EP1779011A1

EP1779011A1 - Electromagnetically driven valve

Info

Publication number: EP1779011A1
Application number: EP05755656A
Authority: EP
Inventors: Masahiko c/o TOYOTA JIDOSHA KABUSHIKI ASANO; Yutaka c/o TOYOTA JIDOSHA KABUSHIKI SUGIE
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2004-08-19
Filing date: 2005-06-28
Publication date: 2007-05-02
Also published as: CN101006301A; US20080029723A1; JP2006057517A; WO2006018934A1

Abstract

An electromagnetically driven valve includes a driven valve having a stem (12) and carrying out reciprocating motion along a direction in which the stem (12) extends, a disc support base (51), a lower disc (20) having one end coupled to the stem (12) and the other end supported by the disc support base (51) so as to allow free oscillation of the lower disc and oscillating around a central axis (25) extending at the other end, and a lower torsion bar (26) provided so as to extend along the central axis (25) and fixed to the other end. The lower torsion bar (26) has a fix portion (4) fixed to the disc support base (51), and a phase angle thereof around the central axis (25) with respect to the disc support base (51) can be adjusted. With such a structure, the driven valve can carry out reciprocating motion in a stable manner, and energy loss can be reduced.

Description

DESCRIPTION

Electromagnetically Driven Valve

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

Japanese Utility Model Laying-Open No. 61-200919 discloses a knock pin having serration formed on an outer circumferential surface of a pin body along an axial direction thereof. In addition, Japanese Utility Model Laying-Open No. 61-200920 discloses a knock pin having an elastic body provided on an outer circumferential surface of a pin body, the elastic body being pressed against and brought in contact with a wall surface of an insertion hole.

Japanese Utility Model Publication No. 14-20004 discloses an apparatus for preventing loosening of a male screw, which includes a male screw threaded on an outer circumference and having a notch in a part of the outer circumference, and a locknut arranged on an outer circumference of the notch. Moreover, Japanese Utility Model Publication No. 37-9013 discloses a screw of which loosening is prevented, which includes a female screw shaped like a case, a screw screwed into the female screw, and a set screw having a disc-shaped head and screwed in an axial direction from a head of the female screw toward an inner end of the screw. An electromagnetically driven valve called a rotary drive 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 on 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 such an electromagnetically driven valve, a torsion bar and a helical spring are provided such that the disc is located at a position intermediate between the valve- opening position and the valve-closing position while the electromagnetic force is not applied. Based on this assumption, electromagnetic force for overcoming spring force of these springs is calculated at each lift position of the driven valve, and current supply to the electromagnet is controlled in accordance with a calculation result. On the other hand, in the torsion bar and the helical spring, error in shape inevitable in the manufacturing step or assembly error with respect to the disc support base or the stem is produced, which results in failure in accurate setting of the disc to the intermediate position. In such a case, error in spring load imposed on the driven valve at each lift position is produced, and accurate electromagnetic force for overcoming the spring load cannot be calculated. Then, movement of the driven valve becomes unstable, a speed of the valve when seated (sound produced from operation) is high, or electric power for correcting such error is wasted in the electromagnet.

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 stable reciprocating motion of the driven valve and reduction in energy loss.

An electromagnetically driven valve according to the present invention is actuated by cooperation of electromagnetic force and elastic force. The electromagnetically driven valve includes: a driven valve having a valve shaft and carrying out reciprocating motion along a direction in which the valve shaft extends; a supporting member provided at a position apart from the driven valve; an oscillating member having one end coupled to the valve shaft and the other end supported by the supporting member so as to allow free oscillation of the oscillating member and oscillating around an axis extending at the other end; and a torsion spring provided so as to extend along the axis and fixed to the other end. The torsion spring includes a fix portion fixed to the supporting member, and a phase angle thereof around the axis with respect to the supporting member can be adjusted.

