Unitary sensor assembly for automotive vehicles

Abstract: A unitary sensor assembly for use in an automotive vehicle having a source of electrical power (50), a body and an automotive suspension relatively movable with respect to said body, comprising: first sensor means (36) for determining the operational position of said suspension with respect to said body (15) and including a first sensor component (38) movable with respect to a second sensor component (40) and means (42) for attaching said first sensor component (38) said suspension (14) and said second sensor component (40) to said body (15) such that said first and second sensor components (38,40) will be caused to move with respect to one another when said suspension (14) moves with respect to said body (15); second sensor means (46) for determining the acceleration of said body (15) of said vehicle with respect to the surface upon which said vehicle is travelling; and electrical power transmission means (44) mounted said first sensor means (36) and electrically interconnecting said first and second sensor means (36,46) for transmitting electrical power from said electrical power source (50) to said first and second sensor means (36,46).

Description: The present invention relates generally to a sensor assembly for use with a suspension system of an automotive vehicle. More particularly, the present invention relates to a unitary sensor assembly for determining the operational position of the suspension as well as the acceleration of the vehicle body with respect to the surface upon which the vehicle is travelling. Automotive suspensions employing adjustable suspension units typically utilise a plurality of height or position sensors for detecting the position of one or more portions of the suspension with respect to another part of the suspension itself or another part of the chassis of the vehicle. In the case of vehicles utilising load levelling, air, hydropneumatic, or other semi-active or active suspension systems, it is necessary to know the ride height of the vehicle in order to determine whether ride height correction is required. In the event, for example, that the ride height is less than prescribed limits, as determined by a height sensor, an adjustable suspension unit may be given a command to increase ride height. Conversely, in the event the ride height exceeds the prescribed limits, the adjustable suspension unit may be given the command to lower, or decrease the ride height. Furthermore, the vehicle ride is influenced greatly by the road conditions. Evaluation of vehicle ride includes measuring the acceleration of the vehicle body with respect to the surface upon which the vehicle is travelling to adjust the suspension unit to dampen the harshness of the vehicle ride due to the road conditions. Typically, an acceleration detecting means, such as an accelerometer, is arranged at part of the vehicle body to determine the motion vibrations of the body due to road conditions. In typical active and semi-active suspension systems, separate height sensors and accelerometers are employed at various locations surrounding the vehicle to generate the above-described information so that the suspension unit may be controlled to respond to given road and load conditions. For example, U.S. Patent Nos. 4,834,419; 4,827,416; 4,743,046; 4,712,807; 4,700,971; 4,065,154; 3,603,612; and 3,124,368 disclose various suspension control systems and associated componentry utilising height sensors separate and apart from acceleration sensors surrounding the vehicle. In utilising separate height and acceleration sensors, there is often a time delay in the information sent to the system controller due to the distance between the sensors. This time delay often results in undesirable cross correlation of the sensed information. Furthermore, the amount and cost of the electronics associated with a system employing separate height and acceleration sensors is increased and installation of a plurality of sensors into a limited amount of space is complicated. Therefore, there is a need for a unitary sensor assembly combining a height and acceleration sensor into a single assembly which negates the undesirable cross correlation effects and reduces the complexity of the electronic circuitry involved with separate sensors and which easily installs into tight vehicle areas. U.S. Patent No. 4,804,203, assigned to the assignee of the present invention, discloses a suspension control system for operating an adjustable suspension unit. The system utilises a single sensor for measuring ride height and relative vertical velocity of a suspension with respect to the vehicle chassis. The sensor of the '203 patent is a height sensor which produces a signal corresponding to the position of the road wheel and tire assembly of the vehicle with respect to the vehicle chassis. A processor receives this set of signals and calculates vertical acceleration of the road wheel with respect to the chassis through a complex algorithm. The calculation of vertical velocity in the '203 system is time consuming and may be too lengthy to be of advantage in real time active suspension systems. EP-A-0 398 311 discloses a sensor assembly for use in an automotive vehicle having