US20070252099A1

US20070252099A1 - Electromagnetically Driven Valve

Info

Publication number: US20070252099A1
Application number: US11/632,660
Authority: US
Inventors: Yutaka Sugie; Masahiko Asano
Original assignee: Individual
Current assignee: Toyota Motor Corp
Priority date: 2004-09-01
Filing date: 2005-06-20
Publication date: 2007-11-01
Also published as: EP1784559B1; WO2006025146A1; JP2006070968A; CN101010494A; EP1784559A1; DE602005004927T2; DE602005004927D1

Abstract

An electromagnetically driven valve includes a driven valve having a stem extending in a prescribed direction and an umbrella-shaped portion provided at a tip end of the stem and opening/closing an intake/exhaust port, a lower disc and an upper disc having one ends coupled to the stem and the other ends supported by a disc support base so as to allow free oscillation of the disc respectively and oscillating around the other ends so as to cause the driven valve to carry out reciprocating motion in the prescribed direction, a lash adjuster provided in the stem, and a guide ring guiding the lash adjuster along the prescribed direction. The lash adjuster contracts and expands in the prescribed direction and accommodates displacement of the stem produced in a direction orthogonal to the prescribed direction as a result of reciprocating motion of the driven valve. With such a structure, the driven valve carries out smooth reciprocating motion.

Description

TECHNICAL FIELD

The present invention generally relates to an electromagnetically driven valve, and more particularly to an electromagnetically driven valve of a rotary drive type used in an internal combustion engine and driven by electromagnetic force and elastic force.

BACKGROUND ART

With regard to a conventional electromagnetically driven valve, for example, Japanese Patent Laying-Open No. 11-30113 discloses an electromagnetically driven apparatus aiming at prevention of generation of sound caused by friction or impact at the time of opening/closing of an intake/exhaust valve as well as attaining improvement in its characteristic of being mounted on an engine. The electromagnetically driven apparatus disclosed in this publication includes an armature accommodated in a casing in a vertically movable manner, a valve-closing electromagnet and a valve-opening electromagnet fixed to positions above and below the armature respectively, and a valve-opening side spring moving an intake valve toward a valve-opening direction through the armature.
The electromagnetically driven apparatus structured as above is called a parallel drive type, in which electromagnetic force generated by the valve-closing electromagnet and the valve-opening electromagnet and elastic force by the valve-opening side spring directly act on a main shaft integrally formed with the armature, thereby causing the main shaft to carry out reciprocating motion.
Moreover, Japanese Patent Laying-Open No. 11-107723 discloses an electromagnetically driven valve aiming to realize excellent silence and power-saving capability. The electromagnetically driven valve disclosed in this publication is also of a parallel drive type, similar to the electromagnetically driven apparatus disclosed in Japanese Patent Laying-Open No. 11-30113 mentioned above.
In addition to the parallel drive type, there is an electromagnetically driven valve of a rotary drive type. The electromagnetically driven valve of this type includes a driven valve having a stem and carrying out reciprocating motion between a valve-opening position and a valve-closing position, a disc having one end in abutment to an end of the stem and the other end supported by a disc support base in a hinged manner, and an electromagnet applying electromagnetic force to the disc. The electromagnetically driven valve further includes a torsion bar provided at the other end of the disc and moving the driven valve toward the valve-opening position and a helical spring arranged around an outer circumference of the stem and moving the driven valve toward the valve-closing position. Elastic force of the spring and electromagnetic force generated as a result of current supply to the electromagnet cause the disc to oscillate around the other end. The movement of the disc is transmitted to the stem through one end, whereby the driven valve carries out reciprocating motion.
In the electromagnetically driven valve of a rotary drive type, oscillation (pivot) movement of the disc is converted to linear movement, which is in turn transmitted to the driven valve. If the disc oscillates around the other end, however, one end of the disc is displaced also in a direction orthogonal to the direction of reciprocating motion of the driven valve. Such displacement causes failure in smooth reciprocating motion of the driven valve or increase in slide resistance between the stem and a guide for guiding the stem.