According to the electromagnetically driven valve structured as above, the fix portion is provided, so that the torsion spring is attached to the supporting member with a phase angle around the axis extending at the other end being adjusted, and fixed to that position. Accordingly, the spring load imposed by the torsion spring onto the oscillating member can accurately be set to a value determined in design. Here, when the oscillating member actually oscillates, no error is produced between the spring load imposed by the torsion spring onto the oscillating member and the spring load calculated in design. Therefore, electromagnetic force based on the spring load in design is applied to the oscillating member, whereby stable reciprocating motion of the driven valve is achieved. As it is not necessary to apply the electromagnetic force for eliminating the error in the spring load, waste of electric power in the electromagnetically driven valve can be prevented.

Preferably, a plurality of oscillating members are provided, with a distance from each other in a direction in which the valve shaft extends. According to the electromagnetically driven valve structured as above, an effect as described above can be obtained in the electromagnetically driven valve adopting a parallel link mechanism.

Preferably, the fix portion includes an outer circumferential surface of the torsion spring, having serration formed. The supporting member has an opening for receiving the fix portion. An inner wall of the opening has serration formed, which is engaged with the serration formed on the fix portion. According to the electromagnetically driven valve structured as above, engagement between the serration formed on the outer circumferential surface of the torsion spring and the serration formed on the inner wall of the opening is shifted, so that a phase angle of the torsion spring around the axis with respect to the supporting member can be adjusted. In addition, as engagement between the serrations is strong, the torsion spring can further reliably be fixed in the adjusted position.

Preferably, the fix portion includes an outer circumferential surface of the torsion spring, implemented as a tapered surface. The supporting member has an opening for receiving the fix portion. An inner wall of the opening has a tapered surface formed, which is pressed against and brought in contact with the tapered surface formed on the fix portion. According to the electromagnetically driven valve structured as above, the torsion spring is pressed into the opening with the tapered surfaces being slid, so that a phase angle of the torsion spring around the axis with respect to the supporting member can arbitrarily be adjusted. In addition, as wedge force is produced between the outer circumferential surface of the torsion spring and the inner wall of the opening, the torsion spring can reliably be fixed in the adjusted position. Moreover, the outer circumferential surface of the torsion spring should only be tapered. Therefore, even if workability of the torsion spring is poor, such a shape can readily be obtained.

Preferably, the fix portion includes an outer circumferential surface of the torsion spring, having a male screw formed. The supporting member has an opening for receiving the fix portion. An inner wall of the opening has a female screw formed such that the male screw formed on the fix portion is screwed in. A locknut is fastened to the opening from a side opposite to a direction in which the fix portion is inserted.

According to the electromagnetically driven valve structured as above, an angle for the torsion spring to be screwed into the opening is modified, so that a phase angle of the torsion spring around the axis with respect to the supporting member can arbitrarily be adjusted. In addition, loosening of the torsion spring can be prevented by repulsive force produced between the locknut and the torsion spring. Accordingly, the torsion spring can reliably be fixed in the adjusted position.

As described above, according to the present invention, an electromagnetically driven valve attaining stable reciprocating motion of the driven valve and reduction in energy loss 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 perspective view of cross-section of the electromagnetically driven valve along the line IV-IV in Fig. 1. Fig. 5 is a cross-sectional view of the electromagnetically driven valve along the line V-V in Fig. 4. ' -

Fig. 6 is an end view of a lower torsion bar viewed in a direction of an arrow VI in Fig. 5.

Fig. 7 is a schematic diagram showing the upper disc and the lower disc at an oscillation end on a valve-opening side.

Fig. 8 is a schematic diagram showing the upper disc and the lower disc at an intermediate position.

Fig. 9 is a schematic diagram showing the upper disc and the lower disc at an oscillation end on a valve-closing side. Fig. 10 is a graph showing a relation between a lift amount of the driven valve and resultant force of the upper torsion bar and the lower torsion bar.

Fig. 11 is a cross-sectional view showing an electromagnetically driven valve according to a second embodiment of the present invention. Fig. 12 is a cross-sectional view showing a variation of the electromagnetically driven valve in Fig. 11.

Fig. 13 is a cross-sectional view showing an electromagnetically driven valve according to a third embodiment of the present invention. Fig. 14 is a cross-sectional view showing the step of adjusting load balance in the electromagnetically driven valve in Fig. 13.

Best Modes for Carrying Out the Invention

Embodiments of the present invention will be described with reference to the drawings.

