Elastic connection between at least two rigid parts

Elastic connection between at least two rigid parts having provided an elastomeric material therebetween where in the connection at least one sensor is integrated which detects forces or moments acting at the connection. Such connections are advantageously built into apparatuses in particular vehicles and the determined forces and moments are used for controlling and monitoring.

TECHNICAL FIELD 
The invention relates to an elastic connection between at least two rigid 
parts having provided therebetween an elastomeric material. 
BACKGROUND ART 
There are numerous devices, apparatuses,and machines which are either 
elastically supported or parts and units thereof are connected with 
eachother by an elastic connection or linkage. Exemplary, such connections 
have become known under the name "rubber metal springs" or "ruber metal 
elements". With such apparatuses, machines, and devices there is often a 
desire for information about the condition and/or the operating states; 
for this purpose the determination of forces and/or moments acting upon 
the apparatuses, machines, and devices would be of advantage. 
For example, the characteristics of a moving automotive vehicle are 
considerably influenced by the condition of the vehicle, the load and the 
forces acting upon the vehicle during movement. For known vehicles it has 
been tried, in time-consuming and cumbersome investigations during the 
developement period to find a compromise permitting acceptable driving 
characteristics for as many different situations as possible. Furthermore, 
it has become known to manually adjust the spring suspension of the 
vehicle dependent on a large or small load. 
Furthermore, it has become known in connection with the use of telescopic 
air supports to provide a load-dependent electronic height regulation 
which regulates the clearance of the carbody above ground and maintains it 
in the horizontal position. For this purpose, an optical or inductive 
height sensor is secured to a spring support which sensor is connected to 
an electronic regulating circuitry which may be set onto one of several 
different positions. However, the known arrangement has only the purpose 
that the car body is adjusted to one of several selected clearances in a 
static state, i.e. when the vehicle is in rest. 
However, during movement of the vehicle quite different situations exist 
depending on the velocity, the acceleration, deceleration, street 
condition and strength and direction of the wind. These different 
situations were taken into account insufficiently when designing the 
vehicle. The todays efforts to keep the c.sub.w value as low as possible, 
are an illusion when the car body, optimised for a horizontal position, 
inclines in forward or rearward direction in view of the forces 
(load-acceleration etc.) acting onto the vehicle. 
Also, the steering geometry once selected and implemented, as well as the 
setting of the toe-in and the like have an optimum for a single situation 
only though in view of the centrifugal forces in bends and in view of side 
wind there may exist quite different situations. 
The European Patent Application Publication No. 0162 604 discloses a dump 
truck which for determining the load weight is supported in a lowered 
position on force measuring cells. By evaluating pressure peaks the road 
condition and the tire condition may be determined during truck movement. 
The European Patent Application Publication No. 151 421 relates to a motor 
car having two piezo-electric plates inserted as a vibration sensor into 
the suspension. Dependent on vibrations according to the street condition 
the suspension is set to "hard", "soft" or "medium". 
The German Patent Application Publication No. 35 02 337 relates to a 
vehicle spring suspension; the fluid spring chambers supply and drain 
valves are controlled, dependent on a change in direction, by means of the 
angular velocity of the steering wheel and the vehicle speed. 
The German Patent Specification No. 1902944 discloses an automotive vehicle 
preventing swerfing by controlling the break system, the accelerator and 
the wheel alignment (camber, spreading, spring hardness) by comparison 
with boundary values and using swivels, lateral acceleration and speed 
sensors. 
The German Patent Application Publication No. 20 09 489 indicates how with 
a motor car movements or force changes of the chassis or the car body may 
be compensated by means of measuring elements and control devices. 
According to the German Patent Application Publication No. 33 00 640 an 
additional steering is accomplished with an automotive vehicle dependent 
on control parameters as speed and lateral acceleration. 
