DE19614161A1 - Transmitter for output and communication data e.g. for motor vehicle airbag restraint system - Google Patents

Abstract

The primary (26) and secondary coil (30) are positioned round a centre axis (14), with secondary coil rotatable and forming an annular gap with the primary coil such that the two coils are inductively coupled. There are two signal generators, each with a different frequency. One of the two signals is applied to a transistor for the control of the current flux through the primary, thus inducing a signal in the secondary with first or second frequency to the secondary is coupled a capacitor, charged by the induced signal of the first frequency. The capacitor is discharged in dependence on the signal with the second frequency.

Description

This invention relates to an apparatus for transmitting Performance and communication data over a ring-shaped Gap away without any direct electrical connection.

Background of the Invention

Vehicles with inflatable restraint devices ("airbags") are equipped in the shell of a steering wheel use an electrically operated pump direction ("inflation device") for deploying the airbag in the event of a violent impact. The detection of one Impacts are generally accelerated brought about knife, which fastened in the passenger compartment is. The accelerometer produces an output, wel cher is processed by an airbag control device. If the control device determines that the impact is sufficiently violent to deploy an airbag justify a suitable trigger signal to the on expanded device issued.

Communication of the trigger signal to the inflation device device requires an electrical connection means over a annular gap in the steering system away by a Steering column and a steering shaft rotatably carried therein is defined. Typically this is electrical Connection by means of a clock spring type device been led.

A typical clockspring type device according to the state of the art Technology includes a stationary outer housing that attaches to the Steering column is coupled to an inner housing that is rotatable carried by the outer casing and in a driving relation  hung is coupled to the steering shaft, and an electric Conductor carried by the stationary case and loose with a lot of turns around the inner case is wrapped. One end of the ladder is over one electrical conductor with an airbag control device connected and its other end is via an electrical Connector connected to the inflator. If the Steering shaft is turned in one direction, the head wrapped closer to the inner case, and when in the other way round, the conductor is loosened and unwound away from the inner case.

To add steering surface controls (steering pad controls) for controlling such vehicle systems, like the radio, the horn, the wipers, the lights device, heating and air conditioning the facility contains multiple leaders.

Although clock spring type devices in their electrical Work are satisfactory, they have certain mechani Disadvantages, for example: (i) incorrect installation during the assembly or maintenance of a steering system can lead to the conductor cable being wound too tightly what is not enough scope for a full rotation of the Steering wheel allowed and damage to the connector calls when a full turn occurs and (ii) distances between the inner and outer housings that are necessary are to rotate the housing with respect to each other allow, can become a clatter or squeak Noise on bumpy roads or while turning the Guide the steering wheel.

Try to move the inner and outer cases into position lock to prevent excessive tightening of the connector cable assembly or maintenance of the steering system  prevent using an anti-rotation effect included the pen, which at the conclusion of the Together menbaus is removed. However, this increases the overall cost of the system and the complexity of its installation.

There is a desire to have a device for transmitting Performance and communication data over the annular gap to get rid of that by a steering column and a steering wave is defined without the need for any direct electrical connection, eliminating the disadvantages of Einrich Clocks of the clock spring type overcome according to the prior art will.

Summary of the invention

The invention relates to a device for transmitting Performance and communication data over a ring-shaped Gap as if through the steering column and the steering shaft of a vehicle without any direct electri connection. The performance is used to inflate device to operate in the shell of the steering wheel arranged to deploy the inflatable restraint is. The communication data becomes a diagnostic over watch the inflation device and to enable actuation supply of vehicle systems through steering surface controls used. A device according to the invention is through characterized in the features specified in claim 1.

The invention preferably provides a primary coil winding ment, which is mechanically coupled to the steering column, and a secondary coil winding that mechanically connects to the steering shaft coupled and in line with the primary coils winding is positioned so that the two despite one Rotation of the steering shaft remain inductively coupled.  

Two oscillators generate electrical signals with passing tuned frequencies. In the preferred embodiment, he the one oscillator generates a signal with a frequency of 96 kHz while the other is a signal with a frequency of 32.7 KHz generated. An electronic switch sets selectively one of the two signals to the transistor to control the Current flow through the primary coil winding, causing a Signal in the secondary coil winding with a match the frequency is induced. The electronic switch causes the 32.7 KHz depending on a violent Impact event are created, whereby it otherwise the 96 KHz Applies signal.

