JP6468202B2 - Control system for electrically heated catalyst - Google Patents

Description

  The present invention relates to a control system for an electrically heated catalyst provided in an exhaust passage of an internal combustion engine.

  2. Description of the Related Art Conventionally, as an exhaust purification device provided in an exhaust passage of an internal combustion engine, an electrically heated catalyst (hereinafter also referred to as EHC) in which a catalyst is heated by a heating element that generates heat when energized has been developed. Has been.

  In EHC, in order to adjust the temperature of the heating element to a desired temperature, the power supply to the heating element is controlled. Therefore, a configuration is known in which exhaust temperature sensors are provided in the exhaust passages upstream and downstream of the heating element in order to obtain the temperature of the EHC heating element. In such a configuration, the temperature of the heating element is estimated based on the detection value of the exhaust temperature sensor. Then, power supply to the heating element is controlled based on the estimated temperature of the heating element (see, for example, Patent Document 1).

Japanese Patent No. 5626368 JP 2000-206070 A JP-A-8-304313 JP 2001-249092 A JP 2013-185573 A

  In the case where an exhaust temperature sensor is provided in the exhaust passage to acquire the temperature of the EHC heating element, even if an exhaust temperature sensor is disposed in the vicinity of the heating element in the exhaust passage, the exhaust temperature sensor and the heating element A certain distance occurs between the two. Further, when the catalyst is heated by energizing the heating element, the exhaust gas may not flow through the exhaust passage. In this case, it is difficult to transfer the heat generated in the heating element to the exhaust temperature sensor via the exhaust. Therefore, it may be difficult to estimate the temperature of the EHC heating element with high accuracy based on the detection value of the exhaust temperature sensor. Therefore, if the power supply to the heating element is controlled based on the detection value of the exhaust temperature sensor, there is a risk of causing an excessive supply or insufficient supply of power.

  The present invention has been made in view of the above problems, and an object of the present invention is to more suitably control power supply to a heating element in EHC.

  An electric heating catalyst control system according to the present invention is an electric heating catalyst control system provided in an exhaust passage of an internal combustion engine, and the electric heating catalyst generates heat when energized and generates heat by generating heat. A heating element that heats, a case that houses the heating element, and a mat member that is sandwiched between the heating element and the case to insulate electricity, and between the case and the mat member or the A load sensor that is provided in the mat member and detects a load applied to the mat member, and a control unit that controls power supply to the heating element based on a detection value of the load sensor.

In the present invention, a load sensor is provided between the case and the mat member or in the mat member in the EHC. Here, when the heating element of the EHC generates heat by energization, the heating element expands as the temperature rises. As a result, the load applied to the load sensor provided in the EHC increases. That is, the detection value of the load sensor has a correlation with the temperature of the heating element. Therefore, by controlling the power supply to the heating element based on the detection value of the load sensor, the temperature of the heating element can be adjusted to a desired temperature.

  The load sensor according to the present invention is provided between the case and the mat member or in the mat member. Therefore, the load sensor can directly detect a volume change accompanying a temperature change of the heating element as a change in the load applied to the load sensor. Therefore, the change in the load detected by the load sensor has higher followability to the change in the temperature of the heating element than the change in the exhaust temperature detected by the exhaust temperature sensor provided in the exhaust passage downstream of the heating element. . Further, even when exhaust does not flow through the exhaust passage, the load detected by the load sensor has a high correlation with the temperature of the heating element.

  In addition, electrical insulation between the heating element and the load sensor is ensured by the mat member. Here, in order to detect the temperature of a heat generating body, the structure which provides a temperature sensor in the position similar to the installation position of the load sensor which concerns on this invention can be considered. However, in such a configuration, since the mat member functions as a heat insulating material, there is a possibility that the correlation between the detection value of the temperature sensor and the temperature of the heating element is lowered. Therefore, rather than the correlation between the detection value of the load sensor according to the present invention and the temperature of the heating element, the detection value of the temperature sensor and the heating element when the temperature sensor is installed at the same position as the installation position of the load sensor. Correlation with temperature is low.

  As described above, in EHC, the power supply to the heating element is controlled more appropriately by controlling the power supply to the heating element based on the detection value of the load sensor showing a high correlation with the temperature of the heating element. can do.

  In the present invention, the control unit stops power supply to the heating element when the detection value of the load sensor reaches a target value corresponding to a predetermined target load after starting the power supply to the heating element. Also good. Here, the target load is a value set as a load that is assumed to be applied to the load sensor when the temperature of the heating element reaches a desired temperature. In addition, a target value that is a detection value of the load sensor corresponding to such a target load can be determined in advance based on experiments or the like. Then, by controlling the power supply to the heating element as described above, it is possible to suppress an excessive supply or insufficient supply of power to the heating element. As a result, the temperature of the heating element can be adjusted to a desired temperature with higher accuracy.

  In addition, the control unit may control the amount of power supplied during execution of power supply to the heating element based on the detection value of the load sensor. Here, while the power supply to the heating element is being executed, the load to be detected by the load sensor while the detection value of the load sensor is moving toward the target value is set as a reference load. This reference load can be determined in advance based on experiments or the like. When the deviation of the actual detection value of the load sensor with respect to the reference load becomes larger than a predetermined level during the power supply to the heating element, the control unit corrects the power supplied to the heating element. Also good. That is, when the actual detection value of the load sensor deviates more than a predetermined level with respect to the reference load, the power supplied to the heating element may be reduced. Further, when the actual detection value of the load sensor is deviated from a predetermined level with respect to the reference load, the power supplied to the heating element may be increased.

According to this, while the power supply to the heating element is being executed, the power supplied to the heating element is such that the load actually applied to the load sensor changes as much as possible along the transition of the reference load. Will be controlled. Therefore, the load applied to the load sensor can reach the target load more quickly while suppressing excessive power supply to the heating element. Therefore, the temperature of the heating element can be raised to a desired temperature more quickly while suppressing the promotion of thermal deterioration of the heating element.

  In the EHC, a pair of electrodes for supplying power to the heating element is provided. Here, a pair of electrodes may be connected to the outer peripheral surface in contact with the mat member of the heating element in the EHC. In this case, each electrode (that is, the positive electrode and the negative electrode) in the pair of electrodes may extend in the circumferential direction and the axial direction along the outer peripheral surface of the heating element, and may be opposed to each other with the heating element interposed therebetween.

  Here, when the EHC heating element is energized, in the heating element, the temperature in the vicinity of each of the pair of electrodes becomes the highest. Then, the temperature at the position farthest from the respective electrodes of the pair of electrodes on the outer peripheral surface of the heating element, that is, the temperature near the intermediate position between the pair of electrodes in the circumferential direction of the heating element becomes the lowest. Therefore, in the present invention, the load sensor may be disposed between the case and the mat member or in the mat member at an intermediate position between the pair of electrodes in the circumferential direction of the heating element. By executing or stopping the power supply to the heating element based on the detection value of the load sensor arranged at such a position, the temperature of the lowest temperature portion of the heating element can be adjusted to a desired temperature. . Therefore, it is possible to sufficiently raise the temperature of the entire heating element with a higher probability.

