JP7465223B2 - Substrate having oxygen concentration sensor signal input circuit and electronic control device equipped with same - Google Patents

Description

The present invention relates to a substrate having an oxygen concentration sensor signal input circuit interposed between an oxygen concentration sensor and an A/D converter, and an electronic control device equipped with the same.

Conventionally, a signal input circuit is known that is interposed between an oxygen concentration sensor and an A/D converter, converts the output signal of the oxygen concentration sensor into an appropriate signal, and supplies the signal to the A/D converter (see, for example, Patent Documents 1 and 2).

Patent Document 1 discloses a signal input circuit suitable for a resistance-type oxygen concentration sensor. This signal input circuit detects (takes in) the output signal of the oxygen concentration sensor centered on a bias point set by dividing the power supply voltage by a first resistor and a second resistor, and supplies the signal to an A/D converter. A capacitor for noise removal is provided between the bias point and the ground point. A filter circuit is also provided between the bias point and the A/D converter.

On the other hand, Patent Document 2 discloses a signal input circuit suitable for a concentration cell type oxygen concentration sensor. This signal input circuit is capable of freely supplying a discharge current to the oxygen concentration sensor. This signal input circuit includes an operational amplifier that constitutes a voltage follower, and the current value of the discharge current is set so that the voltage waveform in the detection signal of the oxygen concentration sensor crosses the detection threshold on the low voltage side.

JP 2003-129894 A JP 2011-203131 A

However, according to the techniques of Patent Documents 1 and 2, as described above, the appropriate signal input circuit configurations differ between resistance-type oxygen concentration sensors and concentration cell-type oxygen concentration sensors. Therefore, depending on which type of oxygen concentration sensor is used, it is necessary to use different boards and electronic components for providing the signal input circuit. For this reason, when manufacturing both types of oxygen concentration sensors as needed, there is a risk of increased costs for manufacturing and production management.

In view of the problems with the conventional technology, the object of the present invention is to provide a signal input circuit board that is highly versatile and can be used with both resistive and concentration cell type oxygen concentration sensors, and an electronic control device having the same, which is small and low cost.

The substrate having the oxygen concentration sensor signal input circuit of the present invention is
A substrate having an oxygen concentration sensor signal input circuit comprising: an input terminal for receiving an analog signal from an oxygen concentration sensor having a detection portion provided so as to be in contact with exhaust gas from an internal combustion engine; an A/D converter for converting the analog signal into a digital signal; and a signal conductor portion interposed between the A/D converter and the input terminal, the signal conductor portion being configured by mounting a plurality of electronic components thereon,
The detection unit can be selectively set to a resistance type oxygen concentration sensor or a concentration cell type oxygen concentration sensor,
the signal conductor portion has a first signal path for inputting a signal from the resistance-type oxygen concentration sensor to the A/D converter, and a second signal path for inputting a signal from the concentration cell-type oxygen concentration sensor to the A/D converter,
The first signal path is
a reference voltage unit having lands and patterns for mounting a first resistor and a second resistor connected between a power supply voltage and a ground point (GND), the reference voltage unit setting a bias voltage for detecting the analog signal from the input terminal by the first resistor and the second resistor;
a first reference setting conductor section having a land and a pattern for mounting a third resistor connected between a connection point between the first and second resistors and a first branch point of the signal conductor section connected to the input terminal, the first reference setting conductor section being configured to be able to pull up the first branch point;
a first low-pass filter section having a land and a pattern for mounting a fourth resistor connected between the first branch point and a second branch point connected to the A/D converter, and a first capacitor connected between the second branch point and the ground point (GND), the first low-pass filter section constituting a low-pass filter capable of removing noise at the first branch point together with the fourth resistor and the first capacitor;
The second signal path is
a second low-pass filter section including a land and a pattern for mounting a first branch conductor section branched from the first branch point, a fifth resistor connected to the first branch conductor section, and a second capacitor connected between the fifth resistor and the ground point (GND), and capable of removing noise at the first branch point;
a third low-pass filter section including a second branch conductor section branched from the second branch point, and a land and a pattern for mounting a sixth resistor connected to the second branch conductor section, the third low-pass filter section configuring a low-pass filter together with the sixth resistor and a first capacitor;
a second reference setting conductor portion including a land and a pattern for mounting a diode connected between the second branch point and the power supply voltage, the second reference setting conductor portion pulling up the second branch point via the diode;
a connection point conductor portion branched from a connection point between the second capacitor and the fifth resistor in the second low-pass filter portion, and a voltage follower portion including a land and a pattern for mounting an operational amplifier connected between the connection point conductor portion and the sixth resistor, and capable of configuring a voltage follower;
A first electronic component group consisting of the first to fourth resistors and the first capacitor, and a second electronic component group consisting of the fifth resistor, the second capacitor, the operational amplifier, the sixth resistor, the diode, and the first capacitor are selectively connected to enable the first and second signal paths.

