GB2074379A

GB2074379A - Fluid pressure sensors

Info

Publication number: GB2074379A
Application number: GB7941613A
Authority: GB
Original assignee: Col Ven SA
Current assignee: Col Ven SA
Priority date: 1978-12-01
Filing date: 1979-03-03
Publication date: 1981-10-28
Also published as: FR2473711A1; DE2948577A1; BR7907864A; FR2473711B3

Abstract

A fluid pressure sensor for detecting a decrease of pressure in the lubrication circuit of an internal combustion engine comprises a hollow body 1 having a stem 2 externally screw-threaded for mounting the sensor in the engine block. The body 1 has an enlarged portion 5 providing an internal chamber, in which is a movable electrically conducting member 16, and which is closed by a cover 11. The conductive member 16 is movable between a first position in which it establishes electrical connection between the body 1 and the cover 11 (via a spring 21) and a second position in which it breaks that connection. An electronic circuit for use with the sensor is provided such that when the lubricant pressure falls below a predetermined minimum and/or the temperature of the lubricant rises above a predetermined maximum, a fuel control solenoid valve is operated to cut off the supply of fuel to the engine and an indicating light is energised. <IMAGE>

Description

SPECIFICATION Pressure sensor for fluids and electronic control circuits for use therewith This invention relates to a fluid pressure sensor and to electronic control circuits for use therewith.

The invention relates more specifically to a new fluid pressure sensor allowing the detection of a decrease of pressure in the lubrication circuit of internal combustion engines and with electronic control circuit arrangements for use therewith so that the decrease of pressure in the lubrication circuit, detected by the sensor, actuates visual warning means provided on the dashboard of the vehicle. This electronic control circuit arrangement may be used in combination with a temperature sensor for the lubricant of the engine.The temperature sensor does not, per se, pertain to the present invention, since it may be any temperature sensor of conventional construction which is adapted to close an electrical circuit in response to normal temperature operating conditions of the engine and open the circuit upon appearing abnormal operating conditions.

The present invention provides a fluid pressure sensor comprising a sensor body having a hollow stem externally threaded and capable of being mounted in an internally threaded aperture provided in the block of the engine, said aperture being in communication with the lubricant in said lubrication circuit of the engine, an enlarged portion internally forming a chamber capable of receiving an electronic control moving member, and a cover portion having an aperture communicating with the atmosphere and a radially projecting peripheral flange retained by a peripheral upper edge of said enlarged portion inwardly bent so as to fasten said peripheral flange with the interposition of electrically isolating rings so that said enlarged portion and said cover portion will be electrically isolated one from the other, said electric control moving member being electrically conductive and arranged so as to be axially slideable within said chamber and being associated with a fluid sealing ring of electrically isolating material, the electric control moving member being capable of moving from a first position in which it establishes electrical continuity between said enlarged portion and said cover portion and a second position in which it breaks said electrical continuity, and an electrically conductive spring arranged between said electric control moving member and said cover portion biasing said moving member towards said first position in the absence of fluid pressure within said hollow stem, and said moving member sliding towards said second position against the force of said spring when submitted to fluid pressure in said hollow stem.

The above mentioned sensor may optionally have an auxiliary calibrating spring one end of which engages stop means provided within the hollow space of the bottom portion of said stem, the other end engaging an electrically isolating member associated with the bottom face of said moving member.

The sensor may also be provided with filter means provided in the bottom porton of said hollow stem and capable of preventing the entrance of foreign matter into the hollow space of said stem.

The sensor may have also means defining a foreign matter collector space within the hollow bottom end of said stem, the upper portion of said means defining a conical seat capable of receiving an electrically conductive member projecting from the bottom face of said moving member and capable of establishing electrical contact with said conical seat when said moving member is in said first position.

