JP7317170B2 - engine - Google Patents

Description

The present invention relates to engines. Specifically, it relates to a configuration in which an oxidation catalyst is installed in an exhaust passage of an engine.

2. Description of the Related Art Conventionally, an engine is known in which an oxidation catalyst is installed in an exhaust passage. Patent Document 1 discloses an engine of this kind.

The configuration of Patent Document 1 includes an oxidation catalyst installed in an exhaust pipe, a first exhaust temperature sensor installed upstream of the oxidation catalyst in the exhaust pipe, and a second exhaust temperature sensor installed downstream of the oxidation catalyst in the exhaust pipe. and an exhaust temperature sensor. Then, after execution of the post-injection, it is determined whether the oxidation catalyst is abnormal based on the upstream exhaust temperature detected by the first exhaust temperature sensor and the downstream exhaust temperature detected by the second exhaust temperature sensor. Whether or not, that is, whether or not it is degraded is determined.

Japanese Unexamined Patent Application Publication No. 2010-203238

The configuration of Patent Literature 1 requires execution of post-injection in order to determine abnormality of the oxidation catalyst. However, post-injection causes deterioration of fuel efficiency and deterioration of the oxidation catalyst, so it has been desired to suppress the number of post-injections.

The present invention has been made in view of the above circumstances, and its object is to determine whether or not the oxidation catalyst is functioning normally without performing post-injection, that is, without supplying unburned fuel to the oxidation catalyst. To provide an engine capable of determining

An engine according to one aspect of the present invention includes an oxidation catalyst, a temperature difference calculation section, and a determination section. The oxidation catalyst is installed in an exhaust passage through which exhaust gas can flow. The temperature difference calculation unit calculates a temperature difference between an exhaust gas temperature on the upstream side of the oxidation catalyst in the exhaust gas flow direction and an exhaust gas temperature on the downstream side of the oxidation catalyst in the exhaust gas flow direction during engine operation. to calculate The determination unit determines whether the oxidation catalyst is functioning normally by determining whether the absolute value of the temperature difference calculated by the temperature difference calculation unit is greater than a predetermined temperature threshold. Judgment [1] is performed.

1 is a diagram showing the overall configuration of an engine according to one embodiment of the present invention; FIG. A block diagram showing the main electrical configuration of the engine. FIG. 5 is a diagram showing the relationship between a temperature change speed vector related to the detection result of the upstream side exhaust temperature sensor and a temperature change speed vector related to the detection result of the downstream side exhaust temperature. 4 is a graph showing a comparison of changes in temperature change rate on the upstream side and the downstream side with and without a catalyst. 4 is a graph showing a comparison of changes in temperature difference between the upstream side and the downstream side with and without a catalyst. 4 is a flowchart showing a process for determining the presence or absence of an oxidation catalyst; 4 is a flowchart showing a subroutine for diagnosing an oxidation catalyst by post-injection;

Next, embodiments of the present invention will be described with reference to the drawings. First, with reference to FIGS. 1 and 2, the basic configuration of an engine 1 according to an embodiment of the invention will be described. FIG. 1 is a diagram showing the overall configuration of an engine 1. As shown in FIG. FIG. 2 is a block diagram showing the main electrical configuration of the engine 1. As shown in FIG.

As shown in FIG. 1, the engine 1 includes an intake section 2, a power generation section 3, an exhaust section 4, and an ECU 5 as a control device.

The intake portion 2 sucks air from the outside. The intake section 2 includes an intake pipe 11 , an intake manifold 12 , a throttle valve 13 and a supercharger 14 .

The intake pipe 11 constitutes an intake passage. The intake pipe 11 is connected to a combustion chamber 23, which will be described later, via an intake manifold 12, so that air taken in from the outside can flow inside.

The intake manifold 12 is connected to the downstream end of the intake pipe 11 in the direction in which intake air flows in the intake passage. The intake manifold 12 distributes the air supplied through the intake pipe 11 according to the number of cylinders of the power generating section 3 . The air after distribution is supplied to the combustion chamber 23 formed in each cylinder.

