Pressure control system

• US 4,583,566 A
• Filed: 08/16/1983
• Issued: 04/22/1986
• Est. Priority Date: 08/16/1983
• Status: Expired due to Term

• Current Assignee: Paul V. Kalavitz, Ralph R. Griner
• Original Assignee: Paul V. Kalavitz, Ralph R. Griner
• Inventors: Griner, Ralph R., Kalavitz, Paul V.
• Primary Examiner(s): Chambers, A. Michael
• Assistant Examiner(s): Fox, John C.
• Application Number:
  US06/523,704
• Time in Patent Office: 980 Days
• Field of Search: 137/101.19, 137/224, 137/487.5, 364/183, 364/55, 361/167, 361/187, 307/10 R, 152/415, 152/416
• US Class Current: 137/101.19
• CPC Class Codes: B60C 23/001 Devices for manually or automatically controlling or distributing tyre pressure whilst the vehicle is moving
• CPC Class Codes: G05D 16/2053 the plurality of throttling means comprising only a first throttling means acting on a higher pressure and a second throttling means acting on a lower pressure, e.g. the atmosphere
• CPC Class Codes: Y10T 137/2529 With electrical controller
• CPC Class Codes: Y10T 137/36 With pressure-responsive pressure-control means

Abstract

A highly accurate pressure control system (200) adapted to control fluid pressure in apparatus such as the air pressure in vehicle tires (136) comprises a control module (210) having an air pressure selector (211) for selecting a desired air pressure and a pressure to voltage transducer circuit (230) for generating a signal representative of the actual air pressure. Signals representative of the difference between actual and desired air pressure are applied to comparator circuitry (246, 248) which control output switches (254, 256) for activating an inflate/deflate valve (220) to inflate or deflate the tires (136) so as to achieve and maintain the desired air pressure. Various circuitry of the control module (210) employ reference signals maintained at reference values held constant relative to a common power supply voltage instead of to a ground reference (218), thus minimizing circuit count and power dissipation while providing sufficient current for operating output switches (254, 256).

Claims

1. In a pressure control system for regulating the actual fluid pressure in fluid-filled apparatus such as pneumatic devices and the like in accordance with an adjustable desired fluid pressure, wherein the system comprises a source of compressed fluid, means for selecting the desired fluid pressure, valve means connected to the apparatus and selectively connectable to the source of compressed fluid for selectively increasing, decreasing and maintaining the fluid pressure in the apparatus, and control means responsive to the actual fluid pressure and the selection of desired fluid pressure to operate the valve means in accordance with the difference between the actual and desired fluid pressure, the improvement wherein the control means comprises:

transducer means connected to the apparatus and responsive to the actual fluid pressure to generate an electrical transducer signal continuously proportional to the magnitude of the actual fluid pressure;

first circuit means connected to the means for selecting the desired fluid pressure and to the transducer means, and responsive to the transducer signal for generating electrical valve control signals representative of the polarity of the difference between the desired fluid pressure and the actual fluid pressure;

the valve means is responsive to the electrical valve control signal to continuously and selectively increase or decrease the actual fluid pressure in the apparatus until the actual fluid pressure is within a predetermined range of the desired fluid pressure; and

the first circuit means comprises proportional signal generating means connected to the transducer means and to the means for selecting the desired fluid pressure, and responsive to the transducer signal and the particular selected desired fluid pressure for generating a first difference signal having a value continuously proportional to the magnitude and polarity of the difference between the actual fluid pressure and the desired fluid pressure during increase and decrease of the actual air pressure.

2. A pressure control system in accordance with claim 1 characterized in that the value of the first difference signal is equal to a nonzero reference level independent of the absolute magnitude of the transducer signal when the difference between the actual and desired fluid pressures is substantially equal to zero.

3. A pressure control system in accordance with claim 1 characterized in that the first circuit means further comprises:

power supply means for generating power supply signals;

reference signal generating means connected to the power supply means for generating second and third reference signals having magnitudes of second and third reference levels, respectively; and

comparator means connected to the proportional signal generating means and the reference signal generating means for comparing the first difference signal with the second and third reference signals, and generating comparison signals in accordance with the results of the comparison.

