Linear solenoid and manufacturing method of the same

An inner diameter of a third stator core is greater than an inner diameter of a second stator core. When a first stator core, the second stator core, and the third stator core are placed in an inner periphery of a coil, a jig is inserted from an inner-periphery opening of a first end side of the third stator core into the third stator core to directly position the first stator core, the second stator core, and the third stator core in a radial direction. Therefore, a side force generated by an axis deviation between the first stator core, the second stator core, and the third stator core can be reduced.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2013-193686 filed on Sep. 19, 2013, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD The present disclosure relates to a linear solenoid which outputs a force acting in an axial direction.

BACKGROUND

JP-2005-045217A (US 2004/0257185 A1) discloses a linear solenoid mounted to a vehicle outputs a thrust using a magnetic flux generated according to an energization of a coil.

In the linear solenoid, a movement amount of a movable core in an axial direction can be increased without increasing a size of the linear solenoid in the axial direction. The movable core includes a cylindrical portion. Stator cores are placed at positions inside of the movable core and outside of the movable core, respectively.

A better configuration of the linear solenoid according to JP-2005-045217A includes the movable core, a first stator core, a second stator core, and a third stator core, which are made of magnetic material.

The movable core includes a magnetic portion having a cylindrical shape, and is placed in an inner periphery of the coil and is movable with respect to an axial direction concentric with the coil. The first stator core is placed at a position inside of an inner periphery of the movable core, and the first stator core receives and transmits the magnetic flux in a radial direction of the movable core. The second stator core is a magnetic portion having a cylindrical shape, and is placed at a position outside of an outer periphery of the movable core such that the movable core is interposed between the first stator core and the second stator core. The second stator core receives and transmits the magnetic flux in the radial direction of the movable core. The third stator core is placed at a position such that the third stator core is not in contact with the second stator core in the axial direction. The third stator core magnetically attracts the movable core in the axial direction.

However, the first stator core, the second stator core, and the third stator core can be directly positioned in the radial direction.

According to JP-2005-045217A, a magnetic portion provided integrally with the first stator core and a magnetic portion provided integrally with the second stator core are fitted to each other to position the first stator core and the second stator core in the axial direction.

Therefore, the first stator core, the second stator core, and the third stator core is insufficiently positioned in the radial direction, and it is possible that a side force generated by an axis deviation between the first stator core, the second stator core, and the third stator core increases. In this case, the side force is an attractive force generated between the movable core, the first stator core, the second stator core, and the third stator core, in the radial direction.

SUMMARY

The present disclosure is made in view of the above matters, and it is an object of the present disclosure to provide a linear solenoid in which a movable core includes a cylindrical portion and stator cores are placed at inner and outer periphery of the cylindrical portion, so as to reduce a side force.

According to an aspect of the present disclosure, a linear solenoid outputs a thrust in an axial direction using a magnetic flux generated according to an energization of a coil. The linear solenoid includes a movable core, a first stator core, a second stator core, and a third stator core.

The movable core includes a magnetic portion having a cylindrical shape, and is placed in an inner periphery of the coil and is movable with respect to an axial direction concentric with the coil. The first stator core made of magnetic material is placed at a position inside of an inner periphery of the movable core, and the first stator core receives and transmits the magnetic flux in a radial direction of the movable core.

The second stator core is a magnetic portion having a cylindrical shape, and is placed at a position outside of an outer periphery of the movable core such that the movable core is interposed between the first stator core and the second stator core. The second stator core receives and transmits the magnetic flux in the radial direction of the movable core. The third stator core is a magnetic portion having a cylindrical shape, and is placed at a position of the first end side in the axial direction with respect to the second stator core such that the third stator core is not in contact with the second stator core. The third stator core magnetically attracts the movable core toward the first end side of the movable core into the inner periphery of the third stator core, the third stator core including an inner-periphery opening at a first end side in the axial direction where the inner-periphery opening is blocked by a cover. The third stator core has an inner diameter that is greater than an inner diameter of the second stator core.

