Abstract:
A two-chamber engine mount, especially for motor vehicles, includes a housing having an interior accommodating a supporting spring made of an elastomeric material dividing the interior of the housing into a working chamber and a compensating chamber closed off from the surroundings by an elastomeric diaphragm. The working chamber and the compensating chamber are filled with a hydraulic fluid and are connected to each other through an overflow passage. At least one plunger is configured as a radial stop in the compensating chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of copending International Application No. PCT/EP99/03161, filed May 7, 1999, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a two-chamber engine mount, especially for motor vehicles, including a housing having an interior accommodating a supporting spring made an elastomeric material dividing the interior into a working chamber and a compensating chamber closed off from the surroundings by an elastomeric diaphragm, the working chamber and the compensating chamber being filled with a hydraulic fluid and connected to each other through an overflow passage. 
     One such two-chamber engine mount is known from European Patent Application 0 253 373 A1. In that known two-chamber engine mount a supporting spring of an elastomeric material is accommodated in a cylindrical housing. The supporting spring divides the interior of the housing into a working chamber and a compensating chamber disposed at an outer periphery of the supporting spring. The two chambers are connected through an overflow passage. A mount core which is vulcanized in place in the supporting spring is to be secured to an engine. A flange which is applied to the mount core clasps the outside of the housing with a clearance and serves as an axial stop. The flange is an additional component which complicates assembly and simultaneously increases the weight and overall dimensions of the mount. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a two-chamber engine mount, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which is further developed so that a radial stop is provided for a supporting spring while achieving compact dimensions and facilitated assembly. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a two-chamber engine mount, especially for motor vehicles, comprising a housing having an interior; a supporting spring of an elastomeric material disposed in the interior and dividing the interior into a working chamber and a compensating chamber to be filled with a hydraulic fluid; an overflow passage interconnecting the working chamber and compensating chamber; an elastomeric diaphragm closing off the compensating chamber from the surroundings; and at least one plunger disposed in the compensating chamber as a radial stop. 
     The plunger provided in accordance with the invention improves the acoustic response in the higher frequency range, more particularly in the frequency range between 80 and 160 Hz. The plunger results in a considerable reduction in the dynamic stiffness in the desired frequency range, often down to a value below that of the static stiffness. This reduction is termed high-frequency isolation. At the same time the plunger acts as a radial stop. 
     In the two-chamber engine mount in accordance with the invention the working chamber is advantageously defined by the supporting spring and the housing. The compensating chamber surrounds the working chamber and is defined by the supporting spring, the housing and an elastomeric diaphragm. Such a mount is also termed a “pot mount”. 
     In accordance with another feature of the invention, the plunger is integral with or formed as one piece with the supporting spring. The integral configuration facilitates producing and assembling the two-chamber engine mount in accordance with the invention. The plunger is vulcanized in place with the mount core in a single operation during production. 
     In accordance with a further feature of the invention, the plunger is separate from the supporting spring on an outer wall surface of the compensating chamber. Although the plunger is produced as a separate component in this embodiment, placing it at the outer wall surface of the compensating chamber is speedy and facilitated. 
     In accordance with an added feature of the invention, there is provided a combination of these two plunger configurations. In this case a plunger configured integrally with the supporting spring cooperates with a plunger disposed at the outer wall surface of the compensating chamber. 
     In all of the embodiments the plunger or plungers achieve high-frequency isolation. A plunger gap formed between the plunger and the outer wall surface of the working chamber or the supporting spring or between the two plungers is significant in this regard. The dimensions of this plunger gap are a factor significantly characterizing the high-frequency isolation. 
     The parameters referred to as plunger diameter, plunger gap and gap length, which are significant in dictating the dynamic response, are freely selectable by placing the plunger in the compensating chamber. When use is made of a plunger disposed at the supporting spring, the plunger gap is formed between the plunger and the outer wall surface of the compensating chamber. This plunger gap is independent of the position of the plunger, thus achieving a dynamic response independent of the settlement of the hydro-elastic mount. 
