| 1. | A circuit card for a sensing device, comprising an electrically insulating substrate and a pattern of resistor material on said substrate defining first and second variable resistors in parallel arrangement of a voltage output circuit that produces a voltage output representative of a sensed value. |
| 2. | The card of claim 1 wherein each variable resistor is connected to multiple wiped conductive contacts that are disposed on said substrate and are offset or staggered from those of the other variable resistor in a direction of movement of a wiper contact such that the wiper contact rides upon one wiped contact and then two offset wiped contacts, or vice versa, as the wiper contact moves in said direction. |
| 3. | The card of claim 2 wherein there are three resistance values for any two wiped contacts that are closed by said wiper contact. |
| 4. | The card of claim 2 wherein said wiped contacts comprise conductive strips having spaced apart facing ends that are offset in said direction. |
| 5. | A circuit card for a fluid pressure sender device, comprising an electrically insulating substrate and a pattern of resistor material on said substrate defining first and second variable resistors in parallel arrangement of a voltage output circuit that produces an analog voltage output representative of fluid pressure. |
| 6. | The card of claim 5 wherein each variable resistor is connected to multiple wiped conductive contacts that are disposed on said substrate and are offset or staggered from those of the other variable resistor in a direction of movement of a wiper contact such that the wiper contact rides upon one wiped contact and then two offset wiped contacts, or vice versa, as the wiper contact moves in said direction. |
| 7. | The card of claim 6 wherein there are three resistance values for any two wiped contacts that are closed by said wiper contact. |
| 8. | The card of claim 6 wherein said wiped contacts comprise conductive strips having spaced apart facing ends that are offset in said direction. |
| 9. | A fluid pressure sender device comprising a wiper contact that moves in a direction in response to changing fluid pressure and a circuit card comprising an electrically insulating substrate and a pattern of resistor material on said substrate defining first and second variable resistors in parallel arrangement in a voltage output circuit that produces an analog voltage output representative of fluid pressure. |
| 10. | The device of claim 9 wherein each variable resistor is connected to multiple wiped conductive contacts that are disposed on said substrate and are offset or staggered from those of the other variable resistor in a direction of movement of a wiper contact such that the wiper contact rides upon one wiped contact and then two offset wiped contacts, or vice versa, as the wiper contact moves in said direction. |
| 11. | The device of claim 9 wherein there are three resistance values for any two wiped contacts that are closed by said wiper contact. |
| 12. | A oil pressure sender device for an internal combustion engine of a motor vehicle, comprising a wiper contact that moves in a direction in response to fluid pressure changes and a circuit card comprising an electrically insulating substrate and a pattern of resistor material on said substrate defining fist and second variable resistors in parallel arrangement of a voltage output circuit that produces an analog voltage output representative of fluid pressure. |
| 13. | The device of claim 12 wherein each variable resistor is connected to multiple wiped conductive contacts that are disposed on said substrate and are offset or staggered from those of the other variable resistor in a direction of movement of a wiper contact such that the wiper contact rides upon one wiped contact and then two offset wiped contacts, or vice versa, as the wiper contact moves in said direction. |
| 14. | The device of claim 12 wherein there are three resistance values for any two wiped contacts that are closed by said wiper contact. |
| 15. | The device of claim 14 wherein said wiper contact is connected to a piston carried on a rolling diaphragm subjected to engine oil pressure fluctuations. |
| 16. | A method of improving resolution of a sensing device having a wiper contact that moves in a direction in response to changes in a parameter, comprising moving the contact upon a pattern of resistor material on a substrate defining first and second variable resistors in parallel arrangement of a voltage output circuit to produce an analog voltage output representative of change in the parameter. |
| 17. | The method of claim 16 wherein said contact moves upon multiple first and second wiped conductive contacts connected to said first and second variable resistors with the first wiped contacts being offset or staggered from the second wiped contacts such that the wiper contact rides upon one wiped contact and then two offset wiped contacts, or vice versa, as the wiper contact moves in said direction. |
| 18. | The method of claim 17 wherein there are three resistance values for any two wiped contacts that are closed by said wiper contact. |
BACKGROUND OF THE INVENTION Oil pressure sender devices are in use for sensing oil pressure in an internal combustion engine and providing an analog voltage output representative of engine oil pressure to an oil gauge or a motor vehicle on-board computer unit.
