Abstract:
The present invention aims at providing a liquid sealed type vibration isolator capable of positioning a partition excellently with the construction of the partition simplified, and maintaining stable damping characteristics of an orifice. To meet the requirements, an outer circumferential portion of the partition forming the orifice is made so that the outer circumferential portion defines at least a part of one or two sides of a cross section of the orifice, and a positioning device formed of a partition press fitting or inserting structure with respect to a groove, or a partition engaging structure is provided in a joint portion between the partition and the other orifice forming member with the construction of the partition simplified, whereby it is rendered possible to improve the accuracy of the partition and obtain a desired cross section of the orifice. When an elastic film is provided on the partition so as to reduce a dynamic spring constant in a high-frequency region, the steps of forming one cylindrical partition and a disc type elastic film separately, forming a positioning bore in a lower surface of a circumferential portion of the elastic film, and positioning the partition radially by press fitting or inserting an upper cylindrical portion thereof into the bore are employed, whereby the manufacturing cost is reduced.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a liquid sealed type vibration isolator used to support a vibration generating member including mainly an automobile engine. 
     2. Description of the Related Art 
     The known liquid sealed type vibration isolators, such as an engine mount for supporting a vibration generating member, such as an automobile. engine so that the vibration of the vibration generating member is not transmitted to a body include, for example, a liquid sealed type vibration isolator shown in FIG. 26, or a liquid sealed type vibration isolator shown in FIG. 27 or  28 . 
     All of these related art liquid sealed type vibration isolators  100  include a metal fixing member  102  to be secured to one of vibration generating member, such as an engine and a support member, such as a body, a metal fixing member  103  to be secured to the other thereof, a vibration isolating base member  104  connecting these two metal fixing members  102 ,  103  together and formed of an elastic body of a rubber-like material, a diaphragm  106  provided on the side of the metal fixing member  103  so as to be opposed to the vibration isolating base member  104 , a liquid chamber  105  formed between the vibration isolating base member  104  and diaphragm  106 , and a partition  107  dividing the liquid chamber  105  into two, i.e. a main liquid chamber  105   a  and an auxiliary liquid chamber  105   b , an orifice  118  communicating the main and auxiliary liquid chambers with each other being formed on an outer circumferential side of the partition  107  to fulfil a vibration damping function of the vibration isolator by an effect of flows of a liquid, which occur owing to the provision of the orifice  118 , in the two liquid chambers, and also a vibration insulating function of the vibration isolator by the vibration isolating base member  104 . 
     In the case of the liquid sealed type vibration isolator shown in FIG. 27 or  28 , an elastic film of a rubber-like material  180  is provided in addition to the above-described structure, in a central region of the partition  107  by a vulcanization bonding device or a sandwiching device so as to reduce a dynamic spring constant of a high-frequency region (especially, an engine noise region). 
     In order to obtain stable product characteristics of such a liquid sealed type vibration isolator, it becomes an important factor that the volume, especially, a cross-sectional area of the orifice having a vibration damping function be set to a desired level. 
     However, all of the liquid sealed type vibration isolators of FIGS. 26,  27  and  28  employ a mode in which an outer circumferential portion of the partition  107  constitutes upper and inner circumferential surfaces and a bottom surface of the orifice, i.e. three sides of a cross section of the orifice, and in which a cylindrical liquid chamber-forming rubber portion  122 , which guides the partition  107  for the press fitting of the same thereinto, and which is on the inner circumferential side of a cylindrical trunk portion  114  of the metal fixing member  103 , constitutes the remaining one side (outer circumferential surface) of the cross section of the orifice. 
     Therefore, when, especially, the partition  107  is formed by bending one piece of metal plate by pressure molding or deep drawing, a molding process for forming the three sides of a cross section of the orifice becomes complicated. 
     When the construction of the partition  107  is simplified so that the pressing or deep drawing thereof can be carried out easily, for the purpose of overcoming the difficulties, there is the possibility that problems arise concerning the radial and vertical positioning of the partition. Especially, when a structure like those of the related art vibration isolators of FIGS. 26,  27  and  28  is employed in which a lower end portion of the partition  107  is bent radially outward with the resultant outer end portion  171  caulked to a caulking portion of the metal fixing member  103 , i.e. a fastened section  116  formed by a caulking device and formed of the cylindrical trunk portion  114  and a bottom member  113  of the metal fixing member  103 , there is the possibility that the partition  107  slips in the radial and vertical directions due to a tightening force of the caulking device. 
     When the partition is thus displaced in the radial and vertical directions, the orifice formed by utilizing the partition cannot be set to a desired cross-sectional area, so that stable product characteristics cannot be obtained. 
     According to an aspect of the present invention, the liquid sealed type vibration isolator is capable of solving these problems, and obtaining stable characteristics. 
     In the case of the liquid sealed type vibration isolator provided with the elastic film  180  in a central region of the partition  107  which divides the liquid chamber  105  into two, i.e. main and auxiliary chambers, the elastic film setting system has problems different from those encountered in the above-described vibration isolator. 
     Namely, in the case of the liquid sealed type vibration isolator of FIG. 27, the lower end portion of the partition  107  is caulked to the fastened section  116  of one metal fixing member  103  with an upper end portion of a cylindrical side wall  172  expanded and press fitted into an inner circumference of the liquid chamber-forming rubber portion  122 , whereby the orifice  118  is formed between the cylindrical side wall and liquid chamber-forming rubber portion  122 . The elastic film of a rubber-like material  180  is vulcanization bonded to a central opening of a top plate portion  123  of the partition  107 . 
     In the case of the liquid sealed type vibration isolator of FIG. 28, the partition  107  is formed of two partition members  107   a ,  107   b . The upper partition member  107   a  is of a disc type shape, provided with an opening  173  in a central portion thereof and press fitted in the liquid chamber-forming rubber portion  122 . The lower partition member  107   b  is formed to a shape of an inverted cup, bent radially outward at a lower end portion thereof and caulked at the same portion to the fastened section  116  of the metal fixing member  103 , provided with an opening  175  in a top plate portion  174  thereof, and has the elastic film of a rubber-like material  180  held between the top plate portion  174  and upper partition member  107   a . A space surrounded by an outer circumferential portion of the upper partition member  107   a , cylindrical side wall  172  of the lower partition member  107   b  and liquid chamber-forming rubber portion  122  forms the orifice  118  which communicates the main and auxiliary liquid chambers  105   a ,  105   b  with each other. 
     Regarding a method of setting the elastic film  180 , the partition  107  of the type in which the elastic film  180  is held between two pressing metal members (partition members) shown in the related art example of FIG. 28, the shapes of the two partition members are simplified but two metal press dies for the manufacturing of the partition members become necessary. In the case of the partition in the related art example of FIG.  27  of the type which is formed by bending one piece of metal plate, and vulcanization bonding the elastic film  180  to the bent plate, the molding of the partition itself becomes complicated, and a bonding agent application step has to be carried out before the elastic film has been formed. In all of these cases, the cost increases. 
     According to another aspect of the present invention, the liquid sealed type vibration isolator capable of solving the above-mentioned problems, facilitating the manufacturing of the partition provided with an elastic film thereon, and reducing the manufacturing cost. 
     SUMMARY OF THE INVENTION 
     In order to achieve the first-mentioned vibration isolator, the inventors of the present invention earnestly discussed the members by which the orifice should be formed and how to position these members for obtaining a desired cross-sectional area of the orifice, with the simplification of the partition taken into consideration as a premise. 
