WO2008099272A1

WO2008099272A1 - Electromagnetically driven valve

Info

Publication number: WO2008099272A1
Application number: PCT/IB2008/000335
Authority: WO
Inventors: Yutaka Sugie; Masahiko Asano
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-02-16
Filing date: 2008-02-14
Publication date: 2008-08-21
Also published as: JP2008202427A

Abstract

An electromagnetically driven valve includes a disk (21) and an electromagnet (51n, 51m). The disk (21) includes a support portion (23) pivotably supported, and pivots about the support portion (23) so that a valve is reciprocated. The electromagnet (51n, 51m) that exerts an electromagnetic force on the disk (21) includes a core (52) arranged so as to be faced to the disk (21), and a coil (53) wound around the core (52). When current is supplied to the coil (53), a First magnetic circuit (61) and a second magnetic circuit (62), in which a magnetic flux passing through the core (52) and the disk (21) flow, are formed. The core (52) has a first extending portion (52h) where the magnetic circuit (61) and the magnetic circuit (62) join. A slit (58) formed in the first extending portion (52h) that separates the magnetic flux flowing in the first magnetic circuit (61) from that flowing in the second magnetic circuit (62).

Description

ELECTROMAGNETICALLY DRIVEN VALVE

BACKGROUND OF THE TNVENTION

1. Field of the Invention The present invention relates to an electromagnetically driven valve. More specifically, the present invention relates to a pivot-type electromagnetically driven valve that drives a valve of an internal combustion engine to open and close.

2. Description of Related Art

As an example of electromagnetically driven valve, for example, US Patent No. 6467441 describes an electromagnetic actuator in λvhich a valve of an internal combustion engine is actuated by cooperation of an electromagnetic force and an elastic force of a spring. The electromagnetic actuator includes a valve having a stem, and an oscillating arm. The oscillating arm has a first end formed in a cylindrical shape and supported on a support frame so as to freely oscillate, and a second end abutted against the distal end of the stem. Electromagnets each including a core and a coil wound around the core are respectively arranged above and below the oscillating arm.

The electromagnetic actuator further includes a torsion bar provided at the first end of the oscillating arm and urging the valve in an opening direction, and a helical spring arranged on the outer circumference of the stem and urging the valve in a closing direction. Due to the electromagnetic force generated on the electromagnet and the elastic forces of the torsion bar and helical spring, the oscillating arm is alternately attracted to the cores of the electromagnets arranged above and below the oscillating arm.

Similar pivot-type electromagnetically driven valves are described in German Patent Application Publication No. 10025491, US Patent No. 7088209, US Patent No. 6571823, and US Patent No. 6481396.

In the electromagnetic actuator described in US Patent No. 6467441 mentioned above, a magnetic flux passing through the core of each electromagnet and the oscillating arm is formed, generating an electromagnetic force that attracts the oscillating arm to the core. However, unless the air gap between the oscillating arm and the core is uniform, there may be a case where a magnetic circuit in which a relatively large magnetic flux flows, and a magnetic circuit in which a relatively small magnetic flux flows are formed within the core, In this case, it becomes difficult to optimize the magnetic flux density at the position where the two magnetic circuits join. As a result, there is a concern that the electromagnetic force exerted on the oscillating arm may decrease, or the electric power consumed by the electromagnets may increase.

Further, unless the air gap between the oscillating arm and the core is uniform, there may be a case where a section in which a relatively large magnetic flux flows, and a section Ln which a relatively small magnetic flux flows may be produced within the oscillating arm as well. In this case, there is a possibility of magnetic saturation occurring in the section where a relatively large magnetic flux flows, giving rise to the same concern as that mentioned above.

SUMMARY OF THE INVENTION The present invention provides an electromagnetically driven valve with enhanced electromagnetic force and reduced power consumption.

A first aspect of the present invention relates to an electromagnetically driven valve. The electromagnetically driven valve includes: a disk that includes a support portion that is pivotably supported, and that pivots about the support portion so that a valve is reciprocated; and an electromagnet that includes a core arranged so as to be faced to the disk, and a coil wound around the core, and that exerts an electromagnetic force on the disk. In the electromagnetically driven valve, when current is supplied to the coil, a first magnetic circuit in which a magnetic flux that passes through the core and the disk and is relatively large flows, and a second magnetic circuit in which a magnetic flux that passes through the core and the disk and is relatively smaller than the magnetic flux flowing in the first magnetic circuit flows, are formed. The core has a core portion where the first magnetic circuit and the second magnetic circuit join, and in the core portion, a slit for separating the magnetic flux flowing in the first magnetic circuit and the magnetic flux flowing in the second magnetic circuit from each other is formed. According to the electromagnetically driven valve configured in this manner, by forming the slit in the core portion, the magnetic paths of the first magnetic circuit and second magnetic circuit are made independent from each other, thereby making it possible to optimize the magnetic flux density in each of the magnetic circuits. This makes it possible to enhance the electromagnetic force exerted on the disk, and reduce the amount of electric power consumed by the electromagnet.

