JP2013217265A - Electromagnetic actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic actuator which prevents a permanent magnet from being cracked by a shock in operation, in the electromagnetic actuator adapted to a valve lift adjusting device of an internal combustion engine.SOLUTION: An electromagnetic actuator 40 attracts a plunger 50 by an electromagnetic force generated by electrifying a coil 42, thereby advancing a regulating pin 60. When the electrification of the coil 42 stops and the regulating pin is pushed back by the torque of a cam shaft, a permanent magnet 41 fixed to a basal end side of the regulating pin 60 on the plunger 50 attracts an attracted surface 511 of the plunger 50 by a magnetic attractive force in a retreating direction. Since the permanent magnet 41 is fixed, the permanent magnet 41 can be prevented from being cracked by a shock in operation compared with a conventional electromagnetic actuator by which the permanent magnet is operated.

Description

  The present invention relates to an electromagnetic actuator that is applied to a valve lift adjusting device for an internal combustion engine and switches a slider position by advancing a regulating pin to engage with an engaging groove.

  2. Description of the Related Art Conventionally, in a valve lift adjustment device that adjusts the lift amount of an intake valve or an exhaust valve of an internal combustion engine, the position of a slider provided so as to be movable relative to the camshaft in an axial direction while rotating together with the camshaft is known. It has been. Further, as a means for switching the position of the slider, an electromagnetic actuator is known in which a restriction pin is operated by electromagnetic force and a tip end portion of the restriction pin is fitted in an engagement groove formed in the slider. For example, in the electromagnetic actuator described in Patent Document 1, when the coil is energized, the restriction pin is activated by the magnetic force of the permanent magnet repelling the electromagnetic force.

US Pat. No. 6,967,550

  In the electromagnetic actuator of Patent Document 1, the permanent magnet sandwiched between the two disks operates in the axial direction integrally with the restriction pin, so that the permanent magnet is broken by an impact during operation, and as a result, the actuator becomes inoperable. There is a risk. Therefore, if the thickness of the disk is increased in order to increase the impact strength, there is a problem that the weight of the movable part increases and the operating speed decreases.

  The present invention was created in view of the above points, and an object of the present invention is to prevent a permanent magnet from being broken by an impact during operation in an electromagnetic actuator applied to a valve lift adjusting device for an internal combustion engine. It is to provide an electromagnetic actuator.

  The present invention is applied to a valve lift adjustment device for an internal combustion engine, and is an electromagnetic actuator that operates a restriction pin using a magnet attracting force of a permanent magnet and an electromagnetic force generated by energization of a coil. The permanent magnet attracted in the backward direction is fixed to the base end side of the restriction pin with respect to the plunger.

  By fixing the permanent magnet, it is possible to prevent the permanent magnet from being cracked by an impact at the time of operation of the electromagnetic actuator of Patent Document 1 that operates the permanent magnet, and as a result, the actuator can be prevented from becoming inoperable.

  Moreover, it is preferable that the holder which accommodates a permanent magnet is formed with a magnetic body. Thereby, the magnetic leakage of a permanent magnet can be suppressed and the magnet attractive force can be increased. In addition, if the permanent magnet is broken, the shatter pieces can be prevented from scattering.

  Furthermore, in the electromagnetic actuator of the present invention applied to the valve lift adjusting device, when the tip of the restriction pin is separated from the engagement groove, the restriction pin is pushed back by the torque of the camshaft. There is no need for drive means for retreating. Therefore, the physique can be made smaller than an electromagnetic actuator having an electromagnetic drive unit in both forward and backward directions.

It is a figure when it starts to shift from a small lift state to a large lift state in a valve lift adjustment device to which an electromagnetic actuator according to an embodiment of the present invention is applied. It is the II-II sectional view taken on the line of FIG. It is a figure in the middle of changing from a small lift state to a large lift state in a valve lift adjustment device to which an electromagnetic actuator by one embodiment of the present invention is applied. It is the IV-IV sectional view taken on the line of FIG. It is a figure when it starts to shift from a large lift state to a small lift state in a valve lift adjustment device to which an electromagnetic actuator according to an embodiment of the present invention is applied. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. It is sectional drawing which shows the last retracted position of the plunger of the electromagnetic actuator by one Embodiment of this invention, and a control pin. It is the VIII section enlarged view of FIG. It is the IX section enlarged view of FIG. It is sectional drawing which shows the most advanced position of the plunger of the electromagnetic actuator by one Embodiment of this invention, and a control pin. In the electromagnetic actuator by one Embodiment of this invention, it is a characteristic view which shows the force which acts on a plunger at the time of a non-energization. In the electromagnetic actuator by one Embodiment of this invention, it is a characteristic view which shows the force which acts on a plunger at the time of electricity supply.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(One embodiment)
An electromagnetic actuator according to an embodiment of the present invention is applied to a valve lift adjusting device that adjusts a lift amount of an intake valve of an internal combustion engine.

