JP2019035338A - Control device - Google Patents

Abstract

To provide a control device capable of reducing an influence of temperature characteristics of a particulate matter, which is used together with an electric resistance type PM sensor.SOLUTION: A control device used together with an electric resistance type PM sensor that outputs a first signal indicating a resistance value between electrodes provided on an insulator exposed to exhaust gas, includes: a temperature sensor that outputs a second signal indicating a peripheral temperature; a heat generator that receives power supply and generates heat; a response delay compensation part for controlling the power supply to the heat generator so that the temperature indicated by the second signal coincides with a predetermined temperature which is lower than a regeneration temperature of the PM sensor, and is set based on an exhaust gas temperature; and a PM amount derivation part for deriving an amount of a particulate matter in the exhaust gas based on the first signal and the second signal.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a control device for an electrical resistance PM sensor.

  Conventionally, an electrical resistance PM sensor that outputs a signal correlated with the amount of particulate matter contained in exhaust gas is sometimes provided in a flow path of exhaust gas generated in an internal combustion engine.

  This type of PM sensor includes an insulating substrate as an example of an insulator, and a pair of electrodes that are spaced apart from each other on the surface of the insulator.

  Since the particulate matter is mainly composed of conductive soot, when a certain amount or more of particulate matter is deposited between the electrodes, a conductive path is formed between the electrodes. In addition, the resistance value of the conductive path changes according to the amount of particulate matter deposited.

  For example, a voltage having a predetermined value (for example, a constant voltage) is applied between the electrodes, so that a signal correlated with the resistance value of the conductive path (in other words, the amount of deposited particulate matter) is output from the electrode pair. .

  Also, in order to remove the particulate matter deposited around the electrodes, the heating element that heats the insulator and the power supply to the heating element so that the substrate temperature matches the temperature at which all of the particulate matter can be combusted. A power control unit for controlling the power supply.

Japanese Patent Laying-Open No. 2015-175321

  The exhaust gas temperature varies greatly depending on the operating condition of the internal combustion engine, and the resistance value of the particulate matter has temperature dependence (hereinafter simply referred to as temperature characteristics). Even under such circumstances, it is required to more accurately derive the amount of particulate matter deposited based on the output signals from the pair of electrodes.

  The objective of this indication is a control apparatus used with an electrical resistance type PM sensor, Comprising: It is providing the control apparatus which can reduce the influence of the temperature characteristic of a particulate matter.

  One form of the present disclosure is a control device that is used together with an electrical resistance type PM sensor that outputs a first signal indicating a resistance value between electrodes provided on an insulator exposed to exhaust gas. A temperature sensor that outputs a second signal representing temperature, a heating element that generates heat upon receiving power supply, a temperature represented by the second signal, and a temperature that is less than the regeneration temperature of the PM sensor and is set based on the exhaust gas temperature. PM for deriving the amount of particulate matter in the exhaust gas based on the response delay compensator for controlling the power supply to the heating element and the first signal and the second signal so as to match the predetermined temperature And a quantity derivation unit.

  According to the present disclosure, it is possible to provide a heating device that can be used together with an electric resistance PM sensor and can reduce the influence of the temperature characteristics of the particulate matter.

The figure which shows the structure of the exhaust system in which the control apparatus regarding one Embodiment of this indication is used. Flow chart of the control device of FIG.

  Hereinafter, the control apparatus 1 will be described in detail with reference to the above drawings. Prior to that, terms are first defined.

<1. Definition>
Table 1 below shows the meaning of acronyms and abbreviations used in this embodiment.

<2. Schematic configuration of control device and PM sensor>
As shown in FIG. 1, a control device 1, an exhaust system 3, and a PM sensor 5 are mounted on a transport device V (for example, a vehicle).

  Hereinafter, the exhaust system 3 and the PM sensor 5 will be described prior to the control device 1.

  The exhaust system 3 is connected to an internal combustion engine (not shown). The internal combustion engine is a diesel engine or a gasoline engine (particularly a direct injection engine), and generates exhaust gas.

  The exhaust system 3 has an exhaust gas passage 31. The exhaust gas passage 31 guides exhaust gas generated in the internal combustion engine to the atmosphere (outside the vehicle). The exhaust gas flow path 31 is provided with a PM filter 33 as an exhaust gas aftertreatment device.

  The PM filter 33 is, for example, a DPF or a GPF. The PM filter 33 is a so-called wall flow filter, which is made of ceramic and has a cylindrical honeycomb carrier.

  When the PM filter 33 is manufactured, a large number of holes penetrating both end faces of the honeycomb carrier are formed, and then the openings on the upstream end face and the downstream end face are alternately sealed to form semi-through holes (that is, cells). It is formed. As a result, the PM filter 33 passes through the upstream end face (ie, the opening of the cell), the upstream side cell, the honeycomb wall surface (the partition wall of two adjacent cells), and the downstream side cell. A flow path for exhaust gas reaching the opening of the side end face (opening of the adjacent cell) is formed. Note that a noble metal catalyst (oxidation catalyst) may be supported or coated on the honeycomb wall surface.