DISCLOSURE OF THE INVENTION

In order to solve the above-described problems, an object of the present invention is to provide an electromagnetically driven valve attaining smooth reciprocating motion of the driven valve.
An electromagnetically driven valve according to the present invention includes: a driven valve having a valve shaft extending in a prescribed direction and a valve element provided at a tip end of the valve shaft and opening/closing an intake/exhaust port; an oscillating member having one end coupled to the valve shaft and the other end supported by a supporting member so as to allow free oscillation of the oscillating member and oscillating around the other end so as to cause the driven valve to carry out reciprocating motion in the prescribed direction; a buffer member provided in the valve shaft between the tip end where the valve element is provided and a position where one end is coupled; and a guide member guiding the buffer member along the prescribed direction. The buffer member contracts and expands in the prescribed direction and accommodates displacement of the valve shaft produced in a direction orthogonal to the prescribed direction as a result of reciprocating motion of the driven valve.
According to the electromagnetically driven valve structured as above, the buffer member is guided by the guide member along the prescribed direction. Accordingly, while movement of the buffer member in the direction orthogonal to the prescribed direction is restricted, displacement of the valve shaft produced in the orthogonal direction can be accommodated. At the same time, the buffer member contracts and expands in the prescribed direction, so that registration error of the valve element caused by a difference from the valve shaft in thermal expansion or part assembly error can be accommodated. Therefore, according to the present invention, smooth reciprocating motion of the driven valve can be achieved while sufficient sealing of the intake/exhaust port by means of the valve element is ensured.
Preferably, the valve shaft has a first shaft portion located on a side where one end is coupled with respect to the buffer member and a second shaft portion located on a side of the valve element with respect to the buffer member. The first shaft portion includes a first end surface abutting on a surface of the buffer member. The first end surface makes sliding movement with respect to the surface of the buffer member, so that displacement of the valve shaft produced in the direction orthogonal to the prescribed direction is accommodated. According to the electromagnetically driven valve structured as above, displacement of the valve shaft produced in the direction orthogonal to the prescribed direction can be accommodated by using a simplified structure.
Preferably, the second shaft portion includes a second end surface connected to a surface of the buffer member, and the first shaft portion is formed such that the first end surface has an area larger than that of the second end surface. According to the electromagnetically driven valve structured as above, a contact area between the first end surface and the surface of the buffer member is increased, so that slide resistance produced therebetween can be made smaller. Therefore, displacement of the valve shaft produced in the direction orthogonal to the prescribed direction can smoothly be accommodated, while suppressing abrasion of the surface of the buffer member.
As described above, according to the present invention, an electromagnetically driven valve attaining smooth reciprocating motion of the driven valve can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing an electromagnetically driven valve according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing an electromagnet in FIG. 1.
FIG. 3 is a perspective view showing a lower disc (an upper disc) in FIG. 1.
FIG. 4 is a schematic diagram showing the upper disc and the lower disc at an oscillation end on a valve-opening side.
FIG. 5 is a schematic diagram showing the upper disc and the lower disc at an intermediate position.
FIG. 6 is a schematic diagram showing the upper disc and the lower disc at an oscillation end on a valve-closing side.
FIG. 7 is a schematic diagram showing movement of the electromagnetically driven valve in FIG. 1.
FIG. 8 is a cross-sectional view of the electromagnetically driven valve along the line VIII-VIII in FIG. 7.
FIG. 9 is a cross-sectional view showing an electromagnetically driven valve according to a second embodiment of the present invention.
FIG. 10 is a cross-sectional view showing an electromagnetically driven valve according to a third embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members have the same reference characters allotted.
(First Embodiment)
