Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
1998-08-26
2001-04-24
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C091S450000, C091S465000, C137S596170
Reexamination Certificate
active
06220288
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is based on an electro-hydraulic control device and, more particularly, to an electro-hydraulic control device for a hydraulic servo motor for controlling a volume flow, having a blocking valve arranged in a housing, whose movable seat valve body is inserted into a connection between a motor chamber and a return flow chamber for securing the motor chamber, and having a proportional magnet with an armature-actuated tappet for actuating the blocking valve.
2. Prior Art
This type of electro-hydraulic control device is already known from U.S. Pat. No. 3,667,722, by means of which a delicate proportional volume control is possible. The check valve protecting the hydraulic servo motor with its load is here designed as a pilot seat valve, so that the leakage is as small as possible. This control device can be used as a lowering brake valve, wherein the actuating forces are as low as possible and therefore the proportional magnet can be made small. It is disadvantageous in connection with this control device that only a 2/3 valve function can be represented, wherein no additional valve functions can be performed by the lowering element designed in accordance with seat valve techniques. In order to keep the actuating forces low here, a one-armed lever, with which a force transfer is performed, is placed between the proportional magnet and the actual seat valve. The force for actuating the check valve is transmitted by an unblocking member, which is made in a pin shape and with a narrow diameter, so that it cannot take on additional functions. The volume flow appearing during the lowering of a load is here only controlled by a valve cone at a seat valve body, so that the flow forces appearing particularly at high loads can considerably interfere with the proportional work functioning of the check valve. Therefore the seat valve body, which here is controlled purely hydraulically, easily tends to oscillate, particularly when pulling loads or changing load directions occur. The ball in the seat valve body, which operates as a pilot member, does not have pressure compensation. In addition, the control device is relatively elaborately constructed, to which the transmitting lever and the valve case for the check valve in particular contribute.
Furthermore, an electro-hydraulic control device had already been proposed in an older patent application, P 195 22 746.8, which operates with 4/2 valve modules. In this case two such 4/2 valve modules with additional non-return valves are arranged in a circuit in such a way that a control valve for a double-acting servo motor results. A seat valve element and a slide element are combined with each other in each 4/2 valve module in such a way, that they have a common, one-piece control member. In this not prepublished control device, this one-piece construction of the control member in the 4/2 valve module leads to a relatively elaborate construction; in addition, difficulties arise in this 4/2 valve module because of close longitudinal tolerances when adjusting the control edges to each other. Form and play tolerances are harder to control with relatively long slides in particular. Furthermore, stepped slides in stepped bores with little play make high demands in respect to deviations from running true; in addition, the stepped slides cannot be ground centerless.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved electro-hydraulic control device of the above-described type, especially for a hydraulic servo motor for controlling a volume flow, which does not have the above-described disadvantages.
According to the invention the electro-hydraulic control device for a hydraulic servo motor for controlling a volume flow, has a blocking valve arranged in a housing, whose movable seat valve body is inserted into a connection between a first motor chamber and a return flow chamber for securing the motor chamber, and has a proportional magnet with an armature-actuated tappet for actuating the blocking valve, and has a longitudinally movable unblocking member, which is separated from the blocking valve and slidingly guided in the housing, which is inserted into the operation connection between the tappet of the proportional magnet and the blocking valve, and is characterized in that, the unblocking member and the tappet of the proportional magnet are arranged coaxially with respect to each other and the unblocking member is embodied as a longitudinal slide which, with one control edge, controls the connection between an inflow chamber and a second motor chamber, wherein the latter is arranged in the slide bore receiving the longitudinal slide next to the return flow chamber and that the longitudinal slide essentially has the same exterior diameter as the seat valve body, and that upon actuation by the proportional magnet both connections are opened or closed in the same direction.
In contrast hereto, the electro-hydraulic control device of the invention has the advantage, that with a simple construction it represents a 4/2 valve function, wherein a lowering element designed in accordance with seat valve technology keeps the leakage as small as possible. The control device can be used in many ways because of its 4/2 function, and in addition is constructed in a cost-efficient and compact way. The control device can be employed as a lowering brake valve, by means of which a sensitive proportional volume control is possible. Because of the two-piece construction, a control edge adjustment can be realized in a simple manner by the length adaptation of the transfer edges.
Advantageous further developments and improvements of the electro-hydraulic control device possible by means of the measures noted in the dependent claims and the following disclosure.
In a preferred embodiment of the invention the seat valve body and the longitudinal slide are guided in a continuous slide bore, particularly with a generally uniform diameter, in which, lying next to each other and arranged spaced from each other in a direction toward the proportional magnet, four chambers are provided for the first motor connection, the return flow connection, the second motor connection and the inflow connection. A valve seat, in particular with a smaller diameter in comparison with the slide bore, which is associated with the seat valve body, is arranged in this slide bore between the first motor chamber and the return flow chamber. It is possible to achieve a particularly advantageous compact structure which, with its four working chambers, is assembled in a particularly space-saving manner.
Other advantageous embodiments are possible in which the blocking valve is a pilot valve, whose seat valve body receives a pilot member, which can be unblocked by the longitudinal slide via a transfer bolt. Preferably the pilot member is a pressure-compensated pilot cone. This makes it possible to achieve small actuation forces by hydraulic unblocking, so that proportional magnets of small size can be employed.
In another preferred embodiment an axially oriented extension, which protrudes into the return flow chamber, has a transfer bolt on its end, and a transfer shoulder associated with the seat valve body is arranged on the extension. The extension is provided between the longitudinal slide and the seat valve body on one of the two components, preferably on the longitudinal slide on its side facing away from the proportional magnet. In this embodiment the seat valve body and the control slide can cooperate like a mutual, one-piece control member, wherein the control slide takes the seat valve body along mechanically, as is the case in connection with a conventional control device. In this case pulling loads in particular can be better managed.
A particularly simple and cost-effective embodiment, which is mainly suitable for small regulating directional control valves with relatively low switching capacity, results when the longitudinal slide can be directly actuated by the armature tappet, and is pr
Lueues Holger
Sandau Hartmut
Schumacher Werner
Michalsky Gerald A.
Robert & Bosch GmbH
Striker Michael J.
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