In the configuration of the present invention, when a first signal path is enabled by connecting a first electronic component group consisting of the first to fourth resistors and a first capacitor to a substrate having an oxygen concentration sensor signal input circuit, a signal from the resistive oxygen concentration sensor can be input to an A/D converter by setting the resistive oxygen concentration sensor as the detection unit of the oxygen concentration sensor.

On the other hand, when a second electronic component group consisting of a fifth resistor, a second capacitor, an operational amplifier, a sixth resistor, a diode, and a first capacitor is connected to a board having an oxygen concentration sensor signal input circuit to activate a second signal path, a concentration cell type oxygen concentration sensor can be set as the detection unit of the oxygen concentration sensor, and a signal from the concentration cell type oxygen concentration sensor can be input to the A/D converter.

As a result, a single substrate can accommodate both resistive (e.g., titania) sensors and concentration cell (e.g., zirconia) sensors. Therefore, when manufacturing an electronic control device that includes a substrate having an oxygen concentration sensor signal input circuit, there is no need to remake the substrate so that a substrate corresponding to the type of oxygen concentration sensor to be set as the detection unit can be used. This makes it possible to reduce the costs of manufacturing and managing production of electronic control devices.

In addition, because no jumper chips or the like are used to switch between the first and second signal paths, the number of electronic components used can be reduced. This makes it possible to minimize the tolerance in accuracy of reading the signal from the oxygen concentration sensor, which is caused by the manufacturing tolerance of each component.

In addition to the above-mentioned characteristic configuration, the present invention is characterized by having at least two or more systems of oxygen concentration sensor signal input circuits each consisting of one input terminal, the first signal path, and the second signal path, and by selectively connecting the first electronic component group or the second electronic component group to each system, the first and second signal paths are enabled, and the detection unit can be alternatively set to either a resistive oxygen concentration sensor or a concentration cell type oxygen concentration sensor for each system.

In general, oxygen concentration sensors are installed before and after a three-way catalyst in the exhaust pipe of an internal combustion engine. For this reason, an actual electronic control unit (ECU) that corresponds to this usually has two or more oxygen concentration sensor signal input circuits.

In this regard, according to the present invention, two or more systems each having one input terminal, a first signal path, and a second signal path can be provided, and each system can be selectively connected to either the first group of electronic components or the second group of electronic components. For example, a resistive type (e.g., titania type) oxygen concentration sensor, which is considered to be relatively non-toxic, can be set in the first system, and a concentration cell type (e.g., zirconia type) oxygen concentration sensor can be set in the second system, thereby providing a low-cost electronic control device with excellent versatility.

The electronic control device of the present invention is characterized in that, in an electronic control device having a substrate having the oxygen concentration sensor signal input circuit described above and setting the resistive oxygen concentration sensor in a detection section, the first electronic component group is mounted to enable the first signal path, and the ratio of the resistance value of the first resistor to the resistance value of the second resistor is approximately 0.109, and the ratio of the resistance value of the second resistor to the resistance value of the third resistor is approximately 6.111.