     As a result, the inventors discovered that, when the orifice was formed by defining two or one side of across section thereof out of three sides thereof by the partition, and the remaining sides thereof by, for example, the liquid chamber-forming rubber portion, vibration isolating base member or an outer circumferential reinforcing metal member of the diaphragm, and not by defining the three sides of such a cross section by the partition as in the related art examples, the shape of the partition was simplified correspondingly. 
     Namely, the first-mentioned invention is a liquid sealed type vibration isolator the construction of which is basically identical with those of the above-described related art examples, i.e., includes two metal fixing members for a vibration generating member and a support member, a vibration isolating base member interposed between the two metal fixing members and formed of an elastic body of a rubber-like material, a diaphragm provided so as to be opposed to the vibration isolating base member, a liquid chamber formed between the vibration isolating base member and diaphragm, and a partition dividing the liquid chamber into two, i.e. a main liquid chamber and an auxiliary liquid chamber, an orifice being formed between the partition and a liquid chamber-forming rubber portion on an outer circumferential side thereof, an outer circumferential portion of the partition being formed so as to define at least a part of one or two sides of a cross section of the orifice, either one of the partition and the other orifice-forming member being press fitted or inserted or engaged at a part thereof in a connecting section between the partition and the remaining orifice-forming member into or with the other thereof, whereby the partition and the other orifice-forming member are positioned. 
     According to this liquid sealed vibration isolator, the partition forms at least only a part of one or two of the wall surfaces of the orifice, the shape of the partition is simplified and variation of the shape thereof decreases. Moreover, the partition and the other orifice-forming member are positioned at the connecting section therebetween by a press fitting or inserting or engaging structure. Therefore, even when a flange portion at a lower section of the partition is caulked to the relative metal fixing member, the partition is retained without being displaced. This enables the partition molding work to be carried out easily, a highly accurate desired cross section of the orifice to be obtained, and stable characteristics to be secured. 
     In this structure, the partition defines at least a part of two or one side of the cross section of the orifice, so that the positioning of the partition in the liquid chamber becomes an important factor. Therefore, it is specially preferable in view of the accuracy of this positioning operation that a positioning device be formed by providing an annular positioning groove in either one of the partition and the other orifice-forming member, and a free end portion, which is to be press fitted or inserted into the groove, on the other thereof. 
     In this liquid sealed type vibration isolator, it is possible that the outer circumferential portion of the partition has a mode in which this outer circumferential portion is bent to an L-shaped cross section so as to define the inner circumferential surface and bottom surface of the orifice, and a mode in which the mentioned outer circumferential portion is formed as a substantially vertical wall so as to define the inner circumferential surface of the orifice with the outer circumferential reinforcing metal member of the diaphragm, which is positioned on the lower side of the vertical wall, utilized as a bottom wall of the orifice. All of these modes enable the shape of the partition to be simplified, and variation of the shape thereof and that of the shape of the outer circumferential reinforcing metal member of the diaphragm to be minimized. 
     A device for positioning the partition of the above-described construction employs the following structure. 
     When the outer circumferential portion of the partition is formed to an L-shaped cross section so as to define the inner circumferential and bottom surfaces of the orifice, an upper end section of the outer circumferential portion, which defines the inner circumferential surface of the orifice, is extended upward, i.e., in the partition inserting direction, and an annular positioning groove is formed in the liquid chamber-forming edge portion, which is opposed to this upwardly extended portion, of the vibration isolating base member, the partition being positioned by press fitting or inserting the upwardly extended portion into the groove. 
     Owing to this arrangement, the upper end portion of the partition is engaged with the liquid chamber-side circumferential portion of the vibration isolating base member by the press fitting of the former into the groove of the latter. Therefore, even when a lower portion of the partition is bent and extended radially outward so as to form a bottom wall of the orifice with an outer circumferential end section of the resultant lower extended portion caulked to the relative metal fixing member, the radial and vertical positioning accuracy can be kept high, and a desired cross section of the orifice can be obtained. 
     Even in the case where the outer circumferential portion of the partition is formed as a substantially vertical wall with the outer circumferential metal member of the diaphragm defining a bottom surface of the orifice, the upper end section of the outer circumferential portion of the partition is extended upward, and an annular positioning groove is formed in the liquid chamber-side circumferential edge portion, which is opposed to this upwardly extended portion, of the vibration isolating base member in the same manner as in the above-described case, the partition being positioned by press fitting or inserting the upwardly extended portion into the groove. 
     In this case, the partition is also positioned by engaging the upper end portion thereof with the liquid chamber-side circumferential edge portion of the vibration isolating member by press fitting the former into the groove of the latter, while the bottom surface of the orifice is positioned by caulking the outer circumferential reinforcing metal member of the diaphragm to the relative metal fixing member. Accordingly, a desired cross section of the orifice can be retained with a high accuracy. 
     When the outer circumferential reinforcing metal member of the diaphragm defines the bottom surface of the orifice as mentioned above, it is preferable that the connecting surfaces of the bottom wall of the orifice and the lower end of the partition be sealed, with a rubber member interposed therebetween. When a structure in which an annular groove is formed in this rubber member between the two connecting surfaces with the lower end portion of the partition press fitted or inserted in the groove is employed, the positioning of the two parts can also be done excellently. 
     The liquid sealed type vibration isolator according to the present invention can also employ a mode in which the lower surface of the outer circumferential portion of the partition constitutes the upper surface of the orifice, the outer circumferential reinforcing metal member, which is positioned on the lower side of the same lower surface, of the diaphragm being formed to an L-shaped cross section so as to define the inner circumferential and bottom surfaces of the orifice, the upper end portion of the reinforcing metal member being brought into pressure contact with the lower surface of the partition via a seal rubber member, whereby this arrangement is utilized for the formation of the orifice. In this case, the simplification of the shape of the partition, facilitation of the molding process and minimization of the variation of the shape of the partition are also attained. 
     When this structure is employed, it is recommended to bend the outer circumferential end portion of the partition in the upward direction, bring the resultant outer circumferential wall into pressure contact with the inner circumferential surface of the cylindrical liquid chamber-forming rubber portion, and engage the upper end portion of the partition with a flat portion formed on the liquid chamber-side circumferential edge portion, which is positioned above the liquid chamber-forming rubber portion, of the vibration isolating base member, whereby the partition is positioned. This enables the positioning of the partition as well as the outer circumferential metal member of the diaphragm to be done with a high accuracy. 
     Especially, since the circumferential wall is formed by upwardly bending the outer circumferential end portion the partition, an operation of a rib for heightening the rigidity of the partition is performed thereby. The circumferential wall also plays the role of a guide when the partition is press fitted into the vibration isolating base member along the cylindrical liquid chamber-forming rubber portion. 
     The partition can also be positioned by bringing the circumferential wall thereof into pressure contact with the inner circumferential surface of the liquid chamber-forming rubber portion, and press fitting or inserting the upper end section of the circumferential wall of the partition into the annular positioning groove formed in the liquid chamber-side edge portion of the vibration isolating base member. This enables the above-mentioned positioning operation to be carried out in a more desirable manner. 
     The liquid sealed type vibration isolator according to the present invention can also be constructed by forming the outer circumferential portion of the partition as a substantially vertical wall defining an upper half of the inner circumferential surface of the orifice, bending the outer circumferential reinforcing metal member of the diaphragm to an L-shaped cross section so as to define the bottom surface and a lower half of the inner circumferential surface of the orifice, and elastically engaging the upper end of the reinforcing metal member with the lower surface of the partition via the seal rubber member. In this case, the simplification of the shape of the partition, facilitation of the molding process and minimization of the variation of the shape of the partition are also attained. 