First, the valve lift adjusting device will be described with reference to FIGS. In the following description, “FIG. 1 etc.” refers to FIGS. 1, 3 and 5, and “FIG. 2 etc.” refers to FIGS. 2, 4 and 6.
As shown in FIGS. 1 to 6, the valve lift adjusting device 10 is linked through rollers 31 and 32 and swing arms 33 and 34 by a cam integrally provided on a slider 21 that rotates together with the camshaft 11. The lift amount of the intake valves 91 and 92 is adjusted.

The camshaft 11 rotates in a fixed direction in conjunction with a crankshaft (not shown). This rotational direction corresponds to the counterclockwise direction when the camshaft 11 is viewed from the left side in FIG.
As shown in FIG. 2 and the like, the camshaft 11 has spline external teeth formed on the outer surface of the portion where the slider 21 is fitted. In addition, illustration of a spline external tooth is abbreviate | omitted in FIG.
The cylindrical slider 21 is provided so as to be able to move relative to the camshaft 11 in the axial direction while rotating together with the camshaft 11 by engaging the spline inner teeth formed on the inner surface with the spline outer teeth of the camshaft 11. Yes. That is, the slider 21 is provided so as to be capable of reciprocating in the axial direction between two slider limiters 12 and 22 fixed to the camshaft 11 in a bowl shape.

Two sets of switching portions 13 and 23, small lift cams 18 and 28, and large lift cams 19 and 29 are integrally provided at both ends of the slider 21. The switching units 13 and 23 switch the position of the slider 21 in the axial direction with respect to the camshaft 11.
Hereinafter, the left switching unit in FIG. 1 is referred to as a first switching unit 13, and the right switching unit in FIG. 1 is referred to as a second switching unit 23. Since these two sets of configurations are basically the same, the configuration of the first switching unit 13, the first small lift cam 18 and the first large lift cam 19 will be described as a representative.

The first switching part 13 is formed with a first engagement groove 14 including a front part 15, a transition part 16, and a rear part 17.
The front stage part 15 and the rear stage part 17 extend in directions orthogonal to the axis at different positions in the axial direction. Further, as shown in FIG. 2, the depth of the groove becomes shallower toward the front in the rotational direction as shown in FIG. 2, and the depth of the groove becomes shallower toward the rear in the rotational direction as shown in FIG. Become.
The transition part 16 connects the front stage part 15 and the rear stage part 17 while tilting so that the front in the rotational direction approaches the front stage part 15 and the rear in the rotational direction approaches the rear stage part 17 with respect to the direction orthogonal to the axis. ing.

Here, two electromagnetic actuators 401 and 402 corresponding to the first switching unit 13 and the second switching unit 23 are applied to the valve lift adjusting device 10.
The electromagnetic actuator 401 corresponding to the first switching unit 13 advances the restriction pin 601 in synchronization with the rotation timing of the camshaft 11 and engages the first engagement groove 14. As a result, the slider 21 moves toward the slider limiter 12 as the camshaft 11 rotates. On the other hand, the electromagnetic actuator 402 corresponding to the second switching unit 23 advances the regulation pin 602 in synchronization with the rotation timing of the camshaft 11 and engages the second engagement groove 24. As a result, the slider 21 moves to the slider limiter 22 side as the camshaft 11 rotates. This detailed operation will be described later.

  The first small lift cam 18 and the first large lift cam 19 are provided adjacent to each other near the center of the slider 21 in the axial direction with respect to the first switching portion 13. As shown in FIG. 2 and the like, the first small lift cam 18 and the first large lift cam 19 are eccentric to the outside with respect to the reference circle in one direction of rotation. Further, the first large lift cam 19 is formed so that the amount of eccentricity from the reference circle is larger than that of the first small lift cam 18.

