Abstract:
A disclosed vibration insulating mount is promptly disposed between a vibrating body and a mounting body. The mount comprises a fluid chamber filled with a fluid, an elastic support partly defining the fluid chamber and mounting the vibrating body, a movable member partly defining the fluid chamber and capable of being displaced so as to change a volume of the fluid chamber, a supporting member supporting the movable member, and an actuator opposed to the movable member and generating displacing force to displace the movable member. Here, thickness of an outer portion of the movable member is thinner than that of an inner portion of the movable member.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a vibration insulating mount which mounts a vibration object such as an engine on a mounting body such as a vehicle body while isolating vibration and particularly to a vibration insulating mount in which a fluid chamber accommodating fluid is defined by a elastic support disposed between the vibrating body and mounting body so as to change a volume of the fluid chamber actively, thereby reducing vibration transmission rate. 
     Japanese Patent Application Laid-Open No. H9-250590 (Japanese Patent Application No. H8-59219) discloses a vibration insulating mount having a fluid chamber accommodating fluid so as to change a volume of the fluid chamber actively. 
     SUMMARY OF THE INVENTION 
     A conventional vibration insulating mount which changes a volume of a fluid chamber actively utilizes a movable member capable of being displaced so as to change the volume of the fluid chamber. According to a consideration by the present inventors, due to physical characteristics of an actuator for displacing the movable member, it is often difficult to keep the movable member parallel to the actuator. As a consequence, the movable member comes into contact with its peripheral members. 
     As its countermeasure, it can be considered to simply reduce the size of the movable member so as to expand a gap relative to the peripheral parts. However, if the size of the movable member is reduced, the change in the volume of the fluid chamber is also decreased. This is not favorable for the vibration insulation characteristic of the vibration insulating mount. 
     Generally in some cases, an electromagnetic actuator is used to displace the movable member and a part of the movable member is constituted of a magnetic path forming member so that a magnetic force is applied to the movable member. With such a structure as well, it is needless to say that if the size of the magnetic path forming member is reduced, it is possible to prevent the movable member from coming into contact with the peripheral members. However, if the size of the magnetic path forming member is simply reduced, the degree of the change in magnetic flux in a space is also reduced, and therefore the magnetic force applied to the movable member is also reduced. Such reduction of the magnetic force applied leads to deterioration of the vibration insulation mounting characteristic, and therefore it is not favorable. 
     Accordingly, it becomes apparent that a vibration insulating mount having a desired characteristic cannot be achieved only by reducing the size of the movable member. 
     The present invention has been achieved by such a consideration by the present inventors, and an object of the present invention is to provide a vibration insulating mount capable of exerting an active vibration insulation mounting characteristic stably and securely while preventing a generation of the abnormal sound which may occur between the movable member and its peripheral components. 
     To achieve the above object, the present invention provides a vibration insulating mount to be disposed between a vibrating body and a mounting body, and comprising a fluid chamber filled with a fluid, an elastic support partly defining the fluid chamber and mounting the vibrating body, a movable member partly defining the fluid chamber and capable of being displaced so as to change a volume of the fluid chamber, a supporting member supporting the movable member, and an actuator opposed to the movable member and generating displacing force to displace the movable member. Here, thickness of an outer portion of the movable member is thinner than that of an inner portion of the movable member. 
     In other words, the vibration insulating mount of the present invention comprising fluid accommodating means accommodating a fluid, elastic mounting means mounting the vibrating body and partly defining the fluid accommodating means, volume changing means changing a volume of the fluid accommodating means and partly defining the fluid accommodating means, supporting means supporting the volume changing means, and reducing means reducing a frequency of contact between the volume changing means and the supporting means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a vehicle to which a vibration insulating mount according to a first embodiment of the present invention is applied; 
     FIG. 2 is a sectional view of the vibration insulating mount according to the first embodiment; 
     FIG. 3 is a partial sectional view showing a structure of an outer peripheral portion of a movable member of the vibration insulating mount of the first embodiment; 
     FIG. 4 is a partial sectional view showing a structure of the movable member when it is inclined of the vibration insulating mount of the first embodiment; 
     FIG. 5 is a partial sectional view showing a structure of the outer peripheral portion of the movable member of the vibration insulating mount of a second embodiment; 
     FIG. 6 is a partial sectional view showing a structure of a supporting ring of a vibration insulating mount according to a third embodiment of the present invention; and 
     FIG. 7 is a partial sectional view showing a structure of the supporting ring of the vibration insulating mount according to a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     First of all, a vibration insulating mount according to a first embodiment of the present invention will be described with reference to FIGS. 1-4. 
