Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2001-05-17
2003-02-04
Lorence, Richard M. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S050000, C477S138000, C477S160000
Reexamination Certificate
active
06514175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for controlling an oil pressure of a transmission which is hydraulically activated to set a gear ratio properly.
2. Related Art
Oil pressures to be used in the transmission are one for activating valves and one for transmitting a torque. The latter oil pressure necessary for the torque transmission is demanded to have a considerably high level but may correspond to the torque to be transmitted. In the vehicular transmission having a hydraulically controlled transmission mounted thereon, therefore, the oil pressure to be generated is varied according to the torque so that it may not become excessively high to prevent the fuel economy from deteriorating.
For example, a continuously variable transmission is constructed to have continuously variable gear ratios such that transmission members such as belts or power rollers are continuously varied in their radial positions for frictional contacts by utilizing that the peripheral velocities of rotary members are different according to those radial positions. In the continuously variable transmission of this kind, the torque is transmitted by frictional forces so that the frictional forces may match the torque to be transmitted, by varying the oil pressure for generating the frictional forces according to the toque. More specifically, the oil pressure is controlled on the basis of engine loads, as represented by the opening of a throttle or the opening (or depression) of an accelerator (pedal).
One example will be described on a belt-type continuously variable transmission. In the transmission of this kind, the torque is transmitted through the frictional forces which are generated between driving and driven pulleys having variable groove widths and a belt made to run on the pulleys. For this torque transmission, therefore, the belt clamping force by the pulleys is controlled on the basis of a load (e.g. accelerator depression) of a prime mover such as the engine connected to an input side of the continuously variable transmission.
As the control for generating the belt clamping force with the oil pressure, there has been known the so-called “open loop control”, in which a target oil pressure and clamping force are obtained by outputting an instruction signal based on the load and by activating a control device such as a solenoid valve in response to that instruction signal. One example of the open loop control is disclosed in Japanese Patent Laid-Open No. 9-217800. This hydraulic control system is constructed such that the line pressure is modulated to the oil pressure of an instruction signal for a controller. In order to prevent the individual difference of the control part such as a solenoid from influencing the oil pressure, on the other hand, a detecting oil pressure is generated in response to an indication from the controller and is detected in terms of ON of a hydraulic switch disposed in a line pressure circuit, so that the correction of a working pressure may be learned and controlled on the basis of a signal coming from the hydraulic switch. Moreover, the detecting oil pressure is preferably generated under conditions for exerting no influence upon the actions of the transmission. These conditions are exemplified by the idling time, the N-range, the normal oil temperature or the vehicle stop.
The aforementioned hydraulic control system of the prior art can be made at a reasonable cost because the oil pressure sensor is replaced by a hydraulic switch, and can prevent the durability from being lost by the high oil pressure because the detecting oil pressure is temporarily generated at the idling time in the N-range or the like where the power is not transmitted to the continuously variable transmission. In that hydraulic control system of the prior art, however, one specific oil pressure is employed as the detecting oil pressure by using the hydraulic switch in place of the oil pressure sensor. This makes it probable that the learning correction cannot always be precisely made on the oil pressure over a wide practical range.
In an electrically activated hydraulic device such as a linear solenoid, on the other hand, there may be a difference between the characteristics in the pressure rising process and the characteristics in the pressure falling process. With a large characteristic difference or hysteresis, the oil pressure cannot be precisely controlled. Moreover, the hydraulic control system of the prior art is constructed to detect one specific oil pressure with the switch. This construction makes it disadvantageously impossible to detect the width of the hysteresis.
SUMMARY OF THE INVENTION
An object of the invention is to provide a hydraulic control system capable of learning and correcting properly the instruction value of an oil pressure to be used in the transmission.
Another object of the invention is to provide a control system capable of learning and correcting the oil pressure without affecting the active state of the transmission adversely.
A first feature of the invention resides in that the rotating speed of a prime mover connected to a hydraulic pump is raised with the transmission being stopped, in that instruction signals for generating a plurality of oil pressures is outputted in the stop state, in that the oil pressures corresponding to the individual instruction signals, and in that the instruction value of the oil pressure is learned and controlled on the basis of the detection result. On the other hand, a second feature of the invention resides in that the instruction signals for generating the plurality of oil pressures are outputted, in that the oil pressures corresponding to the individual instruction signals are detected, and in that the instruction values of the oil pressures are learned and controlled on the basis of the detection results.
According to the invention, more specifically, there is provided a hydraulic control system for generating an oil pressure by turning a prime mover connected to a hydraulic pump and for outputting an oil pressure instruction signal to an electrically activated pressure modulating mechanism, to modulate the oil pressure generated in the hydraulic pump to an oil pressure according to the instruction signal and to feed the modulated oil pressure to a transmission. The hydraulic control system executes controls of: raising the rotating speed of the prime mover while the transmission is not rotated by the prime mover, to increase the output volume of the hydraulic pump; oil pressure instructing for outputting a plurality of instruction signals of different pressure instruction values to the pressure modulating mechanism while the output volume of the hydraulic pump is increased, to output oil pressures at a plurality of pressure levels; detecting the oil pressure to be modulated and fed to the transmission, at a plurality of pressure levels; and learning and correcting the instruction signals on the basis of the pressure instruction value outputted by the oil pressure instructing control and the oil pressure detected by the oil pressure detecting control.
In the invention, therefore, the output pressure of the hydraulic pump is raised by increasing the rotating speed of the prime mover while the transmission is not rotated by the prime mover. Even with the transmission being stopped, therefore, the oil pressure to be generated by the hydraulic pump or the oil pressure source can be to a pressure at the highest level in the acting state of the transmission. In addition, the signals at the plurality of pressure instruction values are outputted. Without any manipulation to activate the transmission with applying the high pressure to the transmission, therefore, it is possible to generate and detect the oil pressure in the practical state of the transmission and to make the learning correction of the oil pressure.
On the other hand, the hydraulic control system of the invention execute controls of oil pressure instructing for outputting an instruction signal at a predetermin
Habuchi Ryoji
Hattori Yuji
Kondo Hiroki
Kono Katsumi
Matsuo Kenji
Ho Ha
Lorence Richard M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toyota Jidosha & Kabushiki Kaisha
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