     When a structure is employed which is obtained by extending the outer circumferential end portion of the partition in the upward direction, forming an annular positioning groove in the liquid chamber-side edge portion, which is opposed to the upwardly extended portion, of the vibration isolating base member, and positioning the partition by press fitting or inserting the upwardly extended portion of the partition into the groove, the partition is positioned by the groove provided in the vibration isolating base member as well as the outer circumferential reinforcing metal member of the diaphragm caulked to the relative metal fixing member. When a structure is further employed which is obtained by forming an annular groove in the rubber member, and press fitting or inserting the upper end portion of the reinforcing metal member into the groove, the combining of the partition and the outer circumferential reinforcing metal member of the diaphragm with each other is done excellently, and the positioning accuracy and sealability of these parts are more improved. 
     In all of the above-mentioned modes, the cross-sectional shape of the orifice formed on the inner side of the outer circumferential surface of the partition is not specially limited but it is preferable, in view of the necessity of simplification of the construction of the partition, that the portion defining the inner circumferential surface of the orifice has a shape close to that of a vertical wall. As long as this condition is satisfied, the orifice may have any of a triangular cross section and a rectangular cross section. 
     For example, any of a structure in which a cross-sectionally triangular orifice is formed by expanding the lower part of the liquid chamber-forming rubber portion which defines the outer circumferential surface of the orifice, and a structure in which a cross-sectionally rectangular orifice is formed by providing a horizontal flat portion on the part of the liquid chamber-side circumferential edge portion of the vibration isolating base member which is above the liquid chamber-forming rubber portion defining the outer circumferential surface of the orifice, to thereby form the upper surface of the orifice; and having these parts and the partition alone or the outer circumferential metal member of the diaphragm cooperate with each other. 
     The partition may be obtained by any of the method of molding one piece of metal plate into a bent product, and the method of molding a cast product of aluminum into such a product. Especially, the former method enables the pressing work or deep drawing work to be simplified. 
     In any of these modes, varying the radial and vertical sizes of the portion to be press fitted of the partition, and the radial and vertical sizes of the groove formed in the vibration isolating base member, into which the partition is to be press fitted, in such a manner that the groove extends in the direction of the whole circumference of the same base member enable the degree of freedom of a characteristic tuning operation to be increased. Therefore, when the liquid chamber-side circumferential edge portion of the vibration isolating base member is formed as the upper surface of the orifice, a structure is preferably employed which is formed by bending the upper end portion of the relative metal fixing member in the inward direction, and burying the resultant bent portion in the vibration isolating base member to thereby secure an increased rigidity of the portion of the vibration isolating base member which defines the upper surface of the orifice. 
     The shape of the central region of the partition is not specially limited. For example, when it is necessary in the vibration isolator to reduce a dynamic spring constant in a high-frequency region (especially, an engine noise region), a structure having an elastic film provided in the central region of the partition can also be employed. 
     In order to achieve the second-mentioned invention, the inventors of the present invention earnestly discussed the method of setting the elastic film with respect to the partition, to discover that, when one cylindrical partition and an elastic film covering the opening thereof were molded separately with the resultant products positioned firmly, it became possible to reduce the dimensions of a metal vulcanization mold for the elastic film, omit the bonding agent application process, and manufacture the partition at a low cost. 
     Namely, according to a second aspect of the present invention, the liquid sealed type vibration isolator includes in the same manner as the above-described invention two metal fixing members, a vibration isolating base member interposed between the two metal fixing members and formed of an elastic body of a rubber-like material, a diaphragm disposed so as to be opposed to the vibration isolating base member, a liquid chamber formed between the vibration isolating base member and diaphragm, and a partition dividing the liquid chamber into two, i.e. main and auxiliary liquid chambers, an orifice being formed between the partition and a liquid chamber-forming rubber portion extending around the partition, the partition being formed of one cylindrical partition plate, and a disc type elastic film formed to a diameter larger than that of an opening of an upper cylindrical portion of the partition plate and closing the central opening of the partition plate, the elastic film and partition plate being formed separately, the elastic film being provided with a positioning bore in a lower surface of a circumferential portion thereof, the upper cylindrical portion of the partition plate being press fitted or inserted in the positioning bore. 
     This structure enables the dimensions of the metal vulcanization mold for the elastic film to be reduced, and the bonding agent application process to be rendered unnecessary. Moreover, the positioning (centering) of the elastic film and partition plate can be done easily. 
     In order to position the partition vertically, a system for engaging the upper end of the outer circumferential portion of the elastic film with a circumferential wall of the liquid chamber, for example, a liquid chamber-side circumferential edge portion of the vibration isolating base member formed of an elastic body of a rubber-like material; forming a flange portion by bending a lower end portion of the partition in the radially outward direction; and caulking this flange portion to the relative metal fixing member can be employed. Regarding a lower end portion of the partition, a system for supporting a lower end portion of the partition plate by engaging the same lower end portion with the outer circumferential reinforcing metal member of the diaphragm can also be employed. 
     In all of these cases, an orifice having a desired cross-sectional area can be formed between the partition and the liquid chamber-forming rubber portion on the outer circumferential side thereof, and stable characteristics can be secured. 
     Concerning the positioning bore formed in the lower surface of the elastic film, the depth thereof is not specially limited. A groove formed in the lower surface of the circumferential portion of the elastic film, or a slit type through hole extending from at least a part of the lower surface of the circumferential portion of the elastic film to an upper surface can also be substituted for the positioning bore. When the through hole is employed, it is recommended that the upper end section, which is press fitted or inserted through the through hole, of the upper cylindrical portion of the partition plate be bent and caulked. This can prevent the elastic film from coming off, and enables the combining of the partition plate with the elastic film to be done reliably. The upper end section of the upper cylindrical portion may be bent either radially inward or radially outward. 
     The positioning bore is provided preferably so as to extend in the direction of the whole circumference of the elastic film for the purpose of preventing the leakage of a liquid from a clearance between the elastic film and partition plate. In the case of the through hole, forming a connecting portion between the central portion and outer circumferential portion of the elastic film is necessary, so that the through hole has to be formed discontinuously in the circumferential portion thereof. 
     When the cross-sectional area of the orifice is large, the part of the vertically intermediate portion of the cylindrical partition plate which is lower than the lower surface of the elastic film is expanded to form a stepped section on the same intermediate portion, and this stepped section can be used as a bottom wall of the orifice. This enables an orifice of a desired cross-sectional area to be obtained. 
     When the positioning bore is formed of a through hole, it is recommended that the upper end portion, which extends through the through hole, of the partition plate be bent radially outward and caulked, and that the elastic film be held in the direction of the height thereof (vertically) between the resultant bent end portion and the stepped section or the lower flange portion of the partition plate. Owing to this arrangement, the fixing of the partition plate and elastic film to each other can be done more easily and reliably. 
     The elastic film and the upper cylindrical portion of the partition plate which define the inner circumferential surface of the orifice are provided with a first opening communicating the main liquid chamber and orifice with each other, and a second opening communicating the auxiliary liquid chamber and orifice with each other. In order to prevent these two openings from being short-circuited, it is recommended that a partition wall for shutting off an orifice passage be formed on a circumferential portion of the elastic film so as to be integral with the elastic film. Even when this partition wall is provided on any of the vibration isolating base member and the elastic film, the invention can be practiced. However, providing the partition wall on the elastic film is advantageous because it enables the relation between the opening of the orifice passage and partition wall to be determined independently. 
