Abstract:
A vibration damping apparatus which is particularly applicable to an automotive engine mount and capable of fully absorbing vibration from vibration generating sources. A sleeve is secured to the automotive engine unit, and a housing is secured to the vehicle body. Once the vibration generated by the automotive engine is transmitted to the sleeve, liquid loaded in a main liquid chamber flows to a sub liquid chamber via a plurality of restricting passages. Vibration is effectively absorbed by the transit resistance against liquid flowing through those restricting passages. Independent of these restricting passages, a cylindrical member is provided which penetrates through the housing and a partition wall block. The cylindrical member is disposed in the path of the restricting passages providing connection between the main and sub liquid chambers. A hollow rotor is rotatably provided, inside of and on the same axial line as the cylindrical member, for opening and closing the restricting passages. When low-frequency vibration is generated, only the restricting passage devoid of the hollow rotor provides connection between the main and sub liquid chambers. Conversely, when high-frequency vibration is generated, those restricting passages each containing the hollow rotor and having a large sectional area are released to provide connection between both chambers thus reliably and effectively absorbing vibrations throughout an extensive range of frequencies.

Description:
This is a continuation of application Ser. No. 08/037,691 filed Mar. 25, 1993, now abandoned, which in turn is a continuation of application Ser. No. 07/770,535 filed Oct. 3, 1991, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vibration damping apparatus which is particularly available for a vehicle engine mount to fully absorb vibration propagated from a variety of vibration generating sources. 
     2. Background information 
     A typical vehicle engine is provided with a vibration damping apparatus serving as the engine mount between the engine unit and the vehicle body. Any conventional vibration damping apparatus is internally provided with a main liquid chamber and a sub liquid chamber respectively being filled with liquid, which are internally connected to each other via a plurality of restricting passages. Whenever vibration of engine is propagated to the vibration damping apparatus, liquid in both chambers passes through these restricting passages so as to absorb vibration by the effect of transit resistance or liquid column resonance in the liquid-filled restricting passages. 
     A typical vehicle engine generates a variety of vibrations including shaking vibration which occurs while the vehicle runs at about 70 kilometers per hour of velocity and idling vibration which occurs while the vehicle runs at an extremely slow velocity such as 5 kilometers per hour for example. 
     Generally, the shaking vibration generates a maximum frequency of 15 Hz, whereas the idling vibration generates 20 through 40 Hz of frequencies, and thus both vibrations are physically different from each other. 
     On the other hand, any of the conventional vibration-proof apparatuses is functionally effective only in a specific range in which the frequencies of the vibration can be determined in accordance with the area and the length of aperture of each limited passage. In other words, any conventional vibration damping apparatus cannot effectively damp and absorb vibration containing frequencies out of the predetermined range. 
     To compensate for this, if any adjustment were applied to such a conventional vibration damping apparatus in order to effectively damp the shaking vibration, then, conversely, it cannot effectively damp the idling vibration, and vice versa. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the invention is to fully solve the technical problems mentioned above by providing a novel vibration damping apparatus which is capable of correctly and fully damping and absorbing vibration throughout an extensive range of frequencies based on a simple structure which permits manufacturers to easily manufacture it. 
     The invention provides a novel vibration damping apparatus which fully absorbs vibration propagated from a variety of vibration sources. In particular, the vibration damping apparatus is ideally suited for the engine mount of a vehicle. 
     The first securing member is connected to either a vibration generating source or a vibration receiving member, while the second securing member is connected to the other one of these two. An elastic member provides connection between the first and second securing members. The elastic member itself is subject to deformation whenever vibration is generated. A main liquid chamber is provided, which uses part of the elastic member to make up its own wall and is connected to a sub liquid chamber via a plurality of restricting passages. 
     Whenever vibration is generated, the vibration is effectively absorbed by the effect of transit resistance or liquid column resonance of liquid in the restricting passages which respectively provide a connection between the main liquid chamber and the sub-liquid chamber. A member which forms a restricting passage is installed in at least one of the plural limited passages, where this member serves as a partition wall separating the main liquid chamber from the sub liquid chamber. A means for controlling the limited passages is provided for at least one of the limited passages. The control member is provided with a cylindrical member having opening, and the control member penetrates through the first securing member and the restricting passage forming member. The restricting passage control member varies the sectional area of the aperture of at least one of the restricting passages so that vibration containing a variety of frequencies can be effectively and fully absorbed. 