  The control system for an electrically heated catalyst according to the present invention may include a plurality of load sensors provided between the case and the mat member in the EHC or in the mat member. At this time, the load sensor may be disposed at a position relatively close to one electrode and a position relatively far from the one electrode in the pair of electrodes that supply power to the heating element.

  Here, local oxidation may occur in the electrode that supplies power to the heating element. When such local oxidation of the electrode occurs, the resistance value of the oxidized portion in the electrode increases. For this reason, if the electrode continues to be supplied with power similar to that in a normal state in a state where local oxidation of the electrode has occurred, the temperature of the electrode excessively increases and the electrode is damaged or There is a risk of melting.

  Here, as described above, in the configuration in which the load sensors are arranged at positions relatively close to one electrode of the pair of electrodes and positions relatively distant from the one electrode, the one electrode When local oxidation occurs in FIG. 2, a load difference, which is a difference between detection values of these two load sensors, becomes larger than when the one electrode is in a normal state. Therefore, in the configuration in which the load sensor is arranged as described above, when the load difference becomes larger than the first predetermined amount during the power supply to the heating element, the control unit supplies the heating element to the heating element. Power to be reduced may be reduced. According to this, when the load difference becomes larger than a predetermined amount as a result of local oxidation of the electrode, the power supplied to the heating element is reduced. Therefore, heating of the catalyst can be continued while suppressing the electrode from being broken or melted.

  In addition, when the power supply to the heating element is executed, the load difference becomes larger than the first predetermined amount, and when the power supplied to the heating element is reduced, the control unit tends to maintain or decrease the load difference. The electric power supplied to the heating element may be gradually reduced until it becomes a trend. Then, after the time when the load difference becomes a maintenance tendency or a reduction tendency, the supply power at that time may be maintained and the power supply to the heating element may be executed. According to this, the reduction amount of the electric power supplied to a heat generating body can be reduced as much as possible, suppressing that an electrode breaks or melts down. Therefore, it is possible to raise the temperature of the heating element as quickly as possible while suppressing breakage or melting of the electrode.

In the configuration in which the load sensor is disposed at a position relatively close to one electrode of the pair of electrodes and a position relatively distant from the one electrode, the power supply to the heating element is being performed. When the load difference becomes larger than the second predetermined amount, the control unit may stop the power supply to the heating element. According to this, when local difference of the electrode occurs and the load difference becomes larger than a predetermined amount as compared with the normal state of the electrode, the power supply to the heating element is stopped. Therefore, it can suppress that an electrode breaks or melts down.

The present invention can more suitably control power supply to a heating element in EHC.

It is a figure which shows schematic structure of the exhaust gas purification apparatus which has EHC based on Example 1 of this invention. It is a figure which shows schematic structure of EHC which concerns on Example 1 of this invention. It is a figure which shows the shape of the mat member before it winds around the EHC carrier based on Example 1 of this invention. It is a figure which shows transition of the temperature of an EHC carrier and the load concerning a load sensor when electricity supply to the EHC carrier is performed based on Example 1 of this invention. It is a flowchart which shows the flow of the electricity supply control of EHC which concerns on Example 1 of this invention. It is a figure which shows the structure at the time of providing the load sensor based on Example 1 of this invention in the mat member. It is a flowchart which shows the flow of the electricity supply control of EHC which concerns on Example 2 of this invention. It is a figure which shows transition of the electric power supplied to the EHC carrier and the detected value of a load sensor based on Example 2 of this invention. It is a figure which shows schematic structure of EHC which concerns on Example 3 of this invention. It is a part of flowchart which shows the flow of the electricity supply control of EHC which concerns on Example 3 of this invention. It is another one part of the flowchart which shows the flow of the electricity supply control of EHC which concerns on Example 3 of this invention. It is a figure which shows the map used in order to calculate guard electric power based on Example 3 of this invention. It is a flowchart which shows the flow of the electricity supply control of EHC which concerns on the modification of Example 3 of this invention.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Example 1>
(Outline configuration)
A schematic configuration of an exhaust gas purification apparatus having an EHC according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating a schematic configuration of an exhaust emission control apparatus according to the present embodiment. FIG. 2 is a diagram illustrating a schematic configuration of the EHC according to the present embodiment. FIG. 2 shows a cross section in a direction perpendicular to the direction in which the EHC exhaust gas flows according to this embodiment (the direction indicated by the arrow in FIG. 1). An exhaust emission control device 1 according to this embodiment is provided in an exhaust pipe 2 of an internal combustion engine constituting a hybrid system having an internal combustion engine and an electric motor as a drive source for a vehicle. However, the internal combustion engine to which the EHC according to the present invention is applied is not necessarily limited to the internal combustion engine constituting the hybrid system.

  The exhaust purification device 1 includes an EHC 3 and a rear catalyst 4. The EHC 3 includes a case 5, an EHC carrier 31, a mat member 32, and electrodes 33a and 33b. The EHC carrier 31 is accommodated in the case 5. The EHC carrier 31 is formed in a cylindrical shape, and is installed so that its central axis is coaxial with the central axis A of the exhaust pipe 2. The central axis A is a central axis common to the exhaust pipe 2, the EHC carrier 31, and the case 5. A three-way catalyst 31 a is supported on the EHC carrier 31. The catalyst supported on the EHC carrier 31 is not limited to the three-way catalyst, and may be an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst.

  The EHC carrier 31 is formed of a material that generates electric resistance when energized. In this embodiment, the EHC carrier 31 corresponds to a heating element according to the present invention. Examples of the material of the EHC carrier 31 include SiC. The EHC carrier 31 has a plurality of passages extending in the direction in which the exhaust flows (that is, the direction in which the central axis A extends) and having a cross section in a direction perpendicular to the direction in which the exhaust flows. And exhaust gas distribute | circulates through this channel | path. The cross-sectional shape of the EHC carrier 31 in the direction orthogonal to the central axis A may be an ellipse or the like.

  A pair of electrodes 33 a and 33 b are connected to the side surface (outer peripheral surface) of the EHC carrier 31. The electrodes 33a and 33b extend in the circumferential direction and the axial direction along the outer peripheral surface of the EHC carrier 31, respectively. The electrode 33a and the electrode 33b face each other with the EHC carrier 31 in between. However, the entire surfaces of the electrode 33a and the electrode 33b are not necessarily opposed to each other. A metal foil 6 is connected to the electrodes 33a and 33b. The metal foil 6 protrudes outside the case 5 through a through hole 32 a formed in the mat member 32 described later and a through hole 5 a formed in the case 5. However, the through hole 5 a of the case 5 is surrounded by the electrode cover 7. Therefore, the metal foil 6 protrudes into the electrode cover 7. A power cable (not shown) is inserted through the electrode cover 7 in a sealed state. The metal foil 6 is connected to the power cable in the electrode cover 7. When the EHC carrier 31 is energized, a current flows from the battery to the electrodes 33 a and 33 b through the power cable and the metal foil 6.

