Patent Application
20050120714
This invention relates to a device for transmitting a displacement of an actuator using an elastomer ring.
The use of devices for transmitting a displacement of an actuator is known in the field of injection valves. The device thereby sets the required clearance for example between the actuator and a setting element to be controlled. Depending on the embodiment of the device, it is also possible to achieve a translation of the displacement of the actuator. For example, with piezoelectric actuators, it is advantageous to increase the relatively slim displacement lift of the piezoelectric actuator, in order to control for example a closing element of a valve or an injection needle.
To transmit the displacement, transmission chambers are provided that are delimited by a first and a second piston and a housing. The transmission chambers are filled with a transmission medium, such as hydraulic oil. For the device to function correctly, it is necessary for there to be minimum pressure in the transmission chambers. To this end, the transmission chambers are hydraulically connected to a compensation chamber. The compensation chamber is used to compensate any change in volume of the transmission chambers and to provide the transmission chambers with a transmission medium at a defined pressure. For the volume of the compensation chamber to be flexible, it is known for the compensation chamber to be sealed using a metal membrane, enabling the volume of the compensation chamber to change. However, sealing the chamber using a metal membrane is relatively complicated and the metal membrane itself is relatively expensive.
The object of the invention is to provide a device to transmit a displacement of an actuator, which does not require a metal membrane.
A considerable advantage of the device according to the invention is that the compensation chamber is delimited by an elastomer ring. The use of elastomer makes it possible on the one hand to vary the volume in the compensation chamber and on the other to subject the fluid in the compensation chamber to the action of pressure. By using a ring made out of elastomer, it is possible to seal relatively high pressures via the elastomer.
In a simple embodiment, the elastomer ring is connected in a circumferentially sealed manner to an inner wall of a housing on the outside and to a piston rod on the inside.
Depending on the manufacturing method used, it is advantageous to provide a first and/or a second sleeve on the outside and/or inside of the elastomer ring. The first outer sleeve is connected in a circumferentially sealed manner to the inner wall of the housing and to the elastomer ring. The second inner sleeve is connected in a circumferentially sealed manner to the first piston or the piston rod and to the elastomer ring. By using the outer sleeve, it is possible to configure the inner wall of the housing so that it is shorter. Furthermore, the surface of the inner wall of the housing does not have to be suitable for use in a vulcanization process, the elastomer being connected in a sealed manner to the inner wall. Greater flexibility is therefore provided in manufacturing the inner wall. It is also possible, for example, for the outer sleeve to be connected in a circumferentially sealed manner to a face end of the housing. Increased flexibility is therefore provided with respect to the region of the connection between housing and elastomer ring.
The use of the second, inner sleeve also makes it possible to manufacture the piston and/or the piston rod independently of the hydraulically sealed connection to the elastomer ring. Increased flexibility is therefore also provided in manufacturing the piston rod.
Furthermore, it is possible to carry out the vulcanization process, in which the elastomer is connected in a circumferentially sealed manner to the inner and outer sleeves, independently of the housing and first piston. It is not until after the process of connecting the elastomer ring to the outer and inner sleeves that the outer and inner sleeves are welded in a circumferentially sealed manner to the housing and/or to the piston or piston rod. The first and second sleeves are preferably made of steel.
The elastomer used has an elasticity that can however diminish when subjected to high pressures in the compensation chamber or for longer periods. To stabilize the elastomer ring, a tension device is preferably provided, which subjects the outside of the elastomer ring to the action of pretension. In this way, the elastic function of the elastomer ring is supported by the tension device.
A preferred embodiment of the tension device is the configuration of a spiral spring, which is clamped between the elastomer and a lay-on surface firmly connected to the piston rod. This creates a means of pretensioning which is independent of the position of the first piston.
To introduce the pretension effectively, it is advantageous to provide a pressure transmission device, which transmits the pretension evenly onto the elastomer ring. By transmitting the pretension evenly, it is possible to avoid local overloading of the elastomer ring.
The pressure transmission device is preferably in the form of a ring.
The ring preferably has a graduated guide, the ring being guided on the piston rod and furthermore the part of the ring with the larger diameter being supported on the elastomer ring. By guiding the ring parallel to the piston rod, the pretensioning force is evenly transmitted to the elastomer ring over the entire ring surface. By guiding the ring along the piston rod, it is possible to avoid tilting the ring and thus only partially loading the elastomer ring.
It is furthermore advantageous to protect the surface of the elastomer ring on which the tension device is acting by means of a protective film. The function of the protective film is to reduce the amount of wear and tear on the surface of the elastomer ring. The protective film is preferably configured in the form of a rubber film, which is affixed to the ring.
The invention will now be shown in more detail with reference to the figures, in which;
The invention is shown below using the example of an injection valve 1. However, the use of the transmission device according to the invention is not restricted to injection valves, as the transmission device according to the invention can be used in diverse technical fields to transmit a displacement of an actuator.
Depending on the embodiment, the transmission device 3 can also have an inverse function, so that the setting element that is mechanically linked to the injection needle 4 is withdrawn from the injection needle 4 when the actuator 2 is displaced in the direction of the injection needle 4.