     As shown in FIG. 1, in a vehicle  10 , an engine (vibrating body)  17  is mounted to a vehicle body (mounting body)  18  constituted of suspension members or the like through a vibration insulating mount (active engine mount)  20  capable of generating a force so as to reduce vibration transmitted from the engine  17  to the vehicle body  18  (which will be referred to as “active mounting force ” hereinafter) in accordance with a drive signal. Actually, there are a plurality of engine mounts each of which generates passive mounting force depending on a relative displacement between the engine  17  and the vehicle body  18  in addition to the vibration insulating mount  20 , between the engine  17  and the vehicle body  18 . As the passive engine mount, for example, a normal engine mount for mounting a load with a rubber-like elastic body, a known fluid charging type mount insulator in which a fluid is charged inside of an elastic body such as a rubber so as to generate a damping force or the like are available. 
     FIG. 2 shows a structure of the vibration insulating mount  20 . A device case  43  contains mount parts such as an outside cylinder  34 , an orifice component  36 , an inside cylinder  37 , a elastic support  32  or the like. Below these mount parts, there are installed an electromagnetic actuator  52  which forms a part of partition wall of a main fluid chamber and displaces an elasticly mounted movable member in a direction in which a volume of the main fluid chamber is changed and a load sensor  64  which detects a vibration status of the vehicle body  18 . 
     Namely, the vibration insulating mount  20  of this embodiment contains an engine side connecting member  30  in which a connecting bolt  30   a  is fixed such that it faces upward. Below this engine side connecting member  30  is fixed a hallow cylinder body  30   b  having an inverse trapezoidal section. 
     On a lower side of the engine side connecting member  30  is fixed the elastic support  32  by vulcanized adhering by use of curing agent so as to cover the surfaces of the lower side of the engine side connecting member  30  and the hallow cylinder body  30   b . This elastic support  32  is a substantially cylindrical elastic body which is inclined gradually downward from its center portion toward its peripheral portion. A hallow portion  32   a  having a mountainous section is formed inside of the elastic support  32 . A thin-shaped bottom end portion of the elastic support  32  is fixed by vulcanized adhering by use of curing agent with an inside peripheral surface of the orifice component  36  in which an axis center P 1  (hereinafter referred to as mount axis) is coaxial with respect to the hallow cylinder body  30   b . Here, the mount axis P 1  is a central axis of the vibration insulating mount  20  and substantially corresponding to a vibrating body mounting direction (in this case, upward/downward direction in FIG.  2 ). 
     The orifice component  36  is a member in which a small-diameter cylinder portion  36   c  is formed continuously between a upper end cylinder portion  36   a  and a lower end cylinder portion  36   b  each having the same outside diameter so as to produce an annular concave portion on its outside surface. Although not shown, an opening portion is formed in the small-diameter cylinder portion  36   c  so that inside and outside of the orifice component  36  communicate with each other through this opening portion. 
     The outside cylinder  34  is fit to outside of the orifice component  36  and this outside cylinder  34  has the same inside diameter as the outside diameter of the upper end cylinder portion  36   a  and lower end cylinder portion  36   b  of the orifice component  36 . The length in the axial direction of the outside cylinder  34  is the same as that of the orifice component  36 . An opening portion  34   a  is formed in this outside cylinder  34 . An outside periphery of a diaphragm  42  constituted of rubber made thin film elastic body is adhered to an edge portion of the opening portion  34   a  so as to close the opening portion  34   a  such that the diaphragm  42  is bent inward of the outside cylinder  34 . 
     When the outside cylinder  34  having the above described structure is fit to outside of the orifice component  36  so as to surround the annular concave portion, an annular space is defined in the circumferential direction between the outside cylinder  34  and the orifice component  36  and then the diaphragm  42  is disposed in that annular space in a condition that it is bent as described above. 
     The inside cylinder  37  fit to inside of the orifice component  36  includes a smallest-diameter cylinder portion  37   a  formed to be smaller than the small-diameter cylinder portion  36   c  of the orifice component  36 , and annular portions  37   b  and  37   c  are formed at upper and lower end portions of the smallest-diameter cylinder portion  37   a  so as to be directed outward in the diameter direction. The annular portion  37   b  at the upper end is formed such that the outside diameter thereof is slightly smaller than the small-diameter cylinder portion  36   c  of the orifice component  36 . The annular portion  37   c  at the lower end is formed so as to be smaller than the lower end cylinder portion  36   b  of the orifice component  36 , and a second opening portion  37   d  is formed in the smallest-diameter cylinder portion  37   a.    