4. A pressure control system in accordance with claim 3 characterized in that the first circuit means further comprises switch means connected to the comparator means and to the valve means, and responsive to the comparison signals for selectively generating the electrical valve control signals.

5. A pressure control system in accordance with claim 1 characterized in that the first circuit means further comprises:

power supply means connected to the transducer means for generating power supply signals;

reference signal generating means connected to the power supply means and to the proportional signal generating means, and responsive to the power supply signals for generating a first reference signal proportional to the power supply signals;

the proportional signal generating means is further responsive to the first reference signal for generating the first difference signal;

the transducer means is further responsive to the power supply signals for generating the transducer signal; and

variations in the power supply signal values will result in proportional changes in the transducer signal and the first reference signal so as to maintain accuracy in the operation of the pressure control system in a manner independent of power supply signal variations.

6. A pressure control system in accordance with claim 1 characterized in that the first circuit means further comprises:

power supply means connected to the transducer means for generating power supply signals;

reference signal generating means connected to the power supply means for generating second and third reference signals having magnitudes of second and third reference levels, respectively, wherein the second reference level is greater in magnitude than the third reference level; and

comparator means connected to the proportional signal generating means and responsive to the magnitude of the first difference signal being greater than the second reference level for generating a first comparison signal, and further responsive to the magnitude of the first difference signal being less than the third reference level for generating a second comparison signal.

7. A pressure control system in accordance with claim 6 characterized in that the comparator means further comprises hysteresis means for providing hysteresis about upper and lower values of difference between the actual and desired fluid pressures at which the first and second comparison signals are generated.

8. A pressure control system in accordance with claim 7 characterized in that said hysteresis means comprises at least one series connection of a diode and a resistance interconnected within the comparator means so that the diode is forward-biased in the presence of the first comparison signal, and reverse-biased in the absence of the first comparison signal, thereby isolating the effects of the hysteresis means in the absence of the first comparison signal.

9. A pressure control system in accordance with claim 7 characterized in that the valve means is responsive to the first one of the electrical valve control signals to decrease the actual fluid pressure, and further responsive to the second one of the electrical valve control signals to connect the source of compressed fluid to the apparatus so as to increase the actual fluid pressure.

10. A pressure control system in accordance with claim 6 characterized in that the first circuit means further comprises:

switch means connected to the comparator means and responsive to the first comparison signal to generate a first one of the electrical valve control signals, and further responsive to the second comparison signal to generate a second one of the electrical valve control signals.

11. A pressure control system in accordance with claim 1 characterized in that the first circuit means further comprises:

power supply means connected to the transducer means for generating a first power signal and a power supply common signal;

reference signal generating means connected to the power supply means and to the proportional signal generating means for generating first, second and third reference signals having first, second and third reference levels, respectively, wherein each of said reference levels is proportional to the difference in magnitudes of the first power signal and the power supply common signal; and

the proportional signal generating means comprises second circuit means connected to the means for selecting the desired fluid pressure and to the transducer means for generating a second difference signal proportional to the difference between actual and desired fluid pressures, wherein the magnitude of the second difference signal is equal to the first reference level when the actual fluid pressure is substantially equal to the desired fluid pressure.

12. A pressure control system in accordance with claim 11 characterized in that the second circuit means comprises a voltage divider circuit connected to the means for selecting a desired fluid pressure, an operational amplifier having input terminals connected to the transducer means and the voltage divider circuit, and an output terminal connected to the voltage divider circuit, wherein the second difference signal is generated on the output terminal and the magnitude of the second difference signal when the actual fluid pressure is equal to the desired fluid pressure corresponds to the magnitude of the transducer signal when the actual fluid pressure is equal to the maximum selectible magnitude of desired fluid pressure.