  In the EHC 3, when the EHC carrier 31 generates heat by energization, the three-way catalyst 31a supported on the EHC carrier 31 is heated. Thereby, activation of the three-way catalyst 31a is promoted. In the present embodiment, power supply to the EHC carrier 31 is controlled by an electronic control unit (ECU) 20 provided in the internal combustion engine. That is, the ECU 20 switches ON / OFF of energization to the EHC carrier 31 and adjusts the power supplied to the EHC carrier 31.

  Case 5 is made of metal. As a material for forming the case 5, a stainless steel material can be exemplified. The inner wall surface of the case 5 is coated with glass which is an electrical insulating material. A mat member 32 is sandwiched between the inner wall surface of the case 5 and the outer peripheral surface of the EHC carrier 31. That is, the EHC carrier 31 is supported by the mat member 32 in the case 5.

The mat member 32 is formed of an electrical insulating material. As a material for forming the mat member 32, a ceramic fiber mainly composed of alumina can be exemplified. The mat member 32 is wound around the outer peripheral surface of the EHC carrier 31. FIG. 3 is a view showing the shape of the mat member 32 before being wound around the EHC carrier 31. The vertical direction in FIG. 3 is the axial direction of the EHC carrier 31 when the mat member 32 is wound around the EHC carrier 31. As shown in FIG. 3, the mat member 32 has a through hole 32a through which the metal foil 6 passes when the EHC 3 is assembled as described above. Further, a convex portion 32 b is formed at one end of the mat member 32, and a concave portion 32 c is formed at the other end of the mat member 32. Then, when the mat member 32 is wound around the EHC carrier 31, the convex portion 32b and the concave portion 32c are combined. Since the mat member 32 is sandwiched between the EHC carrier 31 and the case 5, it is possible to suppress a current from flowing to the case 5 when the EHC carrier 31 is energized. That is, the mat member 32 has not only a function of supporting the EHC carrier 31 in the case 5 but also a function of electrically insulating the case 5 and the EHC carrier 31.

  Further, in this embodiment, as shown in FIG. 2, at the intermediate position between the pair of electrodes 33a and 33b in the circumferential direction of the EHC carrier 31 (that is, the position where La = Lb in FIG. 2), The load sensor 10 is provided between the mat member 32. That is, the load sensor 10 is sandwiched between the inner wall surface of the case 5 and the outer wall surface of the mat member 32 at a position farthest from each of the electrode 33a and the electrode 33b. The load sensor 10 is a sensor that detects a load applied to itself. As the load sensor 10, a load cell or a strain gauge can be employed. The load sensor 10 is electrically connected to the ECU 20. Then, the detected value of the load sensor 10 is input to the ECU 20.

  Further, the rear catalyst 4 is also accommodated in the case 5. The rear stage catalyst 4 is disposed downstream of the EHC carrier 31 in the case 5. A three-way catalyst 41 a is supported on the catalyst carrier 41 of the rear stage catalyst 4. The catalyst supported on the catalyst carrier 41 of the rear catalyst 4 is not limited to the three-way catalyst, and may be an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst. A mat member 42 formed of the same material as that of the mat member 32 is sandwiched between the catalyst carrier 41 of the rear catalyst 4 and the case 5. Thereby, the catalyst carrier 41 is supported by the mat member 32 in the case 5.

  As described above, the exhaust gas purification apparatus 1 according to the present embodiment employs a configuration in which the rear catalyst 4 is accommodated in the case 5, but in the EHC according to the present invention, the rear catalyst is installed in the case. That is not essential.

(Energization control)
Next, energization control of EHC according to the present embodiment will be described. In the hybrid system, the internal combustion engine is started when a predetermined engine start condition is satisfied. However, in this embodiment, the internal combustion engine is not immediately started when the predetermined engine start condition is satisfied, but before the internal combustion engine is started after the predetermined engine start condition is satisfied. The EHC carrier 31 is energized. Thereby, when the internal combustion engine 1 is actually started, the temperature of the EHC carrier 31 can be increased to the activation temperature of the three-way catalyst 31. As a result, the exhaust can be effectively purified immediately after the engine is started.

  Here, the transition of the temperature of the EHC carrier 31 and the load applied to the load sensor 10 when the EHC carrier 31 is energized will be described with reference to FIG. In FIG. 4, when a predetermined engine start condition is established, the temperature increase request flag of EHC 3 stored in the ECU 20 is turned ON at the time indicated by t1. As a result, power supply to the EHC carrier 31 is started. In this embodiment, the power supplied to the EHC carrier 3 is a predetermined constant value (reference power).

When power supply to the EHC carrier 31 is started, the temperature of the EHC carrier 31 starts to rise. Here, when the EHC carrier 31 generates heat by energization, the EHC carrier 31 expands as the temperature rises. When the EHC carrier 31 expands, the load applied to the load sensor 10 provided between the mat member 32 and the case 5 increases. Therefore, as shown in FIG. 4, while electric power is supplied to the EHC carrier 31, the load applied to the load sensor 10 increases as the temperature of the EHC carrier 31 increases. Therefore, the detection value of the load sensor 10 has a correlation with the temperature of the EHC carrier 31. Therefore, in this embodiment, the power supply to the EHC carrier 31 is controlled based on the detection value of the load sensor 10. Specifically, the load applied to the load sensor 10 corresponding to the target temperature set as the temperature of the EHC carrier 31 to be reached by the temperature rise due to energization is set as the target load. Moreover, the detection value of the load sensor 10 corresponding to this target load is set as the target value. The power supply to the EHC carrier 31 is continued while the detection value of the load sensor 10 is smaller than the target value, and when the detection value of the load sensor 10 reaches the target value (t2 in FIG. 4), the EHC carrier 31 is continued. Stop power supply to

  FIG. 5 is a flowchart showing a flow of energization control of the EHC according to the present embodiment. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20 at predetermined intervals. In this embodiment, the control unit according to the present invention is realized by the ECU 20 executing this flow.

  In this flow, first, in S101, it is determined whether or not the temperature increase request flag of the EHC 3 stored in the ECU 20 is ON. As described above, this temperature increase request flag is turned ON when a predetermined engine start condition is satisfied. If a negative determination is made in S101, that is, if the temperature increase request flag is OFF, the execution of this flow is temporarily terminated. On the other hand, when a positive determination is made in S101, the process of S102 is executed next.

