DE3019298A1 - Seat belt rewind mechanism driven by DC motor - automatically reels in belt when fastener is released - Google Patents

Abstract

The motor replaces the more conventional winding mechanism operated by a coil spring. The advantages offered by the motor drive are that the recoiling torque is independent of the length of belt which has been unreeled such that the tension is the belt when in use can be set at a low value, and that operation is quieter. The motor is coupled to the shaft of the drum on which the belt is wound when not in use, typically the coupling is through a reduction gear. The motor supply is switched off when the belt is in the fully reeled-up condition. To unreel the belt it can be pulled against the torque or more preferably, a slipping clutch may be provided. When in use, the motor torque may be reduced, or the motor switched off, by switches in the seat belt fastener.

Description

R e ctio n g Automatic belt retractor for seat belts, in particular in motor vehicles The invention relates to an automatic belt retractor for seat belts, especially in motor vehicles, with one in the winding direction belt take-up shaft acted upon by a driving force and preferably with a webbing and / or vehicle-sensitive locking system.

Automatic seat belt retractors come in many different designs known. What they all have in common is that the belt winding shaft with the help of a spring, in particular spiral spring is wound, which accordingly constantly a Pulling force on the belt -. This results in disruptive effects the user, on the one hand from the natural aging of the spring, the noise and the large friction losses between the individual spring coils result, on the other hand, it can also be seen in the fact that the The further the belt is unwound from the take-up shaft, the greater the tensile force or "moved out".

This means that the tensile force does not only depend on the unwound length of the Belt, but possibly also on the position of the vehicle seat in the vehicle away. This relatively large and in particular variable tensile force on the belt is perceived as unpleasant and annoying by many users and causes them often even not wearing the seat belt at all.

In view of this, the invention has for its object to provide a automatically creating Xn belt retractors free from such troublesome effects and thus contributes to the increased use of seat belts.

The inventive solution to this problem and advantageous embodiments and further developments of the same result from the content of the claims, which are placed in front of this description.

In the simplest embodiment of the invention, the automatic The belt retractor only has a DC motor on and a switch that controls it The engine switches off when the seat belt is taken off by the person concerned and is wound onto the belt take-up shaft as intended. Once the strap is withdrawn from the take-up shaft, the motor switches on again, whereby he tries to turn the belt winding shaft in the winding direction.

The belt can be unwound against the winding force of the motor, why the engine can be designed so that the belt can be pulled off easily and without further possible and the retraction force generated in the belt reduced to a minimum is. After the buckle is closed, the one under tension eliminates it Motor a possibly existing belt slack and compensates in the following every change of position of the user. After unlocking until the buckle is the belt is drawn in to the end position and the switch switches off the motor.

Problems of structural design and adaptation to existing dimensions can be overcome in that the motor has a reduction gear. the belt winding shaft is connected.

In addition, a coupling can be installed between the motor and the belt take-up shaft be switched on. This clutch can be used as a torque-dependent clutch, especially designed as a slip friction clutch, which allows the Unwinding the belt from the belt take-up shaft without the DC motor - if necessary ~ with Gearbox - having to turn against the electrical driving force.

However, it can also be a clutch that can be actuated by the switching device are used, thieves certain operating states of the belt the belt winding shaft completely separates from their drive, so that the belt is practically powerless can be. This makes it possible to realize an embodiment in which the belt can assume two different states of tension. Basically you can This can also be achieved by the fact that the switching device is not the switching clutch but switches the motor itself on and off so that it operates intermittently will.

Another differentiation with the possibility of choosing the one you want Adapting the drive power of the motor to certain operating conditions results in if the same current motor has two separately or simultaneously controllable windings contains. This makes it possible, for example, to adjust the drive power of the motor then to be reduced significantly when the belt locks in the associated belt buckle is.

In this way, the contact pressure of the belt on reduce the user to a value that is no longer disruptive. In other operating states the motor would be switched and delivers a larger one depending on the requirements Drive power, e.g. B. when the buckle is unlocked and the belt very quickly - The switching pulses necessary for controlling the motor are made available by the switching device, the various facilities can have for detecting the respective operating state of the belt. One the A device with a switch that detects the tension state of the belt makes it possible to determine whether the belt is worn or not and / or whether there is a slack in the belt when the belt is on is available.

Furthermore, a device which detects the rolled-up state of the belt can be used with a switch that provides information about whether the belt is partially or is completely settled or not.