13. A pressure control system in accordance with claim 11 chracterized in that the proportional signal generating means further comprises amplifier means connected to the second circuit means and the reference signal generating means, and responsive to the second difference signal and the first reference signal for providing gain to the second difference signal and generating the first difference signal, wherein the magnitude of the first difference signal is equal to the magnitude of the second difference signal when the actual fluid pressure is substantially equal to the desired fluid pressure.

14. A pressure control system in accordance with claim 13 characterized in that the first circuit means further comprises:

comparator means connected to the amplifier means and to the reference signal generating means, and responsive to the magnitude of the first difference signal being greater than the second reference level for generating a first comparison signal, and further responsive to the magnitude of the first difference signal being less than the third reference level for generating a second comparison signal;

switch means connected to the comparator means and responsive to the first comparison signal to generate a first one of the electrical valve control signals, and further responsive to the second comparison signal to generate a second one of the electrical valve control signals; and

the valve means is responsive to the first one of the electrical valve control signals to actuate deflation of the fluid-filled apparatus, and further responsive to the second one of the electrical valve control signals to connect the source of fluid to the fluid apparatus so as to increase the apparatus actual fluid pressure.

15. A pressure control system in accordance with claim 13 characterized in that power supply signals for operating active circuitry of the proportional signal generating means, reference signal generating means and comparator means are independent of an absolute ground reference.

16. In a pressure control system mounted to a vehicle for inflating and deflating the actual air pressure of pneumatic vehicle tires in accordance with a desired air pressure adjustably and remotely selected by a vehicle operator, wherein the system comprises a source of compressed air mounted to the vehicle, means mounted within the vehicle cab for selecting the desired air pressure, valve means connected to the pneumatic apparatus and selectively connectable to the source of compressed air for selectively inflating, deflating and maintaining the actual air pressure in the vehicle tires, and control means responsive to the actual air pressure and the selected desired air pressure to operate the valve means in accordance with the difference between the actual and desired air pressures, the improvement wherein the vehicle includes power supply means and the control means comprises:

transducer means connected to the vehicle tires and to the vehicle power supply means, and responsive to the actual air pressure in the vehicle tires to generate an electrical transducer signal continuously proportional to the magnitude of the actual air pressure;

first circuit means connected to the power supply means and to the means for selecting the desired air pressure, and responsive to the transducer signal for continuously generating electrical valve control signals representative of the polarity of the difference between the desired air pressure and the actual air pressure; and

the valve means is responsive to the electrical valve control signals to continuously and selectively inflate or deflate the actual air pressure in the vehicle tires until the actual air pressure is within a predetermined range of the selected desired air pressure.

17. A pressure control system in accordance with claim 16 characterized in that the first circuit means comprises:

reference signal generating means connected to the vehicle power supply means for generating first, second and third reference signals having first, second and third reference levels, respectively;

voltage follower means connected to the transducer means and to the means for selecting the desired air pressure, and responsive to the transducer signal and a particular selected desired air pressure for generating a voltage follower signal having a magnitude proportional to the magnitude of the difference between actual and desired air pressures, wherein the magnitude of the follower signal will be equal to the first reference signal when the actual air pressure is substantially equal to the desired air pressure;

amplifier means connected to the voltage follower means and to the reference signal generating means, and responsive to the follower signal and the first reference signal for generating a difference signal having a magnitude and polarity proportional to the difference between the actual and desired air pressures;

comparator means connected to the reference signal generating means and to the amplifier means, for comparing the difference signal with the second and third reference signals, and for generating comparison signals in accordance with the result of the comparison; and

switch means connected to the comparator means and responsive to the comparison signals for generating the electrical valve control signals.

18. A pressure control system in accordance with claim 16 characterized in that the system further comprises:

an air line connected to the vehicle tires for applying the actual air pressure to the transducer means; and

damping means connected to the air line for minimizing excursions in the actual air pressure applied to the transducer means, where such changes are effected by momentary changes in the actual air pressure in the vehicle tires caused by transient road or terrain conditions.