JP2000321248A - Oil check sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil check sensor capable of quantitatively detecting the amount of metal powder in engine oil and eliminating the need for removing work at the time of measurement. SOLUTION: This oil check sensor 100 is provided with a coil head 10 for detection to be converted into an electromagnet by an excitation current and an oscillating/tuning circuit 30 to supply an excitation current for the coil head 10 for detection. Metal powder in engine oil is adhered to the coil head 10 for detection magnetized into an electromagnet. The oscillating/tuning circuit 30 generates a detection signal of which amplitude changes according to the inductance value of the coil head 10 for detection which changes according to the amount of the adhered metal powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oil check sensor capable of detecting the amount of metal powder in lubricating oil.

[0002]

2. Description of the Related Art Lubricating oil (hereinafter referred to as "engine oil") used for an engine of an automobile or the like contains fine metal powder generated by abrasion of parts in an engine engine with long-term use. become. If a large amount of metal powder is mixed in the engine oil, the original lubrication performance will not be exhibited, and as a result, the engine body may be damaged. Therefore, by monitoring the amount of the metal powder in the engine oil, the engine oil can be monitored. It is widely practiced to examine the degree of deterioration of the battery and use it as information for determining the timing of replacement.

[0003] Generally, the above-mentioned monitoring is performed by equipping the drain portion of the engine oil circulation system with an oil check sensor for checking the amount of metal powder in the engine oil.

FIG. 11 is a schematic block diagram for explaining the operation principle of an oil check sensor 200 using a conventional permanent magnet.

Referring to FIG. 11, oil check sensor 200 includes a sensor section 210 corresponding to a drain bolt and a detection / main body section 220.

The sensor section 210 includes a pair of permanent magnets 23.
0 and 240. The sensor section 210 is immersed in engine oil and has permanent magnets 230 and 240.
Absorbs metal pieces in engine oil by magnetic force.

[0007] The detection / main body 220 is provided with a pair of electrodes 26.
0 and 265, and a detection short circuit 270 for detecting the presence or absence of a short circuit between both electrodes. These electrodes are often also used as metal (conductor) parts such as joints constituting the oil check sensor body. The electrodes 260 and 265 and the permanent magnets 230 and 240 are integrally fixed via an insulator 250 so as to maintain a constant interval between the two magnets.

The electrode 265, the permanent magnet 230 and the electrode 2
The 60 and the permanent magnet 240 are each electrically connected. The material of the permanent magnets 230 and 240 includes the material even when the temperature becomes high due to the operating engine oil.
A substance that exhibits conductivity is selected.

[0009] Short circuit detection circuit 270 is connected to electrodes 260 and 265 by wiring 290. The short-circuit detection circuit 270 generates an abnormality detection signal when a sufficient amount of metal powder is adsorbed between the permanent magnets 230 and 240 and an electric short-circuit occurs.

That is, the oil check sensor 200
Is to detect whether the amount of metal powder in engine oil exceeds a certain level by detecting an electrical short circuit caused by metal powder adsorbed between a pair of permanent magnets attached to the sensor unit. It is.

[0011]

However, in an oil check sensor using a permanent magnet, it is only possible to judge the presence or absence of metal powder adhering to the sensor part, or to determine the degree of metal powder. The flour could not be evaluated quantitatively.

Further, since a permanent magnet is used, in order to accurately detect the amount of metal powder in the engine oil during operation of the engine, the metal powder attached to the sensor portion is removed once every measurement. Cleaning was necessary.
For this reason, the structure of the oil check sensor must be complicated in order to take the removal work into consideration.

[0013] An object of the present invention is to solve such a problem, and it is possible to quantitatively detect the amount of metal powder in engine oil and to perform a regular removal operation for cleaning. It is to provide an unnecessary oil check sensor.

[0014]

An oil check sensor according to claim 1 is an oil check sensor for detecting an amount of metal powder in lubricating oil, wherein the coil is immersed in lubricating oil and magnetized by an exciting current. Sensor means including a head;
Detecting means for generating a detection signal corresponding to the amount of metal powder attached to the coil head, wherein the detecting means generates an oscillation tuning signal which is an AC electric signal on which a DC component for supplying an exciting current is superimposed. And an oscillation tuning circuit for generating a detection signal whose amplitude changes in accordance with the inductance value of the coil head which changes according to the amount of metal powder adhering to the coil head.

[0015] The oil check sensor according to claim 2 is
The oil check sensor according to claim 1, wherein the sensor means generates a detection level signal having a DC voltage corresponding to the amplitude of the detection voltage signal,
A voltage comparison circuit is further included that compares the voltage level of the detection level signal with a predetermined reference voltage and generates an abnormality detection signal when the detection level signal exceeds the reference voltage.

