JP2006191276A - Transmitting device for electric power and information by proximity magnetic field coupling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a device which supplies electric power and transmits signals by proximity magnetic field coupling small-sized by putting close or uniting transmission lines (magnetic paths) of an electric power system and a signal system and to prevent noise from the electric power system from being mixed with a transmitted signal. <P>SOLUTION: A transformer is constituted wherein an exciting coil and a feed coil are loosely coupled with each other, and a flyback type converter is used which accumulates electric power by applying DC power to the exciting coil and supplies electric power to a load with an electromotive force induced across the feed coil by cutting off the DC power. In a non-feed period wherein current variation of the exciting coil is nearly constant and the power supply from the feed coil is stopped, communication is carried out from a transmitting coil which is nearby the feed coil and rotates together to a magnetic detector nearby it with a high-frequency magnetic field on which a pulse-modulated signal is superposed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

Supply power necessary for operation from the main device to the peripheral device by proximity magnetic field coupling between the main device and the peripheral device, and transfer of information (communication) between the main device and peripheral device by the near magnetic field coupling It is the technique regarding the apparatus which performs. In particular, even when a peripheral device is rotated, power can be supplied and information can be transmitted (communication) without contact.

A coaxial circular coil in which two circular coils are opposed to each other is known as a power transmission means based on near magnetic field coupling. As a main application, it is used as a rotary transformer that supplies power to a rotating object. This form has a feature that the magnetic coupling is sparse compared to a general transformer, that is, the power factor of power transmission is low, but low power transmission can be easily realized. On the other hand, in the patent documents “Transformer for power supply to rotating body” and Non-patent document “Use of core-type rotary transformer for non-contact power feeding to rotating detector”, circular coils (power feeding in FIG. 1) A rotary transformer (hereinafter referred to as a core type rotary transformer) in which the exciting coil 5 is connected in parallel via a core 6 is introduced. The core type rotary transformer can increase the power supply in proportion to the square of the number of exciting coils, and at the same time improve the power supply efficiency, which can be applied to objects with large diameters that were difficult in the past. It becomes.

Japanese Patent Laid-Open No. 10-230375 Odawara Yukio (Inventor) "Use of core-type rotary transformer for non-contact power supply to rotating detector" IEEJ Transactions D (October 2001, P.1068-1074)

Transformers in the form of coaxial circular coils or core-type rotary transformers supply power without contact, but information (signal) transmission means are also required for measurement control applications. If the signal is considered as electric power, another set of transformers can be used. However, in order to improve convenience, when the power supply transformer and the signal transmission transformer are brought close to each other, the noise caused by the power supply is received in information transmission, and the information is correctly received. Solve the problem of transmission failure.

Flyback converters, which are also used to drive coaxial circular coils and core type rotary transformers, store power in the coil while the transistor of the switching element is on, and then during the period when the transistor is off. It is a converter that supplies electric power stored in a coil to a load. Of this power supply cycle, the period in which power is stored in the coil, that is, the rest period of power supply to the load, is a monotonous (linear) magnetic field change and occupies most of the power supply cycle. Therefore, during the suspension period of power supply to the load, the signal transmission coil and magnetic detection means in the vicinity of this transformer communicate with a high-frequency magnetic field carrying a pulse-modulated signal based on near magnetic field coupling, thereby affecting the effect of power supply (noise). ) Good information transmission without receiving.

Non-contact power supply and information transmission can be realized with a simple transformer. In addition, since the power and information signal transmission paths are shared, it is effective in reducing the size of the transformer of the mechanical component as compared with the case where these are separate. Furthermore, the information transmission period can be several times longer than the power supply period, and it is easy to cope with higher speed and higher accuracy of information transmission.

