Automatic vehicle level control

• US 4,540,188 A
• Filed: 04/19/1984
• Issued: 09/10/1985
• Est. Priority Date: 04/19/1984
• Status: Expired due to Fees

• Current Assignee: General Motors Auto OOO (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Meloche, Kenneth R., Libkie, Herbert A., McLeish, James G.
• Primary Examiner(s): Bertsch, Richard A.
• Application Number:
  US06/601,936
• Time in Patent Office: 509 Days
• Field of Search: 280/6 R, 280/6.1, 280/6 H, 280/707, 280/714, 267/64.16
• US Class Current: 280/6.158
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method

Abstract

A level control system for a wheeled motor vehicle with sprung and unsprung masses, an accessory the activation of which indicates the probability of an associated vehicle load change, fluid power apparatus activatable to level the sprung mass relative to the unsprung mass and sensor apparatus effective to periodically indicate a trim or out-of-trim level condition according to predetermined criteria further comprises apparatus defining a service mode with a time period shorter than a predetermined activation time of the fluid power apparatus which avoids overshoot in level adjustment, a cruise mode with a time period longer than the out-of-trim duration of a predetermined long highway feature and a decision mode with a time period of duration intermediate the service and cruise time period durations and longer than the period of sprung mass oscillation during vehicle movement. It further comprises logic control apparatus effective to select from the service, cruise and decision time modes for the determination of trim level condition based on the previous mode, the trim level determination in the previous period and detection of an actuation of the accessory, with the decision mode being selected upon the initiation of system operation and as an intermediate step between service and cruise modes.

Claims

1. A level control system for a wheeled motor vehicle with sprung and unsprung masses and an accessory the activation of which indicates the probability of an associated vehicle load change, the system having fluid power means activatable to level the sprung mass relative to the unsprung mass within a predetermined trim band, said system comprising:

sampling sensor means effective to indicate the height of said sprung mass relative to said trim band;

signal generating means responsive to said sensor means for a selected time period to periodically generate a signal indicating whether said sprung mass is above, within or below said trim band for said time period according to predetermined criteria;

means defining a service time period shorter than a predetermined activation time of said fluid power means which avoids overshoot in level adjustment, a cruise time period longer than the out-of-trim duration of a predetermined long highway feature and a decision time period of duration intermediate the service and cruise time period durations and longer than the period of sprung mass oscillation during vehicle movement;

means effective to initiate system operation with vehicle operation and select said decision time period;

means responsive to a predetermined number of consecutive decision time periods with no above-trim or below-trim signals to select said cruise time period;

means responsive to an above-trim or below-trim signal in a cruise time period to select said decision time period;

means responsive to an above-trim or below-trim signal in a decision time period to activate said fluid power means and select said service time period;

p1 means responsive to a within-trim signal in a service time period to deactivate said fluid power means and select said decision time period;

sensor means effective to generate a signal whenever said accessory is activated; and

means responsive to a signal from said sensor means during a cruise time period to immediately initiate a decision time period, whereby fast reaction to a vehicle load change is effected.

2. A level control system for a wheeled motor vehicle with sprung and unsprung masses and at least one door having alternative open and closed states, the system having fluid power means activatable to level the sprung mass relative to said unsprung mass within a predetermined trim band, said system comprising:

sampling sensor means effective to indicate the height of said sprung mass relative to said trim band;

signal generating means responsive to said sensor means for a selected time period to periodically generate a signal indicating whether said sprung mass is above, within or below said trim band for said time period according to predetermined criteria;

means defining a service time period shorter than a predetermined activation time of said fluid power means which avoids overshoot in level adjustment, a cruise time period longer than the out-of-trim duration of a predetermined long highway feature and a decision time period of duration intermediate the service and cruise time period durations and longer than the period of sprung mass oscillation during vehicle movement;

means effective to initiate system operation with vehicle operation and select said decision time period;

means responsive to a predetermined number of consecutive decision time periods with no above-trim or below-trim signals to select said cruise time period;

means responsive to an above-trim or below-trim signal in a cruise time period to select said decision time period;

means responsive to an above-trim or below-trim signal in a decision time period to activate said fluid power means and select said service time period;

means responsive to a within-trim signal in a service time period to deactivate said fluid power means and select said decision time period;

a door sensor effective to generate a signal whenever said door changes between an open state and a closed state; and

means responsive to a signal from said door sensor during a cruise time period to immediately initiate a decision time period.

3. A level control system for a wheeled motor vehicle with sprung and unsprung masses and an ignition switch controlling vehicle operation with on and off states, the system having fluid power means activatable to level the sprung mass relative to said unsprung mass within a predetermined trim band, said system comprising:

sampling sensor means effective to indicate the height of said sprung mass relative to said trim band;

signal generating means responsive to said sensor means for a selected time period to periodically generate a signal indicating whether said sprung mass is above, within or below said trim band for said time period according to predetermined criteria;

means defining a service time period shorter than a predetermined activation time of said fluid power means which avoids overshoot in level adjustment, a cruise time period longer than the out-of-trim duration of a predetermined long highway feature and a decision time period of duration intermediate the service and cruise time period durations and longer than the period of sprung mass oscillation during vehicle movement;

means effective to initiate system operation with vehicle operation and select said decision time period;

means responsive to a predetermined number of consecutive decision time periods with no above-trim or below-trim signals to select said cruise time period;

means responsive to an above-trim or below-trim signal in a cruise time period to select said decision time period;

means responsive to an above-trim or below-trim signal in a decision time period to activate said fluid power means and select said service time period;

means responsive to a within-trim signal in a service time period to deactivate said fluid power means and select said decision time period;

an ignition switch sensor effective to generate a signal whenever said ignition switch assumes an off state; and

means responsive to a signal from said ignition switch sensor to immediately initiate a decision time period and prevent further selection of a cruise time period, said means further maintaining level system operation for at least a predetermined finish time after the ignition switch off state is sensed, whereby the level of the vehicle may be adjusted after it is unloaded.