The throttle valve 13 is arranged in the middle of the intake passage. The throttle valve 13 changes the cross-sectional area of the intake passage by changing its opening according to a control command from the ECU 5 . Thereby, the amount of air supplied to the intake manifold 12 can be adjusted.

The power generation section 3 includes a cylinder block and a cylinder head 21 . A piston, a crankshaft, and the like are arranged inside the cylinder block. A plurality of (four in this embodiment) cylinders 22 are formed in the upper part of the cylinder block.

A cylinder head 21 is arranged above the cylinder block. An intake manifold 12 is provided for each cylinder 22 in the cylinder head 21 and the cylinder block. An injector 25 for injecting fuel into the intake manifold 12 and the like are attached to the cylinder head 21 .

In each combustion chamber 23 , after the air from the intake manifold 12 is compressed, the injector 25 injects fuel supplied from a fuel supply section (not shown). As a result, the fuel can be burned in the intake manifold 12 to reciprocate the piston up and down. The power thus obtained is transmitted to appropriate devices downstream of the power through a crankshaft or the like.

The supercharger 14 has a turbine 27 , a shaft 28 and a compressor 29 . Compressor 29 is connected to turbine 27 via shaft 28 . In this configuration, when the turbine 27 is rotated by the flow of exhaust gases discharged from the combustion chamber 23, the compressor 29 is rotated. As a result, air purified by an air cleaner (not shown) is compressed and forcibly taken in.

The exhaust part 4 discharges the exhaust gas generated inside the combustion chamber 23 to the outside. The exhaust section 4 includes an exhaust pipe 31 , an exhaust manifold 32 and an exhaust purification device 33 .

The exhaust pipe 31 constitutes an exhaust passage. The exhaust pipe 31 is connected to the combustion chamber 23 via an exhaust manifold 32 and allows the exhaust gas discharged from the combustion chamber 23 to flow therein.

The exhaust manifold 32 is connected to the upstream end of the exhaust pipe 31 in the direction in which the exhaust gas flows. The exhaust manifold 32 collectively guides the exhaust gas generated in each combustion chamber 23 to the exhaust pipe 31 .

In the following description, the upstream side in the direction in which the exhaust gas flows may be simply referred to as the upstream side, and the downstream side in the direction in which the exhaust gas may flow may simply be referred to as the downstream side.

The exhaust purification device 33 is arranged in the middle of the exhaust passage. The exhaust purification device 33 has a housing case 35 , an oxidation catalyst 36 and a filter 37 . The housing case 35 can introduce exhaust gas into the interior and send out the exhaust gas to the outside. The oxidation catalyst 36 and the filter 37 are housed in the housing case 35 .

The oxidation catalyst 36 is arranged upstream of the filter 37 in the storage case 35 . In this way, the exhaust purification device 33 introduces the exhaust gas discharged from the combustion chamber 23 into the housing case 35, passes through the oxidation catalyst 36 and the filter 37, carbon monoxide, nitrogen monoxide, and particles contained in the exhaust gas. Remove any substances such as

The oxidation catalyst 36 is made of platinum or the like, and is a catalyst for oxidizing (burning) unburned fuel, carbon monoxide, nitrogen monoxide, and the like contained in the exhaust gas. The filter 37 is arranged downstream of the oxidation catalyst, and is configured as a fall-flow filter, for example. The filter collects particulate matter contained in the exhaust gas treated with the oxidation catalyst.

The ECU 5 controls driving of the engine 1 . As shown in FIG. 2 , the ECU 5 is connected with an upstream exhaust temperature sensor 56 , a downstream exhaust temperature sensor 57 and an engine speed sensor 58 . Further, an injector solenoid valve 61 and a notification device 62 are connected to the ECU 5 .