According to the German Patent Application Publication No. 30 13 114 the 
relative position of the car body of an automotive vehicle is determined 
relative to several vehicle axles by means of axle sensors and pressure 
sensitive pressure signal devices, namely a manometer. 
According to the German Patent Specification No. 26 36 899 overloading of 
an automotive vehicle is indicated by means of loaddependent threshold 
switches. 
According to the U.S. Pat. No. 3,035,853 the suspension of the car body at 
the chassis is stabilized by means of force measuring cells connected to 
the hydraulic cylinders of the suspension. 
According to the German Patent Application Publication No. 32 36 080 a 
torque strain gauge is used for determining the torque acting at the 
steering shaft and for controlling the servo-sterring system. 
The U.K. Patent Application Publication No. 20 79 701 shows an automotive 
vehicle having a slant compensation using a pendulum. 
The German Patent Application Publication No. 30 16 338 dissloses a 
piezo-electric measuring cell mounted in a tire of an automotive vehicle 
using wireless transmission of the measuring values to a control device 
and for indicating the tire condition 
As far as sensors are provided in known automotive vehicles they are 
discrete elements which are separately mounted at appropriate positions of 
the vehicle by means of fixing devices for suitably securing them. Such 
designs are space and cost consuming. 
Though the determination and use of measuring values for determining the 
condition and the operating state have been explained by referring to an 
automotive vehicle, a similar situation exists with many other 
apparatuses, machines and devices as stationary combustion machines, 
electric machines, tooling machines, construction machines, cranes and 
thelike. 
DISCLOSURE OF THE INVENTION 
It is an essential object of the invention to provide an elastic connection 
between at least two rigid parts which connection permits a simple 
detection of forces and/or moments existing in the connection. 
Furthermore, the connection shall be designed such that force or moment 
measurements may be performed by means of a compact and inexpensive means. 
Furthermore, the invention relates to apparatuses, machines, and devices 
comprising means for simply measuring forces and/ or moments at at least 
some elastic connections between rigid parts. 
The elastic connection between two rigid parts having elastomeric material 
provided therebetween is, according to the invention, characterized in 
that in the connection at least one sensor is integrated for detecting 
forces and/or moments existing in the connection. 
Further features and advantages of the connection according to the 
invention as well as the application thereof with apparatuses, machines 
and devices are characterized in the subclaims.

MODES FOR CARRYING OUT THE INVENTION 
FIG. 1 shows a plan view of a chassis of a motor car illustrating exemplary 
possibilities for providing force measuring cells. In particular there are 
shown: 
force measuring cells 31 at the spring legs (viz. also FIGS. 2 and 3); 
force measuring cells 32 between leaf springs or air springs and the car 
body (viz. FIG. 4); 
force measuring cells 33 provided at the steering, guiding and torsion bar 
heads; 
force measuring cells 34 at the toe-in bar heads; 
force measuring cells 35 at the motor, transmission and differential 
bearings; and 
force measuring cells 36 at the chassis and gearing saddles at the front or 
rear of the car. 
If required, further locations at which forces or moments may exist, may be 
provided with corresponding force measuring cells, in particular at a 
trailer coupling. 
By means of the force measuring elements provided at the vehicle in 
particular the forces, driving and braking moments acting upon the wheels, 
the vehicle load, the forces and moments acting upon the steering system, 
as well as forces and moments acting upon the car body, the chassis and 
the transmission saddles may be measured directly. 
Using these measured values the following parameters may be determined 
indirectly by means of data processors and by using stored and, if 
desired, changeable values. 
Thus, on the basis of detected wheel forces, possibly in consideration of 
other parameters and stored values, the condition of the tires, in 
particular the concentric running, the balance and pressure may be 
determined. Furthermore, the directly measured values permit conclusions 
as to the road quality. The same is true for the conditions of the chassis 
and the shock absorbers. Furthermore important, is detecting of the 
slippage on the road, the torques of the wheels, exemplary in connection 
with antiblocking-systems. 
