Abstract:
The present invention relates to a less current consuming noncontact type 2-channel rotary positioning sensor which can accurately measure the magnitude of the magnetism caused by the rotation of a rotating body by eliminating the imbalance of the magnetism that can be generated due to the eccentricity of the rotating body, by sensing with two hall element the magnitude of magnetism detected by two sensing bars located in opposite places.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates generally to a less current consuming non-contact type 2-channel rotary positioning sensor, and more specifically to a less current consuming non-contact type 2-channel rotary positioning sensor which can accurately measure the magnitude of the magnetism caused by the rotation of a rotating body by eliminating the imbalance of the magnetism that can be generated due to the eccentricity of the rotating body. This invention includes the use of a special geometrical arrangement of sensing bars with two hall elements producing two all most identical linear analog signals. In addition switches are provided by the use of comparator generated switch positions. A microprocessor capable of analog to digital conversion is also included in the present invention to allow digital conversion of the analog signals. The present invention facilates communication with other equipment such as the ECU of a vehicle. 
     A rotary positioning sensor is conventionally used to apply continuously changing physical changes of a rotating body to electric circuits. Rotary positioning sensors equipped with electric signal output are utilized in various ways in many industries. For example, they are used for the control of the engine throttle valve position for a transport vehicle, rotation angle control of a steering shaft, treading control of an electromagnetic accelerator pedal, positioning control of heavy equipment or farm machines, or on-off measurement of a fluid feed valve. 
     The methods of measuring rotary positioning include potentiometric sensing, coded disk shaft encoder sensing, hall elements sensing, magneto-resistive sensing, and inductive sensing types. In actual use, it should be possible to operate at temperatures of −40° C. to +70° C. required by extreme operating conditions of, for example, a commercial vehicle or heavy equipment and to maintain a minimum endurance period of about 5 million operating cycles. In addition the accuracy of any switch position should be kept within an error range of ±2% throughout the life of the position sensor together with an endurance exceeding the minimum endurance period of 5 million operation cycles required in working environments of dust and vibration. 
     Unfortunately the conventional contact potentiometric rotary positioning sensor, which is made of a printed circuit board (hereinafter to be referred to as PCB) or a ceramic board processed with resistance tracks, has drawbacks such as change of electric characteristics due to temperatures and limits to the endurance period and component life due to brush wear. As a result, there are other problems related to the conventional contact resistance potentiometer. 
     First, with some applications the potentiometer is calibrated to various set points prior to delivery. However experience has shown that after a certain period of operation on a vehicle, the set points have drifted away from specification and exceed a limit value in many cases. 
     Second, because of the moving wear contact between the electric resistance track and the brush, there is frequently a deterioration in the integrity of the electrical contact between the brush and track. This can make the output signal more vulnerable to the electrical noise caused by the peripheral electric devices and extreme operating conditions (dust, moisture, vibration, temperature). Such electrical noise changes durability and accuracy. 
     Third, it is impossible to have one design for all applications based on the conventional potentiometer. Design change and further validation of the design is necessary to optimize the conventional potentiometer for different applications which all add to the cost of a product. Examples where major design changes would be needed include the maximum limit to the rated capacity (0.5 watt rated for commercial vehicle, 1.5 watts for heavy equipment) and a change in resistance value (2.5 kW, 5 kW, single track, double track). Each application would require a new design of potentiometer and associated development and tooling costs. 
     Fourth, in the conventional potentiometer the sensor switch load capacity is restricted to 50 mA or less on average, which has limitations in controlling the load in various control circuits where the potentiometer may be used. 
     Fifth, a conventional type contact potentiometer with two or more switches built in the sensor is limited by the power supplied from an electromagnetic unit. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can accurately provide two independent linear analog measurements of the magnitude of magnetism caused by the rotation of a rotating body. This measurement can be obtained by eliminating the imbalance of magnetism that can occur due to the eccentricity of the rotating body. Two hall elements are used to sense the magnitude of magnetism detected by sensing bars located in different positions. 