A device for detecting the winding direction can provide additional information des'Gurtes on the belt take-up shaft.

All of these data-collecting devices contain sensors or Switches whose signals are processed by the switching device that controls the motor then controls in accordance with the established operating state in such a way that it delivers a large, small or no drive power at all.

A fine control can also be assigned to the motor, compensates for the differences in the tensile force in the belt, which -due to the fact that with increasingly unwound Belt the winding diameter is smaller while the drive torque of the motor remains the same.

Electric motors can usually be overloaded at least for a short time. This property can be used to this effect in the belt retractor according to the invention that the engine is designed for operation as a belt tensioner and to that Can be connected via the switching device appropriately charged capacitor. If the switching device that is responsible for a network for the logical connection of Signals from the locking systems, the vehicle brakes and, if necessary, an early warning device has a corresponding signal, e.g. B. via a between the network and the Capacitor switched timer, supplies, the capacitor is discharged, and the discharge current flows through the motor, which then has a correspondingly high drive power releases and works as a belt tensioner by pulling the belt with a jerk.

In the drawing, exemplary embodiments of the invention are shown, which are explained below.

1 shows a block diagram of a drive motor for the Belt winding shaft of an automatic belt retractor, Fig. 2 shows another embodiment of the object according to FIG. 1, FIG. 3 shows a further embodiment of the object According to Fig. 1, Fig. 4a-4d different embodiments of devices for detection the reel-up condition of the belt, FIGS. 5a-5h show further embodiments of the object according to FIGS. 4, 6a-6f, different embodiments of devices for detecting the tension state of the belt webbing, Fig. 7a - 7c further embodiments of the object according to FIGS. 6, 8a-8c various embodiments of devices for detecting the winding direction of the belt, -Fig. 9a and 9b different versions of clutches.

The motor 1 shown in FIG. 1 is one DC motor which is connected in the circuit 2 of a vehicle battery 3. The motor 1 is directly connected to the belt winding shaft with its motor shaft automatic belt retractor, not shown, coupled. He will only ever driven in one direction, namely in such a way that it places the belt on the belt take-up shaft rolls up.

In circuit 2 there is a switch 4 with which circuit a is interrupted can be. This switch 4 belongs to a device to be described below, which detects the retraction of the belt. The switch 4 is open as long as the total available length of the webbing stored on the belt take-up shaft is.

When the belt is unwound from the belt take-up shaft, it closes the switch 4. This also closes the circuit 2, and the motor 1 delivers now a torque, which the belt winding shaft in the winding direction-to tried to turn.

However, since the engine 1 is designed so that its drive power only generates a tensile force in the belt which is equal to or less than that The tensile force is that of conventional belt retractors from the to the belt take-up shaft connected spiral spring is generated, the belt can counteract the drive power of the motor 1 withdrawn from its belt winding shaft and in the associated belt buckle - be locked. Since the switch 4 after. as before is closed, the delivers Motor 1 - when the belt is on, its drive power constantly and calls in the belt a tensile force emerges, which the belt without belt slack to the seated person and thereby moving person.

If the belt buckle is opened, the belt is placed on the belt take-up shaft rolled up until the device for detecting the roll-up condition hits the switch 4 opens, whereby the circuit 2 is interrupted and the motor 1 is stopped.

In some cases the tensile force generated by the motor 1 is applied in the Belt are perceived as annoying, and therefore points in the execution according to Figure 1, the circuit 2 has a branch circuit 5 with a resistor 6 and a changeover switch 7.

Instead of the resistor 6, a current regulator can also be used.

The switch 7 belongs to a device to be described below, which detects the tension of the belt.

If this device for detecting the tension state of the belt is arranged for example in the area of the seat belt buckle, when locking of the seat belt buckle, the switch 7 is actuated and the circuit 2 via the resistance 6 closed. The motor 1 then only outputs a reduced drive power and accordingly generates a lower tensile force in the belt. When the seat belt buckle is unlocked, the switch 7 switches back to the switching position shown, the motor 1 can deliver its full drive power and now also winds the belt high speed on the belt take-up shaft.

