JPS60165518A - Oil level detector for vehicle - Google Patents

Abstract

PURPOSE:To eliminate the influence of a noise, etc., at a start by generating a hold signal corresponding to the initial value of a detector output in power-on operation, and sending a signal when an integral value up to the saturation of the hold signal is larger than a set value as a similar integral value in a state which specifies a shortage of oil. CONSTITUTION:When the movable contact of an ignition switch SW is brought into contact with the fixed contact IG, a constant voltage circuit 30 generates a constant voltage Vd and a constant current generating circuit 20 supplies a constant current to an oil level sensor 10 as a self-heating type resistance thermometer bulb having positive resistance temperature characteristics under the control of an arithmetic circuit 40. The analog voltage VS from the sensor 10, on the other hand, rises abruptly to an initial value VS0, i.e. value of the hold signal at time t0 and reaches to its saturation value at time tS, and attains to VS1 and VS2 when the oil level is at the upper and lower limits respectively. Further, the difference between the signals VS and VS0 is integrated from t0 to tS and the arithmetic circuit 40 sends the signal to a driving circuit 50 when the level is a similar integral value at the lower limit, i.e. smaller than the set value.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a vehicle oil level detection system suitable for detecting a lack of oil in an oil tank of a vehicle heating system based on the liquid level. Regarding equipment.

(Prior art) Conventionally, in this type of vehicle oil level detection device, temperature measurement is performed after applying a constant current to a self-heating type resistance temperature detector having a positive resistance temperature characteristic assembled in an oil tank. When the resistor saturates its internal resistance value due to self-heating according to the penetration length into the oil in the oil tank, detecting the instantaneous output of the temperature sensing resistor at the time of saturation as the liquid level, Some oil pumps generate an output signal indicating oil shortage when this instantaneous detection level exceeds a predetermined reference level.

By the way, in such a configuration, the timing at which the constant current applied to the resistance temperature sensor is started usually coincides with the time when the movable contact in the ignition switch of the vehicle contacts the identification contact IO, and The saturation time of the internal resistance of the temperature-measuring resistor for one shift is 1.5 seconds after the start of applying the standard flow to the 11 resistors. Therefore, the above-mentioned ll'l (gl of m resistors (resistance (14 or I
6 Time at the ox that harmonizes! If the ignition switch described in iii. Sudden change in DC power supply voltage!II←
In addition, there is a risk that the ignition circuit of the vehicle may generate ignition noise due to its operation, so the instantaneous detection level of the oil level detection device may be affected by the above-mentioned starting noise, sudden fluctuations in DC power supply voltage, or ignition noise. The large shadow 6 may cause the detection device to perform erroneous detection.

(Purpose of Light) The present invention was made in response to the above-mentioned problems, and its purpose is to eliminate various noises that tend to occur in the air system when starting a vehicle engine, or to reduce the direct current of the vehicle. To provide an oil level detection device for a vehicle that always correctly detects a lack of oil/1/amount in an oil tank without being affected by voltage fluctuations of a power supply or the like.

(Structure of the Invention) In achieving the above object, the structure of the present invention includes: a constant current generating means which generates a constant current by being supplied with power from a source of direct current 'ε(of the vehicle in response to operation of an operation switch); a detecting means for detecting the liquid level as an analog signal based on an internal resistance value which increases due to self-generation 2 corresponding to the liquid level of oil in the oil tank of the vehicle when an electrical sound current is applied; In the state that defines the lack of oil, the amount of increase in the level of the analog signal is integrated over the time from a certain time after the constant current is applied to the detection means until the time when the level of the analog signal 6iJ is saturated. a setting means for setting the result as a setting signal; and a setting means for setting the result as a setting signal;
a holding signal generating means for generating the initial value of the analog signal of 11J as a holding signal in response to a supply from a source; and integrating the difference between the value of the analog signal and the value of the holding signal with respect to time. an integrating means for generating an integral signal;
and output signal generating means for generating an output signal when the value of the integrated signal No. 411 is greater than the value of the setting signal.

