JPH11132325A - Sensor open failure detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect open failure of a sensor surely by providing the device with a circuit which is pulled up or pulled down to a first channel before a sensor circuit, and holding voltage of an A/D converting capacitor into voltage capable of detecting a fail when a second channel is scanned. SOLUTION: An oil temperature input circuit 10 used as a channel before a throttle circuit is constituted so as to charge an A/D converting capacitor 51 by carrying out pulling-up with 5 V by power source Vcc (5 V) of a terminal 12 when the before channel is scanned. In the case where the channel before the throttle circuit is scanned, a switch 33 is turned on, and the A/D converting capacitor 51 is charged. After that, the switch 33 is turned off, voltage of an A/D port 31 is A/D-converted, and then, the channel of the throttle circuit is scanned. Namely, a switch 43 is turned on, and the A/D converting capacitor 51 is charged by voltage of the A/D port 41 of the throttle input circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor open failure detecting device which constitutes a part of an electronic control system for controlling a transmission mounted on a vehicle.

[0002]

2. Description of the Related Art When the impedance of a circuit is large at the time of a sensor open failure, the voltage at the time of the open failure falls below the fail determination value due to, for example, a voltage drop due to a leakage current of the microcomputer, and the failure determination becomes impossible.
FIG. 10 is a diagram of such a conventional throttle sensor open failure detection circuit, FIG. 11 is a diagram showing time constants of various parts of the throttle sensor open failure detection circuit, and FIG.
6 is a time chart illustrating a conversion operation.

In FIG. 10, 1 is an oil temperature sensor, 2 is a throttle sensor, 3 is a switch, and 10 is an oil temperature input circuit. The oil temperature input circuit 10 sequentially includes a capacitor C ₂₇₀ (470 pF) 11 connected between the input line 4 connected to the oil temperature sensor 1 and the ground, and an input line 4 and the power supply voltage V _CC terminal 12 from the input end. Connected resistor R ₂₇₀ (1 kΩ) 1
3. Capacitor C ₂₇₁ connected between input line 4 and ground
(0.1 μF), a resistor R ₂₇₁ (1 kΩ) 15 connected in series to the input line 4, a diode D ₂₇₀ 17 connected between the power supply voltage V _CC terminal 16 and the input line 4, the input line 4 and the ground and a resistor R ₂₇₂ (5.1kΩ) 19 connected in series with the diode D ₂₇₁ 18, input line 4 connected to.

[0004] The throttle input circuit 20 has an input line 5 connected to the throttle sensor 2 via the switch 3 sequentially from the input end.
A resistor R ₁₅₄ (1 MΩ) 22 connected between the _CC terminals 21,
Capacitor C ₁₅₂ (4) connected between input line 5 and ground
700 pF) 23, a resistor R connected in series to the input line 5
₁₅₆ (39 kΩ) 24; capacitor C ₁₅₃ (0.1 μF) 25 connected between input line 5 and ground; power supply voltage V _CC
Diode D ₁₅₂ 2 connected between terminal 26 and input line 5
7, a diode _D153 connected between the input line 5 and the ground.
28, a resistor R ₁₅₈ (5.1) connected in series to the input line 5
kΩ) 29.

The output of the oil temperature input circuit 10 is A /
Via the D port AN ₅ 31, A / D conversion resistor R _AD (1
kΩ) 32 and a switch SW ₁ 33. The output of the throttle input circuit 20 is the A / D port A
A / D conversion resistance R _AD (1 kΩ) 4 through N ₆ 41
2. It is connected to the switch SW ₂ 43. The switch SW ₁ 33 and the switch SW ₂ 43 both have an A / D conversion capacitor C whose other end is connected to ground.
_AD (20 pF) 51.

Therefore, the throttle input circuit 20
The time constant of each part of is as follows. That is, FIG.
In FIG. 11, the circuit surrounded by the dotted line is composed of (power supply voltage V _CC terminal 21-resistor R ₁₅₄ 22-
The time constant 7τ of the capacitor C ₁₅₂ 23) is 7 × C
₁₅₂ × R ₁₅₄ = 7 × 4700 pF × 1 MΩ = 164 μs
It is.

In FIG. 10, a circuit surrounded by a dotted line has a time constant 7τ in (power supply voltage V _CC terminal 21-resistor R ₁₅₆ 24-capacitor C ₁₅₃ 25) as shown in FIG. , 7 × C ₁₅₃ × (R ₁₅₄ + R ₁₅₆ ) =
7 × 0.1 μF × (1 MΩ + 39 kΩ) = 700 ms.

