Speed ratio control system for continuously variable transmission

• US 6,368,247 B1
• Filed: 04/27/2000
• Issued: 04/09/2002
• Est. Priority Date: 04/28/1999
• Status: Expired due to Term

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabusiki Kasha
• Inventors: Kondo, Kaoru
• Primary Examiner(s): Marmor, Charles A
• Assistant Examiner(s): HO, HA DINH
• Application Number:
  US09/559,342
• Time in Patent Office: 712 Days
• Field of Search: 477/47, 477/44, 477/37, 477/118, 477/120, 477/115
• US Class Current: 477/47
• CPC Class Codes: F16H 2061/6612 for engine braking
• CPC Class Codes: F16H 59/66 Road conditions, e.g. slope, slippery
• CPC Class Codes: F16H 61/21 Providing engine brake control
• CPC Class Codes: F16H 61/66254 controlling of shifting being influenced by a signal derived from the engine and the main coupling

Abstract

A continuously variable transmission that can provide a sufficient engine braking during a downhill running time with neither complicating the control nor inviting an increase in the program capacity is established. In a gear ratio control system 60 for gear ratios in the continuously variable transmission coupled to an engine, setting means 51 to 55 set a target speed of an input unit 21 of the continuously variable transmission during the downhill running time on the basis of a target output of the engine. Control means 56 controls the gear ratios of the continuously variable transmission so that the real speed of the input unit 21 may become the target speed of the input unit 21.

Claims

1. A speed ratio control system for controlling speed ratios of a continuously variable transmission coupled to an engine, comprising:

a setting element for setting a target speed of an input unit of the continuously variable transmission at a downhill running time on the basis of a target output of said engine; and

a control element for controlling the speed ratios of the continuously variable transmission such that an actual speed of said input unit becomes the target speed of said input unit,

wherein said setting element includes,

a decision element for determining whether or not learning conditions are satisfied with a fully closed throttle,

an updating element for updating a learning reference torque when said decision element determines that the learning conditions are satisfied, on the basis of one of a reference torque and the engine torque corresponding to an actual engine output, and a learning reference torque set at the preceding time of satisfying the learning conditions, and

a determining element for determining engine output characteristics on the basis of the learning reference torque updated by said updating element.

2. gear ratio control system for a continuously variable transmission according to claim 1,

wherein said setting element includes,

a target acceleration setting element for setting a target acceleration according to a road slope,

a target output setting element for setting a target output of the engine in accordance with said target acceleration, and

a target speed setting element for setting the target speed of the input unit of said continuously variable transmission in accordance with said target output.

3. A speed ratio control system for controlling speed ratios of a continuously variable transmission coupled to an engine, comprising:

a setting element for setting a target speed of an input unit of the continuously variable transmission at a downhill running time on the basis of a target output of said engine; and

a control element for controlling the speed ratios of the continuously variable transmission such that an actual speed of said input unit becomes the target speed of said input unit,

wherein said setting element includes,

a target acceleration setting element for setting a target acceleration according to a road slope such that an actual acceleration becomes said target acceleration,

a properness deciding element for determining excess/deficiency of an engine braking, and

a learning correcting element for learning and correcting said target acceleration on the basis of the determination of said properness deciding element.

4. A speed ratio control method for controlling speed ratios of a continuously variable transmission coupled to an engine, comprising:

setting a target speed of an input unit of said continuously variable transmission at a downhill running time on the basis of a target output of said engine; and

controlling the gear ratios of said continuously variable transmission such that an actual speed of said input unit becomes the target speed of said input unit,

wherein the step of setting the target speed of said input unit includes,

determining whether or not learning conditions are satisfied with a fully closed throttle,

updating a learning reference torque when it is determined in said determining step that the learning conditions are satisfied, on the basis of one of a reference torque and the engine torque corresponding to an actual engine output, and a preceding learning reference torque set at the preceding time of satisfying the learning conditions, and

determining engine output characteristics on the basis of the learning reference torque updated in said updating step.

5. The speed ratio control method for a continuously variable transmission according to claim 4,

wherein the step of setting the target speed of said input unit includes,

setting a target acceleration according to a road slope,

setting a target output of the engine in accordance with said target acceleration, and

setting said target speed of the input unit of said continuously variable transmission in accordance with said target output.

6. A speed ratio control method for controlling speed ratios of a continuously variable transmission coupled to an engine, comprising:

setting a target speed of an input unit of said continuously variable transmission at a downhill running time on the basis of a target output of said engine; and

controlling the gear ratios of said continuously variable transmission such that an actual speed of said input unit becomes the target speed of said input unit,

wherein the step of setting the target speed of said input unit includes,

setting a target acceleration according to a road slope,

setting said target speed such that an actual acceleration becomes said target acceleration,

determining excess/deficiency of an engine braking, and

learning and correcting said target acceleration on the basis of the decision in said deciding step.