(Effects of the Invention) By configuring the present invention in this way, in response to the operation of the operation switch, the 1iJ current generating means starts supplying a constant current (=J) to the detecting means. At the same time, the nil holding signal generating means generates a holding signal, and the integrating means integrates the difference between each value of the analog signal and the holding signal with respect to time (integrates as N, and mJ recording output signal generating means, F+iJ Since an output signal is generated when the recorded integral symbol signal mJ is greater than the recorded signal value, the output signal that increases is equal to the value of the 111 integral signal, that is, the level of the analog signal, up to the side sum of the two rising widths. is generated as a signal indicating oil shortage when the time integral value of is larger than the value of the setting signal, that is, the time integral value until the saturation of the analog (y above the level of No. A) width that defines oil shortage. As a result, the proportion of fluctuations in DC power supply voltage, starting noise, ignition noise, etc., as described in the prior art of the MW of the present invention, in the value of the integral signal is maintained at a very low level, making it difficult to detect by the device of the present invention. Results are always obtained as correct information.

(Example) Your Honor, an example of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a vehicle oil level detection device to which the present invention is applied.
Oil level sensor 10, constant current generating means 20 and constant voltage circuit 30 connected to the positive terminal of current power source B via ignition switch SW and fuse F of the vehicle
It is equipped with

The oil level sensor 10 includes an oil level gauge 11 (
It is mounted inside the tip of the tip (see Fig. 6), and its lower part is exposed to the outside through the opening 11a (see Fig. 4) of this tip, and has a positive resistance-temperature characteristic (see Fig. 6). Self-heating type dlllll warm body antibodies are formed. As will be described later, the oil level sensor 10 is supplied with a constant current from the constant current generating circuit 20 and generates heat by itself, causing its internal resistance 1 to rise, and generates this as an analog voltage V6.

In this case, the analog voltage vll+ from the oil level sensor 10 changes as shown in FIG. 7 in relation to time t (seconds). However, in FIG. 7, the curve Ll indicates that the oil level in the oil tank (not shown) of the vehicle is at the upper limit level position MAX at the tip of the oil level gauge 11 (as shown in FIGS. 4 and 5). code 1
1b), and curve L2
, the oil level is the same as the oil level gauge 11.
The curve Ll (or L2) corresponds to the case where the lower end of the oil level sensor is at the MIN position (indicated by reference numeral 11C in FIGS. 4 and 5). After starting to flow a constant current to 10, the analog voltage v8
It shows that the voltage rises rapidly to VB0, and then as the voltage rises, it becomes almost saturated at Vs+ (or VB2). Incidentally, the oil level gauge 11 is attached to the oil tank with its tip end immersed in the oil in the oil tank.

The constant current generating circuit 20 generates a DC power source B by contacting the fixed contact G of the movable contact in the ignition switch SW.
It operates by receiving the power supply voltage from the fuse F through the fuse F, and generates a constant current under the control as described below by the arithmetic circuit 40, which is applied to the oil level sensor 10 (=1). When the contact contacts the fixed contact G, it receives the power supply voltage from the DC power supply B through the fuse F, and generates a constant tortoise pressure d.

As shown in FIG. 2, the arithmetic circuit 40 includes a microphone 0 computer 41, and this microcomputer 4
1 operates by receiving a constant voltage Vd from a constant voltage circuit 30, and a computer program stored in advance in the 8th circuit is operated.
The process is executed according to the flowchart 1 shown in the figure, and during the execution, the constant current generating circuit 20, the binary counter 42, the presettable down counter 45, the AN
D gate 45 (2, D type flip-flop 46, AND
It performs various arithmetic processing necessary for controlling the gate 47a1 counter 47 and the D-type flip-flop 49a.

In such a case, the microcomputer 41 uses the start signal, the S)/Tsub signal, and a series of clock pulses b1 and the clock enable signal as? during its arithmetic processing. a'y
1 and second clear signal c1. c2, a latch signal e, a load signal f, and a gate signal da (see FIGS. 9 and 10). Incidentally, in Fig. 2, the symbol 4117 indicates a buffer, and this buffer 41a receives the power supply voltage from the DC power supply B in contact with the fixed contact work G of the movable contact of the ignition switch SV/, and buffers it. A voltage is generated and applied to the microcomputer 41.

The binary counter 42 responds to the clock enable signal a from the microcomputer 41 and outputs each clock pulse b? 11-Count and generate the counting result as a digital signal. Further, the binary counter 42 clears its counting result in response to a clear signal Cl from the microcomputer 41.

The D-A converter 43 receives the digital signal from the binary counter 42, converts the value of this digital signal into analog based on the reference voltage "rer" generated from the reference voltage generator 43a, and converts the analog conversion result into an analog signal. a
Live-t-le. A comparator 431) compares the analog voltage 6 from the oil level sensor 10 with the analog signal from the DA converter 46, and outputs an analog voltage Vθ and mJ.
A high level signal is generated when the level of the analog signal matches the level of the analog signal. This means that the high level signal from the comparator 431) indicates the end of counting by the binary counter 42, that is, the end of conversion signal d (see FIGS. (see ).