     It is another object of the present invention to facilitate the measurement of the intensity of magnetic force in two different positions either in the same direction or mutually reverse direction according to the positioning of the hall element. 
     It is yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can communicate with a rotating body to quantitatively detect each position of the rotating body. Linear analog measurements are converted into high-resolution digital signals using an analog-to-digital converter. 
     It is yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can eliminate problematic limited life and electric sparks that can occur due to mechanical wear. The present invention also reduces the number and size of parts, and reduces the manufacturing cost. In addition, by using a non-contact type photocoupler in present invention to replace the contact type switch used in conventional type of potentiometer electrical contact damage is eliminated. 
     It is still yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can provide accurate output values with high linearity and low hysterises so that a stable output signal can be guaranteed even during unstable power supply. This avoids electrical noise associated with extreme operating conditions such as temperature change, power source noise, noise due to amplification, electric motor, compressor, dust, moisture, and vibration. 
     It is further another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can output both analogue and digital signals with the same product and can operate two or more signal switches in various rotary positions. This achieved by the use of a microprocessor (e.g., modification of a microprocessor algorithm) and an analogue comparator circuit. 
     It is further another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor with an average power consumption less than 25 mA. In addition the present invention can operate three signal switches having a load capacity of 50 mA or less in various rotary positions and the actual switch value can be altered depend on the application by simple changes to the comparator circuit without the need for redesign or remanufacture associated with normal contact type. 
     Accordingly, a less current consuming non-contact type 2-channel rotary positioning sensor a housing with a receipt seat formed on the bottom, a cover with sensor mounting holes and through hole for covering the housing, a rotating body whose one end seats on the receipt seat of the housing and whose flange in the middle is joined to the circumference of the through hole of the cover to be supported in a rotatable manner within the housing and whose top end is formed with a coupling slot, a rotary shaft whose one end is coupled with the rotating body by a coupling protuberance inserted into the coupling slot and whose other end is coupled with the rotary object to be measured, a permanent magnet inserted into the base of the rotating body, sensing bars placed in parallel around the base of the rotating body to detect the location of the permanent magnet, and a PCB placed in the housing so as to join with the sensing bars by interposing one or more hall element. 
    
    
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a perspective view of a less current consuming non-contact type 2-channel rotary positioning sensor of the present invention; 
     FIG. 2 is an exploded view of a rotating body illustrated in FIG. 1; 
     FIG. 3 is an exploded view of the less current consuming non-contact type 2-channel rotary positioning sensor illustrated in FIG. 1; 
     FIG. 4 is a schematic plane view of a permanent magnetic and sensing bars in accordance with the present invention 
     FIG. 5 is a graph showing the relation between voltage and angle of rotation at the rotary positioning sensor of the present invention; 
     FIG. 6 is a schematic circuit diagram of comparator circuit; 
     FIG. 7 is a block diagram in accordance with the present invention; 
     FIG. 8 is a circuit diagram for a power stable circuit of power supplying part in accordance with the present invention; and 
     FIG. 9 is a is a block diagram of 2-channel rotary positioning sensor in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, as shown in FIG. 1, a less current consuming non-contact type 2-channel rotary positioning sensor  1  according to the present invention is equipped with a rotary shaft  10  with spline formed for being joined with the object to be measured such as an engine, motor frame or pedal. The rotary shaft  10  is mounted on a housing  30  in a rotatable manner. The top of the housing  30  is covered with a cover  20 , and the rear of housing  30  has a number of protruding wires  74 . At the ends of these wires  74 , terminals of various forms not shown are inserted to be connected with connectors or wire harnesses not shown. 
     In the cover  20 , sensor mounting holes  22  are formed, which penetrate the housing  30  to couple the rotary positioning sensor  1  of the present invention with the object to be measured. At one end are formed adhesive injecting holes  26  for injecting adhesives such as silicone to prevent float of wires  74 . 