     As for the device case  43 , an upper end caulking portion  43   a  having a circular opening portion having a diameter smaller than the outside diameter of the upper end cylinder portion  36   a  is formed at its upper end portion, and its main body continuous from this upper end caulking portion  43   a  has a cylinder shape extended up to its bottom end opening portion so as to have the same inside diameter as the outside diameter of the outside cylinder  34  (a shape indicated by broken lines at the bottom end opening portion in FIG.  2 ). 
     Then, the outside cylinder  34  in which the elastic support  32 , the orifice component  36 , the inside cylinder  37  and the diaphragm  42  are integrated therewith is inserted into inside of the device case  43  from its bottom end opening portion and by making the upper end portion of the outside cylinder  34  and the orifice component  36  into contact with a bottom surface of the upper end caulking portion  43   a , they are disposed inside of the device case  43 . 
     An air chamber  42   c  is defined in a space surrounded by the inside surface of the device case  43  and diaphragm  42 . An air vent hole  43   a  is formed at a position facing this air chamber  42   c , and the air chamber  42   c  communicates with the atmosphere through this air vent hole  43   a.    
     A cylindrical spacer  70  is fit to a lower portion of the device case  43 , a movable member  78  is disposed at an upper portion of this spacer  70 , and an electromagnetic actuator  52  is disposed at a lower portion of the spacer  70 . 
     That is, the spacer  70  is a member in which a diaphragm  70   c  constituted of a rubber made thin film elastic body is fixed between an upper cylindrical body  70   a  and a lower cylindrical body  70   b  by vulcanized adhering. 
     The electromagnetic actuator  52  comprises a cylindrical yoke  52   a , a circular excitation coil  52   b  embedded at the side of an upper end surface of the yoke  52  and a permanent magnet  52   c  fixed to a upper center portion of the yoke  52   a  such that its poles are directed up and down. The aforementioned yoke  52   a  comprises an upper yoke member  53   a  and a lower yoke member  53   b , which are two divisions thereof in the vertical direction in FIG.  2 . Then, a lower circumference of the upper yoke member  53   a  and a upper circumference of the lower yoke member  53   b  are ground off so as to form a concave portion  52   d  continuous in its circumferential direction. Then, a diaphragm  70   c  of the spacer  70  is bent toward the aforementioned concave portion  52   d . An air chamber  70   d  is defined in a space surrounded by an inner surface of the device case  43  and the diaphragm  70   c , and an air vent hole  43   b  is formed at a position facing this air chamber  70   d  so that the air chamber  70   d  communicates with the atmosphere thorough this air vent hole  43   b . A load sensor  64  is disposed between the bottom surface of the yoke  52   a  and a lid member  62  provided with vehicle side connecting bolts  60  so as to detect a residual vibration necessary for control to reduce vibration. Although as the load sensor  64 , a piezoelectric element, magnetostrictor, strain gauge and the like are available, the piezoelectric element is used in this embodiment. A detection result of this sensor is supplied to a controller  25  as a residual vibration signal “e” as shown in FIG.  1 . 
     On the other hand, a seal ring  72  for fixing a sealing member, a supporting ring  74  as a retainer having a spring supporting portion  74   a  formed along its inner peripheral surface so as to be projected inward for supporting a peripheral portion of a leaf spring  82  described later from down as a free end, and a gap holding ring  76  for setting a gap H between a yoke  52   a  of the electromagnetic actuator  52  and the movable member  78  are disposed coaxially with the mount axis P i , and the movable member  78  is disposed within these rings such that it is displaceable in a vertical direction. 
     The movable member  78  comprises a partition wall forming member  78 A formed in circular shape and a magnetic path forming member  78 B formed in circular shape having a larger diameter than that of the partition wall forming member  78 A. A bolt hole  80   a  is formed in the axis of the partition wall forming member  78 A located at a far side with respect to the electromagnetic actuator  52 . A movable member bolt  80  passes through the magnetic path forming member  78 B located at a near side with respect to the electromagnetic actuator  52  and is screwed with the bolt hole  80   a , so that the partition wall forming member  78 A and magnetic path forming member  78 B are integrated with each other. 
     A constricted portion  79  which is continuous like a ring (viz., an annular void or gap) is defined between the partition wall forming member  78 A and the magnetic path forming member  78 B. A leaf spring  82  which is an elastic member for supporting the movable member  78  elastically is accommodated in this constricted portion  79 . That is, the leaf spring  82  is a disc-shaped member in which a hole is formed in the center thereof. An inner peripheral portion of this leaf spring  82  supports a center portion of the bottom side of the partition wall forming member  78 A from lower side of the partition wall forming member  78 A through a free end. An outer peripheral portion of the leaf spring  82  is supported by the spring supporting portion  74   a  of the supporting ring  74  from a lower side of the leaf spring  82  through a free end. Consequently, the movable member  78  is elastically supported by the device case  43  through the leaf spring  82 . 