     According to the vibration damping apparatus embodied by the invention, vibration propagated from a variety of vibration generating sources is received by a vibration receiving member via an elastic member. Propagated vibration is not only absorbed by the effect of the resistance generated by internal friction of the elastic member, but it is also absorbed by the effect of transit resistance or liquid column resonance of liquid in the limited passages between the main and sub liquid chambers. 
     In particular, since a plurality of limited passages are provided, and at the same time, one or more of these limited passages is connected to a limited-passage control means, vibration containing a variety of frequencies can be properly damped. Specifically, the vibration damping apparatus embodied by the invention can effectively damp vibration in the presence of low-frequency vibration by contracting the sectional area of the aperture of each limited passage. In other words, vibration is fully absorbed by those limited passages having the sectional area of the apertures contracted by the limited-passage control member, or, by those limited passages having a narrow sectional area of apertures without being provided with control members which respectively provide direct connection between the main and sub liquid chambers. 
     When high-frequency vibration is present, the limited passages having a narrow sectional area of aperture clog themselves. To compensate for this, the vibration damping apparatus needs to operate those limited passages having a wide sectional area of aperture. Even when this need arises, according to the vibration damping apparatus embodied by the invention, high-frequency vibration can also effectively be absorbed by expanding the sectional area of the apertures of the limited-passage control member by operating the limited-passage control member itself. 
     The vibration damping apparatus embodied by the invention allocates the limited-passage control member to one or a plurality of limited passages in those situations including the following: a case in which a main liquid chamber and a sub-liquid chamber are connected to each other via a plurality of restricting passages: a case in which either one or a plurality of restricting passage control members is provided for a restricting passage or all the restricting passages; a case in which a main liquid chamber and a plurality of sub-liquid chambers are respectively connected to each other by a plurality of restricting passages, in other words, the case in which a plurality of liquid chambers are connected to each other in series by a plurality of liquid passages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view of a vibration damping apparatus according to a first embodiment of the invention; 
     FIG. 2 is a perspective view of disassembled components of the vibration damping apparatus shown in FIG. 1; 
     FIG. 3 is a sectional view of the vibration damping apparatus taken along the line 3--3 in FIG. 1; 
     FIG. 4 is a sectional view of the vibration damping apparatus taken along the line 4--4 in FIG. 1; 
     FIG. 5 is a sectional view of the vibration damping apparatus shown in FIG. 4 showing an operative state; 
     FIG. 6 is a sectional view of the vibration damping apparatus taken along the line 6--6 in FIG. 1; 
     FIG. 7 is a vertical sectional view of a vibration damping apparatus according to a second embodiment of the invention; 
     FIG. 8 is a perspective view of a partition wall block unit of the vibration damping apparatus according to the second embodiment of the invention; 
     FIG. 9 is a sectional view of the vibration damping apparatus according to the second embodiment in correspondence with those which are shown in FIGS. 4 and 5; 
     FIG. 10 is a sectional view of the vibration damping apparatus according to the second embodiment in correspondence with those which are shown in FIGS. 4 and 5; 
     FIG. 11 is a sectional view of the vibration damping apparatus according to the second embodiment in correspondence with those which are shown in FIGS. 4 and 5; 
     FIG. 12 is a perspective view of disassembled components of a vibration damping apparatus according to a third embodiment of the invention; 
     FIG. 13 is a sectional view of the assembled components shown in FIG. 12; 
     FIG. 14 is a sectional view of a vibration damping apparatus according to the fourth embodiment of the invention; 
     FIG. 15 is a perspective view of disassembled components of a vibration damping apparatus according to a fifth embodiment of the invention; and 
     FIG. 16 illustrates assembled components of the vibration damping apparatus shown in FIG. 15. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 through 6 illustrate a vibration damping apparatus 10 according to a first embodiment of the invention. The vibration damping apparatus 10 has a rectangular housing 12 which itself makes up a securing member on one side of the vibration damping apparatus 10, where the rectangular housing 12 is structured in the block form internally containing hollow domain 14 which extends through the housing 12 in the vertical direction as shown in FIG. 1. 
     The bottom of the hollow domain 14 of the housing 12 substantially makes upa diameter-expanded domain 16 having an expanded inner diameter across a step region 17. A partition wall block 22 is inserted into the diameter-expanded domain 16 in the upward direction from the bottom. The partition wall block 22 is secured to the housing 12 by means of a bottom plate 24 which is secured to the lateral surface of the housing 12. The circumferential edge of a diaphragm 26 is secured between the partition wall block 22 and the bottom plate 24. 
