Vehicle height control apparatus

• US 4,733,875 A
• Filed: 04/21/1986
• Issued: 03/29/1988
• Est. Priority Date: 04/22/1985
• Status: Expired due to Term

• Current Assignee: Honda Elesys Co., Ltd. (Nidec Corporation)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company), NEC Home Electronics, Ltd. (NEC Corporation)
• Inventors: Yamashita, Seiji, Sato, Morio, Azuma, Toshiyuki, Hikichi, Koichi
• Primary Examiner(s): Weaver, Ross
• Application Number:
  US06/853,958
• Time in Patent Office: 708 Days
• Field of Search: 280/6 R, 280/6 H, 280/707, 280/DIG. 1, 280/714
• US Class Current: 280/6.159
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method

Abstract

A vehicle height control device that includes a pressure sensor 28 for detecting the pressure of compressed air supplied to pneumatic shock absorbers 10 for pneumatically bearing the load of a vehicle loads applied through the wheels. A control circuit 30 is included for controlling vehicle height based on the pressure detected by the pressure sensor 28. A waveform shaping circuit is connected between the control circuit 30 and the pressure sensor 28 and shapes the waveform to moderate the pressure change while the pressure is rising to a greater degree than while the pressure is dropping. The waveform shaping circuit includes a passive low-pass filter circuit 38, an active low-pass filter circuit 52 and a pair of diodes 70 and 72. The diodes 70 and 72 connected to the active filter circuit 52, allowing rapid capacitor discharge during decreases in signal amplitude while maintaining a slow discharge rate during decreases in signal amplitude.

Claims

1. A vehicle height control apparatus, receiving a vehicle height signal and controlling height using a pressurized fluid, said apparatus comprising:

pressure sensing means for producing a pressure signal waveform in dependence upon fluid pressure;

pressure signal compression means for amplitude compressing a rising portion of the pressure signal waveform more than a falling portion of the pressure signal waveform, a time constant of the falling portion of said pressure signal waveform being shorter than a time constant of the rising portion of said pressure signal waveform, causing the pressure to increase by a first speed during the rising portion and causing the pressure to decrease by a second speed faster than said first speed during the falling portion; and

height control means for controlling vehicle height in dependence upon the compressed waveform and the vehicle height signal.

2. A vehicle height control apparatus receiving a vehicle height signal, comprising:

height adjustment means for adjusting vehicle height using a pressurized fluid;

pressure sensing means for sensing the pressure of the pressurized fluid and producing a pressure signal having rising and falling portions each having a slope;

waveform shaping means for smoothing the pressure signal by decreasing the slope of the rising portion more than the slope of the falling portion, a time constant of the falling portion of said pressure signal waveform being shorter than a time constant of the rising portion of said pressure signal waveform, causing the pressure to increase by a first speed during the rising portion and causing the pressure to decrease by a second speed faster than said first speed during the falling portion; and

control means for controlling vehicle height in dependence upon the vehicle height signal and the smoothed pressure signal.

3. A vehicle height control apparatus receiving a vehicle height signal, comprising:

height adjustment means for adjusting vehicle height using a pressurized fluid;

pressure sensing means for sensing the pressure of the pressurized fluid and producing a pressure signal having rising and falling portions each having a slope;

waveform shaping means for smoothing the pressure signal by decreasing the slope of the rising portion more than the slope of the falling portion, said waveform shaping means comprising;

a passive low-pass filter operatively connected to said pressure sensing means;

a active low-pass filter operatively connected to said passive low-pass filter; and

a pair of diodes operatively connected between said pressure sensing means and said active low-pass filter; and

control means, operatively connected to said active low-pass filter, for controlling vehicle height in dependence upon the vehicle height signal and the smoothed pressure signal.

4. A vehicle height control apparatus, comprising:

a height control device for controlling vehicle height with a pressurized fluid;

a fluid pressure sensor connected to said height control device;

a passive low-pass filter operatively connected to said fluid pressure sensor;

an active low-pass filter connected to said passive low-pass filter;

a pair of diodes operatively connected between said fluid pressure sensor and said active low-pass filter;

an A/D converter connected to said active low-pass filter; and

a height control circuit connected to said A/D converter and said height control device.

5. An apparatus as recited in claim 4,

wherein said active low-pass filter comprises:

an operational amplifier having inverted and non-inverted inputs and having an output connected to the inverted input and said A/D converter;

a first capacitor connected to the inverted input;

a second capacitor connected between the non-inverted input and ground;

a first resistor connected to said passive low-pass filter and said first capacitor; and

a second resistor connected to the non-inverted input, said first resistor and said first capacitor, and

wherein said pair of diodes includes;

a first diode operatively connected between said first capacitor and said sensor; and

a second diode operatively connected between the non-inverted terminal and said sensor.