Further, in FIG. 10, a circuit surrounded by a dotted line is a capacitor (capacitor C) as shown in FIG.
₁₅₃ 25-resistance R ₁₅₈ 29-A / D port 41-A / D
The time constant 7τ in the conversion resistor R _AD 42-switch SW ₂ 43-A / D conversion capacitor C _AD 51-ground) is 7
× C _AD × (R _AD + R ₁₅₈ ) = 7 × 20 pF × (5.1k
Ω + 1 kΩ) = 0.85 μs.

[0009]

However, according to the conventional throttle sensor open failure detection circuit described above, A / D conversion in a scan mode is performed as shown in FIGS. 12 (a) and 12 (b). In this case, the voltage of each channel is subjected to A / D conversion every 2 ms. At that time, the A / D conversion capacitor C _AD 5 in the A / D converter
1, the voltage of each channel is charged and discharged in order.

Therefore, the throttle sensor 2 shown in FIG.
If the open failure occurs, the throttle input voltage will be 5V, but if the previous channel is low voltage, A
A / D conversion capacitor C _AD 51 in A / D converter 30
Is charged from a low voltage to 5 V, so that a current flows into the microcomputer.
A / D conversion capacitor C _{AD in} A / D conversion converter 30
Before the A / D converter 51 is sufficiently charged, the next A / D conversion is performed, and the voltage charged in the capacitor 51 in the A / D conversion converter 30 gradually decreases to become lower than the fail determination value. Failure judgment becomes impossible.

That is, when scanning is performed, the throttle voltage gradually decreases because the time constant is large as shown in FIG. As a result, the voltage of the A / D conversion capacitor C _AD 51 also decreases as shown in FIG. In other words, a leak current flows during scanning of the throttle sensor, and it is impossible to charge the capacitor in the A / D conversion converter 30 sufficiently.

Accordingly, the voltage at the time of the open failure of the throttle sensor falls below the fail determination value, and the failure determination becomes impossible. The present invention eliminates the above-described problems, and provides an A
An object of the present invention is to provide a sensor open failure detection device that can reliably detect an open failure of a sensor while avoiding a decrease in a voltage charged in a capacitor in a / D conversion converter.

[0013]

In order to achieve the above object, the present invention provides: (1) a sensor open failure detection device, comprising a circuit for pulling up or pulling down a first channel before a sensor circuit; The voltage of the A / D conversion capacitor at the time of scanning the second channel connected to the sensor circuit is maintained at a voltage at which a failure can be detected.

[2] In the sensor open failure detecting device according to the above [1], the sensor connected to the second channel is a throttle sensor.

[0015]

According to the present invention, when a channel in front of a sensor circuit is pulled up (pull up), a leak current is generated at the time of A / D conversion at the time of a sensor open failure. Also, the voltage of the A / D conversion capacitor is reduced and does not fall below the fail determination value, so that the fail determination can be reliably performed.

In the case of pulling down a channel in front of the sensor circuit, a pull-down is performed in advance so as to prevent detection in a low voltage region during A / D conversion at the time of a sensor open failure. A /
The voltage of the D conversion capacitor is reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an electronic control system of an automatic transmission according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a throttle sensor open failure detection circuit according to the first embodiment of the present invention, and FIG. 4 is a flowchart illustrating a throttle sensor open failure detection according to the embodiment. In this embodiment, the same parts as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

In an electronic control system of an automatic transmission, an oil temperature sensor may not be required depending on a vehicle.
Depending on the model, an empty channel may be created for A / D conversion. In FIG. 1, 101 is an automatic transmission, 102 is an electronic control unit (ECU) for controlling the automatic transmission, 1
03 is an oil temperature input processing unit. 104 is a throttle signal (V _th ) input processing unit, 105 is a throttle signal (V _ref ) input processing unit, 106 is a vehicle speed signal input processing unit,
Reference numeral 107 denotes an A / D port AN ₅ for information from each input processing unit.
.About.An ₇ is a microcomputer to take via a (MPU). 108 is a microcomputer (M
PU) 107, the automatic transmission 10
1 is a solenoid output processing unit that outputs control signals to various solenoids in 1.

This embodiment is an electronic control system that does not require such an oil temperature sensor. That is, as shown in FIG. 2, the conventional oil temperature input circuit 10 is used as a front channel of the throttle circuit while leaving it as it is.
In other words, with the power supply voltage V _CC terminal 12 5V power supply, it pulls up at 5V at the time of scanning the previous channel of the throttle circuit, charges the A / D conversion capacitor _CAD 51, and fails at the time of scanning the throttle circuit channel. The configuration is such that the voltage of the A / D conversion capacitor C _AD 51 for which the determination can be sufficiently performed is maintained.