According to this, when a resistive oxygen concentration sensor is set as the oxygen concentration sensor and the air-fuel ratio is detected based on the voltage signal from the resistive oxygen concentration sensor, in the region of exhaust temperature (= temperature of the oxygen concentration sensor) where air-fuel ratio detection is required, the resistance values of the first and second resistors acting as voltage dividing resistors can be set to obtain the maximum possible voltage resolution by adjusting the dynamic range of the sensor signal to the allowable voltage range of the A/D converter while avoiding signal clipping and preventing conflicts with the OBD (on-board diagnosis) function. This setting can be realized while minimizing the number of components in the circuit configuration as much as possible.

In addition, by reducing the number of parts, it is possible to minimize the tolerance in the accuracy of reading the voltage signal from the resistive oxygen concentration sensor due to manufacturing tolerances of the parts, and to reduce manufacturing costs.

The electronic control device of the present invention is characterized in that, in the electronic control device that includes a substrate having the oxygen concentration sensor signal input circuit described above and that sets the concentration cell type oxygen concentration sensor as the detection unit, the second electronic component group is mounted, the second signal path is enabled, and the capacitance of the second capacitor is smaller than the capacitance of the first capacitor.

According to this, when a concentration cell type oxygen concentration sensor is set as the oxygen concentration sensor and the air-fuel ratio is detected based on the voltage signal from the concentration cell type oxygen concentration sensor, the second signal path is enabled and a voltage follower type input circuit suitable for the concentration cell type oxygen concentration sensor is formed, so that the signal from the concentration cell type oxygen concentration sensor can be input to the A/D converter with high accuracy.

1A is a circuit diagram showing a state when a first signal path is enabled in a substrate having an oxygen concentration sensor signal input circuit according to one embodiment of the present invention, and FIG. 1B is a circuit diagram showing a state when a second signal path is enabled in the substrate. FIG. 2 is a perspective view illustrating a configuration of a substrate.

Below, an embodiment of the present invention will be described with reference to the drawings. Fig. 1(a) shows the circuit state when a first group of electronic components is connected to one aspect A of a board 1 having an oxygen concentration sensor signal input circuit according to one embodiment of the present invention, and a first signal path 2 is enabled. Fig. 1(b) shows the circuit state when a second group of electronic components is connected to another aspect B of the board 1, and a second signal path 3 is enabled. The board 1 shown in Figs. 1(a) and (b) constitutes part of a board having other components and circuits that constitute an electronic control unit (ECU).

As shown in Figures 1(a) and (b), the substrate 1 includes one input terminal 5 to which an analog signal is input from an oxygen concentration sensor 4 (4a, 4b) having a detection portion arranged so as to be in contact with the exhaust gas of an internal combustion engine, an A/D converter 6 that converts the analog signal into a digital signal, and a signal conductor portion 7 interposed between the A/D converter 6 and the input terminal 5. An oxygen concentration sensor signal input circuit is formed by mounting multiple electronic components on the signal conductor portion 7.

As described below, the oxygen concentration sensor 4 can be alternatively set as its detection section to either a resistance-type oxygen concentration sensor 4a or a concentration cell-type oxygen concentration sensor 4b.

The signal conductor section 7 has a first signal path 2 that inputs a signal from the resistive oxygen concentration sensor 4a to the A/D converter 6, and a second signal path 3 that inputs a signal from the concentration cell type oxygen concentration sensor 4b to the A/D converter 6.

The first signal path 2 has a land and a pattern for implementing a first resistor R1 and a second resistor R2 that are connected between the power supply voltage VCC and a ground point (LG; logic circuit ground), and includes a reference voltage unit 8 that sets a bias voltage for detecting an analog signal from the input terminal 5 using the first resistor R1 and the second resistor R2.