The upstream exhaust temperature sensor 56 is installed in a region upstream of the oxidation catalyst 36 in the storage case 35 and detects the temperature of the exhaust gas (exhaust temperature) in this upstream region. The upstream exhaust temperature sensor 56 outputs the detected exhaust gas temperature to the ECU 5 .

The downstream exhaust temperature sensor 57 is installed in a region downstream of the oxidation catalyst 36 in the storage case 35 and detects the exhaust temperature in this downstream region. The downstream exhaust temperature sensor 57 outputs the detected exhaust gas temperature to the ECU 5 .

In the following description, the temperature of the exhaust gas in the region of the storage case 35 upstream of the oxidation catalyst 36 may be referred to as the upstream exhaust temperature. Further, the temperature of the exhaust gas in the area downstream of the oxidation catalyst 36 in the storage case 35 may be referred to as the downstream exhaust temperature.

The engine speed sensor 58 is installed near the crankshaft and detects the engine speed based on the speed of the crankshaft. The engine speed sensor 58 outputs the detected engine speed to the ECU 5 .

The injector solenoid valve 61 is provided in the injector 25 and allows the injector 25 to inject fuel into the combustion chamber 23 . The injector solenoid valve 61 opens and closes according to instructions from the ECU 5 . This opening and closing controls the fuel injection state.

A notification device 62 is attached to the machine using the engine 1 and notifies the operator of various situations requiring attention. A lamp, a buzzer, or the like, for example, is used as the notification device 62 .

ECU5 is demonstrated in detail. The ECU 5 includes a vector calculation section 50 , an index calculation section 51 , a temperature difference calculation section 52 and a determination section 53 .

More specifically, the ECU 5 is configured as a computer including a computing section including a CPU and the like, and a storage section including a ROM, a RAM, and the like. The calculation unit sends control commands to various actuators based on information from various sensors, and controls various parameters for operating the engine 1 (for example, fuel injection amount, air intake amount, etc.). The storage unit stores various programs and a plurality of preset control information regarding control of the engine 1 . The ECU 5 can operate as a vector calculation unit 50, an index calculation unit 51, a temperature difference calculation unit 52, and a determination unit 53 by cooperation of the hardware and software described above.

When the engine 1 is running, the vector calculation unit 50 determines that the upstream side exhaust temperature sensor 56 and the downstream side exhaust temperature sensor 57 are the same when unburned fuel is not supplied to the oxidation catalyst 36 (post injection is not being performed). An upstream temperature change rate vector and a downstream temperature change rate vector are calculated based on the respective temperature changes detected over time.

The upstream temperature change speed vector is obtained based on the change in the upstream exhaust temperature detected by the upstream exhaust temperature sensor 56 over a predetermined period of time. The downstream temperature change speed vector is obtained based on the change in the downstream exhaust temperature detected by the downstream exhaust temperature sensor 57 over a predetermined period of time.

Both the upstream and downstream temperature change rate vectors can be expressed as the sum of a first vector and a second vector that are orthogonal to each other, as shown in FIG. The first vector means the horizontal component of the temperature change rate vector shown in FIG. 3, and its length represents the predetermined time over which the temperature change is measured. Although this predetermined time is arbitrary, it can be set to 1 second, for example. The second vector means the vertical component of the temperature change rate vector, and its length and direction represent the direction and magnitude of the temperature change in the given time. In the example of FIG. 3, if the temperature change is positive, the second vector is upward, and if the temperature change is negative, the second vector is downward. If the temperature change is gradual, the direction of the temperature change speed vector is close to the horizontal direction. If the temperature change is abrupt, the direction of the temperature change rate vector makes a large angle with respect to the horizontal direction.

The index calculator 51 calculates an index I (parameter) based on the angle difference θ between the upstream and downstream temperature change speed vectors obtained by the vector calculator 50 .