     The thickness of the elastic film and the diameter of the partition plate are not specially limited but can be selected suitably in accordance with the damping characteristics thereof. Varying the thickness and diameter mentioned above enables a characteristics tuning operation to be carried out easily. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will be described in detail with reference to the following figures, wherein: 
     FIG. 1 is a longitudinal sectional view showing a first mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 2 is a longitudinal sectional view of the same embodiment taken along a different plane; 
     FIG. 3 is a sectional view showing a partition constituting a principal portion of the embodiment and separated from a vibration isolating base member; 
     FIG. 4 is a longitudinal sectional view showing a second mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 5 is a longitudinal sectional view showing a third mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 6 is a longitudinal view of the same embodiment taken along a different plane; 
     FIG. 7 is a longitudinal sectional view showing a fourth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 8 is a longitudinal sectional view showing a fifth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 9 is a longitudinal sectional view showing a sixth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 10 is a longitudinal sectional view of the same embodiment taken along a different plane; 
     FIG. 11 is a longitudinal sectional view of a seventh mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 12 is a longitudinal sectional view of an eighth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 13 is a longitudinal sectional view of the same embodiment taken along a different plane; 
     FIG. 14 is a longitudinal sectional view of a ninth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 15 is a longitudinal sectional view of a tenth mode of embodiment of the liquid sealed type vibration isolator according to the first-mentioned invention; 
     FIG. 16 is a longitudinal sectional view showing a first mode of embodiment of the liquid sealed type vibration isolator according to the second-mentioned invention; 
     FIG. 17 is a longitudinal sectional view of the same vibration isolator taken along a different plane; 
     FIG. 18 is a plan view of a partition of the same vibration isolator; 
     FIG. 19 is a plan view of a partition plate of the same vibration isolator; 
     FIG. 20 is a plan view of an elastic film of the same vibration isolator; 
     FIG. 21 is a longitudinal sectional view showing a second mode of embodiment of the liquid sealed type vibration isolator according to the second-mentioned invention; 
     FIG. 22 is a longitudinal sectional view of the same vibration isolator taken along a different plane; 
     FIG. 23 is a plan view of a partition of the same vibration isolator; 
     FIG. 24 is a plan view of a partition plate of the same vibration isolator; 
     FIG. 25 is a plan view of an elastic film of the same vibration isolator; 
     FIG. 26 is a sectional view showing an example of a liquid sealed type vibration isolator of the related art; 
     FIG. 27 is a sectional view showing another example of a liquid sealed type vibration isolator of the related art; and 
     FIG. 28 is a sectional view showing still another example of a liquid sealed type vibration isolator of the related art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the liquid sealed type vibration isolator according to the present invention will now be described with reference to the drawings. The present invention is not limited to these embodiments. 
     FIG. 1 shows a first mode of embodiment of the liquid sealed type vibration isolator according to a first invention, and FIG. 2 is a longitudinal sectional view of the same vibration isolator taken along a different line, FIG. 3 being a sectional view of a principal portion of the same vibration isolator. 
     As shown in the drawings, a liquid sealed type vibration isolator  1  according to the present invention includes an upper metal fixing member  2  secured to a vibration generating member, such as an engine, a lower metal fixing member  3  secured to a body, a vibration isolating base member  4  interposed between and connecting together these two metal fixing members  2 ,  3  and formed of an elastic body of a rubber-like material, a diaphragm  6  provided on the side of the lower metal fixing member  3  so as to be opposed to the vibration isolating base member  4 , forming a liquid chamber  5 , in which a liquid is sealed, between the diaphragm  6  and vibration isolating base member  4  and formed of a rubber film, and a partition  7  dividing the liquid chamber  5  into a main liquid chamber  5   a  on the side of the vibration isolating base member  4  and an auxiliary liquid chamber  5   b  on the side of the diaphragm  6 . 
     The upper metal fixing member  2  is formed flat, to a central portion of which a fixing bolt  9 , by which the metal fixing member  2  is secured to a vibration generating member, such as an engine, is fixed in an upwardly projecting state. A pin  11  for positioning a base end portion of a metal stopper (not shown), which is adapted to prevent and absorb a large vertical displacement of the upper metal fixing member  2 , is also fixed to an upper surface of the same metal fixing member  2 . 
     The lower metal fixing member  3  includes a bottomed cylindrical bottom member  13  having an expanded outer flange  13   a  at an upper end thereof, and a cylindrical trunk portion  14  fastened at a lower end section thereof to the outer flange  13   a  from the outer side thereof. 
     A fixing bolt  15  for securing the lower metal fixing member  3  to the body is fixed to a bottom portion of the bottom member  13 . The cylindrical trunk portion  14  has a lower end flange  14   a  at its lower end portion, and the lower end flange  14   a  and the outer flange  13   a  of the bottomed cylindrical member  13  are adapted to sandwich outer circumferential portions of the diaphragm  6  and partition  7  therebetween. The lower end flange  14   a  is provided at a free end thereof with a fastened portion  16  extended downward, and the outer flange  13   a  of the bottomed cylindrical member  13  is inserted into the inner side of the fastened portion  16 , the fastened portion  16  being caulked to the outer flange  13   a  so as to enclose the latter, whereby the fastened portion  16  is in a cross-sectionally C-shaped condition. An upper end section of the cylindrical trunk portion  14  is bent inward, and an inner end of a resultant bent section  17  is extended to a position beyond a radially inner end of an orifice  18 , which will be described later, and buried in the vibration isolating base member  4 . 
     In the vibration isolating base member  4 , an elastic body of a rubber-like material is formed in the shape of an umbrella to constitute a rubber body portion the upper and lower end sections of which are vulcanization bonded to the upper metal fixing member  2  and the cylindrical trunk portion  14  of the lower metal fixing member  3  respectively, the lower end section of the base member  4  also enclosing the bent portion  17  at the upper end section of the cylindrical trunk portion  14 . A lower surface of the part of the vibration isolating base member  4  which is below the bent portion  17 , i.e. a liquid chamber-side circumferential portion of the vibration isolating base member  4  is provided with a flat surface section  19 , in which an annulalr groove  20  for press fitting or inserting thereinto an upper end portion of the partition  7  which will be described later is formed. The part of the mentioned portion of the lower surface of the vibration isolating base member which is on the radially outer side of this groove  20  defines an upper surface of the orifice which communicates the main and auxiliary liquid chambers  5   a ,  5   b  with each other. The elastic body of a rubber-like material constituting the vibration isolating base member  4  is extended in a thin film state continuously from an outer circumferential edge part of the flat surface section  19  to a lower end of an inner circumferential surface of the cylindrical trunk portion  14  to thereby form a cylindrical liquid chamber-forming rubber portion  22  defining an outer circumferential surface of the orifice. 
     The partition  7  is formed by deep drawing or pressure molding one piece of disc type metal plate into a bent product, and has a disc type central flat portion  23  dividing the liquid chamber  5  into main and auxiliary liquid chambers  5   a ,  5   b . An outer circumferential section of the central flat portion  23  includes a circumferential wall  24  bent upward and stood up, and folded back and extended downward to form a cylindrical inner circumferential surface, which is formed of a vertical wall surface, of the orifice, and a flange  26  extending radially outward from a lower end of the circumferential wall  24  to form a bottom surface of the orifice. 
     An outer end portion of the flange  26  of the partition  7  is caulked to a fastened portion  16  of the lower metal fixing member  3 . A folded portion  27  at an upper end section of the circumferential wall  24  is extended to a position higher than the upper surface of the orifice  18 , and this extended end portion is positioned by being press fitted or inserted into the groove  20  of the vibration isolating base member  4 . 