The operation in the scan mode of the first embodiment will be described below with reference to FIG. (1) First, the channel before the throttle circuit is scanned. That is, the switch SW ₁ 33 in FIG.
(Step S1). (2) Then, at a voltage of A / D port AN ₅ 31 A / D
The conversion capacitor C _AD 51 is charged (Step S)
2).

(3) Next, the switch SW ₁ 33 is turned off.
(Step S3). (4) Then, the voltage of the A / D port AN ₅ 31 A / D
Conversion is performed (step S4). (5) Next, the channel of the throttle circuit is scanned. That is, the switch SW ₂ 43 in FIG. 2 is turned on (step S5).

[0022] (6) Then, A / D port AN ₆ 41 A / D conversion capacitor C _AD 51 at a voltage is charged (step S6). In the conventional case, sufficient charging cannot be performed due to leakage current. However, in this case, since a 5 V pull-up is performed in the scan of the channel before the throttle circuit, sufficient charging is performed. . (7) Next, turns OFF the switch SW ₂ 43 (step S7).

[0023] (8) Then, the voltage of the A / D port AN ₆ 41 A / D converts (step S8). (9) When the scanning of the predetermined channel is completed, the process returns to step S1 (step 9), and the scanning is sequentially repeated. As described above, according to the first embodiment, the channel before the throttle circuit is pulled up to 5 V by leaving the oil temperature input circuit 10 as it is. The voltage of the A / D conversion capacitor is reduced during the / D conversion and does not fall below the fail determination value. This makes it possible to reliably perform the fail determination, promote the general use of the electronic control system, and increase the cost. There is.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram of an electronic control system of an automatic transmission according to a second embodiment of the present invention, FIG. 5 is a circuit diagram of a throttle sensor open failure detection circuit according to the second embodiment of the present invention, and FIG. 4 is a flowchart illustrating a throttle sensor open failure detection according to the embodiment. In this embodiment, the same parts as those in the conventional example or the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 5, the electronic control system for this automatic transmission is a case where the conventional oil temperature sensor shown in FIG. 12 is used as it is. In this case, if the throttle sensor is opened in the normal scan mode, the problem as described in the problem of the related art will occur. Therefore, in this embodiment, as shown in FIG. The 5V power supply 34 and the resistor R35 are connected to the channel before the circuit so that the channel can be pulled up by the 5V power supply 34.

The operation in the scan mode of the second embodiment will be described below with reference to FIG. (1) First, the channel before the throttle circuit is scanned. That is, the switch SW ₁ 33 in FIG.
(Step S11). (2) Then, at the voltage of the A / D port AN ₄ 31A, A
The / D conversion capacitor C _AD 51 is charged (step S12).

(3) Next, the switch SW ₁ 33 is turned off.
(Step S13). (4) Next, the voltage of the A / D port AN ₄ 31A is changed to A / D
Conversion is performed (step S14). (5) Next, the switch SW ₁₂ 36 is turned on to perform a pull-up of 5 V (step S15).

(6) Then, the A / D conversion capacitor C
_{The AD} 51 is charged (Step S16). (7) Next, the channel of the throttle circuit is scanned. That is, the switch SW ₂ 43 in FIG. 5 is turned ON (step S17). (8) Then, in the voltage of the A / D port AN ₆ 41 A / D
The conversion capacitor C _AD 51 is charged (step S1)
8). In the conventional case, a sufficient charge cannot be performed due to a leak current. However, in this case, even if a leak current occurs, the A / D conversion capacitor _CAD 51 is charged in advance by the pull-up 5V power supply 34, The fail judgment value is guaranteed.

(9) Next, the switch SW ₂ 43 is turned off.
(Step S19). (10) Then, the voltage of the A / D port AN ₆ 41 A /
D conversion is performed (step S20). (11) When the scanning of the predetermined channel is completed, the process returns to step S11 (step 21), and the scanning is sequentially repeated.

As described above, according to the second embodiment, even when the channel of the oil temperature sensor circuit is used as it is, since the channel is pulled up to 5 V during scanning of the channel of the throttle circuit, the throttle sensor open failure At the time of A / D conversion of the throttle voltage at the time, the voltage of the A / D conversion capacitor is reduced and does not fall below the fail determination value, so that the fail determination can be reliably performed.

