EP0235237A1 - Electric power generator for supplying an electronic circuit - Google Patents

Abstract

In an electric generator intended to supply an independent electronic circuit for transmitting a pneumatic pressure, mounted on a wheel of a motor vehicle, or other applications requiring an electrical supply of an independent electronic circuit mounted on a rotary shaft , a dynamo (49) comprises two assemblies moving relative to one another, one of them being the stator and the other the rotor of the dynamo, the first of these assemblies being integral with the rotary shaft (65) and coaxial with the latter and the second movable assembly consisting of a flywheel (85) of appreciable mass and rotating around said rotary shaft. The dynamo comprises a field coil connected to a power input point of said electronic circuit.

Description

ELECTRIC POWER GENERATOR FOR SUPPLYING AN ELECTRONIC CIRCUIT This invention relates to a device designed to monitor air pressure in motor vehicle tires, which operates during the time the motor vehicle is in motion. In particular, this invention refers to the part of the device that has the function of converting the air pressure information into electrical signals and transmit these signals from the vehicle wheel, and it further refers to the supply of electric power to said part.

Each said part of the device is designed to be attached to one wheel of the vehicle so that it will be revolving, that is to say moving with respect to the vehicle body. For that reason, supplying power to said moving part presents considerable problems, since connecting it to the car battery would require the use of a commutator-and-brush assembly which would obviously be too complicated. It is therefore desirable that the moving part of the monitoring device, which includes a transducer, a transmitter, as well as the electric power supply to both, be mounted independent of the vehicle body. The term "independent" is being used to imply the absence of any type of connection whether electrical or of any other type, with the vehicle body and, in particular, with the battery.

The use of solar cells should also be discarded in that their operation is usually adversely affected by dirt build-ups. Considering the application for which the device is designed, frequent cleaning would be necessary. This invention results from having ingeniously conceived of utilising an existing power source, namely the mechanical energy produced by the rotary motion of the wheel with respect to a universal frame of reference. Roughly speaking, the terrestrial gravitational field may be considered as the frame of reference. Essentially, this invention is based on the conversion of the rotational kinetic energy generated by the wheel axle into electric power suitable to feed the pressure state transducers and transmitters.

This invention physically comprises a dynamo mounted integral and coaxial with the car wheel axle; the dynamo includes two assemblies, mutually free to rotate and identified as the dynamo stator and rotor, one of which is integral coaxially with the wheel axle and the other consists of a flywheel of appreciable mass revolving about said axle, as well as a field coil having the function of generating the electrical energy necessary for the above mentioned power supply. Although the electric power generator described in the preceding paragraph is intended to be used with a motor vehicle tire air pressure monitoring device, it can be used as well to supply power to any type electric or electronic circuits mounted on a rotating shaft.

In the following, the present invention will be further clarified by the description of a practical embodiment of this invention, a description made out in a purely illustrative way, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a motor vehicle with a sketch of the monitoring device to which the power generator according to this invention is applied.

Figure 2 is a block diagram illustrating the principle of operation of said monitoring device. Figure 3 is a cross-section view of a motor vehicle wheel with the power generator attached to the wheel rim.

Figure 4 is a detailed cross-section view of one embodiment of the power generator according to this invention, and the location of the monitoring device transducer and transmitter printed circuit boards.

Finally, Figure 5 is a detailed cross-section view of a second embodiment of the power generator according to this invention, and the location of the monitoring device transducer and transmitter printed circuit boards.

Referring first to Figure 1, the embodiments of this invention will be described in detail. Figure 1 shows a motor vehicle 11 comprised of a body 13 and wheels 15, the number of wheels ranging from a minimum of four such as in a sedan or jeep type of vehicle, to six or more such as in a carrier used for transporting goods or passengers. On motor vehicle 11 is mounted a monitoring device composed of moving or external parts 17 attached to each wheel 15, and a stationary or internal part 19 located inside body 13 of vehicle 11.

The stationary part 19 terminates with an alarm device consisting of display 21 mounted on panel 23 inside the passeneger compartment 25 of vehicle 13. The moving part 17 is connected through a tube or hose 27 to a chuck 29 located on the tire or cover 31 of each wheel 15; chuck 29 contains a valve which is conventionally used to inflate tire 31. The chuck 29 and tube 27 assembly allows the passage of air defined as air pressure inlet to the monitoring device 17, 49. In particular, display 21 contains as many indicator lights 33 as are wheels 15, which have the dual function of warning the driver, while the vehicle is in motion, of a low pressure condition in any tire 31 and indicating which tire 31 is in that condition. To that puirpose, moving part 17 senses the air pressure value in the tire to which it is attached to send a corresponding signal to stationary part 19. One advantage, in particular, is that the signal originated by the moving part is of binary type i.e. it indicates either normal or insufficient air pressure in tire 31.

