EP1209366B1 - Actuatotor for use in a motor vehicle - Google Patents

Description

The invention relates to an actuating device, in particular for the Use in motor vehicles.

A wide variety of actuating devices are used in motor vehicle construction used, which is usually the comfort of the driver and the Serve vehicle occupants, but also to a large extent tasks in the Take over as part of a comprehensive security concept. The Window lifting device and the drive of the windshield wipers are only two Examples of such actuators. Under actuator In the context of the present invention, devices are predominantly closed understand that defined in response to a signal with the addition of auxiliary energy Start actions.

The majority of actuators in motor vehicle construction uses electrical actuators, especially electric motors, as well the window lifting device already mentioned and the drive of the Do windshield wiper system. But there are also numerous Actuators that work mechanically and / or operated by hand become. An example of this is the actuator for opening the Bonnet or tailgate, which are usually levers and cables includes. The adjustment of the fresh air supply nozzles takes place usually by hand using an integrated in the nozzle and on the nozzle arranged mechanical actuator.

Actuators for motor vehicles, the tasks under a Security concept take over are often combined with sensors. These sensors generate when certain boundary conditions exist Signal which is fed to the actuating device and activates it. An example of such an actuator is the gas generator an airbag module. If necessary, this is activated by a signal that is generated by a sensor, the sensor often being a Accelerometer is the one when a permissible is exceeded Acceleration generates a signal. This signal works together with Auxiliary energy introduced, for example, the ignition of a pyrotechnic Primer charge and / or the opening of a pressurized gas reservoir, wherein the gas generated or the gas released fills the airbag. Hiebei is the action started by the actuator filling the Airbag.

In the far most common use cases come as Actuators electric drives or electric motors for Use, the number of actuators used is strong overall increases. This leads to an increase in the total weight of the Vehicle also to an increased energy requirement, which in the case of electric drives or electric motors from those in the motor vehicle installed battery must be covered. Corresponding to the elevated Energy requirements by increasing the capacity of the battery in turn leads to a weight increase, with the battery being disadvantageous in particular high ratio of mass to performance is characterized. Also disadvantageous in the case of electrical actuators, this is mandatory electrical line between battery as energy source and Actuator.

In addition, the electric drives also include mechanical ones Components, which is why, like mechanical actuators in principle, are subject to the stick-slip effect disadvantageously. caused is the stick-slip effect due to the sliding between the friction occurring relative to each other. Become the components which can be moved and are in contact by the Electric drive is subjected to forces, so there is a displacement of the Components against each other only when the external force, the static friction occurring in the interface between the in contact stationary components. This force decreases with the beginning of the Relative movement a value corresponding to the sliding friction coefficient, when falling below that defined by the sliding friction coefficient Sliding friction force the relative movement comes to a standstill again. At a The so-called force is not constantly applied from outside Stick-slip effect, in which the components alternately adhere to one another or slide. The consequence of stick-slip effects is that there is no linear relationship between the force applied and that of the actuator there is a subordinate component, and small forces inherently cannot be generated.

As mentioned above, the number of vehicles increases used actuators and with them the total weight of the Motor vehicle too, with electric drives being disadvantageous in particular characterized by a high ratio of component weight to actuation force and thus contribute greatly to weight gain.

In addition, these electric drives may not always be in the frame of a passive safety concept, because with they do not have the necessary response or adjustment times can. For example, a sufficiently quick positioning is one Bonnet in a position advantageous for the opponent of the accident electric drive according to the prior art is not possible because the for the time provided for this process is insufficient or the Electric motor requires unacceptably long adjustment times.

Furthermore, electric drives or electric motors are due to their complex structure and the high number of sensitive components in particular generally more prone to failure than other actuators, especially mechanical actuators. In addition, by Use of the mechanical components already mentioned and with stick-slip effects associated with them usually lubricate them Parts required, which is why these actuators for maintenance and maintenance must be arranged accessible. Another disadvantage is justified by the fact that these actuators one require careful and exact installation in order to work properly ensure, in particular, for example, jamming or To prevent the moving parts from blocking.