When the first stator core, the second stator core, and the third stator core are placed in the inner periphery of the coil, a jig is inserted from an inner-periphery opening of a first end side of the third stator core into the third stator core to directly position the first stator core, the second stator core, and the third stator core in a radial direction. Therefore, a side force generated by an axis deviation between the first stator core, the second stator core, and the third stator core can be reduced. In this case, the side force is an attractive force generated between the movable core, the first stator core, the second stator core, and the third stator core, in the radial direction.

DETAILED DESCRIPTION

Referring to drawings, a linear solenoid1according to an embodiment of the present disclosure will be described.

The linear solenoid1generates a magnetic attractive force as a thrust using a magnetic flux generated according to an energization of a coil2. For example, the linear solenoid1may be mounted to a vehicle to be applied to a supplier supplying an oil pressure of a valve-timing mechanism that changes a valve timing of an internal combustion engine.

The linear solenoid1includes a movable core3, a first stator core4, a second stator core5, and a third stator core6. The first stator core4, the second stator core5, and the third stator core6correspond to magnetic portions.

The movable core3is a magnetic body having a cylindrical shape, and is placed in an inner periphery of the coil2and is movable with respect to an axial direction concentric with the coil2. Alternatively, the movable core3may be a member including the magnetic body. The movable core3includes a first introducing passage8through which a fluid is introduced between a first end side of the movable core3and a second end side of the movable core3in the axial direction. As shown inFIGS. 2A and 2B, two first introducing passages8are provided in an inner peripheral surface of the movable core3at a 180-degrees interval. The first introducing passages8are both provided to penetrate the movable core3in the axial direction and correspond to grooves opened to the inner peripheral surface of the movable core3.

The first stator core4having a cylindrical shape is a part of a first magnetic body9. The first magnetic body9corresponds to a fixed member. The first stator core4is placed at a position inside of an inner periphery of the movable core3, and slidably supports the movable core3in the axial direction. The first stator core4receives and transmits the magnetic flux in a radial direction of the movable core3.

The second stator core5is having a cylindrical shape is a part of a second magnetic body10that is different from the first magnetic body9. The second stator core5is placed at a position outside of an outer periphery of the movable core3such that the movable core3is interposed between the first stator core4and the second stator core5. The second stator core5receives and transmits the magnetic flux in the radial direction of the movable core3. In addition, a gap is generated between an inner peripheral surface of the second stator core5and an outer peripheral surface of the movable core3. The movable core3slides in the axial direction without being in contact with the second stator core5.

The third stator core6having a cylindrical shape is a part of a third magnetic body11that is different from the first magnetic body9and the second magnetic body10. The third stator core6is concentric with the second stator core5and is placed at a position of the first end side in the axial direction with respect to the second stator core5such that the third stator core6is not in contact with the second stator core5. The third stator core6magnetically attracts the movable core3toward the first end side of the movable core3into an inner periphery of the third stator core6.

A cover12is provided to block an inner-periphery opening of a first end side of the third stator core6in the axial direction. The cover12is different from the first magnetic body9, the second magnetic body10, and the third magnetic body11. The first end side of the third stator core6is opposite to a second end side of the third stator core6where the second stator core5is placed. The cover12prevents a foreign matter from entering the linear solenoid1from external. The cover12includes a cover portion13having an angled shape such as an umbrella, and the cover portion13is placed at a first end side of the cover12in the axial direction to prevent the foreign matter from entering the linear solenoid1from external. The cover12further includes a first cylindrical portion14which is pressed into the inner periphery of the third stator core6. An area for receiving and transmitting the magnetic flux increases according to the first cylindrical portion14.

As shown inFIG. 3, in the linear solenoid1, an inner diameter a of the third stator core6is greater than an inner diameter b of the second stator core5. The inner diameter a and the inner diameter b are greater than an outer diameter c of the first stator core4. When the first stator core4, the second stator core5, and the third stator core6are placed in the inner periphery of the coil2, a jig15is inserted from the inner-periphery opening of the first end side of the third stator core6into the third stator core6to directly position the first stator core4, the second stator core5, and the third stator core6in the radial direction.