In order to better explain the application of this invention, a block diagram of the pneumatic pressure monitoring device is provided in Figure 2. As previously mentioned, the monitoring device is composed of a moving or external part 17 and a stationary or internal part 19, the terms "moving" and "stationary" being in this case used with respect to the driver of motor vehicle 11 or to the vehicle body 13. Moving part 17 includes a pressure transducer or converter pressure gage (P/V) 35 which receives pressurised air from tire 31 through tube 27 and converts said pressure value into a binary electric parameter, namely an electric voltage. In particular, transducer 35 will provide an ON signal through output 37 only in the case the pressure value detected is within a predetermined threshold equivalent to tire 31 normal pressure range. Furthermore, transducer 35 may simply consist of a switch which would sense the air pressure in tube 27 and would close when pressure is within the normal range to l et pass an ON si gnal that wi l l enabl e osci l l ator 39.

Oscillator 39 will generate a radio frequency signal when pressure in tire 31 is normal, and viceversa, it will not produce any signal when pressure is low, especially when tire 31 gets deflated.

The oscillator 39 signal is fed into a code modulator circuit 41 having the function of modulating the signal output by oscillator 39 in a code that will permit later identification cf wheel 15 location in vehicle 11. Said modulation and coding process may be of the type 1 nown as PCM, in which modulation is applied by a pulse train and a code is generated according to pulse amplitude or repetition frequency.

The modulated and coded signal output from circuit 41 is applied to a transmitting amplifier (TX) 43 which adapts its amplitude level and sends it to a transmitting antenna 45.

In order to be able to perform their specific functions, components 35, 39, 41, 43 of moving part 17 of the monitoring device are fed with electric power generated by generator (GEN) 49 through a supply line 47. Generator 49 is the main component of this invention and will be described in detail in later paragraphs.

The stationary part 19 of the monitoring device includes a receiving antenna able to receive- the radio frequency signal emitted by transmitting antenna 45 and connected to the input of a receiver 53.

Antenna 51 may either be connected by means of individual cables to be run up to the fender relevant to each wheel 15, or it may be a single antenna located on panel 23 containing display 21. The latter solution, though requiring greater output power from transmitter 43, would make it easier to install stationary part 19 in vehicle 11, since it would only be a matter of installing some modules.

Receiver 53 amplifies and demodulates the input signal that indicates the pneumatic pressure value in one of wheels 15, and sends that signal to a decoder (DEC) 55. The decoder 55 output is connected to display 21 through a harness 57 of cables which are individually connected to a.s many indicator lights 33. Indicator lights 33 can consist of LEDs arranged in a geometric configuration rεproduicing that of wheels 15 of motor vehicle 11, thus making it easier to identify the wheel 15 corresponding to the indicator light 33.

Components 21, 53, 55 of stationary part 19 are powered through another power supply line 59 connected to battery 61 of motor vehicle 11.

It should be emphasised that according to the monitoring device 17, 19 principle of operation, the radioelectric signal is transmitted during the time pneumatic pressure is normal and alarm 21 is activated when no such radioelectric signal is transmitted. In other words, under normal pressure conditions the signal is transmitted continually, and transmission stops as soon as pressure gage 35 senses a low pressure condition. Thanks to this feature, any failure of the monitoring device 17, 19 to generate, transmit, and receive the pressure value signal can be immediately detected, since the alarm is activated by the absence of signal caused by such a circuit failure.

The following description specifically applies to the main object of this invention and provides details of its installation with reference to Figure 3. Figure 3 is a cross-section view taken along the diameter of one front or rear wheel 15 of motor vehicle 11, comprising tire 31 mounted on rim 63 which is attached integral with rotating axle 65. Axle 65 conventionally carries a hub 66 to which rim 63 is attadnec by mean s of a set of bolts and nuts 67. The moving part 17 of the monitoring device is contained in a housing 69 which is attached concentric with rim 63 by means of the same sat of bolts and nuts 67. Hose 27 projects from housing 69 and terminates with a sealed threaded fitting 70 attached to chuck 29 in place of the nipple normally used on a conventional wheel 15. Fitting 70 contains a needle (not shown) which pushes chuck 29 center pin to open the valve of tire 31 and transmit pressure to transducer gage 35. That completes the installation of part 17 of the monitoring device, including generator 49 according to this invention, whose evident advantage is that it does not require any modification whatsoever to wheel 15 components. In addition to the advantage of not having to modify in any way wheel 15 conventional components, the fact that device 17 is mounted by utilising the same nut 67 as used for attaching rim 63 to hub 66, will allow providing part 17 with a theft protection for wheel 15 at no additional cost, by using a special nut with locknut currently available on the market, to protect wheel 15 against said risk.

Figure 4 is a detailed view of housing 69 containing part 17, according to a first embodiment of this invention.

Housing 69 consists of a base 71 and a cover 73 on both of which holes are drilled in line with each other and with bolts 67 of wheel 15.

