Down shift inhibitor system for automatic transmission control

• US 3,927,579 A
• Filed: 03/14/1974
• Issued: 12/23/1975
• Est. Priority Date: 03/14/1974
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Kenneth Frank Golan
• Inventors: Golan, Kenneth Frank
• Primary Examiner(s): Wyche, Benjamin W.
• Assistant Examiner(s): Chandler, Lance W.
• Application Number:
  US05/451,012
• Time in Patent Office: 649 Days
• Field of Search: 74/861,862,863,864,865,866,867,869,752C
• US Class Current: 475/119
• CPC Class Codes: F16H 2061/166 Preventing or initiating shifts for preventing stall or overspeed of engine
• CPC Class Codes: F16H 61/0274 Control units where shifting is directly initiated by the driver, e.g. semi-automatic transmissions generation of movements for final actuating mechanisms F16H61/28
• CPC Class Codes: F16H 61/16 Inhibiting or initiating shift during unfavourable conditions, e.g. preventing forward reverse shift at high vehicle speed, preventing engine over speed unintentional control input F16H61/18

Abstract

An automatic transmission control for the automatic range of a transmission has a power control valve for selecting a desired gear ratio with a manual control valve operable to set the desired gear selection and a plurality of selector valves automatically operated to set the power control valve dependent upon the transmission output speed and up to a highest gear selection selected by an operator. The action of the selector valves is inhibited in down shift of the transmission as demanded by physical movement of the manual control valve to a lower gear setting until a predetermined transmission output speed is reached to avoid overspeeding of the engine.

Claims

1. A hydraulic control system for a multispeed transmission having drive components associated to produce a preselected group of gear ratios in an automatic range of operation, said control system comprising:

a manual control valve;

a group of automatic selector valves;

a power control valve;

fluid conduit connections interconnecting said manual control valve with both said group of automatic selector valves and said power control valve;

said power control valve connected to gear ratio control means for producing a selected gear ratio in the automatic range;

governor means for simultaneously establishing plural governor pressures dependent upon transmission output speed, means for applying each of the governor pressures to a different one of the automatic selector valves, means for applying a reference pressure to each of the last-mentioned selector valves in opposition to the governor pressure, means including the selector valves responsive to variations in transmission output speed and governor pressure to automatically up shift and down shift the transmission within the automatic range of operation and up to the highest gear selected by positioning of said manual control valve; and

means for inhibiting a forced down shift of said transmission as demanded by positioning of the manual control valve at a lower gear setting until a predetermined transmission output speed is reached, including a first valve member of a selector valve subjected at opposite ends thereof to said reference pressure and said governor pressure, respectively, and additional parts of a selector valve adjacent the first valve member which are inactive in said automatic up shift and down shift operation and having a first selected area against which a forced down shift pressure is applied by movement of the manual control valve to urge the first valve member in a direction opposed by said governor pressure and a larger second area which is subjected to the forced down shift pressure only after a forced down shift of the first valve member to hold the particular selector valve in downshifted position.

2. A hydraulic control system for a multispeed transmission having drive components associated to produce a preselected group of gear ratios In an automatic range of operation, said control system comprising:

a manual control valve;

a group of automatic selector valves;

a power control valve;

fluid conduit connections interconnecting said manual control valve with both said group of automatic selector valves and said power control valve;

said power control valve connected to gear ratio control means for producing a selected gear ratio in the automatic range;

means including the selector valves responsive to variations in transmission output speed to automatically up shift and down shift the transmission within the automatic range of operation and up to the highest gear selected by positioning of said manual control valve;

governor means for simultaneously establishing plural governor pressures dependent upon transmission output speed;

means for applying each of the governor pressures to a different one of the automatic selector valves;

means for applying a reference pressure to each of the last-mentioned selector valves in opposition to the governor pressure to obtain said automatic up shift and down shift operation;

each of the selector valves having a first valve member subject at opposite ends thereof to said opposing reference pressure and governor pressure for said automatic up shift and down shift operation and having a second valve member adjacent the first valve member and which is inactive in said automatic up shift and down shift operations and having a selected area and a larger area with said larger area selectively acted upon by the forced down shift pressure signal to hold the selector valve in a down shift position after a forced down shift has been effected;

means responsive to movement of the manual control valve for selectively applying a forced down shift pressure to said selected area of one or more of the selector valves in opposition to the governor pressure whereby forced down shift occurs when the force resulting from down shift pressure exceeds an opposing force including a force from governor pressure; and

means responsive to the value of governor pressure for preventing application of the forced down shift pressure signal to said larger area of the second valve member as demanded by positioning of the manual control valve until a predetermined transmission output speed is reached whereby down shift of the transmission is inhibited.