     In the partition wall forming member  78 A, a partition wall portion  80   c , which is thin and faces a fluid chamber  84 , and an annular rib  80   b  which protrudes upward from an outer periphery of the partition wall portion  80   c  are formed. Then, the fluid chamber  84  is formed by a top face of the partition wall forming member  78 , a bottom face of the elastic support  32  and an inside peripheral surface of the inside cylinder  37  so that fluid is contained in this fluid chamber  84 . To prevent a leakage of the fluid from the fluid chamber  84  to the side of the constricted portion  79  accommodating the leaf spring  82 , a sealing member  86  is provided between an outer periphery of the partition wall forming member  78 A and an inner periphery of the seal ring  72 . The aforementioned sealing member  86  is constituted of a ring-like or annular rubber elastic member and its elastic deformation allows the movable member  78  to be displaced vertically relative to the seal ring  72  and the device case  43  in FIG.  2 . 
     As shown in FIG. 3, a thin annular portion  78 B 1  having a smaller thickness than the magnetic path forming member  78 B is formed on an outer peripheral portion of the magnetic path forming member  78 B such that it is projected outward in the diameter direction. Upper and lower faces of this thin annular portion  78 B 1  are disposed so as to oppose each other so that they are located between the spring supporting portion  74   a  of the supporting ring  74  and the yoke  52   a  of the electromagnetic actuator  52 . It is so constructed that a thick portion of the magnetic path forming member  78 B does not overlap the spring supporting portion  74   a  in a perpendicular direction (vertical direction in the Figure), so that if the movable member  78  moves largely upward in the Figure, the thin annular portion  78 B, comes into contact with the leaf supporting portion  74   a.    
     A stopper member  78 C which is made of a ring-like, rubber-like elastic body for preventing a direct contact with the spring supporting portion  74   a  and yoke  52   a  when the movable member  78  moves excessively is fixed to the aforementioned thin annular portion  78 B 1  in a condition that it covers upper and lower faces of the thin annular portion  78 B 1  and an outer peripheral end of the thin annular portion  78 B 1 . 
     In this embodiment, an inner periphery around the hole of the leaf spring  82  is the nearest the magnetic path forming member  78 B. If a distance at a position where the leaf spring  82  is the nearest the magnetic path forming member  78 B is S (see FIG.  3 ), a distance hi between the upper face of the aforementioned stopper member  78 C and the spring supporting portion  74   a  of the supporting ring  74  when the electromagnetic actuator  52  is not activated, that is, the movable member  78  is attracted by only magnetic force of the permanent magnet  52   c  is set so as to be smaller than the aforementioned distance S (h 1 &lt;S). 
     Further, if a gap between a bottom face of the magnetic path forming member  78 B and the yoke  52   a  of the electromagnetic actuator  52   a  is H, a gap h 3  between a bottom face of the stopper member  78 C and the yoke  52   a  of the electromagnetic actuator  52  is set so as to be smaller than the gap H (h 3 &lt;H), so that the stopper member  78 C is nearer the yoke  52   a  than the bottom face of the magnetic path forming member  78 B. 
     In the mean time, the excitation coil  52   b  of the electromagnetic actuator  52  generates a predetermined electromagnetic force depending on a driving signal “y” which is a current supplied from the controller  25  shown in FIG.  1 . The controller  25  comprises a microcomputer, necessary interface circuit, A/D converter, D/A converter, amplifier, memory medium such as ROM and RAM or the like, and generates and outputs the driving signal “y” to the vibration insulating mount  20  so as to produce an active mounting force in the vibration insulating mount  20  for reducing the vibration generated by the engine  17 . 
     In the case of reciprocating 4-cylinder, 4-cycle engine, for example, the idling vibration or the indistinct sound vibration generated from the engine  17  are produced mainly because engine vibration which is a so-called engine revolution secondary component is transmitted to the vehicle body  18 . Thus, if the driving signal “y” is produced synchronously with that engine revolution secondary component, the vibration of the vehicle body  18  can be reduced. Therefore, according to this embodiment, a pulse signal generator  19  which produces an impulse signal synchronously with a rotation of a crank shaft of the engine  17  (e.g., in the case of the reciprocating 4-cylinder engine, an impulse signal is produced every rotation by 180° of the crank shaft) and outputs as a reference signal “x” is provided, and that reference signal “x” is supplied to the controller  25 . 