In the above-described configuration, the first magnetic circuit may be located relatively farther away from the support portion than the second magnetic circuit. According to the electromagnetically driven valve configured in this manner, by forming the slit in the core portion, the magnetic flux density in the first magnetic circuit is prevented from decreasing due to the influence of the magnetic flux flowing in the second magnetic circuit. This allows a greater electromagnetic force to be exerted on the disk at a position where a large rotational moment is applied.

In the above-mentioned configuration, the core has a substantially E-shaped cross section as taken along a plane orthogonal to a rotation axis of the support portion, and the core includes a base portion, a first extending portion which extends from the base portion toward the disk and around λvhich the coil is wound, a second extending portion which is arranged on the support portion side with respect to the first extending portion, and which extends from the base portion toward the disk, and a third extending portion which is arranged on a side opposite to the second extending portion with respect to the first extending portion, and which extends from the base portion toward the disk. The first magnetic circuit is formed along an annular path including the disk, the third extending portion, the base portion, and the first extending portion. The second magnetic circuit is formed along an annular path including the disk, the second extending portion, the base portion, and the first extending portion. The core portion may be the first extending portion. According to the electromagnetically driven valve configured in this way, it is possible to achieve enhanced electromagnetic force and reduced power consumption with respect to an electromagnetically driven valve of a rotary drive type in which the core of an electromagnet has an "E"-shaped cross section.

In the above-mentioned configuration, an end of the second extending portion extended from the base portion is provided so as to be opposed to the support portion. When the disk is attracted to the electromagnet, a gap between the support portion and the end of the second extending portion may be larger than a gap between each of the first extending portion and the third extending portion and the disk. According to the electromagnetically driven valve configured in this way, due to the reason that the gap between the core and the disk is not uniform, the first magnetic circuit in which a relatively large magnetic flux flows, and the second magnetic circuit in which a relatively small magnetic flux flows are formed.

A second aspect of the present invention relates to an electromagnetically driven valve. The electromagnetically driven valve includes: a disk including a support portion that is pivotably supported, and that pivots about the support portion so that a valve is reciprocated; and an electromagnet that forms a magnetic flux in the disk to exert an electromagnetic force on the disk. In this electromagnetically driven valve, the disk includes a high magnetic flux section in which a relatively large magnetic flux flows, and a low magnetic flux section in which a relatively small magnetic flux flows, and the high magnetic flux section is formed of a high saturation magnetic flux density member having a higher saturation magnetic flux density than a magnetic material forming the low magnetic flux section.

According to the electromagnetically driven valve configured in this way, it is possible to prevent magnetic saturation from occurring in the high magnetic flux section where a relatively large magnetic flux flows, thereby achieving enhanced electromagnetic force and reduced power consumption. The high saturation magnetic flux density member is selectively used for the high magnetic flux section, and therefore, it is possible to keep an increase in material cost to the minimum.

In the above-mentioned configuration, the high magnetic flux section may be located relatively farther away from the support portion than the low magnetic flux section. According to the electromagnetically driven valve configured in this way, it is possible to prevent occurrence of magnetic saturation and exert a greater electromagnetic force on the disk at a position where a large rotational moment is applied.

In the above-mentioned configuration, the high magnetic flux section may have a first split body and a second split body that are separated by a first splitter, and the first splitter may be formed of a magnetic material having a lower saturation magnetic flux density than the high saturation magnetic flux density member. According to the electromagnetically driven valve configured in this way, it is possible to reduce eddy current loss occurring in the high magnetic flux section, and achieve reduced power consumption and improved magnetic responsiveness.

In the above-mentioned configuration, a magnetic path area in a section of the disk where the first split body and the second split body are arranged may be set smaller than a magnetic path area in a section of the disk where the splitter is arranged. According to the electromagnetically driven valve configured in this way, the first split body and the second split body that are formed of the high saturation magnetic flux density member prevent occurrence of magnetic saturation while making the magnetic path area small. This makes it possible to reduce the weight of the disk, thereby achieving a more effective reduction in power consumption.

