Belt retractor unit and vehicle having such a belt retractor unit

Abstract

The present invention relates to a belt retractor unit having a housing (10), a belt reel (20) rotatably mounted within the housing (10), a blocking unit for blocking the belt reel relative to the housing, the blocking unit having an actuator unit (40) having an electromagnet (42), and a control device (50) for controlling the electromagnet (42), the control device (50) having a power input (55), a power output (56) connected to the electromagnet (42), at least one signal input (57) for receiving a control signal, and / or a sensor unit (52) for generating a control signal, and a control device (50) having at least a first active switching state and a passive switching state, in which in the first active switching state a current flows between the power output (56) and the electromagnet (42), the current intensity being greater than in the passive switching state, the control device (50) having at least one DC / DC converter (60) operating as a constant current source between the power input and the power output, whereby the current intensity in the first active switching state has a predetermined first value (I1) independent of the voltage applied to the power input.

Description

[Technical Field]

[0001] The invention relates to a belt retractor unit according to the preamble of claim 1 and to a vehicle comprising such a belt retractor unit according to claim 10. Summary of the Invention [Problem to be solved by the invention]

[0002] Not only all modern passenger cars, but also most trucks, buses, and the like, have seat belt systems. Such safety belt systems always include a belt retractor unit, which includes a belt retractor having a housing and a belt reel rotatably mounted within the housing. A portion of the safety belt system strap is wound around the belt reel, and a user can unwind the safety belt system strap from the belt reel against the force of a return spring acting between the belt reel and the housing. A blocking device is also provided, which has a release state in which the belt spool is not blocked relative to the housing and a blocked state in which the belt spool is blocked relative to the housing. The blocking device typically has two independent sensors: a belt-sensing sensor that senses belt reel rotation, and a vehicle-sensing sensor that senses vehicle position and / or vehicle acceleration (particularly negative vehicle acceleration, i.e., deceleration). Under normal driving conditions, i.e., when the strap is not being stretched too quickly and the vehicle is not in an abnormal position or undergoing abnormal acceleration, the blocking device is in its unblocked state, allowing the user to stretch the strap and allowing relatively free movement. However, if, for example, the strap is stretched too quickly and / or the vehicle decelerates too quickly, the blocking device will become blocked.

[0003] Currently, blocking devices are almost entirely mechanically designed, which means that the complete blocking device (including the sensor) is rigidly connected to the housing of the belt retractor. However, this rigid connection of the entire blocking device to the housing has drawbacks, especially when the belt retractor unit is fixed to the vehicle seat, especially the backrest, since the position of the belt retractor, and therefore the position of the vehicle sensing sensor, can change relative to the vehicle.

[0004] For this purpose, fully or partially electrically operated belt retractor units are known, whose blocking device includes a blocking unit connected to a housing having an electromagnet and a control device for controlling the electromagnet. The electromagnet is part of an electrically controllable actuator unit, and the state of the actuator unit (in particular, no current or current flowing) determines the state of the blocking unit (whether the belt coil is rotatable or blocked). Typically, the blocking unit also includes a return element (usually in the form of a spring) that opposes the electromagnet. This reset element may also be part of the actuator unit. For safety reasons (fail-safe), the no-current state is typically a blocked state, and the current-flowing state is typically an unlocked state. Therefore, a control device driving an actuator unit having a power input connected to the vehicle electrical system and a power output connected to the electromagnet has a passive switching state in which the power supply from the power input to the power output is interrupted, and an active switching state in which the power input is connected to the power output, thereby allowing current to flow through the electromagnet. This control device is generally exclusively electrically coupled to the blocking unit and can be located anywhere in the vehicle, in particular so that it does not move with the seat back. A typical belt retractor unit having such a blocking unit and such a control device is described, for example, in GB Patent No. 2398824B. Such electrically operated belt retractor units have other advantages, as they offer more possibilities for controlling the state (blocked / unblocked) of the belt retractor unit.

[0005] A disadvantage of such a typical belt retractor unit is, of course, that it increases the vehicle's power consumption compared to a purely mechanically operated belt retractor unit. This is all the more true because it is typically preferred, or even necessary, for the belt retractor unit to be locked when in a current-free state, i.e., when no current is flowing through the electromagnet. This means that during normal driving operation, when the belt retractor unit is naturally in its unlocked state, current flows through the electromagnet, thus creating a permanent additional electrical consumer while the vehicle is operating. Naturally, this is already undesirable in a conventional combustion engine vehicle, as it permanently increases the load on the alternator, which in turn increases the vehicle's overall energy consumption. Naturally, this problem is exacerbated in the case of a fully or partially electric vehicle, as the increased power consumption adversely affects the range of electric modes.

