Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F13/00—Units comprising springs of the non-fluid type as well as vibration-dampers, shock-absorbers, or fluid springs
  • F16F13/04—Units comprising springs of the non-fluid type as well as vibration-dampers, shock-absorbers, or fluid springs comprising both a plastics spring and a damper, e.g. a friction damper
  • F16F13/06—Units comprising springs of the non-fluid type as well as vibration-dampers, shock-absorbers, or fluid springs comprising both a plastics spring and a damper, e.g. a friction damper the damper being a fluid damper, e.g. the plastics spring not forming a part of the wall of the fluid chamber of the damper
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
  • F16F15/023—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using fluid means
  • F16F15/027—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using fluid means comprising control arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F7/00—Vibration-dampers; Shock-absorbers
  • F16F7/10—Vibration-dampers; Shock-absorbers using inertia effect

Definitions

• This invention relates to an inertially-coupled active engine mount.
• the object of the invention is to effect vibration isolation between a source of vibration and the base to which it is mounted.
• the source of vibration will be a vehicle engine and the base will be the frame or body of the vehicle.
• Design of traditional vibration isolation mounts which is well-known, involves making a compromise between control of the engine's position and the isolation of vibration.
• the vibration across an automotive engine mount below a certain frequency (about 15 Hz) can generally be attributed to movement of the car body while vibration above this frequency is generally due to imbalance, reaction forces from the piston motion, or torque pulsation forces generated by the engine.
• Several authors have proposed that control forces be applied to various parts of a traditional mount to minimize the effect of this compromise.
• a fairly stiff mount which effectively controls engine position, can be made to effectively isolate high frequency vibrations emanating from the engine in the same way an extremely soft mount would normally do.
• the proposed invention circumvents limitations of each of the prior art implementations in achieving this objective.
• actuators which cause pressure fluctuations in one of the fluid-filled chambers. These pulsations are chosen such that dynamic forces across the mount are minimized. Sometimes only the fluid- related forces are reduced and sometimes the net force across the mount is caused to be zero. In either case, a reduction in the dynamic force transmitted across the mount is obtained. Since the actuator is coupled across the mount through the resonant fluid cavity, this arrangement will be referred to as a resonant coupling arrangement.
• Garnjost U.S. Patent No. 5,067,684 proposes a mount unlike the hydraulic engine mounts in which an actuator and damper are interposed across the simple rubber engine mount. The"active" force across the mount is applied through the damper. Garnjost notes that the damper, when properly sized, causes the actuator displacements to be reduced at low frequencies. Since the actuator is coupled across the mount through a damper, this arrangement will be referred to as a viscous coupling arrangement. Accordingly, it is an object of this invention to provide vibration isolation between a source of vibration and the base to which it is mounted.
• Another object of the invention is to reduce the complexity of the vibration control actuator by reducing the displacements to which it is exposed.
• Figure 1 shows, schematically, a mount configuration used by inventors Idtechnik, Andra and Hoying et al.
• Figure 2 shows the configuration described by inventor Garnjost.
• Figure 3 shows the preferred embodiment of the present invention.
• Figure 4 shows a cutaway view of a component of the present invention, a piston and cylinder as an inertial coupling.
• Figure 5 is a diagram showing a plot of the ratio of engine displacement to actuator displacement versus frequency.
• Figure 6 shows a cutaway view of an embodiment in which the shear coupling is a rod.
• Figure 7 shows a cutaway view of an alternative version of the embodiment of Figure 6.
• Figure 8 shows a cutaway view of the present invention in use on a conventional hydro-mount.
• Figure 1 shows the shortcomings of the approach suggested by Idtechnik, Andra and Hoying et al. It shows the arrangement schematically, replacing physical elements with their dynamic equivalents.
• Spring 1 and damper 2 are the elastomeric stiffness and damping of the mount.
• Spring 3 represents the "bulge" stiffness of the mount. This element represents the pressure forces exerted by the fluid in the mount as a result of displacements of fluid or the various fluid-displacing mount components.
• Actuator 4 is restrained to displace only a small amount by stops 5.