Against this background, it is the object of the invention, a Actuating device, in particular for use in motor vehicles, to introduce the disadvantages of the actuating devices according to the prior art the technology reduces or eliminates, in particular a faster Responsiveness or a shorter adjustment time and should a smaller ratio of component weight to actuation force Has.

This problem is solved by an actuator with a compressed pressure medium storage and a pneumatic Actuator in which the memory and the pneumatic actuator are connected are connected and the connection can be closed by means of a valve and in which the pneumatic actuator has an axially and radially elastic hose comprises, whereby by pressurizing the pneumatic actuator The diameter of the hose increases and the length of the hose increases shortened and the usable by the shortening distance x to Actuation of a further, downstream device is used.

By using a filled with a compressed print medium The actuation device according to the invention is memory as an energy source a self-sufficient unit that in particular does not rely on a battery is instructed as an energy source. This is precisely the case in motor vehicle construction reasons described in the introduction are advantageous since the number of Actuators in vehicle construction increases and an increase in Battery capacity is undesirable due to the associated disadvantages. In addition, the actuating device according to the invention due to its Independence regardless of any existing or not existing energy sources can be arranged. For example, an im Actuator built-in rear of the motor vehicle does not have a possibly arranged in the front area battery, whereby the complex and costly laying of additional electrical Lines are omitted.

In addition, the use of the pneumatic actuator ensures Actuation device according to the invention for essential advantages the actuators known from the prior art. In particular, the design of the pneumatic actuator and the one in it Integrated axially and radially elastic hose ensure an advantageous and improved operating behavior of the actuating device.

The behavior of the elastic hose with regard to its strength and the tension states present in the hose can be derived approximately from the consideration of a straight, circular cylindrical container - a so-called "boiler shell". The so-called membrane stress state in the boiler jacket is described by a stress σ _I acting in the circumferential direction and a stress σ _II acting in the longitudinal direction. With an internal pressure p in the hose, a hose radius r and a wall thickness s of the hose jacket, the circumferential tension or longitudinal tension result as follows: σ I = p * r / s σ II = ½ * p * r / s

These equations show that the longitudinal tension σ _II or the longitudinal force F is proportional to the internal pressure of the hose if it is assumed that the hose radius r and the jacket thickness s of the hose are constant. This results in an approximately linear relationship between the longitudinal force F, which acts on a further, downstream device for the purpose of actuation, and the pressure p present in the interior of the hose. This ensures in a simple manner that a defined longitudinal force F is produced by setting a defined pressure p in the elastic hose, the desired settings being able to be achieved in a targeted and repeatable manner as a result of the clearly defined characteristic curve between pressure p and force F. A clearly defined relationship between the internal pressure p and the force F is only made possible, inter alia, by the fact that the stick-slip effect which occurs in the prior art in the case of actuating devices is omitted in principle because there are opportunities for training as a result of the structural design of the pneumatic actuator corresponding friction effects are missing.

The actuator is operated in such a way that by opening the Valve the connection between the memory and the pneumatic actuator will be produced. As a result of the open valve, the pneumatic actuator due to the compressed print medium stored in the memory acted upon, wherein the pressure medium flowing into the hose to a Increases the inner pressure of the hose leads. This causes the elastic to expand Hose in the radial direction, thereby simultaneously contraction of the Hose takes place in the longitudinal direction. The shortening of the hose or the Distance x, which is characterized by the length difference between the relaxed and the hose shortened by contraction is used for the Actuation of a downstream device used.

For example, the hose with its free end, i.e. with the end that is opposite the end connected to the memory, in the manner with a downstream device connected by the contraction available longitudinal force F of the hose for actuating the downstream device can be used. Generally the one with the hose connected device endeavors by the Pressurization to follow contraction of the hose and track the movement of the free end of the hose while doing so to cover the distance x required for the contraction. this leads to then ultimately to the intended actuation of the device.

