Method and apparatus for automatic transmission cruise control

• US 4,660,672 A
• Filed: 10/15/1984
• Issued: 04/28/1987
• Est. Priority Date: 10/15/1983
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Katou, Yuuji
• Primary Examiner(s): Mitchell, David M.
• Application Number:
  US06/660,962
• Time in Patent Office: 925 Days
• Field of Search: 180/179, 180/178, 180/177, 180/176, 180/175, 74/866, 74/868, 74/877, 74/878, 74/336 R, 74/869, 364/426, 364/431.07, 364/424.1
• US Class Current: 180/175
• CPC Class Codes: B60K 31/047 the memory being digital
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: F16H 61/10 Controlling shift hysteresis

Abstract

In order to prevent hunting between a selected gear ratio (e.g. overdrive) and the next lower one, when a vehicle ascends a slope or incline under "cruise control" an automatic speed control device (ASCD) which controls the opening of the engine throttle under the cruise control mode, upon being put into operation issues a control signal to the transmission control circuit which allows the latter to upshift the transmission to the predetermined gear ratio (viz., overdrive) and which renders the transmission control circuit incapable of downshifting to the next lower gear while the ASCD is functioning. Upon the vehicle speed falling a predetermined amount below the preselected target value, the ASDC issues a signal directly to the transmission to cause a downshift to the next lower gear ratio. Following such a downshift, the ASDC inhibits subsequent upshifting either for a predetermined period of time or until the load which necessitated the downshift disappears.

Claims

1. A method of automatically controlling the speed of an automotive vehicle having an engine and a transmission, at a preselected target value comprising the steps of:

actuating a vehicle speed control device to control an actuator operatively connected with a throttle valve of said engine in a manner to vary the opening degree of said throttle valve in place of a manually produced signal in a manner to maintain said preselected target speed;

rendering a transmission control circuit which is discrete from said vehicle speed control device and which controls the shifting of said transmission between a plurality of forward speed ratios in accordance with a predetermined shift schedule, incapable of downshifting said transmission from a preselected gear ratio to the next lower one once said transmission control circuit has upshifted said transmission to said predetermined gear ratio irrespective of the changes in vehicle speed and engine load at all times when said speed control device is actuated;

using said vehicle speed control device to induce a downshift from said predetermined gear ratio to the next lower one, if the load on said engine increases to a level whereat the vehicle speed falls a predetermined amount below said target level; and

maintaining said downshift until a predetermined phenomenon occurs.

2. A method as claimed in claim 1, wherein said step of maintaining said downshift includes holding said downshift for a predetermined period of time after the downshift occurs and the vehicle speed has returned to said target level.

3. In an automotive vehicle

an engine having a throttle valve;

a throttle valve position sensor for generating a first signal indicative of the position of said throttle valve;

an actuator for moving said throttle valve;

a vehicle speed sensor for generating a second signal indicative of the speed of said vehicle;

an automatic transmission having a plurality of forward speeds;

a transmission control circuit for controlling the shifting between said plurality of forward speeds in response to said first and second signals;

a solenoid valve integrated with said transmission control circuit, said solenoid valve being operable to selectively inhibit said transmission from operating in a preselected gear ratio;

selectively operable vehicle speed control means which is responsive to said second signal for;

(a) rendering said transmission control circuit incapable of downshifting said transmission from said predetermined gear ratio to the next lower one upon having upshifted said transmission to said predetermined gear ratio at all times when said speed control means is operating;

(b) controlling said actuator in a manner to control the position of said throttle valve so as to maintain the vehicle speed essentially constant at a predetermined target value;

(c) issuing a downshift command to said solenoid valve to cause a downshift from said predetermined gear ratio to the next lower one upon the load on said engine increasing to a level whereat the vehicle speed falls a predetermined amount below said target value; and

(d) maintaining said downshift condition until a predetermined phenomenon occurs.

4. A vehicle as claimed in claim 3, wherein said transmission takes the form of a four forward speed transmission wherein said fourth speed is an overdrive ratio and wherein said predetermined gear ratio is said fourth speed ratio.

5. A vehicle as claimed in claim 3, wherein said predetermined phenomenon is the expiry of a predetermined time from the time of downshift and the return of the vehicle speed to said target level.

6. In an automotive vehicle

an engine having a throttle valve;

a throttle valve position sensor for generating a first signal indicative of the position of said throttle valve;

an actuator for moving said throttle valve;

a vehicle speed sensor for generating a second signal indicative of the speed of said vehicle;

an automatic transmission having a plurality of forward speeds;

a transmission control circuit for controlling the shifting between said plurality of forward speeds in response to said first and second signals;

a solenoid valve integrated with said transmission control circuit, said solenoid valve being operable to selectively inhibit said transmission from operating in a preselected gear ratio;

selectively operable vehicle speed control means which is responsive to said second signal for;

(a) rendering said transmission control circuit incapable of downshifting said transmission from said predetermined gear ratio to the next lower one upon having upshifted said transmission to said predetermined gear ratio;

(b) controlling said actuator in a manner to control the position of said throttle valve so as to maintain the vehicle speed essentially constant at a predetermined target value;

(c) issuing a downshift command to said solenoid valve to cause a downshift from said predetermined gear ratio to the next lower one upon the load on said engine increasing to a level whereat the vehicle speed falls a predetermined amount below said target value; and

(d) maintaining said downshift condition until the reduction of the load on said engine to a level whereat said preselected vehicle speed can be maintained in said next lower gear ratio without opening said throttle valve beyond a predetermined limit.

7. A method of automatically controlling the speed of an automotive vehicle having an engine and a transmission, at a preselected target value comprising the steps of:

using a vehicle speed control device to vary the opening degree of a throttle valve associated with said engine in place of a manually produced signal in a manner to maintain said preselected target speed;

rendering a transmission control circuit which controls the shifting of said transmission between a plurality of forward speed ratios, incapable of downshifting said transmission from a preselected gear ratio to the next lower one once said transmission control circuit has upshifted said transmission to said predetermined gear ratio irrespective of the changes in vehicle speed and engine load sensed by a vehicle speed sensor and an engine load sensor, respectively;

using said vehicle speed control device to induce a downshift from said predetermined gear ratio to the next lower one, if the load on said engine increases to a level whereat the vehicle speed falls a predetermined amount below said target level; and

maintaining said downshift until the load on said engine which induced said downshift reduces to a level whereat said vehicle can be operated at the target speed without opening said throttle valve beyond a predetermined amount while said transmission is in said next lower gear ratio.