(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. I₃ 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, 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, a disc support base 51 provided in parallel to stem 12 at a position apart from stem 12, a valve-opening/closing electromagnet 60 (hereinafter, also simply referred to as electromagnet 60) provided in disc support base 51 and generating the electromagnetic force, and a lower torsion bar 26 and an upper torsion bar 36 provided in lower disc 20 and upper disc 30 respectively and applying the elastic force to these discs. 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. Driven valve 14 further includes an umbrella-shaped portion 13 formed at an end of stem 12. 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.

Stem 12 is constituted of a lower stem 12m continuing from umbrella-shaped portion 13 and an upper stem 12n connected to lower stem 12m with a lash adjuster 16 being interposed. Lash adjuster 16 with a property more likely to contract and less likely to expand attains a function as a buffer member between upper stem 12n and lower stem 12m. Lash adjuster 16 accommodates registration error of driven valve 14 at the valve-closing position, and brings umbrella-shaped portion 13 into contact with valve seat 42 in an ensured manner. Lower stem 12m has a coupling pin 12p projecting from its outer circumferential surface formed, and upper stem 12n has a coupling pin 12q projecting from its outer circumferential surface formed in a position away from coupling pin 12p.

In cylinder head 41, a valve guide 43 for slidably guiding lower stem 12m in an axial direction is provided, and a stem guide 45 for slidably guiding upper stem 12n in an axial direction is provided in a position away from valve guide 43. Valve guide 43 and stem guide 45 are formed from a metal material such as stainless steel, in order to endure high-speed slide movement with respect to stem 12.

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 61a and 61b (hereinafter referred to as surface 61a, surface 61b). Valve-opening/closing core 61 has a shaft portion 6 Ip 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 6 Ip, and implemented by a monocoil (a coil implemented by a continuous wire). 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 55a (hereinafter referred to as surface 55 a), and a space in which lower disc 20 oscillates is defined between surface 55a and surface 61b of electromagnet 60. In addition, valve-closing permanent magnet 56 has an attraction and contact surface 56a (hereinafter referred to as surface 56a), and a space in which upper disc 30 oscillates is defined between surface 56a and surface 61a 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 21a and 21b 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 21a and 21b face surface 61b of electromagnet 60 and surface 55a of valve- opening permanent magnet 55, respectively.

Arm portion 21 has a notch 29 formed on the side of one end 22, and elongated 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 3 Ib, a surface 3 Ia, a notch 39, an elongated 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 21a, surface 21b, notch 29, elongated hole 24, shaft receiving portion 28, through hole 27, and central axis 25 of lower disc 20 respectively are formed. Surfaces 31a and 3 Ib face surface 61a of electromagnet 60 and surface 56a 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 coupled to lower stem 12m so as to allow free oscillation of the disc, by insertion of coupling pin 12p into elongated hole 24. One end 32 of upper disc 30 is coupled to upper stem 12n so as to allow free oscillation of the disc, by insertion of coupling pin 12q into elongated hole 34.

In the following, a structure of lower torsion bar 26 and a structure for attachment of lower disc 20 will be described. It is noted that upper torsion bar 36 and upper disc 30 also have similar structures.

Referring to Fig. 1 and Figs. 4 to 6, lower torsion bar 26 is fixed at the other end 23 in such a state that it is inserted into through hole 27. Lower torsion bar 26 is formed from a spring steel, and shaped like a bar extending along central axis 25. Lower torsion bar 26 has a fix portion 4 fixed to disc support base 51 at one end thereof. Lower torsion bar 26 is rotatably supported by disc support base 51, on a side opposite to fix portion 4.

