JP2012127268A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the period for suspending measurement of the amount of PM in exhaust gas due to PM reset for removing fine particles deposited on a PM sensor.SOLUTION: When an internal combustion engine stops, an element of a PM sensor is heated, if the resistance between PM sensor electrodes is smaller than a reference resistance, up to a first temperature so that PM deposited on the element can be heated and removed therefrom. When the internal combustion engine starts, the element is heated, upon detecting that the engine is about to start, up to a second temperature lower than the first temperature so that the deposit on the surface of the element can be heated and removed therefrom. Then, after the internal combustion engine has started and the deposit has been heated and removed from the surface of the element, the amount of fine particles in exhaust gas from the internal combustion engine is detected.

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, it is suitable as a control device for an internal combustion engine that is installed in the exhaust path of the internal combustion engine and has a particulate detection sensor for detecting the amount of particulates in the exhaust gas.

  For example, Patent Document 1 discloses a sensor that detects the amount of particulate matter (hereinafter also referred to as “PM”) in the exhaust gas of an internal combustion engine. The sensor of Patent Document 1 includes an insulating layer to which PM is attached and a pair of electrodes arranged on the insulating layer at a distance from each other. When this sensor is in contact with the exhaust gas and PM in the exhaust gas is deposited between the electrodes, the conductivity between the electrodes changes in accordance with the amount of PM deposited, so the resistance between the electrodes changes. Therefore, by detecting the resistance between the electrodes of the sensor, the amount of PM deposited between the electrodes is detected, whereby the amount of PM in the exhaust gas is estimated.

  In this sensor, when the PM deposition amount between the electrodes exceeds a certain amount, the resistance value between the electrodes no longer changes, and thereafter, the output value corresponding to the PM deposition amount cannot be output. On the other hand, in the technique of Patent Document 1, when the amount of PM deposition between the electrodes increases, the sensor is heated for a predetermined time by a heater built in the sensor, and PM reset is performed to burn and remove the accumulated PM.

JP 2009-1444577 A

  The PM reset that removes the PM accumulated on the sensor as described above by combustion may take a long time. During the PM reset, the sensor cannot be used for normal PM amount detection, and the measurement of the PM amount is stopped. Further, it is known that the PM reset process is performed at the start timing of the internal combustion engine. In this case, the PM reset is performed after moisture in the exhaust pipe is discharged. For this reason, after starting the internal combustion engine, it takes a considerable time to enter the PM amount detection mode. Furthermore, for example, after a low temperature start, when the short trip operation that stops before the water temperature has risen is repeated, a situation may occur in which the sensor does not enter the detection mode.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an improved control device for an internal combustion engine that shortens the period during which the amount of PM cannot be measured due to PM reset.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
When the internal combustion engine is stopped, if the resistance between the electrodes of the particulate detection sensor is smaller than the reference resistance, the element portion of the particulate detection sensor is heated to the first temperature and deposited on the element portion. Fine particle removing means for burning and removing fine particles;
Start prediction means for predicting start of the internal combustion engine;
When the start of the internal combustion engine is predicted, the element portion is heated to a second temperature lower than the first temperature, and the deposit removal means for burning and removing deposits on the surface of the element portion;
Fine particle amount detection means for starting detection of the amount of fine particles in the exhaust gas of the internal combustion engine after the internal combustion engine is started and the deposits on the surface of the element portion are burned and removed;
Is provided.

According to a second invention, in the first invention,
Heating means for heating the element portion to a third temperature lower than the second temperature and higher than 100 ° C. after the deposit on the surface of the element portion is burned and removed by the deposit removing means;
Exhaust gas temperature determining means for determining whether or not the exhaust gas temperature of the internal combustion engine is higher than 100 ° C.,
The particulate matter detection means starts detecting particulate matter in the exhaust gas only when the temperature of the exhaust gas is found to be higher than 100 ° C.