  For example, an example is shown in which the torque of the rotating shaft is measured in real time by a detector attached to the rotating shaft. As shown in FIG. 1, the transformer that supplies electric power includes an exciting coil 5 and a core 6 that are stationary parts, and a power supply coil 3 that rotates together with the rotating shaft 4. Further, in order to perform information transmission, the transmission coil 1 is added to the outer periphery of the feeding coil 3, and the magnetic detector 8 is placed on a stationary part in the vicinity. In the figure, the number of exciting coils 5 is two, but can be changed as necessary. The gap 7 of the core 6 is a gap through which the support member 9 and the wires of the feeding coil 3 and the transmission coil 1 pass, and it is desirable that the gap 7 be as small as possible. In addition, the spacer 2 having an appropriate thickness can be sandwiched between the transmission coil 1 and the feeding coil 3 to suppress the electric field coupling between them.

FIG. 2 shows a block diagram of the power feeding circuit and the signal transmission circuit, and FIG. 3 shows operation waveforms of each part.
In the main device side circuit 35 (stationary part) of the power supply circuit 37, the DC power source 10, the exciting coil 5 having the parallel-connected resonant capacitor 14, and the semiconductor switch 12 having the commutation diode 13 are connected in series. In the peripheral device side circuit 36 that rotates together with the rotating shaft 4, the feeding coil 3, the rectifier capacitor 16, and the rectifier diode 17 are connected in series. In this case, the connection polarity of the rectifier diode 17 is a direction in which energization due to the electromotive force generated in the power feeding coil 3 is prevented when the semiconductor switch 12 is on. Note that a damper 15 made of a resistor and a diode is used in order to attenuate the electrical vibration generated by the inter-terminal capacitance of the rectifier diode 17. In FIG. 2, there are two sets of the exciting coil 5, the core 6, the resonant capacitor 14, the semiconductor switch 12, and the commutation diode 13, and each set has the same conditions in terms of characteristics and control. It can be changed as needed.

  Power supply is performed by periodically turning on / off the semiconductor switch 12 by the timing clock 11, and when the semiconductor switch 12 is turned on, electric power is accumulated in the exciting coil 5. Generate vibration. Along with this, the rectifier diode 17 is energized by the electromotive force induced in the feeding coil 3 by the alternating magnetic field generated in the exciting coil 5, and the rectifier capacitor 16 is charged. Then, the charging power of the rectifying capacitor 16 is output from the peripheral device power supply terminal 18 and used as the power supply for the peripheral device side 36. These are the so-called flyback converter configurations.

  A period during which the rectifying capacitor 16 is charged by the electromotive force generated in the power feeding coil 3 is defined as a power feeding period (41 in FIG. 3), and a period during which charging is not performed is defined as a non-power feeding period (42 in FIG. 3). In the initial period of the non-power supply period 42, the semiconductor switch 12 is off, and the current in the main device side circuit 35 is in the direction of the negative electrode of the DC power supply 10 → the commutation diode 13 → the exciting coil 5 → the positive electrode of the DC power supply 10. This current increases linearly from a negative value. If the semiconductor switch 12 is set to be turned on before the current value becomes zero, then, the current flows from the positive electrode of the DC power supply 10 to the exciting coil 5 → the semiconductor switch 12 → the negative electrode of the DC power supply 10. The current and current values increase linearly. (The current of the exciting coil 6 is indicated by 46 in FIG. 3.) At this time, if the weak current flowing through the damper 15 connected in parallel with the feeding coil 3 is ignored, generally no current flows from the feeding coil 3. (The feeding coil current is indicated by 47 in FIG. 3.) That is, during the non-feeding period 42, the voltage applied to the exciting coil 5 is substantially equal to the voltage of the DC power source 10, and therefore the magnetic field change by the exciting coil 5 is also almost equal. It is constant. For this reason, by transmitting information during the non-power supply period 42, communication that is not affected by the influence of power supply (noise) becomes possible.

The operation cycle 40 of the timing clock 11 T, the length of the passive period 42 and _{T R.} (See FIG. 3) Generally, the ratio of the amplitude voltage of the resonant capacitor 14 to the output voltage of the DC power supply 10 is about 20 times, and (T _R / T) is 0.80 to 0.95. When the voltage ratio is increased, the ratio occupied by the non-power supply period is further increased, which is advantageous in terms of information transmission control.