  In S102, the current detection value Le of the load sensor 10 is read. Next, in S103, it is determined whether or not the detection value Le of the load sensor 10 read in S102 is greater than or equal to the target value Lt. If a negative determination is made in S103, that is, if the detection value Le of the load sensor 10 has not reached the target value Lt, it can be determined that the temperature of the EHC carrier 31 has not yet reached the target temperature. In this case, next, power supply to the EHC carrier 31 is executed (continued) in S106.

  On the other hand, when an affirmative determination is made in S103, that is, when the detection value Le of the load sensor 10 has reached the target value Lt, it can be determined that the temperature of the EHC carrier 31 has also reached the target temperature. In this case, next, in S104, the power supply to the EHC carrier 31 is stopped. Next, in S105, the temperature increase request flag of the EHC 3 stored in the ECU 20 is turned OFF. Thereafter, the execution of this flow is temporarily terminated.

  As described above, by controlling the power supply to the EHC carrier 31 based on the detection value of the load sensor 10, the temperature of the EHC carrier 31 can be adjusted to the target temperature.

  In consideration of the prior art, in order to adjust the temperature of the EHC carrier 31 to the target temperature, the exhaust gas flows out of the exhaust gas purification device 1 through the EHC carrier 31 to the exhaust pipe 2 downstream of the exhaust gas purification device 1. It is conceivable to employ a configuration in which an exhaust temperature sensor for detecting the temperature of the exhaust gas is provided and the temperature of the EHC carrier 31 is estimated based on the detection value of the exhaust temperature sensor. However, in such a configuration, a certain distance is generated between the exhaust temperature sensor and the EHC carrier 31. Further, when the EHC carrier 31 is energized, it is before the internal combustion engine is started. Therefore, it is difficult to transfer the heat generated in the EHC carrier 31 to the exhaust temperature sensor via the exhaust. Therefore, it may be difficult to estimate the temperature of the EHC carrier 31 with high accuracy based on the detection value of the exhaust temperature sensor. Therefore, if the power supply to the EHC carrier 31 is controlled based on the detection value of the exhaust temperature sensor, there is a possibility that an excessive supply or insufficient supply of power may be caused.

  In contrast, in this embodiment, the load sensor 10 is provided between the case 5 and the mat member 32 in the EHC 3. Therefore, the change in the load detected by the load sensor 10 is more than the change in the exhaust temperature detected by the exhaust temperature sensor when the exhaust temperature sensor is provided in the exhaust pipe 2 downstream of the exhaust purification device 1. The followability to the temperature change of the EHC carrier 31 is high. Even if the exhaust gas is not flowing into the exhaust pipe 2 because it is before the internal combustion engine is started, if the EHC carrier 31 expands as its temperature rises, the load applied to the load sensor 10 increases. . Therefore, even if no exhaust flows in the exhaust pipe 2, the load detected by the load sensor 10 has a high correlation with the temperature of the EHC carrier 31.

  In the present embodiment, the electrical insulation between the EHC carrier 31 and the load sensor 10 is ensured by the mat member 32. Here, in order to detect the temperature of the EHC carrier 31, a configuration in which a temperature sensor is provided at a position similar to the installation position of the load sensor 10 according to the present embodiment is conceivable. However, in such a configuration, since the mat member 32 functions as a heat insulating material, the correlation between the detected value of the temperature sensor and the temperature of the EHC carrier 31 may be reduced. Therefore, from the correlation between the detection value of the load sensor 10 according to the present embodiment and the temperature of the EHC carrier 31, the detection value of the temperature sensor when the temperature sensor is installed at the same position as the installation position of the load sensor 10 The correlation with the temperature of the EHC carrier 31 becomes low.

  As described above, according to the present embodiment, in the EHC 3, by controlling the power supply to the EHC carrier 31 based on the detection value of the load sensor 10 showing a high correlation with the temperature of the EHC carrier 31, An excessive supply or insufficient supply of electric power to the EHC carrier 31 can be suppressed. As a result, the temperature of the EHC carrier 31 can be adjusted to the target temperature with higher accuracy.

  Note that the energization timing to the EHC carrier 31 is not limited to before the internal combustion engine is started. For example, the EHC carrier 31 may be energized when there is a temperature increase request for the EHC 3 and the rear catalyst 4 after the internal combustion engine is started. In this case, for example, when the detected value of the load sensor 10 becomes equal to or less than a predetermined energization request value during operation of the internal combustion engine, power supply to the EHC carrier 31 is executed. Further, after the power supply to the EHC carrier 31 is started, the power supply to the EHC carrier 31 is stopped when the detected value of the load sensor 10 reaches a predetermined energization stop value. When performing such energization control, the energization stop value may be set to a value larger than the energization request value in order to suppress hunting.

(Load sensor placement)
Further, in this embodiment, as shown in FIG. 2, the load sensor 10 is provided between the case 5 and the mat member 32 at an intermediate position between the pair of electrodes 33 a and 33 b in the circumferential direction of the EHC carrier 31. Yes. Here, when the EHC carrier 31 is energized, in the EHC carrier 31, the temperatures in the vicinity of the electrodes 33 a and 33 b that supply power to the EHC carrier 31 are highest. On the other hand, in the EHC carrier 31, the temperature at the position farthest from each of the electrode 33a and the electrode 33b, that is, in the vicinity of the intermediate position between the electrode 33a and the electrode 33b on the outer peripheral surface of the EHC carrier 31 is The lowest. That is, in the present embodiment, the load sensor 10 is provided at a position corresponding to a portion where the temperature is lowest in the EHC carrier 31 when the EHC carrier 31 is energized. Therefore, if the detection value of the load sensor 10 has reached the target value, it can be determined with a higher probability that the entire EHC carrier 31 has been heated to the target temperature or higher.

However, the installation position of the load sensor 10 is not limited to the intermediate position between the pair of electrodes 33a and 33b in the circumferential direction of the EHC carrier 31 as described above. However, the load sensor 10 is pressed with the thermal expansion of the EHC carrier 31. Therefore, if the installation position of the load sensor 10 is near the end of the mat member 32, the EHC carrier 31 is repeatedly expanded and contracted, so that the relative installation position of the load sensor 10 with respect to the mat member 32 is reached. May deviate from the original position. As a result, when a part of the load sensor 10 protrudes from the end of the mat member 32, the correlation between the detected value of the load sensor 10 and the temperature of the EHC carrier 31 is different from the initial one. Become. Similarly, if the installation position of the load sensor 10 is in the vicinity of the through hole 32a of the mat member 32, the position of the load sensor 10 deviates from the initial position, so that a part of the load sensor 10 is passed through the through hole 32a. It may be in a state of protruding to the side. Even in such a case, the correlation between the detected value of the load sensor 10 and the temperature of the EHC carrier 31 is different from the initial one. In such cases, even if the power supply to the EHC carrier 31 is controlled based on the detection value of the load sensor 10, it is difficult to adjust the temperature of the EHC carrier 31 to the target temperature with high accuracy. Further, when a part of the load sensor 10 protrudes from the end of the mat member 32, the load sensor 10 is exposed to the exhaust. There is a possibility that a substance adheres to the load sensor 10. Such a thing is not preferable from the viewpoint of leakage prevention.