  With respect to the first switching unit 13 described above, the second switching unit 23 is arranged symmetrically in FIG. The second small lift cam 28 and the second large lift cam 29 are provided adjacent to each other near the center of the slider 21 in the axial direction with respect to the second switching portion 23. The second small lift cam 28 and the second large lift cam 29 are offset in the same direction in the axial direction with respect to the first small lift cam 18 and the first large lift cam 19 and are eccentric in the rotational direction. The portions are arranged in a direction shifted by about 180 °.

The rollers 31 and 32 and the swing arms 33 and 34 correspond to the two sets of small lift cams 18 and 28 and the large lift cams 19 and 29, respectively. The rotational movement of the camshaft 11 is reciprocated by the intake valves 91 and 92. Convert to
The rollers 31 and 32 are interposed between the small lift cams 18 and 28 and the large lift cams 19 and 29 and the central portions of the swing arms 33 and 34.

  The swing arms 33 and 34 have one end abutting against the lash adjusters 35 and 36 and the other end abutting against the intake valves 91 and 92. The swing arms 33, 34 swing with the contact portions with the lash adjusters 35, 36 as fulcrums so that the other ends of the arms approach or separate from the intake valves 91, 92. The lash adjuster 35 corresponding to the swing arm 33 is shown in FIG. 2 and the like, and the lash adjuster 36 corresponding to the swing arm 34 is not shown.

Next, the operation of the valve lift adjusting device 10 will be described with reference to FIGS.
As shown in FIGS. 1 and 2, when the slider 21 is on the slider limiter 22 side, the roller 31 contacts the outer peripheral surface of the eccentric portion of the small lift cam 18 and pushes down the swing arm 33. As a result, the intake valve 91 of the cylinder head 90 is opened by a relatively small lift amount L1. Further, the roller 32 abuts on the outer peripheral surface of the eccentric portion of the small lift cam 28 at a phase shifted by about 180 ° from the roller 31 and pushes down the swing arm 34. As a result, the intake valve 92 is opened by the lift amount L1.
Hereinafter, this state of the valve lift adjusting device 10 is referred to as a “small lift state”. In contrast, a state in which the roller 31 is in contact with the outer peripheral surface of the eccentric portion of the large lift cam 19 is referred to as a “large lift state”.

In the small lift state, the restriction pin 601 of the electromagnetic actuator 401 is located immediately above the front stage portion 15 of the first engagement groove 14. Therefore, when shifting from the small lift state to the large lift state, the electromagnetic actuator 401 advances the restriction pin 601 at the timing when the rotational position of the camshaft 11 becomes the position shown in FIGS. Engage with the groove 14.
When the slider 21 rotates together with the camshaft 11 with the restriction pin 601 fitted in the first engagement groove 14, the position of the groove into which the restriction pin 601 is fitted moves from the front stage part 15 to the rear stage part 17 via the transition part 16. At the same time, the slider 21 moves toward the slider limiter 12 as indicated by an arrow A1 in FIG.

The position P1 of the cams 18 and 19 when the slider 21 rotates 90 ° from the position P0 shown in FIGS. 1 and 2 is shown by solid lines in FIGS. Further, the positions P2 and P3 of the cams 18 and 19 when the slider 21 is rotated 180 ° and 270 ° from the position P0 are indicated by broken lines in FIG. In the rotation range from the position P1 to the position P3, since the roller 31 is in contact with the outer peripheral surface of the reference circular portion of the cams 18 and 19, the intake valves 91 and 92 are kept closed.
Further, at the rotational position past the position P 3, the depth of the groove of the rear stage portion 17 becomes shallow, and the bottom wall of the rear stage portion 17 pushes back the restriction pin 601 of the electromagnetic actuator 401.

  Thereafter, as shown in FIGS. 5 and 6, at the position P <b> 4 where the slider 21 has rotated 360 ° from the position P <b> 0, the roller 31 comes into contact with the outer peripheral surface of the eccentric portion of the large lift cam 19 and pushes down the swing arm 33. . That is, the valve lift adjusting device 10 is in a large lift state. As a result, the intake valve 91 of the cylinder head 90 is opened by a relatively large lift amount L2. Further, the roller 32 abuts on the outer peripheral surface of the eccentric portion of the large lift cam 29 at a phase shifted by about 180 ° from the roller 31 and pushes down the swing arm 34. As a result, the intake valve 92 is opened by the lift amount L2.

