Patent Publication Number: US-2009224445-A1

Title: Liquid Filled Type Vibration Isolator

Description:
TECHNICAL FIELD 
     The present invention relates to a liquid filled type vibration isolator. 
     BACKGROUND ART 
     A known liquid filled type vibration isolator includes: a first attachment member, a cylindrical second attachment member, and a vibration isolating base made of rubber-like elastic material for connecting the first attachment member and the second attachment member; a diaphragm formed by a rubber film and attached to the second attachment member to provide a liquid filled chamber between the vibration isolating base and the diaphragm; a partitioning member for partitioning the liquid filled chamber into a first liquid chamber on the vibration isolating base side and a second liquid chamber on the diaphragm side; and an orifice connecting the first liquid chamber and the second liquid chamber so that the first and second liquid chambers can communicate with each other, as disclosed in the following Patent Reference Nos. 1 and 2, for example. In this liquid filled type vibration isolator, a first outer periphery of the diaphragm is bonded to at least an inner periphery of an annular attachment plate by vulcanization, and a second outer periphery of the attachment plate is fixed to an inner circumference of the second attachment member. According to these references, the partitioning member has an annular orifice forming member for forming the orifice, and a rubber wall for closing the inside of the inner circumference of the orifice forming member. 
     According to the following Patent Reference No. 3, the partitioning member has an elastic partitioning film, an annular orifice forming member for accommodating the elastic partitioning film, and first grid member and second grid member for regulating displacement of the elastic partitioning film from both sides of the film surface. The orifice forming member accommodating the elastic partitioning film is sandwiched between a receiving step formed on the vibration isolating base and a ring-disk-shaped metal pinching member (referred to as “partitioning plate lower metal fitting”) to be fixed therebetween. The outer periphery of the pinching member is caulked to the inner circumference of the second attachment member. The pinching member in the pinching condition is superposed on a metal attachment plate on the outer periphery of the diaphragm from above, and the attachment plate is superposed on a flange disposed at the upper end of a cup-shaped bottom metal fitting of the second attachment member from above. 
     According to the liquid filled vibration isolator disclosed in Patent Reference No. 3, at the time of generation of low-frequency vibration having large amplitude, liquid flows between the first and second liquid chambers through the orifice to produce liquid. flow effect which decreases the vibration. At the time of generation of high-frequency vibration having small amplitude, the elastic partitioning film reciprocatively deforms to absorb liquid pressure in the first liquid chamber and thereby decreases the vibration. According to the structure disclosed in this reference, impact caused by collision of the elastic partitioning film with the first and second grid members is transmitted to the bottom metal fitting via the pinching member and the attachment plate both made of metal. This impact is further transmitted to the vehicle body, causing abnormal noise in the vehicle cabin. 
     For overcoming this problem, reduction of the clearance between the elastic partitioning film and the first and second grid members is considered. In this case, however, the dynamic spring constant in the high frequency range becomes large, and thus desired vibration isolating capability is difficult to be achieved. 
     According to this type of liquid filled type vibration isolator, therefore, it is needed that the reciprocatively deformable component provided on the partitioning member is easily displaced for high-frequency vibration having small amplitude, and that the displacement of the reciprocatively deformable component is regulated as much as possible for input of vibration having large amplitude so as to obtain the liquid flow effect produced by the orifice. In addition, it is desired that the impact produced by the collision of the reciprocatively deformable component with the members for regulating the displacement of the reciprocatively deformable component is not transmitted to the vehicle cabin. However, these requirements are not sufficiently satisfied by the known liquid filled type vibration isolators. 
     According to the following Patent Reference No. 4, a rubber wall is provided on an opening formed in the central area of the partitioning member main body. A pair of displacement regulating members for regulating the elastic deformation of the rubber wall are provided on both sides of the film surface of the rubber wall. The pair of the displacement regulating members are connected with each other via a connecting member penetrating through the central area of the rubber wall. According to this reference, since the rubber wall is attached to the opening formed in the central area of the partitioning member main body on the lower surface of which the diaphragm is overlapped, the lower displacement regulating member of the two displacement regulating members is disposed facing not the liquid chamber but an air chamber. In this structure, therefore, vibration of the rubber wall caused by liquid pressure fluctuations in the first liquid chamber positioned on the upper side is not sufficiently transmitted to the second liquid chamber positioned on the lower side, that is, the vibration of the first liquid chamber is only released to the air chamber. Thus, the spring constant at the time of high-frequency vibration is not sufficiently decreased. 