The electronic control circuit arrangement includes electrically connected in series, a lubricant pressure sensor according to the present invention, a lubricant temperature sensor of conventional design and a fuel control solenoid valve, each of said sensors being capable of closing an electrical return to ground in response to a decrease of the lubricant pressure below a minimum predetermined value and/or in response to an increase of the lubricant temperature above a maximum predetermined value, respectively, energizing said fuel control solenoid valve and cutting the feeding of fuel to the engine.

The circuit arrangement also comprises control means controlling three display lights, energizing a first of said display lights of a first colour (for example blue) when both sensors maintain opened their contacts, said fuel control solenoid valve thus being de-energized allowing the flow of fuel towards said engine, the first display light thus indicating normal operating conditions of the engine and the other two display lights (for example red and yellow) remaining turned off and when at least one of said sensors closes the electrical return to ground, said control means turns on a second display light of a second colour (for example red) while the other two display lights remain turned off.The same control means, when detecting an accidental and undesired interruption of the electrical connections of the fuel control solenoid valve and/or of the electrical connections of the pressure and/or the temperature sensors, energizes the third display light of a third colour (for example yellow), the two other display lights remaining turned off.

According to another embodiment of the electronic control circuit arrangement, it comprises a multivibrator device capable of producing the intermittent turning on and off of said third display light.

In the accompanying drawings, Fig. 1 shows a vertical diametrical cross section of one construction of a fluid pressure sensor embodying the present invention, Figure 2 is a schematic diagram of a first form of an electronic control circuit for use with a fluid pressure sensor embodying the present invention; Figure 3 is another arrangement of electronic circuitry which can be used with a fluid pressure sensor embodying the present invention; Figure 4 is an electronic circuit diagram of a form of circuit more simple than that shown in 'Fig. 3; Figure 5 is an electronic circuit diagram of a more complete circuit than that shown in Figs. 3 and 4;; Figure 6 is a vertical cross-section of a further form of fluid pressure sensor embodying the present invention, and Figure 7 is an electronic circuit diagram of a preferred form of the circuit shown in Fig. 3 incorporating a multi-vibrating device for controlling the luminous indicators.

In Fig. 1 of the drawings the following reference numerals indicate the following parts: 1 shows a mounting body 2 is a lower extension 3 is an actual passage 5 is the upper part of the body 1 which forms a cover 6 is a stepped portion in the interior of the upper part 5, 7 is a second step portion of the part 5 8 is a flange or rim at the outer end of the body 5 9 is a sealing member or washer 10 its a flange 11 is a bell shaped cover on which the flange 10 is a part 1 2 is the bell shaped portion of the cover 11 1 3 is a cylindrical portion forming part of the member 11 which constitutes one of the electrical contacts for the sensor 14 is the axial passage in the portion 1 3 1 5 is a screw threaded porton inside the axial passage 3 1 6 shows the end 1 6 of a regulator introduced into the axial section 1 7 shows the axial screw threading on the end 1 6 1 8 is an axial passage in the end 1 6 1 9 is a projection of smaller diameter than the main part 1 6 and serves as a seat for one end of a helical spring 20 is a helical spring 21 is the movable element of the sensor 22 is a flat horizontal bottom portion of 21 23 is a peripheral cylindrical portion of 21 24 is a peripheral rebated groove in 23 25 is a ring of electrically insulating material 26 is a portion also of electrically insulating material which has a base 27.A projection 28 of the part 26 serves as a seat for one end of the spring 20.

29 is a second helical compression spring Fig. 2 30 is a source of electric potential comprising 1 2 and 24 volt batteries 31 is a positive terminal and 32 the negative terminal which is ultimately connected to the earth 33 34 is a fixed contact 35 is a movable contact of the switch. A second fixed contact 36 of the switch is connected to the fixed contacts 37 of a pulsating interrupter which is normally closed which has a moving contact 38, a second fixed contact 39 of the interrupter is connected to one of the terminals 40 of an electro magnetic valve 41 which is of solenoid type 42 is the other terminal of the valve 41 which is connected to the fixed terminals 43 of a conventional temperature sensor which has a movable contact 44 and fixed contact 45. A fixed contact 45 is connected to earth. The same terminal 42 is also connected to the projection 1 3.

