Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Reexamination Certificate
1998-12-31
2001-11-27
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
C361S154000, C361S160000
Reexamination Certificate
active
06324045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to control transmissions with hydraulic and mechanical gearing, especially transmissions which are used in commercial utility vehicles.
2. Description of the Related Art
All gear shofts should be smooth under load, regardless of the type of engine or differential transmissions that are being applied. These requirement for a transmission control unit are best addressed with an electrohydraulic conyrol system, whose operating principle, for example, is described in the technical publication “Hydrodynamik in der Antriebstechnik”, published by J. M. Voith GmbH, Vereinte Fachverlage Krauskopf-Ingenieur Digest, Mainz, 1987.
The electronics and hydraulics of the above-mentioned electrohydraulic control systems are joined together via solenoid valves including a magnetizing coil, a piston valve and a pull-back spring. Until now, the control of the solenoid valves has been accomplished by continuous controllers which were either hardware-based or software-based. A significant simplification in the control of automatic transmissions, as compared to the continuous controllers, was achieved by the application of two-step controllers (ref. Dubbel, reference book for mechanical engineering, Springer Verlag, Berlin, Heidelberg, N.Y., 1995, Pages X8 through X9). According to the state of the art, these controllers were built using hardware circuitry whereby, the comparators, for example, were applied in the form of connected operational amplifiers. The hardware-based circuitry was designed as application-specific integrated circuitry (ASIC). The setting of the hysteresis, which is required for the stable operation of a two-step controller (ref. Dubbel, rest as stated above, page X8), was accomplished by applying resistors into the circuit design. In a very time-consuming balancing process, these resistors had to be adjusted for every transmission control system as part of a post-manufacturing process. This required among other things, for example, the checking of the entire control system and a manual soldering of balance resistors into the circuitry.
Further, the hardware circuitry assigns a discrete manipulated output for every actual input value. This rigid relationship did not permit the control of two solenoid valves with one and the same controller.
SUMMARY OF THE INVENTION
The present invention provides a digital two-step controller and a digital two-step control process, which surmounts the above-mentioned disadvantages associated with the state of the art. The application of the two-step controller avoids the manual balancing process, which has thus far been a necessity. Furthermore, the present invention provides the capability of controlling several valves with one and the same arrangement.
In accordance with the present invention, the chosen gear befits the vehicle speed and engine load so that optimum engine operating conditions and driveability characteristics can be achieved all times, even under varying driving conditions. The digital two-step controller is designed by comparing the digital actual value stored in memory to a set point value, which is also stored in memory. This comparative assessment is the starting point for the subsequent steps. In one embodiment, the digital actual value is subtracted from the digital set point value and, depending on the algebraic sign of this difference, the process progresses to the next steps. In another embodiment, a digital hysteresis value, which is characteristic for this controller, is added to the set point value, which forms the basis for the hysteresis adjustment of the two-step controller.
It is seen as an advantage for the sampling time to be in the area of 0.1 to 10 milliseconds. It is especially advantageous to work with a sampling period of one millisecond. A sampling period of one millisecond makes it possible for the digital two-step controller to control the actuator sufficiently fast. At very low measured signal strengths, an amplifying circuit can be used to process this analog signal. In another embodiment, the actuator is replaced by a magnetizing coil of a solenoid valve, which is controlled by the digital two-step controller as described in this invention. Thus, the two-step controller, as an embodiment of this invention, can be applied to control an electrohydraulic transmission unit through the use of solenoid valves. This transmission unit is preferably a torque divider transmission.
In addition to the above-mentioned digital two-step control devices, this invention also provides several processes for the two-step control of an actuator element.
The first invention-related process deals with a two-step control logic in which a digital actual value is compared to a digital set point value. In a second design variation, a difference between the digital actual value and the set point value is determined, and the control is performed with the use of this differential signal. In a third design variation, a possible hysteresis of the two-step controller is considered.
The invention is described in more detail below by use of design examples and graphical representations.
REFERENCES:
patent: 4665348 (1987-05-01), Stupak, Jr.
patent: 4770178 (1988-09-01), Sausner et al.
patent: 4855913 (1989-08-01), Brekkestran et al.
patent: 5251091 (1993-10-01), Ito et al.
patent: 5461563 (1995-10-01), Mimura et al.
patent: 5933313 (1999-08-01), Furukawa
patent: 32 25 254 A1 (1984-01-01), None
patent: 40 12 577 C1 (1991-04-01), None
Ref.. Dubbel, reference book for mechanical engineering, Springer Verlag, Berlin, Heidelberg, New York, 1955, pp. X8 through X9. (No Month).
English abstract of Japanese patent document No. 07091530, Apr. 4, 1995.
“Hydrodynamik in der Antriebstechnik” published by J.M. Voith GmbH, Vereinte Fachverlage Krauskopf-Ingenieur Digest, Mainz, 1987. (No Month).
Bek Manfred
Dietzel Bernd
Sherry Michael J.
Taylor & Aust P.C.
Voith Turbo GmbH & Co. KG
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