     According to the structure disclosed in Patent Reference No. 4, the displacement of the rubber wall caused at the time of input of vibration having large amplitude is regulated by the pair of the displacement regulating members which extend over the opening edge of the partitioning member main body to the outside. Thus, at the time of input of vibration having large amplitude, the displacement regulating members contact the partitioning member main body in the axial direction via the edge of the rubber wall, and the rubber is compressed between the displacement regulating members and the partitioning member main body. As a result, the spring constant rapidly increases. In this case, the input given from the displacement regulating members to the partitioning member main body is large, which possibly results in generation of abnormal noise. 
     The following Patent Reference No. 5 discloses a “releasing device assembly” including a pair of upper and lower plate members and a connecting member for connecting these plate members provided in the central area of the partitioning member. However, the partitioning member equipped with the releasing device assembly does not have the rubber wall. More specifically, the releasing device assembly is disposed on the opening in the central area of the partitioning member made of rigid material such that the releasing device can freely slide, and the structure of the pair of the partitioning plates provided in the central area of the rubber wall for pinching the rubber wall in the axial direction is not disclosed in this reference. 
     An automobile engine mount disclosed in the following Patent Reference No. 6 includes a rubber bellows which has two convexes and constitutes an air spring. An intermediate ring for adding weight is supported between the convexes. The inside of the rubber bellows is divided into two chambers by a pair of fixing plates which pinch an inward flange of the intermediate ring. However, the rubber portion pinched by the pair of the fixing plates does not correspond to the rubber wall closing the inside of the inner circumferential surface of the ring-shaped component. Thus, this structure does not decrease high-frequency vibration by the reciprocatative deformation of the rubber portion. Accordingly, the structure of the pair of the partitioning plates provided in the central area of the rubber wall in the axial direction for pinching the rubber wall is not disclosed in this reference similarly to the above case. 
     Patent Reference No. 1: JP-A-2002-310224 
     Patent Reference No. 2: JP-A-2001-027278 
     Patent Reference No. 3: JP-A-2004-316895 
     Patent Reference No. 4: GB 2,332,498 A 
     Patent Reference No. 5: JP-UM-A-03-062244 
     Patent Reference No. 6: JP-A-57-26015 
     DISCLOSURE OF THE INVENTION 
     Problems that the Invention is to Solve 
     The invention has been developed to solve the above problems. It is an object of the invention to provide a liquid filled type vibration isolator which can reduce generation of abnormal noise without decreasing vibration isolating capability. 
     Solution Means of the Problems 
     A liquid filled type vibration isolator according to the invention includes: a first attachment member; a cylindrical second attachment member; a vibration isolating base made of rubber-like elastic material for connecting the first attachment member and the second attachment member; a diaphragm formed by a rubber film and attached to the second attachment member to form a liquid filled chamber between the diaphragm and the vibration isolating base; a partitioning member for partitioning the liquid filled chamber into a first liquid chamber on the vibration isolating base side and a second liquid chamber on the diaphragm side; and an orifice for connecting the first liquid chamber and the second liquid chamber such that these liquid chambers can communicate with each other. 
     The partitioning member includes: 
     an annular orifice forming member provided inside a circumferential wall of the second attachment member to form the orifice; 
     a rubber wall whose outer circumference is bonded to an inner circumferential surface of the orifice forming member by vulcanization to close the inside of the inner circumferential surface of the orifice forming member; and 
     a pair of partitioning plates connected with each other via a connecting member penetrating through a central area of the rubber wall in the radial direction, between which plates the rubber wall is sandwiched in an axial direction of the rubber wall. 
     One of the pair of the partitioning plates constitutes a part of a chamber wall of the first liquid chamber and the other partitioning plate constitutes a part of a chamber wall of the second liquid chamber. Displacements of the pair of the partitioning plates in an axial direction of the orifice forming member are regulated by the rubber wall. 