The linear solenoid1further includes a first receiving and transmitting mechanism (first R/T mechanism) a and a second R/T mechanism β.

The first R/T mechanism a makes a magnetic portion of the second magnetic body10different from the second stator core5be in contact with a magnetic portion of the third magnetic body11different from the third stator core6, so as to receives and transmits the magnetic flux between the magnetic portion of the second magnetic body10and the magnetic portion of the third magnetic body11.

The second magnetic body10includes a second end yoke16having a ring-plate shape. The second end yoke16outwardly extends from a second end side of the second stator core5and covers a second end side of the coil2, in the axial direction. The third magnetic body11includes a first end yoke17having a ring-plate shape, and an outer yoke18. The first end yoke17outwardly extends from the first end side of the third stator core6and covers a first end side of the coil2, in the axial direction. The outer yoke18having a cylindrical shape extends from an outer periphery of the first end yoke17toward a second end side of the axial direction and covers the coil2. The third magnetic body11further includes a first flange portion19. The first flange portion19having a ring-plate shape outwardly extends from a second end side of the outer yoke18in the axial direction.

The second end yoke16includes a first outer-periphery portion20which is in surface contact with the first flange portion19according to the first R/T mechanism α. Therefore, the magnetic flux is received and transmitted between the first outer-periphery portion20and the first flange portion19.

The second end yoke16extends to a position outside of an outer periphery of the coil2, and the first outer-periphery portion20is placed at a position outside of the outer periphery of the coil2. The first outer-periphery portion20includes a first outer-periphery surface20aat a first end side of the first outer-periphery portion20. The first outer-periphery surface20ais a surface perpendicular to the axial direction. The first flange portion19includes a flange surface19bat a second end side of the first flange portion19. The flange surface19bis a surface perpendicular to the axial direction.

Since the first outer-periphery surface20aand the flange surface19bare in surface contact with each other, the magnetic flux is received and transmitted between the second magnetic body10and the third magnetic body11, outside of the coil2.

In addition, since the first flange portion19and the first outer-periphery portion20are not fitted to each other by a male-female fitting, the first flange portion19and the first outer-periphery portion20can relatively move with respect to each other in the radial direction in a case where the jig15positions the second magnetic body10and the third magnetic body11.

The second R/T mechanism β makes a magnetic portion of the first magnetic body9different from the first stator core4be in contact with a magnetic portion of the second magnetic body10different from the second stator core5, so as to receives and transmits the magnetic flux between the magnetic portion of the first magnetic body9and the magnetic portion of the second magnetic body10.

The first magnetic body9includes a second flange portion21. The second flange portion21having a ring-plate shape outwardly extends from a second end side of the first stator core4in the axial direction.

The second end yoke16further includes a first inner-periphery portion23which is in surface contact with a second outer-periphery portion24of the second flange portion21according to the second R/T mechanism β. Therefore, the magnetic flux is received and transmitted between the first inner-periphery portion23and the second outer-periphery portion24.

The second flange portion21extends to a position outside of the outer periphery of the movable core3, and the second outer-periphery portion24is placed at a position outside of the outer periphery of the movable core3. The first inner-periphery portion23includes an inner-periphery surface23bat a second end side of the first inner-periphery portion23. The inner-periphery surface23bis a surface perpendicular to the axial direction. The second outer-periphery portion24includes a second outer-periphery surface24aat a first end side of the second outer-periphery portion24. The second outer-periphery surface24ais a surface perpendicular to the axial direction.

Since the second outer-periphery surface24aand the inner-periphery surface23bare in surface contact with each other, the magnetic flux is received and transmitted between the first magnetic body9and the second magnetic body10, at a position adjacent to the second end side of the coil2.

In addition, since the first inner-periphery portion23and the second outer-periphery portion24are not fitted to each other by a male-female fitting, the first inner-periphery portion23and the second outer-periphery portion24can relatively move with respect to each other in the radial direction in a case where the jig15positions the first magnetic body9and the second magnetic body10.