[0006] Based on this, it is an object of the present invention to improve a typical belt retractor unit so as to reduce power consumption.

[0007] This problem is solved by a belt retractor unit having the features of claim 1. A vehicle having such a belt retractor unit is disclosed in claim 10.

[0008] The force that an electromagnet exerts on a magnetic element, for a given geometry, depends only on the strength of the current flowing through the electromagnet (i.e., its windings). Because the windings of such electromagnets are essentially ohmic, the current strength depends linearly on the applied voltage. To maintain the blocking unit in its state when the electromagnet is energized by a storm, the electromagnet must exert a minimum force on the element to which it is applied, which means that a minimum amperage of current must be guaranteed to flow through the electromagnet. If, as in the prior art, the vehicle's onboard voltage is simply applied to the electromagnet, the electromagnet must be designed to ensure that a holding force is still provided even when the onboard voltage reaches its minimum allowable value. It should be noted that the vehicle's onboard voltage can vary over a relatively wide range, particularly depending on the battery's state of charge. However, this means that when the onboard voltage is in its normal or upper range, more current than necessary flows through the solenoid, consuming unnecessary power.

[0009] Thus, according to the invention, the control device has at least one DC / DC converter between its power input and its power output, operating as a constant current source, so that the current intensity in the first active switching state has a predetermined first value that is independent of the voltage applied to the power input. Such DC / DC converters operating as constant current sources are widely used in technology, have high efficiency and are also very cheap in the power range relevant here.

[0010] By using a DC-DC converter that acts as a constant current source, the electromagnets of the actuator units receive only the current they "need", thus saving power compared to the prior art.

[0011] Typically, the first value of the current is between 50 mA and 500 mA.

[0012] In a particularly preferred embodiment, the control device has two active switching states instead of one, and the current intensity in the second active switching state has a higher value than in the first active switching state. Preferably, the current intensity also has a second predetermined value in this second active switching state, which is greater than the first value. This particularly preferred embodiment of the present invention is based on the following considerations: when the control device switches from a passive switching state to an active switching state, the electromagnet of the actuator unit moves the movable element from the first position to the second position. In principle, this movement means unlocking the blocking unit. The blocking unit then typically remains in the unlocked position for a relatively long time, i.e., the element movable by the electromagnet remains unmoved but is held by the electromagnet. It has been found that the force that the electromagnet must apply to move the element driven by it is substantially greater than the force that the electromagnet must apply to hold the element in the "held by the electromagnet" position. Naturally, according to the above, this also means that the current required to change state is greater than the current required to maintain the state. Naturally, the "holding state" typically lasts much longer than the actual state, so if the current through the electromagnet in the holding state is smaller than during the switching operation, a large amount of energy can be saved. To achieve precisely defined switching behavior and further minimize energy consumption and waste, the current strength preferably also has a defined value in the second active switching state, which is independent of the voltage applied to the power input. This means that the current through the electromagnet in this second active switching state is also supplied by the DC-DC converter. Here, a switchable DC-DC converter can be used to realize the two active switching states.However, since the first active switching state typically exists for a much longer period than the second active switching state, it is not absolutely necessary for the current flowing through the electromagnet in the second active switching state to be provided by a DC-DC converter in order to save energy compared to the prior art. The circuit must be selected so that the current strength in the second active switching state is sufficient in all cases (i.e., even when the voltage of the on-board power supply is low) to ensure the movement of the element driven by the electromagnet.

[0013] Further advantages result from the design of the belt retractor unit according to the present invention.

[0014] The control current of the solenoid naturally requires a corresponding control voltage. With a DC-DC converter, the voltage at the solenoid is independent of the vehicle battery voltage. This means that any fluctuations in the vehicle battery can be compensated for.

[0015] Energy savings can also be achieved using a PWM controller, but this typically has the drawback of generating EMC related interference. However, the use of DC current in accordance with the present invention minimizes any EMC related interference since no PWM frequency is generated.

[0016] As already mentioned, the magnetic field strength of an electromagnet depends mainly on the current, so a DC-DC converter can also be used to compensate for temperature dependence and ageing effects, as a constant current always flows through the electromagnet. [Brief explanation of the drawings]

[0017] The present invention will now be described in more detail by means of preferred embodiments with reference to the figures, in which: [Figure 1]FIG. 1 is a schematic diagram of a belt retractor unit, the belt retractor of which is shown in a schematic side view, the control device in its passive switching state, and the belt retractor in its locked state. [Figure 2] FIG. 2 is a schematic top view of the belt retractor shown in FIG. [Figure 3] FIG. 3 shows the control device shown in FIG. 1 with the control device in an active switching state and the belt retractor in an unlocked state. [Figure 4a] FIG. 4a shows a more detailed view of the embodiment of the control device simplified in FIGS. 1 and 3, in a first active switching state. [Figure 4b] FIG. 4b shows the control device of FIG. 4a in a second active switching state. [Figure 4c] FIG. 4c shows the control device of FIGS. 4a and 4b in a passive switching state. [Figure 5] FIG. 5 shows a typical time-current diagram of the current through the electromagnet of the blocking unit. DETAILED DESCRIPTION OF THE INVENTION