     Next, as shown in FIGS. 2 and 3, the rotary shaft  10  is joined to the rotating body  40  through a coupling protuberance  12  which is formed at the bottom thereof, and around the rotating body  40 , two sensing bars  60  and  62  are placed. A permanent magnet  50  is inserted in the bottom end base  46  of the rotating body  40 , and the sensing bars  60  and  62  sense the positioning of the permanent magnet  50  transmitted through the rotary shaft  10 . The sensing bars transmit the positioning to a PCB  70 . 
     The permanent magnet  50  is inserted in advance during insertion of plastic injecting molding of the rotating body  40 . The permanent magnet  50  is fixed securely to a base portion  46  of the rotating body  40 , and reciprocates and rotates at an angle of about  90  in a reciprocal direction by the actions of the rotating body  40  and a return spring  82 . 
     Here, at the top end head  42  of the rotating body  40  is formed coupling slot  42   a  for inserting the coupling protuberance  12  of the rotary shaft  10 . Therefore, by inserting the coupling protuberance  12  into the coupling slot  42   a  and fixing it, the rotary force of the rotary shaft  10  is exactly transmitted to the rotating body  40 . Also, a joining flange  44  is formed in the middle of the rotating body  40 . Therefore, at the same time when the top end head  42  of the rotating body  40  is inserted into the through hole  24  of the cover  20  during assembly, it is possible to support the rotating body  40  within the housing  30  in a rotatable manner, since the joining flange  44  is joined at a suitable interval between the bottom end circumference of the through hole  24  and sensor mounting holes  22 . Teeth  24 a are formed around the top of through hole  24 . 
     The permanent magnet  50  is inserted in the bottom base  46  of the rotating body  40 , and between this base  46  and the joining flange  44 , for returning to the original position the rotating body  40  rotated by the rotary shaft  10 . 
     Sensing bars  60  and  62  are placed opposite each other at a given interval at both sides of the permanent magnet  50  which are placed parallel in a manner of embracing the base  46  of the rotating body  40 . Also, at the ends of sensing bars  60  and  62  the perpendicularly extending extensions  60   a  and  62   a ,  60   b  and  62   b  respectively are formed, and in the gap between extensions  60   a  and  62   a ,  60   b  and  62   b , two hall elements  72  and  73  are placed. These hall elements  72  and  73  are joined to PCB  70 , acting the role of transmitting the displacements of permanent magnet  50  sensed through sensing bars  60  and  62 . 
     Two long slots  34  are formed lengthwise in the housing  30  forming the external appearance of rotary positioning sensor  1  where the sensing bars  60  and  62  are inserted. Between these long slots  34 , receipt seat  32  is formed where receipt protuberance  48  formed on the base  46  of the rotating body  40 , is received in a rotatable manner. Also, on the bottom of the housing  30 , fixing holes  36  are formed for fixing the PCB  70 , and at the rear end, a bottom crimp terminal  38  is formed for preventing float by crimping wires  74  together with a top crimp terminal  28  formed at the bottom end of the cover  20 . 
     For assembly, two sensing bars  60  and  62  are placed in long slots  34  of the housing  30 , and the PCB  70  is placed on the bottom of the housing  30  while hall elements  72  and  73  are placed between extensions  60   a  and  62   a ,  60   b  and  62   b  of sensing bars  60  and  62 . 
     At this time, the hall elements  72  and  73  are fixed on the bottom of the housing  30  by welding, for example. Next, the base  46  of rotating body  40  that has permanent magnet  50  inserted is placed on the receipt seat  32  of the housing  30 . At this time, between the joining flange  44  of the rotating body  40  and the base  46  is the return spring  82  wound in advance, and one end of the return spring  82  is fixed on the joining flange  44  and the other end is supported by the inner wall of the housing  30 . 