The latch circuit 44 latches the value of the digital signal from the binary counter 42 in response to the latch signal e from the microcomputer 41 and generates it as a latch digital signal. If the latched digital signal goes up, the latched digital signal becomes the negative output of the digital signal from the binary counter 42. The presettable down counter 45 presets the value of the latch digital signal from the latch circuit 44 in response to the load signal f from the microcomputer 41, generates a high level signal from its carry-out terminal CO, and transfers this preset value to the microcomputer 41. While the gate signal f is being generated from the computer 41, the AND gate 4512 is turned on to count down in response to each clock pulse b generated, and when the countdown result reaches zero, a low level signal h ( (see Figure 10).

The D-type flip-flop 46 is connected to the microcomputer 41
A low level signal is generated from the output terminal Q in response to the clear signal C1 from the output terminal Q. 1, this D-type flip-flop 46 performs an AND game 1 under the inverting action of an inverter 467 based on a low level signal from its output terminal Q.
-46b generates a high level signal in response to the presettable down counter No. 1, a constant voltage d from the constant voltage circuit 60 is generated from its output terminal Q as a high level signal 1 (see Figure 10). Then, this high level signal 1 is made to disappear in response to a clear signal C1 from the microcomputer 41. The counter 47 is cleared in response to the clear signal C2 from the microcomputer 41, and the counter 47 is cleared in response to the clear signal C2 from the microcomputer 41.
1 through the AND gate 4717, and the counting result is generated as a digital signal.

The threshold value setting circuit 48 sets, for example, when the liquid level of the oil is at the upper limit level (S [MAX) of the oil level gauge 11, the time t after the start of the constant current flow to the oil level sensor 10 (7th (see figure) to analog voltage Vllll
Analog voltage until saturation time ts (see Figure 7) ■8
The time integral value of the rise width Δ■ (see FIG. 7) is set as a threshold value, and this is generated as a setting signal. The digital comparator 49 compares the digital V signal from the counter 47 with the setting signal from the threshold setting circuit 48, and when the values of both signals match, it generates a high level signal from its output terminal A=B. In response to the clear signal c2 from the microcomputer 41, the D-type flunograph terminal 49a generates a low level signal from its output terminal Q, and the digital comparator 49%C (7) generates a low level signal from the constant voltage circuit 30 at the rise of the high level signal. A high level signal is generated from the output terminal Q of the constant market pressure d and applied to the drive circuit 50. The drive circuit 5o generates a drive signal in response to a high level signal from the D-type flip-flop 4912 of the arithmetic circuit 40.

The oil warning lamp 60 lights up in response to a drive signal from the drive circuit 5o.

In this embodiment configured as above, when the movable contact of the ignition switch SW contacts the fixed contact G, the constant voltage circuit 3o receives the supplied voltage from the DC power supply B and generates a constant voltage Vd. At the same time, the microcomputer 41 of the arithmetic circuit 4o operates to execute the computer program in step 7o according to the flowchart 1 of FIG.
At step 71, it is determined to be YKsJ based on the buffer pressure from the buffer 41a, and at step 72 it waits for several milliseconds, and then at step 73
A start signal is generated from the output terminal START, and in response to this, the constant current generation circuit 20 generates a constant current while receiving the power supply voltage from the DC power supply B, and applies it to the oil level sensor 10. . As a result, the oil level sensor 10 generates an internal resistance value that increases due to its self-heating as analog 1; pressure 8.

Next, the microcomputer 41 waits for a few milliseconds in step 74, generates the clock enable signal a from its output terminal GE in step 75, and performs a step based on the non-generation of the conversion end signal d from the comparator 43b. h with “NO” in 77! Based on the return judgment, in step 76, the clock pulse b is output from the output terminal OK.
occurs repeatedly. Therefore, the binary counter 42 receives the clock enable signal a from the microcomputer 41.
In response to this, the microcomputer 4 becomes ready for counting.
The clock pulses b sequentially generated from 1 are counted and used as an initial signal to the D-A converter 46 and the latch circuit 4.
I agree with 4. Then, the DA converter 43 converts the value of the digital /I/ signal from the binary counter 42 into analog based on the reference voltage Vref from the reference voltage generator 4roa, and generates it as an analog signal.

