Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-05-24
2002-04-23
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C091S433000
Reexamination Certificate
active
06374856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve device, especially a proportional valve and/or a directional control valve.
2. Description of the Related Art
Proportional valves, also referred to as directional control valves, are known in numerous design variations and applied in various applications. Directional control valves are valves whose valve pistons, also referred to as control plungers, can be moved to various fixed shift positions allowing different hydraulic connections to be established for the purpose of controlling operating fluids. As a result, a directional change in fluid flow can be achieved. These valves are characterized by their nominal width, their nominal pressure and their possible distribution options. The main module of a directional control valve is the control unit which houses the valve piston inside the valve body or the control housing, thus bringing about the directional change in the fluid flow. There is an actuator attached to at least one of the two end-faces of the valve piston for the purpose of developing the activation force needed to move the valve piston. A frequently applied design variation is the so-called spool valve whereby the valve closing is initiated by the overlap as a result of the relative movements of the individual valve components, especially the valve piston inside the valve body. Depending upon the design and type of movement, these valves are grouped into rotary spool valves, longitudinal spool valves or a combination of both. The appropriate classification of the control units or valve units is determined by the number of connections or number of possible hydraulic lines that are attached, and by the number of possible shift positions. The control edges of the valve piston and the valve body have an especially significant effect on the precision of the shift events. They impact the throttling of the flow area and, hence, the speed of the consumer, usually a machine. Through appropriate shaping of these control edges in concert with the relative motion of the valve piston with respect to the valve body, different flow characteristics can be achieved. Directional control valves offer a certain number of shift positions.
Proportional directional control valves are defined as continuously variable directional control valves, preferably controlled electrically, whose axial motion of the valve piston is directly controlled in a position control mode or in a force control mode, proportional to a set point value, by pressure sealed actuators. The actuators of electrical, continuously variable directional control valves are designed as control magnets (solenoids) which facilitate an axial movement of the valve piston proportional to an electrical set point value. The valve piston is continuously adjustable in any position within the two stop positions provided by the valve body. This has special advantages when controlling and regulating the speed of hydraulic consumers. Such valves, for example, are known from:
1) Sales literature by Mannesmann Rexrodt:
RD 29 586/09.89
RD 29 175/03.93; and
2) Sales literature by the Herion-Werke KG—Fluidtechnik Nr. 7502263,0503.92.
These types of proportional valves have the disadvantage that the activation force, which, for example, is generated electro-magnetically, hydraulically, mechanically, or through any other devices must be chosen so that the maximum desired pressure that occurs in the consumer downstream of the valve is capable of being maintained on a long-term basis. The size of the effective area exposed to the pressure is determined by this requirement. This, however, has the consequence that lower pressures must be controlled with appropriately lower activation forces. At desired lower pressures, more pressure variability is to be expected during the control process. An increase in the range of activation force usually causes the size of the actuator to increase. For example, if the actuator is designed in form of an electromagnet, a fundamental increase in the magnetic force causes an increase in the size of the magnetizing coil, which requires more room. Furthermore, the costs of the electrical conductors associated with the larger magnetizing coil are higher and the current consumption also increases. As a general rule, and in view of the applications that use these valves, there are limits to the size of the valve and the actuator. Thus, a precise regulation of the pressure in the consumer cannot always be realized.
SUMMARY OF THE INVENTION
The present invention provides a proportional-directional control valve without that the stated disadvantages. Especially, the pressure fluctuations at very low target pressure settings are minimized. The valve device is furthermore suitable for applications, for example, automatic transmissions, whose requirements dictate the need to control the relatively low pressures in the hydraulic clutch elements as precisely as possible, combined with the need of high (torque) transmission capability of the clutch elements while operating in the converter range.
Within a first pressure range or the proportional range (this range can also correspond to the total operating range, which is on the order of 1-5 bar), the valve device is capable of exerting control in proportion to an electric current at the highest level of precision and at the highest possible activation force, while fully taking advantage of the maximum allowable activation force. Additionally, the valve is capable of operating as a normal directional control valve in a second, elevated pressure range, ranging from 6 to 20 bar. Thus, it is capable of transmitting the full pressure independently from the available pressure level in the consumer. The valve device is able to provide precise and repeatable shift events with minimum side effects from hydraulically-induced binding moments and mechanical friction. While achieving these requirements, the design complexity and cost is kept to a minimum.
In addition to a valve body, which includes at least one supply channel and one return channel, the valve device also includes an axially-moveable valve piston residing inside the valve body. This valve piston includes control edges to open and block the connections of the cross-sectional areas of the supply and return channels, as well as an actuator for providing an activation force onto the valve piston. Devices are provided for the generation of a force, opposing the activation force, at least over a part of the total operating range of the valve device. This force is dependent upon the pressure in the return channel. Inside a pressure range, which determines a first part of the total operating range of the valve device (this first part can also correspond to the total operating range), the possible range in activation force is increased relative to the pressure range at the consumer, promoting a more sensitive modulation of the activation forces and the final pressure at the consumer. Thus, a given pressure range at the consumer or return channel requires a larger range in activation force as compared to a conventionally-designed proportional valve. This is achieved after the valve piston has reached a control position by reaching an equilibrium between the activation force and a pressure force. The pressure force imposes a load on a certain area as a function of the pressure in the consumer, directionally opposing the activation force.
An interior opening inside the valve piston extends all the way to the far end of the valve piston relative to the actuator. A plunger resides inside the interior opening, whereby the plunger and the valve piston are moveable relative to one another. A limit stop provides support for the plunger. A connecting hole is between the interior opening of the valve piston and the outer periphery of the valve piston. The mouth of the connecting hole at the outer periphery of the valve piston is arranged so that the connecting hole is in communication with the return channel while operating in the stated portion of
Michalsky Gerald A.
Taylor & Aust P.C.
Voith Turbo GmbH & Co. KG
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