The electromagnetically driven valve according to the present embodiment implements an engine valve (an intake valve or an exhaust valve) in an internal combustion engine such as a gasoline engine or a diesel engine. In the present embodiment, description will be given assuming that the electromagnetically driven valve implements an intake valve, however, it is noted that the electromagnetically driven valve is similarly structured also when it implements an exhaust valve.
Referring to FIG. 1, an electromagnetically driven valve 10 is a rotary drive type electromagnetically driven valve. As an operation mechanism for the electromagnetically driven valve, a parallel link mechanism is applied.
Electromagnetically driven valve 10 includes a driven valve 14 having a stem 12 extending in one direction and an umbrella-shaped portion 13 formed at a tip end of stem 12, and a lower disc 20 and an upper disc 30 coupled to different positions on stem 12 and oscillating by receiving electromagnetic force and elastic force applied thereto. Stem 12 is constituted of an upper stem 18 coupled to lower disc 20 and upper disc 30 and a lower stem 19 continuing from umbrella-shaped portion 13.
Electromagnetically driven valve 10 further includes a lash adjuster 16 disposed between upper stem 18 and lower stem 19, and a guide ring 45 disposed on an outer circumference of lash adjuster 16 and guiding lash adjuster 16 along the direction in which stem 12 extends. Driven valve 14 carries out reciprocating motion in the direction in which stem 12 extends (a direction shown with an arrow 103), upon receiving the oscillating movement of lower disc 20 and upper disc 30.
Driven valve 14 is mounted on a cylinder head 41 having an intake port 17 formed. A valve seat 42 is provided in a position where intake port 17 of cylinder head 41 communicates to a not-shown combustion chamber. The reciprocating motion of driven valve 14 causes umbrella-shaped portion 13 to intimately contact with valve seat 42 or to move away from valve seat 42, so as to open or close intake port 17. In other words, when stem 12 is elevated, driven valve 14 is positioned at a valve-closing position. On the other hand, when stem 12 is lowered, driven valve 14 is positioned at a valve-opening position.
In cylinder head 41, a valve guide 43 for slidably guiding lower stem 19 in an axial direction is provided. Valve guide 43 is formed from a metal material such as stainless steel, in order to endure high-speed slide movement with respect to lower stem 19. A collar-shaped lower retainer 8 is fixed to an outer circumferential surface of lower stem 19, at a position apart from valve guide 43. A hollow portion 9 opening toward a top surface side is formed in cylinder head 41. Hollow portion 9 houses a lower spring 11 between a bottom surface of hollow portion 9 and lower retainer 8. Lower spring 11 applies the elastic force to driven valve 14 in such a direction that lower retainer 8 moves away from the bottom surface of hollow portion 9, that is, in a direction elevating lower stem 19.
Lash adjuster 16 is constituted of an upper lid and a lower lid arranged with a prescribed gap therebetween and a viscous member filling the gap between the upper lid and the lower lid, such as grease or oil. With such a structure, lash adjuster 16 can freely expand and contract in the direction in which stem 12 extends. Lash adjuster 16 is shaped like a column, and includes a top surface 16a and a bottom surface 16 b facing upper stem 18 and lower stem 19 respectively and a slide surface 16 c extending between top surface 16 a and bottom surface 16 b.
A tip end of lower stem 19 opposite to the tip end where umbrella-shaped portion 13 is formed is connected to bottom surface 16 b of lash adjuster 16. That is, umbrella-shaped portion 13 and lash adjuster 16 are provided at opposing ends of lower stem 19, and lower retainer 8 is fixed at a position therebetween. Upper stem 18 has an end surface 18 a facing top surface 16 a. Upper stem 18 is provided, with respect to lash adjuster 16, in such a manner that end surface 18 a abuts on top surface 16 a. Slide surface 16 c of lash adjuster 16 extends, with a distance from the outer circumferential surface of upper stem 18 and lower stem 19 in a radial direction. That is, lash adjuster 16 has a diameter larger than that of upper stem 18 and lower stem 19.
Guide ring 45 has an annular shape, and has a guide surface 45 c extending along an inner circumference. Guide surface 45 c and slide surface 16 c of lash adjuster 16 face and slidably contact with each other. In upper stem 18, a coupling pin 12 p protruding from the outer circumferential surface and a coupling pin 12 q protruding from the outer circumferential surface at a position apart from coupling pin 12 p are formed.
On the top surface of cylinder head 41, disc support base 51 supporting lower disc 20 and upper disc 30 so as to allow free oscillation thereof is provided. An electromagnet 60 for applying electromagnetic force to lower disc 20 and upper disc 30 is attached to disc support base 51.