The first R/T mechanism α is placed at a first end side of the axial direction of the second R/T mechanism β.

The linear solenoid1further includes a notch portion25which penetrates the second end yoke16in the axial direction. The coil2includes a terminal26extends from the notch portion25. The first R/T mechanism α is placed at the first end side of the terminal26.

The linear solenoid1further includes a bearing28, an output member29, and a bobbin30.

The bearing28is fixed to the inner periphery of the movable core3and directly slides with respect to the first stator core4. The movable core3indirectly slides with respect to the first stator core4via the bearing28. The bearing28includes an outer-periphery part that is made of magnetic material, and an inner-periphery part that is made of non-magnetic material. The bearing28further includes an inner periphery surface that is made of non-magnetic material and is directly in contact with an outer periphery surface of the first stator core4.

A first area is an area in the inner periphery surface of the movable core3where the magnetic flux can be received and transmitted between the inner periphery surface of the movable core3and the outer periphery surface of the first stator core4in the radial direction. A length of the first area in the axial direction is referred to as a first length d. A second area is an area in the outer periphery surface of the first stator core4where the magnetic flux can be received and transmitted between the outer periphery surface of the first stator core4and the inner periphery surface of the movable core3in the radial direction. A length of the second area in the axial direction is referred to as a second length e. As shown inFIG. 4, the first length d is less than the second length e. Further, the first length d is substantially equal to a length of the bearing in the axial direction.

The bearing28includes a third flange portion32which outwardly extends from a second end side of the bearing28in the axial direction. The third flange portion32limits a movement of the movable core3toward the second end side of the axial direction by being in contact with a second inner-periphery portion33of the second flange portion21. The third flange portion32includes a first end part that is placed at a first end side of the third flange portion32and is made of magnetic material, and a second end part that is placed at a second end side of the third flange portion32and is made of non-magnetic material. The third flange portion32further includes an abutting surface32bthat is made of non-magnetic material and is directly in contact with the second inner-periphery portion33.

As shown inFIG. 5, second introducing passages34are provided in a surface of a first end side of the second inner-periphery portion33in the axial direction as grooves through which the fluid is introduced between an inner periphery of the third flange portion32and an outer periphery of the third flange portion32. According to the present embodiment, the second introducing passages34are provided around an axial center of the linear solenoid1at a 60-degrees interval. Further, the second introducing passages34are radially placed.

The output member29that is made of non-magnetic material is fixed to the movable core3, and moves together with the movable core3toward a first end side of the axial direction to outputs the thrust. When the output member29receives a recovery force from an external device, the output member29is moved together with the movable core3toward the second end side of the axial direction.

The output member29includes a fixed portion36and a shaft portion37. The fixed portion36is a cylindrical shape and is fixed to the movable core3to be concentric with the movable core3. The shaft portion37is a column shape and extends toward the first end side of the axial direction.

The inner periphery of the movable core3includes a step surface at the first end side of the movable core3in the axial direction. A diameter of the step surface is greater than a diameter of a common part of the inner periphery. In this case, the common part of the inner periphery is a part of the inner periphery other than the step surface. The fixed portion36is inserted into an area including the step surface and is fixed to the movable core3. The bearing28is inserted into an area including the common part and is fixed to the movable core3. As shown inFIG. 2A, a gap f is generated between the bearing28and the fixed portion36. The gap f communicates with the first introducing passage8.

An opening38is formed by the cover portion13such that the shaft portion37penetrating the opening38in the axial direction. Therefore, the shaft portion37outputs the thrust to external devices.

The shaft portion37has a diameter less than a diameter of the fixed portion36. The shaft portion37and the fixed portion36are seamlessly bonded to each other via a taper portion39. The taper portion39expanses its diameter toward the second end side of the axial direction. A first end side of the first stator core4relatively moves with respect to an inner periphery of the fixed portion36. The first end side of the first stator core4is chamfered to have a taper shape. Even though the movable core3and the output member29moves to positions most close to the second end side of the first stator core4, an inner periphery of the taper portion39are not in contact with the first stator core4.