Instead of the translation function, the transmission device 3 can also have a pure transmission function, the displacement of an actuator being transmitted in order to effect a corresponding displacement of the injection needle.
A first piston 6 is provided in the form of a sleeve that is open on one side. The sleeve-shaped part of the piston delimits a first transmission chamber 10, into which a second piston 7 is guided. The first and second pistons 6, 7 delimit the first transmission chamber 10. The first piston 6 is in turn guided in a cylinder-shaped chamber of a housing, which has an end surface 15 on the face end to the first piston 1. An aperture 16 is placed in the end surface 15, through which a piston rod of the second piston 7 is guided. The piston rod has a smaller diameter than the second piston 7. The piston rod passes via a ring-shaped recess in the wider diameter of the second piston 7. A second transmission chamber 11 is configured between the end surface 5, the recess and a ring-shaped face surface 17 of the first piston 6. The second transmission chamber 11 is hydraulically connected to the first transmission chamber 10 via a first sealing gap 18, which is configured between a side wall of the second piston 7 and inner wall of the first piston 6. The first transmission chamber 10 is delimited by a second end surface 19 of the first piston 6 and a second face surface 20 of the second piston 7. The first sealing gap 18 is designed in a narrow manner so that transient pressure differences are not compensated. Furthermore, the second transmission chamber 11 is connected to a compensation chamber 22 via a second sealing gap 21, which is configured between the outer wall of the first piston 6 and the inner wall of the housing 4. The first transmission chamber 10 is hydraulically connected to the compensation chamber 22 via a bore 60, which is placed in the first piston 6. The first piston 6 passes into the piston rod 51 via a second recess. The piston rod 51 is essentially in the form of a cylinder and has a smaller diameter than the first piston 6.
In a first embodiment according to
The geometry of the elastomer ring is such that the elastomer ring has sufficient elasticity and at the same time the necessary stability to delimit the pressure of the compensation chamber 22. Due to its elastic properties, the elastomer ring should enable the volume in the compensation chamber to grow and also prevent too high an increase in pressure.
The first and second transmission chambers 10, 11 and the compensation chamber are filled with a transmission fluid. In this way, it is possible to achieve a motive link between the first and second pistons 6, 7. If the first piston 6 is moved deeper into the housing 5 by the actuator, the second piston 7 is in turn moved deeper into the housing 5. Inverse motion is thus achieved between the first and second pistons 6, 7. The compensation chamber 22 is connected to the second transmission chamber 11 via the second sealing gap 21, the second sealing gap 21 being designed in such a narrow manner that transient pressure differences between the transmission chamber 11 and the compensation chamber 22 are not compensated. The term transient is understood to mean activating times of the actuator that the actuator requires in order to activate a setting element, in the example shown to activate the injection needle.
Pressure differences lasting for a longer period of time are compensated via the second sealing gap 21 between the second transmission chamber and the compensation chamber 22. In this way, it is possible to automatically achieve a compensation of clearance. The first and second pistons 6, 7 can therefore always be laid onto an actuator and/or a setting element. The transmission element is preferably under pressure. The pressure can for example be transmitted to the transmission fluid via the elastomer ring 50 using a tension device. Instead of the embodiment shown in
In a preferred embodiment according to
In a preferred embodiment, a tension device is provided, which is used to pretension the elastomer ring 50 in the direction of the compensation chamber 22. In a simple embodiment, a spiral spring 54 is provided for this purpose, which is clamped between a stop ring 55 and the elastomer ring 50. The stop ring 55 is connected firmly to the piston rod 51. In a preferred embodiment, a pressure transmission device is provided between the tension device and the elastomer ring 50, said pressure transmission device transmitting the pretension force of the spiral spring 54 having a larger surface to the surface of the elastomer ring 50. The pressure transmission device is preferably configured in the form of a pressure ring 56. The pressure ring 56 preferably has a support surface essentially corresponding to the surface of the elastomer ring 50. In a further preferred embodiment, the pressure ring 56 has a graduated guide, the pressure ring 56 being guided by the piston rod 51 in the area of the guide with the smaller diameter. In this way, the pressure ring 56 is guided axially, so that the pressure ring 56 is not able to tilt. In this way it is possible to ensure that the pressure ring 56 evenly transmits the pretension force preset by the spiral spring 54 onto the elastomer ring 50 via the lay-on surface of the pressure ring 56.
In a preferred embodiment, a protective film 57 is affixed to the surface of the pressure ring 56, which is assigned to that of the elastomer ring 50. The protective film 57 is comprised for example of rubber and serves to protect the elastomer ring 50 from abrasion due to the pressure ring 56. The protective film 57 preferably has a greater hardness than the elastomer ring 50.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10233907.4 | Jul 2002 | DE | national |
This application is a continuation of copending International Application No. PCT/DE03/02328 filed Jul. 15, 2003 which designates the United States, and claims priority to German application no. 102 33 907.4 filed Jul. 25, 2002.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/DE03/02328 | Jul 2003 | US |
| Child | 11034499 | Jan 2005 | US |