[0018] With reference to Figures 1 and 2, the essential features of the belt retractor unit according to the present invention will first be described. It should be noted that the representations are very schematic and represent only the basic principles of the present invention. The belt retractor unit can be considered to include a belt retractor 10 and a control device 50. Here, the control device 50 may be directly connected to the housing of the belt retractor 10, but this is not necessary, and therefore the control device 50 is shown separated from the housing in Figures 1 and 3. Naturally, the control device and the belt retractor must be electrically connected to each other.

[0019] In the following, conduits are shown only diagrammatically (along with the output and return conductors) where power lines are shown as solid lines and signal lines are shown as lines with a "dash-dotted" pattern.

[0020] The belt retractor 10 comprises, as is conventional, a housing 12, a belt reel 20 rotatably supported in the housing and around which a portion of the strap 5 is wound, and a blocking unit for blocking the belt reel 20 in the housing 12. In the illustrated embodiment, the housing 12 has two housing plates 14a, 14b connected by a connecting bolt 16, but this should be understood as an example only. In principle, as is also shown here, the blocking unit has a locking wheel 22 connected in a rotatably fixed manner to the belt reel 20. A pawl 24a is further provided which locks the locking wheel 22, and thus the belt spool 20, to the housing 12 in the locked state (FIG. 1), but not in the released state (FIG. 3).

[0021] Importantly, the position of the pawl 24a is controlled directly (as shown) or indirectly by the actuator assembly 40, which includes the electromagnet 42. In the illustrated embodiment, this effect is achieved by the fact that the actuator unit 40 includes, in addition to the electromagnet 42, a plunger 44 driven by the electromagnet, which acts on the lever 24 carrying the pawl 24a. When a sufficiently strong current flows through the electromagnet, it pushes the plunger 44 outward. However, as already mentioned, it should be noted that this configuration should be understood only as an example. Essentially, the blocking unit includes an electromagnet, and the actuator unit controls the blocking unit depending on the current flowing through the magnet. This also typically means that a spring—in this case, a tension spring 30, or another elastic element—is provided that uniquely defines the state of the blocking unit when the electromagnet 42 of the actuator unit 40 is current-free and therefore does not exert any force on the plunger driven by it. This current-free state, as also shown in the figure, is the locked state.

[0022] Such electrically controlled blocking units with electromagnets are known in the prior art, therefore the present invention also relates to the control of the electromagnets, i.e. the control device 50 only.

[0023] As mentioned above, the essence of the present invention is that the control device 50 includes at least one DC-DC converter that functions as a constant current source, and in the first active switching state of the control device 50, only a current sufficient to maintain the desired state (i.e., the unlocked state) is supplied to the solenoid. As also explained above, the control device preferably has three switching states: a first active switching state, a second active switching state, and a passive switching state. In the passive switching state, the control device does not supply current to the electromagnet; in the first active switching state, the control device supplies current to the electromagnet, the current intensity of which has a predetermined first value I1; and in the second active switching state, the control device supplies current to the electromagnet, the current intensity of which has a predetermined second value I2. Possible schematic circuit diagrams of such a control device are shown in Figures 4a-4c and are described below.

[0024] The control unit has a power input 55 connected to the vehicle's electrical system and a power output 56 connected to the electromagnet 42 of the actuator unit 40. Furthermore, the control device has a signal input 57 and / or a dedicated sensor unit 52 (in the embodiment shown, both are present, but this is not necessary), a switchable DC-DC converter 60, and a logic unit 54. The sensor unit 52 can in particular be an acceleration sensor, which outputs a signal to the logic unit 54 when a predetermined acceleration value is exceeded or fallen below. Depending on the received signal, this logic unit 54 controls the switchable DC-DC converter 60, which can supply three predetermined current levels to the electromagnet 42 via the power output 56, starting from the on-board voltage supplied to the electromagnet via the power input 55. In the illustrated embodiment, the DC-DC converter 60 includes a first converter unit 61 that generates a predetermined first current intensity having a first value I1, a second converter unit 62 that generates a predetermined second current intensity having a second value I2, and a selector switch 64 with three positions, where I2 > I1. The selector switch 64 is controlled by the logic unit 54. In the switching state of the selector switch 64 shown in FIG. 4a, the first transducer unit 61 supplies current to the electromagnet. In the switching state shown in FIG. 4b, the second transducer unit 62 supplies current. In the switching state shown in FIG. 4b, the electromagnet is currentless. The switching states of the control unit correspond to the switching states of the selector switch, at least when the on-board voltage is applied to the power input 55.