     The outer circumferential wall  24  defining the inner circumferential surface of the orifice is provided with openings  28 ,  29  opened into the main and auxiliary liquid chambers  5   a ,  5   b . In order to prevent these openings  28 ,  29  from being short-circuited, a part of a circumferential portion of the liquid chamber-forming rubber portion  22  joined to the vibration isolating base member  4  is provided with a partition wall  30 , which is adapted to shut off the two openings  28 ,  29  from each other, in such a manner that the partition wall  30  is integral with the vibration isolating base member  4 . 
     Owing to this arrangement, the flange  26 , circumferential wall  24 , liquid chamber-forming rubber portion  22 , and flat surface section  19  of the liquid chamber-forming inner circumferential edge portion of the vibration isolating base member  4  form the bottom surface, inner circumferential surface, outer circumferential surface and upper surface respectively of the orifice, and these surfaces are joined together in a liquid-tight condition to form the cross-sectionally rectangular orifice  18  which communicates the main and auxiliary liquid chambers  5   a ,  5   b  with each other. 
     The diaphragm  6  has an elastic film  6   a  of a flexible rubber-like material, and an annular outer circumferential reinforcing metal member  25  an inner end portion of which is buried firmly in an outer circumferential portion of the elastic film  6   a , an outer end portion of the outer circumferential reinforcing metal member  25  being placed on the outer flange  13  of the bottom member  13 . The inner end portion of the outer circumferential reinforcing metal  25  is bent and extended upward, and the resultant bent extended portion  32  is enclosed with the rubber member  33  integral with the diaphragm. This bent extended portion  32  is engaged with the inner side of a lower portion of the circumferential wall  24  of the partition  7 . An air chamber  38  is formed between the diaphragm  6  and bottom member  13 . 
     In order to assemble this vibration isolator  1 , the cylindrical trunk portion  14  is set in a liquid tank with the lower end opened portion thereof directed upward, and the partition  7  is inserted into this opened portion, the folded portion  27  at the inserting free end section of the circumferential wall  24  being press fitted or elastically inserted into the groove  20  of the vibration isolating base member  4 . The diaphragm  6  is then fixed to the resultant product, and a combination of these parts is taken out into the atmosphere. After the residual liquid on this product has been removed, the fastened portion  16  is caulked to complete the assembling operation. 
     In this assembling operation, the upper end portion of the circumferential wall  24  of the partition  7  is put in an engaged state with respect to the groove  20  of the vibration isolating base member  4  by pressure fitting or inserting the former into the latter, so that the radial and vertical positioning of the partition  7  can be done with a high accuracy. Consequently, the cross-sectional area of the orifice  18  enclosed with the partition  7 , vibration isolating base member  4  and liquid chamber-forming rubber portion  22  can be set to a desired level, and excellent vibration damping characteristics can be obtained. 
     FIG. 4 shows a second mode of embodiment of the first-mentioned invention, in which main parts of the construction identical with that of the corresponding parts of the above-described first mode of embodiment are designated by the same reference numerals. 
     In this mode of embodiment, an opening  34  is formed when a dynamic spring constant in a high-frequency region (especially, an engine noise region) requires to be reduced, in a central flat portion  23  of a partition  7 , and an elastic film  8  of a rubber-like material is vulcanization bonded to the partition  7  so as to cover the opening. Owing to the effect of this elastic film  8 , the dynamic spring constant in the high-frequency region (especially, an engine noise frequency) can be reduced. The construction and effects of the parts other than those referred to above are identical with those of the corresponding parts of the first-mentioned embodiment. 
     FIG. 5 shows a third mode of embodiment of the first-mentioned invention, and FIG. 6 a longitudinal sectional view of the same embodiment taken along a different plane, the main parts of this embodiment the construction of which is identical with that of the corresponding parts of the above-described embodiment being designated by the same reference numerals. 
     The vibration isolator  1  of this mode of embodiment is formed by utilizing as orifice-forming members a flat surface portion  19  and liquid chamber-forming rubber portion  22  of the vibration isolating base member, partition  7  and an outer circumferential reinforcing metal member  25  of a diaphragm. 
     The partition  7  is obtained by pressing or deep drawing one piece of disc type metal plate into a bent product, which has a shape of a tray and includes a disc type central flat portion  23 , and a circumferential wall  24  formed in a bent state so as to extend upward from an outer circumferential part of the flat portion  23  and define an upper half of an inner circumferential surface of the orifice. An upper end portion of the circumferential wall  24  extends to a position higher than the flat surface portion  19  of a liquid chamber-side circumferential edge section of the vibration isolating base member  4 , and a resultant upwardly extended portion  24   a  is press fitted or inserted into an annular groove  20  formed in the vibration isolating base member  4 , whereby the partition is positioned. The circumferential wall  24  is provided with an opening  28  therethrough which communicates the main liquid chamber  5   a  and orifice  18  with each other. 
     An inner end portion of the outer circumferential reinforcing metal member  25  of the diaphragm  6  is bent and extended upward, and a resultant bent and extended portion  32  is covered at its circumferential part with a rubber member  33 , via which an upper end of the bent and extended portion  32  is elastically engaged with a lower surface (on the side of the diaphragm) of the central flat portion  23  of the partition  7 . The bent extended portion  32  is provided with an opening  29  therethrough which communicates the orifice  18  and auxiliary chamber  5   b  with each other. The outer circumfential reinforcing metal member  25  of the diaphragm  6  constitutes a bottom surface of the orifice, and an outer end portion of the reinforcing metal member is caulked to a fastened portion  16  of the lower metal fixing member  3 . The construction of the other parts is substantially identical with that of the corresponding parts of the first embodiment. 
     In order to assemble this vibration isolator, a cylindrical trunk portion  14  is set in a liquid tank with a lower end opened portion thereof directed upward in the same manner as in the first mode of embodiment, and the partition  7  is inserted into the opened end portion. A free end portion (extended portion  24   a ), with respect to the direction of the insertion of the partition, of the circumferential wall  24  is then press fitted or inserted into the groove  20  of the vibration isolating base member  4 , and the diaphragm  6  is fixed. The resultant product is then taken out into the atmosphere, and the residual liquid is regulated, the fastened portion  16  being then caulked to complete the assembling work. 
     In this case, the partition  7  is formed to a simple tray-like shape in which the circumferential wall  24  stands up on an outer circumferential part of the central flat portion  23 . Therefore, the partition  7  has various advantages, i.e., it has a simple construction, and is molded easily. Moreover, the partition can be positioned by merely press fitting or inserting the upper end extended portion  24   a  of the circumferential wall  24  thereof into the groove  20  of the vibration isolating base member  4 , and can easily set the orifice  18  having a desired cross section. 
     FIG. 7 shows a fourth mode of embodiment of the first-mentioned invention, and the main parts thereof the construction of which is identical with that of the corresponding parts of the above-described modes of embodiments are designated by the same reference numerals. 
     In the vibration isolator  1  of the fourth embodiment, an opening  34  is formed in a central flat portion  23  of the partition  7 , and an elastic film  8  is vulcanization bonded to the partition so as to cover the opening  34 , the vibration isolator being made capable of effectively reducing a dynamic spring constant in a high-frequency region (especially, an engine noise region) by an operation of the elastic film  8 . The construction and effects of the other parts are identical with those of the corresponding parts of the above-described third mode of embodiment. 
     FIG. 8 is a longitudinal sectional view showing a fifth embodiment of the first-mentioned invention, the main parts the construction of which is identical with that of the corresponding parts of the above-described modes of embodiments are designated by the same reference numerals. 