In the above-mentioned configuration, the electromagnet may include a first electromagnet, and a second electromagnet that is arranged on a side opposite to the first electromagnetic with respect to the disk, the high magnetic flux section may have a third split body and a fourth split body that are separated by a second splitter, the third split body may be arranged so as to face the first electromagnet, and the fourth split body may be arranged so as to face the second electromagnet. According to the electromagnetically driven valve configured in this manner, the magnetic flux flowing between the first electromagnet and the disk, and the magnetic flux flowing between the second electromagnet and the disk are prevented from interfering with each other while the disk is alternately attracted to the first electromagnet and the second electromagnet. This improves the magnetic responsiveness of the electromagnetically driven valve. As described above, according to the present invention, it is possible to provide an electromagnetically driven valve which can achieve enhanced electromagnetic force and reduced power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a cross-sectional view showing an electromagnetically driven valve according to the first embodiment of the present invention;

FIG. 2 is a perspective view showing an electromagnet shown in FIG. 1 ; FIG, 3 is a perspective view showing a disk shown in FIG. 1 ;

FIG, 4 is a cross-sectional view showing how the electromagnetically driven valve shown in FIG. 1 is driven; FIG. 5 is a cross-sectional view showing an electromagnetically driven valve according to the second embodiment of the present invention;

FIG. 6 is a graph showing the B-H curves of magnetic materials forming the disk shown in FIG. 5;

FIG. 7 is a cross-sectional view showing a first modification of the electromagnetically driven valve shown in FIG. 5;

FIG. 8 is a perspective view of a disk shown in FIG. 7;

FIG 9 is a cross-sectional view showing a second modification of the electromagnetically driven valve shown in FIG. 5, illustrating a state with a disk attracted toward a valve-closing electromagnet; FIG. 10 is a cross-sectional view showing the second modification of the electromagnetically driven valve shown in FIG. 5, illustrating a state with a disk attracted toward a valve-opening electromagnet; and

FIG. 11 is a cross-sectional view showing a third modification of the electromagnetically driven valve shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In the drawings referenced below, the same reference numerals are used to denote the same or like members. FIG. 1 is a cross-sectional view showing an electromagnetically driven valve according to a first embodiment of the present invention. The electromagnetically driven valve according to this embodiment may be used as an intake valve or exhaust valve of an internal combustion engine such as a gasoline engine or diesel engine mounted in a vehicle. While this embodiment is directed to a case where the electromagnetically driven valve is used as an intake valve, the electromagnetically driven valve may have the same structure even when used as an exhaust valve.

As shown in FIG. 1, the electromagnetically driven valve 10 is a pivot-type electromagnetically driven valve of a rotary drive type that is driven by cooperation of electromagnet force and elastic force.

The electromagnetically driven valve 10 includes an intake valve 14, a disk 21 that pivots about a center axis 25, and a valve-closing electromagnet 51m and a valve-opening electromagnet 51n that each exert an electromagnetic force on the disk 21. The intake valve 14 includes a stem 11 extending in one direction, and a valve head 12 formed at the distal end of the stem 11. Following the pivoting motion of the disk 21, the intake valve 14 reciprocates in the direction in which the stem 11 extends (direction indicated by arrow 101).

The intake valve 14 is mounted in a cylinder head 18 in which an intake port 16 is formed. A valve seat 19 is provided at a position where the intake port 16 communicates with the combustion chamber 17. The intake port 16 opens and closes as the valve head 12 is brought into close contact with the valve seat 19 or released from the valve seat 19 in accordance with the reciprocating motion of the intake valve 14.

The electromagnetically driven valve 10 has valve guides 41 and 42 for guiding the stem 11 so as to be axially slidable. The valve guides 41 and 42 are formed of, for example, metal such as stainless steel to withstand the high-speed sliding motion of the stem 11. A lower spring 43, which serves as a first spring member, is supported on the outer circumference of the stem 11 by a flanged lower retainer 44. The lower spring 43 is formed of a coil spring. The lower spring 43 exerts an elastic force on the intake valve 14 in a direction for moving the stem 11 upwards (that is, in a direction for closing the intake valve 14). FIG. 2 is a perspective view showing the electromagnet shown in FIQ 1. As shown in

FIGs. 1 and 2, a support base 48 is fixed on the top surface of the cylinder head 18. The valve-closing electromagnet 5 Im and the valve-opening electromagnet 5 In are supported on the support base 48. The valve-closing electromagnet 51m and the valve-opening electromagnet 51n are respectively arranged above and below the disk 21.

The valve-closing electromagnet 51m and the valve-opening electromagnet 5 In have the same shape. The shape of the valve-opening electromagnet 5 In will be described as a representative example. The valve-opening electromagnet 51n includes a coil 53 and a core 52. The coil 53 is wound around the core 52. As shown in FIG. 1, the core 52 has a substantially E-shaped cross section as taken along a plane orthogonal to the center axis 25. The core 52 includes a base portion 52g, a first extending portion 52h, a second extending portion 52j, and a third extending portion 52k. The first extending portion 52h, the second extending portion 52j, and the third extending portion 52k are arranged apart from each other. The first extending portion 52h, the second extending portion 52j, and the third extending portion 52k extend toward the disk 21 from the base portion 52g. The second extending portion 52j is arranged on the side of a support portion 23 of the disk 21 with respect to the first extending portion 52h. The second extending portion 52j is located opposite the support portion 23. The third extending portion 52k is arranged on the side opposite to the second extending portion 52j with respect to the first extending portion 52h. The second extending portion 52j is arranged closest to the center axis 25, and the third extending portion 52k is arranged farthest from the center axis 25. The first extending portion 52h is arranged at a position farther from the center axis 25 than the second extending portion 52j and closer to the center axis 25 than the third extending portion 52k. As shown in FIG. 2, the coil 53 is wound around the first extending portion 52h. The coil 53 is wound so as to pass through the gap between the first extending portion 52h and the second extending portion 52j and the gap between the first extending portion 52h and the third extending portion 52k. The length of the core 52 along the axial direction of the center axis 25, that is, the depth of the core 52 is the same between the first extending portion 52h, the second extending portion 52j, and the third extending portion 52k.