[0025] FIG. 5 illustrates the operation of logic unit 54 based on the current output.

[0026] When the vehicle is not in operation, the vehicle's power supply is normally switched off, meaning that no power is supplied to the electromagnet, and the belt retractor is therefore in the state shown in FIG. 1. Alternatively or additionally, the selector switch may be in the switching state shown in FIG. 4c. According to the definition selected here, the control device is in its passive switching state. When the vehicle is then operated, the logic unit 54 controls the selector switch 64 at time t0 (e.g., after the system has been tested) to the switching state shown in FIG. 4b, so that a current of intensity I2 flows through the electromagnet 42, generating a force sufficient to move the plunger 44 and thus place the blocking unit in an unlocked state. After a predetermined time interval Δt (which may be less than one second) has elapsed, the logic unit 54 now controls the selector switch 64 to change to the switching state shown in FIG. 4a, causing the first converter unit 61 to supply a current of magnitude I1 to the electromagnet. This current I1 is sufficient to keep the blocking unit in its unlocked state. If now a signal indicating an accident is supplied to the logic unit 54 via the signal input 57 or by the sensor unit 54, the logic unit 54 controls the selector switch 64 so that it changes to the open state (Fig. 4c), i.e. the current to the electromagnet 42 is interrupted and the belt retractor changes to the state shown in Fig. 1. If now the signal changes again and there is no longer an accident or dangerous situation, what has just been described is repeated, i.e. first a current of intensity I2 flows through the electromagnet for a time interval Δt, and after this time interval has elapsed a current of intensity I1 flows.

[0027] It is therefore essential that during the transition from the blocked to the unblocked state, the stronger current always flows through the solenoid first, followed by the weaker current flowing through the solenoid in the subsequent holding state.

[0028] This results in an overall significantly reduced power consumption compared to the prior art, which is a major advantage, especially for vehicles that are fully or partly electric. [Explanation of symbols]

[0029] 10 Belt retractor 12 Housing 14a, b Housing plate 16 Connection bolt 18 Holder for spring and actuator unit 20 Belt Reel 22 Locking Wheel 24 Lever 24a Claw 30 Tension spring 40 Actuator Unit 42 Electromagnet 44 Plunger 50 Control device 52 Sensor Unit 54 logical units 55 Power input section 56 Power output section 57 Signal input section 60 Switchable DC-DC Converter 61 First transducer unit 62 Second transducer unit 64 Selector switch

Claims

1. A belt retractor unit, a housing (10); a belt reel (20) rotatably mounted within the housing (10); a locking unit for locking the belt reel to the housing, the locking unit having an actuator unit (40) having an electromagnet (42); a control device (50) for controlling the electromagnet (42), the control device (50) comprising a power input (55), a power output (56) connected to the electromagnet (42), at least one signal input (57) for receiving a control signal, and / or a sensor unit (52) for generating a control signal, the control device (50) having at least one first active switching state and one passive switching state, in which in the first active switching state a current flows between the power output (56) and the electromagnet (42), the current intensity of which is greater than in the passive switching state; and 1. A belt retractor unit, comprising: a control device (50) having at least one DC-DC converter (60) acting as a constant current source between the power input and the power output, whereby the current intensity in the first active switching state has a predetermined first value (I1) independent of the voltage applied to the power input.

2. 2. The belt retractor unit according to claim 1, wherein the first value (I1) is between 50 mA and 500 mA.

3. 3. A belt retractor unit according to claim 1 or 2, characterized in that the control device (50) has a second active switching state in which the current intensity is greater than that of the first active switching state.

4. 4. The belt retractor unit according to claim 3, characterized in that in the second active switching state, the current intensity has a predetermined second value (I2) that is independent of the voltage applied to the power input (55) and is greater than the first value.

5. 5. A belt retractor unit according to any one of claims 1 to 4, characterized in that the belt reel (20) is locked relative to the housing (12) when the control device (50) is in the passive switching state.

6. 4. The belt retractor unit according to claim 3, characterized in that the control device (50) switches from the passive switching state first to the second active switching state and then to the first active switching state when the belt reel (20) is unlocked.

7. 7. A belt retractor unit according to any one of claims 1 to 6, characterized in that the current intensity between the power output (56) and the electromagnet (42) in the passive switching state is essentially zero.

8. A vehicle equipped with an electric drive having a belt retractor unit according to any one of claims 1 to 7.

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