  Considering the above problems, even if the relative installation position of the load sensor 10 with respect to the mat member 32 is deviated from the initial position due to repeated expansion and contraction of the EHC carrier 31, the entire load sensor 10 is It is preferable to arrange the load sensor 10 at a position where the state covered with the mat member 32 is maintained. That is, the installation position of the load sensor 10 is as shown in the area Ar1 shown by hatching in FIG. It is preferable to set the position away from the end of the mat member 32 to some extent. Note that the installation position of the load sensor 10 in the EHC 3 according to the present embodiment is near the center of the region Ar1 in FIG.

  In the present embodiment, as shown in FIG. 2, the load sensor 10 is sandwiched between the inner wall surface of the case 5 and the outer wall surface of the mat member 32. However, instead of this, as shown in FIG. 6, a configuration in which the load sensor 10 is embedded in the mat member 32 may be adopted. Even in such a configuration, when the EHC carrier 31 expands, the load applied to the load sensor 10 increases. Therefore, the detection value of the load sensor 10 has a correlation with the temperature of the EHC carrier 31. Even in such a configuration, the mat member 32 can ensure electrical insulation between the EHC carrier 31 and the load sensor 10.

<Example 2>
The configuration of the exhaust gas purification apparatus according to the present embodiment is the same as that of the first embodiment. Hereinafter, differences between the EHC energization control according to the present embodiment and the first embodiment will be described.

  In the first embodiment described above, the supplied power when the EHC carrier 31 is energized is set to a constant reference power. However, in practice, even if the supplied power is constant, the temperature of the EHC carrier 31 is caused by a change in the state of the EHC carrier 31 or the electrodes 33a and 33b, adhesion of a conductive substance to the EHC carrier 31, and the like. There are cases where variations occur in the manner of transition. If the temperature of the EHC carrier 31 rises rapidly due to such variation in the temperature transition of the EHC carrier 31, there is a risk that thermal degradation of the EHC carrier 31 is promoted. In addition, since the variation in the temperature transition of the EHC carrier 31 occurs, on the other hand, if the rate of temperature rise of the EHC carrier 31 is excessively reduced, the temperature of the EHC carrier 31 may not be sufficiently increased.

Therefore, in the present embodiment, a reference load is set while power supply to the EHC carrier 31 is being executed. Here, the reference load is a load to be detected by the load sensor 10 while the detection value of the load sensor 10 is moving toward the target value during execution of power supply to the EHC carrier 31. That is, the transition of the reference load is the transition of the load that should be originally applied to the load sensor 10 during execution of power supply to the EHC carrier 31. Such a reference load can be determined in advance based on experiments or the like. In this embodiment, while the power supply to the EHC carrier 31 is being executed, the degree of deviation of the actual detection value of the load sensor 10 with respect to the reference load is calculated, and the EHC carrier 31 is calculated based on the degree of deviation. Correct the power supplied to the.

  FIG. 7 is a flowchart showing a flow of energization control of the EHC according to the present embodiment. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20 at predetermined intervals. Note that the processing in each step from S101 to S106 of this flow is the same as the processing in each step from S101 to S106 in the flow of energization control of the EHC according to the first embodiment shown in FIG. Therefore, description of the processing in these steps is omitted. In the present embodiment, the control unit according to the present invention is realized by the ECU 20 executing this flow.

  In this flow, if a negative determination is made in S103, that is, if the detection value Le of the load sensor 10 has not reached the target value Lt, then the process of S204 is executed. In S204, the current reference load Lb is calculated. Here, the transition of the reference load Lb during execution of power supply to the EHC carrier 31 may be stored in the ECU 20 as a map, and the reference load Lb may be calculated using the map. In addition, a function for calculating the reference load Lb using the power supplied to the EHC carrier 31 (here, the reference power) and the elapsed time since the start of power supply to the EHC carrier 31 as parameters is stored in the ECU 20. The reference load Lb may be calculated using a function.

Ｒｂ：乖離率
Ｌｅ：Ｓ１０２で読み込まれた荷重センサ１０の検出値
Ｌｂ：Ｓ２０４で算出された基準荷重 Next, in S205, a deviation rate Rb that is an index value indicating the degree of deviation of the actual detection value of the load sensor 10 with respect to the reference load is calculated. Here, the deviation rate Rb is calculated using Equation 1 below.

Rb: Deviation rate Le: Detection value of load sensor 10 read in S102 Lb: Reference load calculated in S204

  Next, in S206, it is determined whether or not the deviation rate Rb calculated in S205 is larger than a predetermined deviation rate R0. Here, the predetermined deviation rate R0 is a threshold with which it can be determined that the power supplied to the EHC carrier 31 should be corrected when the deviation rate Rb is greater than the predetermined deviation rate R0. The predetermined deviation rate R0 is determined in advance based on experiments or the like and is stored in the ECU 20.

  If an affirmative determination is made in S206, then in S207, the power supplied to the EHC carrier 31 is corrected. Here, when the detected value Le of the load sensor 10 is larger than the reference load Lb, that is, when the detected value Le of the load sensor 10 is shifted to the increasing side with respect to the reference load Lb, the power supplied to the EHC carrier 31 is increased. Reduce the power supply from the current level. On the other hand, when the detected value Le of the load sensor 10 is smaller than the reference load Lb, that is, when the detected value Le of the load sensor 10 is shifted to the decreasing side with respect to the reference load Lb, the power supplied to the EHC carrier 31 is currently Increase the power supply. At this time, the correction amount (or correction rate) of the power supplied to the EHC carrier 31 is determined based on the deviation rate Rb calculated in S205. Following S207, the process of S106 is executed. In this case, in S106, the power corrected in S207 is supplied to the EHC carrier 31.

On the other hand, if a negative determination is made in S206, that is, if the divergence rate Rb is equal to or less than the predetermined divergence rate R0, then the S106 process is executed. In this case, in S106, power supply to the EHC carrier 31 is executed while maintaining the current power supply.

  FIG. 8 is a diagram showing a transition between the power supplied to the EHC carrier 31 and the detection value of the load sensor 10 when the control flow described above is executed. In FIG. 8, a line L <b> 1 indicates a transition of power supplied to the EHC carrier 31, and a line L <b> 2 indicates a transition of a detection value of the load sensor 10. In FIG. 8, the alternate long and short dash line represents the reference power, and the alternate long and two short dashes line represents the transition of the reference load.