An outer circumferential surface 4a of fix portion 4 has serration formed. The serration is implemented by grooves extending in the axial direction and provided side by side in a circumferential direction. The number of grooves provided side by side in the circumferential direction on outer circumferential surface 4a may be set to 20, for example, or alternatively, it may be set to different number. Disc support base 51 has an opening 52 for receiving fix portion 4 formed. An inner wall of opening 52 has serration formed, which is engaged with the serration formed on outer circumferential surface 4a. When fix portion 4 is inserted in opening 52, the serration formed on outer circumferential surface 4a of fix portion 4 and the serration formed on the inner wall of opening 52 are engaged with each other, so that lower torsion bar 26 is fixed to disc support base 51. The other end 23 of lower disc 20 is thus supported by disc support base 51 so as to allow free oscillation of the disc around central axis 25. Similarly, the other end 33 of upper disc 30 is supported by disc support base 51 so as to allow free oscillation of the disc around central axis 35, with upper torsion bar 36 being interposed. Oscillation of lower disc 20 and upper disc 30 around central axes 25 and 35 respectively can cause driven valve 14 to carry out reciprocating motion. Lower torsion bar 26 applies elastic force to lower disc 20, in a manner moving the same clockwise around central axis 25. Upper torsion bar 36 applies elastic force to upper disc 3.0, in a manner moving the same counterclockwise around central axis 35. While the electromagnetic force from electromagnet 60 is not yet applied, lower disc 20 and upper disc 30 are positioned by elastic force of lower torsion bar 26 and upper torsion bar 36 at a position intermediate between an oscillation end on a valve-opening side and an oscillation end of a valve-closing side.

In the present embodiment, lower torsion bar 26 and upper torsion bar 36 are fixed to disc support base 51, with a position where the serration formed on outer circumferential surface 4a of fix portion 4 is engaged with the serration formed on the inner wall of opening 52 being adjusted. For example, if lower disc 20 and upper disc 30 are positioned closer to the oscillation end on the valve-opening side with respect to the intermediate position described above, counterclockwise elastic force by upper torsion bar 36 overcomes clockwise elastic force by lower torsion bar 26. Here, for example, in order to increase the elastic force by lower torsion bar 26, the position of engagement of the serrations should be adjusted such that fix portion 4 of lower torsion bar 26 is shifted clockwise with respect to opening 52. In this manner, fix portion 4 attains a function as a mechanism for adjusting load balance between lower torsion bar 26 and upper torsion bar 36. By means of fix portion 4, lower disc 20 and upper disc 30 can accurately be positioned at the intermediate position between the oscillation end on the valve-opening side and the oscillation end of the valve-closing side.

An operation of electromagnetically driven valve 10 will now be described. Referring to Fig. 7, 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 61p 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. 7. 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 surface 61a of electromagnet 60 is generated. On the other hand, lower disc 20 is attracted to surface 55a by valve-opening permanent magnet 55. Consequently, upper disc 30 and lower disc 20 resist the elastic force of lower torsion bar 26 arranged around central axis 25, and they are held at the oscillation end on the valve-opening side shown in Fig. 7. Referring to Fig. 8, 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 surfaces 61a and 55a as a result of the elastic force of lower torsion bar 26, respectively, and start to oscillate toward the intermediate position. The elastic force applied by lower torsion bar 26 and upper torsion bar 36 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 upper torsion bar 36. On the other hand, as inertia! 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. 9, 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. 9. 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 surface 61b of electromagnet 60 is generated. On the other hand, upper disc 30 is attracted to surface 56a by valve- closing permanent magnet 56.

Here, upper disc 30 is also attracted to surface 61a 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. 9. 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 can carry out the reciprocating motion as a result of the oscillating movement.

Electromagnetically driven valve 10 according to the first embodiment of the present invention is actuated by cooperation of the electromagnetic force and the elastic force. Electromagnetically driven valve 10 includes driven valve 14 having stem 12 serving as the valve shaft and carrying out the reciprocating motion along the direction in which stem 12 extends, disc support base 51 serving as the supporting member .provided at a position apart from driven valve 14, 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 so as to allow free oscillation of the disc respectively and oscillating around central axes 25 and 35 extending at the other ends 23 and 33, and lower torsion bar 26 and upper torsion bar 36 serving as the torsion springs extending along central axes 25 and 35 and fixed to the other ends 23 and 33. Lower torsion bar 26 and upper torsion bar 36 have fix portion 4 fixed to disc support base 51, and a phase angle thereof around central axes 25 and 35 with respect to disc support base 51 can be adjusted.