In the large lift state, the restriction pin 602 of the electromagnetic actuator 402 is located immediately above the front portion 25 of the second engagement groove 24. Therefore, when shifting from the large lift state to the small lift state, the electromagnetic actuator 402 moves the restriction pin 602 forward at the timing when the rotational position of the camshaft 11 reaches the position shown in FIGS. Engage with the groove 24.
When the slider 21 rotates together with the camshaft 11 in a state where the restriction pin 602 is fitted in the second engagement groove 24, the position of the groove in which the restriction pin 602 is fitted is changed from the front stage part 25 to the rear stage part 27 via the transition part 26. At the same time, the slider 21 moves toward the slider limiter 22 as indicated by an arrow A2 in FIG.

As described above, the valve lift adjusting device 10 controls the operation of the electromagnetic actuators 401 and 402 in synchronization with the rotation timing of the camshaft 11, thereby changing the lift amount of the intake valves 91 and 92 to the lift amount L1 and the lift amount. It is possible to switch to either L2.
Specifically, the operating conditions can be appropriately improved by adjusting the valve lift amount according to the rotational speed and load of the internal combustion engine.

  Next, the detailed structure of the electromagnetic actuator which is the principal part of this invention is demonstrated with reference to FIGS. In the following description, the two electromagnetic actuators 401 and 402 are collectively referred to as “electromagnetic actuator 40”. Further, the regulation pins 601 and 602 of the two electromagnetic actuators 401 and 402 are collectively referred to as “regulation pins 60”.

As shown in FIGS. 7 and 10, the electromagnetic actuator 40 includes a permanent magnet 41, a coil 42, a rear stator 43, a front stator 44, a yoke 46, a holder 47, a plunger 50, a regulating pin 60, a sleeve 70, a spring 75, and the like. ing. These members are assembled coaxially with respect to a common central axis O.
The plunger 50 and the restriction pin 60 are integrally coupled, and reciprocate with respect to other members from the most retracted position shown in FIG. 7 to the most advanced position shown in FIG. Here, the last retracted position is “zero stroke”, the most advanced position is “full stroke”, and the advance distance from the last retracted position is indicated by a stroke (mm). In the following description, “forward direction” or “forward” corresponds to the downward direction of FIGS. 7 to 10, and “reverse direction” or “rearward” corresponds to the upward direction of FIGS. 7 to 10.

The permanent magnet 41 is fixed to the base end side of the restriction pin 60 with respect to the plunger 50, attracts the attracted surface 511 of the plunger 50 in the backward direction by the magnet attracting force, and attracts and holds it at the last retracted position.
The coil 42 is energized via a connector (not shown) to generate an electromagnetic force that attracts the plunger 50 in the forward direction.

  The rear stator 43 and the front stator 44 are made of a magnetic material and cover the axial end of the coil 42 and a part in the radial direction, respectively. Specifically, as shown in FIG. 8, the rear stator 43 includes a rear wall 431 that covers the rear end portion of the coil 42, and an inner wall 432 that covers the rear portion in the radial inner direction of the coil 42. The front stator 44 includes a front wall 441 that covers the front end portion of the coil 42 and an inner wall 442 that covers a front portion of the coil 42 in the radial inner direction. The open surface 433 of the inner wall 432 of the rear stator 43 and the open surface 443 of the inner wall 442 of the front stator 44 face each other in the axial direction, and a gap 45 is formed therebetween.

  The rear stator 43 and the front stator 44 slide the sliding portion 52 of the plunger 50 along the inner walls 432 and 442, and constitute a transmission path for the magnetic flux Φ generated by the coil 42 by energization. At this time, by forming the gap portion 45, the magnetic flux Φ flows from the rear stator 43 to the front stator 44 via the plunger 50.

The yoke 46 is formed of a magnetic material in a cylindrical shape and covers the radially outward direction of the coil 42. The yoke 46, together with the rear stator 43 and the front stator 44, constitutes a transmission path for the magnetic flux Φ generated by the coil 42 when energized.
A bottomed cylindrical holder 47 that houses the permanent magnet 41 is joined to the opening 461 at the rear of the yoke 46. The holder 47 is made of a magnetic material, and the side facing the attracted surface 511 of the plunger 50 is open.

