Patent Application
20080096719
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring initially to
The primary pulley 11 is an input shaft pulley on the input shaft side for inputting rotation from the engine 1 into the continuously variable transmission 10. The primary pulley 11 includes a movable conical sheave 11a and a stationary or fixed conical sheave 11b. The movable conical sheave 11a is disposed opposite the fixed conical sheave 11b to form a V-shaped pulley groove. The movable conical sheave 11a is displaceable in an axial direction by hydraulic fluid pressure operating toward a primary pulley cylinder chamber 11c. The fixed conical sheave 11b rotates integrally with an input shaft 11d. The primary pulley 11 is connected to the engine 1 via the forward/reverse switching mechanism 3 and the torque converter 2. The torque converter 2 preferably comprising a lock-up clutch. The primary pulley 11 transmits the rotation of the engine 1 to the secondary pulley 12 by the drive belt 13. The rate at which the primary pulley 11 rotates is detected by a primary pulley rotation rate sensor 26.
The drive belt 13 wraps around the primary pulley 11 and the secondary pulley 12, and transmits the rotation of the primary pulley 11 to the secondary pulley 12. The secondary pulley 12 outputs the rotation transmitted via the drive belt 13 to the differential 4. The secondary pulley 12 basically includes a movable conical sheave 12a and a stationary or fixed conical sheave 12b. The moveable conical sheave 12a is disposed opposite the fixed conical sheave 12b to form a V-shaped pulley groove. The moveable conical sheave 12a is displaceable in an axial direction in accordance with the hydraulic fluid pressure operating toward a secondary pulley cylinder chamber 12c. The conical sheave 12b rotates integrally with an output shaft 12d. The pressure-receiving surface area of the secondary pulley cylinder chamber 12c is set to be substantially equivalent to that of the primary pulley cylinder chamber 11c.
The secondary pulley 12 is connected to the differential 4 via idler gears 14. The secondary pulley 12 outputs rotation to the differential 4. The rate at which the secondary pulley 12 rotates is detected by a secondary pulley rotation rate sensor 27. The vehicle speed can be calculated from the rotation rate of the secondary pulley 12.
The CVT-CU 20 determines the contact frictional force and the transmission gear ratio (the value obtained from dividing the effective radius of the secondary pulley 12 by the effective radius of the primary pulley 11), and then transmits a command to the hydraulic control unit 30 for controlling the continuously variable transmission 10. The CVT-CU 20 performs these actions based on the signals from an inhibitor switch 23, an accelerator pedal stroke sensor 24, a fluid temperature sensor 25, the primary pulley rotation rate sensor 26, the secondary pulley rotation rate sensor 27, and other sources, as well as input torque information from an engine control unit 21.
The hydraulic control unit 30 is actuated according to the command from the CVT-CU 20. The hydraulic control unit 30 controls the hydraulic fluid pressure supplied to the primary pulley 11 and the secondary pulley 12, and moves the moveable conical sheave 11 a and the moveable conical sheave 12a the direction of the rotational axis.
The width of the pulley groove changes when the movable conical sheave 11a and the movable conical sheave 12a move. The V-belt 13 then moves on the primary pulley 11 and secondary pulley 12. As a result, the contact radius of the V-belt 13 changes with respect to the primary pulley 11 and the secondary pulley 12, and the transmission gear ratio and the contact frictional force of the V belt 13 are controlled.
The rotation of the engine 1 is delivered to the belt-type continuously variable transmission 10 via the torque converter 2 and the forward/reverse switching mechanism 3. Thus, the rotation of the engine 1 is transmitted from the primary pulley 11 to the differential 4 via the V-belt 13 and the secondary pulley 12.
When an acceleration pedal 24 is depressed, or gears are shifted in manual mode, the movable conical sheave 11a of the primary pulley 11 and the movable conical sheave 12a of the secondary pulley 12 are displaced along the axial direction, and the radius of contact with respect to the V-belt 13 is changed, whereby the transmission gear ratio is continuously changed.
