage P1 passes on its inner circumferential side, the main valve body <NUM> that is seated on and separated from the valve seat member <NUM> to apply a resistance to a flow of a liquid passing through the main passage P1, the extension-side pressure introduction passage P2 that includes the orifice O1 partway to reduce the pressure of the extension-side chamber L1 and guide the reduced pressure to the back surface of the main valve body <NUM>, the compression-side pressure introduction passage P3 that reduces the pressure of the compression-side chamber L2 and guides the reduced pressure to the back surface of the main valve body <NUM>, and the pressure control passage P4 that is connected downstream of the orifice O1 in the extension-side pressure introduction passage P2, and the solenoid valve <NUM> is disposed partway in the pressure control passage P4.

The main valve body <NUM> include the first valve body member <NUM> that has an annular shape and is seated on and separated from the valve seat member <NUM> and the second valve body member <NUM> that is stacked on the first valve body member <NUM> (side opposite to valve seat member), and is seated on and separated from the first valve body member <NUM>. The first valve body member <NUM> and the second valve body member <NUM> are biased in the direction away from the valve seat member <NUM> by the pressure of the extension-side chamber L1. On the other hand, the second valve body member <NUM> is biased in the direction away from the first valve body member <NUM> by the pressure on the inner circumferential side of the first valve body member <NUM>. Further, the first valve body member <NUM> and the second valve body member <NUM> are biased toward the valve seat member <NUM> by the force to attract the second movable iron core <NUM> due to the energization of the coil <NUM>.

According to the above configuration, when the biasing force of the coil spring <NUM> is canceled by the attraction of the first movable iron core <NUM> in the normal state, the thrust applied to the valve body <NUM> and the main valve body <NUM> in the closing direction increases as the amount of current supplied to the solenoid S is increased, so that hard damping force characteristics are achieved. In other words, when soft damping force characteristic are achieved, only a small amount of current supplied to the solenoid S is required. When the damper D is mounted on a vehicle, the power consumption during normal traveling can be reduced. Moreover, heat generation of the solenoid S can be reduced and a change in the liquid temperature of the damper D can be made small, so that the change in damping force characteristics due to the change in the liquid temperature can be made small.

Furthermore, according to the above configuration, the attraction of the first movable iron core <NUM> is released at the time of a failure, and the coil spring (biasing member) <NUM> can bias the valve body <NUM>, the first valve body member <NUM>, and the second valve body member <NUM> so as to close these members. Consequently, the valve opening pressure of the valve body <NUM> at the time of a failure can be determined by the setting of the coil spring <NUM>, and the first valve body member <NUM> or the second valve body member <NUM> can apply a predetermined resistance to a flow of a liquid passing through the main passage P1.

As described above, the biasing force of the coil spring <NUM> is canceled in the normal state, the damper D can apply a larger damping force than that in the full soft state at the time of a failure, and thus it is possible to prevent the damping force from becoming insufficient at the time of a failure. In addition, according to the above configuration, the liquid can pass through the pressure control passage P4 even at the time of a failure, and thus it is not necessary to provide a passage for allowing the flow of the liquid at the time of a failure in addition to the passage for pressure control. Therefore, the configuration of the damper D can be simplified and the cost can be reduced.

However, the configuration of the passage in which the solenoid valve <NUM> including the solenoid S is provided can be changed as appropriate, and the configuration of the damper D including the solenoid valve <NUM> can also be changed as appropriate. For example, when the damper includes a reservoir as described above, the main passage having the main valve body <NUM> whose back pressure is controlled by the solenoid valve <NUM> may cause the extension-side chamber or the compression-side chamber to communicate with the reservoir, or the extension-side valve <NUM> and the compression-side valve <NUM> may be eliminated. In addition, it is needless to mention that the solenoid valve <NUM> may be used in various devices other than the damper D, and the solenoid S may also be used in various devices other than the solenoid valve <NUM> functioning as a pressure control valve.

Such changes can be made regardless of the arrangement of a fixed iron core in order to attract the first movable iron core <NUM> and the second movable iron core <NUM> in the direction away from each other, the configurations of the first movable iron core <NUM> and the second movable iron core <NUM>, the configuration of the biasing member, and the configuration of the regulation member.

Claim 1:
A solenoid, comprising:
a coil (<NUM>);
a first movable iron core (<NUM>) and a second movable iron core (<NUM>) that are attracted in a direction away from each other by energizing the coil (<NUM>);
a biasing member that biases the first movable iron core (<NUM>) toward the second movable iron core (<NUM>);
a first regulation member that restricts approach of the first movable iron core (<NUM>) and the second movable iron core (<NUM>); and
a first fixed iron core (<NUM>) and a second fixed iron core (<NUM>) that are arranged with a predetermined distance between the first fixed iron core (<NUM>) and the second fixed iron core (<NUM>), wherein
the first movable iron core (<NUM>) and the second movable iron core (<NUM>) have a cylindrical shape with a bottom, and are disposed between the first fixed iron core (<NUM>) and the second fixed iron core (<NUM>) so as to be able to approach or be separated from the first fixed iron core (<NUM>) and the second fixed iron core (<NUM>), respectively, and bottom portions of the first movable iron core (<NUM>) and the second movable iron core (<NUM>) face the second fixed iron core (<NUM>),
the first movable iron core (<NUM>) is movably inserted into an inside of the second movable iron core (<NUM>), and is disposed on a side of the second movable iron core (<NUM>) facing the first fixed iron core (<NUM>) to be attracted to the first fixed iron core (<NUM>) by energizing the coil (<NUM>),
the biasing member is a coil spring (<NUM>), and is inserted into an inside of the first movable iron core (<NUM>) to be interposed between the bottom portion of the first movable iron core (<NUM>) and the first fixed iron core (<NUM>), and
the second movable iron core (<NUM>) is disposed on a side of the first movable iron core (<NUM>) facing the second fixed iron core (<NUM>) to be attracted to the second fixed iron core (<NUM>) by energizing the coil (<NUM>).