     In the vibration isolator  1  of the fifth embodiment, an opening  34  is formed in a central flat portion  23  of a partition  7 , and an upper end of a bent portion  32  of an outer circumferential reinforcing metal member  25  of the diaphragm  6  and the partition  7  sandwich an elastic film  8  so as to cover the opening, to thereby enable a dynamic spring constant in a high-frequency region (especially, an engine noise region) to be reduced effectively. The construction and effects of the other parts are identical with those of the corresponding parts of the third mode of embodiment. 
     FIG. 9 is a longitudinal sectional view showing a sixth embodiment of the first-mentioned invention, and FIG. 10 a longitudinal sectional view of the same embodiment taken along a different plane. In this embodiment, the structural parts identical with those of the above-described embodiments are also designated by the same reference numerals. 
     In the sixth embodiment, a cross-sectionally rectangular orifice  18  is formed by a liquid chamber-forming rubber portion  22  defining an outer circumferential surface of the orifice, a partition  7  defining an upper surface thereof, and an outer circumferential reinforcing metal member  25  of a diaphragm  6  which defines an inner circumferential and bottom surfaces thereof. 
     The partition  7  is formed by pressing or deep drawing one piece of metal plate into tray-like structure including a disc type central flat portion  23 , and a circumferential annular wall  24  standing up from an outer circumferential section of the central flat portion  23 . 
     The outer circumferential section  24  of this partition  7  is press fitted into an inner circumferential section of the liquid chamber-forming rubber portion  22 , and an upper end thereof is engaged with the flat surface portion  19  of a liquid chamber-side circumferential edge section of a vibration isolating base member  4 . 
     An outer circumferential reinforcing metal member  25  of the diaphragm  6  includes a ring-shaped bottom portion  25   a  caulked at an outer end section thereof to a fastened portion of a lower metal fixing member  3 , and a cylindrical portion  32  extended in a bent state and standing up from an inner end of the bottom portion and forming an inner circumferential surface of the orifice, an upper end section of the bent extended portion  32  being press fitted or inserted in an annular groove  41  of a rubber member  40  annularly vulcanization bonded to a lower surface of the central flat portion  23  of the partition  7 . Owing to this arrangement, joint surfaces of the partition  7  and the outer circumferential reinforcing metal member  25  of the diaphragm are sealed, and a space enclosed with these parts and liquid chamber-forming rubber portion  22  functions as the orifice  18 . 
     The central flat portion  23  of the partition  7  is provided at an outer circumferential section thereof with an opening  28  communicating with a main liquid chamber  5   a , while the outer circumferential reinforcing metal member  25  of the diaphragm  6  is provided at an inner circumferential portion  32  thereof with an opening  29  communicating with an auxiliary liquid chamber  5   b . A partition wall  43  for preventing these openings  28 ,  29  from being short-circuited is molded so as to become integral with a part of a circumferential portion of the rubber member  40  vulcanization bonded to a lower surface of the partition  7 . The construction of the remaining parts is identical with the corresponding parts of the first mode of embodiment. 
     In order to assemble this vibration isolator  1 , a cylindrical trunk portion  14  is set in a liquid tank with a lower end opened part thereof directed upward, and an inserting free end section of the partition  7  is engaged with the flat surface portion  19  of the vibration isolating base member  4  as the partition  7  is press fitted into the base member along the liquid chamber-forming rubber member  22 . The diaphragm  6  is then fixed, and an upper end section of the bent extended portion  32  of an inner end part of the outer circumferential reinforcing metal member  25  is press fitted or inserted into the groove  41  of the annular rubber member  40  on the lower surface of the partition  7 . A combination of these parts is then taken out, and the residual liquid is regulated, the fastened portion  16  being thereafter caulked. 
     Although, in this case, the partition  7  is formed by merely standing up the outer circumferential part of the central flat portion  23  and has a simple shape, the circumferential wall  24  thereof is in pressure contact with the liquid chamber-forming rubber portion  22  with the upper end thereof engaged with the flat surface portion  19  of the vibration isolating base member  4 , whereby the radial and vertical positioning of the partition  7  is done. Moreover, the circumferential wall  24  of the partition  7  functions as a rib, and the rigidity of the partition  7  can thereby be secured, so that variation of the cross-sectional area of the orifice due to vibration can also be prevented. Since the outer circumferential reinforcing metal member  25  of the diaphragm  6  includes the bottom portion  25   a , and cylindrical bent extended portion  32  standing up from the inner end of the bottom portion, and has also a simple shape, a molding operation therefor by deep drawing work or pressing work can be carried out easily. 
     FIG. 11 is a longitudinal sectional view showing a seventh mode of embodiment of the first-mentioned invention, in which the main parts the construction of which is identical with that of the corresponding parts in the above-described modes of embodiments are designated by the same reference numerals. 
     In the vibration isolator in the seventh embodiment, an opening  34  is formed in a central flat portion  23  of a partition  7 , and an elastic film  8  is vulcanization bonded to the central flat portion so as to cover the opening, whereby a dynamic spring constant in a high-frequency region (especially, an engine noise region) can be effectively reduced. This elastic film  8  is vulcanization molded so that it becomes integral with a rubber member  40  and a partition wall  43  which are formed on a lower surface of the partition  7 . The construction and effects of the other parts are identical with those of the corresponding parts of the sixth embodiment. 
     FIG. 12 is a longitudinal sectional view showing an eighth mode of embodiment of the first-mentioned invention, and FIG. 13 a longitudinal sectional view of the same embodiment taken along a different plane. The main parts the construction of which is identical with that of the corresponding parts of the above-described modes of embodiments are designated by the same reference numerals. 
     A vibration isolator  1  of the eighth mode of embodiment is basically substantially identical with the vibration isolator of the sixth mode of embodiment, i.e., in the eighth embodiment, a cross-sectionally rectangular orifice  18  is formed of a liquid chamber-forming rubber portion  22  defining an outer circumferential surface of the orifice, a partition  7  defining an upper surface thereof, and an outer circumferential reinforcing metal member  25  of a diapharm which defines an inner circumferential and bottom surfaces thereof. However, the construction of a device for positioning the partition  7 , and that of joint portions of the partition  7  and outer circumferential reinforcing metal member  25  are different from those of the corresponding parts of the sixth mode of embodiment. 
     Concretely speaking, the partition  7  is formed to a tray-like shape in the same manner as in the sixth mode of embodiment. A circumferential wall  24  of the partition is press fitted in an inner curcumferential section of the liquid chamber-forming rubber portion  22 , and an upper end extended part  24   a  thereof is press fitted or inserted into an annular groove  20  formed in a boundary section between a flat surface portion  19  of a liquid chamber-side circumferential part of a vibration isolating base member  4  and the liquid chamber-forming rubber portion  22 , whereby the partition is positioned. An annular groove  45  is further provided in a lower surface of an outer circumferential section of a central flat portion  23  of the partition  7 , and a thin film type rubber member  40  is vulcanization bonded to the partition along the annular groove  45 , the rubber member having a cross-sectionally groove-shaped portion in conformity with the groove  45  of the partition  7 . 
     The construction of an outer circumferential reinforcing metal member  25  of a diaphragm  6  is also identical with that of the same member in the sixth mode of embodiment, and an upper end section of an upwardly bent extended portion  32  of an inner end part thereof is press fitted into an annular groove  40   a  of the rubber member  40  on the lower surface of the partition  7 . owing to this arrangement, joint surfaces of the partition  7  and outer circumferential reinforcing metal member  25  are sealed, and a space enclosed with these parts and liquid chamber-forming rubber portion  22  functions as an orifice  18 . The construction of the other parts is identical with that of the corresponding parts of the sixth mode of embodiment. 