The core 52 is formed of a magnetic material. In this embodiment, the core 52 is formed of a plurality of laminated electromagnetic steel sheets. The core 52 may be formed of a magnetic material other than an electromagnetic steel sheet, for example, a green compact of magnetic powder. The coil 53 of the valve-closing electromagnet 51m, and the coil 53 of the valve-opening electromagnet 51n may be formed of a single continuous coil wire or may be formed of separate coil wires.

FIG 3 is a perspective view showing the disk shown in FIG. 1. As shown in FIG. 1, the disk 21 is supported on the support base 48. The disk 21 is formed of a magnetic material. The disk 21 may be formed of a bulk material to ensure strength. The disk 21 has a small magnetic permeability in comparison to the core 52. The disk 21 includes the support portion 23 and a connecting portion 22. The center axis 25 is defined within the support portion 23. The disk 21 extends from the support portion 23 toward the connecting portion 22 in a direction crossing the stem 11. As shown in FIG. 3, a through-hole 24 is formed in the support portion 23. The support portion 23 has a cylindrical shape. The support portion 23 includes a circumferential surface that extends along the center axis 25. A torsion bar 31, which serves as a second spring member, is press-fitted in the through-hole 24. The torsion bar 31 extends in the axial direction of the center axis 25. The support portion 23 is pivotably supported on the support base 48 via the torsion bar 31. A distal end l ie of the stem 11 on the side opposite to the distal end at which the valve head 12 is formed is connected to the connecting portion 22.

The torsion bar 31 exerts an elastic force on the disk 21 in a direction that pivots the disk 21 counterclockwise about the center axis 25. That is, the torsion bar 31 exerts an elastic force on the intake valve 14 to lower the stem 11 (that is, in a direction for opening the intake valve 14) via the disk 21. When no electromagnetic force exerted on the disk 21 , the disk 21 is positioned in an intermediate position between the valve-open position and the valve-closed position due to the elastic forces of the lower spring 43 and torsion bar 31.

When current is supplied to the coil 53 of the valve-closing electromagnet 51m, a magnetic flux passing through the core 52 of the valve-closing electromagnet 51m and the disk 21 is formed. The valve-closing electromagnet 51m thus generates an electromagnetic force that attracts the disk 21. When current is supplied to the coil 53 of the valve-opening electromagnet 5 In, a magnetic flux passing through the core 52 of the valve-opening electromagnet 5 In and the disk 21 is formed. The valve-opening electromagnet 5 In thus generates an electromagnetic force that attracts the disk 21.

When the disk 21 is attracted toward the valve-closing electromagnet 51m and the valve-opening electromagnet 5 In₅ a relatively small gap is formed between each of the first extending portion 52h and third extending portion 52k and the disk 21, and a relatively large gap is formed between the second extending portion 52j and the disk 21. In this embodiment, each of the first extending portion 52h and third extending portion 52k and the disk 21 are brought into close contact with each other, and a gap is formed between the second extending portion 52j and the support portion 23.

While the end face of the second extending portion 52j opposite the support portion 23 has a planar shape in FIG. 2, the shape of the end face is not limited to this. For example, the end face may have a curved surface that conforms to the circumferential surface of the support portion 23 and extends along the center axis 25.

Due to the electromagnetic forces generated by the valve-closing electromagnet 51m and the valve-opening electromagnet 5 In, and the elastic forces of the lower spring 43 and torsion bar 31, the disk 21 is alternately attracted toward the valve-closing electromagnet 51m and the valve-opening electromagnet 5 In, and pivots about the center axis 25. As the disk 21 is attracted toward the valve-closing electromagnet 51m, the stem 11 ascends, so the intake valve 14 is positioned in a valve-closed position. As the disk 21 is attracted toward the valve-opening electromagnet 5 In, the stem 11 descends, so that the intake valve 14 is positioned in a valve-open position. FIG. 4 is a cross-sectional view showing how the electromagnetically driven valve shown in FIG. 1 is driven. While the following description will be directed to a case where the disk 21 is attracted toward the valve-closing electromagnet 51m, the same applies to a case where the disk 21 is attracted toward the valve-opening electromagnet 5 In.

