Hydraulic control apparatus for vehicle power transmitting system having continuously variable transmission

• US 5,006,093 A
• Filed: 02/07/1990
• Issued: 04/09/1991
• Est. Priority Date: 02/13/1989
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Habuchi, Ryoji, Itoh, Hiroshi, Soga, Yoshinobu, Sugaya, Masami, Hattori, Yuji, Morisawa, Kunio, Kouno, Katsumi
• Primary Examiner(s): Bui, Thuy M.
• Application Number:
  US07/476,601
• Time in Patent Office: 426 Days
• Field of Search: 474/18, 474/28, 474/69, 474/70, 74/866-868
• US Class Current: 474/28
• CPC Class Codes: F16H 61/66259 using electrical or electronical sensing or control means

Abstract

A hydraulic control apparatus for a vehicle power transmitting system having a continuously variable transmission having a first and a second shaft, a pair of variable-diameter pulleys provided on the shafts, a belt connecting the pulleys, and two hydraulic actuators for changing diameters of the pulleys. The apparatus includes a directional control valve for supplying a fluid from a pressure line to one of the two actuators while discharging the fluid from the other actuator, a first fluid passage connected to the directional control valve, for primarily supplying the fluid from the pressure line to a driving side actuator of the two actuators which is provided on a driving one of the first and second shafts, a second fluid passage connected to the directional control valve, for primarily supplying the fluid from the pressure line to a driven side actuator of the hydraulic actuators, and a flow restrictor for restricting a flow of the fluid through the first fluid passage so that a fluid flow resistance of the first fluid passage is higher than a fluid flow resistance of the second fluid passage.

Claims

1. A hydraulic control apparatus for a power transmitting system for an automotive vehicle having a continuously variable transmission which has a first and a second shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a belt connecting the pulleys, and a pair of hydraulic actuators for changing effective diameters of the pulleys, the apparatus including a directional control valve for supplying a working fluid from a pressure line to one of said pair of hydraulic actuators while discharging the working fluid from the other hydraulic actuator, for controlling a speed ratio of the transmission, wherein the improvement comprises:

a first fluid passage connected to said directional control valve, for primarily supplying said working fluid from said pressure line to a driving side actuator of said pair of hydraulic actuators which is provided on a driving one of said first and second shafts;

a second fluid passage connected to said directional control valve, for primarily supplying the working fluid from said pressure line to a driven side actuator of said pair of hydraulic actuators; and

flow restrictor means for restricting a flow of the fluid through said first fluid passage so that a fluid flow resistance of said first fluid passage is higher than a fluid flow resistance of said second fluid passage.

2. A hydraulic control apparatus according to claim 1, wherein said directional control valve is a two-position valve having a first and a second position, said apparatus further comprising:

a two-position flow control valve disposed between said directional control valve and said pair of hydraulic actuators, and cooperated with said directional control valve to control said speed ratio of said transmission such that said directional control valve is operated selectively to one of said first and second positions while a duty cycle of said flow control valve is controlled;

a first pressure line as said pressure line for applying a first line pressure to said one of said pair of hydraulic actuators;

a second pressure line for applying a second line pressure lower than said first line pressure, to said other hydraulic actuator;

a by-pass line connecting said second pressure line and an actuator of said pair of hydraulic actuators which is provided on one of said first and second shafts which is located nearer to drive wheels of the vehicle;

a one-way valve disposed in said by-pass line, for permitting a flow of the fluid therethrough in a direction from said second pressure line toward said actuator provided on the shaft nearer to said drive wheels; and

a flow restrictor disposed in said by-pass line, in parallel with said one-way valve.

3. A hydraulic control apparatus according to claim 1, wherein said directional control valve is a two-position valve having a first and a second position for increasing and reducing the speed ratio of the transmission, respectively, said apparatus further comprising:

a first solenoid coil for operating said directional control valve selectively to said first and second positions;

a two-position flow control valve disposed between said directional control valve and said driving and driven side actuators, and having a first and a second position for changing the speed ratio of the transmission at respective two different rates;

a second solenoid coil for operating said flow control valve selectively to said first and second positions; and

means for applying a first line pressure and a second line pressure lower than said first line pressure to said one and other hydraulic actuators, respectively, said speed ratio of the transmission being increased or reduced with said first and second line pressures applied to said one and other hydraulic actuators, respectively, depending upon a selected one of said first and second positions of said directional control valve, at one of said two rates depending upon a selected one of said first and second positions of said flow control valve,

said directional control valve having a drain port, a first line pressure port receiving said first line pressure, a second line pressure port receiving said second line pressure, four ports respectively connected to a first, a second, a third and a fourth connecting line, a spool having four lands for connecting said drain port and said first connecting line and connecting said first line pressure port and said third connecting line when said first solenoid coil is placed in one of energized and deenergized states thereof, and for connecting said first line pressure port and said second connecting line and connecting said second line pressure port and said fourth connecting line when said first solenoid coil is placed in the other of said energized and deenergized states,

said flow control valve having a port communicating with said driving side actuator, a port communicating with a driven side actuator of said pair of hydraulic actuators which is provided on a driven one of said first and second shafts, four ports respectively connected to said first, second, third and fourth connecting lines, and a spool having three lands, for connecting said first connecting line and said driving side actuator and connecting said third connecting line and said driven side actuator when said second solenoid coil is placed in one of energized and deenergized states thereof, and for connecting said second connecting line and said driving side actuator and connecting said fourth connecting line and said driven side actuator when said second solenoid coil is placed in the other of said energized and deenergized states.