For optimising the driving characteristics the wind resistance, the 
buoyancy forces acting from the front, from the rear and laterally onto 
the car body and lateral forces caused by the side wind may be determined 
and evaluated. 
Force measuring cells 35 used in connection with the support of the motor 
may be used for determining the torque acting at the motor. 
The values and parameters directly measured and derived therefrom 
respectively, are then used for a corresponding adjusting and/or 
regulating of various units of the car as well as for a further processing 
for information purposes. 
For example, the suspension, attenuation and clearance above ground of the 
car may be automatically regulated for an optimisation of the driving 
characteristics. Furthermore, the influencing of the break and 
acceleration forces and the distribution of the driving energy onto the 
wheels is important, in particular, for all-wheel-drives and the 
antiblocking system, respectively. A steering regulation, exemplary in the 
form of an automatic change of the steering geometry, in particular the 
toe-in the steering and the steering point may automatically compensate 
side wind influences. Furthermore, regulating the tire pressure or at 
least an indication of the required tire-pressure may be considered. Also, 
influencing of the torque converter of an automatic shift gearing may be 
possible. 
On the basis of the torque acting on the motor and, in addition, by using 
the rotational speed the actual effective power of the motor may be 
determined and used for optimising the operation of the motor (optimum 
torque), possibly, in connection with the torque converter of the 
automatic transmission gearing. 
FIG. 2 shows an embodiment of the provision of a force measuring cell 31 
(viz. also FIG. 1) in cooperation with a spring leg of a motor car for 
determining the wheel load. An upper flange 13 of a vibration metal 
bearing 3 of the spring leg 2 is connected to force meaasuring cell 31, 
which preferably is an elastostatic force measuring cell as disclosed in 
the European Patent Application Publication No. 145,001 (viz. also FIG. 
3). 
The wheel bearing 4 is horizontally guided from the chassis 5 via the 
levers 6 and 7, a torsion bar 8 and a steering bar 9. The influence of 
by-pass forces caused by the horizontal guidance, onto the wheel load 
measurement are compensated by a load dependent calibration. 
FIG. 3 illustrates details of the mounting of the force measuring cell 31 
in the spring leg 2. 
The force measuring 31 of the preferred embodiment consists of two potlike 
elements, i.e. an outer pressure cylinder 22 and an inner load piston 24 
nested in the cylinder 22, elastomeric material 23 being provided between 
these elements peripherally and between the bottom of the pressure 
cylinder 22 and the top face of the load piston 24. In pressure cylinder 
22 a pressure transducer or sensor 21 is arranged which exemplary operates 
on a piezo-resistive basis. The pressure transducer 21 is inserted into 
the pressure cylinder 22 from the topside and, with its bottom side, it is 
contact to the elastomeric material. The car body 55 of the motor car has 
a flange 14, which exemplary is connected to a flange 25 formed at the 
pressure cylinder 22 by a corresponding screw connection 26. 
On the other hand the load piston 24 is provided with a flange 16 secured 
to the flange 13 of the vibration metal bearing 3 of the spring leg 2 by 
means of a screw connection 17. At the upper end of a piston rod 10 
extending into the vibration metal bearing 3 there is provided a groove 
ball bearing 27, which ensures a rotational movability between the spring 
leg and the force measuring cell. A projection 57 of the piston rod 10 
supports a spring plate 28 engaging a spiral spring 29. The piston rod 10 
is surrounded by a hollow rubber spring 11. 
The weight of the car body 54 urges against the elastomeric material 23 
provided between the pressure cylinder 28 and the load piston 24, which 
elastomeric material transmit this pressure to the pressure transducer 21 
converting this pressure into an electric signal which is supplied to the 
evaluation unit. The wheel load may be determined with the car in rest 
either after or during the loading. This enables a determination of the 
added load by first determining the net-weight of the car body before 
loading and offering a continuous indication during loading. Such an 
arrangement may preferably be provided with trucks. 