     Next, the cover  20  is placed and joined on the top of the housing  30 , while inserting a rubber O-ring  80  in the top end head  42  of the rotating body  40  to prevent inflow of water or foreign matter from outside. In this process, wires  74  are inserted and connected to the rear end of the PCB  70  between the top crimp terminal  28  of the cover  20  and the bottom crimp terminal  28  of the housing  30  to crimp them, and then adhesives such as silicone are injected through adhesive injecting holes  26  for assembly. 
     In such a state of assembly, the coupling protuberance  12  of the rotary shaft  10  is joined to to the coupling slot  42   a  formed on the top end head  42  of the rotating body  40  to complete assembly, and the rotary positioning sensor of the present invention is mounted on the object to be measured through sensor mounting holes  22 . At this time, the rotary shaft  10  is assembled in such a manner that it can rotate as a single body together with the rotating part of the object to be measured. 
     On the other hand, the base portion  46  of the rotating body  40  has an elliptical form as illustrated, so it has a structure whereby a 360-degree rotation is impossible inside the sensing bars  60  and  62 . The sensing bars  60  and  62  play a role of a stopper that prevents rotation of the base portion  46 . Namely, it prevents the base portion from moving at an angle exceeding about 90 degrees in the positive direction. Therefore, the angle of rotation in the base portion becomes smaller, and as a result, it is characterized by the ability of minimizing the air gap. 
     Next, FIG. 4 is a sketch showing a layout of the sensing bars and permanent magnet of the present invention. As shown here, the pair of sensing bars  60  and  62  is placed opposite each other across a given interval (air gap) between both ends when each pair is positioned on a straight line with both ends of the permanent magnet  50 . The hall elements  72  and  73  are placed between the upper and lower extensions  60   a  and  62   a ,  60   b  and  62   b  formed opposite each other on both ends of sensing bars  60  and  62 . Because of the placing of the hall elements, the magnetic field strength according to variation of the distance between both ends of the permanent magnet  50  (which is transmitted through the rotary shaft  10  and the rotating body  40 ), can be transmitted to the hall elements  72  and  73 . Also, since the direction of the transmitted magnetic field is changed according to the direction wherein the upper and lower surfaces of the hall elements  72  and  73  are inserted between the sensing bar extensions  60   a ,  62   a ,  60   b  and  62   b , the output signals of the sensor are outputted positive or reverse. Namely, by positioning the sensing bars  60  and  62  closer to the inside of the magnetic field that is formed by the permanent magnet assembled to the elliptical base portion  46 , the position sensor detects the changes of magnetic field by rotation of the permanent magnet, so that the sensing bars serve as sensor output. 
     Since both ends of sensing bars  60  and  62  that are embracing the permanent magnet  50 , are placed in such a manner that one magnetic field strength of the same permanent magnet  50  is transmitted to two hall elements  72  and  73  at the same point, an imbalance of the magnetic force line caused by the inconsistency of an air gap between the rotating body  40  and sensing bars  60  and  62  can be compensated. The electric signal detected at the hall element  72  is converted into digital signal by the PCB  70  before it is outputted as an output signal and a switch signal. As illustrated, it is designed to ensure the reliability of the sensor when using two hall elements, by providing two proportional and mutually complementing signals with respect to the same angle of rotation through two hall elements for the magnetic field strength of one identical permanent magnet  50 . 
     Next, FIG. 5 is a graph showing the relation between voltage and angle of rotation at the rotary positioning sensor of the present invention. In this graph, the abscissa represents an angle of rotation ( 0 ) of the permanent magnet  50  and the ordinate represents output voltage (Vs). Signals outputted from sensor  1  are shown by the graph between angle of rotation (q) and output voltage (Vs). 
     As illustrated here, we can see output voltage (Vs) is obtained in proportion to angle of rotation ( 0 ) in the rotary positioning sensor  1  of the present invention. Also, it is designed to obtain at least two switch signals at two or more given voltage potentials of output signal. At this time, it is possible to change appropriately as necessary the on-off state of the switch signal. 