4. A hydraulic control apparatus according to claim 1, further comprising:

a two-position flow control valve for regulating a rate of flow of the fluid therethrough, having an open and a closed position for respectively selecting a first rapid and a second slow shifting mode in which the speed ratio of the transmission is rapidly and slowly changed, respectively, a duty cycle of said flow control valve being controlled so as to provide a third medium-speed shifting mode in which the speed ratio is changed at a rate intermediate between rates of change in said first and second shifting modes, the speed ratio of the transmission being controlled in a selected one of at least two of said first, second and third shifting modes, so that a control error of said speed ratio is zeroed;

means for determining said control error;

means for determining a duty cycle at which said flow control valve is operated so as to zero the detected control error and

means for determining at least one boundary duty cycle value each substantially corresponding to a boundary between a controllable range and a non-controllable range of the rate of flow of the fluid through said flow control valve, said rate of flow of the fluid effectively varying with the duty cycle of the flow control valve over said controllable range, and not effectively varying with the duty cycle within said non-controllable range; and

mode selecting means for selecting said one of at least two of said first, second and third shifting modes, by comparing the determined duty cycle with said at least one boundary duty cycle value.

5. A hydraulic control apparatus for a power transmitting system for an automotive vehicle having a continuously variable transmission which has an input and an output shaft, a pair of variable-diameter pulleys provided on the input and output shafts, respectively, a belt connecting the pulleys, and a first and a second hydraulic actuator which are respectively provided on said input and output shafts, for changing effective diameters of the pulleys, said apparatus including a two-position directional control valve having a first and a second position, for applying a first line pressure from a first pressure line to one of said first and second hydraulic actuators while applying a second line pressure from a second pressure line to the other of said hydraulic actuators, and a two-position flow control valve disposed between said directional control valve and said hydraulic actuators and whose duty cycle is controlled so as to control a rate of flow of a working fluid therethrough, whereby a speed ratio of said transmission is changed at a controlled rate, wherein the improvement comprises:

a by-pass line connecting said second pressure line to said second hydraulic actuator;

a one-way valve disposed in said by-pass line, for permitting a flow of the fluid therethrough in a direction from said second pressure line toward said second hydraulic actuator; and

a flow restrictor disposed in said by-pass line, in parallel with said one-way valve.

6. A hydraulic control apparatus for a power transmitting system for an automotive vehicle having a continuously variable transmission which has a first and a second shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a belt connecting the pulleys, and a pair of hydraulic actuators for changing effective diameters of the pulleys, said apparatus including means for applying a first line pressure and a second line pressure lower than said first line pressure to one and the other of said pair of hydraulic actuators, respectively, so as to control a speed ratio of said transmission, wherein the improvement comprises:

a two-position directional control valve having a first and a second position for increasing and reducing the speed ratio of the transmission, respectively;

a first solenoid coil for operating said directional control valve selectively to said first and second positions;

a two-position flow control valve disposed between said directional control valve and said pair of hydraulic actuators, and having a first and a second position for changing the speed ratio of the transmission at respective two different rates; and

a second solenoid coil for operating said flow control valve selectively to said first and second positions,

said directional control valve having a drain port, a first line pressure port receiving said first line pressure, a second line pressure port receiving said second line pressure, four ports respectively connected to a first, a second, a third and a fourth connecting line, a spool having four lands for connecting said drain port and said first connecting line and connecting said first line pressure port and said third connecting line when said first solenoid coil is placed in one of energized and deenergized states thereof, and for connecting said first line pressure port and said second connecting line and connecting said second line pressure port and said fourth connecting line when said first solenoid coil is placed in the other of said energized and deenergized states,

said flow control valve having a port communicating with said driving side actuator, a port communicating with a driven side actuator of said pair of hydraulic actuator which is provided on a driven one of said first and second shafts, four ports respectively connected to said first, second, third and fourth connecting lines, and a spool having three lands, for connecting said first connecting line and said driving side actuator and connecting said third connecting line and said driven side actuator when said second solenoid coil is placed in one of energized and deenergized states thereof, and for connecting said second connecting line and said driving side actuator and connecting said fourth connecting line and said driven side actuator when said second solenoid coil is placed in the other of said energized and deenergized states.

7. A hydraulic control apparatus for a power transmitting system for an automotive vehicle having a continuously variable transmission, hydraulic actuator means for controlling a speed ratio of the transmission, and a two-position flow control valve connected to said hydraulic actuator means, for regulating a rate of flow of a working fluid therethrough so as to control a rate of change in said speed ratio, said flow control valve having an open and a closed position for respectively selecting a first rapid and a second slow shifting mode in which the speed ratio of the transmission is rapidly and slowly changed, respectively, a duty cycle of said flow control valve being controlled so as to provide a third medium-speed shifting mode in which the speed ratio is changed at a continuously variable rate intermediate between rates of change in said first and second shifting modes, the speed ratio of the transmission being controlled in a selected one of at least two of said first, second and third shifting modes, so that a control error associated with said speed ratio is zeroed, wherein the improvement comprises:

means for determining said control error;

means for determining a duty cycle at which said flow control valve is operated so as to zero the detected control error;

means for determining at least one boundary duty cycle value each substantially corresponding to a boundary between a controllable range and a non-controllable range of the rate of flow of the fluid through said flow control valve, said rate of flow of the fluid effectively varying with the duty cycle of the flow control valve over said controllable range, and not effectively varying with the duty cycle within said non-controllable range; and

mode selecting means for selecting said one of at least two of said first, second and third shifting modes, by comparing the determined duty cycle with said at least one boundary duty cycle value.