  On the other hand, in the power feeding period 41, the current of the exciting coil 5 changes greatly in a short time, and the charging current to the rectifying capacitor 16 is also generated and changed in the power feeding coil 3. On the other hand, immediately after the end of the power supply period 41, the voltage applied to the rectifier diode 17 changes suddenly from the forward direction to the reverse direction, and electrical vibration occurs between the inter-terminal capacitance of the rectifier diode 17 and the power supply coil 3. For this reason, the power feeding period 41 and the transition period immediately after this are not used for information transmission.

The signal transmission circuit 38 is divided into a main body device side circuit 35 (stationary part) and a peripheral device side circuit 36 (rotation part) like the power feeding circuit 37. In order to synchronize signal transmission, the power supply period 41 and the non-power supply period 42 are detected in each circuit. In the peripheral device side circuit 36, the power supply period 41 and the non-power supply period 42 can be directly discriminated by detecting the voltage between the terminals of the rectifier diode 17 by the power supply detector 19. On the other hand, in the main device side circuit 35, the time when the semiconductor switch 12 is turned off from the on state substantially coincides with the start of the power supply period 41. In addition, since the length of the power supply period 41 is constant in a steady state and can be measured in advance, the start of the non-power supply period 42 is longer than the power supply period 41 (T−T _R ). The semiconductor switch is simply turned off by the timing clock 11 (43 in FIG. 3).

  Next, an operation for transmitting an analog signal by a sensor or the like will be described. The feed detector 19 detects the start of the non-feed period 42, the next triangle wave generation circuit 20 raises the triangular wave of the pulse-width modulated carrier from the reset state, and returns the triangle wave to the reset state by the end of the no-feed period 42. . (See 48 in FIG. 3) In the next PWM modulation circuit 22, the analog signal input 21 and the triangular wave voltage are compared and converted to a binary pulse signal by PWM modulation. (Analog signal corresponds to 49 in FIG. 3. Also, this change is assumed to be slow compared with the timing clock period T. The binary pulse signal corresponds to 50 in FIG. 3.) The wave modulation circuit 23 performs amplitude modulation to generate a high-frequency magnetic field around the transmission coil 1. Here, the capacitor 24 prevents the transmission coil 1 from being energized during the power supply period 41. The capacitor 25 is used to generate a high frequency magnetic field by resonance.

In the main device side circuit 35, the high frequency magnetic field generated by the transmission coil 1 is detected by the magnetic detector 8, the low frequency component which is mainly power supply noise is removed by the band filter 26, and the continuous wave demodulation circuit 27 detects the high frequency magnetic field. . As shown by 51 in FIG. 3, the waveform after detection has a slow rise and fall of the signal, and the amplitude may also fluctuate. Therefore, an error occurs when this on / off determination is made with a certain threshold. . Therefore, the next differentiation circuit 28 and a binary conversion circuit 29 using a Schmitt comparator detect the rising and falling edges of the signal of the waveform after detection and convert it to a binary signal to reduce the error. Next, the pulse detection circuit 30 refers to the timing clock 11, detects only the pulse signal corresponding to the non-feed period 42, and obtains the received PWM signal 54. This is converted into an analog signal by the PWM demodulation circuit 31 and output from the terminal 32.

  In response to the above-mentioned “Best Mode for Carrying Out the Invention”, a system for specifically measuring the torque of an axle was prototyped. In the rotating transformer of the mechanical component, the diameter of the feeding coil 3 was 13 cm, and the number of windings of the conducting wire was 20 times. A ferrite core having an outer diameter of 28 mm, an inner diameter of 15 mm, a thickness of 13 mm, and a gap of 6 mm was used as the core 6. The number of exciting coils 5 is one. The feed coil 3 has a self-inductance of 200 μH, the excitation coil 5 has a self-inductance of 160 μH, and their mutual inductance is 60 μH. The resonant capacitor 14 is a 0.02 μF high voltage capacitor, and the semiconductor switch 12 is a power MOS • FET incorporating a commutation diode 13. A vinyl-coated conductive wire was wound twice with a spacer 2 of about 1 mm on the feeding coil 3 as the transmission coil 1. The inductance of the transmission coil 1 is 0.7 μH. The magnetic detector 8 uses a coil having a diameter of 20 mm as means for magnetic detection, and amplifies the signal by a transistor (FET).