According to a third aspect of the present invention, there is provided an oil check sensor, comprising:
3. The oil check sensor according to claim 1, wherein the oscillation tuning circuit generates an AC electric signal in response to an externally applied start control signal. 4.

According to a fourth aspect of the present invention, there is provided an oil check sensor, comprising:
4. The oil check sensor according to claim 3, wherein the start control signal is activated in conjunction with a power signal of an engine in which the oil check sensor is incorporated.

According to a fifth aspect of the present invention, there is provided an oil check sensor, comprising:
An oil check sensor for detecting the amount of metal powder in the lubricating oil, wherein the sensor means includes a coil head immersed in the lubricating oil and magnetized by an excitation current, and the amount of the metal powder adhered to the coil head. Detecting means for generating a detection signal, the detecting means comprising: a resonance capacitor connected in parallel with the coil head; and a reference which is an AC electric signal having a DC component and a first frequency for supplying an exciting current. An oscillation tuning signal generated by superimposing the oscillation signal on an oscillation tuning signal for supplying a resonance circuit including a resonance capacitor and a coil head; and an amount of metal powder attached to the coil head. And a phase difference detecting means for detecting a phase difference between a current and a voltage in the resonance circuit.

According to a sixth aspect of the present invention, there is provided an oil check sensor,
6. The oil check sensor according to claim 5, wherein the phase difference detection means includes a first phase detection pulse signal activated at a timing when the polarity of the AC component of the oscillation tuning signal changes, and a voltage generated in the resonance capacitor. A phase detection circuit that generates a second phase detection pulse signal that is activated at a timing when the polarity of the second phase detection pulse signal changes, and an activation timing between the first phase detection pulse signal and the second phase detection pulse signal. A phase difference measurement circuit for measuring a difference, wherein the phase difference measurement circuit generates a high frequency pulse having a second frequency higher than the first frequency, a first phase detection pulse signal, and a first phase detection pulse signal. A phase difference counting circuit that counts high-frequency pulses generated while only one of the two phase detection pulse signals is activated.

The oil check sensor according to claim 7 is
7. The oil check sensor according to claim 6, wherein the detection unit further includes an abnormality detection circuit that generates an abnormality detection signal when the count value of the phase count circuit exceeds a predetermined value.

The oil check sensor according to claim 8 is
8. The oil check sensor according to claim 5, wherein the oscillation tuning signal generating means generates an oscillation tuning signal in response to a start control signal supplied from outside.

The oil check sensor according to claim 9 is
9. The oil check sensor according to claim 8, wherein the activation control signal is activated in conjunction with a power signal of an engine in which the oil check sensor is incorporated.

[0023]

[First Embodiment] FIG. 1 is a schematic block diagram for explaining a configuration of an oil check sensor 100 according to a first embodiment of the present invention.

Referring to FIG. 1, oil check sensor 1
00 includes a sensor section 110 and a detection / main body section 120.

The sensor section 110 includes a detection coil head 10 at the tip. The detection coil head 10 is supplied with an excitation current from the oscillation tuning circuit 30 and magnetized, thereby adsorbing metal powder in the engine oil as in the case of the permanent magnet in the conventional oil check sensor 200.

The detection / main body section 120 includes the oscillation tuning circuit 30.
including. The oscillation tuning circuit 30 is activated by an externally applied activation control signal, and supplies an oscillation tuning signal (frequency fd), which is an AC electric signal with a DC component superimposed thereon, to supply an exciting current to the coil head 10 for detection. appear. The wiring 60 is a coil head 1 for detecting the oscillation tuning signal.
Transmit to 0.

The oil check sensor 100 performs detection by utilizing the fact that the inductance value of the detection coil head 10 continuously changes in accordance with the amount of metal powder adsorbed on the detection coil head 10 which has been turned into an electromagnet. Metal powder in the engine oil is quantitatively detected by a detection voltage signal that reflects a change in the amplitude of an AC electric signal corresponding to a change in the reactance X (X = ωL, ω = 2π · fd) of the coil head 10 for use.

The oscillation tuning circuit 30 supplies an oscillation tuning signal including an AC voltage component of a constant frequency to the detection coil head 10 and generates an AC component of a voltage generated in the detection coil head 10 as a detection voltage signal. Thus, the amount of metal powder attached to the detection coil head can be detected.

FIG. 2 is a conceptual diagram for explaining the measurement principle of oil check sensor 100 according to the first embodiment of the present invention.