Referring to FIGS. 1 and 2, electromagnet 60 is provided in disc support base 51 at a position between lower disc 20 and upper disc 30. Electromagnet 60 is constituted of a valve-opening/closing coil 62 and a valve-opening/closing core 61 formed from a magnetic material and having attraction and contact surfaces 61 a and 61 b. Valve-opening/closing core 61 has a shaft portion 61 p extending in a direction orthogonal to the direction in which stem 12 extends. Valve-opening/closing coil 62 is provided in a manner wound around shaft portion 61 p, and implemented by a monocoil (a coil implemented by a continuous wire). It is noted that valve-opening/closing coil 62 may be implemented by winding a plurality of coils, without limited to the monocoil.
Disc support base 51 further includes a valve-opening permanent magnet 55 and a valve-closing permanent magnet 56 located on a side opposite to valve-opening permanent magnet 55 with electromagnet 60 being interposed. Valve-opening permanent magnet 55 has an attraction and contact surface 55 a, and a space in which lower disc 20 oscillates is defined between attraction and contact surface 55 a and attraction and contact surface 61 b of electromagnet 60. In addition, valve-closing permanent magnet 56 has an attraction and contact surface 56 a, and a space in which upper disc 30 oscillates is defined between attraction and contact surface 56 a and attraction and contact surface 61 a of electromagnet 60.
Referring to FIGS. 1 and 3, lower disc 20 has one end 22 and the other end 23, and extends from the other end 23 to one end 22 in a direction intersecting stem 12. Lower disc 20 is constituted of an arm portion 21 having rectangular surfaces 21 a and 21 b formed and extending between one end 22 and the other end 23, and a shaft-receiving portion 28 having a hollow cylindrical shape and provided at the other end 23. Surfaces 21 a and 21 b face attraction and contact surface 61 b of electromagnet 60 and attraction and contact surface 55 a of valve-opening permanent magnet 55, respectively.
Arm portion 21 has a notch 29 formed on the side of one end 22, and annular holes 24 are formed in opposing wall surfaces of notch 29. A central axis 25 extending in a direction orthogonal to a direction from one end 22 to the other end 23 is defined in the other end 23. Shaft receiving portion 28 has a through hole 27 formed, which extends along central axis 25.
Upper disc 30 is shaped similarly to lower disc 20, and one end 32, the other end 33, an arm portion 31, a surface 31 b, a surface 31 a, a notch 39, a hole 34, a shaft receiving portion 38, a through hole 37, and a central axis 35 corresponding to one end 22, the other end 23, arm portion 21, surface 21 a, surface 21 b, notch 29, hole 24, shaft receiving portion 28, through hole 27, and central axis 25 of lower disc 20 respectively are formed. Surfaces 31 a and 31 b face attraction and contact surface 61 a of electromagnet 60 and attraction and contact surface 56 a of valve-closing permanent magnet 56, respectively. Lower disc 20 and upper disc 30 are formed from a magnetic material.
One end 22 of lower disc 20 is rotatably coupled to upper stem 18 by fitting of coupling pin 12 p into hole 24. One end 32 of upper disc 30 is rotatably coupled to upper stem 18 by fitting of coupling pin 12 q into hole 34. Coupling pins 12 p and 12 q are permitted only to rotate in holes 24 and 34.
With such a coupling structure, as compared with an example in which holes 24 and 34 have an elongated shape and coupling pins 12 p and 12 q are provided movably in the elongated holes, pressure on the contact surface between the surfaces of coupling pins 12 p and 12 q and inner walls of holes 24 and 34 can be lowered. Therefore, according to the present embodiment, a structure attaining suppression of development of abrasion at a position where stem 12 is coupled to lower disc 20 and upper disc 30 can be obtained. In addition, as movement of coupling pins 12 p and 12 q is restricted within holes 24 and 34, a coupled state of stem 12 and lower disc 20 and upper disc 30 can reliably be retained even if electromagnetically driven valve 10 is driven at high speed. Accordingly, reliability of electromagnetically driven valve 10 can be improved.
The other end 23 of lower disc 20 is supported by disc support base 51 so as to allow free oscillation of the disc, with a lower torsion bar 26 inserted in through hole 27 being interposed. The other end 33 of upper disc 30 is supported by disc support base 51 so as to allow free oscillation of the disc, with an upper torsion bar 36 inserted in through hole 37 being interposed. With such a structure, lower disc 20 and upper disc 30 oscillate around central axes 25 and 35 respectively, whereby driven valve 14 carries out reciprocating motion along the direction in which stem 12 extends.