     The hollow domain 14 has slopped inner surfaces at two opposing sides whosedistance apart gradually increases in the upward direction. The external surface of an elastic member 28 is secured to the surface of inner domain 12 vulcanizing means. An extended part 28A vertically extended downward integrally with the elastic member 28, is disposed on the inner surface ofthe hollow domain 14 and the diameter-expanded domain 16. 
     A sleeve 32 is secured to the center of the elastic member 28 to comprise asecuring member on the other side, of the vibration-proof apparatus 10. A plate 34 is installed inside of the elastic member 28 in order to adjust rigidity of the elastic member 28. 
     A plurality of liquid chambers are formed by those components including thehollow domain 14, the elastic member 28, and the diaphragm 26. All the liquid chambers are filled with water or oil. The liquid is separated by the partition wall block 22. A main chamber 36 is formed between the partition wall block 22 and the elastic member 28. A sub-liquid chamber 38is formed between the partition wall block 22 and the diaphragm 26. An air chamber 42 is formed between the diaphragm 26 and the bottom plate 24, where the air chamber 42 can atmospherically be connected as required. 
     For example, the housing 12 is secured to the vehicle body, while sleeve 32is secured to the engine, so as to cause the elastic member 28 to hold the load delivered to the vehicle body from the engine unit. At the same time,the load is also applied to the main liquid chamber 36 in the form of compressive force. 
     As shown in FIGS. 2 and 3, a large groove 44 is provided at the outer periphery of the partition wall block 22. The large groove 44 is U-shaped in the longitudinal direction as shown in FIG. 3, but it has rectangular shape in the longitudinal orthogonal direction as shown in FIG. 4. One endof the large groove 44 is connected to the main liquid chamber 36 via a rectangular opening 46, whereas the other end of the large groove 44 is communicated to an cylindrical hole 48 via a rectangular opening 47. 
     As shown in FIG. 1, the cylindrical hole 48 penetratively extends itself from the external wall of the partition wall block 22 to the internal recess 52 which is formed in the direction of the main liquid chamber 36. Part of the inner circumferential wall of the cylindrical hole 48 is connected to the large groove 44 via the rectangular opening 47. Because of this structure, when the partition wall block 22 is assembled to the housing 12, the external edge of the large groove 44 is blocked by the inner surface member of the diameter-expanded member 16, more particularly, the large groove 44 is blocked by the extended member 28A ofthe elastic member 28. Owing to this arrangement, a restricting passage 54 is formed. An end of the large groove 44 is connected to the main liquid chamber 36 by means of the rectangular opening 46, whereas the other end of the large groove 44 is communicated to the sub-liquid chamber 38 via the cylindrical hole 48. 
     A small groove 56 is formed at a position closer to the sub-liquid chamber 38 than the large groove 44 and in parallel therewith. As shown in FIGS. 2and 4, an end of the small groove 56 is connected to the main liquid chamber 36 via the rectangular opening 46, whereas the other end is connected to the recess 52 via a through-hole 58. In consequence, the small groove 56 forms a restricting passage 59 having a portion of its external wall formed by the diameter-expanded member 16. Both ends of the restricting passage 59 are respectively connected to the main liquid chamber 36 and the sub-liquid chamber 38 via the rectangular opening 46 and the through-hole 58. The longitudinal orthogonal sectional area of therestricting passage 59 is narrower than that of the restricting passage 54. 
     A cylindrical member 62 is inserted in the cylindrical hole 48. As shown inFIG. 1, the cylindrical member 62 penetrates through an insertion hole 90 of the housing 12, and then, a screw member 63 provided on the external circumference of the cylindrical member 62 is engaged with a thread portion provided inside the insertion hole 90 of the housing 12 so that the cylindrical member 62 can be secured to the housing 12. 
     A hollow domain 62A is provided in cylindrical member 62, at a position close to the tip end thereof. Cylindrical member 62 is inserted in the cylindrical hole 48, where the hollow domain 62A has a coaxial, cylindrical hole coaxially being extended from the tip. A rectangular opening 64 is provided on part of the external circumferential surface of the cylindrical member 62. The cylindrical member 62 is secured to the housing 12 in order that the rectangular opening 64 can correctly match the other rectangular opening 47. 