According to a third invention, in the first or second invention,
Output detection means for detecting the output of the particulate detection sensor when the internal combustion engine is stopped after the combustion removal of the particulates by the particulate removal means;
Correction means for correcting the zero point of the particle detection sensor in accordance with the output detected by the output detection means;
Is further provided.

  According to the first invention, when fine particles are accumulated in the element portion of the fine particle detection sensor, a process (PM reset) for removing the combustion when the internal combustion engine is stopped is performed. Further, at the stage when the start prediction of the internal combustion engine is detected, a process of burning the deposits adhering to the element portion is performed. Therefore, the particulate matter amount in the exhaust gas can be detected by the particulate detection sensor at an early stage when the internal combustion engine is started.

  According to the second invention, when the internal combustion engine is started, the temperature of the element portion is set to 100 ° C. until the temperature of the exhaust gas becomes higher than 100 ° C. after the treatment for removing the deposits on the element portion is performed. maintain. As a result, the influence of moisture on the electrodes in the exhaust pipe of the internal combustion engine can be suppressed, and detection of the amount of fine particles can be started immediately when the exhaust gas becomes higher than 100 ° C.

  According to the third aspect of the invention, the zero point of the particulate detection sensor can be corrected based on the sensor output after the particulate combustion removal process. Thereby, it is possible to suppress the influence of the output deviation due to the aging of the sensor or the like and detect the amount of fine particles more accurately.

It is a schematic diagram for demonstrating the PM sensor in embodiment of this invention. It is a schematic diagram for demonstrating the PM sensor in embodiment of this invention. It is a figure for demonstrating the state at the time of PM amount detection of PM sensor in embodiment of this invention. It is a figure for demonstrating the relationship between PM deposition amount and the output of PM sensor in embodiment of this invention. It is a timing chart for demonstrating control of PM reset in embodiment of this invention. It is a figure for demonstrating control of the conventional PM reset. It is a flowchart for demonstrating the routine of control which a control apparatus performs in embodiment of this invention. It is a flowchart for demonstrating the routine of control which a control apparatus performs in embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
1 and 2 are schematic views for explaining a PM sensor (particle detection sensor) according to an embodiment of the present invention. FIG. 1 is an overall view of the PM sensor, and FIG. 2 is a part of a sensor element portion. FIG. A PM sensor 2 shown in FIG. 1 is installed, for example, in an exhaust path of an internal combustion engine mounted on a vehicle, and is used for detecting PM (particulate matter) in exhaust gas.

  As shown in FIG. 1, the PM sensor 2 includes a cover 4 and an element portion 6 installed in a space in the cover 4. The cover 4 has a plurality of holes through which gas passes. When the PM sensor 2 is used, the cover 4 is installed in the exhaust passage of the internal combustion engine, exhaust gas flows into the cover 4 from a plurality of holes in the cover 4, and the element portion 6 is in contact with the exhaust gas.

  As shown in FIG. 2, the element portion 6 has a pair of electrodes 8 and 10 on the surface thereof. The pair of electrodes 8 and 10 are arranged at a predetermined interval without being in contact with each other. Furthermore, each of the electrodes 8 and 10 has a portion formed in a comb-teeth shape, and is arranged so as to be engaged with each other in this portion. The electrodes 8 and 10 are in contact with the insulating layer 12 formed in the lower layer. The insulating layer 12 has a function of depositing PM. A heater (removal means) (not shown) is embedded in the lower layer of the electrodes 8 and 10 inside the insulating layer 12.

  The electrode 8 and the electrode 10 are each connected to a power source (not shown) via a power circuit or the like. Thereby, a predetermined voltage can be applied between the electrode 8 and the electrode 10. The heater is connected to a power source (not shown) via a power circuit or the like, and the element unit 6 including the electrodes 8 and 10 is heated by supplying predetermined power to the heater.