     The controller  25  executes so-called synchronous Filtered XLMS algorithm which is a sequentially renewal-type adaptive algorithm based on the residual vibration signal “e” and reference signal “x” so as to calculate the driving signal “y” to the vibration insulating mount  20  and output that driving signal “y” to the vibration insulating mount  20 . 
     Speaking concretely, the controller  25  has an adaptive digital filter W capable of varying a filter coefficient W i  (i=0, 1, 2, . . . , I−1: I is tap number) and, from the time when a current reference signal “x” is input, the controller  25  outputs the filter coefficient W i  of the adaptive digital filter W at a predetermined sampling clock interval as the driving signal “y”. On the other hand, the controller  25  executes a processing for renewing the filter coefficient W i  of the adaptive digital filter W based on the reference signal “x” and residual vibration signal “e”. 
     The renewal formula of the adaptive digital filter W is expressed in the form of an formula based on the Filtered-X LMS algorithm. 
     
       
           W   i ( n+ 1)= W   i ( n )−μ R   T   e ( n ) 
       
     
     Wherein, terms with (n), (n+1) respectively indicate values at the time of sampling time n, n+1, and μ is a convergence coefficient. Further, theoretically, the renewing reference signal R T  is a value obtained by filter processing with respect to the reference signal “x” with a transmission function filter C{circumflex over ( )} which is obtained by modeling a transmission function C between the electromagnetic actuator  52  and the load sensor  64  of the vibration insulating mount  20  by use of a finite impulse response-type filter. Since the magnitude of the reference signal “x” is “1”, the value of the renewing reference signal R T  coincides with a sum of the impulse response waveforms at the sampling time n when the impulse response of the transmission function filter C{circumflex over ( )} is generated in sequential synchronously with the reference signal “x”. Although, theoretically, the reference signal “x” is filtered with the adaptive digital filter W so as to generate the driving signal “y”, since the magnitude of the reference signal “x” is “1”, even if the filter coefficient W i  is output in sequential as the driving signal “y”, the same result is obtained as when the result of the filtering processing is used as the driving signal “y”. 
     Next, an operation of the vibration insulating mount of this embodiment will be described. 
     That is, in a condition in which the idling vibration or the indistinct sound vibration is generated from the engine  17 , the filter coefficient W i  of the adaptive digital filter W is supplied in sequential as the driving signal “y” to the electromagnetic actuator  52  of the vibration insulating mount  20  from the controller  25 , at the predetermined sampling clock interval from the time when the reference signal “x” is input. 
     As a result, a magnetic force is generated in the excitation coil  52   c  corresponding to the driving signal “y”. Then, it can be considered that that magnetic force from the excitation coil  52   c  strengthens or weakens the magnetic force of the permanent magnet  52   c  because the magnetic path forming member  78 B has been already applied with a certain level of the magnetic force by the permanent magnet  52   c . That is, when no driving signal “y” is supplied to the excitation coil  52   b , the movable member  78  including the magnetic path forming member  78 B is displaced at a position in which a supporting force of the leaf spring  82  is balanced with the magnetic force of the permanent magnet  52   c . Then, when the driving signal “y” is supplied to the excitation coil  52   b  in this neutral state and the magnetic force generated in the excitation coil  52   b  by the driving signal “y” is opposite to the magnetic force of the permanent magnet  52   c , the movable member  78  is displaced in a direction in which the gap relative to the electromagnetic actuator  52  is increased. On the contrary, if the magnetic force generated in the excitation coil  52   b  is in the same direction as the magnetic force of the permanent magnet  52   c , the movable member  78  is displaced in a direction in which the gap relative to the electromagnetic actuator  52  is decreased. 
     As described above, the movable member  78  can be displaced in both ways. If the movable member  78  is displaced, the partition wall forming member  78 A forming a part of the partition wall of the fluid chamber  84  is also displaced, so that the volume of the fluid chamber  84  is changed. Due to the change of the volume, the so-called expansion spring of the elastic support  32  is changed. Thus, the active mounting force in both positive and negative directions is generated in the vibration insulating mount  20 . 