Fix portion 4 includes outer circumferential surface 4a of lower torsion bar 26 and upper torsion bar 36, having the serration formed. Disc support base 51 has opening 52 for receiving fix portion 4 formed. The inner wall of opening 52 has the serration formed, which is engaged with the serration formed in fix portion 4.

In the present embodiment, the mechanism for adjusting load balance by means of fix portion 4 has been provided in each of lower disc 20 and upper disc 30, however, the mechanism may be provided in either one of them. If the mechanism for adjusting load balance is provided in each of lower disc 20 and upper disc 30, load balance between lower torsion bar 26 and upper torsion bar 36 can readily be varied. Therefore, elastic force applied to lower disc 20 and upper disc 30 during oscillation can freely be adjusted.

According to electromagnetically driven valve 10 in the first embodiment of the present invention as structured above, fix portion 4 is provided in lower torsion bar 26 and upper torsion bar 36, so that lower disc 20 and upper disc 30 can accurately be positioned at the intermediate position between the oscillation ends on the valve-opening side and the valve-closing side while electromagnetic force from electromagnet 60 is not applied.

Fig. 10 shows a relation between a lift amount of the driven valve and resultant force of the upper torsion bar and the lower torsion bar, and the resultant force of upper torsion bar 36 and lower torsion bar 26 is represented on the ordinate assuming a direction moving driven valve 14 upward as positive. A straight line 76 in Fig. 10 represents a relation between the lift amount and the resultant force in design, that is, a relation between the same when lower disc 20 and upper disc 30 are accurately positioned at the intermediate position while electromagnetic force from electromagnet 60 is not applied. A straight line 78 in Fig. 10 represents a relation between the lift amount and the resultant force when lower disc 20 and upper disc 30 are positioned closer to the valve-opening side with respect to the intermediate position, while a straight line 77 in Fig. 10 represents a relation between the lift amount and the resultant force when lower disc 20 and upper disc 30 are positioned closer to the valve-closing side with respect to the intermediate position.

As can been seen from comparison of straight lines 76 to 78, if lower disc 20 and upper disc 30 are set to a position displaced from the intermediate position, a point where elastic force of two torsion bars are balanced is displaced from a balance point P in design in a range indicated by an arrow 79 in Fig. 10. Here, the resultant force of the two torsion bars applied to driven valve 14 at each lift position fluctuates, for example, in a range shown with an arrow 80 in Fig. 10, and error is produced with respect to the resultant force set in design, that is, with respect to the resultant force represented by straight line 76. In the present embodiment, however, lower disc 20 and upper disc 30 are accurately positioned at the intermediate position between the oscillation ends on the valve-opening side and the valve-closing side, and therefore, no such error is produced. Accordingly, the electromagnetic force calculated based on the resultant force set in design is applied to lower disc 20 and upper disc 30, whereby stable reciprocating motion of driven valve 14 can be achieved. (Second Embodiment)

An electromagnetically driven valve according to the present embodiment is structured in a manner basically similar to electromagnetically driven valve 10 in the first embodiment. Therefore, description of a redundant structure will not be repeated.