  The above-described detector, power supply circuit, and the like are connected to a control device (not shown). The control executed by the control device includes, for example, detection of the PM amount in the exhaust gas and temperature control of the element unit 6. Specifically, the control device performs control so that a predetermined voltage for PM amount detection (hereinafter referred to as “PM amount detection voltage”) is applied between the electrodes 8 and 10, and the output (current value) at this time Is detected via a detector (not shown), and the amount of PM in the exhaust gas is detected according to the resistance value between the corresponding electrodes 8 and 10. Further, the control device controls the temperature of the element unit 6 by controlling the power supplied to the heater.

  The control executed by the control device in the present embodiment further includes a PM reset for burning and removing PM accumulated in the element section 6 of the PM sensor 2 and a PM amount detected by the PM sensor 2 after starting the internal combustion engine. Start control until the PM detection mode is set.

  FIG. 3 is a diagram for explaining the PM deposition state on the element unit 6. Specifically, immediately after the PM reset (or in the initial state of the sensor) in which the PM between the electrodes 8 and 10 is almost completely removed, as shown on the left side of the drawing in FIG. It will be in the state which has not accumulated. On the other hand, when the PM sensor 2 comes into contact with the exhaust gas, PM gradually accumulates between the electrodes 8 and 10. As shown in the right side of the drawing in FIG. 3 due to the deposited PM, conduction between the electrodes 8 and 10 is further increased, and further, as the amount of PM deposition increases, the number of conduction points between the electrodes 8 and 10 increases.

  FIG. 4 is a graph for explaining the relationship between the PM deposition amount between the electrodes 8 and 10 and the sensor output. The horizontal axis represents the PM deposition amount, and the vertical axis represents the sensor output. As described above, immediately after PM reset, in a state where PM is hardly adhered between the electrodes 8 and 10, the electrodes 8 and 10 are not conductive. Therefore, even if a PM amount detection voltage is applied between the electrodes 8 and 10 immediately after the PM reset, the output (current value) of the PM sensor 2 becomes a value near zero. Thereafter, even if the PM deposition amount slightly increases, the output of the PM sensor 2 becomes a value close to 0 in the period (A) in which the electrodes 8 and 10 are insulated from each other. Shows little change. Hereinafter, this period (A) is referred to as a “sensor dead zone”.

  Gradually, when the amount of deposited PM increases and the electrodes 8 and 10 are electrically connected by PM, thereafter, the resistance between the electrodes 8 and 10 decreases as the amount of deposited PM increases. Therefore, the sensor output starts to change according to the amount of PM deposited between the electrodes 8 and 10. In this state, the control device detects the current when the PM amount detection voltage is applied between the electrodes 8 and 10 as a sensor output, and the resistance value between the electrodes 8 and 10 corresponding thereto detects the current in the exhaust gas. The amount of PM can be estimated.

  By the way, when the PM amount is continuously detected and the PM accumulated on the electrodes 8 and 10 of the PM sensor 2 is saturated, the PM sensor 2 can no longer output any more, and the PM amount is correctly measured. It becomes a state that can not be. In order to avoid such a situation, a PM reset for burning and removing PM is generally performed at the start of the internal combustion engine. However, the PM reset at the start requires a considerable time. However, it is desirable that the PM detection mode can be shifted to an earlier stage after the internal combustion engine is started.

  Therefore, in the first embodiment, the control device avoids the PM accumulated between the electrodes 8 and 10 from being saturated, and can start measuring the PM amount at an early stage after the internal combustion engine is started. Therefore, PM reset and start control described later are performed.

  FIG. 5 is a timing chart for illustrating control in the present embodiment of the present invention. In FIG. 5, the horizontal axis indicates time, the vertical axis indicates temperature, (a) indicates element temperature, and (b) indicates exhaust gas temperature.

  In this control, first, when the sensor output at time T1 when the internal combustion engine is stopped is not 0, it is determined that PM is accumulated between the electrodes 8 and 10. In this case, PM reset is immediately executed. Specifically, the temperature of the element unit 6 (element temperature) is raised to about 800 ° C. (first temperature) and heated for a predetermined PM reset time (period (A) in FIG. 5). The Thereby, the PM deposited on the element portion 6 is removed by combustion. Note that the PM reset time (A) is a sufficient and optimum time for burning the PM deposited in advance, and is obtained in advance through experiments or the like and stored in the control device.