     Because the magnetic path forming member  78 B for receiving magnetic force is extended in the diameter direction thereof to such an extent that the magnetic path forming member  78 B does not come into contact with anything when it moves upward and the thin annular portion  78 B 1  is projected in the diameter direction thereof, the entire surface area of the magnetic path forming member  78 B can be increased. Further, because the thickness of the thin annular portion  78 B 1  is smaller than the thickness of the magnetic path forming member  78 B, the movable member  78  does not come into contact with the supporting ring  74  when the movable member  78  moves at an ordinary stroke. Each filter coefficient W i  of the adaptive digital filter Which generates the driving signal “y” is renewed sequentially according to the aforementioned formula based on the synchronous Filtered-X LMS algorithm. Therefore, after a certain time has been passed and each filter coefficient W i  of the adaptive digital filter W is converged to an optimum value, by supplying the driving signal “y” to the vibration insulating mount  20 , the idling vibration or the indistinct sound vibration which is transmitted from the engine  17  to the vehicle body  18  through the vibration insulating mount  20  is reduced. 
     Thereupon, FIG. 4 shows a case in which when the movable member  78  is attracted by the electromagnetic actuator  52 , the movable member  78  is largely inclined because of inequality of electromagnetic force in the circumferential direction and/or inequality of spring constant of the leaf spring  82  in the circumferential direction. 
     At this time, a top inclined portion (right edge portion of the movable member  78  in FIG. 4) of the outer peripheral portion of the movable member  78  comes near a bottom face of the spring supporting portion  74   a  of the supporting ring  74 . Because in this embodiment, there is provided a large distance between the thin annular portion  78 B 1  projected in the convex shape outward in the diameter direction from the outer peripheral portion of the magnetic path forming member  78 B and the spring supporting portion  74   a , the frequency of contact between the magnetic path forming member  78 B and spring supporting portion  74   a  can be reduced. When the magnetic path forming member  78 B comes into contact with the spring supporting portion  74   a , no abnormal sound is generated because the stopper member  78 C fixed around the thin annular portion  78 B 1  exists between the thin annular portion  78 B 1  and the spring supporting portion  74   a.    
     A bottom inclined portion (left edge portion of the movable member  78  in FIG. 4) of the outer peripheral portion of the movable member  78  comes near the top face of the yoke  52   a . Because a large gap is defined between the thin annular portion  78 B 1  of the magnetic path forming material  78 B and yoke  52   a , the frequency of contact between the magnetic path forming member  78 B and yoke  52   a  can be reduced. When the magnetic path forming member  78  comes into contact with the yoke  52   a , no abnormal sound is generated because the stopper member  78 C fixed around the thin annular portion  78 B 1  exists between the thin annular portion  78 B 1  and yoke  52   a.    
     When the magnetic path forming member  78 B is inclined, there is a fear that, as shown by the symbol A in FIG. 4, the leaf spring  82  may come into contact with the top face of the magnetic path forming member  78 B and an abnormal sound may be generated. However, according to this embodiment, because the distance h, between the top face of the stopper member  78 C and the spring supporting portion  74   a  of the supporting ring  74  is set so as to be smaller than the distance S between the leaf spring  82  and the magnetic path forming member  78 B when they are nearest each other (h 1 &lt;S), the stopper member  78 C comes into contact with the spring supporting portion  74   a  first thereby preventing the leaf spring  82  from coming into contacting with the top face of the magnetic path forming member  78 B so as to prevent a generation of the abnormal sound. 
     If an internal pressure of the fluid chamber  84  changes largely so that the movable member  78  moves excessively in the vertical direction, the thin annular portion  78 B 1  and the spring supporting portion  74   a  of the supporting ring  74   a  act as a stopper so as to inhibit further movement of the movable member  78 . Thus, it is possible to avoid a problem that the rib  80   b  collides with the internal cylinder  37  to produce a damage. 
     According to this embodiment, even if the diameter of the magnetic path forming member  78 B is not reduced and the entire thickness thereof is not reduced, a direct contact of the magnetic path forming member  78 B relative to the spring supporting portion  74   a  of the supporting ring  74  and the top face of the yoke  52   a  can be prevented. Therefore, it is possible to provide a vibration insulating mount  20  in which a generation force of the electromagnetic actuator  52  is not reduced and having a stable vibration insulation characteristic. 
     Because the stopper member  78 C made of rubber like elastic body according to this embodiment is fixed around the periphery of the thin annular portion  78 B 1  projected in the convex shape outward in the diameter direction, the stopper member  78 C is formed in such a manner that the volume of its upper portion which may be in contact with the spring supporting portion  74   a  of the supporting ring  74  and the volume of its lower portion which may be in contact with the top face of the yoke  52   a  are efficiently increased. As a result, if the spring supporting portion  74   a  and the yoke  52   a  comes into contact with the stopper member  78 C repeatedly, this portion having the increased volume of the stopper member  78 C is capable of keeping its elastic deformation for a long time, so that the durability and wear resistance of the stopper member  78 C are efficiently improved. 