     A rotor 66 is coaxially inserted in the hollow domain 62A. The tip of the rotor 66 is open and has hollow cylindrical form. The interior and the exterior of the rotor 66 are connected to each other by a rectangular through-hole 67 which is formed in part of the wall of the rotor 66. A blocking wall 66A closing the open tip and the opposite side of the rotor 66 is secured to the tip of a rotary shaft 68 which is held by the cylindrical member 62. The other end of the rotary shaft 68 projects from the housing 12 and is connected to an output shaft 71A of motor 71. The motor 71 is secured to the housing via a case 69. A controller 73 controlsthe supply of DC power to the motor 71. A sensor 74 of the controller 73 detects the number of rotations of the engine, vehicle velocity, and frequencies of vibration. The controller 73 controls the rotation of the motor 71 in correspondence with the frequencies to be absorbed. Both ends of a cover member 76 are secured to the tip of the housing 12 in order that the maximum stroke of the sleeve 32 can be controlled. 
     Next, operational features of the vibration damping apparatus according to the first embodiment of the invention are described below. 
     When the vehicle engine generates vibration containing relatively low frequencies, such as shaking vibration with a maximum of 15 Hz, the controller 73 feeds DC power to the motor 71 to cause the through-hole 67 of the rotor 66 to enter into a condition in which it is not matched with the rectangular opening 47 as shown in FIG. 4. As a result, the restricting passage 54 is shut off by the lateral wall of the rotor 66, and as a result, only the restricting passage 59 is connected to the main liquid chamber 36 and the sub-liquid chamber 38. After connecting the restricting passage 59 containing a relatively narrow effective sectional area to the main and sub liquid chambers 36 and 38, variation of pressure in the main liquid chamber 36 caused by the vibrating engine is effectively absorbed by the effect of transit resistance or liquid-column resonance generated in the restricting passage 59. 
     Conversely, when the vehicle engine generates idling vibration containing relatively high frequencies ranging from 20 to a maximum of 40 Hz for example, the restricting passage 59 clogs itself. To compensate for this, the controller 73 feeds DC power to the motor 71 to rotate the rotor 66 upto the position where the through-hole 67 correctly matches the opening 64 shown in FIG. 5. As a result, the through-hole 67 is connected to the rectangular opening 47 to cause the restricting passage 54 to be connectedto the main liquid chamber 36 and the sub liquid chamber 38. As a result, vibration containing relatively high frequencies generated in the main liquid chamber 36 is effectively absorbed by the effect of transit resistance or liquid-column resonance generated in the restricting passage54 having a large effective sectional area. 
     According to the first embodiment, the rotor 66, which has been accommodated inside the cylindrical member 62, is subject to rotation. Since the cylindrical member 62 is inserted into and assembled with the cylindrical hole 48, the rotor 66 securely rotates inside of the cylindrical member 62 to open and close the rectangular opening 47. In consequence, a faulty centering effect caused by incorrect disposition of the rotor 66 in the cylindrical hole 48, and irregular rotation of the rotor 66 can respectively be eliminated. 
     Except for the disposition of the rotor 66 inside of the annular hole via the cylindrical member 62, as far as the cylindrical hole 48 and the rotor66 can correctly be assembled to the predetermined positions, the scope of the first embodiment of the invention is by no means restricted to the structure mentioned above. 
     Next, referring to FIGS. 7 through 11, the vibration damping apparatus according to the second embodiment of the invention is described below. 
     As shown in FIGS. 7 and 8, a vibration damping apparatus according to a second embodiment provides a through-hole 78 on the top of the partition wall block 22. Notch 64 of the cylindrical member 62 has a size capable ofconnecting the through-hole 78 to the hollow domain 62A. Like the rectangular opening 47, the through-hole 78 permits part of the circumferential wall of the cylindrical hole 48 to be communicated with the main liquid chamber 36. However, unlike the rectangular opening 47, the through-hole 78 directly connects the cylindrical hole 48 to the main liquid chamber 36. In addition to the restricting passages 54 and 59, the through-hole 78 itself makes up the third restricting passage, which has an effective sectional area substantially larger than those of other restricting passages and lower transit resistance value. As shown in FIG. 7, in order to connect the through-hole 78 to the main liquid chamber 36, the second embodiment provides opening 79 in part of the interior of the housing 12. 