The terminal 42 is connected to the end 46 of a resistor 47, the end 48 of which is connected to the end 49 of an indicating lamp, for example a blue lamp 50 the other terminal 51 of which is connected to earth. The end 52 of the resistor 53 is connected to the fixed contact 39 of the interrupter 38 whereas the other end 54 of the resistor is connected to one of the ends 45 of an indicating lamp, for example a red lamp 56 of which the other end is connected to the end 46 of a resistor 47 and to the terminal 47 of the electric valve 41.

57 is a line indicating an indicator panel of which the interrupter 38, the lamps 50 and 56 and the resistors 47 and 53 form part.

In Fig. 3 there is shown a circuit which is substantially similar in operation to that of Fig. 2.

The positive terminal 31 of the supply of potential 30 is connected to one of the fixed contacts 34 of a general interrupter 35, the other contact 36 of which is connected to a first fixed contact 37 of a pulsating interrupter 38, the second fixed contact of which is connected to one of the terminals 40 of a electro valve 41, the other terminal 42 of the electro valve is connected simultaneously to one of the terminals 43 of a temperature sensor which includes a moving contact 44 and to one of the terminals 1 3 of the fluid pressure sensor embodying the invention which has a movable contact 21. The other terminals 45 and 2 of the sensors are connected to the negative terminal 32 of the potential supply 30.The positive terminal 31 is connected through the interrupters 35 and 38 to one of the ends of a resistor 59, the other end of which is connected to the base electrode 60 of a transistor 61. The base electrode 60 is in turn connected to the emitter electrode 62 through a resistor 63 and the emitter electrode 62 is also connected to the terminal 42 of the electric valve 41 and to the terminals 43 and 1 3 of the sensors. The emitter electrode 62 is thus connected to earth 33 through the series resistors 64 and 65. The collector electrode 66 of the transistor 61 is connected to the positive terminal 41 of the spy potential 30 through a red indicating lamp 56, a resistor 53 and the interrupters 38 and 35.A second transistor 37 has its base electrode 68 connected to the collector electrode 66 of the transistor 61 through a resistor 69 and to the negative terminal 32 of the supply of potential 30 through a resistor 68'. The omitter electrode 70 is connected to the negative terminal 32 and its collector electrode 71 is connected to the positive terminal 31 of the supply of potential 30 through a yellow indicator lamp 72, a resistor 73 and the interrupters 35 and 38. A third transistor 74 has its base electrode 75 connected to the junction of the resistors 64 and 65. Its emitter electrode 76 is connected to the negative terminal 32 of the potential supply.The collector electrode 77 of the transistor 74 is connected by one part to the base electrode 68 of the transistor 67 through a resistor 78 and for the other part to the terminal 31 through a blue indicator lamp 50, a resistor 47 and interrupters 35 and 38.

Fig. 4 shows in diagrammetric form another circuit which is more simple than that shown in Fig. 3. In Fig. 4 the source of potential 30 has its riegative terminal 32 connected to earth 33 whereas its positive terminal 31 is connected to one of the fixed contacts 34 of an interrupter 35, the other contact 36 of which is connected to one of the fixed contacts 37 of pulsating interrupter 38, the other fixed contact 39 of which is connected to the emitter electrode 79 of a transistor 80. The base electrode 81 is for the one part connected to the emitter electrode 79 through a resistor 82 and for the other part, through a further resistor 83, to the terminals 31 and 43 of the temperature sensors 21 and 24: The other terminals 2 and 45 of the sensors are connected to the negative terminal 32 of the supply of potential 30.One of the terminals 42 of the winding of excitation of the electro valve 41 is connected to the negative terminal 32 of the source of potential 30. The other terminal 40 is connected to the collector electrode 84 of the transistor 80. A first blue indicating lamp 50 is connected for the one part to the positive terminal 31 of the source of potential 30 through the interrupters 35 and 38 and for the other part to the collector electrode 84 of the transistor 80 and to the terminal 40 of the electro valve 41 to a resistor 85. A second red indicator lamp 56 is connected on the one hand to the collector electrode 84 of the transistor 80 and on the other hand to the negative terminal 32 of the source of potential 30.