For example, U. S. Patent 5 483 835 describes an oil pressure sender device having a flexible rolling diaphragm that communicates to a wet oil pressure cavity of the sender device subjected to oil pressure of the engine and a dry circuit card cavity in which an electrically insulative circuit card is disposed having a pattern of resistor material thereon to define variable resistors arranged in series in a pressure sensing circuit that provides the analog voltage output.
The rolling diaphragm carries a piston for movement in the dry circuit card cavity and on which piston a pair of electrical contact fingers are disposed so to move across the variable resistors on the circuit card in a manner that varies resistance and thus voltage output of the pressure sensing circuit.
An object of the present invention is to provide an improved sensing circuit card for a sensing device and having a voltage output of improved resolution.
Another object of the present invention is to provide an improved pressure sensing circuit card for a fluid pressure or other sender device and having analog voltage output of greater resolution.
SUMMARY OF THE INVENTION The present invention provides a circuit card for a sensing device wherein the circuit card includes a pattern of resistor material thereon defining first and second variable resistors in parallel arrangement of a voltage output circuit that produces an voltage output representative of a sensed value. Each variable resistor is connected to multiple wiped conductive contacts that are offset or staggered from those of the other variable resistor in a direction of movement of a wiper contact that is responsive to movement of a rolling diaphragm from a sensed parameter or variable such as, for example only, fluid pressure, linear or rotary motion, liquid level, displacement and the like. In this way, the wiper contact closes/opens the wiped contacts of the variable resistors in a manner that increases voltage resolution of the sensing circuit. For example, in an illustrative embodiment of the present invention, there are three resistance values for any two wiped contacts that are closed by the wiper contact to thereby increase resolution of the voltage output of the sender device.
The above objects and advantages of the present invention will become more readily apparent from the following drawings taken with the detailed description of the invention.
DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal sectional view of an oil pressure sender device in accordance with an embodiment of the invention.
Figure 2 is a longitudinal sectional view of an oil pressure sender device viewed in a direction 90 degrees to Figure 1.
Figure 3 is an elevational view of the pressure sensing circuit card in accordance with an embodiment of the invention.
Figure 4 is a rear elevational of the pressure sensing circuit card in accordance with an embodiment of the invention.
Figure 5 is a schematic electrical circuit diagram of the voltage output circuit including a pair of variable resistors in a parallel arrangement as a voltage divider.
Figure 6 is a schematic diagram of the voltage output circuit including a fixed resistor representation of variable resistors.
DESCRIPTION OF THE INVENTION Although an embodiment of the invention is described in detail herebelow with respect to an oil pressure sender device, it is not limited thereto and can be practiced with respect to various sensing devices including, but not limited to, pressure sensors, liquid level sensors, linear motion sensors, rotary motion sensors, displacement sensors and other sensors to sense a change in a parameter or variable (e. g. liquid level, motion, pressure, displacement, etc.). For purposes of illustration and not limitation, the invention can be used in connection with motor vehicles, such as automobiles, trucks, etc. for example in throttle position sensors, coolant level sensors, oil level sensors, air conditioning pressure sensors, oil pressure sensors, fuel tank vapor pressure sensors, and fuel level sensors. Those skilled in the art will appreciate that the invention is not limited to these service applications and that the invention can be used in connection with a variety of sensing devices.