  The PM reset is completed at time T2 after the PM reset time (A) has elapsed. In this state, ideally, no PM is deposited on the element portion 6 and the sensor output is zero.

  Thereafter, the start control of the PM sensor 2 is executed at time T3 when the start prediction of the internal combustion engine is detected. That is, at time T3, the temperature of the element unit 6 is controlled so that the temperature becomes about 300 ° C. (second temperature), and the element unit 6 is heated for a predetermined adhering matter removal time (period (B) in FIG. 5). The As a result, deposits on the surface of the element portion 6, such as oil and fuel components, are removed by combustion. The deposit removal time (B) is a sufficient and optimum time for burning the deposit on the element unit 6 and is obtained in advance by experiments and stored in the control device. Further, the detection of the start prediction is determined based on whether or not a state satisfying a predetermined condition is detected, such as a signal when an ACC (accessory power supply) is turned on or a door opening / closing signal of the vehicle.

  When the start of the internal combustion engine is detected at time T4 after the completion of combustion removal of the deposit, the element temperature is controlled to about 100 ° C. (third temperature). Thereby, dew condensation on the electrodes 8 and 10 of the element part 6 is prevented. Furthermore, when the temperature (b) of the exhaust gas becomes higher than 100 ° C. at time T5, it is considered that there is no influence of condensation on the element portion 6. At this time, PM can be attached to the element portion 6 by thermophoresis. Therefore, at time T5 when the exhaust gas becomes higher than 100 ° C., the energization to the heater is stopped and the PM amount detection voltage is applied between the electrodes 8 and 10 to start detection of the PM amount.

  FIG. 6 is a diagram for explaining time and sensor output when a conventional PM reset is executed when the internal combustion engine is started. In FIG. 6, the horizontal axis represents time, and the vertical axis represents sensor output. For reference, an example of a change in vehicle speed corresponding to the time is shown below the time axis.

  At time T5 shown in FIG. 6, the PM reset processing of the present embodiment is completed and the PM detection mode is set. On the other hand, in the case of the conventional PM reset, first, after the start of the internal combustion engine, in order to avoid the influence of the moisture in the exhaust pipe, a moisture-proof period is taken until time T6 when it is estimated that the moisture in the exhaust pipe is exhausted. .

  At time T6 after the disappearance of moisture in the exhaust pipe, PM reset is started. That is, the sensor element temperature is maintained at a temperature of about 800 ° C. and maintained for a preset PM reset time.

  By PM reset, PM deposited on the element unit 6 is almost completely removed. Therefore, the “sensor dead zone” is set between time T7 and time T8 after the PM reset time has elapsed. That is, in this state, even if the PM amount detection voltage is applied, a sensor output corresponding to the PM amount in the exhaust gas cannot be obtained. In the conventional PM reset process, the PM amount can be detected only at time T8 when a certain amount of PM is accumulated between the electrodes and is no longer the “sensor dead zone”.

  As described above, in the conventional processing, after the PM reset is started, it takes a considerable time until the PM amount detection can be started. On the other hand, the PM reset and the internal combustion engine when the internal combustion engine is stopped as in the present embodiment. By performing the start control after the start prediction, it is possible to shift to the PM detection mode at an early stage after the start of the internal combustion engine.

  7 and 8 are flowcharts for illustrating a control routine executed by the control device in the embodiment of the present invention. In the routine of FIG. 7, when the stop of the internal combustion engine is recognized in step S2, the output of the PM sensor 2 at the time of stop is detected and recorded (S4). The sensor output at the time of stop is an output obtained by applying a PM amount detection voltage to the PM sensor when the internal combustion engine is stopped.