As shown in FIG. 4, when the disk 21 is attracted toward the valve-closing electromagnet 51m, current is supplied to the coil 53 of the valve-closing electromagnet 51m, so a magnetic circuit 61 in which a relatively large magnetic flux flows, and a magnetic circuit 62 in which a relatively small magnetic flux flows are formed in the core 52 and the disk 21.

In the magnetic circuit 61, a magnetic flux passes around the coil 53 while flowing through an annular path formed by the base portion 52g, the first extending portion 52h, the disk 21, and the third extending portion 52k. In the magnetic circuit 62, a magnetic flux passes around the coil 53 while flowing through an annular path formed by the base portion 52g, the first extending portion 52h, the disk 21, and the second extending portion 52j. In the magnetic circuit 62, the magnetic flux passes through the support portion 23. The magnetic circuit 61 and the magnetic circuit 62 join at the First extending portion 52h.

The magnetic circuit 61 is formed at a position relatively far from the support portion 23, and the magnetic circuit 62 is formed at a position relatively close to the support portion 23. Because a relatively small gap is formed between each of the first extending portion 52h and third extending portion 52k and the disk 21, and a relatively large gap is formed between the second extending portion 52j and the disk 2I₃ the magnetic flux flowing in the magnetic circuit 61 becomes larger than the magnetic flux flowing in the magnetic circuit 62.

As shown in FIGs. 3 and 4, the disk 21 includes a first section 26, and second sections 27 and 28 on the path along which the magnetic circuit 61 is formed. The first section 26 located opposite the coil 53. The second section 27 and the second section 28 are located opposite the first extending portion 52h and the third extending portion 52k, respectively. As shown in FIG. 3, the thickness of the disk 21 is set such that the magnetic path area Sl at the first section 26 is larger than the magnetic path areas S2 and S3 at the second sections 27 and 28. That is, the thickness Tl of the disk 21 at the first section 26 is greater than the thicknesses T2 and T3 of the disk 21 at the second sections 27 and 28. Assuming that the thickness of the disk 21 is constant, the magnetic flux density in each of the second sections 27 and 28 is lower than the magnetic flux density in the first section 26, In this embodiment, the thickness Tl of the disk 21 is greater at the first section 26 where the magnetic flux density is high, and the thicknesses T2 and T3 of the disk 21 smaller at the second sections 27 and 28 where the magnetic flux density is low. The weight of the disk 21 may be thus reduced without causing magnetic saturation within the disk 21. The reduced weight of the disk 21 makes it possible to improve the quietness of the electromagnetically driven valve 10. In addition, it is possible to reduce power consumption and transition time as well as improve durability. It should be noted that the disk 21 provided to the electromagnetically driven valve 10 may have a constant thickness. As shown in FIGs. 2 and 4, a slit 58 is formed in the core 52. The slit 58 is formed so as to separate the magnetic flux flowing in the magnetic circuit 61 and the magnetic flux flowing in the magnetic circuit 62 from each other. An air space is formed in the slit 58. Alternatively, a resin or a non-magnetic member may be provided in the slit 58.

As shown in FIG. 4, the slit 58 is formed in the first extending portion 52h where the magnetic circuit 61 and the magnetic circuit 62 join. As shown in FIG. 2, the slit 58 is formed over the entire width in the depth direction of the core 52. The slit 58 divides the first extending portion 52h into a support-portion-side portion 66 and a connecting-portion-side portion 67. The magnetic circuit 61 is formed on a path that includes the connecting-portion-side portion 67. The magnetic circuit 62 is formed on a path including the support-portion-side portion 66.

If the slit 58 is not formed in the core 52, the magnetic flux flowing in the magnetic circuit 61 and the magnetic flux flowing in the magnetic circuit 62 are equalized in the first extending portion 52h. Because the magnetic flux flowing in the magnetic circuit 62 is smaller than the magnetic flux flowing in the magnetic circuit 61, as the two magnetic fluxes are equalized, the magnetic flux density on the path of the magnetic circuit 61 decreases.

In contrast, according to this embodiment, the magnetic path of the magnetic circuit 61 is made independent from the magnetic path of the magnetic circuit 62 by forming the slit 58 in the core 52. The magnetic flux density inside the first extending portion 52h thus remains high on the path of the magnetic circuit 61. As a result, a greater electromagnetic force is exerted on the disk 21 at a position where a large rotational moment is applied.

The slit 58 is formed such that the magnetic path area in the connecting-portion-side portion 67 becomes as small as possible within a range that will not cause magnetic saturation of the magnetic flux flowing in the magnetic circuit 61. The electromagnetic force F exerted on the disk 21 is proportional to the value of ((magnetic flux density B)² x magnetic path area S). That is, to increase the electromagnetic force F, it is more effective to increase the magnetic flux density B than to increase the magnetic path area S. For this reason, by forming the slit 5 S as described above, a greater electromagnetic force may be exerted on the disk 21 at a position where a large rotational moment is applied.