In addition, the actuating device according to the invention is based on the principle less susceptible to faults and easier to install, which among other things the result is that the presented actuator no special maintenance, in particular no lubrication of individual components required. It is easier to install Actuator not only due to the fact that it is a independent, self-sufficient functional unit, but also because of pneumatic actuator is significantly less sensitive to installation errors, with the possibility of any guidance of the elastic Hose exists, which is not always linear in the installed state must be arranged.

Actuators in which the valve is an are advantageous Fast switching valve is. This allows the pneumatic actuator from Storage supplied amount of pressure medium regulated in small steps and can be dosed exactly. In addition, both the response and also the adjustment time of the overall "actuating device" system is shorter, these times being the individual response and adjustment times all of the elements of the device partially cumulative. Thus leads the improvement of an element to an improvement of the overall system.

Actuators in which the memory and the pneumatic actuator are connected to each other via a pressure line. This increases the flexibility when installing the device compared to the Embodiments in which the pneumatic actuator without Interposition of a pressure line is connected directly to the memory. A flexible pressure line enables an arrangement of the pneumatic Actuator and the memory each independently, but also the Supply of several pneumatic actuators from one memory by means of several pressure lines.

Actuators are advantageous in which between the memory and the pneumatic actuator is arranged a pressure reducer which Reduces the pressure of the compressed print medium. This makes it possible to store the print medium highly compressed in the memory. Will that If there is no pressure reducer, the pressure medium only exits from the memory, when entering the pneumatic actuator and possibly in the throttled pressure line arranged between these components, exists at the addition of a pressure reducer and thus an additional one Throttle point the possibility of a much higher pressure drop between Realize memory and actuator, thereby reducing the pressure medium under essential higher pressures can be stored in the memory. Consequently, at Using an additional pressure reducer the internal pressure of the compressed storage medium storing memory a multiple of permissible internal pressure of the elastic hose.

Assuming the same storage volume, this leads to a larger one Total mass of storable print medium. On the other hand, the Use the pressure reducer to reduce the size of the Storage if an equal mass total to be stored Media is used. A reduction in the storage volume is under the aspect of reducing the space required basically viewed as cheap, with an increase in storable mass of pressure medium is also advantageous in such a way that the actuator corresponding to a larger available quantity of pressure medium can be operated more often.

Actuators in which the working pressure of the pneumatic actuator, the maximum internal pressure p of the hose Pressurization of the actuator is less than the pressure of the compressed Print media in memory.

Such an embodiment of the actuating device according to the invention has, as already indicated above, advantages in two ways. On the one hand the required storage volume with constant medium mass all the more smaller the higher the print medium is compressed. On the other hand, stocks the storage - assuming the same storage volume - with increasing Internal pressure of a larger mass of pressure medium, which reduces the number of Actuations of the pneumatic actuator is increased. This has the consequence that the memory, for example, designed as a gas pressure cartridge less frequently must be replaced or filled.

Actuators which are characterized in that that in the hose of the pneumatic actuator a displacement body is arranged.

This advantageous embodiment is based on the idea that a Hose that has the smallest possible pressure medium Has hose volume when using the same storage - so equally large storage volume and identical storage pressure provided - can be operated more often than a hose that has a larger one with hose volume that can be acted upon by a pressure medium.

Provided the hose has a hose volume V _s in the relaxed state and has approximately the ambient pressure as the internal pressure. Then, when the pneumatic actuator is pressurized and the desired internal pressure increase of the hose to, for example, 6 bar, on the one hand so much pressure medium must be supplied that a pressure increase of 5 bar takes place in the hose volume V _{s of} the relaxed hose and possibly a volume change Δ V des caused by a volume increase Hose is also filled with medium under 6 bar pressure. The mass of pressure medium to be introduced into the hose is thus composed of two parts.

By arranging a displacement body V _v in the hose of the pneumatic actuator, the hose volume V _s is reduced by the volume V _{v of} the displacement body. As a result, less pressure medium must now be introduced into this hose in order to achieve the same increase in internal pressure. The saving in pressure medium is proportional to the volume of the displacer V _v .