     According to this structure, the displacements of the pair of the partitioning plates are regulated by the rubber wall provided inside the inner circumferential surface of the orifice forming member. Thus, the vibration isolator offers desired vibration isolating capability for absorbing high-frequency vibration while regulating displacements of the pair of the partitioning plates caused by vibration having large amplitude. More specifically, at the time of vibration having large amplitude, liquid flows between the first liquid chamber and the second liquid chamber through the orifice to produce liquid flow effect which decreases the vibration. At the time of high-frequency vibration having small amplitude, the pair of the partitioning plates reciprocate as one body and absorb liquid pressure in the first liquid chamber to decrease the vibration. Since the pair of the partitioning plates face the first liquid chamber and the second liquid chamber, the liquid pressure fluctuations in the first liquid chamber can be adequately transmitted to the second liquid chamber. Thus, both the first liquid chamber and the second liquid chamber can produce resonance effect, resulting in improvement of vibration reduction effect. 
     According to this structure, the rubber wall is interposed between the pair of the partitioning plates and other hard components such as the orifice forming member. Thus, impact caused by collision of the pair of the partitioning plates with the rubber wall at the time of vibration having large amplitude or high-frequency vibration is absorbed by the rubber wall. As a result, the impact is not easily transmitted to the second attachment member and the first attachment member. 
     According to an example of the liquid filled type vibration isolator of the invention, an attachment hole through which the connecting member penetrates is formed in the central area of the rubber wall. Annular convexes project from the front and back of the rubber wall around the attachment hole to the outside in the axial direction. The annular convexes engage with annular concaves each of which is formed on the corresponding plate of the two partitioning plates. In this case, the rubber wall and the partitioning plates are positioned in the radial direction. In addition, even when the attachment hole is subject to expansion at the time of input of vibration having large amplitude, separation of the partition plates from the rubber wall is prevented by the engagement between the convexes and the concaves on the partitioning plates. 
     According to an example of the liquid filled type vibration isolator of the invention, the respective ends of the outer peripheries of the partitioning plates are located inside the outer circumferential edge of the rubber wall and the inner circumferential surface of the orifice forming member in the radial direction. In this case, the spring constant slowly increases at the time of input of vibration having large amplitude, thereby reducing generation of abnormal noise. Since the force received by the partitioning plates is transmitted to the orifice forming member via the rubber wall only as a force substantially in the shearing direction, the orifice forming member receives only small force. 
     According to an example of the liquid filled type vibration isolator of the invention, each of the partitioning plates has a first partitioning plate portion disposed at the center in the radial direction for connection, a second partitioning plate portion disposed outside the first partitioning plate portion in the radial direction for holding the rubber wall, and a third partitioning plate portion disposed outside the second partitioning plate portion in the radial direction at a position opposed to the rubber wall with a clearance between the third partitioning plate portion and the rubber wall. In this case, the vibration isolating capability is adjustable by controlling the clearance. 
     According to an example of the liquid filled type vibration isolator of the invention, a plate surface of the third partitioning plate portion facing the rubber wall and a wall surface of the rubber wall opposed to the plate surface have tapered surfaces which extend outward in the radial direction while inclining outward in the axial direction of the rubber wall. The clearance between the third partitioning plate portion and the rubber wall gradually expands toward the outside in the radial direction of the orifice forming member. In this case, the displacements of the plate surfaces of the partitioning plates are regulated by the wall surfaces of the rubber wall softly, and thus collision is not easily caused. 
     According to an example of the liquid filled type vibration isolator of the invention, the connecting member has a convex formed on the first partitioning plate portion of one of the partitioning plates. An attachment hole through which the convex is press-fitted penetrates through the central area of the rubber wall. The distal end of the convex engages with an engaging portion formed on the first partitioning plate portion of the other partitioning plate to be fixed thereto. In this case, the pair of the partitioning plates can be securely connected. 
     According to an example of the liquid filled type vibration isolator of the invention, the external shape of the one partitioning plate facing the first liquid chamber is larger than that of the other partitioning plate facing the second liquid chamber. In this case, the following advantages are offered. Generally, the force applied to the pair of the partitioning plates is larger during pressure-applied displacement in the first liquid chamber than during negative pressure displacement. Since the external shape is determined as above, displacement regulation effect can be increased according to the degree of the force applied to the partitioning plates. Therefore, the liquid flow effect produced by the orifice at the time of input of vibration having large amplitude can be more effectively increased. 