Lower torsion bar 26 and upper torsion bar 36 apply elastic force to lower disc 20 and upper disc 30, in a manner moving the same counterclockwise around central axes 25 and 35, respectively. While the electromagnetic force from electromagnet 60 is not yet applied, lower disc 20 and upper disc 30 are positioned by lower torsion bar 26, upper torsion bar 36, and lower spring 11 at a position intermediate between an oscillation end on a valve-opening side and an oscillation end of a valve-closing side.
An operation of electromagnetically driven valve 10 will now be described.
Referring to FIG. 4, when driven valve 14 is at the valve-opening position, valve-opening/closing coil 62 is supplied with a current flowing in a direction shown with an arrow 111 around shaft portion 61 p of valve-opening/closing core 61. Here, on a side where upper disc 30 is located, the current flows from the back toward the front of the sheet showing FIG. 4. Accordingly, magnetic flux flows in valve-opening/closing core 61 in a direction shown with an arrow 112, and the electromagnetic force attracting upper disc 30 toward attraction and contact surface 61 a of electromagnet 60 is generated. On the other hand, lower disc 20 is attracted to attraction and contact surface 55 a by valve-opening permanent magnet 55. Consequently, upper disc 30 and lower disc 20 resist the elastic force of lower spring 11 in FIG. 1, and they are held at the oscillation end on the valve-opening side shown in FIG. 4.
Referring to FIG. 5, when current supply to valve-opening/closing coil 62 is stopped, the electromagnetic force generated by electromagnet 60 disappears. Then, upper disc 30 and lower disc 20 move away from attraction and contact surfaces 61 a and 55 a as a result of the elastic force of lower spring 11 in FIG. 1 respectively, and start to oscillate toward the intermediate position. The elastic force applied by lower torsion bar 26, upper torsion bar 36, and lower spring 11 attempts to hold upper disc 30 and lower disc 20 at the intermediate position. Therefore, at a position beyond the intermediate position, force in a direction reverse to an oscillating direction acts on upper disc 30 and lower disc 20 from lower torsion bar 26 and upper torsion bar 36. On the other hand, as inertial force acts on upper disc 30 and lower disc 20 in the oscillating direction, upper disc 30 and lower disc 20 oscillate as far as the position beyond the intermediate position.
Referring to FIG. 6, at the position beyond the intermediate position, a current is again fed to valve-opening/closing coil 62 in a direction shown with arrow 111. Here, on a side where lower disc 20 is located, the current flows from the front toward the back of the sheet showing FIG. 6. Accordingly, magnetic flux flows in valve-opening/closing core 61 in a direction shown with an arrow 132, and the electromagnetic force attracting lower disc 20 toward attraction and contact surface 61 b of electromagnet 60 is generated. On the other hand, upper disc 30 is attracted to attraction and contact surface 56 a by valve-closing permanent magnet 56.
Here, upper disc 30 is also attracted to attraction and contact surface 61 a of electromagnet 60 by the electromagnetic force generated by electromagnet 60. Here, the electromagnetic force is stronger between lower disc 20 and electromagnet 60 because a space therebetween is narrow. Therefore, upper disc 30 and lower disc 20 oscillate from the position beyond the intermediate position to the oscillation end on the valve-closing side shown in FIG. 6.
Here, lash adjuster 16 expands and contracts in the direction in which stem 12 extends, so as to accommodate registration error of driven valve 14 at the valve-closing position in FIG. 6. Accordingly, intimate contact of umbrella-shaped portion 13 with valve seat 42 is ensured, thereby ensuring sealing between intake port 17 and the combustion chamber. In the present embodiment, the parallel link mechanism causing lower disc 20 and upper disc 30 to simultaneously oscillate in order to allow reciprocating motion of driven valve 14 is adopted. Actually, however, registration error of driven valve 14 tends to occur due to dimension error or assembly error caused among disc parts. Therefore, lash adjuster 16 is particularly effective in electromagnetically driven valve 10 including the parallel link mechanism.
Thereafter, current supply to valve-opening/closing coil 62 is repeatedly started and stopped at a timing described above. In this manner, upper disc 30 and lower disc 20 are caused to oscillate between the oscillation ends on the valve-opening side and the valve-closing side, so that driven valve 14 carries out the reciprocating motion as a result of the oscillating movement.
FIG. 7 schematically shows movement of the lower disc and the upper disc oscillating from the oscillation end on the valve-closing side to the oscillation end on the valve-opening side as well as the lash adjuster lowered with such movement.