  Specifically, as shown in FIG. 9, the opening side end surface 471 of the holder 47 protrudes toward the plunger 50 with respect to the end surface 411 of the permanent magnet 41. That is, when the attracted surface 511 of the flange portion 51 of the plunger 50 is attracted by the permanent magnet 41 and abuts against the opening-side end surface 471 of the holder 47, there is a gap between the end surface 411 of the permanent magnet 41 and the attracted surface 511. δ is formed.

The plunger 50 is made of a magnetic material and includes a large-diameter flange portion 51 formed at a rear end portion and a sliding portion 52 extending from the flange portion 51 to the front end portion with a constant diameter.
The attracted surface 511 on the permanent magnet 41 side of the flange portion 51 always receives the action of the magnet attracting force of the permanent magnet 41. The outer wall 521 of the sliding portion 52 slides along the inner walls of the rear stator 43 and the front stator 44. In the connecting hole 522 of the sliding portion 52, the connecting portion 61 of the restriction pin 60 is inserted, and the plunger 50 and the restriction pin 60 are integrally coupled. The abutting surface 621 of the spring insertion portion 62 of the regulation pin 60 abuts on the tip surface 523 of the sliding portion 52.

  Referring to FIG. 8 again, the axial position of the open surface 443 of the front stator 44 is provided so as to coincide with the axial position of the distal end surface 523 of the sliding portion 52 when the plunger 50 is at zero stroke. Here, the axial position “matches” is based on technical common sense in the technical field of electromagnetic actuators, for example, about several hundreds of micrometers to several millimeters due to chamfering of the edges of the open surface 443 and the tip surface 523. Including those adjusted by range.

As described above, the axial position of the distal end surface 523 and the open surface 443 at the time of the zero stroke of the plunger 50 substantially coincides, thereby minimizing the magnetic gap Gm shown in FIG. Therefore, the magnetic flux Φ generated by the coil 42 at the moment when energization is started from the time of de-energization flows most efficiently from the plunger 50 to the front stator 44 through the minimum magnetic gap Gm. Further, since the path area of the magnetic flux Φ is reduced, the magnetic flux density is increased. Therefore, the maximum electromagnetic force is obtained in the state shown in FIG.
Incidentally, when the plunger 50 moves forward as indicated by a broken line, the path area of the magnetic flux Φ increases due to the axial overlap of the plunger 50 and the front stator 44 with the advance, and the magnetic flux density decreases. Therefore, the electromagnetic force of the coil 42 decreases.

The restriction pin 60 is coaxially formed on the central axis O in this order from the base end side in the order of the connecting portion 61 connected to the plunger 50, the spring insertion portion 62 to which the spring 75 is externally inserted, the sliding portion 63, and the distal end portion 64. Has been.
The sliding portion 63 is slidable on the inner wall of the sliding hole 721 of the sleeve 70 at the outer wall 632. The step surface between the sliding portion 63 and the spring insertion portion 62 constitutes a spring seat surface 631 that supports the front end portion of the spring 75.
The distal end portion 64 is inserted into the insertion hole 722 of the sleeve 70 by the outer wall 641. The tip end face 643 is located on the same plane as the end face 723 of the sleeve 70 or slightly inward of the end face 723 when retracted last. Further, the tip end face 643 protrudes from the end face 723 of the sleeve 70 during advance, and engages with the engaging grooves 14 and 24 of the valve lift adjusting device 10.

The sleeve 70 includes a flange portion 71 and a main body portion 72.
The flange portion 71 has a radially outer wall joined to the opening 462 in front of the yoke 46. Further, a peripheral edge of the rear end surface of the flange portion 71 is in contact with the front wall 441 of the front stator 44, and a recess 711 for accommodating the spring pressing plate 76 is formed inside the peripheral edge.
In the main body 72, a sliding hole 721 that accommodates the sliding portion 63 of the restriction pin 60 and an insertion hole 722 into which the distal end portion 64 of the restriction pin 60 is inserted are formed coaxially on the central axis O.

The spring 75 is externally inserted into the spring insertion portion 62 of the restriction pin 60, and both ends are supported between the spring pressing plate 76 and the spring seat surface 631 of the restriction pin 60. The spring 75 biases the restriction pin 60 in the forward direction by the spring force.
The spring pressing plate 76 is accommodated in the concave portion 711 of the flange portion 71 of the sleeve 70 and supports the rear end portion of the spring 75.