The voltage of the DC power source 10 was 10 V, the operating frequency of the timing clock 11 was 20 kHz, the on / off duty ratio of the semiconductor switch was 80%, 1 W was fed at an efficiency of 60%, and signal transmission was performed. The continuous wave modulation circuit 23 is an AM system and has a frequency of 20 MHz. The signal transmission distance could be separated from the winding of the transmission coil 1 to about 15 mm at the coil tip of the magnetic detector 8. FIG. 4 shows an analog signal output waveform 59 in which a sine wave signal (58 in FIG. 4) having a frequency of 1 kHz and an amplitude of 2 V is input to the analog signal input 21 and this transmission signal is observed by the analog signal output 32. Although the PWM demodulating circuit 31 has a stepped waveform because it depends on the sample-and-hold circuit, transmission of signals (information) was obtained with sufficiently practical accuracy and speed.

(1) Although the rotary type is shown as the best mode and example for carrying out the invention, a stationary type can also be applied. Thus, it can be used as a power supply and information transmission means that is detachable even in an environment with a lot of flammable gas or dust or in water.

(2) Although the best mode and embodiment for carrying out the invention are based on the core type rotary transformer described in the background art, a coaxial circular coil having similar characteristics can also be used.

(3) In the best mode and embodiment for carrying out the invention, a signal to be transmitted is a pulse width modulation (PWM) signal, but a digital signal is sequentially bit by bit during a non-feed period (42 in FIG. 3). It can also handle serial transmission.

(4) In the best mode and embodiment for carrying out the invention, an example is shown in which power is supplied from the main device side (35 in FIG. 2) to the peripheral device side 36 and signal transmission is performed in the opposite direction. However, it is also possible to perform signal transmission in the same direction as the direction of power supply.

(5) The present invention is a wiring that connects the circuit of the movable part and the circuit of the stationary part, and can solve the problem that the skin of the wiring is damaged and peeled and fine dust is generated, or the wiring is made compact. Since it can be put together, it can cope with dust-proof measures and downsizing of clean room compatible devices.

Structure of rotating transformer for mechanical parts Circuit block diagram of the device of the present invention Operation waveform of each part in FIG. Observation waveform of signal transmission in Fig. 2

Explanation of symbols

40 Period of power supply and signal transmission based on the timing clock (31) (period T)
41 feeding period 42 parasitic period _(T R)
43 Semiconductor switch (12) ON period 44 Semiconductor switch (12) OFF period 45 Waveform showing semiconductor switch (12) ON / OFF state 46 Excitation coil (6) Current waveform 47 Feed coil (3 ) Current waveform 48 Triangular wave generation circuit (20) Output waveform 49 Analog signal input (21) Waveform 50 PWM modulation circuit (22) Output waveform 51 Continuous wave demodulation circuit (27) Output waveform 52 Differentiation circuit (22) Output waveform 53 2 Value conversion circuit (29) output waveform 54 Pulse detection circuit (30) output waveform

Claims (1)

Using a transformer that forms a sparse magnetic coupling between the power supply coil and the excitation coil, the power is stored by applying a DC power supply to the excitation coil, and the load is generated by the electromotive force induced in the power supply coil by the disconnection of the DC power supply. In the flyback converter for supplying power, a transmission coil and a magnetic detector are provided in the vicinity of the transformer, and during the non-feeding period in which the current change of the excitation coil is substantially constant and power supply to the load is stopped, A power and information transmission device using near magnetic field coupling that performs communication by a high-frequency magnetic field based on pulse modulation between a transmission coil and the magnetic detector.

Images