Referring to FIGS. 7 and 8, when lower disc 20 and upper disc 30 oscillate around the other ends 23 and 33 respectively, one ends 22 and 32 pivot around central axes 25 and 35 respectively, as if laying down an arc trail. More specifically, when lower disc 20 and upper disc 30 oscillate from the oscillation end on the valve-closing side to the intermediate position, one ends 22 and 32 are lowered, with a movement in a direction away from central axes 25 and 35. Meanwhile, when lower disc 20 and upper disc 30 oscillate to the oscillation end on the valve-opening side beyond the intermediate position, one ends 22 and 32 are lowered, with a movement in such a direction as approaching central axes 25 and 35.
When lower disc 20 and upper disc 30 oscillate from the oscillation end on the valve-closing side to the oscillation end on the valve-opening side with such movement of one ends 22 and 32, upper stem 18 is lowered while being displaced in a direction orthogonal to the direction in which stem 12 extends (hereinafter, also referred to as a direction orthogonal to stem 12). Similarly, when lower disc 20 and upper disc 30 oscillate from the oscillation end on the valve-opening side to the oscillation end on the valve-closing side, upper stem 18 is elevated while being displaced in the direction orthogonal to stem 12.
Here, end surface 18 a of upper stem 18 makes a sliding movement in a horizontal direction with respect to top surface 16 a of lash adjuster 16, so that displacement of upper stem 18 to the direction orthogonal to stem 12 is accommodated. FIG. 8 shows a slide portion 71 on top surface 16 a, where sliding movement with respect to end surface 18 a is made. Meanwhile, lash adjuster 16 is guided by guide ring 45 along the direction in which stem 12 extends. Therefore, even if force in the direction orthogonal to stem 12 is applied due to sliding movement with respect to end surface 18 a, lash adjuster 16 does not move in that direction. With such a structure, oscillating movement of lower disc 20 and upper disc 30 can be converted to reciprocating motion of driven valve 14, without transmitting displacement of upper stem 18 in the direction orthogonal to stem 12 to lower stem 19.
In order to make smaller a coefficient of friction, top surface 16 a may be subjected to surface treatment, such as polished finish of top surface 16 a of lash adjuster 16 or appropriate metal coating of top surface 16 a. In such a case, smooth sliding between end surface 18 a and top surface 16 a can be achieved, and abrasion resistance of slide portion 71 can be improved.
Preferably, lash adjuster 16 and upper stem 18 are formed from different materials. Then, such a state that end surface 18 a and top surface 16 a slid with respect to each other and brought in contact with each other are more susceptible to chemical bond can be prevented. This is also the case between lash adjuster 16 and guide ring 45 as well as between coupling pins 12 p, 12 q and lower disc 20 and upper disc 30, that are slid with respect to each other and brought in contact with each other in a similar manner.
Electromagnetically driven valve 10 according to the first embodiment of the present invention includes driven valve 14 having stem 12 serving as a valve shaft extending in a prescribed direction and umbrella-shaped portion 13 serving as a valve element provided at the tip end of stem 12 and opening/closing the intake/exhaust port, lower disc 20 and upper disc 30 serving as oscillating members having one ends 22 and 32 coupled to stem 12 and the other ends 23 and 33 supported by disc support base 51 serving as a supporting member so as to allow free oscillation of the disc respectively and oscillating around the other ends 23 and 33 so as to cause driven valve 14 to carry out reciprocating motion in the prescribed direction, lash adjuster 16 serving as a buffer member provided in stem 12 between the tip end where umbrella-shaped portion 13 is provided and positions where one ends 22 and 32 are coupled respectively, and guide ring 45 serving as a guide member guiding lash adjuster 16 along the prescribed direction. Lash adjuster 16 contracts and expands in the prescribed direction and accommodates displacement of stem 12 produced in the direction orthogonal to the prescribed direction as a result of reciprocating motion of driven valve 14.
Stem 12 has upper stem 18 serving as a first shaft portion located on a side where one ends 22 and 32 are coupled with respect to lash adjuster 16, and lower stem 19 serving as a second shaft portion located on a side of umbrella-shaped portion 13 with respect to lash adjuster 16. Upper stem 18 includes end surface 18 a serving as a first end surface abutting on top surface 16 a serving as the surface of lash adjuster 16. End surface 18 a makes sliding movement with respect to top surface 16 a of lash adjuster 16, so as to accommodate displacement of stem 12 produced in the direction orthogonal to the prescribed direction.
A plurality of lower discs 20 and upper discs 30 serving as the oscillating members are provided, with a distance from one another in the direction in which stem 12 serving as the valve shaft extends. Electromagnets 60 having valve-opening/closing coil 62 implemented by the monocoil are arranged among lower discs 20 and upper discs 30 serving as the plurality of oscillating members.