Detection coil head 10 and oscillation tuning circuit 3
The resonance characteristics of the resonance circuit formed by the tuning capacitor included in the coil 0 vary depending on the presence or absence of metal powder attached to the detection coil head. Here, as an example, the case where the resonance frequency of the resonance circuit is reduced from the resonance frequency f1 to f2 when there is no adhesion of the metal powder to the detection coil head due to the adhesion of the metal powder will be described.

The frequency of the AC component of the oscillation tuning signal is maintained at a constant frequency fd by the oscillation circuit included in the oscillation tuning circuit. Assuming that the amplitude of the AC component of the oscillation tuning signal under this frequency without metal powder is A1,
As the resonance characteristics change due to the effect of the adhesion of the metal powder to the detection coil head and the resonance frequency decreases to f2, the signal amplitude of the AC component decreases from A1 to A2.

That is, a voltage signal including an AC component having a constant frequency is applied to the resonance circuit, and the amplitude of the AC component is changed by the change in the resonance characteristic caused by the adhesion of the metal powder to the detection coil head. The amount of metal powder attached to the head can be quantitatively grasped.

The detection / main unit 120 is provided with the oscillation tuning circuit 30.
And a detection rectifier circuit 40 that receives a detection voltage signal generated by the detection voltage signal and generates a detection level signal corresponding to the amplitude of the detection voltage signal.

The detection and rectification circuit 40 is a circuit that generates a detection level signal that is a DC voltage signal corresponding to the amplitude of the detection voltage signal that is an AC voltage signal. It is constituted by a circuit. Since the detection level signal generated by the detection and rectification circuit 40 continuously changes according to the amount of metal powder adhering to the detection coil head 10, it is necessary to quantitatively grasp the amount of metal powder in engine oil. Becomes possible.

FIG. 3 is a circuit diagram showing an example of a specific configuration of the oscillation tuning circuit 30 and the detection and rectification circuit 40.

Referring to FIG. 3, oscillation tuning circuit 30 includes a transistor Q1, a vibrator XC, resistors R1, R2, R3 and a capacitor Ca forming an oscillation circuit. The collector of transistor Q1 is connected to node Na, and the base of transistor Q1 is connected to a node to which resistors R1 and R2 connected in series between a Vdd power supply and a ground line are connected. The oscillator XC is connected between the base and the collector of the transistor Q1. The resistor R3 and the capacitor Ca are connected in parallel between the emitter of the transistor Q1 and the ground line.

The oscillation circuit constituted by these elements generates an AC signal having a constant frequency fd at the node Na.

The oscillation tuning circuit 30 further includes a node Na
And a tuning capacitor Cd connected between the power supply and the Vdd power supply. The tuning capacitor Cd is connected in parallel with the detection coil head 10, and forms a resonance circuit with the detection coil head.

With such a configuration, the tuning capacitor Cd and the detecting coil head are provided with an AC voltage signal in which a DC voltage for supplying an exciting current and an AC voltage component generated by the oscillation circuit are superimposed. Is applied.

The oscillation tuning circuit 30 further includes a control switch SW which is turned on / off in response to a start control signal and executes or stops supply of a power supply voltage to the oscillation circuit.
Thus, the oil check sensor 100 can be operated in synchronization with the start control signal.

The start control signal may be a signal which is activated at an appropriate timing from the outside. If the start control signal is linked with the start of the engine body, the amount of metal powder in the engine oil can be measured more accurately. Can be. This is because when the engine is stopped, there is a high possibility that the metal powder has precipitated in the engine oil, and this state can be automatically avoided to perform the measurement.

The detection and rectification circuit 40 includes a tuning capacitor C
d, a capacitor Cb connected between the node Na and the node Nb, a diode D1 connected between the node Nb with the direction from the node Nb to the ground line being reversed, and a detection level signal from the node Nb. The diode D2 connects between the node Nc and the ground line, with the direction toward the node Nc where the signal N is generated as a forward direction, and a capacitor Co connected between the node Nc and the ground line.

The capacitor Cb extracts a detection voltage signal which is an AC signal whose amplitude changes due to the influence of metal powder attached to the detection coil head by passing only the AC component from the voltage generated at the node Na.

When the detection voltage signal is negative, the diode D1 conducts and the capacitor Cd is charged. On the other hand, when the detection voltage signal is positive, the diode D2 conducts,
A voltage corresponding to the sum of the voltage charged in the capacitor D1 and the detection voltage signal is applied to the capacitor Co.

With such a configuration, the detection and rectification circuit 40 performs so-called voltage doubler rectification, and the capacitor Co has a voltage corresponding to the amplitude of the detection voltage signal, that is, the amount of metal powder adhering to the detection coil head. A detection level signal is generated.