Fig. 5 shows a further form of the circuitry for controlling the fluid pressure sensor. In Fig. 5 a source of potential 30 has a positive terminal 31 and a negative terminal 32, the latter of which is connected to earth 33. The positive terminal 31 is connected to one of the fixed contacts of a switch or interrupter 35, the other fixed contact 36 of which is connected to the fixed contact 37 of a pulsating interrupter 38. The other fixed contact 39 is connected to the base electrode 37 of a transistor 88 through a resistor 89. The collector electrode 90 is connected to the fixed contact 39 of a pulsating interrupter 38 through a blue indicating lamp 50 and a resistor 47.The base electrode 87 is connected through a resistor 91 to one of the terminals 42 of the exciter winding of an electro valve 41, the other terminal 40 of the electrode valve 41 is connected to the emitter electrode 92 of the transistor 98. The base electrode 87 is connected through a resistor 93 and a resistor 94 to the base electrode 95 of the transistor 96.

The base electrode 95 is connected to the emitter electrode 97 of the said transistor through a resistor 98 and the collector electrode 99 is connected to the emitter electrode 92 of the transistor 88. The emitter electrode 97 is connected to the positive terminal 31 of the source of potential 30 through switches 38 and 35. At the junction, represented by the conductor 100 between the resistors 34 and 94 are respective connection terminals 31 and 42 of the pressure sensor and temperature sensor. The junction 101 between the emitter electrode 92 of the transistor 88 and the collector electrode 99 of the transistor 96 are connected to the base electrode 102 of a transistor 103 through a resistor 104 and the emitter electrode 105 is connected to the base electrode 102 through a resistor 106 and directly to the negative terminal 32 of the supply of potential 20.The collector electrode 107 is connected to the positive terminal 31 of the supply of potential 30 through a red indicator lamp 56, a resistor 53 and the swiches 38 and 35. A transistor 108 has its base electrode 109 connected to the collector electrode 90 of the transistor 88 through a resistor 11 0, to the negative terminal 32 of the source of potential 30 through a resistor 11 and to a collector electrode 107 of the transistor 103 through a resistor 11 2. The emitter electrode 11 3 is connected directly to the negative terminal 33 of the supply of potential 30. The collector electrode 114 is connected to the positive terminal 31 of the supply of potential 30 through a yellow indicator lamp 72, a resistor 73 and the switches 38 and 35.

Fig. 6 shows a preferred form of the fluid pressure sensor. In Fig. 6, 11 5 is a filter for preventing the entry of extraneous material into the interior space 11 6. 11 7 is an element which comprises a tubular portion 118 and an enlarged portion 11 9 of conical interior shape as shown at 120. 22' is a movable element which has on its lower part a projection 1 21 which is circular in transverse section. 122 is the lower interior part of the bell shaped member 123.

This makes a secure electrical contact and at the same time provides a direct passage in the diametrical direction which connects the bottom of the bell shaped member 1 23 with the space 1 24 in order to prevent the compression of air in this part of the element 22' when in the lifted position. This embodiment is advantageous in permitting a more simple arrangement which does not require the spring 20 present in the above described forms of the invention.