According to electromagnetically driven valve 10 in the first embodiment of the present invention structured as above, lash adjuster 16 can convert the oscillating movement of lower disc 20 and upper disc 30 into linear movement of stem 12, to achieve smooth reciprocating motion of driven valve 14. At the same time, sufficient sealing between umbrella-shaped portion 13 and valve seat 42 can be ensured by means of lash adjuster 16. In addition, guide ring 45 is provided in electromagnetically driven valve 10 so as to guide lash adjuster 16. Therefore, as compared with an example in which guide ring 45 guides stem 12, radius of curvature of slide surface 16 c and guide surface 45 c at a contact position can be made larger. Accordingly, pressure on the contact surface between slide surface 16 c and guide surface 45 c can be lowered, whereby abrasion resistance of guide ring 45 can be improved.
(Second Embodiment)
An electromagnetically driven valve according to the present embodiment is structured in a manner basically similar to the electromagnetically driven valve in the first embodiment. Therefore, description of a redundant structure will not be repeated.
FIG. 9 is an enlarged view of a region of the electromagnetically driven valve where the lash adjuster is provided. Referring to FIG. 9, an end surface 19 a is defined at a position of lower stem 19 connected to bottom surface 16 b of lash adjuster 16. In the present embodiment, the tip end of upper stem 18 is formed like a collar, such that end surface 18 a has an area larger than an area of end surface 19 a.
According to the electromagnetically driven valve in the second embodiment of the present invention structured as above, an effect similar to that in the first embodiment can be obtained. In addition, a contact area between end surface 18 a and top surface 16 a is reduced, so that smoother sliding movement of end surface 18 a with respect to top surface 16 a can be achieved.
(Third Embodiment)
An electromagnetically driven valve according to the present embodiment is structured in a manner basically similar to the electromagnetically driven valve in the first embodiment. Therefore, description of a redundant structure will not be repeated.
FIG. 10 is an enlarged view of a region of the electromagnetically driven valve where the lash adjuster is provided. Referring to FIG. 10, lash adjuster 16 is constituted of an upper lid 81 having top surface 16 a, a lower lid 83 arranged with a prescribed distance from upper lid 81 and having bottom surface 16 b, and a viscous member 82 filling a gap between upper lid 81 and lower lid 83, such as grease and oil. In the present embodiment, lower retainer 8 in FIG. 1 is not provided in lower stem 19. Lower spring 11 is housed in hollow portion 9 between the bottom surface of hollow portion 9 and lower lid 83.
In the electromagnetically driven valve according to third embodiment of the present invention, lash adjuster 16 serving as the buffer member includes upper lid 81 abutting on upper stem 18 serving as the first shaft portion, lower lid 83 connected to lower stem 19 serving as the second shaft portion and arranged at a position distant from upper lid 81, and viscous member 82 filling the gap between upper lid 81 and lower lid 83. The electromagnetically driven valve further includes lower spring 11 serving as the spring member, which is provided on a side opposite to viscous member 82, with either upper lid 81 or lower lid 83 being interposed, and applies elastic force to stem 12 serving as the valve shaft. Lower spring 11 serving as the spring member moves either upper lid 81 or lower lid 83.
According to the electromagnetically driven valve in the third embodiment of the present invention structured as above, an effect similar to that in the first embodiment can be obtained. In addition, lash adjuster 16 is formed integrally with lower retainer 8, whereby the number of parts of the electromagnetically driven valve can be reduced.
The first to third embodiments have described an example adopting a parallel link mechanism in an electromagnetically driven valve of a rotary drive type, however, the present invention is not limited thereto. The present invention is applicable to an electromagnetically driven valve including one disc having one end coupled to stem 12 and the other end supported by disc support base 51 so as to allow free oscillation of the disc and a plurality of electromagnets arranged above and below the disc and alternately applying electromagnetic force to the disc, in a manner similar to the first to third embodiments.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
Industrial Applicability
The present invention is mainly utilized as an intake valve or an exhaust valve in a gasoline engine, a diesel engine, or the like.