  The exhaust gas guided from the upstream side of the exhaust gas passage 31 passes through the PM filter 33 having the above configuration. In the process, particulate matter in the exhaust gas is deposited and collected on the upstream surface of the honeycomb wall surface. Further, the exhaust gas that has passed through the PM filter 33 is treated with a well-known SCR or the like to be rendered harmless, and then discharged into the atmosphere via a muffler (not shown).

  The PM sensor 5 is a so-called electric resistance type PM sensor. For example, the PM sensor 5 is disposed immediately downstream of the PM filter 33 in the exhaust gas passage 31 and is exposed to the exhaust gas passing therethrough. As a result, particulate matter in the exhaust gas is accumulated inside the PM filter 33, and a first signal that changes in accordance with the amount of accumulation is output to the control device 1.

  The PM sensor 5 is not limited to the immediate downstream side of the PM filter 33, and may be provided at other locations such as the upstream side of the PM filter 33.

  Here, a perspective view of the main part of the PM sensor 5 is drawn in the ellipse of FIG. Hereinafter, the principal part of the PM sensor 5 will be described in detail with reference to this.

  The PM sensor 5 includes an insulator 51 and at least a pair of electrodes 53.

  The insulator 51 is made of a material having electrical insulation (for example, heat-resistant ceramic), and is, for example, an insulating substrate having two main surfaces 51a and 51b facing each other in a predetermined direction.

  The pair of electrodes 53 is made of a conductive material, and is disposed, for example, on the main surface 51a with a space therebetween. Although the shape of each electrode 53 is not specifically limited, For example, it is a comb-tooth shape.

  The insulator 51 as described above is disposed, for example, such that the pair of electrodes 53 are exposed to the exhaust gas in the exhaust gas flow channel 31 and the main surface 51 a faces the upstream side of the exhaust gas flow channel 31.

  The particulate matter in the exhaust gas is mainly composed of soot having conductivity. Therefore, when a certain amount or more of particulate matter is deposited between the pair of electrodes 53, a conductive path is formed between the pair of electrodes 53. In addition, the resistance value of the conductive path varies depending on the amount of particulate matter deposited.

  A voltage (for example, a constant voltage) Vd having a predetermined value is applied between both terminals of the pair of electrodes 53, for example, under the control of the control unit 17. Therefore, a current Id that correlates with the resistance value of the conductive path (in other words, the amount of particulate matter deposited) flows through a pair of electrodes 53 (hereinafter also referred to as electrode pair 53). This current Id is given to the control unit 17 as a first signal.

  The control device 1 includes a heating element 11, a temperature sensor 13, a power supply circuit 15, and a control unit 17.

  The heating element 11 is made of a conductive material having a relatively high resistance value, and is provided on the insulator 51. Here, the following is illustrated as an aspect with which the heat generating body 11 is provided in the insulator 51. FIG.

  The first mode is as illustrated, and is a mode in which the heating element 11 is provided on the main surface 51 b of the insulator 51. Although not shown, the second mode is a mode in which the heating element 11 is provided so as to be embedded in the insulator 51. Although not shown, the third mode is a mode in which the heating element 11 is provided slightly apart from the insulator 51.

  The heating element 11 has a meandering shape or the like in plan view from the normal direction of the main surface 51b, and converts the electric power supplied from the power supply circuit 15 into heat and releases it under the control of the control unit 17. Thereby, the insulator 51 is heated.

  The temperature sensor 13 is, for example, a chip-type thermistor having a positive or negative temperature characteristic, and may be mounted on the surface of the insulator 51. The temperature sensor 13 outputs a second signal correlated with its ambient temperature to the control unit 17. Here, its own ambient temperature substantially corresponds to the temperature of the particulate matter deposited between the electrodes 53.

  The power supply circuit 15 generates a constant voltage Vd from an output voltage from a battery (not shown) and applies it between the terminals of the electrode 53. The power supply circuit 15 further switches, for example, the output voltage from the battery by a switching element based on a control signal output from the control unit 17 described later, and the pulse voltage obtained thereby is connected between both terminals of the heating element 11. Apply to.

  The control unit 17 is an ECU including an input / output connector, a microcomputer, a program memory, and a main memory mounted on the control board.

  The input / output connector is electrically connected to the temperature sensor 13 and the power supply circuit 15 described above.

  The microcomputer executes the program in the program memory using the main memory, and executes processing as shown in FIG.

<3. Processing of control unit>
In FIG. 2, the microcomputer receives a first signal from the electrode pair 53 and a second signal from the temperature sensor 13 (step S001).

  Next, the microcomputer operates as a response delay compensation unit, and has a first duty ratio so that a deviation between a temperature represented by the second input signal from the temperature sensor 13 and a predetermined temperature is close to zero. A pulsed control signal is generated and output from the input / output connector to the switching element of the power supply circuit 15 (step S003).