The circuit configuration of the oscillation tuning circuit 30 and the detection and rectification circuit 40 shown in FIG. 3 is merely an example and does not limit the configuration of the present invention. That is, the configuration of the oscillation tuning circuit 30 may be any circuit configuration as long as the oscillation tuning signal, which is a voltage signal in which an AC component and a DC component of a constant frequency are superimposed, can be supplied to the detection coil head. Can be. Similarly, the rectification detection circuit 40 can have any circuit configuration as long as it can generate a DC voltage signal corresponding to the amplitude of the detection voltage signal as a detection level signal. It is not limited.

The detection / main unit 120 further includes a voltage comparison circuit 50 for comparing the magnitude of the output signal of the detection and rectification circuit with a predetermined threshold value.

The voltage comparison circuit 50 compares a threshold value preset as a voltage level of a detection level signal corresponding to the amount of metal powder at a level requiring replacement of engine oil with a voltage level of the detection level signal. Then, when the detection level signal exceeds this threshold, the abnormality detection signal is activated. This makes it possible to constantly monitor the deterioration state of the engine oil and perform appropriate abnormality monitoring according to the measurement result.

Further, the oil check sensor 100 employs an electromagnetized coil head for detection to adsorb metal powder in engine oil. Therefore, the supply of the excitation current is stopped, so that the oil check sensor 100 can be used for detection without special cleaning work. Metal powder adhering to the coil head can be removed.

Therefore, it is not necessary to design the oil check sensor 100 in consideration of the steady removal operation of the sensor, and the cost can be reduced by simplifying the structure of the sensor. .

Further, by further providing a circuit for stabilizing the amplitude of the AC component of the oscillation tuning signal, the detection accuracy can be more stably secured. [Second Embodiment] An oil check sensor according to the first embodiment aims to quantitatively grasp the amount of metal powder attached by utilizing the change in the amplitude of an AC signal in accordance with the change in the inductance of the coil head. However, the change in the inductance affects not only the amplitude but also the phase of the AC signal.

In the second embodiment, the change in the phase of the AC signal caused by the change in inductance according to the adhesion of the metal powder to the coil head is used to quantitatively grasp the amount of the metal powder attached. It is the purpose.

FIG. 4 is a schematic block diagram for illustrating the configuration of oil check sensor 150 according to the second embodiment of the present invention.

Referring to FIG. 4, oil check sensor 1
50 is different from the oil check sensor 100 according to the first embodiment in the configuration and operation of the detection / main unit 121.

The detection / main unit 121 includes an oscillation tuning circuit 31.
including. The oscillation tuning circuit 31 is activated by an externally applied activation control signal, and generates an oscillation tuning signal which is an AC electric signal with a DC component superimposed thereon. The wiring 60 is
The oscillation tuning signal is transmitted to the detection coil head 10.

The oscillation tuning signal is, as in the first embodiment,
A DC component for supplying an exciting current to the coil head 10 and a reference resonance signal (frequency f) which is an AC electric signal for detecting a change in inductance of the coil head 10.
d) is a signal obtained by superimposing.

The oil check sensor 150 detects the reactance X of the detection coil head 10 according to the amount of metal powder adsorbed on the detection coil head 10 which has been turned into an electromagnet.
Using the fact that (X = ωL, ω = 2π · fd) changes continuously, the metal powder in the engine oil is determined by the phase change of the resonance output signal which is an AC voltage generated in the resonance circuit including the coil head. Detection. Oscillation tuning circuit 31
Is activated by an externally applied activation control signal as in the first embodiment.

The detection / main unit 121 includes an oscillation tuning circuit 31.
It further includes a phase detection circuit 41 and a phase difference measurement circuit 51 provided for detecting a phase difference between the obtained resonance output signal and the reference resonance signal.

The phase detection circuit 41 includes a phase detection pulse PD1 for detecting a timing when the reference resonance signal changes from minus to plus, and a phase detection pulse PD2 for detecting a timing when the resonance output signal changes from minus to plus.
And generate.

The phase difference measuring circuit 51 outputs the phase detection pulse P
A timing difference between D1 and the phase detection pulse PD2 is detected, and a detection level signal indicating the amount of metal powder adhering to the coil head is generated. As will be described in detail later, in the oil check sensor 150, a detection level signal can be obtained as a digital value by performing a timing difference between the two by counting high-frequency pulses.

FIG. 5 is a block diagram for explaining the configuration of the detection / main body section 121 in more detail.

Referring to FIG. 5, oscillation tuning circuit 31 includes a resonance capacitor C connected in parallel with coil head 10.
d. The coil head 10 as an inductor and the resonance capacitor Cd form a parallel resonance circuit.