Referring to Figures 1-4, an oil pressure sender device 10 for use to sense oil pressure in an internal combustion engine of a motor vehicle, such as automobile, truck, etc., is shown. The sender device 10 includes a sender base structure 12 having a metal base 14 and a sender body structure 16 that is secured to the base 14 by a crimped annular edge 20 of base 14. The oil pressure sender device 10 further includes interior components such as damper plug 22 that is recessed within a fluid passageway or bore 24 which together define a plurality of stacked volume chambers 26a-26d, a rolling diaphragm assembly 28 which includes a reinforced diaphragm 29, a piston 30 which has integrally molded thereto, wiper contacts 32, 34, a spring 36 that partially nests within the piston 30, a retainer shoulder 37 that provides an upper surface for the spring 3 to bias against, and an electrically insulative circuit card 50 pursuant to an embodiment of the present invention to be described below. The piston 30 carries wiper contacts 32, 34. The contact 32 includes contact fingers 32a, 32b. The contact 34 includes similar contact fingers 34a (one shown). The end of circuit card 50 inserts between a single electrical clip 40a and a pair of electrical clips 42, 42a that engage opposite sides of the circuit card 50 and that are preferably integrally molded to the body 18. The clips 40a, 42, 42a are electrical extensions of respective connector pins 40b, 42b, 42c that extend up through and out of the body structure 16.
Connector pin 40c is a dummy pin unconnected to an electrical clip. Certain of the above described features of the oil pressure sender device 10 are described in U. S. Patent 5 483 835, the teachings of which are incorporated herein by reference.
In a service application for a liquid level sensor (e. g. fuel sensor), a liquid level float movable with the level of the liquid (e. g. liquid fuel) would be connected to wiper contact 32, 34 of the sensing device via a fluid level arm or other linkage. In a service application for a motion sensor, a member that moves would be connected to wiper contact 32, 34 of the sensing device via a suitable linkage. In a service application for a displacement sensor, a member that is displaced would be connected to wiper contact 32, 34 of the sensing device via a plunger or suitable linkage. The wipers 32, 34 and fingers 32a, 34a thereby would be caused to move relative to the variable resistors 80, 90 described below. In service applications other than pressure sensing, the diaphragm 29 and other related components may be omitted.
The oil pressure sender base structure 12 has at its base the fluid inlet passageway 24 that receives pressurized fluid in the direction indicated by arrow P. The source of the pressure P may be from an oil inlet line (not shown) or by threading the base of the oil pressure device 10 into the block 44 (partially shown in Figure 2) of the motor vehicle internal combustion engine.
Those skilled in the art will appreciate that the sender device 10 can be employed to sense any fluid pressure.
As mentioned, an oil pressure sender device of the general type described above having certain components described above, with the exception of the circuit card 50 pursuant to the invention, and its calibration are described in U. S. Patent 5 483 835, the teachings of which are incorporated herein by reference.
Referring to Figure, 3 and'., a circuit card 50 in accordance with an embodiment of the present invention is shown including on one side thereof, resistor material 60 and conductive material 62 disposed on a ceramic (or other electrical insulating material) circuit card substrate 63 to form a portion of a voltage output circuit 70. In particular, the resistor material 60 is present in patterns forming variable resistors 80, 90 and a fixed resistor 92 of the circuit 70. Resistors 80, 90 each may comprise a 2K Ohm variable resistor, while fixed resistor 92 can comprise a 110 Ohm fixed resistor. The variable resistors 80, 90 are illustrated schematically in Figure 5 in a parallel resistor arrangement as a voltage divider of the circuit 70. The conductive material 62 is present in patterns to form conductive leads 72, 74 connected to the variable resistors 80, 90 and conductive strip-shaped contacts C through Z and AA through EE.
The conductive leads 72, 74 define terminals A and B where terminal A is a ground terminal connected to electrical clip 42 and terminal B is an applied voltage terminal (e. g. 5 volts DC is applied to terminal B) connected to clip 42a.
Referring to Figure 4, circuit card 50 is shown including on a rear or back side thereof, a conductive material 64 on ceramic substrate 63 to form a wiped output contact 94 of the voltage output circuit 70 for output signal.
The resistor material 60 typically comprises a rare earth oxide, such as Ru203, or other suitable resistor material. The conductive material 62, 64 typically can comprise a conventional palladium silver alloy or other suitable conductive material. The resistor material 60 is deposited on the substrate 63 by conventional thick film techniques. The conductive material 62, 64 is deposited on the substrate 63 by conventional thick film techniques. The circuit card 63 typically comprises alumina but other suitable electrical insulating ceramic or other materials can be used in practice of the invention. The invention is not limited to any particular materials for the resistor material 60, conductive material 62, 64, or substrate 63.