Fig. 11 shows a region similar to that shown in Fig. 5. Referring to Fig. 11, in the present embodiment, outer circumferential surface 4a of fix portion 4 is formed as a tapered surface. In other words, outer circumferential surface 4a extends in a manner inclined with respect to central axis 25, and is implemented by a side surface of a frustum of a cone formed along central axis 25. On the inner wall of opening 52, a tapered surface being in surface contact with outer circumferential surface 4a while lower torsion bar 26 is inserted in opening 52 is formed. Fix portion 4 has a hexagonal hole 84 formed from a side of an end surface 4c of fix portion 4. Disc support base 51 has a female screw hole 81 formed, which is opened from a side of a side surface 51c and continues to opening 52. A nut 82 is tightened into female screw hole 81 with a magnitude of tightening force P. Nut 82 has a hexagonal hole 83 penetrating along central axis 25 formed. Hexagonal hole 83 is larger than hexagonal hole 84. Nut 82 presses end surface 4c of fix portion 4, so that the tapered surface formed on outer circumferential surface 4a is pressed against and brought in contact with the tapered surface formed on the inner wall of opening 52. Here, an angle between central axis 25 and an edge line of outer circumferential surface 4a is assumed as θ (a tapered angle of outer circumferential surface 4a is 2Θ). Then, fastening force N of fix portion 4 with respect to opening 52 having a magnitude of P/tanθ is produced. In the present embodiment, a special hexagonal wrench having a through hole formed in an axial direction and a normal hexagonal wrench are used to fix lower torsion bar 26 to disc support base 51. More specifically, nut 82 is lightly tightened in such a state that fix portion 4 is inserted in opening 52. Then, the tip end of the special hexagonal wrench is fitted to hexagonal hole 83, and the normal hexagonal wrench is inserted in the through hole formed in the special hexagonal wrench for fitting to hexagonal hole 84. In such a state, lower torsion bar 26 is positioned so as to attain an optimal phase angle by turning the normal hexagonal wrench, and thereafter the special hexagonal wrench is turned. Lower torsion bar 26 is thus fixed in that position. According to the electromagnetically driven valve in the second embodiment of the present invention, fix portion 4 includes outer circumferential surface 4a of lower torsion bar 26 formed as the tapered surface. Disc support base 51 has opening 52 for receiving fix portion 4. The inner wall of opening 52 has the tapered surface formed, which is pressed against and brought in contact with the tapered surface formed on fix portion 4.

Disc support base 51 has female screw hole 81 continuing to opening 52 formed. Nut 82 serving as a pressing member for pressing end surface 4c of fix portion 4 and pressing and contacting the tapered surfaces formed on outer circumferential surface 4a and the inner wall of opening 52 with each other is fastened to female screw hole 81. Fix portion 4 has hexagonal hole 84 formed from the side of end surface 4c, which serves as a first tool insertion hole in which the hexagonal wrench serving as a tool for turning fix portion 4 around rotation axis 25 is inserted. Nut 82 has hexagonal hole 83 formed, which serves as a second tool insertion hole in which the special hexagonal wrench serving as a tool for exposing hexagonal hole 84 for fastening nut 82 is inserted.

Fig. 12 shows a variation of the electromagnetically driven valve in Fig. 11. Referring to Fig. 12, in the present variation, a plate 71 joined to end surface 4c of fix portion 4 is provided, instead of nut 82 in Fig. 11. Plate 71 extends over end surface 4c as far as side surface 51c of disc support base 51, like a collar. Plate 71 has an elongated hole 7 Ih formed in a position above side surface 51c, which is elongated in a circumferential direction around central axis 25. Plate 71 is fastened to disc support base 51 by a bolt 72 inserted through elongated hole 7 Ih. In the present variation, bolt 72 is fastened with plate 71 being turned, so as to fix lower torsion bar 26 at an optimal phase angle.

In the present embodiment, description has been given solely in connection with lower torsion bar 26, however, fix portion 4 as described above should only be provided in at least one of lower torsion bar 26 and upper torsion bar 36.

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, according to the present embodiment, the mechanism for adjusting load balance by means of fix portion 4 is implemented by abutment of the tapered surfaces. Therefore, lower torsion bar 26 can be positioned at any phase angle around central axis 25, whereby adjustment of load balance with a further higher degree of freedom can be achieved. In addition, as large fastening force can be generated by virtue of wedge effect, loosening of lower torsion bar 26 from opening 52 can be prevented. (Third Embodiment) An electromagnetically driven valve according to the present embodiment is structured in a manner basically similar to electromagnetically driven valve 10 in the first embodiment. Therefore, description of a redundant structure will not be repeated.

Fig. 13 shows a region similar to that shown in Fig. 5. Referring to Fig. 13, in the present embodiment, outer circumferential surface 4a of fix portion 4 has a male screw formed. Fix portion 4 has a hexagonal hole 88 formed from a side of end surface 4c of fix portion 4. On the other hand, the inner wall of opening 52 has a female screw formed, into which a male screw formed on outer circumferential surface 4a is screwed. A locknut 86 is fastened to opening 52 from a side opposite to fix portion 4, and end surface 4c of fix portion 4 is pressed by an end surface 86c of locknut 86 facing end surface 4c. Locknut 86 has a hole 87 formed, which is penetrated in a direction in which central axis 25 extends.