  Next, it is determined whether or not the current output of the PM sensor 2 is greater than 0 (S6). In step S <b> 2, when the output of the PM sensor 2> 0 is not established, it is estimated that PM is not deposited between the electrodes 8 and 10 of the PM sensor 2. Therefore, in this case, the PM reset is not performed when the internal combustion engine is stopped this time, and this routine ends.

  On the other hand, if the establishment of output> 0 is recognized in step S 6, it is recognized that PM is deposited between the electrodes 8 and 10. In this case, PM reset is executed (S8). Here, predetermined electric power is supplied to the heater, and the element part 6 is heated to about 800 ° C. This state is continued for a PM reset time stored in advance in the control device.

  When the PM reset in step S8 is completed, the current output and temperature of the PM sensor 2 are detected and recorded (S10). The sensor element temperature can be detected by, for example, detecting the impedance when a predetermined AC voltage is applied between the electrodes 8 and 10 and obtaining the relationship from the relationship between the impedance and the sensor element temperature, or the heater resistance. Is obtained from the relationship between the heater resistance and the sensor element temperature. Thereafter, the processing at the time of the current stop ends.

  In the routine of FIG. 8, first, a start prediction of the internal combustion engine is detected (S102). Here, the start prediction of the internal combustion engine is detected by satisfying any of the predetermined start prediction conditions such as, for example, whether the operation of the ACC or the opening / closing of the door of the vehicle is detected.

  If the detection of the start prediction is recognized in step S102, then a deposit removal process is performed (S104). In the deposit removal process, the element unit 6 is heated to a temperature of about 300 ° C. by supplying predetermined power to the heater. This state is continued for the deposit removal time previously stored in the control device. Thereby, the oil component etc. which adhered to the surface of the element part 6 are removed by combustion.

  Next, it is determined whether or not the sensor output at the previous stop of the internal combustion engine was greater than 0 (S106). Here, the sensor output at the time of stopping is detected by the process of step S4 or S10 in FIG. 7 and recorded in the control device.

  If it is determined in step S106 that the sensor output at stop> 0 is established, then zero point correction is executed (S108). The zero point correction is to correct a deviation of the sensor output that occurs even after the PM reset, and the zero point of the sensor output is corrected by a correction value that is obtained according to the sensor output at the time of stop.

  In step S106, it is determined whether or not establishment of the sensor output at stop> 0 is recognized, or after the zero point correction of the sensor output is performed in step S108, the internal combustion engine is started. S110). If the start of the internal combustion engine is not permitted, the determination in step S110 is repeated at regular intervals until the start is permitted.

  On the other hand, if the start of the internal combustion engine is recognized in step S108, then the temperature of the element unit 6 is maintained at 100 ° C. (S112). Specifically, energization to the heater is controlled, and the element unit 6 is heated and maintained at 100 ° C.

  Next, it is determined whether or not the temperature of the exhaust gas has become higher than 100 ° C. (S114). Specifically, the current temperature of the exhaust gas is detected according to the output of the exhaust gas temperature sensor installed in the exhaust pipe of the internal combustion engine, and it is determined whether or not the detected temperature is higher than 100 ° C.

  If the establishment of the exhaust gas temperature> 100 ° C. is not recognized, the sensor element is maintained at about 100 ° C. until the establishment of the exhaust gas temperature> 100 ° C. is recognized (S112). Success / failure determination of temperature> 100 ° C. is repeated at regular intervals.

  On the other hand, if the establishment of the exhaust gas temperature> 100 ° C. is recognized in step S114, then the start of detection of the PM amount by the sensor is permitted (S116). Here, a PM amount detection voltage is applied between the electrodes 8 and 10 of the PM sensor 2, and the PM amount is detected based on a resistance value obtained according to the output at this time.

  As described above, in the present embodiment, PM reset is performed when the output of the PM sensor 2 is not 0 when the internal combustion engine is stopped. Further, at the time when the start of the internal combustion engine is predicted, a process of removing deposits such as oil components adhering to the surface of the element portion 6 is performed. After the start-up, until the exhaust gas reaches 100 ° C., the influence of moisture in the exhaust pipe is suppressed by maintaining the element portion 6 at 100 ° C. By this control, the detection of the PM amount can be started when the exhaust gas of the internal combustion engine becomes higher than 100 ° C., and the PM detection mode can be shifted to an earlier stage when the internal combustion engine is started.