In Fig. 7 there is a further electric diagram of a circuit for controlling the fluid pressure sensor which is similar to that shown in Figs. 3 to 5. The difference between what is shown in Fig. 7 and which is shown in Figs. 3 and 5 lies in that it includes a multivibrator which comprises the transistors 1 26 and 1 27 which are provided in a conventional multivibrator circuit and which in this example control the yellow indicator, for example, an LED indicated at 1 28 instead of the direct control by the transistor 67 of Fig. 3 and the transistor 108 of Fig. 5. The multivibrator makes the indication of the lamp 1 28 intermittent instead of continuous.Other differences between the arrangements of Figs. 3 and 5 on the one hand and Fig. 7 on the other hand is that the entry of the electronic portion of the control is in the case of Fig. 7 before the pulsating interrupter 38 with the addition of a fuse 129, instead of after the interrupter 38. In this manner the lighting of the yellow lamp is caused in case of a failure in the operation of the interrupter 38 or of the fuse 1 29.

Typical electrical characteristics for the components of the circuits.

FIG. 2 Reference No. Part Characteristics 21 Pressure Sensor Simple, unipolar 30 Potential Supply 24 V (12V) 35 General switch for ignition Simple, unipolar 38 Pulsating interrupter Simple, unipolar 41 Electric valve Dependent on the fuel valve.

44 Temperature sensor Simple, unipolar (conventional) 47 Resistor 3302-LED.120053 (100 S2) (LED.680 2) 50 Lamp (yellow) 24 V, 2 W-LED.20 mA.

53 Resistor 100 S3-LED.1200 S1 (LED.680 ) 56 Lamp (red) 24 V, 2 W-LED.20 mA FIG. 3 21 Pressure Sensor Simple, unipolar 30 Potential supply 24 V (12 V) 35 General ignition switch Simple, unipolar 38 Pulsating interrupter Simple, unipolar 41 Electric valve Dependent upon the fuel valve 44 Temperature Sensor Simple, unipolar (conventional) 47 Resistor 270 -LED.1200 # (LED.680 #) 50 Lamp (blue) 24 V, 2 W-LED. 20mA 53 Resistor 270#-LED.1200# (LED.680 & ) 56 Lamp (red) 24 V, 2 W-LED.2OmA 59 Resistor 2.2O0-LED.2.200 (680 #)-(LED.680#) 61 Transistor Texas 2A3726 63 Resistor 68 & (47 #) 64 Resistor 2.200 # (680 #) 65 Resistor 68 # (47 52) 67 Transistor Texas 2A-3726 68 Resistor 56 # 69 Resistor 2.700 # (1.200 72 Lamp (yellow) 24 V, 2 W-LED.20 mA 73 Resistor 270 S2-LED.1200 # (LED.680 #) 74 Transistor Texas 2A3726 78 Resistor 2.700 # (1.200 53) FIG. 4 21 Pressure sensor Simple, unipolar 30 Potential supply 24 V (12 V) 35 General ignition switch Simple, unipolar 38 Pulsating interrupter Simple, unipolar 41 Electrovalve Dependent on the fuel valve 44 Temperature sensor Simple, unipolar (conventional) 50 Lamp (blue) 24 V, 2 W-LED.20 mA 56 Lamp (red) 24 V, 2 W-LED.20 mA 80 Transistor Texas TIP 34 82 Resistor (3.9 #) 83 Resistor 47 # (22 #) 85 Resistor 270 S2-LED.1200 # (100 #)-(LED.680#) 86 Resistor 100 #-LED.1200 A (LED.680 #) FIG. 5 21 Pressure sensor Simple, unipolar 30 Potential supply 24 V (12 V) 35 General ignition switch Simple, unipolar 38 Pulsating interrupter Simple, unipolar 41 Electro-valve Depends on the fuel valve 44 Temperature sensor Simple, unipolar (conventional) 47 Resistor 270 -LED.1200 Q (LED.680 52) 50 Lamp (blue) 24 V, 2 W-LED.20mA 53 Resistor 270 #-LED. 1200 # (LED.680 Q) 56 Lamp (red) 24 V, 2 W-LED.20 mA 88 Transistor Texas 2A3726 89 Resistor 2.700 S2 (1.200 S3) 91 Resistor 56 Sa 93 Resistor 2.700 u (1.200 Q) 94 Resistor 47 S2 (22 ) 96 Transistor Texas TIP 34 98 Resistor 8 Q (3,9 ) 103 Transistor Texas 2A3726 104 Resistor 2.200 S2 (680 ) 106 Resistor 68 S2 (47 s2) 108 Transistor Texas 2A3726 110 Resistor 2.700 S2 (1.200 61) 111 Resistor 56 u 112 Resistor 2.700 a (1.200 ) The values in brackets relate to the case in which there is used a potential supply 30 of 12 V.