The oscillation tuning circuit 31 further includes an oscillation tuning signal generating circuit 35 for generating an oscillation tuning signal for supplying an exciting current to the parallel resonance circuit. The oscillation tuning signal is represented by the sum of outputs of a DC signal generated from the bias voltage generation circuit 36 and a reference oscillation signal (frequency fd) which is an AC signal generated from the oscillation circuit 38. The frequency fd is set near the resonance frequency of the parallel resonance circuit.

With such a configuration, an alternating current having a constant frequency fd is supplied to the parallel resonance circuit.
Under a constant frequency, the phase of the resonance output signal, which is an AC voltage generated in the parallel resonance circuit in response to the AC current, changes the inductance of the coil head and the resonance capacitor in the same manner as the amplitude change described in the first embodiment. Varies depending on the relationship with the capacitance of

FIG. 6 is a waveform diagram showing an example of a change in the resonance output signal according to the adhesion of the metal powder.

Referring to FIG. 6, the reference resonance signal is transmitted to the parallel resonance circuit as a triangular wave AC signal. In oil check sensor 150, the current phase of the parallel resonance circuit is equal to the phase of the reference voltage signal.

Since the resonance characteristic of the parallel resonance circuit changes in accordance with the change in the inductance value due to the adhesion of the metal powder to the coil head, the amplitude and the phase of the resonance output signal change.

When there is no adhesion of metal powder to the coil head, the phase delay of the voltage generated in the parallel resonance circuit under the frequency fd with respect to the current (hereinafter, also simply referred to as the phase difference).
Is φ1.

The adhesion of the metal powder to the coil head increases the inductance value of the coil head. Correspondingly, under a certain operating frequency, the alternating current flowing through the capacitor relatively increases, so that the phase difference between the voltage and the current generated in the parallel resonance circuit increases from φ1 to φ2.

FIG. 7 is a conceptual diagram for further explaining the measurement principle of oil check sensor 150 according to the second embodiment of the present invention.

Referring to FIG. 7, the positive direction of the vertical axis in FIG.
Indicates the direction in which the phase of the voltage advances with respect to the current. FIG. 7 schematically illustrates a change in phase of a voltage with respect to a current in a parallel resonance circuit according to a frequency.

According to the adhesion of the metal powder to the coil head,
The resonance frequency of the parallel resonance circuit receiving the supply of the alternating current having the constant frequency fd changes from f1 to f2.

As the parallel resonance circuit operates at a frequency higher than the resonance frequency, the alternating current flowing through the capacitor relatively increases, so that the phase difference increases in the direction in which the voltage phase is delayed (current advance). . Therefore, the phase difference φ2 with respect to the current of the voltage when the metal powder adheres to the coil head is larger than the phase difference φ1 when the metal powder does not adhere to the coil head. Since the resonance frequency of the parallel resonance circuit changes continuously in accordance with the amount of metal powder attached to the coil head, the detected phase difference can be associated with the amount of metal powder attached.

In the oil check sensor 100 according to the first embodiment for detecting a change in amplitude, in order to ensure stable detection accuracy, it is necessary to ensure the stability of the amplitude of the AC component in the oscillation tuning signal. It is desirable to add the function of the oil check sensor 150 according to the second embodiment.
As for the above, since the amplitude stability does not significantly affect the detection accuracy, it is possible to realize the detection unit with a simpler circuit configuration.

FIG. 8 is a circuit diagram for explaining a specific configuration example of the oscillation tuning circuit 31. Referring to FIG. 8, oscillation tuning circuit 31 includes a resonance capacitor Cd, a coupling capacitor Cb, and an oscillation tuning signal generation circuit 35. The resonance capacitor Cd is connected between a node Nx that receives an oscillation tuning signal from the oscillation tuning signal generation circuit 35 and a ground line in order to form a parallel resonance circuit with the inductor component Ld of the coil head.

The coupling capacitor Cb extracts an AC component of the voltage generated in the parallel resonance circuit, and transmits it to the phase detection pulse generation circuit 42b.

The oscillation tuning circuit 35 includes a bias voltage generation circuit 36, an addition circuit 37, an oscillation circuit 38, and an internal voltage generation circuit 39.

Bias voltage generating circuit 36 includes a resistor R connected between + Vcc power supply line 152 and node Nz.
5 and a Zener diode ZD and a capacitor Cf connected in parallel between the node Nz and the ground wiring. Due to the Zener diode ZD, a constant DC bias voltage Vz (Vss ≦ Vz ≦ Vcc,
Vss: ground voltage). The capacitor Cf stabilizes the DC bias voltage Vz.