The bobbin30is a member made of resin and is wound by the coil2. The bobbin30includes a second cylindrical portion40, a fourth flange portion41a, and a fifth flange portion41b.

The second cylindrical portion40is placed at a position outside of both the second stator core5and the third stator core6. The second cylindrical portion40is wound by the coil2. The fourth flange portion41aand the fifth flange portion41boutwardly extend from a first end side of the second cylindrical portion40and a second of the second cylindrical portion40, respectively, so as to define a coil area where the coil2is wound. The linear solenoid1includes a first end seal γ and a second end seal δ which protect the coil2from the fluid entering the linear solenoid1.

The first end seal γ is provided to surround an axial center of the coil2at a first end side of the fourth flange portion41ain the axial direction. As shown inFIG. 6, a first protrusion42athat is made of resin and has a ring shape surrounds the axial center of the coil2at a surface of the first end side of the fourth flange portion41a. The first end seal γ is provided by being solidified after being melted according to a melting resin at the first protrusion42a.

The second end seal δ is provided to surround the axial center of the coil2at a second end side of the fifth flange portion41bin the axial direction. A second protrusion42bthat is made of resin and has a ring shape surrounds the axial center of the coil2at a surface of the second end side of the fifth flange portion41b. The second end seal δ is provided by being solidified after being melted according to a melting resin at the second protrusion42b.

A manufacturing method of the linear solenoid1includes an injection molding step which injects a melting resin and molds the coil2, the first magnetic body9, the second magnetic body10, the third magnetic body11, the bobbin30, and an attachment bracket43. Further, the first end seal γ, the second end seal δ, a connector44, and a groove receiving an O-ring45are formed by the melting resin injected in the injection molding step.

As shown inFIG. 3, an injection opening (not shown) of the melting resin in the injection molding step is placed at a position in an area g that is opposite to a second end side of the first magnetic body9.

The second end yoke16has a shape that does not interfere with the second protrusion42b. For example, the second end yoke16is not in contact with the second protrusion42b. The second end yoke16further includes an intermediate portion46placed between the first inner-periphery portion23and the first outer-periphery portion20. The intermediate portion46extends toward the second end side of the axial direction. As shown inFIG. 3, the intermediate portion46and the fifth flange portion41bform a space47into which the second protrusion42bprotrudes. The melting resin is filled in the space47.

The linear solenoid1further includes a penetrating hole49that penetrates the third stator core6. The penetrating hole49communicates an interior of the linear solenoid1with an exterior of the linear solenoid1. The penetrating hole49is opened at a position of the linear solenoid1outward of an inner-peripheral wall6aof the third stator core6. According to the present embodiment, the penetrating hole49is parallel to the axial center of the linear solenoid1. Further, a plurality of the penetrating holes49is provided around the axial center of the coil2. As shown inFIG. 7, for example, the penetrating holes49may be provided around the axial center of the coil2at a 45-degrees interval.

The linear solenoid1is mounted to the vehicle such that the axial direction is substantially parallel to a horizontal direction. In this case, the connector44extends upward in a vertical direction with respect to gravity, and the attachment bracket43extends downward in the vertical direction with respect to gravity. Thus, as shown inFIG. 8, a fluid level in the linear solenoid1is controlled to be lower than the inner-peripheral wall6aof the third stator core6.

In the linear solenoid1, when the coil2is energized, the magnetic flux is received and transmitted in the radial direction between the first stator core4, the second stator core5, and the movable core3. Further, the magnetic flus is received and transmitted in the radial direction between the movable core3and the third stator core6, and the movable core3is attracted and moved toward the first end side of the axial direction. Thus, the linear solenoid1outputs the thrust in the axial direction.