The step of adjusting load balance in the electromagnetically driven valve shown in Fig. 13 will now be described. Referring to Fig. 14, initially, fix portion 4 is fastened to opening 52. Referring to Fig. 13, locknut 86 is lightly fastened from the opposite side, and the hexagonal wrench is fitted into hexagonal hole 88 through hole 87. In such a state, lower torsion bar 26 is positioned at an optimal phase angle by turning the hexagonal wrench, and locknut 86 is further rigidly fastened. Lower torsion bar 26 is thus fixed to that position. According to the electromagnetically driven valve in the third embodiment of the present invention, fix portion 4 includes outer circumferential surface 4a of lower torsion bar 26 having the male screw formed. Disc support base 51 has opening 52 for receiving fix portion 4. The inner wall of opening 52 has the female screw formed such that the male screw formed on fix portion 4 is screwed in. Locknut 86 is fastened to opening 52 from the side opposite to the direction in which fix portion 4 is inserted. Fix portion 4 has hexagonal hole 88 formed from the side of end surface 4c, which serves as a tool insertion hole in which the hexagonal wrench serving as a tool for turning fix portion 4 around rotation axis 25 is inserted. Locknut 86 has hole 87 for exposing hexagonal hole 88 formed.

In the present embodiment, description has been given solely in connection with lower torsion bar 26, however, fix portion 4 as described above should only be provided in at least one of lower torsion bar 26 and upper torsion bar 36. According to the electromagnetically driven valve in the third embodiment of the present invention, an effect similar to that in the first embodiment can be obtained. In addition, according to the present embodiment, the mechanism for adjusting load balance by means of fix portion 4 is implemented by a screw structure. Therefore, lower torsion bar 26 can be positioned at any phase angle around central axis 25, whereby adjustment of load balance with a further higher degree of freedom can be achieved. 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 actuated by cooperation of electromagnetic force and elastic force, comprising: a driven valve (14) having a valve shaft (12) and carrying out reciprocating motion along a direction in which said valve shaft (12) extends; a supporting member (51) provided at a position apart from said driven valve

(14); an oscillating member (20, 30) having one end (22, 32) coupled to said valve shaft (12) and the other end (23, 33) supported by said supporting member (51) so as to allow free oscillation of the oscillating member and oscillating around an axis (25, 35) extending at said other end (23, 33); and a torsion spring (26, 36) provided so as to extend along said axis (25, 35) and fixed to said other end (23, 33); wherein said torsion spring (26, 36) includes a fix portion (4) fixed to said supporting member (51), and a phase angle of the fix portion around said axis (25, 35) with respect to said supporting member (51) can be adjusted.

2. The electromagnetically driven valve according to claim 1, wherein a plurality of said oscillating members (20, 30) are provided, with a distance from each other in a direction in which said valve shaft (12) extends.

3. The electromagnetically driven valve according to claim 1, wherein said fix portion (4) includes an outer circumferential surface (4a) of said torsion spring (26, 36) having serration formed, said supporting member (51) has an opening (52) for receiving said fix portion (4), and an inner wall of said opening (52) has serration formed, which is engaged with the serration formed on said fix portion (4).

4. The electromagnetically driven valve according to claim 1, wherein said fix portion (4) includes an outer circumferential surface (4a) of said torsion spring (26, 36) implemented as a tapered surface, said supporting member (51) has an opening (52) for receiving said fix portion (4), and an inner wall of said opening (52) has a tapered surface formed, which is pressed against and brought in contact with the tapered surface formed on said fix portion (4).

5. The electromagnetically driven valve according to claim 1, wherein said fix portion (4) includes an outer circumferential surface (4a) of said torsion spring (26, 36) having a male screw formed, said supporting member (51) has an opening (52) for receiving said fix portion (4), and an inner wall of said opening (52) has a female screw formed such that the male screw formed on said fix portion (4) is screwed in, and a locknut (86) is fastened to said opening (52) from a side opposite to a direction in which said fix portion (4) is inserted.