  As shown in FIG. 8, by executing the control flow described above, the load actually applied to the load sensor 10 changes to the transition of the reference load as much as possible while the power supply to the EHC carrier 31 is being executed. The electric power supplied to the EHC carrier 31 is controlled so as to move along. For this reason, it is possible to cause the load applied to the load sensor 10 to reach the target load more quickly while suppressing excessive power supply to the EHC carrier 31. Therefore, the temperature of the EHC carrier 31 can be raised to the target temperature more quickly while suppressing the promotion of thermal degradation of the EHC carrier 31.

<Example 3>
The configuration of the exhaust gas purification apparatus according to the present embodiment is different from the configuration of the exhaust gas purification apparatus according to the first embodiment in that a plurality of load sensors are provided in the EHC. Hereinafter, the difference of the configuration of the EHC according to the present embodiment from the first embodiment will be described. FIG. 9 is a diagram illustrating a schematic configuration of the EHC according to the present embodiment. FIG. 9 shows a cross section in a direction perpendicular to the flow direction of the EHC exhaust gas according to the present embodiment (the direction indicated by the arrow in FIG. 1).

  In the present embodiment, the load sensors 11 and 12 are provided in the EHC 3 in addition to the load sensor 10 disposed at the same position as in the first embodiment. Hereinafter, the load sensor 10 is referred to as a first load sensor 10, the load sensor 11 is referred to as a second load sensor 11, and the load sensor 12 is referred to as a third load sensor. The configuration of the second load sensor 11 and the third load sensor 12 itself is the same as that of the first load sensor 10.

  As shown in FIG. 9, the second load sensor 11 is provided between the case 5 and the mat member 32 at a position overlapping with a portion in the vicinity of the circumferential end of the electrode 33 a. Further, the third load sensor 12 is provided between the case 5 and the mat member 32 at a position overlapping with a portion in the vicinity of the circumferential end of the electrode 33b. That is, similarly to the first load sensor 10, the second load sensor 11 and the third load sensor 12 are also sandwiched between the inner wall surface of the case 5 and the outer wall surface of the mat member 32. Similarly to the first load sensor 10, the second load sensor 11 and the third load sensor 12 are also electrically connected to the ECU 20, and the detection values of the second load sensor 11 and the third load sensor 12 are the ECU 20. Is input.

  When the EHC carrier 31 generates heat when energized and the EHC carrier 31 expands as the temperature rises, not only the load applied to the first load sensor 10 but also the load applied to the second load sensor 11 and the third load sensor 12 respectively. Will also increase. Therefore, not only the detection value of the first load sensor 10 but also the detection values of the second load sensor 11 and the third load sensor 12 are correlated with the temperature of the EHC carrier 31.

Further, as described above, when the EHC carrier 31 is energized, in the EHC carrier 31, the temperatures in the vicinity of the electrodes 33a and 33b that supply power to the EHC carrier 31 are highest. On the other hand, the temperature of the portion in the vicinity of the intermediate position between the electrode 33a and the electrode 33b on the outer peripheral surface of the EHC carrier 31 is lowest. In other words, in the present embodiment, when the EHC carrier 31 is energized, the first load sensor 10 is provided at a position corresponding to the portion of the EHC carrier 31 where the temperature is lowest, and the EHC carrier 31 is energized. In this case, the second load sensor 11 and the third load sensor 12 are provided at a position corresponding to the highest temperature portion of the EHC carrier 31.

  Also in the present embodiment, when the energization of the EHC carrier 31 is started, a predetermined reference power similar to that in the first embodiment is supplied to the EHC carrier 31. Here, in EHC3, local oxidation may occur in the electrodes 33a and 33b. For example, when the EHC carrier 31 is cracked due to thermal stress and either the electrode 33a or the electrode 33b is exposed to air (oxygen), the portion of the electrode exposed to air (oxygen) is oxidized. It becomes easy to progress. Hereinafter, the electrode on which local oxidation has occurred may be referred to as an “oxidation electrode”. In this oxidation electrode, the resistance value of the oxidized portion increases. For this reason, if the electrodes 33a and 33b continue to supply power in the same manner as in a normal state in the state where local oxidation has occurred in the electrode 33a or the electrode 33b, the temperature of the oxidation electrode excessively increases, The oxidation electrode may be damaged or melted.

  As described above, when local oxidation occurs in the electrode 33a or the electrode 33b, the temperature of the oxidation electrode becomes higher when power is supplied to the EHC carrier 31 than when the electrodes 33a and 33b are in a normal state. . Along with this, the temperature in the vicinity of the oxidation electrode in the EHC carrier 31 also increases. If it does so, when the electrode 33a turns into an oxidation electrode, the detection value of the 2nd load sensor 11 will increase compared with the time of normal. Further, when the electrode 33b is an oxidation electrode, the detection value of the third load sensor 12 is increased as compared with the normal time. On the other hand, the first load sensor 10 is relatively far from the electrode 33a than the second load sensor 11, and is relatively far from the electrode 33b than the third load sensor 33c. Therefore, even if the temperature in the vicinity of the oxidation electrode in the EHC carrier 31 increases due to local oxidation in the electrode 33a or the electrode 33b, the influence on the detection value of the first load sensor 10 is the second load sensor 11. Or it is small compared with the influence on the detection value of the 3rd load sensor 12. Therefore, when the electrode 33a becomes an oxidation electrode, the difference between the detection value of the first load sensor 10 and the detection value of the second load sensor 11 increases compared to the normal time. Moreover, when the electrode 33b becomes an oxidation electrode, the difference between the detection value of the first load sensor 10 and the detection value of the third load sensor 12 is increased compared to the normal time. Therefore, in this embodiment, the difference between the detection value of the first load sensor 10 and the detection value of the second load sensor 11, or the difference between the detection value of the first load sensor 10 and the detection value of the third load sensor 12. Based on the above, the power supply to the EHC carrier 31 is controlled.

  10 and 11 are flowcharts showing the flow of energization control of the EHC according to the present embodiment. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20 at predetermined intervals. Note that the processes in steps S101 and S104 to S106 of this flow are the same as the processes in steps S101 and S104 to S106 of the EHC energization control flow according to the first embodiment shown in FIG. It is the same. Therefore, description of the processing in these steps is omitted. In the present embodiment, the control unit according to the present invention is realized by the ECU 20 executing this flow.

  In this flow, when an affirmative determination is made in S101, the process of S302 is executed next. In S302, the current detection value Le1, the second load sensor detection value Le2, and the third load sensor detection value Le3 are read. Next, in S303, it is determined whether or not the detection value Le1 of the first load sensor 10 read in S302 is greater than or equal to the target value Lt. The process of S303 is substantially the same as the process of S103 of the flow of energization control of EHC according to the first embodiment shown in FIG. If an affirmative determination is made in S303, that is, if the detected value Le1 of the first load sensor 10 has reached the target value Lt, the process of S104 is then executed.

