Motors: expansible chamber type – With motive fluid valve – To provide unequal inlet and exhaust flow rates to single...
Reexamination Certificate
1999-02-23
2001-06-26
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
To provide unequal inlet and exhaust flow rates to single...
Reexamination Certificate
active
06250201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a throttle device for use in hydraulic adjustment devices in motor vehicles. More specifically, the present invention relates to a throttle device for a hydraulic adjustment device for actuating a motor vehicle clutch.
2. Description of the Related Art
A prior art blocking-protected hydraulic brake system for vehicles is disclosed by German reference DE 37 44 070 C2. This prior art system comprises a main brake cylinder, a pressure medium supply tank and at least one wheel brake, which is connected to the main brake cylinder via a brake line and to the pressure medium supply tank via a relief line. A pressure modulation valve is located in each of the aforementioned lines, so that the pressurization or pressure relief of the wheel brakes can be implemented depending on pressure control signals. A pump that conveys pressure medium from the pressure medium supply tank is attached to the brake line via a pressure line. FIG. 1 of this prior art reference shows that a throttle valve (12′ and 12″) is connected between the pump and the main brake cylinder in the brake line piece between the main brake cylinder and the opening of the pressure line into the brake line. FIG. 2 of the reference shows that the throttle valve has a first check valve 61 that blocks flow toward the main brake cylinder and a second check valve which blocks flow in the opposing direction. The two check valves are connected in parallel fashion opened toward the main cylinder and the second check valve has a prestress force. Thus, when the pressure medium flows from the main brake cylinder to the wheel brake cylinder, the wheel brake cylinder can be operated at unhindered pedal speed. However, as long as the prestress is maintained in the second check valve, a maximum reset force is not exceeded upon aeration of the brakes. In addition, the pulsation of the operating pedal is so heavily damped by the continually open throttle valve as to no longer be experienced as unpleasant by the driver.
SUMMARY OF THE INVENTION
A throttle device in a hydraulic line according to the present invention is intended less to damp vibrations than to limit the maximum flow speed during operation in the first flow direction, and also to limit the flow speed to a certain value when the fluid is pushed back in a second flow direction. The throttle device may be used in a hydraulic actuator for a vehicle clutch in which the fluid flows in the first flow direction during disengagement of the clutch and the fluid is pushed back in the second direction via the diaphragm spring of the clutch. Limiting the flow speed in the second flow direction prevents torque peaks from occurring in the drive train when the transmission is connected to the crank shaft of the internal combustion engine. Such torque peaks arise due to excessively fast engagement of the clutch and lead to overload. The engagement speed is set at an experimentally established value, which is not exceeded even in the event of fast shifting. Although the system is equipped with a throttle to limit the engagement speed, the engagement speed must not be allowed to fall below a permissible lower limit, which may occur at low temperatures. If possible, the disengagement speed should not be impaired.
In designing throttle devices in hydraulic adjustment devices for motor vehicle clutches, it is necessary to take into account the noise created, in particular, at the high flow speeds reached when the clutch is engaged too quickly because the driver slips off the clutch pedal. It has therefore been necessary to equip the throttle device with a disk whose passageway has a diameter designed to prevent the static pressure from dropping locally below the damping pressure of the fluid to prevent cavitation of the fluid flowing through the throttle. The vapor bubbles formed during cavitation collapse and may produce sound radiations. In view of this characteristic, it is advantageous to equip the passage with a funnel-shaped inlet and/or outlet in the channel widenings that prevent the flow from separating at the passage and thereby prevent cavitation and noise associated with the collapse of the vapor bubbles formed during cavitation.
The object of the invention is to provide a throttle device for installation in a hydraulic adjustment device for a vehicle clutch that limits the engagement speed of the clutch to a maximum value without producing disturbing noise.
The object is met by a throttle device for installation between a cylinder of a hydraulic adjustment device having a housing and a cylinder interior and a hydraulic line for establishing a throttle resistance to a flow of hydraulic fluid in at least one of two opposing flow directions. The throttle device includes a disk having a passage movably mountable in the hydraulic line, the disk and the hydraulic line being configurable for forming a channel between the disk and the hydraulic line when the disk is mounted in the hydraulic line, a first stop for preventing movement of the disk past the first stop in one of the two opposing flow directions, and a second stop for stopping movement of the disk in the other of the two opposing flow directions, wherein the disk is movable between a first position whereat the disk abuts the first stop and a second position whereat the disk abuts said second stop.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the dislcosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
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Ebert Angelika
Grosspietsch Wolfgang
Krappmann Klaus
Pagels Olaf
Riess Thomas
Cohen & Pontani, Lieberman & Pavane
Mannesmann Sachs AG
Ryznic John E.
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