A reduction in the hose volume V _s by directly reducing the hose length or the hose diameter is generally not expedient, since the longitudinal force F to be generated must be of a predetermined size and this is a function of the square of the hose radius r. A shortening of the hose is not possible in most applications. This is usually the case when it is not primarily the longitudinal force to be generated that is important, but rather the distance x made usable by the contraction of the hose. It should be taken into account here that the length of the distance x realized by the contraction of the hose depends not only on the internal pressure but also on the total length of the hose.

Actuating devices in which the displacement body is cylindrical and are arranged coaxially to the hose are advantageous. The displacement body thus corresponds to the preferred outer shape of the hose, and it is precisely through the similarity of the outer shape of the displacement body and the hose that a maximum reduction in the hose volume V _s can be achieved.

The invention furthermore relates to the use of one of the aforementioned actuators for positioning a hood of a motor vehicle, the pneumatic actuator with its free end, i.e. with the end, the end connected to the memory opposite, is connected in the manner with the hood that the hose if the length is reduced due to pressurization, the bonnet from one Rest position, in which the hood is arranged in a closed position is in a working position in which the bonnet is positioned elevated, emotional.

The background to the targeted positioning of the bonnet is pedestrians and cyclists who are among the weaker road users from to provide protective devices on the part of the motor vehicles. It did studies have shown that the relevant impact zones of Pedestrians and two-wheelers in the area of the front section and here in particular in the area of the hood of the motor vehicle. On Solution to minimize the risk of injury in the event of an impact The hood is the targeted positioning of the hood in front of the Impact of the pedestrian or the two-wheeler. With the help of Positioning devices can be the usually small distance between Enlarge the engine and engine block so that there is a risk of the Head is reduced to the engine block. By lifting the The bonnet is the distance between the bonnet and the engine block thus increasing the usable deformation path when a person collides.

Initially, there were no actuators for lifting the bonnet reversible systems, e.g. pyrotechnic propellants used according to Activation by a sensor the bonnet in the preferred position have proceeded. The further development of this approach has to Use of reversible systems, with the actuators used the bonnet after an impact or in the event of a fault Activation of the system have returned to their original position.

The available actuators, especially the pyrotechnic primers have more or less major disadvantages compared to the presented Actuator on.

The presented operating device according to the invention, however, has all necessary properties on an actuator for lifting a bonnet is mandatory. Especially the short ones Response and adjustment times are shown when using the Actuating device according to the invention for positioning a Bonnet of a motor vehicle as extremely cheap.

Figur 1

den theoretischen Spannungszustand im Mantel des Schlauches anhand einer perspektivischen Darstellung eines Schlauchsegmentes, und

Figur 2

eine Seitenansicht einer ersten Ausführungsform der Betätigungsvorrichtung zur Positionierung einer Motorhaube eines Kraftfahrzeuges in der Ruheposition, und

Figur 3

eine Seitenansicht der in Figur 2 gezeigten Ausführungsform der Betätigungsvorrichtung zur Positionierung einer Motorhaube eines Kraftfahrzeuges in der Arbeitsposition.

The invention is explained below using an exemplary embodiment according to the attached figures. Here shows:

Figure 1

the theoretical stress state in the jacket of the hose based on a perspective view of a hose segment, and

Figure 2

a side view of a first embodiment of the actuating device for positioning a hood of a motor vehicle in the rest position, and

Figure 3

a side view of the embodiment shown in Figure 2 of the actuator for positioning a hood of a motor vehicle in the working position.

FIG. 1 shows the theoretical, two-axis state of stress in the jacket of the hose 4. The normal stress σ _II acts in the direction of the longitudinal axis of the hose 4, the product of this normal stress σ _II and the associated annular cross-sectional area of the hose jacket forming the longitudinal force F. The circumferential stress σ _I acts perpendicular to the longitudinal stress σ _II and thus in the circumferential direction. It is twice as large as the longitudinal stress σ _II . The formal relationships have been explained in detail in the general description section and should not be repeated here.