On the other hand, if a negative determination is made in S303, that is, if the detection value Le1 of the first load sensor 10 has not reached the target value Lt, then the process of S304 is executed. In S304, the current load difference DLe is calculated. Here, the difference between the detection value Le1 of the first load sensor 10 read in S302 and the detection value Le2 of the second load sensor 11, and the detection value Le1 of the first load sensor 10 read in S302 and the third load. Of the differences from the detection value Le3 of the sensor 12, the larger difference is calculated as the load difference DLLe.

  Next, in S305, it is determined whether or not the load difference DLe calculated in S304 is larger than a predetermined first load difference DLe1. Here, since the first load difference DLe1 is locally oxidized in the electrode 33a or the electrode 33b, if the reference power is continuously supplied to the EHC carrier 31, the electrode 33a or the electrode 33b is damaged or melted. This is the threshold value of the load difference that can be determined to be a concern. Such a first load difference DLe1 is determined in advance based on experiments or the like, and is stored in the ECU 20. In the present embodiment, the first load difference DLe1 corresponds to the first predetermined amount according to the present invention.

  If a negative determination is made in S305, that is, if the load difference DLe is equal to or less than the first load difference DLe1, the process of S310 is executed next. In S310, the supply power to the EHC carrier 31 is set to the current supply power Pp. It should be noted that the reference power is set to the supply power Pp while the load difference DLe is maintained below the first load difference DLe1 since the energization of the EHC carrier 31 is started. Next, power supply to the EHC carrier 31 is executed in S106. That is, in this case, the supply of the current supply power Pp to the EHC carrier 31 is continued. Further, while the load difference DLe is maintained at the first load difference DLe1 or less after the energization of the EHC carrier 31 is started, the supply of the reference power to the EHC carrier 31 is continued.

  On the other hand, when an affirmative determination is made in S305, it is determined whether or not the load difference DLe calculated in S304 is greater than a predetermined second load difference DLe2. Here, the second load difference DLe2 is larger than the first load difference DLe2. Since the second load difference DLe2 is locally oxidized at the electrode 33a or the electrode 33b, there is a possibility that the electrode 33a or the electrode 33b may be damaged or melted if the power supply to the EHC carrier 31 is continued. It is the threshold value of the load difference that can be determined as follows. Such a second load difference DLe2 is determined in advance based on experiments or the like and is stored in the ECU 20. In the present embodiment, the second load difference DLe2 corresponds to the second predetermined amount according to the present invention.

  If an affirmative determination is made in S306, then the power supply to the EHC carrier 31 is stopped in S104. In this case, power supply to the EHC carrier 31 is stopped before the detection value Le1 of the first load sensor 10 reaches the target value Lt, that is, before the temperature of the EHC carrier 31 reaches the target temperature.

  On the other hand, if a negative determination is made in S306, that is, if the load difference DLe is greater than the first load difference DLe1 and less than or equal to the second load difference DLe2, the process of S307 is executed next. In S307, the guard power Plimit is calculated based on the current load difference DLe calculated in S304. FIG. 12 is a diagram showing a map used for calculating the guard power Plimit in S304. Such a map is stored in the ECU 20 in advance. In FIG. 12, the horizontal axis represents the load difference DLe, and the vertical axis represents the guard power Plimit. As shown in FIG. 12, the guard power Plimit calculated when the load difference DLe is greater than the first load difference DLe1 and less than or equal to the second load difference DLe2 is calculated as a smaller value as the load difference DLe increases.

Next, in S308, it is determined whether or not the current supply power Pp to the EHC carrier 31 is larger than the guard power Plimit calculated in S307. If a negative determination is made in S308, that is, if the current supply power Pp to the EHC carrier 31 is equal to or less than the guard power Plimit, the process of S310 is executed next. As described above, in S310, the power supplied to the EHC carrier 31 is set to the current power supply Pp. On the other hand, when an affirmative determination is made in S308, the process of S309 is executed next. In S309, the power supplied to the EHC carrier 31 is set to the guard power Plimit calculated in S307. Next, power supply to the EHC carrier 31 is executed in S106. That is, in this case, supply of the guard power Plimit to the EHC carrier 31 is executed.

  According to the control flow described above, the reference power is supplied to the EHC carrier 31 after the energization of the EHC carrier 31 is started until the load difference DLe exceeds the first load difference DLe1 (the electrodes 33a and 33b are connected). Since both are in a normal state, if the detected value Le1 of the first load sensor 10 reaches the target value Lt without the load difference DLe exceeding the first load difference DLLe1, the power to the EHC carrier 31 at that time Supply is stopped.) Since local oxidation occurs in the electrode 33a or the electrode 33b, the temperature of the oxidation electrode rises while power is supplied to the EHC carrier 31, and the load difference DLe becomes the first load difference DLe1. When it becomes larger, the electric power supplied to the EHC carrier 31 is reduced. Thereby, it can suppress that the temperature of an oxidation electrode rises excessively. Therefore, heating of the three-way catalyst 31a can be continued while suppressing breakage or melting of the electrodes 33a and 33b.

  However, even if the power supplied to the EHC carrier 31 is reduced, the load difference DLe does not necessarily decrease immediately. Therefore, according to the control flow described above, while the load difference DLe tends to increase, the guard power Plimit is gradually reduced according to the increase. That is, the power supplied to the EHC carrier 31 is gradually reduced until the load difference DLe tends to be maintained or decreased. When the load difference DLe tends to be maintained or decreased due to the gradual reduction of the power supplied to the EHC carrier 31, the supply power at the time when the load difference DLe tends to be maintained or decreased after that time. Thus, the power supply to the EHC carrier 31 is executed. According to this, it is possible to reduce the amount of power supplied to the EHC carrier 31 as much as possible while suppressing breakage or melting of the electrodes 33a and 33b. Therefore, it is possible to raise the temperature of the EHC carrier 31 as quickly as possible while suppressing breakage or melting of the electrodes 33a and 33b.

  In addition, when the load difference DLe becomes larger than the first load difference DLe1 while the power supply to the EHC carrier 31 is being executed, the control content when reducing the power supplied to the EHC carrier 31 is as described above. The control content is not limited to this. For example, when the load difference DLe exceeds the first load difference DLe1 after the start of energization of the EHC carrier 31, the power supplied to the EHC carrier 31 is reduced to a corrected power that is a predetermined amount smaller than the reference power, and thereafter The power supplied to the EHC carrier 31 may be maintained at the correction power.