The oscillation circuit 38 includes a + Vcc power supply line 152
In response to the supply of the power supply voltage from -Vcc power supply line 154, reference resonance signal is output to node Ny. As the oscillation circuit 38, a triangular wave generation circuit using a generally used operational amplifier may be applied.

The addition circuit 37 includes a + Vcc power supply line 152
And an operational amplifier 160 that operates by receiving a power supply voltage from a -Vcc power supply line 154, and a feedback resistor R connected between an output terminal and an inverting input terminal of the operational amplifier 160.
6 and a resistor R7 connected between the output terminal of the operational amplifier 160 and the node Nx.

The non-inverting input terminal of operational amplifier 160 is connected to node Nz where DC bias voltage Vz is generated, and the inverting input terminal of operational amplifier 160 is connected to node Ny where reference oscillation signal DC bias voltage Vz is generated. . Operational amplifier 160 outputs an oscillation tuning signal obtained by adding DC bias voltage Vz and DC bias voltage Vz to node Nx.

Internal voltage generation circuit 39 converts internal power supply voltages + Vcc and -Vcc to + Vcc in accordance with the start control signal.
Output to cc power supply wiring 152 and -Vcc power supply wiring 154, respectively. At the timing before the activation control signal is activated, the internal power supply voltage is not supplied to each circuit in the oscillation tuning signal circuit 35, so that no oscillation tuning signal is generated. Since the supply of the internal power supply voltage is started in response to the activation of the start control signal, an oscillation tuning signal is generated, and the oil check sensor 150 is activated by exciting the coil head 10.

The oscillation tuning circuit 35 further includes a coupling capacitor Ce connected between the node Ny and the phase detection circuit 42a for transmitting the phase of the reference resonance signal to the phase detection pulse generation circuit 42a.

With such a configuration, the oscillation tuning circuit 31 has an oscillation tuning circuit in which a DC bias component for exciting the coil head 10 and an AC component for detecting a change in inductance of the coil head 10 are superimposed. A signal can be generated. Further, the phases of the reference resonance signal and the resonance output signal can be extracted and transmitted to the phase detection pulse generation circuits 42a and 42b.

Next, detection of a phase difference and signal processing after the detection will be described. Referring again to FIG. 5, the phase detection circuit 41 receives the reference resonance signal and receives the phase detection pulse PD.
1 and a phase detection pulse generation circuit 42b that receives the resonance output signal and generates a phase detection pulse PD2.

The phase detection pulse PD1 is activated at a timing when the reference resonance signal changes from a negative voltage to a positive voltage (hereinafter also referred to as a zero cross timing), and is deactivated again after a lapse of a certain time until the next zero cross timing. This is a pulse signal to be converted. The phase detection pulse PD2 is a similar signal, and detects the zero cross timing of the resonance output signal. Each of the phase detection pulse generation circuits 42a and 42b can be constituted by a comparator that compares a voltage signal transmitted by the capacitors Cb and Ce with a ground voltage.

The phase difference measuring circuit 51 outputs the high-frequency pulse CP
Count pulse generating circuit 54 for generating (frequency fp)
And the high frequency pulse CP and the phase detection pulses PD1, P
And a phase difference count circuit 52 that receives D2 and generates a detection level signal.

The frequency fp of the high frequency pulse CP is set sufficiently higher than the frequency fd of the reference oscillation signal.

The phase difference counting circuit 52 counts the time difference between the activation timings generated between the phase detection pulses PD1 and PD2 by the high-frequency pulse generated therebetween, and generates the obtained count value as a detection level signal. .

FIG. 9 is a circuit diagram showing a specific configuration example of the phase difference counting circuit 52. Referring to FIG. 9, phase difference count circuit 52 includes an inverter 161 that inverts and outputs phase detection pulse PD2, a NAND gate 163 that receives the output of inverter 161 and phase detection pulse PD1 as two inputs, and a NAND gate 163. 165, and a NAND gate 167 that receives the output of the inverter 165 and the high-frequency pulse CP as two inputs.
, An inverter 169 for inverting the output of the NAND gate 167, and a counter IC 170.

The counter IC 170 has an MR terminal and an LE terminal.
A terminal has a terminal and a CLK terminal. At an activation timing of a trigger signal supplied to the MR terminal, the counter value is reset and counting of a clock signal supplied to the CLK terminal is started. The counter IC 170 is L
The counting operation is continued until the signal of the E terminal is activated.