A typical example of a land and a pattern is shown in FIG. 2. As shown in FIG. 2, the land 9 is a portion of the substrate portion 10 of the substrate 1 where the copper foil constituting the pattern 12 is exposed so that the lead of the component 11 can be soldered. The pattern 12 is a portion of the copper foil for conducting the lands 9 together. A through hole 13 is provided to connect the pattern 12 on one side of the substrate portion 10 to the pattern 12 on the other side. The through hole 13 can function as, for example, the first and second branch points described later. In a multilayer substrate (not shown) in which the substrate portion 10 of the substrate 1 is provided in multiple layers, a part of the pattern 12 is disposed in an intermediate layer between an upper substrate portion facing the one side and a lower substrate portion facing the other side, and is connected to the land 9 via the through hole 13, thereby reducing the area occupied by the pattern 12 on the substrate 1.

Returning to FIG. 1, the first signal path 2 also has a land and pattern for implementing a third resistor R3 connected between the connection point between the first and second resistors R1 and R2 and a first branch point B1 of the signal conductor section 7 connected to the input terminal 5, and includes a first reference setting conductor section 14 configured to be able to pull up the first branch point B1.

The first signal path 2 also includes a land and pattern for mounting a fourth resistor R4 connected between the first branch point B1 and a second branch point B2 connected to the A/D converter 6, and a first capacitor C1 connected between the second branch point B2 and the ground point (LG), and includes a first low-pass filter section 15 in which the fourth resistor R4 and the first capacitor C1 constitute a low-pass filter capable of removing noise at the first branch point B1.

The second signal path 3 includes a first branch conductor section 16 branched from the first branch point B1, a fifth resistor R5 connected to the first branch conductor section 16, and a land and pattern for mounting a second capacitor C2 connected between the fifth resistor R5 and the ground point (LG), and includes a second low-pass filter section 17 capable of removing noise at the first branch point B1.

The second signal path 3 also includes a second branch conductor section 18 branched off from the second branch point B2, a land and pattern for mounting a sixth resistor R6 connected to the second branch conductor section 18, and a third low-pass filter section 19 that constitutes a low-pass filter together with the sixth resistor R6 and the first capacitor C1.

The second signal path 3 also includes a land and pattern for implementing a diode D connected between the second branch point B2 and the power supply voltage VCC, and includes a second reference setting conductor portion 20 that pulls up the second branch point B2 via the diode D.

The second signal path 3 further includes a connection point conductor section 21 branched off from the connection point between the second capacitor C2 and the fifth resistor R5 in the second low-pass filter section 17, and a voltage follower section 23 that can configure a voltage follower by including a land and pattern for implementing an operational amplifier 22 connected between the connection point conductor section 21 and the sixth resistor R6.

The substrate 1 has a shape in which a first electronic component group consisting of the first to fourth resistors R1 to R4 and the first capacitor C1 and a second electronic component group consisting of the fifth resistor R5, the second capacitor C2, the operational amplifier 22, the sixth resistor R6, the diode D, and the first capacitor C1 are selectively connected to enable the first and second signal paths 2 and 3.

When the first electronic component group is mounted and the first signal path 2 is enabled as in aspect A of the board 1, the dynamic range (the ratio of the minimum and maximum readable signals) of the signal waveform from the resistive oxygen concentration sensor 4a input to the A/D converter 6 at the first branch point B1, which is pulled up by the reference voltage unit 8, changes. Therefore, it is necessary to change the settings of the first to third resistors R1 to R3 associated with the first branch point B1 to match the dynamic range of the sensor signal within the allowable voltage range of the A/D converter 6 (between the power supply voltage VCC and ground) while at the same time avoiding signal clipping on the power supply voltage VCC side or the ground side. In this aspect A, for example, it is preferable that the ratio (Ra/Rb) of the resistance value Ra of the first resistor R1 to the resistance value Rb of the second resistor R2 is close to 0.109, and the ratio (Rb/Rc) of the resistance value Rb of the second resistor R2 to the resistance value Rc of the third resistor R3 is close to 6.111. In this configuration, by setting the resistance type oxygen concentration sensor 4a as the detection unit, the signal from the resistance type oxygen concentration sensor 4a can be appropriately input to the A/D converter 6.