A capacitor is electrical with the secondary coil winding tion and is dependent on a 96 KHz-Si gnal charged, which induces in the secondary coil winding becomes. Once charged, the capacitor is ready to actuate the inflation device.

The inflation device is actuated during unloading of the condenser depending on the inflation device speed of a 32.7 kHz signal that is in the secondary len winding is induced.

The communication data transmission is by means of inductive Impedance brought about. Each steering surface control button is connected to a multiplexer, which is a serial Output generated with a stream of serial codes, where each code is a binary word with a predetermined number of Bits is. Each control button has a unique one serial code that assigned each of its operating states is shown (e.g. "on" and "off"). A multiplexer transmits the serial codes to a modulator, which measures the impedance (Load) the secondary coil winding between one of the two Impedance values vary. Because the two windings are inductive  coupled, this impedance is in the secondary coils winding reflected back to the primary coil winding, whereby the amplitude of the voltage is varied, which over the primary coil winding is developed. A demodulator, which is coupled to the primary coil winding converts the varying amplitudes back into serial codes. After that the serial codes are demultiplexed to binary outputs according to the current state of each control to generate a button.

The 96 KHz signal carries both the power (capacitor la transmission) and communication data (serial code) transmission This causes the 32.7 KHz signal to operate the Airbag inflation device controls (discharge of the condensate tors).

Brief description of the drawing

The invention is exemplified below with reference to Drawing described; in this shows:

System FIG. 1 is an exploded perspective view of a steering, including the apparatus of the invention,

Fig. 2A-B detailed diagrams of the electronic circuitry of the preferred embodiment of the invention, and

Figures 3A-B are block diagrams of a general arrangement of the electronic circuit depicted in Figures 2A-B.

Detailed description of the preferred embodiments

In the following description, similar parts or Structures used in the figures with the same Chen reference numerals and where such parts and Structures previously described with respect to an earlier figure the description will not be repeated.

With reference to the drawings and particularly to FIG. 1, a basic vehicle steering system includes (i) a steering column 10 attached to the vehicle chassis, (ii) a steering shaft 12 rotatable within the steering column 10 along a central axis 14 is carried, with the steering column 10 and the steering shaft 12 having an annular gap 11 therebetween, and (iii) a steering wheel 16 which is coupled to the steering shaft 12 for its rotation.

The steering wheel 16 comprises (i) an inflatable restraining means 18 , which is arranged in the shell 15 of the steering wheel 16 , (ii) an electrically operated deployment device ("on inflation device") 20 and (iii) multiple control devices 22 , such as push buttons and switches 22 for Controlling such vehicle systems as the radio; the horn, the windshield wiper, the lighting, the heating and the air conditioning.

The device according to the invention comprises (i) a primary coil winding 26 which is mechanically coupled to the steering column 10 and electrically to various vehicle systems 34 , 36 and 38 via an electronic circuit on the primary side 28 , and (ii) a secondary coil winding 30 which mechanically with the steering shaft 12 and electrically with the inflating device 20 and steering surface control elements 22 via an electronic circuit on the secondary side 32 is coupled. The primary and secondary coil windings 26 and 30 are positioned coaxially and in the annular gap 11 relative to one another so that they are inductively coupled, and remain so, despite rotation of the secondary coil winding 30 by the steering shaft 12th

By means of the device of the invention, power and communication data are transmitted inductively across the annular gap 11 between the steering column 10 and the steering shaft 12 by means of the primary and secondary coil windings 26 and 30 . Power is transmitted to allow inflation device 20 to deploy and actuate steering surface controls 22 . Communication data are transmitted to enable diagnostic monitoring of the inflation device 20 and to monitor the actuation of the steering surface control elements 22 .

FIGS. 2A-B illustrate detailed circuit diagrams of the preferred embodiment of the electronics on the primary and secondary pages 28 and 32 according to the invention. In order to facilitate understanding of their effect, block are diagrams of the general circuit arrangement in Fig. 3A-B shown.

A block diagram of the general circuitry of the electronic circuit on primary 28 is shown in FIG. 3A. Referring to FIG. 3A, two oscillator circuits 50 and 52 are provided for generating a 32.7 KHz or 96 KHz alternating current signal. The 96 KHz signal is used for power and communication data transmission, while the 32.7 KHz signal is used to initialize the deployment of the airbag. The oscillators 50 and 52 are energized by a low voltage source 54 with typically +5 V DC. The two signals are coupled to a single-pole switch (SPDT) 56 , the output of which is connected to the gate of a transistor 58 . The position of switch 56 controls which of the two signals actuates transistor 58 . When the 32.7 KHz signal is coupled to the gate, transistor 58 will "turn on" (conduct current) and "turn off" at a frequency of 32.7 KHz. Similarly, when the 96 KHz signal is coupled to the gate, transistor 58 will "turn on" and "turn off" at a frequency of 96 KHz, allowing current to flow through the primary coil winding 26 at a corresponding frequency flows.