The output of the inverter 165 is at H level until the phase detection pulse PD2 is activated (H level) after the timing at which the phase detection pulse PD1 is activated (H level). Therefore, the high frequency pulse CP is transmitted to the CLK terminal of the counter IC 170 only while the output of the inverter 165 is at the H level.

The counter IC 170 resets the count value in response to the activation of the phase detection pulse PD1 input to the MR terminal, and waits until the phase detection pulse PD2 input to the LE terminal is activated. The number of high frequency pulses CP input to the CLK terminal is counted.

Further, after the counter IC 170, B
CD display IC175 and 7 segment display LED180
, The phase difference count circuit 5
The detection level signal, which is the count value of 2, can be displayed on the LED.

FIG. 10 is a timing chart for explaining the operation of the phase difference measuring circuit 51.

Referring to FIG. 10, when there is no adhesion of metal powder to the coil head, the phase detection pulse PD1
Is activated at time t0, and the phase detection pulse PD2 is activated at time t1 with a delay. In this case, since one high-frequency pulse is generated during the phase difference φ1 of the parallel resonance circuit, the count value “1” is output as the detection level signal.

In the case where the metal powder is adhered to the coil head, the phase detection pulse PD2 is activated at time t2 after the activation of the phase detection pulse PD1 at time t0. In this case, since five high-frequency pulses are generated during the phase difference φ2 of the parallel resonance circuit,
The count value “5” is output as the detection level signal.

As described above, it is possible to output a phase difference that continuously changes according to the amount of metal powder adhering to the coil head as a count value.

Oil Check Sensor 15 of Second Embodiment
0, a detection level signal corresponding to the amount of metal powder adhering to the coil head can be obtained as a digital value, as described above. Therefore, in addition to the effects described in the first embodiment, output data is also transferred to a personal computer. It can be handled more easily, for example, by processing the data.

In the oil check sensor 150,
As with the oil check sensor 100 of the first embodiment, a threshold value is provided for the detection level signal, and when the threshold value is exceeded, the abnormality detection signal is activated, so that appropriate abnormality monitoring can be performed. .

The effect of operating the oscillation tuning circuit in synchronization with the start control signal and the point at which the detection coil head is formed as an electromagnet and the metal powder in engine oil is adsorbed has been described in the first embodiment. Since this is the same as the above, the description will not be repeated.

It should be noted that the embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0103]

According to the first aspect of the present invention, the oil check sensor utilizes a change in the inductance value of the detection coil head according to the amount of metal powder adhering to the detection coil head which is electromagnetized by the oscillation tuning circuit. Since the amount of metal powder in the engine oil is detected, the quantity of the metal powder in the engine oil can be quantitatively detected. Can be simplified.

The oil check sensor according to claim 2 is
In addition to the effect of the oil check sensor according to claim 1, an abnormality detection signal is generated when the inductance value of the detection coil head that changes due to the adhesion of the amount of metal powder exceeds a certain level. Monitoring can be performed more appropriately.

The oil check sensor according to claim 3 is
In addition to the effect of the oil check sensor according to the first or second aspect, the oscillation tuning circuit can be activated only in a necessary period according to the control activation signal, so that power consumption can be reduced.

The oil check sensor according to claim 4 is
In addition to the effect of the oil check sensor according to claim 3, since the oscillation tuning circuit can be started in conjunction with the power signal of the engine, there is a high possibility that the metal powder is precipitated in the engine oil. It is possible to more accurately check the amount of metal powder in the engine oil while avoiding a stop.

The oil check sensor according to claim 5 is
Utilizing the phase change of the AC voltage caused by the change in the inductance value of the detection coil head according to the amount of the metal powder attached to the detection coil head which is electromagnetized by the oscillation tuning circuit, the metal powder in the engine oil is used. Since the amount is detected, quantitative detection of the amount of metal powder in the engine oil can be performed stably with a simpler circuit, and there is no need to design the system taking into account the steady removal of the sensor. Thus, the structure of the sensor can be simplified.

The oil check sensor according to claim 6 is
Since the output signal can be obtained as a digital signal, in addition to the effect of the oil check sensor according to claim 5, the amount of metal powder in the engine oil is detected by an output signal that can be handled more easily. Is possible.

The oil check sensor according to claim 7 is
In addition to the effect of the oil check sensor according to claim 6, an abnormality detection signal is generated when the inductance value of the detection coil head, which changes due to the adhesion of the amount of metal powder, exceeds a certain level. Monitoring can be performed more appropriately.

An oil check sensor according to claim 8 is
In addition to the effect of the oil check sensor according to any one of claims 5 to 7, the oscillation tuning circuit can be activated only in a necessary period according to the control activation signal, thereby reducing power consumption. Can be.

