Shock absorber with sonar position sensor

• US 5,104,144 A
• Filed: 09/25/1990
• Issued: 04/14/1992
• Est. Priority Date: 09/25/1990
• Status: Expired due to Term

• Current Assignee: Tenneco Automotive Operating Company Incorporated (Apollo Global Management, Inc.)
• Original Assignee: Monroe Auto Equipment Company (Apollo Global Management, Inc.)
• Inventors: Bethell, Michael R.
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): Hurley, Kevin
• Application Number:
  US07/587,981
• Time in Patent Office: 567 Days
• Field of Search: 280/707, 280/702
• US Class Current: 188/284
• CPC Class Codes: B60G 17/01933 Velocity, e.g. relative velocity-displacement sensors
• CPC Class Codes: B60G 2202/24 Fluid damper
• CPC Class Codes: B60G 2400/25 Stroke; Height; Displacement
• CPC Class Codes: B60G 2400/91 Frequency
• CPC Class Codes: B60G 2401/15 Doppler effect
• CPC Class Codes: B60G 2401/176 Radio or audio sensitive means, e.g. Ultrasonic
• CPC Class Codes: B60G 2500/10 Damping action or damper
• CPC Class Codes: B60G 2600/90 other signal treatment means
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00

Abstract

A damping device operable to change a suspension characteristic of a vehicle in response to changes in a relative relationship between the piston and the cylinder of the damping device. The damping device comprising a pressure cylinder forming a working chamber operable to store damping fluid. A piston is disposed within the pressure cylinder defining an upper and lower portion of the working chamber. The damping device further comprises a transducer for emitting and receiving sound waves within the lower portion of the working chamber. The sound waves emitted by said transducer are reflected by the end surface of the cylinder or a base valve mounted at the end of the cylinder and are received by said transducer. A timing circuit determines the difference in time between the emitted and reflected sound waves and generates an output in response thereto. A central processor calculates the desired relative relationship, such as the relative distance between the piston and the base valve, from the output of the timing circuit.

Claims

1. A hydraulic actuator connecting the sprung and unsprung portions of a vehicle, said hydraulic actuator operable to selectively change a suspension parameter in response to changes in a relative relationship between a telescopically movable component and a stationary component of said hydraulic actuator, comprising:

a cylinder forming a working chamber operable to store damping fluid;

a piston disposed within said cylinder defining a first and a second portion of said working chamber, said piston being movable within said cylinder;

transducer means for emitting and receiving sound waves propagating through damping fluid contained within said second portion of said working chamber;

means for driving said transducer means so as to cause said transducer means to emit sound waves, said means for driving being operable to cause said transducer means to emit said sound waves in response to a first electrical signal;

means for reflecting sound waves emitted by said transducer means, said reflecting means being disposed within said cylinder;

timing means for determining the time between a sound wave emitted by said transducer means and reception of a reflection of said sound waves by said transducer means, said timing means generating an output in response thereto, said timing means including switch means for electrically connecting said transducer means to said means for driving upon receipt of said first electrical signal, said switch means being further operable to electrically connect said transducer means to said timing means in the absence of said first electrical signal;

means for calculating the relative relationship between said piston within said cylinder in response to said output from said timing means; and

a control circuit operable selectively change said suspension parameter in response to the relative relationship of said piston within said cylinder.

2. The hydraulic actuator according to claim 1, wherein said actuator is a hydraulic direct acting, telescopic, shock absorber.

3. The hydraulic actuator according to claim 1, wherein the frequency of the sound waves emitted by said first transducer means residue within the ultrasonic spectrum.

4. The hydraulic actuator according to claim 3, wherein said driving means comprises a wave generating circuit operable to cause said transducer means to generate ultrasonic waves.

5. The hydraulic actuator according to claim 4, wherein said wave generation circuit enables said transducer means to generate pulsed ultrasonic waves having a fixed controlled frequency and duration.

6. The hydraulic actuator according to claim 5 further comprising a piston rod for supporting said piston in said working chamber, said transducer means comprises a transmitter mounted to said piston on a surface opposite said piston rod and being operable to propagate ultrasonic waves through said damping fluid contained in said second portion of said working chamber.

7. The hydraulic actuator according to claim 6, wherein said transducer means also acts as a receiver.

8. The hydraulic actuator according to claim 7, wherein said transducer means comprise piezoelectric transducers.

9. The hydraulic actuator according to claim 7, wherein said transducer means comprises magnetorestrictive transducers.

10. The hydraulic actuator according to claim 1, wherein said reflecting means comprises a base valve disposed within said cylinder.

11. The hydraulic actuator according to claim 10, wherein said base valve further comprises means for compensating for changes in the speed of propagation of said sound waves.

12. The hydraulic actuator according to claim 1, wherein said reflecting means comprises a bottom end surface of said cylinder.