a body and an automotive suspension relatively movable with respect to said body, the sensor assembly comprising a first sensor means for determining the operational position of the suspension with respect to the body and a vertical acceleration sensor according to the preamble of claim 1. In EP-A-0 398 311 the sensor assembly is not unitary and the electrical power transmission means is not mounted to the first sensor means and does not electrically interconnect the first and second sensor means. It is an objective of the present invention to provide a unitary sensor assembly for use with an automotive suspension system wherein the assembly provides suspension position and acceleration information from the same point of the suspension to eliminate cross correlation of sensed information. It is a further objective of the present invention to provide a unitary sensor assembly for use with an automotive suspension wherein the assembly includes a height and acceleration sensing means electrically connected to a single circuit board. It is an advantage of the present invention to reduce the complexity and cost associated with multiple, separated sensors surrounding the vehicle by providing a unitary sensor assembly utilising a common circuit board for supplying power to the height and acceleration sensing means on the assembly. According to this invention we provide a unitary sensor assembly comprising the features of claim 1. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a front elevational view of an automotive suspension equipped with a telescoping or linear suspension sensor assembly according to the present invention. Figure 2 is a front elevational view of an automotive suspension equipped with a rotary suspension sensor assembly according to the present invention. Figure 3 is a schematic, side elevational view of the linear sensor assembly of Figure 1. Figure 4 is an overall system block diagram in accordance with an embodiment of the present invention. Figure 5 is a schematic diagram of the sensor assembly of the present invention. As shown in Figures 1 and 2, a suspension sensor assembly according to the present invention is intended for use with an automotive suspension including road wheel and tire assembly 10 rotatably attached to a wheel carrier 12. Each of the suspensions shown in Figures 1 and 2 includes a lower control arm 14 having an inboard end pivotally attached to chassis 16 of the vehicle and an outboard end pivotally attached to wheel carrier 12. The suspension shown in Figure 1 also includes an upper control arm 18 pivoted between the upper end of the wheel carrier 12 and the chassis 16, and a suspension spring 22 interposed between a first spring seat associated with lower control arm 14 and a second spring seat associated with the chassis 16. As such, the chassis comprises part of the suspension because it includes attachment points for the various moving parts of the suspension. Finally, the suspension in Figure 1 also includes at least one adjustable suspension unit 20 and linear sensor assembly 24 mounted between wheel carrier 12 and body 15 such that vertical movement of the road wheel 10 will be accompanied by telescoping movement of sensor assembly 24. In addition to the elements previously enumerated, the suspension of Figure 2 includes at least one adjustable McPherson strut 26 having a lower end rigidly attached to wheel carrier 12 and an upper end which extends through ride height adjuster 28. The upper end of strut 26 extending above ride height adjuster 28 is resiliently or pivotally attached to the chassis of the vehicle in conventional fashion. The suspension in Figure 2 is completed by the suspension sensor assembly 24 which includes a rotary position sensor 30 which senses the vertical position of the road wheel with respect to the chassis. As may be seen from Figure 2, this sensing results from the connection of position sensor 30 between the chassis 16 and lower control arm 14 such that the motion of lower control arm 14 which accompanies the vertical movement of the road wheel will be translated into rotary motion of the sensor by crank arm 32 and connecting link 34. Those skilled in the art will appreciate in view of this disclosure that although the present suspension systems have been described in view of well known parallel arm and McPherson strut configurations, a sensor assembly according to the present invention could be utilised with a variety of suspension configurations including modified McPherson strut, Hotchkiss, quadralink, or other types of suspension configurations. It will further be appreciated that an assembly according to the present invention could be utilised with suspension systems featuring not only controllable damping or controllable ride height, but also those systems in which both damping and ride height are controlled. Further, the sensor assembly disclosed herein would likely be useful for providing operational data for other types of hydraulic, electric, or electromagnetic semi-active or active vehicular suspension systems. As shown in Figure 3, a linear sensor assembly 24 of the present invention includes a height sensing means 36 for determining the operational position of the vertical location of the