Next, the operation of the electromagnetic actuator 40 having the above configuration will be described with reference to FIGS.
As shown in FIG. 11, the magnet attracting force Fm by the permanent magnet 41 and the spring force Fsp by the spring 75 act on the plunger 50 during non-energization.
The magnet attracting force Fm acts in the direction in which the plunger 50 is retracted, and is maximum at a stroke of 0 mm, and decreases as the stroke increases. For reference, according to Coulomb's law, the magnet attractive force Fm decreases in inverse proportion to the square of the stroke. The spring force Fsp acts in the direction in which the plunger 50 is moved forward, is maximum at a stroke of 0 mm, and decreases linearly as the stroke increases. Since the magnet attracting force Fm is set to exceed the spring force Fsp at a stroke of 0 mm, the plunger 50 is attracted and held by the permanent magnet 41.
As a result, the distal end portion 64 of the restriction pin 60 is accommodated inside the end surface 723 of the sleeve 70, and the engagement with the engagement grooves 14 and 24 is released in the valve lift adjusting device 10.

On the other hand, as shown in FIG. 12, during energization, in addition to the magnet attracting force Fm and the spring force Fsp, an electromagnetic force Fsol attracted in the forward direction acts on the plunger 50.
As described above, the maximum electromagnetic force Fsol is obtained at the moment when energization is started from the time of de-energization by the configuration in which the axial position of the opening surface 443 of the front stator 44 and the distal end surface 523 of the zero stroke is the same. can get. That is, the electromagnetic force Fsol is maximum at a stroke of 0 mm and decreases as the stroke increases.

The resultant force (Fsol + Fsp) of the electromagnetic force Fsol and the spring force Fsp is set to exceed the magnet attracting force Fm in the entire stroke range including the stroke of 0 mm. Therefore, the plunger 50 is peeled off from the permanent magnet 41 and moves forward to the full stroke Sf. Even if the electromagnetic force Fsol becomes zero or a value close to zero during the forward movement, the plunger 50 moves forward only with the spring force Fsp.
Thereby, the front end portion 64 of the restriction pin 60 protrudes from the end surface 723 of the sleeve 70 and engages with the engagement grooves 14 and 24 of the valve lift adjusting device 10. Then, the slider 21 is moved to a predetermined position by the rotation of the camshaft 11, and the valve lift amount is switched.

By rotating the switching portions 13 and 23 following the movement of the slider 21, the distal end portion 64 of the restriction pin 60 is pushed back, so that the plunger 50 moves backward from the full stroke Sf to a stroke area equal to or less than the threshold stroke St that can be returned.
In the region below the threshold stroke St, the magnet attracting force Fm exceeds the spring force Fsp, so that the plunger 50 is attracted in the backward direction until the attracted surface 511 contacts the opening side end surface 471 of the holder 47. At this time, since the gap δ is formed between the end surface 411 of the permanent magnet 41 and the attracted surface 511, the plunger 50 does not collide with the permanent magnet 41.

(effect)
The effect of the electromagnetic actuator 40 of this embodiment will be described.
(1) Since the permanent magnet 41 is fixed to the electromagnetic actuator 40 of the present embodiment, the permanent magnet is broken by an impact at the time of operation compared to the conventional electromagnetic actuator that operates the permanent magnet. As a result, the actuator operates. It can be prevented from becoming impossible.
(2) Since the holder 47 that houses the permanent magnet 41 is formed of a magnetic material, the magnetic leakage of the permanent magnet 41 can be suppressed and the magnet attracting force Fm can be increased. Further, if the permanent magnet 41 is broken, it is possible to prevent the shattered pieces from being scattered.

(3) The opening side end surface 471 of the holder 47 protrudes toward the plunger 50 with respect to the end surface 411 of the permanent magnet 41, and a gap δ is formed between the end surface 411 of the permanent magnet 41 and the attracted surface 511. Therefore, when the plunger 50 is attracted by the permanent magnet 41, the attracted surface 511 of the plunger 50 does not collide with the end surface 411 of the permanent magnet 41 and abuts against the opening side end surface 471 of the holder 47. Thereby, it is possible to prevent the permanent magnet 41 from being broken.
Moreover, since the plunger 50 does not contact the permanent magnet 41 directly, deterioration of the magnetic characteristics of the permanent magnet 41 can be suppressed.

