Liquid-sealing type variation isolating apparatus

Abstract

The liquid-sealing type vibration isolating apparatus of the present invention includes a coupler attached to a vibrating body, a holder, an insulator for absorbing and isolating vibration from the vibrating body at a position between the coupler and the holder, and a vibration isolating mechanism directly following the insulator and including liquid chambers sealing an incompressible fluid. This vibration isolating mechanism has a main chamber sealing a liquid, having a part of wall thereof formed by the insulator, an auxiliary chamber communicating with the main chamber via an orifice, and an equilibrium chamber provided in a portion of the main chamber via a diaphragm and having a varying volume in the chamber. The vibration isolating apparatus further includes switching means for introducing a negative pressure and the atmospheric pressure continuously or in synchronization with vibration of the vibrating body, and control means for controlling this switching operation.

What is claimed is:  
     
         1 . A liquid-sealing type vibration isolating apparatus comprising a coupler attached to a vibrating body, a holder attached to a vehicle body side, an insulator which is provided between said coupler and said holder and absorbs and isolates vibration from said vibrating body, and a vibration isolating mechanism which directly follows said insulator and is formed with a liquid chamber sealing a liquid which is an incompressible fluid; said vibration isolating mechanism including a main chamber having a wall thereof formed by a part of the insulator and sealing the liquid, an auxiliary chamber connected to said main chamber so that said liquid flows through an orifice, an equilibrium chamber which is provided at a part of said main chamber via a diaphragm and is formed so that the volume thereof in the chamber changes, and an air chamber which surrounds said auxiliary chamber via another diaphragm and constantly receives air; said apparatus further comprising switching means for performing a switching operation so as to alternately introduce any one of a negative pressure and the atmospheric pressure into said equilibrium chamber constantly or in synchronization with engine vibration, and control means for controlling the switching operation of said switching means.  
     
     
         2 . The liquid-sealing type vibration isolating apparatus according to  claim 1 , wherein said vibration isolating mechanism includes a main chamber which comprises a liquid chamber arranged in series with said insulator and having a wall thereof formed by a part of said insulator, an auxiliary chamber connected to said main chamber so as to allow said liquid to flow via an orifice to the main chamber and separated by a partition plate forming of a rigid body from said main chamber, an equilibrium chamber formed via a diaphragm between said main chamber and said partition plate and arranged so as to introduce any one of the atmospheric pressure and a negative pressure, and an air chamber provided under said auxiliary chamber via another diaphragm and constantly fed with air.  
     
     
         3 . The vibration isolating apparatus according to  claim 1 , further comprising 
 a length L 1  of a duct line from said atmospheric pressure inlet to said equilibrium chamber is set at a value determined by the following formula:   0.85 cT/4≦L 1 ≦1.15 cT/4   where c is the sound velocity (340 m/sec) and T is a period of time (in seconds) during which the open air is introduced into said equilibrium chamber by said switching means.    
     
     
         4 . The vibration isolating apparatus according to  claim 1 , further comprising 
 an expansion chamber having a larger diameter than that of said duct line is provided between said atmospheric pressure inlet and said switching means, and a length L 2  between said expansion chamber and said equilibrium chamber is set at a value determined by the following formula:     0.85  cT/4≦L 2 ≦1.15 cT/4   where c is the sound velocity (340 m/sec) and T is a period of time (in seconds) during which the open air is introduced into said equilibrium chamber by said switching means.    
     
     
         5 . The vibration isolating apparatus according to  claim 3 , wherein said required frequency is required for synchronizing with an idling vibration of said engine.  
     
     
         6 . The vibration isolating apparatus according to  claim 4 , wherein said required frequency is required for synchronizing with an idling vibration of said engine.  
     
     
         7 . The liquid-sealing type vibration isolating apparatus according to  claim 2 , wherein said auxiliary chamber is connected to said main chamber via a first orifice, separated by a first partition plate forming of a rigid body and having a part of the wall thereof formed by a first diaphragm, a third liquid chamber is provided to be connected to said main chamber via a second orifice and formed between said main chamber and said first partition plate so as to receive the liquid in said main chamber; and said equilibrium chamber is partitioned and formed by a second diaphragm relative to said third liquid chamber and receiving any one of the atmospheric pressure and a negative pressure; said liquid-sealing type vibration isolating apparatus further comprising a second partition plate serving as a stopper, provided in said main chamber above said second diaphragm forming said equilibrium chamber; the second orifice provided in a portion of said second partition plate.  
     
     
         8 . The liquid-sealing type vibration isolating apparatus according to  claim 7 , further comprising a second equilibrium chamber partitioned and formed by a third diaphragm to said second partition plate and for continuously introducing any one of a negative pressure and the atmospheric pressure therein in compliance with a switching operation of the switching means in response to the traveling state of the vehicle.  
     
     
         9 . The vibration isolating apparatus according to  claim 1 , wherein said housing space is a side branch having a closed end.  
     
     
         10 . The vibration isolating apparatus according to  claim 7 , wherein said housing space is a side branch having a closed end.  
     
     
         11 . The vibration isolating apparatus according to  claim 1 , wherein 
 a resistance for slowing down the introduction of the negative pressure or the atmospheric pressure into said equilibrium chamber is provided in the middle of a communicating path communicating between said switching means and said equilibrium chamber.    
     
     
         12 . The vibration isolating apparatus according to  claim 7 , wherein 
 a resistance for slowing down the introduction of the negative pressure or the atmospheric pressure into said equilibrium chamber is provided in the middle of a communicating path communicating between said switching means and said equilibrium chamber.    
     
     
         13 . The liquid-sealing type vibration isolating apparatus according to  claim 7 , wherein said equilibrium chamber is partitioned and formed by a second diaphragm having a higher deformation rigidity than said first diaphragm relative to said third liquid chamber.  
     
     
         14 . The liquid-sealing type vibration isolating apparatus according to  claim 13 , wherein said second diaphragm has a shape having a stopper-like projection constantly in contact with the partition plate forming the lower surface of said equilibrium chamber and a plate partitioning between said main chamber and said third liquid chamber, on each of the upper and the lower sides near the center portion thereof.  
     
     
         15 . The liquid-sealing type vibration isolating apparatus according to  claim 13 , wherein the configuration around said second diaphragm comprises a rubber-film-like diaphragm, and a spring acting so as to constantly push back said rubber-film-like diaphragm toward the third liquid chamber side communicating with said main chamber.  
     
     
         16 . The liquid-sealing type vibration isolating apparatus according to  claim 1 , wherein said coupler is an inner cylinder, said holder is an outer cylinder, said insulator is provided around said inner cylinder between said inner cylinder and said outer cylinder; said vibration isolating mechanism is provided around said insulator, and said air chamber is provided outside said auxiliary chamber.