Figure 2 shows an embodiment of the actuator as it for example for positioning a hood of a motor vehicle is used. The overall system is shown in the rest position, which in addition to the actuating device, a control unit 11, an intermediate element 9 and a hood bracket 10.

The actuating device itself comprises a memory 1, one pneumatic actuator 2 and one the pneumatic actuator 2 and the memory 1 connecting pressure line 5, between the pneumatic actuator 2 and Storage 1 both a valve 3 and a pressure reducer 6 is arranged. The pneumatic actuator 2 has an axially and radially elastic hose 4 on, in which a displacement body to reduce the hose volume 7 is arranged. With its free end 8, the pneumatic actuator is over a Intermediate element 9 with the short leg of an L-shaped and rotatable on Motor vehicle mounted hood bracket 10 connected. The valve 3 is operated by the control unit 11, i.e. opened and closed.

The actuator is activated to position the bonnet (Figure 3). For this purpose, the valve 3 is opened by the control unit 11, so that the pressure medium stored in the memory 1 after passing through the Pressure reducer 6 and the valve 3 in the hose 4 of the pneumatic Actuator 2 flows. Due to the inflowing pressure medium increases the diameter of the hose 4 with simultaneous contraction of the Hose 4. The intermediate element 9 with the free end 8 of the Pneumatic actuator 2 connected hood bracket 10 follows the Contraction of the hose 4 when pressurized in such a way that it is rotates around their bearing 12. The connection point of the intermediate element 9 with the short leg of the hood bracket 10 also migrates in Direction of the longitudinal axis of the hose 4 and thus in the direction of Contraction of the hose 4. The second longer leg of the motor bracket During this rotation, 10 lifts one which is mounted on the bonnet holder 10 Bonnet in an elevated position.

LIST OF REFERENCE NUMBERS

1

Storage

2

Pneumatic actuator

3

Valve

4

tube

5

pressure line

6

pressure reducer

7

displacer

8th

free end

9

intermediate element

10

hood holder

11

control unit

12

camp

Claims (8)

1. Actuating device, in particular for use in motor vehicles, having a store (1) stocking a compressed pressure medium and a pneumatic actuator (2), in which the store (1) and the pneumatic actuator (2) are connected to one another and the connection can be closed by means of a valve (3) and in which the pneumatic actuator (2) comprises an axially and radially resilient hose (4), wherein the diameter of the hose (4) is increased and the length of the hose (4) is shortened by exposing the pneumatic actuator (2) to pressure and in which the distance x which can be utilised due to shortening serves for actuating a further, subsequent device.
2. Actuating device according to claim 1, characterised in that the valve (3) is a rapid-switch valve.
3. Actuating device according to one of the previous claims, characterised in that the store (1) and the pneumatic actuator (2) are connected to one another via a pressure pipe (5).
4. Actuating device according to one of the previous claims, characterised in that a pressure reducer (6), which reduces the pressure of the compressed pressure medium, is arranged between the store (1) and the pneumatic actuator (2).
5. Actuating device according to one of the previous claims, characterised in that the working pressure of the pneumatic actuator (2), the maximum internal pressure p of the hose (4) during exposure of the actuator (2) to pressure, is less than the pressure of the compressed pressure medium in the store (1).
6. Actuating device according to one of the previous claims, characterised in that a displacer (7) is arranged in the hose (1) of the pneumatic actuator (2).
7. Actuating device according to claim 6, characterised in that the displacer (7) is designed to be cylindrical and is arranged coaxially to the hose (4).
8. Use of an actuating device according to one of the previous claims for positioning an engine bonnet of a motor vehicle, characterised in that the pneumatic actuator (2) with its free end (8), that is with the end which is opposite the end connected to the store (1), is connected to the engine bonnet such that the hose (4) during length shortening due to exposure to pressure moves the engine bonnet from a rest position, in which the engine bonnet is arranged in a closed position, into a working position, in which the engine bonnet is positioned elevated.

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