In the embodiment according to FIG. 2, the motor 1 has two different ones Windings to which separate connecting lines 8 and 9 are assigned. The windings of the motor 1 can have the same or different numbers of turns. The relationship the number of turns and thus the possible drive power of the motor can be in With regard to the different operating states of the engine or the belt and the desired tensile forces in the belt can be freely selected. In the case of the FIG The embodiment shown is the connection line leading to one winding 8 is connected directly to circuit 2, while that to the other winding Leading connection line 9 can be switched into the circuit 2 via the changeover switch 7 is.

Other circuits are possible.

In addition, a branch circuit 10 belongs to the embodiment according to FIG an electromagnet 11 and a switch 12. With the electromagnet 11 can a clutch shown, for example, in Figure 9a or 9b is actuated, which is connected between motor 1 and the belt take-up shaft. The switch 12 belongs to a device to be described for detecting the winding direction of the Belt take-up shaft.

When the belt is pulled from its rest position from the belt take-up shaft is actuated the device for detecting of the roll-up state the switch 4, which closes the circuit 2. At the same time, the facility delivers for detecting the winding direction, a signal which closes the switch 12, whereby the electromagnet 11 is energized and the clutch between motor 1 and the belt take-up shaft releases. Then the belt can be practically powerless from the belt take-up shaft subtracted from. If the particular connection design for the buckle, z. B.

Lock tongue, the belt inserted into the associated buckle and has been locked there, the device for detecting the winding direction opens the switch 12, while at the same time the switch 7 the other switch position occupies and thereby closes the circle of branches 10 again. Now the engine will only supplied with power via the connecting line 8; he delivers accordingly low torque and generates a low tensile force in the harness.

When loosening the lock tongue from the buckle is the same time Changeover switch 7 is actuated, and the second winding of the motor is again connected to the circuit 2 laid so that the belt at high speed on -the- belt winding shaft is rolled up and withdrawn into its storage position. This rest position is from the device for detecting the roll-up state detected, the switch 4 is opened and motor 1 is stopped.

In the embodiment according to FIG. 3, the motor 1 also has two separate ones or simultaneously controllable windings with associated connecting lines 8, 9. These windings, however, are preceded by a regulator 13, the task of which is to to control the engine 1 so that depending on the given operating conditions a constant tensile force is always generated in the belt. So this is the same Controller 13 changes in the tensile force of the belt, which arise from the fact that with constant, Torque delivered by motor 1 as a result of the uneven diameter of the belt roll on the belt take-up shaft changes the tensile force of the belt. The controller 13 receives its control signals from a device 14 that determines the diameter of the winding shaft recorded. Such a device is shown, for example, in FIG. 8b.

Instead of the switch 7 shown in Figure 2 are in the embodiment according to Figure 3, two separate, each associated with the connecting lines 8 and 9, respectively Switch 15 resp.

16 provided.

In addition, the engine 1 in the embodiment according to Figure 3 is designed so that that it can also work as a belt tensioner in the overload area. To do this is the engine 1 can be connected to a capacitor 17 connected to the circuit 2.

The control or the connection of the capacitor 17 to the motor 1 takes place via a timing element 18, which is based on signals from a network of AND gates 19 and OR gates 20, 21 is activated. That from the in the manner shown interconnected gates formed network processes signals of a vehicle-sensitive Blocking system 22, a handbrake 23, a footbrake 24 and possibly one Early warning device 25.

In addition to those already described in connection with FIGS. 1 or 2 Operating mode that also applies to Figure 3, the engine 1 in the embodiment according to Figure 3 also work as a belt tensioner in the event of danger, namely when the network the gate 19-21 supplies a corresponding signal to the timing element 18, which the capacitor 17 switches to the motor 1, which then with a correspondingly high Drive power winds the belt onto the belt take-up shaft, in order to Removed any slack in the belt and the person strapped to the associated vehicle seat pulls into the seat.

In Figures 4a-4d are different embodiments of devices for detecting the rolled-up state of a belt 26 is shown. These bodies are arranged in the area of an upper deflection fitting 27 for the belt 26.

In the embodiment according to FIG. 4a, this is assigned to this device Switch 4 is a photoelectric switch that operates on a color luminescent coating 28 of the belt webbing 26 responds. The coating 28 is arranged on the belt 26, that they are in the area of the photoelectric switch 4, if the available Length of the belt 26 is rolled onto the belt take-up shaft.

In the embodiment according to Figure 4b, the switch -4 is a leaf spring switch, its two spring tongues 29, 30 on the one hand on the deflection fitting 27 and on the other hand lie on the belt 26. The belt 26 has an electrically conductive coating 31, which like the color luminescent coating 28 of the embodiment according to FIG 4a is arranged in a belt section, which in the rest state of the belt 26 of the Spring tongue 30 can be detected.