road wheel and tire assemblies with respect to the body or chassis of the vehicle. Height sensor 36 includes a first sensor component 38 which slidably reciprocates within a second sensor component 40 as the road wheel and tire assembly 10 moves vertically with respect to the vehicle. Each of the first and second sensor components, 38, 40 respectively, includes a ball stud and socket assembly 42 for attaching the respective sensor components to the lower control arm 14 and the vehicle body 15 (Fig. 1). As shown in Figure 3, the height sensor 36 is a linear variable displacement transformer (LVDT) but it should be readily apparent to those skilled in the art that other types of height sensing means may also be utilised. Those skilled in the art will appreciate in view of this disclosure that other types of road wheel vertical position sensors such as the rotary Hall effect sensor shown in Figure 2 or other types of linear or rotary resolver devices may be applied according to the present invention. An acceleration sensing device, such as accelerometer 46, is mounted to the second sensor component of height sensor 36 by means of a bracket 48. Accelerometer 46 determines the acceleration of the vehicle body with respect to the surface upon which the vehicle is travelling. Accelerometer 46 may be of any known type of accelerometer such as a Piezo electric accelerometer, a Piezo resistive or a Piezo capacitive accelerometer. Accelerometer 46 is connected electrically to an integrated circuit board 44 mounted within bracket 48 of the second sensor component 40 of the height sensor 36. As will be explained in further detail below, the circuit board 44 is common to both the height sensor 36 and accelerometer 46 and supplies power to each sensing element from a vehicle power source such as the battery of the vehicle. The circuit board 44 includes a common oscillator circuit, a common input protection circuit and a power supply circuit so that a single circuit board may be utilised for both of the sensing elements. By contrast, the cited prior art teach separate circuit boards for each sensing element. By utilising a single circuit board for the unitary sensor assembly of the present invention, a significant cost saving and simplification of this circuit can be realised. Furthermore, it is advantageous to obtain vertical position information and acceleration information from the same vehicle point in many known control strategies for active suspension type vehicles. By placing the accelerometer 46 directly in the location of the height sensor 36, it is not necessary to derive the vertical velocity of the body with respect to the surface upon which the vehicle is travelling through lengthy and complex calculations of the position of the suspension members with respect to time as shown in the '203 patent. Furthermore, it should be readily apparent to those skilled in the art that the sensor assembly of the present invention could be used at each wheel location within the vehicle or could be used at both front wheels and one rear wheel of the vehicle to develop information needed for any control strategy which may be utilised in a controlled suspension system. A suspension control system utilising a sensor assembly of the present invention is valuable because the height sensor cooperates with the acceleration sensor and a suspension control module to produce signals indicative of not only the suspension's ride height but also indicating the relative velocity of the suspension and wheel and tire assembly with respect to the chassis at a common measuring point of the vehicle. Figure 4 shows a system block diagram of a suspension control system utilising a sensor assembly of the present invention. As shown in Figure 4, a vehicle power source, such as a battery 50, supplies power to the circuit board 44 common to both the suspension position sensor 36 and the suspension acceleration sensor 46. Each of these sensors 36, 46 generates a set of signals indicative of the suspension position and acceleration with respect to the surface upon which the vehicle is travelling and sends the signals to a suspension control module 52. The suspension control module interacts with the adjustable suspension units 20 to either vary the ride height or to control the damping of the suspension system to achieve optimum performance according to a variety of known control strategies. The suspension control module 52 generally comprises a microprocessor. The microprocessor generally comprises an input interface, a central processing unit (CPU), a readable, addressable memory (RAM), a read only memory (ROM) and an output interface. The microprocessor is connected to the position sensor 36 and acceleration sensor 46 by means of the input interface. It has been determined that a type 8797 microprocessor by Intel Corp. is useful for practicing the present invention. Those skilled in the art will appreciate in view of this disclosure that other types of microprocessors may be useful for practicing this invention. Referring now to Figure 5, during operation of a control system utilising a sensor assembly of the present invention, each of the position sensors 36 and the accelerometer 46 outputs a series of signals to the