  (4) The axial position of the open surface 443 of the front stator 44 is provided so as to coincide with the axial position of the distal end surface 523 when the plunger 50 is attracted to the permanent magnet 41. Therefore, as the plunger 50 moves forward, the magnetic flux density due to the overlap between the plunger 50 and the front stator 44 in the axial direction decreases, and the electromagnetic force Fsol of the coil 42 decreases. As a result, the electromagnetic force Fsol is maximized at a stroke of 0 mm where the plunger 50 needs to be separated against the magnet attracting force Fm at the start of operation, and thus the electromagnetic force Fsol can be generated efficiently. Therefore, the coil 42 can be reduced in size.

  (5) In the electromagnetic actuator 40 of this embodiment applied to the valve lift adjusting device 10, when the distal end portion 64 of the restriction pin 60 is separated from the engagement grooves 14 and 24, the restriction pin 60 is caused by the torque of the camshaft 11. Since it is pushed back, there is no need for drive means for retracting the regulating pin 60 from the most advanced position. Therefore, the physique can be made smaller than that of an electromagnetic actuator having two electromagnetic driving portions in both forward and backward directions, as described in, for example, Japanese Patent Application Laid-Open No. 7-335434.

(Other embodiments)
(A) The holder that houses the permanent magnet is not limited to a magnetic material, and may be formed of a nonmagnetic metal such as austenitic stainless steel or a resin.
(A) The opening side end surface of the holder is not limited to the configuration protruding to the plunger side with respect to the end surface of the permanent magnet, and may be formed on the same surface as the end surface of the permanent magnet, or may be recessed with respect to the end surface of the permanent magnet. May be formed.
(C) The axial position of the open surface of the front stator does not have to coincide with the axial position of the tip surface when the plunger is at the zero stroke.

(D) The valve lift adjusting device is not limited to the intake valve, and may adjust the lift amount of the exhaust valve.
(E) The configuration of the cam lift, slider, etc. of the valve lift adjustment device is not limited to that illustrated in the above embodiment, and any configuration can be used as long as it can be switched by forward and backward movement of the restriction pin of the electromagnetic actuator. May be.
As mentioned above, this invention is not limited to such embodiment, In the range which does not deviate from the meaning of invention, it can implement with a various form.

10: Valve lift adjusting device,
11 ... camshaft, 14, 24 ... engagement groove,
21 ... Slider,
40, 401, 402 ... electromagnetic actuator 41 ... permanent magnet,
42 ... Coil,
50 ... Plunger, 511 ... Adsorbed surface,
60, 601, 602 ... restriction pin, 64 ... tip part,
75 ・ ・ ・ Spring,
91, 92 ... Intake valves.

Claims (4)

The present invention is applied to a valve lift adjusting device (10) for adjusting the lift amount of an intake valve (91, 92) or an exhaust valve of an internal combustion engine, and rotates with the cam shaft (11) of the valve lift adjusting device with respect to the cam shaft. When the front end portion (64) of the restriction pin (60, 601, 602) is engaged with the engagement groove (14, 24) formed in the slider (21) relatively movable in the axial direction, the restriction pin is caused by electromagnetic force. An electromagnetic actuator (40, 401, 402) in which the restriction pin is pushed back by the torque of the cam shaft when the tip of the restriction pin is moved away from the engagement groove.
The restriction pin provided to be able to move forward with respect to the engagement groove;
A plunger (50) formed of a magnetic material and connected to one end of the restriction pin;
A permanent magnet (41) fixed to the base end side of the restriction pin with respect to the plunger, and attracting the attracted surface (511) of the plunger in the backward direction;
A coil (42) for generating an electromagnetic force for attracting the plunger in a forward direction by energization;
A spring (75) for urging the regulating pin in the forward direction;
An electromagnetic actuator comprising:   2. The electromagnetic actuator according to claim 1, further comprising a holder (47) formed of a magnetic material, opened to a side facing the attracted surface of the plunger, and housing the permanent magnet. 3.   The electromagnetic actuator according to claim 2, wherein an opening side end surface (471) of the holder protrudes toward the plunger side with respect to an end surface of the permanent magnet. It is made of a magnetic material, and is provided between the coil in the radial direction and the plunger and between the permanent magnet side and the restriction pin side in the axial direction via a gap (45), via the plunger A rear stator (43) for transmitting magnetic flux and a front stator (44),
The front stator is provided so that the axial position of the open surface facing the gap coincides with the axial position of the distal end surface of the plunger in a state where the plunger is attracted to the permanent magnet. The electromagnetic actuator as described in any one of Claims 1-3 characterized by the above-mentioned.

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