     Because the stopper member  78 C is fixed continuously from its upper portion to its lower portion just as if it wraps entirely the thin annular portion  78 B 1 , the fixing force of the stopper member  78 C with respect to the magnetic path forming member  78 B is increased. 
     Although according to this embodiment, the thin annular portion  78 B 1  is formed in a step shape so that it is projected outward, it may be structured in such a manner that the thickness is gradually reduced linearly from inside to outside, that is a tapered shape is formed. 
     Next, a vibration insulating mount according to a second embodiment of the present invention will be described with reference to FIG.  5 . 
     The vibration insulating mount according to this embodiment basically has the same structure as the first embodiment except that the structure of the magnetic path forming member is different. Thus, the same reference numerals are attached to the same components and a description on the same structure and processing is omitted. 
     As shown in FIG. 5, the outer peripheral portion of the magnetic path forming member  78 B of this embodiment is formed as a thin annular portion  78 B 2  which is gradually thinned outward in the diameter direction while curved. The upper and lower curved faces of this thin annular portion  78 B 2  respectively oppose the spring supporting portion  74   a  of the supporting ring  74  and the yoke  52   a  of the electromagnetic actuator  52  with a large gap. A stopper member  78 C, made of ring-like, rubber-like elastic body is fixed to the aforementioned thin annular portion  78 B 2  in a condition that it covers the upper and lower curved faces of the thin annular portion  78 B 2  in order to prevent a direct contact of the thin annular portion  78 B 2  with the spring supporting portion  74   a  and yoke  52   a.    
     If a gap between the leaf spring  82  and magnetic path forming member  78 B when they are the nearest each other is assumed to be S in this embodiment, a distance h 4  between the upper face of the stopper member  78 C 1  and spring supporting portion  74   a  of the supporting ring  74  is set to a value smaller than the aforementioned distance S (h 4 &lt;S). A gap h 5  between the lower face of the stopper member  78 C 1  and yoke  52   a  of the electromagnetic actuator  52  is set to be value smaller than a gap H between the lower face of the magnetic path forming member  78 B and yoke  52   a  of the electromagnetic actuator  52  (h 5 &lt;H), so that the stopper member  78 C 1  is nearer the yoke  52   a  than the lower face of the magnetic path forming member  78 B is. 
     Even if the movable member  78  having the magnetic path forming member  78 B of the aforementioned structure is inclined, because the thin annular portion  78 B 2  which is gradually thinned outward in the diameter direction while curved defines a large gap relative to the spring supporting portion  74   a , the frequency of a contact between the magnetic path forming member  78 B and spring supporting portion  74   a  can be reduced. If the magnetic path forming member  78 B comes into contact with the spring supporting portion  74   a , no abnormal sound is produced because the stopper member  78 C 1  fixed around the thin annular portion  78 B 2  (upper and lower faces, and outer peripheral end face) exists between the thin annular portion  78 B 2  and spring supporting portion  74   a . Further, because there is a large gap defined between the thin annular portion  78 B 2  and yoke  52   a , the frequency of the contact between the magnetic path forming member  78 B and yoke  52   a  can be reduced. If the magnetic path forming member  78 B comes into contact with the yoke  52   a , no abnormal sound is produced because the stopper member  78 C 1  fixed around the thin annular portion  78 B 2  exists between the thin annular portion  78 B 2  and yoke  52   a . Further, in this embodiment, the distance h 4  between the upper face of the stopper member  78 C 1  and spring supporting portion  74   a  of the supporting ring  74  is set to be a value smaller than the distance S between the leaf spring  82  and magnetic path forming member  78 B when the leaf spring  82  is the nearest the magnetic path forming member  78 B (h 4 &lt;S), so that the stopper member  78 C 1  comes into contact with the spring supporting portion  74   a  so as to prevent a contact between the leaf spring  82  and magnetic path forming member  78 B, and therefore a generation of the abnormal sound is prevented. 
     As described above, according to this embodiment, it is possible to prevent a direct contact of the magnetic path forming member  78 B with the spring supporting portion  74   a  of the supporting ring  74  and upper face of the yoke  52   a , even if the diameter of the magnetic path forming member  78 B is not reduced and the entire thickness of the magnetic path forming member  78 B is not reduced, like the first embodiment. Thus, in this embodiment also, it is possible to provide a vibration insulating mount  20  in which a generation force of the electromagnetic actuator  52  is not reduced and having a stable vibration insulation control characteristic. 
     Next, a vibration insulating mount according to a third embodiment of the present invention will be described with reference to FIG.  6 . 