13. The hydraulic actuator according to claim 1, wherein said timing means comprises a timing circuit operable to continuously generate an output in response to the time between a sound wave being emitted by said transducer means and a reflection of said sound wave being received by said transducer means.

14. The hydraulic actuator according to claim 1, wherein said means for calculating the relative relationship between said piston and said cylinder comprises an electronic processor.

15. A method of determining the relative displacement between a piston and a stationary surface within a pressure cylinder of a direct acting shock absorber, said method comprising the steps of:

delivering an electrical signal generated by a wave generation circuit to an ultrasonic transmitter through a first electrical path including at least a two-position switch when said switch is in a first position, said ultrasonic transmitter operable to emit pulsed ultrasonic waves of fixed and controlled frequency in response to said electrical signal generated by said wave generation circuit, said switch being operable to allow electric current to flow in a second electrical path when said switch is in a second position;

changing the position of said switch from said first position to said second position so as to allow electric current to flow through said second electrical path;

reflecting said ultrasonic waves emitted by said ultrasonic transmitter against a fixed inner surface of said pressure cylinder;

receiving said ultrasonic wave reflected by said fixed inner surface by an ultrasonic receiver through said second electrical path;

changing the position of said switch from said second position to said first position so as to allow electrical current to flow through said first electrical path;

providing timing means for determining the time an emitted ultrasonic wave takes to be reflected back to said receiver, and generating an output signal in response thereto; and

calculating the relative distance between said piston and said fixed inner surface in response to said output signal from said timing means.

16. The method of claim 15 further comprising the step of selectively changing a suspension parameter of said shock absorber in response to said calculated relative distance between said piston and said fixed inner surface.

17. The method of claim 16, wherein said transmitter and said receiver comprise a single piezoelectric transducer.

18. The method of claim 16, wherein said piston has a first surface facing said fixed inner surface of said pressure cylinder, said piezoelectric transducer being mounted to said first surface of said piston.

19. The method of claim 18, wherein said step of calculating said relative movement between said piston and said fixed inner surface comprises delivering said output signal from said timing circuit to a central processor, said central processor calculating said relative distance from said output.

20. A direct acting hydraulic shock absorber operable to selectively vary a suspension characteristic thereof in response to the relative displacement between a movable and a stationary component, said shock absorber comprising:

a pressure cylinder forming a working chamber operable to store damping fluid;

a piston disposed within said pressure cylinder defining a first and second portion of said working chamber, said piston being movable with respect to said pressure cylinder and comprising valve means for metering the flow of damping fluid between said first and second portions of said working chamber during movement of said piston within said pressure cylinder;

transducer means for emitting and receiving sound waves propagating through said damping fluid contained within said second portion of said working chamber, said transducer means being mounted to said piston;

means for driving said transducer means being operable to cause said transducer means to emit sound waves upon generation of a first electrical signal;

a base valve operable mounted to an end surface of said second portion of said working chamber, said base valve operable to reflect sound waves emitted by said transducer means, said base valve having means for compensating for variations in the speed of propagation of said sound waves through said damping fluid;

a timing circuit for measuring the difference in time of said sound wave emitted by said transducer means and said sound waves received by said transducer means, and generating an output in response thereto, said timing circuit including switch means for electrically connecting said transducer means to said means for driving upon receipt of said first electrical signal, said switch means being further operable to electrically connect said transducer means to said timing means in the absence of said first electrical signal;

a computer for calculating the distance between said piston and said base valve from said output of said timing circuit; and

a piston control circuit for selectively controlling said valve means so as to change the flow of damping fluid in said shock absorber in response to the distance between said piston and said base valve.

21. The direction acting hydraulic shock absorber according to claim 20, wherein said sound waves emitted by said transducer means reside within the ultrasonic spectrum.

22. The direct acting hydraulic shock absorber according to claim 21, wherein said means for driving said transducer means comprises a wave generation circuit, said wave generation circuit operable to cause said transducer means to generate constant frequency ultrasonic wave.

23. The direct acting hydraulic shock absorber according to claim 22, wherein said wave generation circuit is operable to generate at modulated pulsed signal.

24. The direct acting hydraulic shock absorber according to claim 22, wherein said transducer means comprise piezoelectric devices.

25. The direct acting hydraulic shock absorber according to claim 22, wherein said transducer means comprise magnetorestrictive devices.

26. The direct acting hydraulic shock absorber according to claim 22, wherein said frequency detection circuit continuously generates an output in response to change in distance between said piston and said base valve.

27. The direct acting hydraulic shock absorber according to claim 20, wherein said compensation means associated with said base valve comprises a step-like base valve having first and second reflecting surfaces, said first and second reflecting surfaces separated by a predetermined axial distance such that said transducer means receives two distinct sound waves reflected by said first and second reflecting surface, respectively, so as to define a reference signal.