When the level of the analog signal from the D-A converter 43 increases and becomes equal to the analog voltage v6 from the oil level sensor 10, the comparator 43b generates a conversion end signal d, which is applied to the input terminal EOO of the microcomputer 41. Give.

Then, in step 77, the microcomputer 41 outputs "YE" based on the conversion end signal from the comparator 43'b.
sJ, and in step 78 its output terminal qLFo
A clear signal C+'t' is generated from the output terminal LATCH to clear both the count value of the binary counter 42 and the output of the D-type double-flop 46. In step 79, a launch signal e is generated from the output terminal LATCH, and In response, the latch circuit 44
The negative value of the digital signal from the binary counter 42 at the time of generation of the conversion end signal d from the converter 43b7)) is latched as a latch digital signal. This means that the latch digital signal from the launch circuit 44 calculates the number of clock pulses b corresponding to the analog voltage ■8 at the time of generation of the conversion end signal d from the comparator 45t) to the digital initial value of the analog voltage ■8. In this case, the digital initial value is larger as the oil level is closer to the lower limit level position M of the oil level gauge 11. Note that the conversion end signal d from the comparator 43b
is D due to clearing of the count contents of the binary counter 42.
- It disappears due to the disappearance of the analog signal from the A converter 43.

Tweet, the microcomputer 41 generates a clock enable signal a and a load signal f in step 80,
In step 81, a gate signal g is generated, and both nutesops 7
Step 8 as for the iterative operation in 6.77
When the clock pulse b is repeatedly generated in step 82 based on the repeated determination of "NOJ" in 6, the binary counter 42 generates the clock pulse b in the same way as in the above case.
At the same time, the D-A converter 43 starts counting the D-
A conversion action begins. In addition, the presettable down counter 45 presets the latch digital signal (lJik) from the launch circuit 44 in response to the load signal f from the microcomputer 41, and while the gate signal g is being generated, the ANDN-gate a complete micro combination ,
- The preset value is counted down in response to clock pulses b sequentially generated from 41, and when the countdown result becomes zero, a low level signal is generated from the carry-out terminal Co.

Then, the AND gate 46b generates a high level signal in response to the low level signal from the presettable down counter 45' under the inverting action of the inverter 46 (l) as the D-type Frisopfrodde 46 is cleared. In response to the high level signal, the DW flip-flop 46 generates a high level/L' signal ie and applies it to the AND gate 47a. As a result, the counter 47 counts the clock pulses b sequentially generated from the microcomputer 41 through the ANDN-gate aTh while the high level signal 1 is being generated, generates this as a digital signal, and applies it to the digital conhaler 49. Then, when the conversion end signal d is generated from the comparator 43b in the same manner as described above, the microcomputer 41 determines YESJ in step 86, eliminates the gate signal g in step 84, and outputs AN.
D game) 45.2 stops applying the clock pulse b to the presec pulldown counter 45, and in step 85, a clear signal C1 is generated to clear the count contents of the binary counter 42, and the DW flip-flop 4
The high level signal 1 from 6 is made to disappear.

However, in the current situation, a predetermined time period (pre-recorded in the microcomputer 41 in 1. Since the period (completed) has not elapsed, the microcomputer 41 determines rNOJ at step 86 and returns the computer program to step 80.

Thereafter, as the microcomputer 41 repeats the calculations in steps 80 to 86, the counter 47 becomes A N
In cooperation with the D gate 47a, the series of clock pulses b is counted repeatedly during each occurrence of the high level 18 generated repeatedly from the D-type flip-flop 46 for each occurrence of the low level signal from the presettable down counter 45. Then, the digital comparator 4
4a' of the hexydigital signal applied to 9 (; Level signal output.

In other words, the launch circuit 44 provides an analog signal.

After the digital initial value of the voltage Vθ is launched, the rising width digital value corresponding to the rising width ΔV of the analog voltage ■6 that increases with the passage of time is generated as the high level signal 1 from the D-type flip-flop 46 of the counter 47. A digital signal is generated from the counter 47 by being integrated over time by each counting action on each series of clock pulses b at each time, and the value of this digital signal, that is, the integrated value of the rise width digital value is sent to the digital comparator 49. Since the value of the setting signal from the r4 value setting circuit 48 is compared with the value of the setting signal from the r4 value setting circuit 48, when the movable contact of the ignition switch SW contacts the fixed contact ST, Even if starting noise, fluctuations in the power supply voltage of DC power supply B, ignition noise, etc. mentioned above are mixed into the device of the present invention as errors, the proportion of these mixed errors in the integrated value of each rise width digital value is It will be kept very low so that no ttV will occur at the output of digital comparator 49.