On the other hand, on the basis of the statically determined wheel load the 
suspension, attenuation ect. may be adjusted correspondingly. This allows 
to consider an asymmetric loading of the invididual wheels. 
However, according to a further aspect of the present invention it is also 
possible, to determine the dynamic response of the forces exerted onto the 
wheel by continuous measurement during driving and to use this response 
for optimising the driving characteristics. 
FIG. 4 illustrates the bearing and suspension of a wheel as it may be used 
in connection with a truck or a rail vehicle. In particular FIG. 4 shows 
force measuring elements 32 which may be similarly designed as force 
measuring element according to FIG. 3. 
FIG. 4 shows the car body 55 resting on supporting elements 46 of the axle 
arrangement 48 by means of air springs 44 with interposed force measuring 
cells 32. 
FIG. 5 shows an alternative embodiment for supporting the car body 55 by 
means of a hollow rubber/air spring 44 on a support element 47 engaging 
the wheel axle not shown in FIG. 5. 
FIG. 6 shows an embodiment of the inventive connection further integrated 
as compared with the embodiment of FIG. 3; similar or corresponding parts 
are provided with the same reference numerals as in FIG. 3 and are not 
explained in further detail. It should be noted the omission of the 
flanges 13 and 16, respectively, and of the screw connection 17 and the 
considerable reduction in height of the arrangement. 
With this embodiment the vibration metal bearing 3 is directly inserted in 
an inwardly tapered recess 63 of a pressure piston 64 which in turn is 
provided in a pressure cylinder 61 similar to the pressure cylinder 22. 
Thus, there is a complete integration of the force/moment measuring device 
resulting in low manufacturing efforts. Furthermore, the force/moment 
measuring device does not need any essential additional space. 
FIG. 7 shows an embodiment of the connection according to the invention as 
it may be used for a force measuring cell 35 for supporting the motor or 
the shift gearing, respectively. This embodiment is particularly simple 
since the connection is just a bearing support on a basis 65 of the 
chassis without any lateral securing. The more important is in this 
connection the complete integration of the force measuring cell in the 
elastic connection. 
As with the embodiment of FIG. 6 the vibration bearing 3 is again provided 
in the interior of a tapered recess 63 of the pressure piston 64 which is 
arranged in the interior of the pressure cylinder 61. The latter may 
exemplary be secured to the motor 37 (FIG. 1) by means of screws. Again, 
in this connection there is no increase in height of the arrangement by 
interposing the force/torque measuring device. Housing the vibration metal 
bearing 3 in the interior of the pressure piston 64 results in a 
particularly simple mounting. FIG. 8 shows a further embodiment of the 
invention using an integrated force measuring cell 33 (viz. also FIGS. 1 
and 2). Again, the complete integration of the force/moment measuring 
device in the connection joint should be noted. The torsion bar 8 (viz. 
also FIG. 2) is surrounded by elastomeric material 66 which in outward 
direction is bounded by the inner surface of a pressure cylinder 67 formed 
in the region of the torsion bar 8 and having a half-cylindrical shape. 
The half-cylindrical part 86 merges into a cylindrical section 69 whose 
longitudinal axis is orthogonal to the longitudinal axis of the torsion 
bar 8. A piston 70, fitted with its rear side to the rounding of the 
elastomeric material 66 is guided in the cylindrical section 69 and acts 
via the elastomeric material 23 onto the pressure transducer or sensor 21. 
The force vertically acting onto the torsion bar 8 is transmitted through 
the elastomeric material 66 to the piston 70 and from the latter through 
further elastomeric material to the sensor 21. 
With the embodiments described above in particular an integrated force 
measuring cell according to European Patent Application Publication No. 