The electromagnetically driven valve 10 according to the first embodiment of the present invention includes the disk 21 , and the valve-closing electromagnet 51m and the valve-opening electromagnet 5 In. The disk 21 includes the support portion 23 pivotably supported, and causes the intake valve 14 to reciprocate as the disk 21 pivots on the support portion 23. The valve-closing electromagnet 51m and the valve-opening electromagnet 51n each include the core 52 located opposite the disk 21, and the coil 53 wound around the core

52, and exert an electromagnetic force on the disk 21. When current is supplied to the coil

53, the magnetic circuit 61 as a first magnetic circuit in which a magnetic flux that passes through the core 52 and the disk 21 and is relatively large flows, and the magnetic circuit 62 as a second magnetic circuit in which a magnetic flux that passes through the core 52 and the disk 21 and is relatively small flows, are formed. The core 52 has the first extending portion 52h as a core portion where the magnetic circuit 61 and the magnetic circuit 62 join. In the first extending portion 52h, the slit 58 that separates the magnetic flux flowing in the magnetic circuit 61 from the magnetic flux flowing in the magnetic circuit 62 is formed.

With the electromagnetically driven valve 10- according to the first embodiment of the present invention configured as described, it is possible to reduce power consumption while increasing an electromagnetic force exerted on the disk 21.

FIG. 5 is a cross-sectional view showing an electromagnetically driven valve according to a second embodiment of the present invention. FIG. 5 is a view corresponding to FIG. 4 according to the first embodiment. In this embodiment, description will not be repeated for structures that overlap with those of the electromagnetically driven valve 10 according to the first embodiment.

As shown in FIG 5, a disk 121 of the electromagnetically driven valve according to this embodiment includes a high magnetic flux section 71 and a low magnetic flux section 72. A relatively large magnetic flux flows in the high magnetic flux section 71, and a relatively small magnetic flux flows in the low magnetic flux section 72. The magnetic circuit 61 and the magnetic circuit 62 are respectively formed in the high magnetic flux section 71 and the low magnetic flux section 72. The low magnetic flux section 72 is located opposite the first extending portion 52h and the third extending portion 52k. The low magnetic flux section 72 is located opposite the first extending portion 52h and the second extending portion 52j. The high magnetic flux section 71 is arranged relatively far from the center axis 25, and the low magnetic flux section 72 is arranged relatively close to the center axis 25. FIG. 6 is a graph indicating the B-H curves of materials used to form the disk 121 shown in FIG. 5. In FIG. 6, a curve 201 indicates the B-H curve of a magnetic material forming the high magnetic flux section 71 , and a curve 202 indicates the B-H curve of a magnetic material forming the low magnetic flux section 72. The high magnetic flux section 71 is formed of a high saturation magnetic flux density member having a saturation magnetic flux density B 1. The low magnetic flux section 72 is formed of a magnetic member having a saturation magnetic flux density B2. The saturation magnetic flux density Bl is higher than the saturation magnetic flux density B2. As an example, Bl is 2.2 T, and B2 is 1.6 to 1.8 T.

By forming the high magnetic flux section 71 , in which a relatively large magnetic flux flows, using a high saturation magnetic flux density member, magnetic saturation in the high magnetic flux section 71 is prevented. However, a high saturation magnetic flux density member is extremely expensive. In this embodiment, a high saturation magnetic flux density member is selectively used for the high magnetic flux section 71 in the disk 21, thereby keeping an increase in material cost to the minimum.

The electromagnetically driven valve according to the second embodiment of the present invention includes the disk 121, and the valve-closing electromagnet 51m and the valve-opening electromagnet 5 In. The disk 121 includes the support portion 23 that is pivotably supported in place, and causes the intake valve 14 reciprocate as the disk 21 pivots about the support portion 23. The valve-closing electromagnet 51m and the valve-opening- electromagnet 5 In each form a magnetic flux in the disk 121 to exert an electromagnetic force. The disk 121 includes the high magnetic flux section 71 in which a relatively large magnetic flux flows, and the low magnetic flat section 72 in which a relatively small magnetic flux flows. The high magnetic flux section 71 is formed of a high saturation magnetic flux density member having a higher saturation magnetic flux density than the magnetic material forming the high magnetic flux section 71.

With the electromagnetically driven valve according to the second embodiment of the present invention configured as described above, the same effect as that described with reference to the first embodiment may be attained.

While the slit 58 is formed in the core 52 shown in FIG. 5, the slit 58 may be omitted. The disk 121 may also have a constant thickness.

FIG. 7 is a cross-sectional view showing a first modification of the electromagnetically driven valve shown in FIG. 5. FIG. 8 is a perspective view of the disk shown in FIG. 7. As shown in FIGs. 7 and 8, in this modification, the high magnetic flux section 71 includes a split body 76 and a split body 77 separated by a splitter 75. The split body 76 and the split body 77 are separated by the splitter 75 on the path of the magnetic circuit 61. That is, as shown in FIG. 7, the high magnetic flux section 71 is separated in the thickness direction of the disk 121 into the split body 76 and the split body 77 by the splitter 75.