     According to an example of the liquid filled type vibration isolator of the invention, a first outer periphery of the diaphragm is bonded at least to an inner periphery of an annular attachment plate by vulcanization, and a second outer periphery of the attachment plate is fixed to an inner circumferential surface of the second attachment member. A cylindrical standing wall extending upward in an inner axial direction of the orifice forming member is provided on the inner periphery of the attachment plate. The first outer periphery of the diaphragm is bonded to the inner periphery of the attachment plate by vulcanization in such a condition as to cover the standing wall. The standing wall engages with the inner surface of one end of the orifice forming member. The orifice forming member is sandwiched between an attachment plate portion of the standing wall at the root and a receiving step formed on the vibration isolating base to be fixed therebetween. A rubber portion of the first outer periphery of the diaphragm is interposed between the attachment plate portion and the one end of the orifice forming member and between an outer circumferential surface of the standing wall of the attachment plate and an inner circumferential surface of the one end of the orifice forming member. In this case, the following advantages are offered. 
     Since the cylindrical standing wall engages with the inner surface of the one end of the orifice forming member, the orifice forming member is positioned in the radial direction of the orifice forming member. Since the rubber portion of the first outer periphery of the diaphragm is interposed between the attachment plate portion and the one end of the orifice forming member and between the outer circumferential surface of the standing wall of the attachment plate and the inner circumferential surface of the one end of the orifice forming member, the impact is absorbed by the rubber portion even when the impact is transmitted to the orifice forming member. Thus, transmission of the impact to the vehicle body via the attachment plate and the second attachment member is prevented. Furthermore, a ring-disk-shaped metal pinching member for pinching and fixing the orifice forming member together with the receiving step formed on the vibration isolating base can be eliminated, resulting in reduction of number of components and weight and simplification of the structure. 
     Advantage of the Invention 
     According to the invention, a liquid filled type vibration isolator which reduces generation of abnormal noise without lowering vibration isolating capability is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-sectional view of a liquid filled type vibration isolator in an embodiment. 
         FIG. 2  is a vertical cross-sectional view of a partitioning member and a diaphragm of the vibration isolator. 
         FIG. 3  is a vertical cross-sectional view of the partitioning member. 
         FIG. 4  is a vertical cross-sectional view of the diaphragm. 
         FIG. 5  is a vertical cross-sectional view of a connection structure for connecting the partitioning member and the diaphragm. 
         FIG. 6  is a plan view of the partitioning member. 
         FIG. 7  is a view in a direction indicated by an arrow F in  FIG. 6 . 
         FIG. 8  is a vertical cross-sectional view of the disassembled partitioning member. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     An embodiment according to the invention is hereinafter described with reference to the drawings.  FIG. 1  is a vertical cross-sectional view of a liquid filled type vibration isolator  100  in this embodiment. The vibration isolator  100  includes a first attachment metal fitting  1  attached to an automobile engine, a second cylindrical attachment metal fitting  2  attached to a body frame positioned below the engine, a vibration isolating base  3  made of rubber-like elastic material for connecting the first and second fittings  1  and  2 , a stopper metal fitting  40 , and a rubber cover  41  for covering the stopper metal fitting  40 . 
     The first attachment metal fitting  1  has a first attachment bolt  6 A projecting upward. The second attachment metal fitting  2  is constituted by a cylindrical metal fitting  4  on which the vibration isolating base  3  is formed by vulcanization, and a cup-shaped bottom metal fitting  5 . A second attachment bolt  6 B projecting downward is provided in the central area of the bottom metal fitting  5 . The vibration isolating base  3  has a truncated cone shape. The upper end surface of the base  3  is bonded to the first attachment metal fitting  1  by vulcanization, and the lower end portion of the base  3  is bonded to an upper end opening of the cylindrical metal fitting  4  by vulcanization. The upper end opening of the fitting  4  extends upward while gradually expanding. A rubber-film-shaped seal wall  7  for covering the inner circumferential surface of the cylindrical metal fitting  4  is provided at the lower end of the vibration isolating base  3 . 