Specifically, the index I is obtained by dividing the angular difference θ, expressed in radians, by the pi for normalization, and the upstream and It is obtained by multiplying the absolute value of the difference of the temperature change rates on the downstream side.
I=θ×|difference in temperature change rate between upstream and downstream sides|/π

This index I has the property of increasing as the angular difference θ of the temperature change velocity vector increases. Therefore, the index I substantially represents the strength of the correlation between the upstream side exhaust temperature and the downstream side exhaust temperature. Further, due to the above weighting, even if the angle difference θ is the same, if the temperature change on one of the upstream side and the downstream side is slow to follow the temperature change on the other side, the calculated index value will be It's getting bigger.

FIG. 4 shows the results of comparing the speed of temperature change on the upstream side and the downstream side with and without the oxidation catalyst 36 . When a machine using the engine 1 performs work, the temperature of the exhaust gas fluctuates according to, for example, fluctuations in the load. Therefore, the upstream temperature change rate oscillates between plus and minus with an amplitude depending on the situation.

When the oxidation catalyst 36 is present, as shown in the upper graph of FIG. 4, the temperature change on the downstream side is gentler than the temperature change on the upstream side due to the heat capacity of the catalyst. Therefore, since the angle difference θ between the temperature change velocity vectors on the upstream side and the downstream side increases, the above index I increases. On the other hand, if the oxidation catalyst 36 is removed for some reason, the temperature change on the downstream side well follows the temperature change on the upstream side and fluctuates greatly, as shown in the lower graph of FIG. Therefore, since the angle difference θ between the temperature change velocity vectors on the upstream side and the downstream side becomes smaller, the above index I becomes smaller.

The temperature difference calculator 52 in FIG. 2 calculates the upstream exhaust temperature sensor 56 and the downstream exhaust temperature in a state in which unburned fuel is not supplied to the oxidation catalyst 36 (a state in which post-injection is not performed) during operation of the engine 1 . A temperature difference is calculated from each exhaust temperature detected by the sensor 57 . Specifically, the temperature difference calculator 52 calculates the temperature difference between the exhaust temperature detected by the upstream exhaust temperature sensor 56 and the exhaust temperature detected by the downstream exhaust temperature sensor 57 at the same timing.

FIG. 5 shows the transition of the difference in exhaust gas temperature between the upstream side and the downstream side, comparing the results with and without the oxidation catalyst 36 . When the oxidation catalyst 36 is present, it is difficult for the temperature on the downstream side to follow the temperature change on the upstream side, so a temperature difference is likely to occur as shown in the upper graph of FIG. On the other hand, in the absence of the oxidation catalyst 36, the temperature on the downstream side well follows the temperature on the upstream side and changes, so as shown in the lower graph of FIG. 5, the temperature difference is less likely to occur.

The determination unit 53 in FIG. 2 determines whether the oxidation catalyst 36 is functioning normally. This determination includes determining whether or not the oxidation catalyst 36 is installed in the exhaust passage. If the oxidation catalyst 36 is not installed in the exhaust passage for some reason, the determination unit 53 determines that the oxidation catalyst 36 is not functioning normally.

Specifically, the determination unit 53 compares the index I obtained by the index calculation unit 51 with a predetermined threshold. The determination unit 53 determines that the catalyst is installed if the index I is larger than the threshold, and that the catalyst is not installed if the index I is smaller than the threshold.

Further, the determination unit 53 compares the temperature difference obtained by the temperature difference calculation unit 52 with a predetermined threshold value. The determination unit 53 determines that the oxidation catalyst 36 is installed if the temperature difference is larger than the threshold, and that the oxidation catalyst 36 is not installed if the temperature difference is smaller than the threshold.

Next, the process for determining whether or not the oxidation catalyst 36 is normally installed in the exhaust passage will be described in detail with reference to FIG. FIG. 6 is a flow chart showing a process for determining the installation state of the oxidation catalyst 36. As shown in FIG.

In this embodiment, when the engine 1 is in a normal operating state, the determination unit 53 provided in the ECU 5 performs the first determination and the second determination to determine whether or not the oxidation catalyst 36 is normally installed in the exhaust passage. make a judgment. The control performed by the ECU 5 will be described in detail below with reference to the flowchart of FIG.