Claims

1. An electromagnetically driven valve comprising:

a driven valve (14) having a valve shaft (12) extending in a prescribed direction and a valve element (13) provided at a tip end of said valve shaft (12) and opening/closing an intake/exhaust port;

an oscillating member (20, 30) having one end (22, 32) coupled to said valve shaft (12) and the other end (23, 33) supported by a supporting member (51) so as to allow free oscillation of the oscillating member and oscillating around said other end (23, 33) so as to cause said driven valve (14) to carry out reciprocating motion in said prescribed direction;

a buffer member (16) provided in said valve shaft (12) between the tip end where said valve element (13) is provided and a position where said one end (22, 32) is coupled; and

a guide member (45) guiding said buffer member (16) along said prescribed direction; wherein

said buffer member (16) contracts and expands in said prescribed direction and accommodates displacement of said valve shaft (12) produced in a direction orthogonal to said prescribed direction as a result of the reciprocating motion of said driven valve (14),

said valve shaft (12) has a first shaft portion (18) including a first end surface (18 a) abutting on a surface (16 a) of said buffer member (16) and located on a side where said one end (22, 32) is coupled with respect to said buffer member (16), and a second shaft portion (19) located on a side of said valve element (13) with respect to said buffer member (16),

said first end surface (18 a) makes sliding movement with respect to the surface (16 a) of said buffer member (16), so that displacement of said valve shaft (12) produced in the direction orthogonal to said prescribed direction is accommodated,

said second shaft portion (19) includes a second end surface (19 a) connected to a surface (16 b) of said buffer member (16), and

said first shaft portion (18) is formed such that said first end surface (18 a) has an area larger than that of said second end surface (19 a).

2. (canceled)

3. (canceled)