In the embodiment according to FIG. 4c, the belt 26 has that described above Section a thickening 32, which actuates the switch 4, which in this case - a simple spring switch is.

In the embodiment according to FIG. 4d, the belt 26 has a corresponding one Section a ferromagnetic coating 33, which with a below the Deflection fitting 27 arranged permanent magnets 34 cooperates.

When the belt 2-6 is at rest, the permanent magnet 34 stops the with the ferromagnetic coating 33 provided portion of the belt 26, so that this section can operate a pin 35, which acts as a spring-tongue switch trained switch 4 belongs. If the in the area of the switch 4 on the belt 26 connected lock tongue 36 detected and thus the coated portion of the Permanent magnet 34 is withdrawn, the switch 4 supplies a switching signal.

The devices shown in FIGS. 5a-5h also work in a similar manner for detecting the reel-up state of the belt.

These facilities are each in the area of the belt winding shaft arranged and each sense the surface of a roll 37.-In the execution according to Figure 5a, a pivotably mounted two-armed lever 38 is provided, the one arm with a roller 39 runs off the roll 37 and the other arm over it a pin 35 actuates the switch 4.

In the embodiment according to FIG. 5b, the lever 38 is one-armed and carries on this arm both the roller 39 running on the winding 37 and the pin 35 to operate the switch 4.

In the embodiment according to FIG. 5c, the pivotably mounted one-armed one carries Lever 38 a slit diaphragm 4-0 through which a light source 41 emanating Light beam strike a photo element 42 and thereby trigger a switching signal can.

The embodiment according to FIG. 5d works similarly, with the proviso that that the slit diaphragm 40 is fixed and a switching signal with increasing or decreasing diameter of the coil 37 is generated.

The device shown in Figure 5f has a switch 4 two spring tongues 29, ~ 30, which lie next to one another on the winding 37. That Webbing 26 is on a corresponding portion with an electrically conductive Coating 31 is provided, via which the switch 4 thus formed is closed, when the section with the coating 31 is under the two spring tongues 29, 30 is located.

The embodiment shown in Figure 5h corresponds functionally the embodiment according to Figure 4a. The belt strap 26 has a at the corresponding point Color luminescent coating 28, which is in a photoelectric switch or

Photo element 42 triggers a switching signal.

Devices are shown in FIGS. 6a-6f. with whom the state of tension of the belt 26 can be detected.

The facilities shown are preferably in the range of Fittings, in particular deflection fittings -27, are arranged. To these facilities belongs to the switch 7 described at the beginning or equivalent embodiments, e.g. switches 15, 16.

In the embodiment according to Figure 6a is below the deflection fitting 27 pivotably mounted a lever -43 which actuates the switch 7 via a pin 44. In the rest position of the belt 26, the belt 26 or its lock tongue 36 acts the other side of the lever 43, which thereby moves the switch 7 into the switching position shown presses. If the belt 26 is removed, a switching signal is generated.

In the embodiment according to FIG. 6b, there is between the upper deflection fitting 27 and the coil 37 of the belt 26 is a lever system made up of two levers mounted in a joint 45 Roller levers 46, 47 are arranged. The roller lever 46 is on the one hand on a spring 48 and on the other hand supported on the winding 37, while the roller lever 47 is supported on the roller lever 46 via a spring 49. The roller lever 46 carries the switch 7 actuated by the roller lever 47 supported on the belt 26 when the tension of the belt changes.

In the embodiment according to FIG. 6c, only one is on the deflection fitting 27 mounted roller lever 46 is provided, which carries a slit screen 40. The slit diaphragm A light source 41 and a photo element 42 are assigned to 40. The tensioned belt 26 is guided in the area of the slit diaphragm 40 and covers the slit diaphragm. if the tension of the belt 26 decreases, the slit screen 40 is free, and it is formed a switching signal.

In the embodiment according to FIG. 6d, the belt 26 is attached to the deflection fitting 27 via a substantially vertically displaceable and supported on a spring 50 Tab 51 out. The free end of the tab 51 is acted upon by a pin 44 the switch 7. When the tension of the belt 26 is released, the flap 51 of the spring 50 is raised and the changeover switch 7 is actuated, so that a switching signal arises.