The split bodies 76 and 77 are formed of a high saturation magnetic flux density member. The splitter 75 is formed of a magnetic member 78 that has a lower saturation magnetic flux density than the high saturation magnetic flux density member used to form the split bodies 76 and 77. The magnetic member 78 may be formed of the same material as the magnetic material forming the low magnetic flux density section 72 or may be formed of a different material. The split bodies 76 and 77, and the magnetic member 78 and the low magnetic flux density section 72 may be bonded together by welding, for example. When a change in magnetic field occurs inside the disk 121, an eddy current 79 flowing in a direction that impedes the change is induced. While a high magnetic flux density member has excellent magnetic properties, it suffers from a large loss due to such eddy currents. In contrast, according to this embodiment, induction of eddy current may be suppressed by arranging in the high magnetic flux section 71 the magnetic member 78 having a lower saturation magnetic flux density. Further, the flow of the eddy current 79 may be positively cut off by forming the splitter 75 to separate the split body 76 from the split body 77, both of which are formed of a high saturation magnetic flux density. As a result, loss due to eddy currents is reduced, thereby reducing power consumption and improving magnetic responsiveness.

Further, as shown in FIG. 8, the split bodies 76 and 77 are arranged in the second section 28 and the second section 27, respectively. The magnetic member 78 is arranged in the first section 26. That is, the disk 121 includes the split bodies 76 and 77 that are formed of a high saturation magnetic flux density member and respectively have the relatively small disk thicknesses T3 and T2, and the magnetic member 78 that is formed of a material having a lower saturation magnetic flux density than the split bodies 76 and 77 and has the relatively large disk thickness Tl . It is thus possible to reduce the weight of the disk 121 while suppressing the occurrence of magnetic saturation within the disk 121.

FIGs. 9 and 10 are cross-sectional views showing a second modification of the electromagnetically driven valve shown in FIG. 5. FIG. 9 shows the disk 121 attracted toward the valve-closing electromagnet 51m, and FIG. 10 shows the disk 121 attracted toward the valve-opening electromagnet 5 In.

As shown in FIGs. 9 and 10, the high magnetic flux section 71 includes a split body 81 and a split body 82 separated by a splitter 80. The split body 81 is arranged so as to face the valve-closing electromagnet 51m. The split body 82 is arranged so as to face the valve-opening electromagnet 51 n. The splitter 80 is formed of a magnetic member 83 that has a lower saturation magnetic flux density than the high saturation magnetic flux density member used to form the split bodies 81 and 82. The magnetic member 83 is provided integrally with the low magnetic flux section 72. That is, the magnetic material forming the magnetic member 83 is the same as the magnetic material forming the low magnetic flux section 72. The split bodies 81 and 82 may be bonded to the low magnetic flux section 72 and the magnetic member 83 by such means as shrink fitting, welding, or caulking.

The disk 121 reciprocates between a valve-open position and a valve-closed position in a short time on the order of several milliseconds. Therefore, when the disk 121 is attracted toward the valve-closing electromagnet 51m, for example, the magnetic flux that attracts the disk 121 toward the valve-opening electromagnet 5 In remains as a residual magnetic flux. As a result, the build-up of a magnetic flux flow formed in the disk 121 is impeded by the residual magnetic flux. A residual magnetic flux tends to increase, particularly when a high saturation magnetic flux density member is used.

In contrast, according to this embodiment, the splitter 80 is formed to separate the split body 81 from the split body 82. The splitter 80 is formed of the magnetic member 83 having a lower saturation magnetic flux density than the split bodies 81 and 82. It is thus possible to suppress interference between the magnetic flux formed in the split body 81 when attracting the disk 121 toward the valve-closing electromagnet 51m, and the magnetic flux formed in the split body 82 when attracting the disk 121 toward the valve-opening electromagnet 5 In. This improves the magnetic responsiveness.

The splitter 80 may be formed of a non-magnetic member such as resin instead of the magnetic member 83. In this case, magnetic flux interference between the split body 81 and the split body 82 is prevented more effectively. On the other hand, if the splitter 80 is formed of the magnetic member 83, it is possible to magnetic saturation within the disk 121 while keeping the thickness of the disk 121 small.

FIG. 11 is a cross-sectional view showing a third modification of the electromagnetically driven valve shown in FIG. 5. As shown in FIG. 11 , according to this modification, the high magnetic flux section 71 includes split bodies 91, 92, 93, and 94. The split bodies 91 and 94, and the split bodies 92 and 93 are separated by the splitter 75. The splitter 75 is formed of the magnetic member 78. The split bodies 91 and 92, and the split bodies 93 and 94 are separated by the splitter 80. The splitter 80 is formed of the magnetic member 83. The disk 121 according to this modification combines the features of the disk 121 according to the first modification shown in FIG 7, and the features of the disk 121 according to the second modification shown in FIGs. 9 and 10. Due to this configuration, both the effect of the first modification and the effect of the second modification may be attained.