In accordance with an embodiment of the present invention, switch contacts C, D, F, H, J, L, N, P, R, T, V, X, Z, BB, and DD connected to variable resistor 80 are vertically offset or staggered in Figure 3 relative to the switch contacts E, G, I, K, M, O, Q, S, U, W, Y, AA, CC, and EE connected to variable resistor 90. The offset or stagger of the contacts occurs in the direction of movement of the contact 32 upwardly or downwardly in Figure 3 in response to oil pressure changes that cause the diaphragm 29 and piston 30 carried thereon to move. In particular, during operation of the internal combustion engine, the fingers 32a, 32b of the wiper contact 32 ride upon the conductive strip-shaped contacts C through Z and AA through EE.
The contact 32 includes multiple (e. g. 3) fingers 32a that ride upon contacts C, D, F, H, J, L, N, P, R, T, V, X, Z, BB, and DD and multiple (e. g. 3) fingers 32b that ride upon contacts E, G, I, K, M, O, Q, S, U, W, Y, AA, CC, and EE.
Referring to Figure 4, the circuit card 50 is shown including on a rear or back side thereof, a conductive material 64 on ceramic card substrate 63 to form an output contact 94 of the voltage output circuit 70 for output signal via electrical clip 40a contacting therewith.
Referring to Figure 5, the variable resistors 80, 90 are shown in parallel resistor arrangement in the circuit 70 and with fixed resistor 92 of Figure 3 for purposes of illustrating the parallel resistor circuit. By use of separate variable resistors 80, 90 as described above, the resolution of the resistance and therefore the resolution of the analog voltage output of the sender device 10 is quadrupled using the same area or size of substrate 63 as used in aforementioned U. S. Patent 5 483 835. For example, referring to Figure 6, there are three resistance values for any two switch contacts SW1-SW7 (e. g. SW1 and SW2 in Figure 6). That is, when contact SW1 is closed with contact SW2 open, a resistance value of X Ohms (resistor R1) and its corresponding voltage output is provided. Closing contact SW2 with contact SW1 closed provides a resistance of Xr = [X+Y]/2 Ohms where Y Ohms is provided by resistor R2. Opening contact SW1 with contact SW2 closed would provide a resistance of Y Ohms (resistor R2) because of movement of the wiper contact 32 upwardly in Figure 3 to increase the variable resistance. The resistance presented by the formula for Xr falls at the midpoint between the values of X Ohms for resistor R1 and Y Ohms for resistor R2 ; i. e. in a hypothetical example, if X= 1 Ohm and Y = X+1 = 2 Ohms, then Xr = 1. 5 Ohms. Offsetting or staggering of the contacts C, D, F, H, J, L, N, P, R, T, V, X, Z, BB, and DD relative to contacts E, G, I, K, M, O, Q, S, U, W, Y, AA, CC, and EE in the direction of movement of wiper contact 32 as shown in Figure 3 provides means to achieve this mode of wiped contact opening and closing when the wiper contact 32 moves upwardly or downwardly relative to the wiped contacts due to oil pressure changes. Thus, as the wiper contact 32 moves upwardly in response to oil pressure changes, the fingers 32a, 32b will ride upon contact D first, then contacts D and E concurrently, then contact F, contacts F and G concurrently, and so on to provide a voltage output with greater resolution. The conductive contacts C through Z and AA through EE are offset and dimensioned in the direction of movement of the wiper contact 32 so that the wiper contact 32 rides upon one wiped contact (e. g. only contact D closed) and then two offset wiped contacts (e. g. both contacts D and E closed), then the next wiped contact (e. g. only contact F closed), and so on as the wiper contact 32 moves in the direction. The reverse wiped contact closing/opening sequence occurs when the wiper contact 32 moves in the opposite direction. The offset and dimensions of the wiped contacts are selected relative to the contact 32 to insure that the contact 32 can ride upon and engage both offset wiped contacts (e. g. D and E) as necessary to close both contacts (e. g. D and E) to operate the voltage divider formed by variable resistors 80, 90 in the manner explained above to increase voltage resolution.