     The vibration insulating mount of this embodiment basically has the same structure as the first embodiment except that the structure of the supporting ring is different from the first embodiment. Thus, the same reference numerals are attached to the same components and processing, and a description thereof is omitted. 
     As shown in FIG. 6, in the supporting ring  88  of this embodiment, a spring supporting portion  88   a  formed to be projected in a convex shape from the inner peripheral portion supports the outer peripheral portion of the leaf spring  82  through its upper face as a free end from below and the lower face of the spring supporting portion  88   a  is formed as an inclined face  88   b  which gradually departs from the outer peripheral portion of the magnetic path forming member  78 B as the inclined face  88   b  goes inward in the diameter direction. 
     The distance between the thin annular portion  78 B 1  and inclined face  88   b  is further increased because of the provision of the supporting ring  88  having the above structure. Thus, even if the movable member  78  is inclined and displaced, the frequency of the contact between the magnetic path forming member  78 B and spring supporting portion  88   a  is further reduced. The inclined surface  88   b  and the thin annular portion  78 B 1 , can be, due to the space therebetween which is self-evident from FIG. 6, taken as defining a part of a means for reducing the frequency of contact between the magnetic path forming member and the spring support portion  74   a . Therefore, it is possible to provide a vibration insulating mount which prevents the abnormal sound which may be produced between the spring supporting portion  88   a  of the supporting ring  88  and magnetic path forming member  78 B and has a stable vibration insulation control characteristic without reducing a generation force of the electromagnetic actuator  52 . 
     Although in this embodiment, the distance between the thin annular portion  78 B 1  and magnetic path forming member  78 B is increased by the linear inclined face  88   b , it is permissible to use a stepped face instead of the linear face. 
     Next, a vibration insulating mount according to a fourth embodiment of the present invention will be described with reference to FIG.  7 . 
     The vibration insulating mount of this embodiment basically has the same structure as the first embodiment except that the structure of the supporting ring is different from the first embodiment. Thus, the same reference numerals are attached to the same components and processing, and a description thereof is omitted. 
     As shown in FIG. 7, in the supporting ring  90  of this embodiment, a spring supporting portion  90   a  formed to be projected in a convex shape from the inner peripheral portion supports the outer peripheral portion of the leaf spring  82  through its upper face as a free end from below and the lower face of the spring supporting portion  90   a  is formed as a curved face  90   b  which is curved in a convex shape at a predetermined curvature radius R 1  toward the magnetic path forming member  78 B. 
     The distance between the thin annular portion  78 B 1  and curved face  90   b  is increased because of the provision of the supporting ring  90  having such a structure and thus becomes part of an arrangement which includes the thin annular portion  78 B 1 , and which can, due to the clearance which is self-evident in FIG. 7, be considered as part of a means for reducing the frequency of contact between the magnetic path forming member and the supporting portion  90   a  even if the movable member  78  is inclined and displaced, the frequency of the contact between the magnetic path forming member  78 B and spring supporting portion  90   a  is further reduced. Therefore, it is possible to provide a vibration insulating mount  20  which prevents the abnormal sound which may be produced between the spring supporting portion  90   a  of the supporting ring  90  and magnetic path forming member  78 B and has a stable vibration insulation control characteristic without reducing a generation force of the electromagnetic actuator  52 . 
     Further, the contact face pressure in the stopper member  78 C which comes into contact with the curved face  90   b  of the spring supporting portion  90   a  is reduced as compared to the other embodiments. Thus, the durability and wear resistance of the stopper member  78  are further improved. 
     The vibration insulating mount according to the respective embodiments described above are not restricted to their application to a vehicle, and the present invention can be applied to another apparatus for reducing a vibration generated by the elements other than the engine  17 . Regardless of the object to which be the present invention is applied , the same operation and effect as the respective embodiments described above can be achieved. For example, the present invention can be applied to a vibration insulating mount for reducing a vibration transmitted from a machine tool to a floor or a room. 
     Although in the respective embodiments above, the synchronous Filtered-X LMS algorithm is used as an algorithm for generating the driving signal “y”, the applicable algorithm is not restricted to this one, but for example, ordinary Filtered-X LMS algorithm or the like can be used instead. 
     It is needless to say that the structure of the first or the second embodiment and the third or fourth embodiment are possible to be correspondingly combined. 
     The entire contents of a Patent Application No. TOKUGANHEI 10-55254, with a filling date of Mar. 6, 1998 in Japan, are hereby incorporated by reference. 
     Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the teachings. The scope of the invention is defined with reference to the following claims.