The normal operating state is not an idling state, but a state in which the engine speed is equal to or higher than a predetermined speed due to combustion of fuel in the combustion chamber 23 . Both the first determination and the second determination are performed in a state in which unburned fuel is not supplied to the oxidation catalyst 36 (a state in which post-injection is not performed).

The flow shown in FIG. 6 is started at an appropriate timing after the engine 1 is started. When the process starts, the ECU 5 first determines whether or not a predetermined determination condition is satisfied (step S101). This determination condition includes that the engine is in a normal operating state. The operating state of the engine 1 is determined based on the engine speed detected by the engine speed sensor 58 .

Specifically, when the engine speed detected by the engine speed sensor 58 is equal to or higher than a predetermined speed, it is determined that the engine 1 is not in an idling state but in a normal operating state. . When the engine speed is less than the predetermined speed, it is determined that the engine 1 is not in a normal operating state. If the above determination condition is not satisfied, the determination of step S101 is repeated.

In step S101, if the determination condition is satisfied, the ECU 5 acquires the upstream exhaust temperature based on the detection result of the upstream exhaust temperature sensor 56, and the downstream exhaust temperature sensor 57 detects the exhaust temperature. Based on this, the exhaust gas temperature on the downstream side is acquired (step S102).

Next, the vector calculation unit 50 calculates the temperature change speed vector of the exhaust temperature on the upstream side and the temperature change speed vector of the exhaust temperature on the downstream side as described above (step S103).

When the two temperature change rate vectors are obtained, the index calculator 51 calculates the index I according to the above formula using the angular difference θ between the vectors. Based on this index I, the determination unit 53 determines whether or not the oxidation catalyst 36 is normally installed in the exhaust passage (first determination, step S104). Specifically, when the index I is larger than the threshold, it is determined that the oxidation catalyst 36 is normally installed in the exhaust passage. On the other hand, when the index I is equal to or less than the threshold, it is determined that there is a possibility that the oxidation catalyst 36 is not normally installed in the exhaust passage. As the threshold value, an appropriate value may be determined by experiment or the like.

The ECU 5 checks the result of the first determination (step S105). If the oxidation catalyst 36 is normally installed in the exhaust passage, the value of the counter is reset to zero (step S106). The counter relates to conditions for diagnosing the oxidation catalyst 36 with post-injection, which will be described later in detail. After that, the process returns to step S101.

If it is determined in step S105 that there is a possibility that the oxidation catalyst 36 is not normally installed in the exhaust passage, the temperature difference calculator 52 calculates the current upstream exhaust gas temperature and the downstream exhaust gas temperature. Calculate the temperature difference between Based on this temperature difference, the determination unit 53 determines whether or not the oxidation catalyst 36 is normally installed in the exhaust passage (second determination, step S107). Specifically, when the absolute value of the temperature difference is greater than the threshold, it is determined that the oxidation catalyst 36 is normally installed in the exhaust passage. On the other hand, if the absolute value of the temperature difference is equal to or less than the threshold, it is determined that there is a possibility that the oxidation catalyst 36 is not normally installed in the exhaust passage. As the threshold value, an appropriate value may be determined by experiment or the like.

The ECU 5 checks the result of the second determination (step S108). If the oxidation catalyst 36 is normally installed in the exhaust passage, the value of the counter is reset to zero (step S106). After that, the process returns to step S101.

When it is determined in step S108 that there is a possibility that the oxidation catalyst 36 is not normally installed in the exhaust passage, the ECU 5 increases the value of the counter by 1 (step S109). After that, the ECU 5 determines whether or not the value of the counter is equal to or greater than the threshold (step S110). Although this threshold value is arbitrary, for example, assuming that the determination cycle from step S101 to step S110 is repeated once per second, for example, the value of the counter when the determination cycle continues for several hours can be determined. can be done.

If it is determined in step S110 that the value of the counter is equal to or greater than the threshold value, the post-injection diagnosis of the oxidation catalyst 36 is performed (step S111). If the counter value is less than the threshold, the process of step S111 is not performed. In either case, the process returns to step S101.