According to this invention, generator 49 consists of a direct current motor contained in casing 77. Casing 77 mounts a circular support 79 secured to base 71 by means of screws 81, The direct current generator 49 is aligned coaxially with axle 65 so that casing 77 will rotate together with wheel 15.

Generator 49 includes a rotating shaft 83 projecting from casing 77, on which is mounted a flywheel 85, also contained in housing 69. According to this invention principle of operation, casing 77 together with the stator assembly of generator 49 rotates at the same speed as wheel 15 while vehicle 11 moves on; whereas flywheel 85 slips with respect to the rotary motion of wheel 15 since rotating shaft 83 is mounted idle on axle 65 of wheel 15. The slipping άf flywheel 85 is due to the fact that its inertia makes it rotate at a considerably lower angular speed than that of axle 65. Ideally, flywheel 85 should practically stand still with respect to vehicle body 13 for the purpose of increasing generator 49 output power; however, the flywheel is drawn to rotate because of friction in the bearings that support rotating shaft 83 and, essentially, because of the electromagnetic coupling between the rotor and stator of generator 49. In other words, there are two kinds of opposing forces acting upon flywheel 85, one force being generated bysaid electromagnetic coupling which tends to cause wheel 15 to draw flywheel 85 to a rotary motion, and the other force being originated by flywheel 85 inertia which counteracts said rotary motion. Flywheel 85 should desirably have an appreciable mass in order to increase its moment of inertia, hence its checking action, as well as to increase t he slipping motion and maximising the generator 49 output power. Figure 5 is a cross-section view taken along the diameter of a detail of a second preferred embodiment of generator 49 according to this invention. In this embodiment dynamo 49 is provided with a flat stator consisting of a field coil 93 wound about a stator plate 95. In this configuration, a coil 93 has several turns of extremely reduced thickness, of the order of the diameter of the wire used for winding coil 93, which results in considerably smaller size of housing 69 and, therefore, reduced size of the portion of the device projecting from rim 63 (Figure 3).

The dynamo 49 rotor includes a permanent magnet 97 adhering to flywheel 85, in which a recess has been machined to accommodate magnet 97 so that its outer surface be flush with that of flywheel 85.

Both the dynamo 49 and printed circuit boards 87 are mounted on a supporting sleeve 79' fastened to base 71 of housing 69 by means of screws 81', the same as stator plate 95 is fastened to supporting sleeve 79'. Printed circuit boards 87 can be mounted directly using long screws 89' and appropriate spacers to attach them to stator plate 95. Rootating shaft 83 is mounted inside supporting sleeve 79' and kept in place by means of two bearings 99 suitable to allow it to rotate freely with respect to axle 65 with which it is aligned coaxially.

It is obvious that other numerous and different changes and modifications can be performed by the skilled in the art on the embodiments of the present invention hereinbefore described, without departing from its scope, which is clearly specified in the claims that follow.

Claims

C L A I M SHaving described in detail and determined the nature of this invention and. the possible embodiments, exclusive proprietary rights are hereby claimed for the following:

1. An electric power generator to be used to feed an independent pneumatic pressure transmitting electronic circuit, mounted on a wheel of a motor vehicle, or any other application requiring power supply of an independent electronic circuit mounted on a rotating shaft; wherein a dynamo comprising two assemblies moving with respect to each other, of which one is the stator and the other the rotor of the dynamo, the first one of said assemblies being mounted integral and coaxial with said rotating shaft and the second moving one consisting of a flywheel of appreciable mass rotating about said rotating shaft; and wherein said dynamo includes a field coil connected to one supply incut of said elec ronic circuit.

2. A generator according to Claim 1, wherein said flywheel is considerably unbalanced.

3. A generator according to any one of Claims 1 and 2, wherein said field coil is associated with said stator, while said flywheel is provided with a permanent magnet adhering to the same and being part of said rotor.

4. A generator according to Claim 3, wherein said rotor is disc-shaped and is located in front of said stator which, in this case, is disc-shaped too and on which said substantially flat field coil is wound.

5. A generator according to any one of the preceding Claims, wherein said stator has at least one printed circuit board attached to it, said electronic circuit being mounted on at least one said board and including a transducer pressure gage provided with one air inlet connected to said, wheel tire and one electric output connected to the input of a pressure transmitter.

6. A generator according to any one of the preceding Claims, wherein said first moving assembly is attached to said rotating shaft by means of the same sets of bolts and nuts as used for fastening the wheel.

7. A generator according to Claim 6, wherein said dynamo and said electronic circuit are provided with a cover fastened to said wheel by means of said sets of bolts and nuts.

8. An electric power generator used to feed an independent oceumatic pressure transmitting electronic circuit mounted on a motor vehicle wheel, essentiallyconstructed, located and operating as specified in thetechnical description with reference to the accompanying drawings.