It is to be understood that the example embodiments described herein are not limitative. It is intended that the scope of the invention is defined not by the above description but by the claims and covers all modifications equivalent to and within the scope of the claims.

Claims

CLAIMS:

1. An electromagnetically driven valve characterized by comprising: a disk that includes a support portion that is pivotably supported, and that pivots about the support portion so that a valve is reciprocated; and an electromagnet that includes a core arranged so as to be faced to the disk, and a coil wound around the core, and that exerts an electromagnetic force on the disk, wherein: when current is supplied to the coil, a first magnetic circuit in which a magnetic flux that passes through the core and the disk flows, and a second magnetic circuit in which a magnetic flux that passes through the core and the disk and is smaller than the magnetic flux flowing in the first magnetic circuit flows, are formed; the first magnetic circuit and the second magnetic circuit join at a central portion of the core; and a slit is formed in the central portion to separate the magnetic flux flowing in the first magnetic circuit from the magnetic flux flowing in the second magnetic circuit.

2. The electromagnetically driven valve according to claim 1, wherein the first magnetic circuit is located further away from the support portion than the second magnetic circuit.

3. The electromagnetically driven valve according to claim 1 or 2, wherein: the core includes a base portion; a first extending portion which extends from the base portion toward the disk, around which the coil is wound; a second extending portion, which is arranged on the support portion side with respect to the first extending portion and extends from the base portion toward the disk; and a third extending portion which is arranged on a side opposite to the second extending portion with respect to the first extending portion, and extends toward the disk from the base portion; the first magnetic circuit is formed along an annular path that includes the disk, the third extending portion, the base portion, and the first extending portion; the second magnetic circuit is formed along an annular path that includes the disk, the second extending portion, the base portion, and the first extending portion; and the central portion is the first extending portion.

4. The electromagnetically driven valve according to claim 3, wherein an end of the second extending portion extended from the base portion is provided to face the support portion and, when the disk is attracted to the electromagnet, a gap between the support portion and the end of the second extending portion is larger than the gap between each of the first extending portion and the third extending portion and the disk.

5. An electromagnetically driven valve characterized by comprising: a disk that includes a support portion that is pivotably supported, and that pivots about the support portion so that a valve is reciprocated; and an electromagnet that forms a magnetic flux in the disk to exert an electromagnetic force on the disk, wherein: the disk includes a high magnetic flux section, and a low magnetic flux section in which smaller magnetic flux than a magnetic flux, which flows in the high magnetic flux section, flows, and the high magnetic flux section is formed of a high saturation magnetic flux density member that has a higher saturation magnetic flux density than the magnetic material that forms the low magnetic flux section.

6. The electromagnetically driven valve according to claim 5, wherein the high magnetic flux section is located further away from the support portion than the low magnetic flux section.

7. The electromagnetically driven valve according to claim 5 or 6, wherein the high magnetic flux section has a first split body and a second split body that are separated in a thickness direction of the disk by a first splitter, and the first splitter is formed of a magnetic material having a lower saturation magnetic flux density than the high saturation magnetic flux density member.

8. The electromagnetically driven valve according to claim 7, wherein a magnetic path area in a section of the disk where the first split body and the second split body are arranged is smaller than the magnetic path area in a section of the disk where the splitter is arranged.

9. The electromagnetically driven valve according to claim 5 or 6, wherein: the electromagnet includes a first electromagnet, and a second electromagnet that is arranged on a side of the disk opposite from the first electromagnet; and the high magnetic flux section has a third split body and a fourth split body that are separated by a second splitter, the third split body faces the first electromagnet, and the fourth split body faces the second electromagnet.

10. The electromagnetically driven valve according to claim 3, wherein a thickness of the section of the disk located to face the first extending portion and the section of the disk located to face the third extending portion is smaller than the thickness of the section of the disk located to face the portion of core located between the first extending portion and the third extending portion.

11. The electromagnetically driven valve according to claim 5 or 6, wherein: the high magnetic flux section has a first split body, a second split body, a third split body, and a fourth split body that are separated by a first splitter and a second splitter; the first splitter is formed of a magnetic material having a lower saturation magnetic flux density than the high saturation magnetic flux density member; the first split body and the second split body are respectively separated from the third split body and the forth split body in the thickness direction of the disk by the first splitter; the electromagnet includes a first electromagnet, and a second electromagnet that is arranged on a side of the disk opposite from the first electromagnet; and the first split body and the second split body are separated by the second splitter, and the third split body and the fourth split body are separated by the second splitter so that the first and the third split body face the first electromagnet, and the second split body and the fourth split body face the second electromagnet.