     A partially spherical diaphragm  9  is attached to the second attachment metal fitting  2 . The diaphragm  9  is formed by a rubber film and constitutes a liquid filled chamber  8  between the lower surface of the vibration isolating base  3  and the diaphragm  9 . The liquid filled chamber  8  is filled with liquid. The diaphragm  9  is covered by the bottom metal fitting  5 . A partitioning member  12  for partitioning the liquid filled chamber  8  into a first liquid chamber  11 A on the vibration isolating base  3  side and a second liquid chamber  11 B on the diaphragm  9  side is equipped. An orifice  25  is formed so that the first liquid chamber  11 A and the second liquid chamber  11 B can communicate with each other. 
     The partitioning member  12  has: an annular orifice forming member  16  provided inside a cylindrical circumferential wall  28  of the second attachment metal fitting  2 ; a rubber wall  15  whose outer circumference  15 G is bonded to an inner circumferential surface  16 N of the orifice forming member  16  by vulcanization to close the inside of the inner circumferential surface  16 N; and a pair of upper and lower partitioning plates  17  and  18  connected with each other via a connecting member (corresponding to a first convex  48  to be described later) penetrating through a central area  15 T of the rubber wall  15  in the radial direction. The rubber wall  15  is sandwiched between the pair of the partitioning plates  17  and  18  in an axial direction G of the rubber wall  15 . 
     The orifice forming member  16  forms the orifice  25  between the orifice forming member  16  and the circumferential wall  28  of the second attachment metal fitting  2 , more specifically, between the orifice forming member  16  and the seal wall  7  covering the inner circumferential surface of the circumferential wall  28 , and engages with the inner circumference of the circumferential wall  28 . Thus, the orifice  25  is formed along the circumference of the orifice forming member  16  (see  FIGS. 6 and 7 ) in a circumferential direction P. The orifice forming member  16  has a plurality of ribs  90 . 
     The rubber wall  15  is a disk-shaped component. The outer circumference  15 G of the rubber wall  15  is bonded to an inner circumferential surface  16 N of a cylindrical main body  16 H of the orifice forming member  16  by vulcanization (see  FIG. 3 ). 
     The partitioning plate  18  of the two partitioning plates  17  and  18  constitutes a part of the chamber wall of the first liquid chamber  11 A (that is, disposed facing the first liquid chamber  11 A), and the other partitioning plate  17  constitutes a part of the chamber wall of the second liquid chamber  11 B (that is, disposed facing the second liquid chamber  11 B). The displacements of the pair of the partitioning plates  17  and  18  are regulated by the rubber wall  15  in an axial direction G of the orifice forming member  16  (identical to the axial direction G of the rubber wall  15 ). 
     The ends of outer circumferential edges  17 G and  18 G of the partitioning plates  17  and  18  are positioned inside the outer circumferential edge of the rubber wall  15  and the inner circumferential surface  16 N of the orifice forming member  16  in the radial direction (see  FIG. 3 ). In this embodiment, as illustrated in  FIG. 2 , the position of the outer circumferential edge of the rubber wall  15  coincides with the position of the inner circumferential surface  16 N of the orifice forming member  16  as the position of the junction surface of these components in a radial direction K of the orifice forming member  16 . Thus, outside diameters D 1  and D 2  of the partitioning plates  17  and  18  are smaller than a diameter D 0  of the junction surface (that is, the inner circumferential surface  16 N), and the external shapes of the partitioning plates  17  and  18  are smaller than the external shape of the rubber wall  15  in the plan view (see  FIG. 6 ). In this embodiment, the external shape of the partitioning plate  18  facing the first liquid chamber  11 A is larger than the external shape of the partitioning wall  17  facing the second liquid chamber  11 B (outside diameter D 1  of partitioning plate  18 &gt;outside diameter D 2  of partitioning plate  17 ). 