     In accordance with an additional feature of the invention, the plunger is shiftingly guided at the outer wall surface in the direction of a centerline through the engine mount. This enables stops or fastener elements for the plunger to be eliminated and thus facilitates assembly and reduction of weight without detriment to the dual function of the plunger as a radial stop and for high-frequency isolation. 
     In accordance with yet another feature of the invention, the plunger includes a leaf spring vulcanized in place to boost the radial stiffness. The leaf spring may be simply vulcanized in place in the plunger to enable the radial stiffness to be “tuned” to the existing boundary conditions. 
     In accordance with yet a further feature of the invention, there is provided at least one axial stop to define the movement of the supporting spring in the direction of its centerline. The axial stop prevents prohibitively large movements of the supporting spring in avoiding the engine mount from being damaged or ruined. 
     In accordance with yet an added feature of the invention, the axial stop is configured as a protruding portion of a bottom of the housing, requiring no additional components, thus simplifying production and assembly of the two-chamber engine mount in accordance with the invention. 
     In accordance with yet an additional feature of the invention, the axial stop is rigidly connected to the housing from which it protrudes radially. The outer diameters of the two-chamber engine mount in accordance with the invention are thus maintained compact. 
     Advantageously, both axial stops are combined in such a way that they define the movements of the supporting spring in two opposing directions, thus preventing prohibitive movements of the supporting spring in the direction of both the engine and the vehicle body. 
     Advantageously the first axial stop cooperates with a projection configured integrally with the supporting spring, and the second with a plunger configured integrally with the supporting spring. The projection and the plunger may be vulcanized in place in a single operation with the mount core in producing the supporting spring. 
     In accordance with again another feature of the invention, the supporting spring has a gap in which a movable isolation diaphragm is accommodated with clearance. This isolation diaphragm, like the plunger, results in a reduction in the dynamic stiffness in a specific frequency range. 
     Advantageously, the plunger is configured in such a way that it results in a high-frequency isolation in a first frequency range while a high-frequency isolation is achieved in a second frequency range by the isolation diaphragm, thus achieving an improvement in the acoustic response in two frequency ranges that are separate from each other. As an alternative the isolation diaphragm and the plunger may be constructed for a high-frequency isolation in the same frequency range so that the dynamic stiffness is significantly reduced. 
     In accordance with again a further feature of the invention, the isolation diaphragm and the gap are disposed parallel to a centerline of the engine mount. The term “parallel” in this sense is understood to mean that the isolation diaphragm and the gap are oriented perpendicular to the plane which in turn stands perpendicular to the centerline of the engine mount. This embodiment permits a configuration and assembly which is simple. 
     In accordance with again an added feature of the invention, the isolation diaphragm has the shape of a ring segment. The isolation diaphragm and the gap in this embodiment are disposed concentric to the centerline of the engine mount. 
     In accordance with again an additional feature of the invention, the supporting spring forms ridges defining the gap and passages located in-between for fluid actuation of the isolation diaphragm. These ridges assure the stability of the supporting spring. The stability is difficult to achieve with a large full-length opening for fluid actuation of the isolation diaphragm. At the same time the passages between the ridges permit a relatively large surface area fluid actuation of the isolation diaphragm. 
     In accordance with a concomitant feature of the invention, the isolation diaphragm is made of an elastomeric material, a substantially rigid material or a combination of these materials. The isolation diaphragm can be optimally “tuned” to the various boundary conditions by suitably selecting the material therefor. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a two-chamber engine mount, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic, longitudinal-sectional view of a first embodiment of a two-chamber engine mount in accordance with the invention; 
     FIG. 2 is a view similar to FIG. 1, illustrating a second embodiment of the invention; 
     FIG. 3 is a view similar to FIG. 1, illustrating a third embodiment of the invention; 
     FIG. 4 is a cross-sectional view taken along a line IV—IV in FIG. 1, in the direction of the arrows; and 
     FIG. 5 is a cross-sectional view taken along a line V—V in FIG. 1, in the direction of the arrows. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a first embodiment of an engine mount  10   a  in accordance with the invention, including a housing  11  having an interior in which an insert  12  as well as a supporting spring  13  with a mount core  14  vulcanized in place are incorporated. The conical supporting spring  13  divides the interior of the housing  11  into a working chamber  15  and a compensating chamber  16  connected to each other through an overflow passage  17 . The overflow passage  17  has an approximately spiral run along an inner wall surface of the housing  11  through the supporting spring  13 , as a result of which a large length of the overflow passage  17  is assured. 