145 001 has been used. Such a force measuring cell is particularly 
characterized in that between a cylindrical element and a piston guided 
therein there is formed a very narrow gap exemplary in the range of point 
1 to 2 millimeters which gap is relatively high and completely filled with 
elastomeric material. Between the face surface of the piston and the 
bottom of the cylindrical element there is formed a space which is filled 
with elastomeric material. A pressure or force sensor is either embedded 
in the elastomeric material or is accessible from the exterior and, 
respectively, insertable in a wall of the cylindrical element such that in 
particular the force receiving surface of the pressure or force sensor is 
in engagement with the elastomeric material. 
FIGS. 9 to 14 schematically show embodiments illustrating a further 
simplification and integration of the force measuring cell in the elastic 
connectin of two rigid parts. 
In particular, with those embodiments the piston 70 (FIG. 8) is completely 
omitted which results in designs where a cylindrical element 72 is 
surrounded by a concentric space filled with elastomeric material 73 which 
space exemplary is formed in a flangeable element 71. This results in a 
bearing joint as it may exemplary be used for a torsion bar of a wheel 
suspension of a motor car. Alternatively, the element 72 may form a 
bearing in which an axle may rotate. 
The embodiments according to the FIGS. 9 to 11 differ only by the different 
number and arrangement of pressure sensors. With the embodiments according 
to FIGS. 9 and 10 the pressure sensors are inserted into the cylindrical 
inner wall, the embodiment of FIG. 9 using one pressure sensor 74 only 
whilst the embodiment according to FIG. 10 using several, exemplary four 
pressure sensors indicating the load int he foru directions by means of 
corresponding electric signals. 
With the embodiment of FIG. 11 the pressure sensors 74, specifically three 
pressure sensors 74, are embedded in the elastomeric material 73; thus, 
there is no need of mechanical tooling of the parts 71 and 72, 
respectively. 
FIGS. 12 to 14 show embodiments similar to those of the FIGS. 9 to 11, 
however, using an outer rigid part formed as a tube 75 concentrically to 
the inner rigid part 72. The arrangement of the force measuring cells 
correspond to that of the embodiments of FIGS. 9 to 11. 
FIGS. 15 and 16 show embodiments using a conical or inclined, respectively, 
vibration metal spring by means of which a machine element 79 may be 
elastically supported in three dimensions which as known prevents the 
transmission of vibrations to frame 78. One or several force measuring 
cell(s) 77 may be embedded in the elastomeric material 76 or may be 
inserted at one of the contact surfaces of the machine element 79 or the 
frame 78, respectively, in the elastomeric material 76. 
FIG. 17 shows the simplest embodiment of an elastic connection using an 
integrated force measuring device where an upper rigid part 81 is 
elastically supported via a block of elastomeric material 82 on a base 
part 83. One or several pressure sensors 84 may be either embedded in the 
elastomeric block 82 or, however, are inserted in the contact surfaces of 
the parts 81 or 83, respectively to the elastomeric block 82. 
It should be noted, that with the various embodiments the elastomeric 
material preferably is tightly connected, in particularly vulcanized with 
the contact surfaces of the rigid parts, engaging the material. This 
ensures a uniform transmission of the forces and moments acting onto the 
rigid parts. Even in mass production this results in connections which 
have a similar characteristic which may be predicted with high 
probability. Thus, the force or moment measurement may be performed 
without any cumbersome adjustment and with sufficient accuracy. 
As explained before, with the integrated pressure sensors not only forces 
may be measured which exist in or at, respectively, the connection. 
Torques exerted onto the connection may be determined by a corresponding 
multiplication of the measured force components by the associated lever 
arms. However, by a corresponding arrangement and alignment of the 
pressure sensors torques may be directly determined, too. An example for 
such a connection is shown in FIG. 14 where the pressure sensors 74 are 
arranged exemplary at an angle of 45 degree in respect of the radial 
direction. With a fixedly mounted outer rigid cylinder element 75 the 
pressure sensors 74 measure a torque a moment exerted onto the inner 
element about the central longitudinal axis. Also, a radial arrangement of 
the pressure sensors is possible. 