In addition, as in another aspect B of the board 1, when the second electronic component group consisting of the fifth resistor R5, the second capacitor C2, the operational amplifier 22, the sixth resistor R6, the diode D, and the first capacitor C1 is mounted and the second signal path 3 is enabled, the impedance (ratio of voltage to current) changes before and after the operational amplifier 22, so it is necessary to change the settings of the second and third low-pass filter sections 17 and 19 before and after the operational amplifier 22 to achieve impedance matching and optimize the noise index. In this aspect B, it is preferable that the capacitance of the second capacitor C2 is smaller than the capacitance of the first capacitor C1, and in this configuration, by setting the concentration cell type oxygen concentration sensor 4b as the detection section, the input signal from the concentration cell type oxygen concentration sensor 4b can be input to the A/D converter 6 with high accuracy.

Therefore, a single substrate 1 can accommodate both resistive (e.g., titania) sensors and concentration cell (e.g., zirconia) sensors.

As described above, according to this embodiment, one board 1 can accommodate both resistance-type sensors and concentration cell-type sensors, so when manufacturing an electronic control device equipped with the board 1, there is no need to remake the board so that a board corresponding to the type of oxygen concentration sensor set as the detection unit of the oxygen concentration sensor 4 can be used. This makes it possible to reduce the costs of manufacturing and production management of electronic control devices having an oxygen concentration sensor signal input circuit.

In addition, since no jumper chips or the like are used to switch between the first and second signal paths 2 and 3, the number of electronic components used can be reduced. This makes it possible to minimize the tolerance in accuracy of reading the signal from the oxygen concentration sensor, which is caused by the manufacturing tolerance of each component.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, an oxygen concentration sensor is generally placed before and after a three-way catalyst in the exhaust pipe of an internal combustion engine. For this reason, an actual electronic control unit (ECU) corresponding to this usually has two or more oxygen concentration sensor signal input circuits.

Therefore, a substrate may be provided that has a multi-system oxygen concentration sensor signal input circuit that has one input terminal 5, a first signal path 2, and a second signal path 3 on the substrate 1, and either the connection of the first electronic component group described above or the connection of the second electronic component group described above may be set individually for each of the systems.

According to this, for example, a low-cost electronic control device with excellent versatility can be provided by connecting a first and second electronic component group to the first and second systems, respectively, and setting a resistive type (e.g., titania type) oxygen concentration sensor, which is considered to be relatively non-toxic, in the first system, and setting a concentration cell type (e.g., zirconia type) oxygen concentration sensor in the second system.

1...substrate, 2...first signal path, 3...second signal path, 4...oxygen concentration sensor, 4a...resistance type oxygen concentration sensor, 4b...concentration cell type oxygen concentration sensor, 5...input terminal, 6...A/D converter, 7...signal conductor section, 8...reference voltage section, 9...land, 10...substrate section, 11...component, 12...pattern, 13...through hole, 14...first reference setting conductor section, 15...first low pass filter section, 16...first branch conductor section, 17...second low pass filter section, 18...second branch conductor section, 19...third low pass filter section, 20...second reference setting conductor section, 21...connection point conductor section, 22...op-amp, 23...voltage follower section, B1...first branch point, B2...second branch point, C1...first capacitor, C2...second capacitor, R1 to R6...first to sixth resistors.