As described above, when a high level signal is generated from the digital comparator 49, the Dffl flip-flop 49a generates a high level signal, and in response, the drive circuit 50
generates a drive signal and lights up the oil/l/v warning lamp 60. This allows the driver to correctly recognize the lack of V amount. Note that the determination in step 86 is [YE
When it comes to sJ, Microfunby 41 is step 8.
At 7.88, the Nutonop signal and the clear signal C2 are sequentially generated, and the constant current generating circuit 20 is connected to the microcomputer 41.
The constant current generation is stopped in response to the Nutnobu signal from the microphone 1 computer 41, and the counter 47 and the DIJ9 flip-flop 49a are both cleared in response to the clear signal C2 from the microphone 1 computer 41.

Furthermore, in carrying out the present invention, the present invention is not limited to the embodiments described above, and, for example, a constant current generating means that is supplied with power from a DC power source of a vehicle in response to the operation of an operation switch and generates a constant current. 01J;
When the recorded liquid level is in a state that defines the shortage of the above-mentioned OJ, the above-mentioned analog signal is determined for the time from the time after applying the constant current to the detection means until the saturation time of the level of the analog signal. a setting means for setting a result of integrating a level rise width of the signal as a setting signal; and a setting means for repeatedly generating a second timing signal after generating a first timing signal in response to power supply from the DC power supply by operating the operation switch. a timing signal generating means for converting the analog signal into a first digital signal in response to the first timing signal, and converting the analog signal into a second digital signal in response to each of the second timing signals after the conversion; A-D converting means for repeatedly converting into a digital signal υ; holding signal generating means for holding the value of the first digital signal and generating it as a holding signal; and a value of each second digital signal Ga and the holding signal. The present invention includes an integrated signal generating means that sequentially integrates the difference in diameter from the value of the integrated signal and generates an integrated signal, and an output signal generating means that generates an output signal when the value of the integrated signal is larger than the value of the setting number 1. By configuring the invention, substantially the same effects as those of the embodiments described above can be achieved.

In such a case, power is supplied from the DC power supply in response to the operation of the operation switch to convert the value of the analog signal into a first digital value, and after this conversion, the value of the analog signal is converted into a second digital value. A microcontroller is programmed to perform repeated conversion, sequentially integrate the winter values of each of the second digital values and the first digital value, and generate an output signal when the integrated result is larger than the pre-stored value of the setting signal. A computer may be used in place of the setting means, timing signal generation means, A/D conversion means, holding signal generation means, integration signal generation means, and output signal generation means.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the device of the present invention, and FIG.
The figure is the same detailed circuit diagram, Figure 6 is an external view of the oil level gauge, Figures 4 and 5 are enlarged views of the same parts, and Figure 6 is the positive resistance temperature of the oil level sensor in Figures 1 and 2. FIG. 7 is a graph showing the output characteristics of the oil level sensor, FIG. 8 is a flowchart showing the action of the microcomputer in FIG. 2, and FIGS. 9 and 10 are graphs showing the output characteristics of the oil level sensor. FIG. 3 is an output waveform diagram of each circuit element in FIG. Explanation of symbols B: DC power supply, SW: ignition switch, 10: oil level sensor, 20: constant current generation circuit, 41: microcomputer. 4'2...Binary counter, 43...D-4 converter. 431)...Comparator, 44...Latch circuit. 45...Presettable down counter, 46b. 47a...AND gate, 46...D-type Frinopfloff'', 4612...Inverter, 47...Counter, 48...Threshold value setting circuit, 49...Digital comparator. Applicant: Nippondenso Co., Ltd. Agent Person Patent Attorney Teru Hase −

Claims (1)

[Claims] a constant current generating means that is supplied with power from a vehicle's DC power supply in response to the operation of an operation switch and generates a constant current; a detection means for detecting the liquid level /I/ as an analog signal based on an internal resistance value that increases due to heat generation; Setting means for setting, as a setting signal, the result of integrating the range of increase in the level of the analog signal over a period of time from a certain time after the provision to a time when the level of the analog signal is saturated;
a hold signal generating means for generating an initial value of the analog signal as a hold signal in response to power supply from the DC power source by operating the operation switch; 1. An oil level detection device for a vehicle, comprising: an integrating means for integrating the integral signal and generating the integrated signal as an integral signal; and an output signal generating means for generating an output signal when the value of the integral signal is larger than the value of the setting signal.