FIG. 18 illustrates an embodiment of the connection according to the 
invention where in addition to force measurement the torque may be 
directly determined. A first rigid, fixedly mounted element 84 is provided 
with two spaced flanges 92 between which extends a rod 87 having a 
non-circular exemplary squared crosssection, the rod 87 being secured at 
its opposite faces exemplary by means of screws 88. A second rigid part 86 
exemplary in the form of a lever is provided at its one end with a 
throughhole 93 surrounding the rod 87. The through-hole 93 preferably is 
also of a non-circular exemplary squared cross section the edges of the 
rod 87 being offset in respect of the edges of the through-hole 93 
exemplary by 90 degree. The through-hole 93 is somewhat larger as the 
cross-section of the rod 87 the interspace between the surfaces of the rod 
87 and the sides of the through-hole 93 being filled with cushions 94 made 
of elastomeric material and enclosing a pressure sensor 95. With the 
embodiment the pressure sensors 95 are aligned such that their pressure 
receiving surfaces extend in parallel to the surfaces of the rod 87. When 
a torque is exerted onto the lever 86 about the longitudinal axis of the 
rod 87 this torque may be determined directly by the sensors 95. 
FIG. 19 shows a connection between a rigid fixedly arranged part 85 and a 
further rigid part 86. Again a rod 87 having preferably a squared cross 
section is used. 
The cushions 94 correspond to those of FIG. 18. 
It should be appreciated, that all connections have directly integrated 
force measuring devices which results in a particular advantageous 
arrangements in respect of cost and space. 
With a motor car according to FIG. 1 being provided with such elastic 
connections containing force/moment measuring devices the electrical 
signals supplied by the pressure sensors may be applied to a processor 100 
representing the central processing unit of the control system illustrated 
in FIG. 20. A person skilled in the field of data processing is in the 
position to set up a corresponding program for the processor which 
generates on the basis of detected values, stored reference values and 
corresponding mathematical relations of the values to each other various 
control signals. In particular, a control signal may be issued from the 
processor 100 to a steering control circuit 101 by which signal the 
steering angle or the degree of servo-steering, respectively, the toe-in 
or the like may be influenced. A further control signal may be applied to 
a motor operating control circuit by which signal a control of fuel 
supply, the ignition time and the like may be accomplished. Also the 
processor 100 may apply further control signals to a suspension control 
circuit 103 by means of which the clearance of the car body above ground, 
as well as the degree of spring action of the individual wheel suspensions 
may be controlled dependent on the momentary load caused by the loading, 
the driving and the side wind as well as the cornering characteristics. A 
further control signal may be supplied to a break control circuit 104 
controlling an antiblocking system. A further control signal may be 
applied to an emergency control unit 106 which initiates appropriate 
measures in case of emergency as inflating a protective air bag. Control 
signals supplied to an indicator control circuit 105 cause the initiation 
of corresponding indicator controls giving optical and accustical 
indications to the user of the vehicle. 
For other apparatuses, machines and devices a corresponding control system 
may be designed by a person skilled in the art according to the individual 
requirements. 
As regards the specific design and operation of the force/moment measuring 
devices integrated in the connections according to the embodiments it is 
referred to the European Patent Application Publication No. 145 001 the 
disclosure of which is completely declared to the contents of the present 
patent application. In particular, the material for the elastomeric 
material disclosed there may be used and the dimensional values indicated 
there are a basis for dimensioning the connections according to the 
invention. Also, the various types of sensors disclosed in this printed 
publication are adapted inter alia in connection with the present 
invention. 
In connection with FIG. 8 it should be noted that those connections may 
represent force measuring cells 36 according to FIG. 1, too. The generally 
symetrical arrangement (left and right) of two connections permits the 
calculation of the torque between the two connections on the basis of the 
known distance thereof and using the forces detected by the pressure 
sensors.