Power plants – Pressure fluid source and motor – Coaxial impeller and turbine unit
Reexamination Certificate
1999-06-01
2002-03-19
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Coaxial impeller and turbine unit
C060S359000
Reexamination Certificate
active
06357229
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a hydrodynamic clutch and a method of operating a hydrodynamic clutch.
2. Description of the related art
Hydrodynamic clutches for transfer of torque are known from many descriptions, for example from the pamphlets
1.) CR 252; and
2.) J. M. Voith GmbH” “Hydrodynamic in drive technology; Vereinigte Fachverlage Krauskopf Ingenieur Digest; Mainz 1987. Hydrodynamic clutches for transfer of torque include at least two blade wheels arranged concentrically to each other. The two blade wheels include one primary blade wheel and a secondary blade wheel which, together, form at least one torus-shaped work chamber. The primary blade wheel acts as a pump impeller and the secondary blade wheel as a turbine wheel. The primary blade wheel is linkable with a drive shaft that can be coupled at least indirectly with a drive motor for torsional strength. The secondary blade wheel is linkable with a drive shaft that can be coupled at least indirectly for torsional strength with a machine that is to be driven. For the transfer of torque, the working chambers are to be filled with operating medium. The operating medium is circulated due to the primary blade wheel rotation during the operation of the clutch, and produces a reaction moment on the blading of the secondary blade wheel. This circulation of the operating medium between the primary and secondary blade wheels is also referred to as operating circulation. However, not the entire flow of energy is converted into reaction moment, only a part, while the remainder is converted into heat.
Cooling of the operating medium during operation of the clutch can be accomplished in various ways. Possible is a cooling circuit which is allocated to the operating circuit, and through which, during operation, a part of the operating medium would be continuously supplied. Through appropriate openings in the blade wheels and through nozzles, the heated operating medium could, for example, be admitted to a pump shell that is rotating at the speed of the primary blade wheel. There, the operating medium is received by a dynamic pressure tube which is positioned against the direction of rotation. In its fitting position, the dynamic pressure tube engages in the pump shell above the clutch shaft. Because of the pressure conditions, the flow energy of the operating medium which is accepted through the accumulation dynamic pressure tube is sufficient to return it again to the clutch, without additional help, through a cooling unit, a cooler or a heat exchanger. For this purpose, an enclosed coolant circuit is assigned to the operating circuit during operation. There is always a sufficient quantity of operating medium in the clutch and in the cooling circuit when stationary. No liquid is added to or removed from this circuit. By adding to or removing operating medium from the clutch, an increase or decrease of the motor speed is achieved. For this purpose, a supply line or channel and a discharge line or channel are assigned to the operating chambers for the purpose of filling and emptying. The supply and discharge lines are connected to an external operating medium supply source, such as an operating medium tank. The provision of the supply and discharge lines to the operating chambers can be arranged separately from the cooling circuit or by utilizing the lines or channels of the cooling circuits.
Other methods of exchanging or cooling the operating medium present in the operating chamber are possible. For example, the operating medium can be exchanged in the operating circuit by simultaneous removal of a certain volume of heated operating medium and by feeding of operating medium at lower temperature in the corresponding volume.
A significant problem with hydrodynamic clutches is that, depending on the application, and due to the rotation of the rotor parts of the clutch in a housing, the danger exists during start-up or activation of not filling the clutch to an exact level. Rather, the clutch can be overfilled, since an exact filling degree is very difficult to achieve. A deterioration of the efficiency level and an increasing leakage in the individual labyrinths, that is, the operating medium carrying lines, are apparent due to additional losses in the rotor parts themselves, such as the individual blade wheels, the housing and the rotor parts. A solution for the avoidance of these disadvantages, which would include an additional discharge line from the housing to the tank, is not desirable. In order to avoid overfilling, the supply line or the control unit for regulating the supply is triggered through a filling signal. The pressure in the discharge line, for example, may act as the filling signal. This pressure is measured by an acquisition sensor measuring the current pressure value in the discharge line from the operating chamber. The unit is locked electrically through a pressure switch when the unit exceeds a certain pressure so that supply of additional operating medium is prevented. However, the problem with such a method is that this signal is very inexact due to the varying marginal values. Also, this signal is often insufficient in order to prevent overfilling of the clutch. The pressure switch itself must always be adjusted very precisely during initial operation and, moreover, is subjected to the pressure peaks by the opened filling valve in the supply line. Specifically, a certain pressure value is continuously determined, with the device for measuring the pressure, during a time span between an empty condition of the clutch to a maximum filling of the clutch.
This pressure value steadily increases. A clear deviation in increase in a characteristic curve for the pressure, in dependence on the clutch filling, occurs only in the area of overfilling, that is at a clutch filling degree of greater than 100%. Each pressure value is therefore proportional to a certain filling degree. In order to determine a full status, a corresponding pressure value must therefore be measured. Tolerances may be included in these determinations. Consequently, only a small pressure area remains in which an overfill may be concluded. Within this limited pressure area, triggering of the pressure switch is necessary. Since the determined pressure value in the line can still be affected by a series of additional marginal factors, the acquired pressure value often does not correspond with the theoretically assigned filling degree. An early termination of filling at a filling degree of less than 100%, or overfilling, is then the result.
SUMMARY OF THE INVENTION
The present invention expands on a method of operating a hydrodynamic clutch so that the disadvantages of the current state of the art are avoided. Specifically, an effective protection against overfilling is realized which is suitable for different applications and offers quick response times. The method of the present invention distinguishes itself through low constructional and control engineering costs. The constructional design necessary in order to realize overfill protection is greatly non-susceptible to failure and is able to very quickly and precisely sense and respond to a maximum permissible filling degree. The maximum permissible filling degree can be consistent with the generally maximum permissible and freely definable filling degree.
According to the invention, a hydrodynamic clutch, including at least two blade wheels, one primary blade wheel and a secondary blade wheel, which together form at least one torus-shaped operating chamber, is operated so that only two filling degree conditions are recognized. One filling degree condition includes the condition of non-filling and partial filling, and a second filling degree condition describes the maximum permissible filling degree. An established first, very low first pressure value is assigned to the first filling degree condition. A greater pressure value is assigned to the second filling degree condition. The operating chamber is coupled with an accumulation chamber. The
Bregler Haymo
Schust Bernhard
Leslie Michael
Lopez F. Daniel
Taylor & Aust P.C.
Voith Turbo GmbH & Co. KG
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