The embodiment according to FIG. 6e works similarly, with the difference that that the deflection fitting 27 is suspended from a spring 52. The switch 7 actuating pin 44 is arranged on deflection fitting 27. The deflection fitting 27 takes the one indicated by the dash-dotted line 53 when the belt is tension-free Position and when the belt is tensioned that indicated by the dash-dotted line 54 Lay a.

The embodiment according to Figure 6f shows an end fitting 55 for the belt 26 arranged device for detection the state of tension of the belt. The end fitting 26 can be moved in height and is supported on the spring 52. The pin 44 fastened to the end fitting 55 acts on the switch 7.

In the embodiments according to FIGS. 7a-7c, the voltage of the Belt determined from the respective position of the movably mounted belt lock 56. In the embodiment according to Figure 7a, the belt buckle 56 is about a substantially horizontal Axis 57 is pivotably mounted and supported on a spring 58. The switch 7 carries the pin 44 on a spring tongue, which is inserted into an associated recess 59 of the Belt lock 56 engages. If the buckle 56 is under the action of the tensile force of the belt is pivoted into the inclined position indicated by a dash-dotted line 60, then the pin 44 is lifted out of the recess 59 and the changeover switch 7 actuated.

In the embodiment according to FIG. 7b, the belt lock 56 is in the direction of the Axis 57 pivotably arranged and supported on the spring 58, so that the switch 7 is actuated via the pin 44 when the buckle 56 is under the action of Tensile force of the belt in the inclined position indicated by the dash-dotted line 60 got.

In the embodiment according to Figure 7c, the buckle 56 is from a resiliently flexible anchoring part 61, e.g. B. a wire held. In unencumbered In the state of the belt buckle 56, the anchoring part 61 is in front of a stationary one Orifice plate 62 to which a light source 41 and a photo element 42 are assigned. if the belt closed 56 or its anchoring part 6-1 by the dash-dotted line Line 60 assumes the inclined position indicated, the light beam hits the light ball 41 on the photo element 42 and triggers a switching signal.

Tn Figures 8a-8c devices are shown that the winding direction of the belt. In the embodiment according to FIG. 8a, a is pivotable Bearing lever 63 pressed by a spring 64 onto the surface of the roll 37. The lever 63 carries the pin 44 for actuating the switch 12. When the belt is rolled up the lever 63 assumes the position shown in the illustration.

If the belt is unrolled, then the winding 37 rotates in the direction of the arrow 65, and the lever 63 takes the indicated by the dash-dotted line 66 Position a, where he actuates the switch 12, which a corresponding switching signal gives away.

In the embodiment shown in FIG. 8b, the belt take-up shaft is attached 67, a threaded section 68 is connected, on which a nut 69 is guided in a rotationally fixed manner is to which an electrical resistor 70 is assigned. The resistance 70 can be a ohmic, inductive or capacitive resistance. When the belt take-up shaft rotates 67, the nut 69 is moved to or fro in the direction of the double arrow 71. Included the resistance 70 is changed accordingly, and the change in resistance becomes a switching signal derived. At the same time, the change in resistance can also a may for the change in the diameter of the coil 37 can be derived.

In the embodiment according to FIG. 8c, the diameter of the roll is 37 measured optically or with ultrasound. For this purpose, a transmitter 72 is provided, whose Signals reflected from the roll and picked up by a receiver 73.

The output of the receiver 73 forms a measure of the diameter of the Winding 37 and thus for the rolling state of the belt.

In Figures 9a and 9b are exemplary embodiments of clutches shown, the between motor 1 and belt take-up shaft 67, optionally below further interposition of a reduction gear, not shown, arranged In the embodiment according to FIG. 9a, one coupling half 74 is connected to a gear stage 75. The coupling half 74 has a toothing 76 to which a toothing of the other coupling half 77 is assigned. the Coupling half 77 is axially displaceable against the pressure of a spring 78. To postpone an angle lever 79 is used, one arm of which is inserted into a circumferential groove 80 of the coupling half 77 engages and the other arm of which can be acted upon by the electromagnet 11. In the functional position shown - the clutch is closed, so that the belt can be wound up by the motor 1. If the electromagnet 11 is actuated, then the bell crank 79 is attracted by the electromagnet 11 and the clutch is opened.

In the embodiment according to FIG. 9b, the gear stage 75 forms itself a coupling half that has a coupling disc 81 with the other coupling half 77 can be coupled.