     In order to assemble this vibration isolator  1 , a cylindrical trunk portion  14  is set in a liquid tank with a lower end opened section directed upward, and an inserting free end extended part thereof is press fitted or inserted into the groove  20  of the flat surface portion  19  of the vibration isolating base member  4  as the partition  7  is press fitted into the vibration isolating base member  4  along the liquid chamber-forming rubber portion  22 . A diaphragm is then fixed, and an upper end section of the bent extended portion  32  at an inner end part of the outer circumferential reinforcing metal member  25  is engaged with the groove  40   a  of the rubber member  40  of the partition  7 . The resultant product is taken out into the atmosphere, and the residual liquid is regulated, a fastener portion  16  being caulked to complete the assembling work. 
     Although, in this case, the partition  7  is formed by merely standing up the outer circumferential edge section of the central flat portion and has a simple shape, the outer circumferential wall  24  is in pressure contact with the liquid chamber-forming rubber portion  22  with the upper end part thereof engaged with the groove  20  of the vibration isolating base member  4  in a press fitted or inserted state. Therefore, the radial and vertical positioning of the partition  7  can be done in more desirable manner than in the sixth mode of embodiment. The operation and effects of the other parts are identical with those of the corresponding parts of the sixth mode of embodiment. 
     FIG. 14 is a longitudinal sectional view showing a ninth mode of embodiment of the first-mentioned invention, in which the main parts the construction of which is identical with that of the corresponding parts of the above-described modes of embodiments are designated by the same reference numerals. 
     In the ninth mode of embodiment, an opening  34  is formed in a central flat portion  23  of the partition  7  with an elastic film  8  vulcanization bonded to the partition so as to cover the opening  34  in the same manner as in the seventh mode of embodiment. Accordingly, a dynamic spring constant in a high-frequency region (especially, an engine noise region) can be effectively reduced. This elastic film  8  is vulcanization molded so that the film becomes integral with a rubber member  40  and a partition wall  43  which are on a lower surface of the partition  7 . The construction and effects of the other parts are identical with those of the corresponding parts of the eighth mode of embodiment. 
     FIG. 15 is a longitudinal sectional view showing a tenth mode of embodiment of the first-mentioned invention, in which the constituent parts the construction of which is identical with that of the corresponding parts of the above-described modes of embodiment are also designated by the same reference numerals. 
     In the vibration isolator of the tenth mode of embodiment, an orifice  18  is formed of a liquid chamber-forming rubber portion  22  defining an outer circumferential surface of the orifice, a liquid chamber-side flat surface portion  19  of a vibration isolating base member  4  which defines an upper surface thereof, a partition  7  defining an inner circumferential surface thereof, and an outer circumferential reinforcing metal member  25  of a diaphragm  6  which defines a bottom surface thereof. This mode of embodiment differs from the first mode of embodiment in the following points only. The outer circumferential reinforcing metal member  25  defines the bottom surface of the orifice. The partition  7  does not have a lower end flange. A lower end of a vertical circumferential wall  24  is engaged with an upper surface of the outer circumferential reinforcing metal member  25 . The construction of the other portions is identical with the corresponding portions of the first mode of embodiment. 
     Concretely speaking, the partition  7  is formed by bending one piece of disc type metal plate by deep drawing or pressure molding, and includes a central flat portion  23 , and a cylindrical circumferential wall  24  constituting a vertical wall surface and formed by bending an outer circumferential part of the central flat portion  23  upward, and then folding back the upwardly extending part downward, a lower end of this circumferential wall  24  being elastically engaged with a rubber member  33  in which the outer circumferential reinforcing metal member  25  is buried. 
     The partition  7  in this case is press fitted or inserted in a groove of a vibration isolating base member  4 , and a lower end of the partition is elastically engaged with the outer circumferential reinforcing metal member  25  of the diaphragm, so that the radial and vertical positioning of the partition can be done with a high accuracy. 
     As described above, the first-mentioned invention has the following advantages. Since a partition press fitting or inserting structure with respect to a groove, or a surface engaging structure therefor is utilized in a joint portion between the partition  7  and the other orifice-forming member with the simplification of the construction of the orifice forming partition and the facilitation of a partition molding process achieved, the positioning of the partition and the other orifice-forming member can be done easily. 
     Next, the modes of embodiments of the liquid sealed type vibration isolator of the second-mentioned invention will be described with reference to the drawings. 
     FIG. 16 is a longitudinal sectional view showing a first mode of embodiment of the liquid sealed type vibration isolator of the second-mentioned invention, FIG. 17 a longitudinal sectional view of the same vibration isolator taken along a different plane, FIG. 19 a plan view of a partition, and FIG. 20 a plan view of an elastic film. 
     As shown in the drawings, the basic construction of the liquid sealed type vibration isolator of this invention is identical with that of the above-described first-mentioned invention. The parts the construction of which is identical with that of the corresponding parts of the first-mentioned invention are designated by the same reference numerals, and the detailed descriptions thereof are omitted. The vibration isolator of the second-mentioned invention generally has the following construction. 
     This vibration isolator includes an upper metal fixing member  2  secured to a vibration generating member, such as an engine, a lower metal fixing member secured to a body, a vibration isolating base member  4  formed of an elastic member of a rubber-like material connecting these two metal fixing members  2 ,  3  together, a diaphragm  6  provided on the lower metal fixing member  3  so as to be opposed to the vibration isolating base member  4 , and forming a liquid chamber  5  between the diaphragm and vibration isolating base member  4 , and a partition  7  dividing the liquid chamber  5  into main and auxiliary liquid chambers  5   a ,  5   b.    
     A fixing bolt  9 , and a pin  11  for positioning a large displacement preventing metal stopper are fixed to the upper metal fixing member  2 . The lower metal fixing member  3  includes a bottom member  13  having an outer flange  13   a  at an upper end section thereof and a fixing bolt  15  at a bottom section thereof, and a cylindrical trunk portion  14 . A lower end flange  14   a  of the cylindrical trunk portion  14  and the outer flange  13   a  of the bottom member  13  are fastened together by caulking. An outer circumferential portion of the diaphragm  6  is caulked to this fastened portion  16 . 
     The vibration isolating base member  4  is formed of an elastic body of a rubber-like material having an umbrella-like shape, and vulcanization bonded at an upper portion thereof to the upper metal fixing member  2 , and at a lower circumferential portion thereof to the cylindrical trunk portion of the lower metal fixing member  3 . An inner end section of an upper end bent part  17  of the cylindrical trunk portion  14  is extended inward to a position beyond an inner circumferential surface of an orifice  18  and buried in the vibration isolating base member  4 . A lower surface, i.e. a liquid chamber-side circumferential edge section of the vibration isolating base member  4  is formed as a flat surface portion  19 , with which an elastic film of the partition  7  which will be described later is engaged. The elastic body of a rubber-like material of the vibration isolating base member  4  is extended in a thin film state from an outer circumferential edge section of the flat portion  19  thereof to a lower end of an inner surface of the cylindrical trunk portion  14  to form a cylindrical liquid chamber-forming rubber portion  22 . 
     In the case of this invention, the partition  7  is formed of a cylindrical partition plate  70 , and an elastic film  80  formed to a diameter larger than that of an upper cylindrical portion  71  of the partition plate  70  and formed of a disc type elastic body of rubber closing a central opening  72  of the partition plate. 