  By the process of step S003, the heating element 11 generates heat, and the heating element 11 heats the insulator 51 so that the temperature of the particulate matter deposited between the electrodes 53 becomes a predetermined temperature.

  Here, the predetermined temperature is determined based on an exhaust gas temperature generated in the internal combustion engine that is lower than a regeneration temperature of the PM sensor 5 described later. Here, the temperature of the exhaust gas generated in the internal combustion engine varies greatly depending on the operation state of the internal combustion engine, but in the real world (actual traveling environment), it varies within a certain temperature range to some extent. The temperature range can be obtained in advance by experiments or the like. The predetermined temperature is set to an intermediate value in the temperature range of the exhaust gas, for example.

  If the temperature range of the exhaust gas is about 0 ° C to 400 ° C, the predetermined temperature is set to about 150 ° C to 250 ° C, for example. More preferably, the predetermined temperature is set to an intermediate value of about 200 ° C.

  Next, the microcomputer operates as a PM amount deriving unit, and is based on the resistance value represented by the first input signal from the electrode pair 53 and the temperature represented by the second input signal from the temperature sensor 13. The amount of the substance is derived (step S005).

  Specifically, the program memory stores a map in which the amount of particulate matter in the exhaust gas is described for each combination of the resistance value indicated by the first signal and the temperature indicated by the second signal. The microcomputer reads the amount of the particulate matter specified by the resistance value indicated by the input first signal and the temperature indicated by the input second signal.

After step S005, the microcomputer determines whether or not the execution condition for the regeneration process of the PM sensor 5 is satisfied (step S007). Although the determination criteria of step S007 may be a well-known thing, the following two are illustrated, for example.
Whether or not a predetermined time has elapsed since the previous regeneration process. Whether or not the amount of the particulate matter obtained in step S005 has exceeded a predetermined amount.

  If NO is determined in step S007, the process returns to step S001.

  On the other hand, if “YES” is determined in the step S007, the microcomputer functions as a regeneration processing unit and burns and removes the temperature represented by the second signal received in the step S001 and all the particulate matter deposited on the PM sensor 5. A pulsed control signal having a second duty ratio is generated so that a deviation from a possible temperature (hereinafter referred to as a regeneration temperature) approaches zero, and is output from the input / output connector to the switching element of the power supply circuit 15 (step) S009).

  By the processing in step S009, the heating element 11 heats the insulator 51 so that the temperature of the particulate matter deposited between the electrodes 53 becomes the regeneration temperature (for example, about 600 ° C.). As a result, the particulate matter between the electrodes 53 is completely burned (regeneration processing of the PM sensor 5).

<4. Effect of control device>
The control device 1 of the present disclosure is characterized by executing response delay compensation in step S003. If this step S003 is not executed, the following technical problem arises.

  As described above, the temperature of the exhaust gas generated in the internal combustion engine varies greatly depending on the operating condition of the internal combustion engine within a certain temperature range.

  Further, the resistance value of the particulate matter has temperature characteristics. Specifically, the resistance value of the particulate matter changes exponentially with respect to the temperature of the particulate matter.

  Further, since the operation of the temperature sensor 13 is a thermal phenomenon, there is a response delay.

  Therefore, if step S005 is executed without executing step S003, if the temperature of the exhaust gas (that is, the temperature of the particulate matter) changes significantly, the control unit 17 cannot correctly recognize the current temperature of the particulate matter, and as a result, cannot correctly derive the current amount of the particulate matter.

  However, if step S003 described above is performed and the temperature of the particulate matter between the electrodes 53 is set to the above-described predetermined temperature (preferably, an intermediate value of the exhaust gas temperature range), even if the exhaust gas temperature changes greatly, Compared to the case where step S003 is not executed, the temperature represented by the second signal is more likely to quickly follow the actual temperature of the particulate matter. That is, response delay can be compensated.

  As described above, according to the control device 1 of the present disclosure, it is possible to reduce the influence of the temperature characteristics of the particulate matter, and to derive an amount of the particulate matter that is more suitable for the current situation.

  The control device of the present disclosure can reduce the influence of the temperature characteristics of the particulate matter, and is suitable for transportation equipment.

DESCRIPTION OF SYMBOLS 1 Control apparatus 11 Heating body 13 Temperature sensor 17 Control part 5 PM sensor 51 Insulator 53 Electrode

Claims (2)

A control device used together with an electric resistance type PM sensor that outputs a first signal representing a resistance value between electrodes provided on an insulator exposed to exhaust gas,
A temperature sensor that outputs a second signal representing its ambient temperature;
A heating element that generates heat upon receiving power supply;
A response delay compensation unit that controls power supply to the heating element such that the temperature represented by the second signal matches a predetermined temperature that is lower than the regeneration temperature of the PM sensor and is set based on the exhaust gas temperature; ,
A PM amount deriving unit for deriving the amount of particulate matter in the exhaust gas based on the first signal and the second signal;
A control device comprising: The predetermined temperature is set to an intermediate value in the temperature range of the exhaust gas.
The control device according to claim 1.

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