This other coupling half 77 has a pot magnet 82 with a coil 83, which functionally corresponds to the electromagnet 11 of the embodiment according to FIG. 9a.

Those disclosed in the description, the claims and the drawing Features of the invention can be used individually or in any combination among themselves for the implementation of the invention in its various embodiments be essential.

Blank page

Claims (26)

Claims 1. Automatic belt retractor for seat belts, in particular in motor vehicles, with a driving force in the winding direction acted upon Gurtaufwickelwelle and preferably with a belt and / or vehicle-sensitive locking system, characterized by a drive for the Belt take-up shaft (67) installed electric motor (1), one of the operating status the belt (26) and / or the vehicle detecting switching device assigned is. 2. Belt retractor according to claim 1, characterized by a direct current motor (1) as a drive for the Gurtaufwickelwele (67). 3. Belt retractor according to claim 1 or 2, characterized by a Reduction gear (75) between Motor (1) and belt take-up shaft (67). 4. Belt retractor according to claim 1, 2 or 3, characterized in that that between the motor (1) and the belt take-up shaft (67) a clutch '(74, 77) is switched on is. 5. Belt retractor according to claim 4, characterized in that the Coupling is designed as a clutch that releases the torque as a function of the torque. 6. Belt retractor according to claim 4, characterized in that the Coupling designed as a clutch (74, 77) that can be actuated by the switching device is. 7. Belt retractor according to claim 2, characterized in that the DC motor (1) two separately or simultaneously controllable windings (8, 9). 8. Belt retractor according to claim 7, characterized by the same number of turns of the two windings. 9. Belt retractor according to claim 7, characterized by unequal Number of turns of the two windings. 10. Belt retractor according to at least one of the preceding claims, characterized in that the switching device has at least one voltage state the belt detecting device with switch (7). 11. Belt retractor according to claim 10, characterized in that the Device for detecting the state of tension in the area of when the Belt (26) pivotable belt section is arranged. 12. Belt retractor according to claim 10, characterized by a resilient supported deflection fitting (27). 13. Belt retractor according to claim 10, characterized by a resilient supported belt buckle (56). 14. Belt retractor according to at least one of the preceding claims, characterized in that the switching device has at least one of the rolled-up state the belt (26) detecting device with switch (4). 15. Belt retractor according to claim 14, characterized in that the Means for detecting the reeling condition as the diameter of the belt roll sensing button (38; 29, 30; 42; 72, 73) is formed. 16. Belt retractor according to claim 14, characterized in that the Device for detecting the reeling condition as mechanical or electromagnetic detectable mark (28, 31, 32) is designed on the belt (26). 17. Belt retractor according to at least one of the preceding claims, characterized in that the switching device with mechanical switches (4, 7, 12) is equipped. 18. Belt retractor according to at least one of the preceding claims, characterized in that the switching device has photoelectric switches (42) is equipped. 19. Belt retractor according to at least one of the preceding claims, characterized by a device for Detecting the winding direction of the belt strap (26) on the belt take-up shaft (67) with switch (1.2). 20. Belt retractor according to claim 19, characterized in that the Device for detecting the winding direction as a pivotably mounted lever (63) is designed, the free end of which is resilient with frictional contact on the belt roll (26, 37) is present. 21. Belt retractor according to claim 19, characterized in that the Device for detecting the winding direction as on a threaded section (68) the belt take-up shaft (67) non-rotatably held nut (69) is formed, the to measure the displacement an ohmic, inductive or capacitive resistance - (70) is assigned. 22. Belt retractor according to claim 19, characterized by an optical or device (72, 73) operating with ultrasound for detecting the winding direction. 23. Belt retractor according to at least one of the preceding claims, characterized in that the operating state of the belt (26) is detected Switching device on the motor voltage according to the respective winding diameter setting controller (13) is assigned. 24. Belt retractor according to at least one of the preceding. Claims, characterized in that the engine (1) for operation is designed as a belt tensioner and to a charged via the switching device Capacitor (17) can be connected. 25. Belt retractor according to claim 24, characterized in that the Switching device a network (19, 20, 21) for the logical combination of signals the locking systems (22), the vehicle brakes (23, 24) and possibly one Has early warning device (25). 26. Belt retractor according to claim 25, characterized by an between the network (19, 20, 21) and the capacitor (17) switched timing element (18). description