     As shown in the drawings, a lower end portion of the partition plate  70  is bent radially outward to form a flange  73 , which is caulked to a fastened portion  16  of the lower metal fixing member  3 . The part of the partition plate  70  which is lower than a vertically intermediate section thereof is expanded to form a stepped portion  74 , which defines a bottom surface of the orifice, and a larger-diameter portion  75  lower than the stepped portion  74  is engaged under pressure with a liquid chamber-forming rubber portion  22 . The partition plate  70  is provided at two portions of a circumferential section thereof with a recess  51  and a through hole  52  for communicating the orifice  18  with the main and auxiliary chambers  5   a ,  5   b  respectively. 
     The elastic film  80  is adapted to reduce a dynamic spring constant in a high-frequency region (especially, an engine noise region), and formed in the shape of a disc and engaged at an upper edge part of an outer circumferential portion thereof with a flat surface portion  19  of the vibration isolating base member  4 . The elastic film  80  is provided in its lower surface with a positioning groove  81  extending in the direction of the whole circumference thereof as shown in FIG. 20, and the upper cylindrical portion  71  of the partition plate  70  is press fitted or inserted in the groove  81 . 
     The elastic film  80  is provided at a part of an outer circumferential edge portion thereof with a recess  37  correspondingly to the recess  51  of the partition plate  70 , and this recess  37  constitutes an opening communicating the main liquid chamber  5   a  and orifice  18  with each other. The elastic film  80  is also provided in an outer circumferential surface thereof with a lateral hole  39  correspondingly to the through hole  52  of the partition plate  70 , and this lateral hole  39  and the through hole  52  of the partition plate  70  constitute an opening communicating the auxiliary liquid chamber  5   b  and orifice  18  with each other. 
     Between the recess  37  and lateral hole  39  of the elastic film  80 , a partition wall  43  of a rubber-like material for preventing the short-circuiting of an orifice-communicating opening is molded so that the partition wall  43  is integral with the elastic film  80  and projects outward from a circumference thereof. 
     The diaphragm  6  has an elastic film  6   a  of a flexible rubber-like material, and an inner end portion of an annular outer circumferential reinforcing metal member  25  is buried firmly in an outer circumferential portion of the elastic film  6   a , an outer end portion of this outer circumferential reinforcing metal member  25  being placed on the outer flange  13   a  of the bottom member  13 . An air chamber  38  is formed between the diaphragm  6  and bottom member  13 . 
     In order to assemble this vibration isolator  1 , the partition is first assembled by press fitting or inserting the upper cylindrical portion  71  of the partition plate  70  into the groove  81  in the lower surface of the elastic film  80 , and the lower end opened section of the cylindrical trunk portion  14  of the metal fixing member  3  is then set in an upwardly directed state in a liquid tank, the partition  7  being inserted therein with the elastic film  80  brought into contact with the flat surface portion  19  of the vibration isolating base member  4 . The diaphragm  6  is then fixed, and the resultant product is taken out into the atmosphere, the residual liquid being regulated. The fastened portion  16  is then caulked to complete the assembling work. 
     In this assembled product, a space enclosed with the outer circumferential surface  80   a  of the elastic film  80 , stepped portion  74  of the partition plate  70 , liquid chamber-forming rubber portion  22  and the flat surface portion  19  of the liquid chamber-side circumferential surface of the vibration isolating base member  4  functions as the orifice  18 . In this case, the elastic film  80  is engaged at the groove  81  in the lower surface thereof with the partition plate  70 , whereby the elastic film  80  is radially positioned. Since the elastic film  80  is engaged at the upper end thereof with the flat surface portion  19  of the vibration isolating base member  4 , and at the lower surface thereof with the stepped portion  74  of the partition plate  70 , it is also positioned vertically. Consequently, the cross-sectional area of the orifice  18  formed by these members is set to a desired level, and excellent vibration damping characteristics are obtained. 
     FIG. 21 is a longitudinal sectional view of a liquid sealed type vibration isolator showing a second mode of embodiment of the second-mentioned invention, FIG. 22 a longitudinal sectional view of the same vibration isolator taken along a different plane, FIG. 23 a plan view of a partition, FIG. 24 a plan view of a partition plate, and FIG. 25 a plan view of an elastic film. The main parts the construction of which is identical with that of the corresponding parts of the above-described modes of embodiments are designated by the same reference numerals. 
     As shown in FIG. 23, a partition  7  in this mode of embodiment is identical with that in the first mode of embodiment in that it is formed of a cylindrical partition plate  70  and a disc type elastic film  80  but the shape of a hole for positioning the elastic film  80  and that of an upper portion, which is inserted into this hole, of the partition plate  70  are different from those of the corresponding parts of the first embodiment. 
     Namely, as shown in FIG. 24, an upper cylindrical portion  71  of the partition plate  70  is provided at an upper end thereof with an upwardly extended portion  71   a , while the elastic film  80  is provided correspondingly to the extended portion  71   a  with a slit type through hole  83  extending from a lower surface of an outer circumferential edge portion of the elastic film  80  to an upper surface thereof. After the upper cylindrical portion  71  of the partition plate  70  has been press fitted or inserted into this through hole  83 , the extended portion  71   a  at the upper end of the upper cylindrical portion  71  is bent, and the bent extended portion  71   a  and an intermediate stepped portion  74  of the partition plate  70  sandwich the elastic film  80  therebetween, the resultant product being caulked, whereby the elastic film  80  is fixed to the partition plate  70 . 
     The diameter of an outer end of the bent extended portion  71   a  is set equal to the outer diameter of a lower large-diameter portion  75  of the partition plate  70 , and an outer end section of the bent extended portion is formed so that it is press fitted into an inner circumferential surface of a liquid chamber-forming rubber portion  22 . An upper surface of the bent extended portion  71   a  is adapted to be engaged with a liquid chamber-side flat surface portion  19  of a vibration isolating base member  4 . 
     In this mode of embodiment, a recess  54  is formed in a liquid chamber-side portion of the vibration isolating base member  4 , and used as an opening communicating a main liquid chamber  5   a  and an orifice  18  with each other. A through hole  55  is formed in an elastic film-passing portion of the partition plate  70  which is higher than the stepped portion  74  thereof, and a recess  56  is formed correspondingly to this through hole so as to extend from an outer circumferential side of the elastic film to a lower surface thereof. The recess  56  and the through hole  55  of the partition plate  70  form an opening communicating an auxiliary liquid chamber  5   b  and orifice  18  with each other. 
     Since the construction of the remaining portions of the partition plate  70  and elastic film  80  and that of the parts other than these are identical with that of the corresponding portions and parts of the first mode of embodiment, the descriptions thereof will be omitted. 
     In the structure of the second embodiment, a positioning operation is carried out by passing the upper end portion of the partition plate  70  through the through hole  83  provided in an outer circumferential portion of the elastic film  80 , the radial positioning (centering) of the elastic film  80  can be done easily. Since the elastic film  80  is sandwiched in the direction of height (vertically) between the bent extended portion  51  and stepped portion  74  of the partition plate  70  and caulked, the combining of the partition plate  70  and elastic film  80  together can be done easily. 
     A few more sentences will be added. In any of the above modes of embodiments, the thickness of the rubber of the elastic film  80  may be set suitably in accordance with the required damping characteristics, and the invention is not limited to the illustrated modes of embodiments in this regard. 
     As is clear from the above description, the providing of an elastic film on a partition for the purpose of reducing a dynamic spring constant in a high-frequency region is done according to the second-mentioned invention by forming one cylindrical partition plate and a disc type elastic film separately, forming a positioning bore in a circumferential portion of a lower surface of the elastic film, and press fitting or inserting an upper portion of the partition plate into this bore. Therefore, a step, such as a bonding agent application step becomes unnecessary, and the dimensions of a metal vulcanization mold for the elastic film are reduced. This enables the partition plate and elastic film to be manufactured advantageously at a low cost.