According to the present embodiment, the linear solenoid1includes the movable core3having a cylindrical shape, and the first stator core4and the second stator core5which are placed at positions inward of the movable core3and outward of the movable core3, respectively. The magnetic flux is received and transmitted in the radial direction from both the first stator core4and the second stator core5. The third stator core6is a magnetic portion and is placed at a position of the first end side in the axial direction with respect to the second stator core5such that the third stator core6is not in contact with the second stator core5. The third stator core6magnetically attracts the movable core3toward the first end side of the movable core3into the inner periphery of the third stator core6. The cover12is provided to block the inner-periphery opening of the first end side of the third stator core6in the axial direction. In the linear solenoid1, the inner diameter a of the third stator core6is greater than the inner diameter b of the second stator core5.

When the first stator core4, the second stator core5, and the third stator core6are placed in the inner periphery of the coil2, the jig15is inserted from the inner-periphery opening of the first end side of the third stator core6into the third stator core6to directly position the first stator core4, the second stator core5, and the third stator core6in the radial direction. Therefore, a side force generated by an axis deviation between the first stator core4, the second stator core5, and the third stator core6can be reduced. In this case, the side force is an attractive force generated between the movable core, the first stator core, the second stator core, and the third stator core, in the radial direction.

The first R/T mechanism α is provided to receive and transmit the magnetic flux by making the second end yoke16of the second magnetic body10be in contact with the first flange portion19of the third magnetic body11. Specifically, the first R/T mechanism α receives and transmits the magnetic flux by making the first outer-periphery surface20abe in surface contact with the flange surface19b.

Therefore, since an area for receiving and transmitting the magnetic flux between the second magnetic body10and the third magnetic body11can be sufficiently ensured, the magnetic attractive force can be ensured by reducing a magnetic resistance.

The second R/T mechanism β is provided to receive and transmit the magnetic flux by making the second flange portion21of the first magnetic body9be in contact with the second end yoke16of the second magnetic body10. Specifically, the second R/T mechanism β receives and transmits the magnetic flux by making the second outer-periphery surface24abe in surface contact with the inner-periphery surface2b.

Therefore, since an area for receiving and transmitting the magnetic flux between the first magnetic body9and the second magnetic body10can be sufficiently ensured, the magnetic attractive force can be ensured by reducing a magnetic resistance.

The first R/T mechanism α is placed at the first end side of the axial direction of the second R/T mechanism β.

Therefore, a size of the linear solenoid1can be reduced in the axial direction. The second R/T mechanism β is necessary to be placed at a position adjacent to the second end side of the coil2. The first R/T mechanism α can be placed at one of a position outward of the coil2and a position inward of the coil2. Since the first R/T mechanism α is placed at the first end side of the axial direction of the second R/T mechanism β, the size of the linear solenoid1can be reduced in the axial direction.

The injection opening of the melting resin in the injection molding step of the linear solenoid1is placed at a position in an area g that is opposite to the second end side of the first magnetic body9. Further, the injection opening is placed at a position adjacent to a second end side of the second R/T mechanism β in the axial direction.

Thus, the first outer-periphery surface20acan be surely in surface contact with the flange surface19baccording to an injection pressure of the melting resin such that the first outer-periphery surface20ais fixed to the flange surface19b, and the second outer-periphery surface24acan be surely in surface contact with the inner-periphery surface23baccording to an injection pressure of the melting resin such that the second outer-periphery surface24ais fixed to the inner-periphery surface23b. It is unnecessary to provide specified positions for the above surfaces to meet each other according to the first R/T mechanism α and the second R/T mechanism β.

A configuration of the linear solenoid1is not limited to the present embodiment, various modifications can be applied.

According to the present embodiment, the first stator core4slidably supports the movable core3from the inner periphery of the movable core3. However, the second stator core5may slidably support the movable core3from the outer periphery of the movable core3. Alternatively, the second stator core5may slidably support the output member29.

According to the present embodiment, the second introducing passages34are provided in the second flange portion21of the first magnetic body9. However, the second introducing passages34may be provided in the third flange portion32of the bearing28. Alternatively, the second introducing passages34may be provided in both the second flange portion21and the third flange portion32.