FIG. 7 is a circuit diagram of a throttle sensor open failure detecting circuit according to a third embodiment of the present invention. In this embodiment, as shown in FIG. 7, the A / D port AN is connected to the channel in front of the throttle circuit so that the channel can be pulled down.
₅ 31B is grounded and the power supply voltage V _CC terminal 21 of the throttle input circuit 20 (see FIG. 5).
_{So that} the load side of the resistor R ₁₅₆ is grounded via the resistor R ₁₅₉ 38.

The operation in the scan mode of the third embodiment will be described below with reference to FIG. (1) First, the channel before the throttle circuit is scanned. That is, the switch SW ₁ 33 in FIG. 7 is turned ON.
(Step S21). (2) Then, at the voltage of the A / D port AN ₄ 31A, A
The / D conversion capacitor _CAD 51 is charged (step S22).

(3) Next, the switch SW ₁ 33 is turned off.
(Step S23). (4) Next, the voltage of the A / D port AN ₄ 31A is changed to A / D
Conversion is performed (step S24). (5) Next, the switch SW ₁₃ 37 is turned ON, and pull-down is performed in advance so that detection cannot be performed in a low area (step S25).

(6) Then, the A / D conversion capacitor C
The potential of the _AD 51 shifts to the potential of the pull-down region (Step S26). (7) Next, the channel of the throttle circuit is scanned. That is, the switch SW ₂ 43 in FIG. 7 is turned ON (step S27). (8) Then, the voltage of the A / D port AN ₆ 41 is A / D
The voltage is applied to the conversion capacitor C _AD 51 (step S2).
8).

(9) Next, the switch SW ₂ 43 is turned off.
(Step S29). (10) Then, the voltage of the A / D port AN ₆ 41 A /
D conversion is performed (step S30). Then, as shown in FIG. 9, it becomes possible to determine whether the throttle sensor has failed in the pull-down area PD. In FIG. 9, PU indicates a pull-up area.

(11) When the scanning of the predetermined channel is completed, the process returns to step S21 (step 3).
1) Repeat scanning sequentially. As described above, according to the third embodiment, even when the channel of the oil temperature sensor circuit is used as it is, the voltage of the A / D conversion capacitor is changed at the time of A / D conversion of the throttle voltage when the throttle sensor is open. Since the voltage is reduced by pulling down in advance, it is possible to perform detection in a low region, and it is possible to reliably perform a fail determination.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is an electronic control system configuration diagram of an automatic transmission according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a throttle sensor open failure detection circuit according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a throttle sensor open failure detection according to the first embodiment of the present invention.

FIG. 4 is an electronic control system configuration diagram of an automatic transmission according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a throttle sensor open failure detection circuit according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a throttle sensor open failure detection according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a throttle sensor open failure detection circuit according to a third embodiment of the present invention.

FIG. 8 is a flowchart illustrating a throttle sensor open failure detection according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram of a pull-down detection area according to a third embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional throttle sensor open failure detection circuit.

FIG. 11 is a diagram showing time constants of various parts of a conventional throttle sensor open failure detection circuit.

FIG. 12 is a time chart showing an A / D conversion operation of a conventional throttle sensor open failure detection circuit.

[Explanation of symbols]

1 oil temperature sensor 2 throttle sensor 3 switches 4 input lines 10 oil temperature input circuit 11,14,23,25 capacitor 12,16,21,26 supply voltage V _CC terminal 13,15,19,22,24,29 , 38 resistors 17, 18, 27 and 28 diodes 20 throttle input circuits 31,31B A / D port AN ₅ 31A A / D port AN ₄ 32 A / D conversion resistor R _AD 33 switches SW ₁ 34 5V supply 35 resistor R 36 Switch SW ₁₂ 37 Switch SW ₁₃ 41 A / D port AN ₆ 42 A / D conversion resistor R _AD 43 Switch SW ₂ 51 A / D conversion capacitor C _AD 101 Automatic transmission 102 Electronic control unit (ECU) 103 Oil temperature input processor 104 throttle signal (V _th) input processing unit 105 throttle signal (V _ref) input unit 106 vehicle speed Signal input processing unit 107 microcomputer (MPU) 108 solenoid output processing unit

Claims (2)

[Claims] 1. A sensor open failure detection device, comprising: a circuit for pulling up or pulling down a first channel in front of a sensor circuit, for A / D conversion during scanning of a second channel connected to the sensor circuit. A sensor open failure detecting device for maintaining a voltage of a capacitor at a voltage capable of detecting a failure. 2. The sensor open failure detecting device according to claim 1, wherein the sensor connected to the second channel is a throttle sensor.