Claims

1. A fluid pressure sensor comprising a sensor body having a hollow stem externally threaded capable of being mounted in an internally threaded aperture provided in the block on an engine, said aperture being in communication with the lubricant of the lubrication circuit of the engine, an enlarged portion forming an internal chamber housing an electric control movable member, and a cover portion having an aperture communicating with the atmosphere and a radially projecting peripheral flange retained by a peripheral upper edge of said enlarged portion, inwardly bent so as to fasten said peripheral flange with the interposition of electrically isolating rings so that said enlarged portion and said cover portion will be electrically isolated one from the other, said electric control movable member being electrically conductive and arranged so as to be axially slideable within said chamber and being associated with a fluid sealing ring of electrically isolating material, the electric control movable member being capable of moving from a first position in which it establishes electrical continuity between said enlarged portion and said cover portion and a second position in which it breaks said electrical continuity, and an electrically conductive spring arranged between said electrical control movable member and said cover portion biasing said movable member towards said first position in the absence of fluid pressure within said hollow stem, and said movable member sliding towards said second position against the force of said spring when submitted to fluid pressure in said hollow stem,

2.A fluid pressure sensor according to claim 1, having an auxiliary calibrating spring arranged between longitudinally adjustable stop means provided in the bottom portion of said hollow stem and engaging an electrically isolating member associated with the bottom face of said movable member.

3. A fluid pressure sensor according to claim 1, having filter means provided in the end portion of said hollow stem and capable of preventing the entrance of foreign matter into the hollow space of said stem.

4. A fluid pressure sensor according to claim 1, having means defining a foreign matter collector space within the hollow bottom end of said stem, the upper portion of said means defining a conical seat capable of receiving and electrically conductive member projecting from the bottom face of said movable member and capable of establishing electrical contact with said conical seat when said movable member is in said first position.

5. An electronic control circuit arrangement for use with a fluid pressure sensor of the preceding claims, said circuit arrangement comprising, electrically connected in series, said lubricant pressure sensor a lubricant temperature sensor and a fuel control solenoid valve, each of said sensors being capable of closing an electrical return to ground in response to a decrease of the lubricant pressure below a minimum predetermined value and/or in response to an increase of the lubricant temperature above a maximum predetermined value, respectively, energizing said fuel control solenoid valve and cutting the feeding of fuel to the engine, or deenergizing said fuel control solenoid valve under normal operating conditions, control means controlling three display lights, energizing a first of said display lights of preferably a first colour when both sensors maintain opened their contacts, said fuel control solenoid valve thus being de-energized allowing the flow of fuel towards said engine, the first display light thus indicating normal operating conditions of the engine and the other two display lights remaining turned off, and when at least one of said sensors closes the electrical return to ground said control means turns on a second display light of preferably a second colour while the other two display lights remain turned off, and said control means, when detecting an accidental and undesired interruption of the electrical connections of the fuel control solenoid valve and/or of the electrical connections of the pressure and/or temperature sensors, energizes the third display light of preferably a third colour, the other two display lights remaining turned off.

6. An electronic control circuit arrangement according to claim 5 comprising a multivibrator device connected between said control means and said third display light and being capable of producing the intermittent turning on and off of said third display light.