  In this embodiment, the “particulate removal unit” of the present invention is realized by executing the process of step S8, and the “starting prediction unit” is realized by executing the process of step S102. By executing the process of step S104, an “adherent removal means” is realized, and by executing the process of step S116, a “fine particle amount detection means” is realized, and the process of step S112 is executed. The “heating means” is realized, the “exhaust gas temperature determining means” is realized by executing the processing of step S114, the “output detecting means” is realized by executing step S4 or S10, and step S108. [Correction means] is realized by executing the above process.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, when the sensor output is larger than 0 when the internal combustion engine is stopped, PM reset is performed. However, PM reset may be performed only when the sensor output is larger than a predetermined reference value.

  In the present embodiment, the case where a current value is detected when a predetermined PM amount detection voltage is applied as the sensor output has been described. However, the PM sensor 2 is not limited to the one that outputs a current value. Any value that outputs a value having a correlation with the resistance between 10 may be used.

  Further, in the present embodiment, in the start-up control, a case where both the process for removing the deposits on the surface of the element unit 6 and the process for maintaining the element unit 6 at 100 ° C. until the exhaust gas reaches 100 ° C. will be described. did. However, the present invention is not limited to this, and only the deposit removal processing on the surface of the element portion may be performed.

  In the present embodiment, the case where the zero point of the PM sensor 2 is corrected based on the sensor output at the time of stop in the start control has been described. However, the present invention is not limited to such a zero point correction. In the present embodiment, the correction value is obtained according to the sensor output at the time of stop and the zero point is corrected. However, in the present invention, the zero point correction method is not limited to this. For example, the sensor output at the time of stop may be set as the zero point as it is. Further, the zero point correction is not limited to the one that performs the zero point correction at the time of starting, and for example, the zero point correction may be performed at the timing of detecting the sensor output when the internal combustion engine is stopped.

  Further, in the above embodiment, when the number of each element, number, quantity, range, etc. is mentioned, it is mentioned unless otherwise specified or clearly specified in principle. The invention is not limited to the numbers. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 PM sensor 6 Element part 8, 10 Electrode

Claims (3)

When the internal combustion engine is stopped, if the resistance between the electrodes of the particulate detection sensor is smaller than the reference resistance, the element portion of the particulate detection sensor is heated to the first temperature and deposited on the element portion. Fine particle removing means for burning and removing fine particles;
Start prediction means for predicting start of the internal combustion engine;
When the start of the internal combustion engine is predicted, the element portion is heated to a second temperature lower than the first temperature, and the deposit removal means for burning and removing deposits on the surface of the element portion;
Fine particle amount detection means for starting detection of the amount of fine particles in the exhaust gas of the internal combustion engine after the internal combustion engine is started and the deposits on the surface of the element portion are burned and removed;
A control device for an internal combustion engine, comprising: Heating means for heating the element portion to a third temperature lower than the second temperature and higher than 100 ° C. after the deposit on the surface of the element portion is burned and removed by the deposit removing means;
Exhaust gas temperature determining means for determining whether or not the exhaust gas temperature of the internal combustion engine is higher than 100 ° C.,
2. The internal combustion engine according to claim 1, wherein the fine particle amount detection means starts detection of the fine particle amount in the exhaust gas only when it is recognized that the temperature of the exhaust gas is higher than 100 ° C. 3. Engine control device. Output detection means for detecting the output of the particulate detection sensor when the internal combustion engine is stopped after the combustion removal of the particulates by the particulate removal means;
Correction means for correcting the zero point of the particle detection sensor in accordance with the output detected by the output detection means;
The control apparatus for an internal combustion engine according to claim 1, further comprising:

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