  Further, since the load difference DLe is larger than the first load difference DLe1 while the power supply to the EHC carrier 31 is being executed, the load difference DLe is maintained even if the power supplied to the EHC carrier 31 is reduced. It may continue to increase without trend or decline. In such a case, it is considered that the oxidation of the electrode 33a or the electrode 33b has progressed to some extent. According to the control flow described above, in such a case, when the load difference DLe reaches the second load difference DLe2, the power supply to the EHC carrier 31 is stopped. According to this, it is possible to suppress the electrodes 33a and 33b from being damaged or melted.

However, in this case, as described above, the power supply to the EHC carrier 31 is stopped before the temperature of the EHC carrier 31 reaches the target temperature. However, even in such a case, when the internal combustion engine is started, the temperature of the EHC carrier 31 (that is, the temperature of the three-way catalyst 31a) can be raised to some extent. Therefore, the three-way catalyst 31a can be activated earlier after the internal combustion engine is started. Further, by suppressing the breakage or melting of the electrodes 33a and 33b, the three-way catalyst 31a can be heated by energizing the EHC carrier 31 before the next start of the internal combustion engine.

  In addition, arrangement | positioning of the load sensor in a present Example is not restricted to the position shown in FIG. If load sensors are disposed at positions relatively close to and relatively far from the electrode 33a, when the electrode 33a becomes an oxidation electrode, the difference between the detection values of these load sensors. However, it becomes larger than when the electrode 33a is in a normal state. Further, if load sensors are arranged at positions relatively close to and relatively far from the electrode 33b, when the electrode 33b becomes an oxidation electrode, detection values of these load sensors are detected. Is larger than that in the normal state of the electrode 33ab. For this reason, load sensors are arranged at positions relatively close to and far from the electrode 33a, and positions relatively close to and far from the electrode 33b. If a load sensor is provided for each, it is possible to control power supply to the EHC carrier 31 based on the same load difference as described above.

(Modification)
FIG. 13 is a flowchart showing a flow of EHC energization control according to a modification of the present embodiment. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20 at predetermined intervals. Note that the processes in steps S101 and S104 to S106 of this flow are the same as the processes in steps S101 and S104 to S106 of the EHC energization control flow according to the first embodiment shown in FIG. It is the same. Further, the processing in S304 and S305 of this flow is the same as the processing in S304 and S305 of the flow of EHC energization control shown in FIG. In the present modification, the control unit according to the present invention is realized by the ECU 20 executing this flow.

  In this flow, when a negative determination is made in S305, that is, when the load difference DLe is equal to or smaller than the first load difference DLe1, power supply to the EHC carrier 31 is executed in S106. In this case, reference power is supplied to the EHC carrier 31. On the other hand, when an affirmative determination is made in S305, power supply to the EHC carrier 31 is then stopped in S104. In the present modification, the first load difference DLe1 corresponds to the second predetermined amount according to the present invention.

  That is, in the present modification, when the load difference DLe becomes larger than the first load difference DLe1 while the power supply to the EHC carrier 31 is being executed, the power supply to the EHC carrier 31 is stopped at that time. Is done. Such control can also prevent the electrodes 33a and 33b from being damaged or melted.

DESCRIPTION OF SYMBOLS 1 ... Exhaust purification device 2 ... Exhaust pipe 3 ... Electric heating type catalyst (EHC)
31..EHC carrier 32..Mat members 33a, 33b..Electrode 4 ... latter stage catalyst 41..catalyst carrier 42..mat member 5 ... case 6 ... metal foil 7 ... electrode cover 10 ..Load sensor (first load sensor)
11. Second load sensor 12. Third load sensor 20. ECU

Claims (7)

A control system for an electrically heated catalyst provided in an exhaust passage of an internal combustion engine,
The electrically heated catalyst generates heat when energized, a heating element that heats the catalyst by generating heat, a case that houses the heating element, and a mat that is sandwiched between the heating element and the case to insulate electricity. A member, and
A load sensor provided between the case and the mat member or in the mat member for detecting a load applied to the case;
And a control unit that controls power supply to the heating element based on a detection value of the load sensor.   The control unit stops power supply to the heating element when the detection value of the load sensor reaches a target value corresponding to a predetermined target load after the start of power supply to the heating element. The control system of the electrically heated catalyst as described in 1.   While the control unit is executing power supply to the heating element, the load sensor detects a reference load that is a load to be detected while the detection value of the load sensor is moving toward the target value. When the deviation of the actual detection value of the load sensor is greater than a predetermined level, the power supplied to the heating element when the actual detection value of the load sensor deviates to the increase side with respect to the reference load transition The control system for an electrically heated catalyst according to claim 2, wherein the electric power supplied to the heating element is increased when the actual detection value of the load sensor deviates from the reference load transition. . A pair of electrodes for supplying power to the heating element is connected to an outer peripheral surface of the heating element in contact with the mat member of the electric heating catalyst, and each electrode in the pair of electrodes is an outer periphery of the heating element. Extending in the circumferential direction and axial direction along the surface, and facing each other across the heating element,
4. The load sensor according to claim 2, wherein the load sensor is disposed between the case and the mat member or in the mat member at an intermediate position between the pair of electrodes in the circumferential direction of the heating element. Control system for electrically heated catalyst. A pair of electrodes for supplying power to the heating element is connected to an outer peripheral surface of the heating element in contact with the mat member of the electric heating catalyst, and each electrode in the pair of electrodes is an outer periphery of the heating element. Extending in the circumferential direction and axial direction along the surface, and facing each other across the heating element,
The load sensor is disposed in each of a position relatively close to one electrode and a position relatively distant from the one electrode in the circumferential direction of the heating element,
When the load difference, which is the difference between the detection value of one load sensor and the detection value of the other load sensor, is larger than a first predetermined amount during the power supply to the heating element, the control The control system for an electrically heated catalyst according to claim 1, wherein the unit reduces power supplied to the heating element.   While the power supply to the heating element is being executed, when the load difference becomes larger than the first predetermined amount and the power supplied to the heating element is reduced, the control unit causes the load difference to be reduced. The power supplied to the heating element is gradually reduced until the maintenance tendency or the reduction tendency is reached, and the power at that time is maintained after the load difference becomes the maintenance tendency or the reduction tendency. The control system for an electrically heated catalyst according to claim 5, wherein power is supplied to the battery. A pair of electrodes for supplying power to the heating element is connected to an outer peripheral surface of the heating element in contact with the mat member of the electric heating catalyst, and each electrode in the pair of electrodes is an outer periphery of the heating element. Extending in the circumferential direction and axial direction along the surface, and facing each other across the heating element,
The load sensor is disposed in each of a position relatively close to one electrode and a position relatively distant from the one electrode in the circumferential direction of the heating element,
While the power supply to the heating element is being performed, if the load difference, which is the difference between the detection value of one load sensor and the detection value of the other load sensor, is greater than a second predetermined amount, the heat generation The control system for an electrically heated catalyst according to claim 1, wherein power supply to the body is stopped.

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