     Therefore, when the through-hole 67 of the rotor 66 is disposed in the manner shown in FIG. 9, the through-hole 67 does not match either of the rectangular opening 47 and the through-hole 78, then only the restricting passage 59 interconnecting the main and sub-liquid chambers 36 and 38 and having the least effective sectional area can absorb vibration of relatively low frequencies. As shown in FIG. 10, when the through-hole 67 correctly matches the rectangular opening 47, the restricting passage 59 clogs itself. When this condition is present, the other restricting passage 54 effectively absorbs the vibration. Furthermore, as shown in FIG. 11, when the through-hole 67 of the rotor 66 matches the through-hole78, and yet, even when those restricting passages 54 and 59 respectively clog themselves as a result of the occurrence of vibration containing extremely high frequencies like a minimum of 50 Hz for example, the through-hole 78 can securely absorb this vibration. 
     The second embodiment provides a structure with permits the rotor 66 to open and close the rectangular opening 47 and the through-hole 78. In addition, not only does rotor 66 function to fully open and close both therectangular opening 47 and the through-hole 78 but also closes either of them to a halfway position and thus control the half-open sectional areas of the rectangular opening 47 and the through-hole 48. 
     Next, referring to FIGS. 12 and 13, a vibration damping apparatus accordingto a third embodiment of the invention is described below. 
     The third embodiment provides a structure in which the rotor 66 and the rotary shaft 68 are coaxially secured to each other in advance of the overall assembly of the apparatus. More particularly, the rotor 66 and therotary shaft 68 are made of identical metallic material by executing a cutting process or a molding process. Like the preceding embodiments, the third embodiment provides a structure in which the rotary shaft 68 penetrates through the cylindrical member 62 and then the motor 71 is connected to the tip of the rotary shaft 68. Nevertheless, according to the third embodiment, since the rotary shaft 68 is previously secured to the rotor 66, the axes of the two are precisely coaxial. This in turn frees manufacturers from the critical work of correctly aligning axes whenconnecting them to each other which is required in the previous embodiments. 
     Specifically, the motor 71 is previously secured to the tip of the rotary shaft 68 which penetrates through the cylindrical member 62, by inserting the rotor 66 into the cylindrical member 62. Next, while this condition ispresent, the screw 63 of the cylindrical member 62 is engaged with the housing 12. Alternatively, after securing the cylindrical member 62 to thehousing 12 with the screw 63, the motor 71 is secured to the rotary shaft 68 which projects itself from the cylinder member 62. In this case, a specific structure may also be introduced in order to prevent the rotor 66from moving in the axial direction within the cylindrical member 62 so thatthe rotor 66 can be prevented from being pulled out of the cylinder member 62 by the force of the rotary shaft 68 affecting in the axial direction inthe course of connecting the rotary shaft 68 to the motor 71. 
     Next, according to a fourth embodiment of the invention shown in FIG. 14, athrough-hole 82 is provided through the axial line of the rotary shaft 68. Liquid can be loaded into respective liquid chambers through needles (not shown) which are inserted in the through-hole 82. When loading liquid, an aperture may be provided in front of each liquid chamber to atmospherically release air pushed forward by the inflowing liquid, or internal air may be released from the intervals between the needles and the through-hole 82 by disposing the through-hole 82 at a higher position than the needles. 
     After fully loading liquid, the through-hole 82 is closed by inserting rubber stoppers, or the through-hole 82 may be automatically closed by means of the motor 71. 
     FIGS. 15 and 16 respectively designate the vibration damping apparatus according to the fifth embodiment of the invention. In place of the screw member 63, the fifth embodiment provides a cylindrical rubber member 84 for the cylindrical member 62. Internal surface of the rubber member 84 issecured to the external surface of the cylindrical member 62 by means of vulcanizing process. The cylindrical member 62 is thrust into the housing 12 before being fixed. The cylindrical member 62 is thrust into the housing 12 producing an elastic deformation of the rubber member 84 and thereby airtightly sealing the interval between the cylindrical member 62 and the through-hole 78 of the housing 12. Therefore, the fifth embodimentpermits manufacturers to more easily execute the process for assembling therotor 66 with the cylindrical member 62 than those processes done for the preceding embodiments. 
     By virtue of the structural feature mentioned above, the vibration damping apparatus embodied by the invention securely and fully absorbs vibration containing a wide-range of frequencies. These embodiments of the inventionpermit manufactures to precisely position the rotor when inserting it into an cylindrical member provided for part of limited passages to facilitate them to easily assemble the vibration damping apparatus embodied by the invention.