In general, the normally closed position of switch 56 is such that the 96 KHz signal is coupled to the gate of transistor 58 . Actuation of the switch 56 , however, couples the 32.7 KHz signal to the gate of the transistor 58 . Actuation of the switch 56 is controlled by an airbag deployment signal received from an airbag control device 34 via signal line 60 .

The operation of transistor 58 controls the flow of current through primary coil winding 26 . When transistor 58 is "on", the low voltage side of primary coil winding 26 is closed to ground, allowing current to flow through primary coil winding 26 from a high voltage source 62 (e.g., +8 Vdc) to ground, thereby causing a Magnetic field is generated, which inductively couples the primary and secondary coil windings 26 and 30 . When the transistor 58 is "turned off", the low voltage side of the primary coil winding 26 is "switched open", whereby the current is interrupted and the magnetic field breaks down. Which of the two signals is coupled to the gate will determine the operating frequency of transistor 58 and thereby the current flow through primary coil winding 26 and ultimately the rise and breakdown of an inductively coupled magnetic field.

A demodulator 64 and a demultiplexer 66 are coupled to the low voltage side of the primary coil winding 26 . They cause communication data to be decoded which is transmitted from the secondary coil winding 30 to the primary coil winding 26 . A more detailed description of their effect is given below.

A block diagram of the general circuitry of the electronic circuit on secondary 32 is shown in FIG. 3B. Referring to Fig. 3B, two receptions and seminars are gerschaltkreise 70 and 72 coupled to a secondary coil winding 30. Each circuit 70 and 72 is "tuned" to a specific frequency for receiving either the 32.7 KHz or the 96 KHz signal, which are transmitted inductively across the ring-shaped gap 11 . Optical isolators 80 and 82 are provided for isolating the 32.7 and 96 kHz receiver circuits 70 and 72 from each other and from the rest of the electronics on the secondary side 32 .

An induced 96 KHz signal in the secondary coil winding 30 is received by the 96 KHz receiver circuit 72 and used to continuously charge an energy storage capacitor 74 . The capacitor charge is held by the 96 kHz signal at a level which is necessary to actuate the inflation device 20 to deploy the airbag 18 .

The capacitor 74 is coupled to the inflation device 20 via a transistor 76 , the gate of which is coupled to the 32.7 KHz receiver circuit 70 . A 32.7 KHz signal induced in secondary coil winding 30 will cause the 32.7 KHz receiver circuit 70 to become active, thereby "turning on" transistor 76 via signal line 78 . This in turn will create a discharge path for the capacitor 74 through the inflation device 20 , thereby deploying the airbag 18 .

In general, a 96 KHz signal is induced in the secondary coil winding 30 . However, when an air bag deployment signal is received via signal line 60, the electronics on the primary side 28 will interrupt the 96 KHz signal and induce a 32.7 KHz signal in the secondary coil winding 30 to initiate the discharge of the capacitor 74 to deploy the air bag 18 .

The so far described section of the circuitry on the secondary side 32 is primarily concerned with the transfer of power across an annular gap 11 to energize (charge) a capacitor 74 for storing energy to deploy an airbag 18 and so on Control unfold.

The electronics on the secondary side 32 , which is used to transmit communication data across the annular gap, comprises a multiplexer 84 and a modulator 86 . The multiplexer 84 receives binary inputs (which have a "1" or "0" state value) from the steering surface control elements 22 and the airbag inflation device 20 . It converts these multiple binary inputs into a serial output with a stream of binary words (ie, a predetermined number of binary values that are generated sequentially). There is a unique binary word assigned to each state of each binary input to multiplexer 84 .

The serial output is received by the modulator 86 , which modulates an impedance of the secondary coil winding 30 accordingly. For example, when a binary "1" is received, the modulator 86 loads the secondary coil winding 30 with an added impedance. When a binary "0" is received, the added impedance is removed.