Referring again to Figure 6, a fixed resistor representation of variable resistor 80 or 90 in the voltage output circuit is illustrated. In Figure 6, resistors Ri through R6 are shown only for purposes of representing a variable resistor with the number of resistors shown being arbitrarily selected. When contact SW1 is closed, the resistance value at Vmeasure (VM = voltage out) is X Ohms using the hypothetical example above and the corresponding voltage measured at Vmeasure is expressed as : Vmeasurel where Rf is fixed resistor 92.
When contact SW1 and SW2 are closed, the resistance value at measure is [X+ (X+1)]/2 Ohms using the hypothetical example above and the corresponding voltage measured at Vmeasure is expressed as : Vmeasure2 = When contact SW1 is open and SW2 is closed, the resistance value at Vmeasure is X+1 Ohms and the corresponding voltage measured at Vmeasure is expressed as : <BR> <BR> <BR> <BR> <BR> <BR> <BR> (+V - Vmeasure1) * R1<BR> <BR> measure3- Ri + R2 + R3 For purposes of illustration only, Table I sets forth voltage outputs versus fluid pressure (psi) as the contact 32 connects terminal A with different contacts C, D, etc. when a voltage of 5. 0 volts DC is applied between terminal A and terminal B in Figure 3.
TABLE I MEASURED FROM A TO: PSI VOLTS C 0.000 0 5000 D 5. 000 0. 6425 D&E 6. 375 0. 6891 E 7. 750 0. 7850 E&F 9. 125 0.8404 F 10.500 0. 9275 F&G 11. 875 0. 98681 G 13.250 1. 0700 G&H 14. 625 1. 1316 16. 000 1. 2125 H&l 17. 375 1. 2755 18.750 1. 3550 I&J 20.125 1.4191 1 21. 500 1. 4975 J&K 22.875 1. 5625 K 24. 250 1. 6400 K&L 25. 625 1. 7057 L 27.000 1.7825 L&M 28. 375 1.8488 M 29.750 1. 9250 M&N 31. 125 1. 9919 N 32.500 2. 0675 N&O 33.875 2. 1349 O 35. 250 2. 2100 O&P 36. 625 2. 2778 38. 000 2. 3525 P&Q 39. 375 2.4208 Q 40.750 2. 4950 Q&R 42. 125 2. 5637 R 43. 500 2. 6375 R&S 44. 875 2. 7066 S 46.250 2.7800 S&T 47. 625 2. 8495 T 49.000 2.9225 T&U 50. 375 2.9924 U 51. 750 3. 0650 U&V 53. 125 3.1354 V 54.500 3.2075 V&W 55. 875 3.2783 W 57. 250 3.3500 W&X 58. 625 3. 4213 X 60.000 3. 4925 X&Y 61. 375 3. 5644 Y 62.750 3.6350 Y&Z 64. 125 3. 7075 z 65. 500 3. 7775 Z&AA 66. 875 3.8506 AA 68. 250 3. 9200 AA&BB 69. 625 3. 9940 BB 71. 000 4. 0625 BB&CC 72. 375 4.1375 CC 73. 750 4.2050 CC&DD 75. 125 4. 2813 DD 76. 500 4. 3475 DD&EE 77. 875 4. 4258 EE 79. 250 4. 4900 a TOTAL 5. 0000 # In Table I and Figure 3, the variable resistors 80, 90 each are 2K Ohm and fixed resistor 92 is 110 Ohms. The output voltage was measured between terminal A and a wiped contact such as between terminal A and contact C, then between terminal A and contact D, then between terminal A and contacts D and E where the contact fingers 32a, 32b contact both contacts D and E, and so. The resolution of voltage output provided pursuant to the invention is apparent from Table I. Oil pressure values corresponding to the measured output voltages are shown in column entitled"PSI" in Table I.
Although the present invention has been described above with respect to certain detailed embodiments, those skilled in the art will appreciate that changes, modifications and the like can be made thereto within the scope of the invention as set forth in the appended claims.