Claims (4)

A substrate having an oxygen concentration sensor signal input circuit comprising: an input terminal for receiving an analog signal from an oxygen concentration sensor having a detection portion provided so as to be in contact with exhaust gas from an internal combustion engine; an A/D converter for converting the analog signal into a digital signal; and a signal conductor portion interposed between the A/D converter and the input terminal, the signal conductor portion being configured by mounting a plurality of electronic components thereon,
The detection unit can be selectively set to a resistance type oxygen concentration sensor or a concentration cell type oxygen concentration sensor,
the signal conductor portion has a first signal path for inputting a signal from the resistance-type oxygen concentration sensor to the A/D converter, and a second signal path for inputting a signal from the concentration cell-type oxygen concentration sensor to the A/D converter,
The first signal path is
a reference voltage section having lands and patterns for mounting a first resistor and a second resistor connected between a power supply voltage and a ground point, the reference voltage section setting a bias voltage for detecting the analog signal from the input terminal by the first resistor and the second resistor;
a first reference setting conductor section having a land and a pattern for mounting a third resistor connected between a connection point between the first and second resistors and a first branch point of the signal conductor section connected to the input terminal, the first reference setting conductor section being configured to be able to pull up the first branch point;
a first low-pass filter section having a land and a pattern for mounting a fourth resistor connected between the first branch point and a second branch point connected to the A/D converter, and a first capacitor connected between the second branch point and the ground point, the first low-pass filter section constituting a low-pass filter capable of removing noise at the first branch point together with the fourth resistor and the first capacitor;
The second signal path is
a second low-pass filter section including a land and a pattern for mounting a first branch conductor section branched from the first branch point, a fifth resistor connected to the first branch conductor section, and a second capacitor connected between the fifth resistor and the ground point, the second low-pass filter section being capable of removing noise at the first branch point;
a third low-pass filter section including a second branch conductor section branched from the second branch point, and a land and a pattern for mounting a sixth resistor connected to the second branch conductor section, the third low-pass filter section configuring a low-pass filter together with the sixth resistor and a first capacitor;
a second reference setting conductor portion including a land and a pattern for mounting a diode connected between the second branch point and the power supply voltage, the second reference setting conductor portion pulling up the second branch point via the diode;
a connection point conductor portion branched from a connection point between the second capacitor and the fifth resistor in the second low-pass filter portion, and a voltage follower portion including a land and a pattern for mounting an operational amplifier connected between the connection point conductor portion and the sixth resistor, and capable of configuring a voltage follower;
A substrate having an oxygen concentration sensor signal input circuit, characterized in that a first electronic component group consisting of the first to fourth resistors and the first capacitor, and a second electronic component group consisting of the fifth resistor, the second capacitor, the operational amplifier, the sixth resistor, the diode, and the first capacitor are selectively connected to enable the first and second signal paths. 2. A board having an oxygen concentration sensor signal input circuit as described in claim 1, characterized in that the board has at least two or more systems of oxygen concentration sensor signal input circuits each consisting of the one input terminal, the first signal path, and the second signal path, and the first electronic component group or the second electronic component group is selectively connected for each system to enable the first and second signal paths, and the detection unit can be alternatively set to either a resistive oxygen concentration sensor or a concentration cell type oxygen concentration sensor for each system. An electronic control device comprising a substrate having the oxygen concentration sensor signal input circuit according to claim 1 or 2, and setting the resistive oxygen concentration sensor in the detection section, characterized in that the first electronic component group is mounted to enable the first signal path, and the ratio of the resistance value of the first resistor to the resistance value of the second resistor is approximately 0.109, and the ratio of the resistance value of the second resistor to the resistance value of the third resistor is approximately 6.111. An electronic control device comprising a substrate having the oxygen concentration sensor signal input circuit according to claim 1 or 2, and setting the concentration cell type oxygen concentration sensor as the detection unit, characterized in that the second electronic component group is mounted, the second signal path is enabled, and the capacitance of the second capacitor is smaller than the capacitance of the first capacitor.

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