BACKGROUND OF THE INVENTION

An actuator device is described which reduces the vibrational forces imparted by

an internal combustion engine to the interior of a vehicle. Specifically, an electromagnetic

actuator is described which may be implemented in an engine mount for generating a force for canceling vibrational forces induced by the internal combustion engine on the

vehicle frame.

One of the desirable marketing features for a passenger automobile is reduced

passenger compartment noise and vibrations. The principle source for passenger compartment noise and vibrations is the internal combustion engine supported to the frame

of the automobile. The internal combustion engine produces vibrational forces, typically

within the bandwidth of 8 to 50 Hz which are torsional in nature. Conventional engine mounts which support the engine to the automobile frame are designed to help reduce the amount of vibrations induced in the automobile frame. The mount typically includes an

upper casing connected to the engine and a lower casing connected to the frame, and the

casings are in turn fastened together. The upper casing contains a metal bushing

supporting an engine mounting bolt connected to the engine. The metal bushing is in turn

supported by a rubber disk to the upper casing. The rubber disk provides some damping of the engine vibrations, and is capable of compressing a few millimeters under the static

load of the engine. The lower casing is attached to the vehicle frame via a frame bolt.

Typically three or four of such mounts are used to support the engine to the automobile frame.

Various attempts have been made to improve upon the isolation of the automobile

passenger compartment and frame from the internal combustion engine. A number of

patents have issued relating to the use of electromagnetic vibration devices for canceling

the vibratory forces generated by the internal combustion engine. Such attempts are

described in U.S. Patents 4,699,348, 4,869,474, 4,083,433 and 4,664,219. These

devices are utilized in a closed loop which includes a vibration sensor, and an actuator

connected to the engine mount. The sensed vibrations are used to create a damping force

in opposition to the engine vibration.

Some of the foregoing devices require significant changes from conventional engine

mounting to implement the vibration reducing transducers. Hence, there is a need for a

force transducer having a mechanical configuration which is capable of replacing a conventional engine mount without any significant redesign or reconfiguration of the

attachment between frame and engine.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a engine mount actuator for reducing

vibration imparted from a internal combustion engine to an automobile frame.

It is a more specific object of this invention to provide an actuator which is

compatible with present day engine mounting arrangements.

These and other objects of the invention are provided by an electromagnetic

actuator incorporated within an existing engine mounting structure which generates a

counter vibratory force to engine produced vibrations. The electromagnetic actuator is

supported by a mounting flange located between the upper and lower casings of a conventional mounting structure. The electromagnetic actuator and mounting flange may

be displaced in a lateral direction in order to compensate for side loads imparted by the

engine to the electromagnetic actuator. The actuator of the preferred embodiment has a stator with first and second concentric toroidal windings which define a circumferential space there between. A magnet assembly is disposed within the circumferential space,

and is coupled to an engine mounting bolt in the upper casing. An electromagnetic

current through the stator windings displaces the magnet assembly and the coupled engine

mounting bolt along the axis of the engine bolt in a direction to counteract vibrational

forces induced by the engine on the mounting bolt. In a preferred embodiment of the

invention, the magnet assembly is coupled via a bearing and spherical bushing assembly to the engine mounting bolt. An alignment shaft coaxial to the engine mounting bolt

extends through a bore in the stator and supports the magnet assembly for sliding movement within the circumferential space between stator windings.

DESCRIPTION OF THE FIGURES

Figure 1 is a section view of an actuator in accordance with a preferred

embodiment of the invention.

Figure 2 illustrates the permanent magnet assembly used in the actuator of Figure 1.

Figure 3 illustrates the configuration of the stator used within the actuator of Figure 1.

Figure 4 is a top partial view of the floating flange 20.

Figure 5 is a section view of the floating flange 20 in the vicinities of bushing 17.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to Figure 1 , there is shown an electromagnetic actuator 5 in

accordance with a preferred embodiment of the invention. The electromagnetic actuator

5 is supported within a conventional engine mounting structure, and generates a counter

vibratory force between engine mounting bolt 24 and frame mounting bolt 27. The

conventional mounting structure includes a lower casing 11 , facing an upper casing 9 and

connected thereto by a plurality of mounting bolts 30. The upper casing 9 includes an

elastomeric isolator disk 10, supported against the inner wall of upper casing 9. A engine

support bushing 23 within the upper casing 9 is connected to the mounting bolt 24 by a

fastener 22. The elastomeric isolator disk 10 compresses in response to the weight of the

engine supported by mounting bolt 24. and serves to dampen engine vibrations transmitted by mounting bolt 24.

The lower casing 11 is connected to the engine frame via a frame mounting bolt

27 and an associated washer 31. The electromagnetic actuator 5 in accordance with the preferred embodiment includes a stator assembly 7 supported on a flange 20, captivated between the upper and lower casings 9 and 11 , and a moving magnet assembly 8 which moves into and out of

a circumferential space 34 provided by stator assembly 7. The magnet assembly 8 is in

turn coupled by a bearing assembly 25 to the engine mounting bolt 24. The stator 7 includes as shown in Figure 2 inner and outer windings 33 and 38.

The inner winding 33 is in two upper and lower segments and each segment is wound

concentric to the force axis 39 for the device on coil form 37. The outer winding 38 is also formed in an upper and lower segment and supported by a non-ferrous coil form 43.

Each of the segmented windings carry a current in opposite directions from each other

producing an additive force with oppositely disposed groups of magnets 15 and 18 of the

magnet assembly 8.