     FIG. 6 is a schematic circuit diagram showing the processing of linear analogue signals by the comparators in accordance with the present invention. First, the output signal of the hall elements  72  and  73  is inputted using comparators. For the standard voltage of the comparator, Vdd voltage is used to extract three different standard voltages Vref. By using comparators  97 ,  98  and  99 , triggering signals of a given potential can be obtained as desired by the user at 5V or less. This switch can be used to control external equipment. For example, this switch capability could be used with the electromagnetic control unit (ECU) of a vehicle through the photocoupler. 
     FIG. 7 is a schematic diagram of a PCB according to the present invention. As mentioned above, the changes of the magnetic field generated from the permanent magnet rotating together with the rotating body  40  by the rotary shaft  10  are detected by a pair of sensing bars  60  and  62 . The resultant field strength detected at the sensing bars  60  and  62  is transmitted to PCB  70  by the hall elements  72  and  73  placed between the extensions  60   a  and  62   a ,  60   b  and  62   b  of the pair of sensing bars  60  and  62  in the assembled condition protruding by a given length in the unilateral direction from the unilateral portion of PCB  70 , so that the imbalance of the magnetic field generated by the eccentricity of the rotating body  40  is compensated. At this time, the instantaneous intensity of magnetic field detected in proportion to each angle of rotation of the permanent magnet  50  is amplified to high-level voltage through amplifier (AMP)  90 , before it is given as an output signal of rotary positioning sensor  1  through wires  74  via compensating circuit  91 . The given signal is inputted into the electromagnetic control unit and the comparison logic circuit  94  of the vehicle. This comparison logic circuit can send the inputted signal through the comparators  97 ,  98 ,  99  as a comparison signal at a desired voltage. 
     This signal activates the photocouplers  96 , which directly drive the connected load respectively. 
     Filter  92  located at the front end of input voltage Vref, is composed of an RC circuit, and stabilizes within ±0.1% of the voltage supplied from the electronic controller of the object to be measured (e.g., engine or electric motor) for stable supply to the integrated circuit and comparison logic circuit of the hall elements  72  and  73 , so that a stable output signal can be guaranteed even during unstable power supply. 
     The PCB  70  is equipped with an independent current circuit so that the photocoupler  96  can operate as a short-circuit switch of a high-voltage power source, separately from the hall elements  72  and  73 . 
     FIG. 8 is a circuit for supplying power to the circuit of FIG. 7, and it is designed for example, to supply power with stability from the battery of a vehicle in a volume sufficient to directly drive the load connected to photocouplers  96  respectively. The power supply portion  70  is designed with a free voltage circuit  101  that eliminates voltage pulsation from the power supplied from the battery using the regulator  100 , and blocks power source noise to convert to a stable voltage level. This circuit makes the present sensor effectively correspond to the voltage level that is different according to the vehicle applied, and also plays a role of protecting the control portions  72 ,  73  and circuit  94  of FIG. 7 from over-voltage. 
     FIG. 9 is a block diagram schematically showing the processing of signals by the present rotary positioning sensor, wherein the driving power is stabilized by supplying the outside unstable pulsating direct current power and then using the hall elements  72  and  73  to detect each displacement that changes according to the rotary displacement of the rotary shaft  10 . The detected displacement is converted to a linear analog signal and sent to the comparison logic circuit portion  95  inside the electromagnetic control unit and sensor of a vehicle for example. The signal transmitted directly to an electromagnetic control unit (ECU) of a vehicle is used to control the throttle valve of the vehicle, and the signal transmitted to the comparison logic circuit can be used to drive or stop the loads of the connected vehicle by activating each switch at a given voltage position. 
     According to the present invention as described above, it is possible to provide a semi-permanent sensor that can maintain an endurance period of more than 1,000 times in the intensity of the magnetism obtained by a 2-channel non-contact rotary displacement measuring method whereby the intensity of magnetic force is perceived according to the movement of the rotating body, and that can operate smoothly even under extreme operating conditions of a vehicle or farm machine while maintaining an exact measurement error range of ±1%. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.