     As illustrated in  FIG. 8 , each of the partitioning plates  17  and  18  has a first partitioning plate portion  51  provided at the center in the radial direction for connection, a second partitioning plate portion  52  positioned outside the first partitioning plate portion  51  in the radial direction to hold the rubber wall  15 , and a third partitioning plate portion  53  positioned outside the second partitioning plate portion  52  in the radial direction at a position opposed to the rubber wall  15  with a clearance S between the third partitioning plate portion  53  and the rubber wall  15  (see  FIG. 3 ). A plate surface  53 C of the third partitioning plate portion  53  facing the rubber wall  15  and a wall surface  15 C of the rubber wall  15  opposed to the plate surface  53 C have tapered surfaces which extend outward in the radial direction while inclining outward in the axial direction of the rubber wall  15 , and the clearance S gradually expands toward the outside in the radial direction of the orifice forming member  16 . By this arrangement, the thickness of the rubber wall  15  gradually increases toward the outside in the radial direction. The tapered surfaces have smoothly curved shapes in the vertical cross section of the partitioning member  12 . An axial center O of the rubber wall  15  coincides with an axial center O of the partitioning plates  17  and  18 . 
     The connecting member has the cylindrical first convex  48  projecting from the first partitioning plate portion  51  of the partitioning plate  18 . An attachment hole  60  through which the first convex  48  is press-fitted penetrates through an central area  15 T of the rubber wall  15 . An annular distal end  48 A of the first convex  48  engages with an engaging portion  61  formed on the first partitioning plate portion  51  of the partitioning plate  17  to be fixed thereto. The engaging portion  61  has an annular first groove  61 A and a second convex  61 B projecting from a position inside the first groove  61 A in the radial direction. The first convex  48  is press-fitted through the attachment hole  60 . An annular third convex  70  projecting from the inner circumferential edge of the rubber wall  15  to one side in the axial direction engages with the inner surface of the first groove  61 A. The second convex  61 B engages with the inner surface of a hollow  71  at the distal end  48 A of the first convex  48 . An annular second groove  73  surrounding the first convex  48  is formed at the base end of the first convex  48 . An annular fourth convex  74  projecting from the inner circumferential edge of the rubber wall  15  to the other side in the axial direction engages with the second groove  73 . 
     The annular convexes  70  and  74 , which project from the back and front of the rubber wall  15  around the attachment hole  60  to the outside in the axial direction, engage with the annular concave grooves  61 A and  73  formed on the pair of the partitioning plates  17  and  18  when the rubber wall  15  and the pair of the partitioning plates  17  and  18  are assembled. The pair of the partitioning plates  17  and  18  are formed by resin material. The first convex  48  and the engaging portion  61  are fixed to each other by ultrasonic welding. 
     As illustrated in  FIGS. 6 and 7 , a vertical wall  42  for forming an end  45  of the orifice  25  in the circumferential direction P is provided on the orifice forming member  16 . The orifice forming member  16  has a first opening  31  for connecting the orifice  25  and the first liquid chamber  11 A, and a second opening  35  for connecting the orifice  25  and the second liquid chamber  11 B. 
     As illustrated in  FIGS. 1 and 4 , a first outer periphery  14  of the diaphragm  9  is bonded to an inner circumferential edge  13 N of the annular attachment plate  13  by vulcanization, and a second outer periphery  13 G of the attachment plate  13  is fixed to an inner circumference  2 N of the second attachment metal fitting  2 . More specifically, the second outer periphery  13 G of the attachment plate  13  and the upper end of the bottom metal fitting  5  are covered by the lower end of the cylindrical metal fitting  4 , and these three portions are caulked into one body. 
     As illustrated in  FIG. 5 , a cylindrical standing wall  29  which extends upward in an inner axial direction G 1  of the orifice forming member  16  is provided on an inner periphery  13 N of the attachment plate  13 . The first outer periphery  14  of the diaphragm  9  is bonded to the inner periphery  13 N of the attachment plate  13  by vulcanization in such a condition that the outer periphery  14  covers the standing wall  29 . The standing wall  29  engages with the inner surface of one end  16 A of the orifice forming member  16 . The orifice forming member  16  is sandwiched between an attachment plate portion  32  at the root of the standing wall  29  and a receiving step  33  formed on the vibration isolating base  3  (see  FIG. 1 ) and fixed therebetween. A rubber portion  34  of the first outer periphery  14  of the diaphragm  9  is interposed between the attachment plate portion  32  and the one end  16 A of the orifice forming member  16  and between an outer circumferential surface  29 G of the standing wall  29  and the inner circumferential surface  16 N of the one end  16 A of the orifice forming member  16 . 