suspension control module 52. As stated above, the position sensor 36, through its sensing element 37, outputs a signal indicative of the operational position of the suspension with respect to the body of the vehicle while the accelerometer 46, though its sensing element 47, outputs a series of signals corresponding to the acceleration of the vehicle body with respect to the surface upon which the vehicle is travelling. As shown in Figure 5, each of these signals first passes through a filter 54, typically a low pass filter, which filters out all of the nonessential information generated by each sensor. It should be readily apparent to those skilled in the art that other types of known filters can be used depending on the control strategy employed by the apparatus. The signals then pass through an amplifier 56. The amplifier 56 puts each of the signals at a level that the suspension control module 52 can read and interpret. After leaving the amplifier 56, the signals each pass through a slope and offset adjustment device 58 which calibrates the signal to be readable by the control module 52. A feedback circuit 60 may also be employed as a reiterative means to insure the accuracy of the signal that the control module is receiving. It should be apparent to those skilled in the art that the signals from each of the position sensor and accelerometer 46 is generated independently and sent to microprocessor 52 independently of one another as shown by the separate lines of Figure 5. As further shown in Figure 5, the circuit board of the present invention utilises a common oscillator 64 of a known type, a common input protection circuit 62 comprising mainly capacitors, diodes or varisters to protect the circuit from electrical spikes from the input of the vehicle battery. The circuit board also includes a common power supply means 62 to transmit the power from the vehicle power source to each of the sensor elements. As such, the circuit board comprises an electrical power transmission means for transmitting the power from the vehicle battery to the position sensor 36 and the accelerometer 46 as well as supplying the power to send a signal from the sensor elements to the control module. Those skilled in the art will appreciate in view of this disclosure that a sensor assembly according to the present invention may be employed with a variety of known suspension control systems to provide information to those systems which is needed in the control strategies of the apparatus's. Furthermore, other types of detectors or switches could be employed within the height sensor according to the present invention, for example, magnetic reed switches or electromechanical devices could be utilised.

Claims: A unitary sensor assembly for use in an automotive vehicle having a source of electrical power (50), a body (15) and an automotive suspension relatively movable with respect to said body, comprising: a circuit board (44) electrically connected to said power source (50) and operative to supply power from said power source (50) to first and second sensor means (36,46), said circuit board (44) having an oscillator circuit, an electrical input protection circuit and an electrical power supply circuit; first sensor means (36) for determining the operational position of said suspension with respect to said body (15), said first sensor means (36) being electrically connected to said circuit board (44) and including a first sensor component (38) movable with respect to a second sensor component (40) and means (42) for attaching said first sensor component (38) to said suspension and said second sensor component (40) to said body (15) such that said first and second sensor components (38,40) will be caused to move with respect to one another when said suspension moves with respect to said body (15); and second sensor means (46) for determining the acceleration of said body (15) of said vehicle with respect to the surface upon which the vehicle is travelling, said second sensor means (46) also being electrically connected to said circuit board (44); characterised in that said second sensor means (46) is mounted to said second sensor component (40) of said first sensor means (36). An assembly according to claim 1 further characterised in that the circuit board (44) is mounted to said second sensor component (40) of said first sensor means (36). An assembly according to either claim 1 or claim 2 further characterised in that said second sensor component (40) includes a bracket (48) attached to the outer periphery thereof, said bracket (48) being configured to receive said circuit board (44) and second sensing means (46). An assembly as claimed in any one of the preceding claims in which the first sensor means (36) comprises a linear height sensor. An assembly as claimed in any one of claims 1 to 3 in which the first sensor means (36) comprises a rotary height sensor. An assembly as claimed in any one of the preceding claims in which said second sensor means (46) comprises an accelerometer.

Inventors: MORRIS PETER THOMAS, MORRIS, PETER THOMAS
Applicants: FORD FRANCE, FORD MOTOR CO, FORD WERKE AG, FORD FRANCE S. A., FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1991
Main classification: B60G17
IPC codes: B60G17