• the placement of the support 20 under beam 6 represents the area ratio between the fluid passage and the main chamber and mass 7 represents the mass of the fluid in the passage.
• Spring 8 and damper 9 represent the stiffness restraining the fluid in the passage and the viscous resistance to flow through the passage, respectively.
• Plate 10 represents the vehicle body while mass 11 represents the portion of the engine mass supported by that particular mount. It can be seen that when the mass 11 resonates, the force through spring 3, which acts to restrain the engine, is high. This occurs when the engine has been caused to move at large displacements relative to the frame by forces input from the road. This high force through spring 3 only occurs when the actuator has been "shorted" by the stops 5. Therefore, the actuator 4 is unable to apply control forces across the mount under conditions of high engine displacement.
• the design of Garnjost is shown schematically in Figure 2 showing engine mass
• Figure 3 shows, schematically, how the invention is arranged. Many of the elements of Figure 1 are present and the actuator is moved into a position in parallel with the mount stiffness and damping and is placed in series with an inertial coupling 12 and a shear coupling 13.
• the inertial coupling is a device which transmits a force which is proportional to the acceleration of the device's two terminals.
• the shear coupling transmits force primarily along its axis while having very low stiffness in the plane normal to its axis.
• the coupling 12 is a hydraulic cylinder 31 with a piston 32 having openings 33 which allow fluid to pass between its chambers.
• the openings are large enough that the fluid viscosity does not impede the flow significantly, but are small enough, compared to the piston area, that the acceleration of fluid through the openings causes a force to be transmitted across the coupling.
• the shear coupling can consist of a device as disclosed in Chaplin's U.S. Patent 4,600,863, or a stack of many pieces of rubber which have a high area to thickness ratio separated by stiff material, or a hydraulic device constructed of rubber and a fluid as used in common engine hydraulic mounts. It could also be as simple as a flexible rod.
• This "active assembly” could either be internal or external to the rubber structure.
• the shear coupling 40 is simply a long, thin rod which transmits very little force in directions perpendicular to its axis.
• the mount stiffness 41 is provided by molded rubber, which supports the engine's weight and reacts against its torques.
• the engine is attached at engine attachment means 42 and the bottom of the mount rests on the vehicle body 10.
• the actuator 4 drives across the mount through the inertial coupling 12, the lower end of which is attached to the bottom of the mount and the car body 10.
• the shear coupling action is provided by the fact that the clearance between the plunger 51 and rigid sides 52 of the mount is large enough for fluid 53 to flow unimpeded by viscous resistance, but small enough to induce high accelerations in the fluid.
• This enables rotation and off-axis motion of the piston while allowing unrestricted axial motion and "inertial" resistance to that motion.
• Figure 8 shows how a conventional hydro-mount might be modified to include the current invention without sacrificing the beneficial behavior of the hydro-mount at low frequencies.
• the hydro-mount might be modifed to include the current invention without sacrificing the beneficial behaviour of the hydro-mount at low frequencies.
• the hydro-mount contains two fluid cavities 62 and 63 which are connected by an orifice 66.
• the lower cavity 63 is bounded by a rubber diaphragm 65 on one side.
• tube 61 is a device like that disclosed in the referenced Chaplin patent above except with low axial stiffness and high circumferential stiffness, and hence resistance to radial expansion. This "tube” would exert forces across the hydro-mount 60 as a result of motion of the actuator 4 and inertial coupling 12 without otherwise influencing the pressure within the mount's operating fluid cavities 62, 63 and 64.
• the pressure between cavities 62 and 64 could be equalized with small holes allowing communication between the cavities.
• the tube 61 could be constructed of a rubber tube reinforced with steel rings, a wire mesh, or other means such that it would contain fluid pressure without expanding radially, but would easily expand axially.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Aviation & Aerospace Engineering (AREA)
• Combined Devices Of Dampers And Springs (AREA)
• Arrangement Or Mounting Of Propulsion Units For Vehicles (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1994
  • 1994-05-11 EP EP94917347A patent/EP0704037A4/fr not_active Withdrawn
  • 1994-05-11 WO PCT/US1994/005215 patent/WO1994027083A1/fr not_active Application Discontinuation
  • 1994-05-11 JP JP6525665A patent/JPH08508815A/ja active Pending

Patent Citations (1)

Non-Patent Citations (1)

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