     The first outer periphery  14  of the diaphragm  9  is bonded to the inner periphery  13 N of the attachment plate  13  by vulcanization in such a condition that the first outer periphery  14  covers a convex side surface  36 N of a corner  36  formed by the standing wall  29  and the attachment plate portion  32 . The convex side surface  36 N of the corner  36  has a circular-arc-shaped vertical cross section. The first outer periphery  14  of the diaphragm  9  freely swings upward and downward around the corner  36  having the circular-arc-shaped vertical cross section in accordance with input of vibration. 
     According to the liquid filled type vibration isolator  100  having this structure in this embodiment, displacements of the pair of the partition plates  17  and  18  are regulated by the rubber wall  15  at the time of generation of low-frequency vibration having large amplitude. As a result, liquid flows between the first liquid chamber  11 A and the second liquid chamber  11 B through the orifice  25 , and the vibration is decreased by liquid flow effect thus produced. Since the external shapes of the partition plates  17  and  18  are smaller than that of the rubber wall  15 , a region constituted only by the rubber wall  15  having no rigidity is secured between the inner circumferential surface  16 N of the orifice forming member  16  and the partitioning plates  17  and  18 . Thus, the force received by the partitioning plates  17  and  18  at the time of input of the vibration having large amplitude is transmitted to the orifice forming member  16  via the rubber wall  15  only as a force substantially in the shearing direction. Therefore, the orifice forming member  16  receives only small force, and the spring constant slowly increases. Moreover, since the thickness of the rubber wall  15  outside the partitioning plates  17  and  18  in the radial direction is large, the rubber wall  15  has excellent capability for regulating displacements of the partitioning plates  17  and  18 . 
     When high-frequency vibration having small amplitude is generated, the displacements of the pair of the partitioning plates  17  and  18  are not regulated by the rubber wall  15 . In this case, the partitioning plates  17  and  18  reciprocate as one body. As a result, liquid pressure in the first liquid chamber  11 A is absorbed and thereby the vibration is decreased. Since the pair of the partitioning plates  17  and  18  face the first liquid chamber  11 A and the second liquid chamber  11 B, respectively, the liquid pressure fluctuations in the first liquid chamber  11 A can be adequately transmitted to the second liquid chamber  11 B. Thus, both the first liquid chamber  11 A and the second liquid chamber  11 B can produce resonance effect, resulting in improvement of vibration reduction effect. 
     In this embodiment, the rubber wall  15  is interposed between the pair of the partition plates  17  and  18  and the orifice forming member  16 . Thus, the impact produced by the collision of the pair of the partition plates  17  and  18  with the rubber wall  15  at the time of vibration having large amplitude or absorption of high-frequency vibration is absorbed by the rubber wall  15 . As a result, the impact is not easily transmitted to the second attachment metal fitting  2  and the first attachment metal fitting  1 . Furthermore, the orifice forming member  16  is fixed to the second attachment metal fitting  2  via the seal wall  7 , the receiving step  33 , and the rubber portion  34  of the diaphragm  9  as elastic members. Thus, even when the impact is transmitted to the orifice forming member  16 , the impact is absorbed by these elastic portions without transmission to the vehicle body. 
     According to this embodiment, therefore, the partition plates  17  and  18  are easily displaced for high-frequency vibration having small amplitude. On the other hand, the displacements of the partition plates  17  and  18  are regulated as much as possible for the input of vibration having large amplitude so that liquid flow effect can be produced by the orifice  25 . Moreover, transmission of the impact caused at the time of collision of the partition plates  17  and  18  with the rubber wall  15  to the vehicle cabin can be prevented. 
     According to this embodiment, the annular convexes  70  and  74  are formed on the back and front surfaces of the rubber wall  15  around the attachment hole  60 , and the rubber wall  15  is fixed to the pair of the partitioning plates  17  and  18  under the condition where the convexes  70  and  74  engage with the grooves  61 A and  73  of the partitioning plates  17  and  18 . Thus, even when the attachment hole  60  of the rubber wall  15  is subject to expansion by excessively large force applied to the partitioning plates  17  and  18  particularly at the time of input of vibration having large amplitude, separation of the partition plates  17  and  18  from the rubber wall  15  is prevented by the engagement between the convexes  70  and  74  and the grooves  61 A and  73 . 