A pressure regulator valve 40 (line pressure regulating component) drains some of the discharge pressure supplied from a hydraulic fluid pump 42 to a fluid channel 43 via a fluid channel 41, and thereby regulates the hydraulic fluid pressure within the fluid channel 41 as a line pressure in response to commands from by the hydraulic control unit 30. A fluid channel 44 that branches off from the fluid channel 41 supplies the line pressure to a gear changing control valve 45, a secondary valve 46, and a pilot valve 47. The hydraulic fluid pressure drained from the pressure regulator valve 40 is supplied to a clutch regulator valve 48 via the fluid channel 43.
The clutch regulator valve 48 drains some of the hydraulic fluid pressure drained from the pressure regulator valve 40, and thereby regulates the hydraulic fluid pressure in the fluid channel 43 as clutch pressure. A fluid channel 49 that branches from the fluid channel 43 supplies the clutch pressure to a select switch valve 50.
The pilot valve 47 reduces the line pressure supplied via the fluid channel 44 to a fixed pressure corresponding to the set weight load of a spring, and regulates the pressure as pilot pressure. The pilot pressure is supplied to a secondary solenoid 52 and a select switch solenoid 53 via a fluid channel 51.
In the secondary solenoid 52, the fluid channel 51 is connected to an input port of the secondary solenoid 52 for supplying the pilot pressure and a fluid channel 55 in communication with a secondary control valve 54 is connected to an output port of the secondary solenoid 52. The secondary solenoid 52 constitutes a signal pressure regulating component that regulates the pilot pressure according to a current supplied thereto, and supplies the pilot pressure as signal pressure to the secondary control valve 54. The secondary valve 46 and secondary control valve 54 constitutes a secondary pressure regulating component.
The secondary solenoid 52 is a linear solenoid that can adjust the aperture of a solenoid valve 52a based on a command signal from the hydraulic control unit 30. As shown in
In the select switch solenoid 53, the fluid channel 51, which supplies the pilot pressure, is connected to an input port of the select switch solenoid 53, and a fluid channel 56, which communicates with the select switch valve 50, is connected to an output port of the select switch solenoid 53. The select switch solenoid 53 is switched ON or OFF according to a current supplied to its solenoid based on a command signal from the hydraulic control unit 30. In the ON state, the pilot pressure is supplied as signal pressure to the select switch valve 50.
In the secondary control valve 54, the fluid channel 49 is connected to an input port of the secondary control valve 54, and a fluid channel 57, which communicates with the secondary valve 46, is connected to an output port of the secondary control valve 54. The secondary control valve 54 regulates the clutch pressure as the signal pressure of the secondary valve 46 according to the signal pressure supplied from the secondary solenoid 52 via the fluid channel 57, and supplies the resulting pressure to the secondary valve 46.
In the secondary valve 46, the fluid channel 44 is connected to an input port of the secondary valve 46, and a fluid channel 58, which communicates with the secondary pulley cylinder 12c, is connected to an output port of the secondary valve 46. The secondary valve 46 reduces the line pressure according to the signal pressure supplied from the secondary control valve 54 via the fluid channel 57, and supplies the line pressure to the secondary pulley cylinder 12c.
In the gear change control valve 45, the fluid channel 44 is connected to an input port of the gear change control valve 45, and a fluid channel 59, which communicates with the primary pulley cylinder chamber 11c, is connected to an output port of the gear change control valve 45. The gear change control valve 45 reduces the line pressure according to the operation of a servo link 60 that constitutes a mechanical feedback mechanism, and supplies the line pressure to the primary pulley cylinder chamber 11c. The gear change control valve 45 is driven by a stepper motor 61 that is connected to one end of the servo link 60 and is provided with feedback in regard to the groove width, i.e., the actual transmission gear ratio, from the movable conical sheave 11a of the primary pulley that is connected to the other end. The stepper motor 61 is controlled based on a command signal from the hydraulic control unit 30.