The impedance of the secondary coil winding 30 affects the inductive coupling between the primary and secondary coil windings 26 and 30 and in particular, affects the amplitude of the voltage developed across the primary coil winding 26th For example, a larger impedance in the secondary coil winding 30 reduces the amplitude of the voltage developed across the primary coil winding 26 and vice versa. By modulating the impedance of the secondary coil winding 30 between two impedance levels, the voltage developed across the primary coil winding 26 will modulate accordingly between two amplitude levels.

Back to Fig. 3A, the demodulator 64 compares the clamping voltage on the low voltage side of the primary coil winding 26 with a predetermined threshold voltage of each "off" -ZY klus of transistor 58. (Note that during each "on" cycle of transistor 58 , the secondary side of primary coil winding 26 is at ground (0 VDC) potential.) If the primary coil winding voltage is less than the threshold voltage, a binary "1" of the demo dulator 64 generated. Otherwise a binary "0" is generated.

The output of demodulator 64 is therefore a serial output with a stream of binary numbers having the values of "1" or "0" that are identical to those used by the multiplier 84 of the circuit on the secondary side of FIG. 3B are given. The demultiplexer 66 decodes the serial output to control the binary status of each of the steering surfaces and the air bag inflator 20 at a data transfer rate of 96 KHz. This information can then be used by suitable control devices for controlling the corresponding vehicle systems.

In summary, a device for transmitting power and communication data over an annular gap is provided with an inductively coupled primary coil winding ( 26 ) and secondary coil winding ( 30 ) which is rotatable therein. Two signal oscillators ( 50 , 52 ) are electrically coupled to a transistor ( 58 ) for controlling the current flow through the primary coil winding, thereby inducing a signal with a respective frequency in the secondary coil winding. An electronic switch ( 56 ) causes one of the two signals ( 52 ) to be applied to the transistor for charging a capacitor ( 74 ) coupled to the secondary coil winding and causes the other of the two signals ( 50 ) to be on the transistor is applied to discharge the capacitor. Actuation of the control devices ( 22 ) causes the impedance of the secondary coil winding to be modulated ( 86 ). The inductive coupling of the two coil windings causes this modulation to be reflected by modulating the voltage developed across the primary coil winding. The primary coil winding voltage is compared ( 64 ) to a threshold voltage for decoding the modulated voltage and for determining actuation ( 66 ) of the control devices.

Claims (4)

1. A device for transmitting power and communication data across an annular gap, the device comprising
a primary winding ( 26 ) positioned around a central axis ( 14 ),
a secondary winding ( 30 ) positioned about the central axis, rotatable with respect to the primary winding and forming the annular gap therebetween, the secondary winding being positioned in accordance with the primary winding such that the two windings are inductively coupled,
Means for generating a first signal ( 52 ) at a first frequency,
Means for generating a second signal ( 50 ) with a second frequency,
a transistor ( 58 ),
Means ( 56 ) for selectively applying one of the first and second signals to the transistor to control the flow of current through the primary winding to induce a signal in the secondary winding at one of the first and second frequencies,
a capacitor ( 74 ) coupled to the secondary winding and charged by the induced signal in the secondary winding at the first frequency, and
Means ( 76 ) for discharging the capacitor charge as a function of the induced signal in the secondary winding with the second frequency. 2. The apparatus of claim 1, further comprising
at least one control device ( 22 ) which is coupled to the secondary winding, each control device having at least two operating states,
Means ( 86 ) for varying an impedance of the secondary winding depending on a current state of each controller, the varying impedance varying a voltage developed across the primary winding, and
Means ( 64 , 66 ) for decoding the primary winding voltage to determine the current state of each controller. 3. The apparatus of claim 2, wherein the means for varying an impedance of the secondary winding comprises
Means ( 84 ) for generating a stream of binary numbers having a first and a second value, each predetermined number of sequentially generated binary numbers in the stream corresponding to a predetermined serial code of binary values identifying a current state of a predetermined controller , and each state of each controller has a unique serial code, and
Means ( 86 ) for (i) adding an impedance to the secondary winding in response to a generated binary number having a first value and (i) removing the impedance from the secondary winding in response to a generated binary number having a second value, wherein the Secondary winding varies between one of the two impedance values. 4. The apparatus of claim 3, wherein the means for decoding the primary winding voltage comprises
Means ( 64 ) for (i) generating a binary number having a first value as a function of a voltage having a value which exceeds a predetermined threshold value, and
(ii) generating a binary number having a second value in response to a voltage having a value that does not exceed the predetermined threshold, and means ( 66 ) for identifying a predetermined number of sequentially generated binary values as one of the unique serial codes which corresponds to a current state of a predetermined control device.