An oil check sensor according to claim 9 is
In addition to the effect of the oil check sensor according to claim 8, the oscillation tuning circuit can be started in conjunction with the power signal of the engine, so that the engine is likely to have metal powder precipitated in the engine oil. It is possible to more accurately check the amount of metal powder in the engine oil while avoiding a stop.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of an oil check sensor 100 according to Embodiment 1 of the present invention.

FIG. 2 is a conceptual diagram for explaining a measurement principle of the oil check sensor 100 according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a specific configuration of an oscillation tuning circuit 30 and a detection and rectification circuit 40.

FIG. 4 is a schematic block diagram illustrating a configuration of an oil check sensor 150 according to Embodiment 2 of the present invention.

FIG. 5 shows detection / main body 1 of oil check sensor 150.
FIG. 21 is a block diagram for explaining the configuration of an embodiment 21 in more detail.

FIG. 6 is a waveform chart showing an example of a change in a resonance output signal according to adhesion of metal powder.

FIG. 7 is a conceptual diagram illustrating a measurement principle of an oil check sensor 150 according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram for explaining a specific configuration example of an oscillation tuning circuit 31;

FIG. 9 is a circuit diagram showing a specific configuration example of a phase difference counting circuit 52.

FIG. 10 is a timing chart for explaining the operation of the phase difference measurement circuit 51.

FIG. 11 is a schematic block diagram for explaining the operation principle of an oil check sensor 200 using a permanent magnet according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Detection coil head 30, 31 Oscillation tuning circuit 40 Detection rectification circuit 41 Phase detection circuit 50 Voltage comparison circuit 51 Phase difference measurement circuit

Claims (9)

[Claims] 1. An oil check sensor for detecting an amount of metal powder in lubricating oil, comprising: sensor means including a coil head immersed in lubricating oil and magnetized by an exciting current; Detecting means for generating a detection signal according to the amount of the metal powder, the detection means generates an oscillation tuning signal which is an AC electric signal in which a DC component for supplying the excitation current is superimposed, An oil check sensor including an oscillation tuning circuit that generates a detection signal whose amplitude changes according to an inductance value of the coil head that changes according to an amount of the metal powder attached to the coil head. A detection level signal generating circuit for generating a detection level signal having a DC voltage corresponding to an amplitude of the detection voltage signal; and a detection level signal generating circuit configured to determine a voltage level of the detection level signal and a predetermined reference voltage. The oil check sensor according to claim 1, further comprising a voltage comparison circuit that generates an abnormality detection signal when the detection level signal exceeds the reference voltage. 3. The oscillation tuning circuit generates the AC electric signal in response to an externally applied start control signal.
The oil check sensor according to claim 1. 4. The oil check sensor according to claim 3, wherein the start control signal is activated in conjunction with a power signal of an engine in which the oil check sensor is incorporated. 5. An oil check sensor for detecting an amount of metal powder in lubricating oil, comprising: sensor means including a coil head immersed in lubricating oil and magnetized by an exciting current; Detecting means for generating a detection signal in accordance with the amount of metal powder, the detecting means comprising: a resonance capacitor connected in parallel with the coil head; a DC component for supplying the exciting current; An oscillation tuning signal generating means for supplying an oscillation tuning signal obtained by superimposing a reference oscillation signal which is an AC electric signal having a frequency to a resonance circuit formed by the resonance capacitor and the coil head; and A phase difference detecting means for detecting a phase difference between a current and a voltage in the resonance circuit, the phase difference detecting means changing in accordance with an amount of the metal powder attached to the head; , Oil check sensor. 6. The phase difference detecting means, comprising: a first phase detection pulse signal activated at a timing when a polarity of an AC component of the oscillation tuning signal changes; A phase detection circuit that generates a second phase detection pulse signal that is activated at the timing when the first phase detection pulse signal is activated. A phase difference measurement circuit for measuring, wherein the phase difference measurement circuit generates a high frequency pulse having a second frequency higher than the first frequency; a first phase detection pulse signal; 6. A phase difference counting circuit for counting the high-frequency pulses generated while only one of the second phase detection pulse signals is activated. Oil check sensor. 7. The oil check sensor according to claim 6, wherein the detection unit further includes an abnormality detection circuit that generates an abnormality detection signal when a count value of the phase difference count circuit exceeds a predetermined value. 8. The oil check sensor according to claim 5, wherein said oscillation tuning signal generating means generates said oscillation tuning signal in response to an externally applied start control signal. 9. The oil check sensor according to claim 8, wherein the activation control signal is activated in conjunction with a power signal of an engine in which the oil check sensor is incorporated.