     The compensating chamber  16  is closed off from the surroundings by an elastomeric diaphragm  18 . A stiffener  19  is provided in order to boost the stability of the supporting spring  13 . 
     In this embodiment, a plunger  20   a  is configured to be integral with or part of the supporting spring  13 . The plunger  20   a  has a leaf spring  21   a  vulcanized in place to boost its radial stiffness. 
     The engine mount  10   a  is secured through the use of studs  22 ,  23  disposed concentrically to a centerline  24  of the engine mount  10   a.    
     An isolation or decoupling diaphragm  30 , which is provided between the working chamber  15  and the compensating chamber  16 , is disposed in a gap  31  in the supporting spring  13 . The manner in which the isolation diaphragm  30  is mounted and acts will be described in detail with reference to FIGS. 4 and 5. 
     Two axial stops  41 ,  42  are provided in order to define the movement of the mount core  14  in the direction of the centerline  24 . The axial stop  41  is configured as a protruding portion of a bottom  43  of the housing  11  and cooperates with a projection  40  of the supporting spring  13 . The other axial stop  42  is rigidly connected to the housing  11 , protrudes radially therefrom and defines the movement of the mount core  14  in the opposite direction. Prohibitively large movements cause the plunger  20   a  to be stopped by the axial stop  42 . 
     The axial stop  42  has an opening  44  for the mount core  14 . The size of the opening  44  is selected in such a way that the mount core  14  does not come into contact with the axial stop  42 . 
     The working chamber  15 , the compensating chamber  16  and the overflow passage  17  are filled with a hydraulic fluid. Any displacement of the mount core  14  relative to the housing  11  changes the volume of the working chamber  15  so that the hydraulic fluid flows through the overflow passage  17 . The hydraulic damping opposes the movement of the mount core  14 . At the same time the hydraulic fluid flows through a plunger gap  38  formed between the plunger  20   a  and the insert  12 . In this case too, hydraulic damping occurs which opposes movement of the mount core  14 . This results in a reduction in the dynamic stiffness, depending on the location and size of the plunger gap  38 . At the same time, the isolation diaphragm  30  moves in the gap  31  which likewise results in a reduction in the dynamic stiffness. 
     As mentioned above, any prohibitively large movement of the mount core  14  is prevented by the axial stops  41 ,  42 . The plunger  20   a  serves as a radial stop. When the mount core  14  is exposed to forces which are not oriented parallel to the centerline, the mount core will radially deflect. Should a prohibitively large radial deflection occur, the plunger  20   a  will come into contact with the insert  12  to oppose any further deflection. The radial stiffness of the plunger  20   a  is boosted by the leaf spring  21  that is vulcanized in place, so that prohibitive deformations or damage to the plunger  20   a  need not be feared. In this configuration the leaf spring  21   a  does not come into contact with the insert  12  since the leaf spring is covered by the supporting spring  13 . It is this coverage that reliably prevents any rattling or similar disturbing noise. 
     Referring now to FIGS. 2 and 3, it is seen that each illustrates a further embodiment of an engine mount  10   b ,  10   c  in accordance with the invention. Components which are like or similar to those illustrated in FIG. 1 are identified by like reference numerals. In order to avoid tedious repetition, reference is made to the description relating to FIG. 1 to explain these components and how they function. 
     The embodiment shown in FIG. 2 provides a plunger  20   b  which is configured integrally with or is part of the supporting spring  13 . This plunger is configured to be smaller than the plunger  20   a  of the embodiment shown in FIG.  1 . The plunger  20   b  has a leaf spring  21   b  vulcanized in place to boost the radial stiffness. 