The magnetic circuit of the stator 7 includes an exterior ferrous cylinder 40 and

an internal ferrous coil form 37. The coil forms 37, 43 and outer case 40 for the stator

7 are connected together along the bottom thereof with a nonferrous face plate 41 by

fasteners 49. Thus, the magnetic flux is confined between coil form 37 and ferrous tube

or cylinder 40 to produce the maximum magnetic flux orthogonal to the inner and outer

coils 33 and 38. The outer case 40 is in turn held by fasteners 32 to the floating flange

20. Floating flange 20 includes oversized openings 51 and 52, which receive the bushing

17. The bushing member 17 is selected to be approximately 20 mils higher than the thickness of the flange 20. In this way, any side loads imparted by the engine mounting

bolt 24 with respect to the frame mounting bolt 27, will induce a small degree of lateral

movement of the flange 20 and the entire stator 7 in a direction to reduce side loading. A linear slide bearing 31 is included in a central bore 35, of the stator 7 coaxial to the force axis 39. The slide bearing 31 is adapted to receive an alignment shaft 36 on the

magnet assembly 8 of Figure 3.

The magnet assembly 8 is coupled by a bearing assembly 25 including a bearing cap 28 and spherical bearing 21 to the engine mounting bolt 24. The assembly includes

a receptacle 29 integral with the magnet assembly support plate 19 of the magnet

assembly 8. A pan screw 26 holds the spherical bearing 21 to the engine mounting bolt

24, and the bearing cap 28 connects the spherical bearing 21 to the magnet assembly 8.

The spherical bearing assembly will permit rotation in three degrees if the engine rocks or twists.

Referring now to Figure 3, the magnet assembly is shown which includes first and

second permanent magnet arrays 15 and 17, which are disposed about a circumference

to coincide with the position of the circumferential space 34 defined by the stator

assembly 7 of Figure 2. The magnet assembly is divided into an upper and lower

circumferential assemblies 15 and 18. The magnets of the assemblies are held in place

with spacers 16 captivated by a magnet holder 13 and a magnet assembly support plate

19. Two toroidally shaped magnets may be used in place of discrete permanent magnets

of each of the assemblies 15 and 18. Threaded screws 14 hold the entire magnet

assembly together.

The alignment shaft 36 is held at one end by a set screw 48 in the bearing

assembly 25, and is received in the slide bearing 31 coaxially located with the force axis 39, so that the magnet arrays 15 and 18 may be accurately located within the

circumferential space 34 of the stator 7. Once located, the engine mount 5 under load positions the upper and lower magnet arrays 15 and 18 adjacent the upper and lower

segments of inner and outer windings 33 and 38.

In operation, the inactivated actuator does not support the engine, but relies upon

the conventional elastomeric support 10 for support. The actuator is specifically designed

to axially push and pull the engine mounting bolt 24, by means of a force generated along

the force axis 39. Using a control system in accordance with the prior art devices noted previously, the dynamic forces produced by the engine which fluctuate above and below

the nominal static load can be reduced if not eliminated. These forces tend to have a

magnitude in the plus or minus 20 pound range, and within a vibrational frequency

spectrum out to 100 Hz.

The actuator produces a linear force between the upper magnet assembly 8 and the

lower stator 7 section along the force axis 39, which is parallel to the support axis for the engine mount. The force produced is proportional to an input current through the inner

and outer coil windings, which may be advantageously connected in series, and the

magnetic flux density from the permanent magnets which is radial in nature. In the

preferred embodiment, the upper magnet assembly 15 has a north/south polarity which

produces a radially inward magnetic flux field whereas the lower magnetic assembly 18

has north/south polarity which produces a radially outward magnetic flux field. The

windings in the lower sections in both the inner and outer windings 33 and 38, are wound in opposite directions, and the magnetic field vector through the upper inner/outer coil sections is opposite from the magnetic field vector through the lower inner and outer coil

sections. The total force produced by the electromagnetic actuator is as follows:

F _z = I ₀ B _r (N,2π _rι + N ₀ 27rr ₀ ), where, F _z = axial Force [N]

I ₀ = input current [A]

B _r = radial magnetic flux density [T]

N _t = number of inner winding turns within the magnetic field

N ₀ = number of outer winding turns within the magnetic field

r _f = mean inner coil radius [m]

r ₀ = mean outer coil radius [m] The inner and outer coil windings are generally connected in series but can also be

connected in parallel for certain applications.

During operation, any lateral forces which are imparted to the actuator, tend to

bind the linear bearing 31 with the central alignment shaft 36. The effect is minimized

by having the mounting flange 20 supported to shift horizontally in response to a higher

than normal lateral force. Referring to Figures 4 and 5. a high temperature, low friction

material, such as polyimide 53 may be applied to the top and bottom surfaces of the

mounting flange 20 to lower friction and promote sliding movement in response to an

excessive lateral force. The bushings 17, have a height of 20 mils greater than the

thickness of the mounting flange 20, thus avoiding binding of the lower case 11 or the

upper case 9 to flange 20, when a lateral force is exerted between the magnet assembly

8 and stator assembly 7. Flange 20 floats between upper case 9 and lower case 11 but

is held in place by a plurality of mounting bolts 30 around the periphery of the flanges

of the lower and upper cases 11 and 9.

The upper bolting location on the engine can move with respect to the frame

bolting location because of elastomeric isolation disk 10. Spherical bearing assembly 25

will permit rotational movement between the upper and lower mounting locations.

Thus, there is shown an actuator device which may be incorporated in a standard

engine mounting structure, which will produce an adequate compensation force for

dampening engine induced vibrations. Those skilled in the art will recognize yet other

embodiments of the invention as described by the claims which follows.