In the select switch valve 50, the fluid channel 49 is connected to an input port; and a fluid channel 63, which communicates with a manual valve 62, is connected to an output port. The select switch valve 50 switches the connecting fluid channel, with the output pressure of the select switch solenoid 53 supplied via the fluid channel 56 being used as the signal pressure.
When the select switch solenoid 53 is ON, a spool valve 64 of the select switch valve 50 slides upward in the drawing, against the urging force of a spring 65. The clutch pressure supplied from the fluid channel 49, after being passed through a fluid channel 66 that branches off from the fluid channel 49 and regulated by a select control valve 67, is accordingly supplied to a forward clutch 69 via the select switch valve 50, the fluid channel 63, the manual valve 62, and a fluid channel 68.
When the select switch solenoid 53 is OFF, the spool valve 64 of the select switch valve 50 slides downward in the drawing via the urging force of the spring 65. The clutch pressure supplied from the fluid channel 49 is accordingly supplied to the forward clutch 69 via the select switch valve 50, the fluid channel 63, the manual valve 62, and a fluid channel 68. The forward clutch 69 engages, and is thereby able to transmit the driving force of the engine 1 to the variable transmission 10. The forward clutch 69 is configured so that the transmittable torque increases as the pressure supplied to the forward clutch 69 increases.
The control performed by the hydraulic CVT controller (the CVT-CU 20 and the hydraulic control unit 30) is described below with reference being made to the flowchart of
In step S1, a decision by the CVT-CU 20 is made as to whether or not the shift position is within the N range. If the shift position is in the N range, then the process proceeds to step S2. If the shift position is outside of the N range, then the process returns to step S1.
In step S2, the secondary pressure is indicated as being the maximum (MAX) pressure. As a result, the solenoid valve 52a of the secondary solenoid 52 is completely closed by the hydraulic control unit 30, and the amount of the hydraulic fluid pressure being drain becomes zero. The signal pressure accordingly reaches its maximum, and the secondary pressure becomes the MAX pressure.
In step S3, a decision by the CVT-CU 20 is made as to whether or not the shift position is within the D range. If the shift position is in the D range, then the process proceeds to step S4. If the shift position is outside of the D range, then the process returns to step S3.
In step S4, a decision by the CVT-CU 20 is made as to whether or not precharging has concluded. With precharging, when the shift position is switched from the N range to the D range and the forward clutch 69 is engaged, the pressure supplied to the forward clutch 69 is reduced to an initial forward clutch engagement pressure after the supply pressure has been maintained in a state of maximum pressure for a prescribed period of time. Precharging is performed in order to quickly move the forward clutch to the initial engaging state.
In step S5, the indication that the secondary pressure is MAX pressure is terminated. The aperture of the solenoid valve 52a of the secondary solenoid 52 is accordingly controlled by the hydraulic control unit 30 so that a desired secondary pressure is reached.
In the present embodiment, as described above, the signal pressure is regulated so that the pressure supplied to the secondary pulley 12 is at a maximum from the time the shift position is within the N range to the time the position changes into the D range and precharging concludes. Therefore, the solenoid valve 52a closes completely, and the amount in which the hydraulic fluid is drained is zero. As a result, the amount of wasted fluid decreases, and the balance in the fluid supplied through the overall hydraulic circuit improves. The hydraulic fluid pressure supplied to the forward clutch 69 can be maintained even during periods of idling, when the rate of engine rotation is low. It is also possible to prevent any jerkiness when the vehicle starts to move as caused by delayed clutch engagement, and also to prevent shock from occurring as a result of sudden engaging of the clutch thereafter.
In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. The term “detect” as used herein to describe an operation or function carried out by a component, a section, a device or the like includes a component, a section, a device or the like that does not require physical detection, but rather includes determining, measuring, modeling, predicting or computing or the like to carry out the operation or function. The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-288546 | Oct 2006 | JP | national |