     According to this embodiment, the partitioning plate  18  on the first liquid chamber  11 A side is larger than the partitioning plate  17  on the second liquid chamber  11 B side. Thus, the downward displacement (that is, toward the second liquid chamber  11 B) of the pair of the partitioning plates  17  and  18  is more largely regulated than the upward displacement (that is, toward the first liquid chamber  11 A). Generally, at the time of input of vibration having large amplitude, the force applied to the pair of the partitioning plates  17  and  18  is larger during pressure-applied displacement in the first liquid chamber  11 A in which the partitioning plates  17  and  18  are displaced downward than during negative pressure displacement in which the partitioning plates  17  and  18  are displaced upward. Since the sizes of the partitioning plates  17  and  18  are determined as above, displacement regulation effect can be increased according to the degree of the force applied to the partitioning plates  17  and  18 . Therefore, the liquid flow effect produced by the orifice  25  at the time of input of vibration having large amplitude can be more effectively increased. 
     In the structure having a dedicated pinching member for pinching and fixing the orifice forming member together with the receiving step of the vibration isolating base and an opening formed on the pinching member and open to the second liquid chamber, for example, a time-consuming process for positioning the orifice forming member in the circumferential direction relative to the pinching member is required for the purpose of determining the length of the orifice in the circumferential direction. However, when the vertical wall  42  for forming the end  45  of the orifice  25  in the circumferential direction P and the second opening  35  for connecting the orifice  25  and the second liquid chamber  11 B are provided on the orifice forming member  16  as in this embodiment, the length of the orifice  25  in the circumferential direction P can be determined only by the orifice forming member  16 . Thus, the necessity for the process for positioning the orifice forming member is eliminated, and thus the work efficiency can be improved. 
     Moreover, the first outer periphery  14  of the diaphragm  9  is bonded by vulcanization in such a condition to cover the convex side surface  36 N of the corner  36  having a circular-arc-shaped vertical cross section on the attachment plate  13 . Thus, the first outer periphery  14  of the diaphragm  9  can swing around the corner  36  having the circular-arc-shaped vertical cross section in accordance with input of vibration. Accordingly, the problem that force is concentrated on a part of the first outer periphery  14  of the diaphragm  9  can be avoided, and durability of the diaphragm  9  can be increased. 
     DESCRIPTION OF REFERENCE NUMERALS AND SIGNS 
       1  . . . first attachment member (first attachment metal fitting
   2  . . . second attachment member (second attachment metal fitting),  2 N . . . inner circumference
   3  . . . vibration isolating base
   8  . . . liquid filled chamber
   9  . . . diaphragm
   11 A . . . first liquid chamber
   11 B . . . second liquid chamber
   12  . . . partitioning member
   13  . . . attachment plate,  13 N . . . inner periphery,  13 G . . . second outer periphery
   14  . . . first outer periphery
   15  . . . rubber wall,  15 C . . . wall surface,  15 G . . . outer circumference,  15 T . . . central area in radial direction
   16  . . . orifice forming member,  16 A . . . one end,  16 N . . . inner circumferential surface
   17  . . . partitioning plate (other partitioning plate)
   18  . . . partitioning plate (one partitioning plate)
   25  . . . orifice
   28  . . . circumferential wall
   29  . . . standing wall,  29 G . . . outer circumferential surface
   32  . . . attachment plate portion
   33  . . . receiving step
   34  . . . rubber portion
   48  . . . connecting member (convex (first convex)),  48 A . . . distal end
   51  . . . first partitioning plate portion
   52  . . . second partitioning plate portion
   53  . . . third partitioning plate portion,  53 C . . . plate surface
   60  . . . attachment hole
   61  . . . engaging portion,  61 A . . . first groove (annular concave),  61 B . . . second convex
   70  . . . third convex (annular convex)
   73  . . . second groove (annular concave)
   74  . . . fourth convex (annular convex)
   100  . . . liquid filled type vibration isolator
 
G . . . axial direction of orifice forming member (axial direction of rubber wall)
 
G 1  . . . inner axial direction of orifice forming member
 
K . . . radial direction of orifice forming member
 
S . . . clearance