     In this embodiment a further plunger  25   a  is disposed at an outer wall surface  27  of the compensating chamber  16 . The plunger  25   a  shown in FIG. 2 may be shifted at the outer wall  27  in the direction of the centerline  24  of the engine mount  10   b . The plunger gap  38  is formed between the plungers  20   b ,  25   a.    
     The response of the engine mount  10   b  to loading and the hydraulic damping by the overflow passage  17 , the isolation diaphragm  30  and the plunger gap  38  are the same as already described with reference to FIG.  1 . The further plunger  25   a  is displaced as a function of the fluid flow and the damping parallel to the centerline  24  along the outer wall  27 . The further plunger  25   a  additionally serves together with the plunger  20   b  as a radial stop. 
     Referring now to FIG. 3, there is seen a third embodiment of an engine mount  10   c  making use of a further plunger  25   b  disposed at the outer wall surface  27 . The further plunger  25   b  is provided with a leaf spring  26  that is vulcanized in place to boost the radial stiffness. The plunger gap  38  is formed between the further plunger  25   b  and the supporting spring  13  surrounding the mount core  14 . The further configuration and functioning of the individual components are the same as those in the embodiments shown in FIGS. 1 or  2 . 
     Referring now to FIGS. 4 and 5, there are seen more-detailed illustrations of the way in which the isolation diaphragm  30  is mounted and fluidly actuated. The mounting and functioning are identical to that of the embodiments shown in FIGS. 1 to  3 . 
     The isolation diaphragm  30  and the gap  31  in the supporting spring  13  have the shape of a ring segment and are disposed concentric to the centerline  24 . In order to provide fluid actuation, the supporting spring  13  is provided in the direction of the compensating chamber  16  with a series of passages  32  and ridges  33  located therebetween. The hydraulic fluid comes into contact with the isolation diaphragm  30  through the passages  32 . 
     The side of the supporting spring  13  facing the working chamber  15  forms passages  35  with ridges  34  located therebetween. The passages  35  permit fluid actuation of the isolation diaphragm  30  from the working chamber  15 . 
     Any displacement of the mount core  14  relative to the housing  11  changes the volume of the working chamber  15 , thereby resulting in a difference in pressure between that of the working chamber  15  and that of the compensating chamber  16 . This difference in pressure is effective through the passages  32 ,  35  on the isolation diaphragm  30  and moves the isolation diaphragm  30  radially outwards, when an overpressure exists in the working chamber  15 , until the isolation diaphragm comes into contact with the ridges  33 . This is the position shown in FIG.  5 . If the pressure in the working chamber  15  is less than that in the compensating chamber  16 , the isolation diaphragm  30  is moved radially inwards until it comes into contact with the ridges  35  and the gap  31  is thereby defined by the ridges  33 ,  34 . 
     During low-amplitude movements of the mount core  14 , as occur usually when the engine is idling, the isolation diaphragm  30  isolates vibrations of the mount core  14  from the vehicle body. 
     During higher amplitude movements of the mount core  14 , the hydraulic fluid flows through the overflow passage  17  so that it is thereby hydraulic damped. This hydraulic damping opposes movement of the mount core  14 . The overflow passage  17  communicates through a port  36  with the compensating chamber  16  and through a further port  37  with the working chamber  15 . Depending on the movement of the mount core  14  , the hydraulic fluid flows either from the working chamber  15  into the compensating chamber  16  or vice-versa. 
     The engine mount  10   a ,  10   b ,  10   c  in accordance with the invention permits radial support of the supporting spring by the plungers  20   a ,  20   b ,  25   a ,  25   b  which are provided in the compensating chamber and configured as a radial stop. The plungers  20   a ,  20   b ,  25   a ,  25   b  simultaneously result in a reduction in the dynamic stiffness which enhances the acoustic response of the engine mount  10   a ,  10   b ,  10   c  in accordance with the invention. A further improvement in the acoustic response is achieved by the isolation diaphragm  30 . In addition to this the engine mount  10   a ,  10   b ,  10   c  is simple and cost-effective in production and assembly.