Diagnosis of the oxidation catalyst 36 by post-injection is well known, but will be briefly described with reference to FIG.

When the subroutine of FIG. 7 is called by step S111 of FIG. 6, the ECU 5 first performs post-injection (step S201). Post-injection means injecting fuel from the injector 25 at a timing after fuel combustion so that unburned fuel is supplied to the oxidation catalyst 36 through the exhaust passage.

Subsequently, the ECU 5 obtains the upstream side exhaust temperature based on the detection result of the upstream side exhaust temperature sensor 56, and obtains the downstream side exhaust temperature based on the detection result of the downstream side exhaust temperature sensor 57 (step S202).

When the temperature information is obtained, the ECU 5 uses the temperature to diagnose the oxidation catalyst 36 (step S203). This diagnosis includes not only deterioration of the oxidation catalyst 36 but also determination of the presence or absence of the oxidation catalyst 36 . In this diagnosis, when it is determined that the oxidation catalyst 36 is not present, the ECU 5 activates the notification device 62 to notify the operator and call attention to it. At this time, in order to prevent deterioration of emissions, the engine 1 may be automatically and forcibly shifted to a limited operation in which the output of the engine 1 is partially limited.

By performing the above control, when the engine 1 is in a normal operating state, it is possible to make the first determination and the second determination regarding whether or not the oxidation catalyst 36 is normally installed. That is, the post-injection is used to make a definitive determination that the oxidation catalyst 36 is not present. Without performing, the determination of the presence or absence of the oxidation catalyst 36 is completed.

In the present embodiment, post-injection is actually performed when the situation in which it is determined that there is no oxidation catalyst 36 in both the first determination and the second determination corresponds to the count threshold value of step S110 (for example, a number of times). time). Therefore, the chances of post-injection can be greatly reduced, so deterioration of fuel consumption and promotion of deterioration of the oxidation catalyst 36 can be prevented.

As described above, the engine 1 of this embodiment includes the oxidation catalyst 36, the upstream side exhaust temperature sensor 56, the downstream side exhaust temperature sensor 57, and the ECU5. The oxidation catalyst 36 is installed in an exhaust passage through which exhaust gas can flow. The upstream exhaust temperature sensor 56 is installed upstream of the oxidation catalyst 36 in the direction of exhaust gas flow, and detects the exhaust temperature. The downstream side exhaust temperature sensor 57 is installed downstream of the oxidation catalyst 36 in the direction in which the exhaust gas flows, and detects the exhaust temperature. The ECU 5 determines the correlation between the exhaust temperature detected by the upstream side exhaust temperature sensor 56 and the exhaust temperature detected by the downstream side exhaust temperature sensor 57 when the oxidation catalyst 36 is not supplied with unburned fuel during engine operation. Based on this, it is determined whether or not the oxidation catalyst 36 is normally installed in the exhaust passage (whether it functions normally).

As a result, when the engine 1 is running, even if unburned fuel is not supplied to the oxidation catalyst 36 (even if post-injection is not performed), the correlation between the upstream side exhaust temperature and the downstream side exhaust temperature with respect to the oxidation catalyst 36 can be obtained. , it can be determined whether or not the oxidation catalyst 36 is normally installed in the exhaust passage. Therefore, it is possible to reduce the number of opportunities for post-injection, thereby preventing deterioration of fuel consumption and acceleration of deterioration of the oxidation catalyst 36 due to post-injection.

Further, in the engine 1 of the present embodiment, the ECU 5 includes a vector calculation section 50 and a determination section 53 . The vector calculator 50 calculates an upstream temperature change speed vector and a downstream temperature change speed vector. The upstream temperature change speed vector is based on the change in the exhaust temperature detected by the upstream exhaust temperature sensor 56 over a predetermined period of time. The downstream temperature change speed vector is based on the change in the exhaust temperature detected by the downstream exhaust temperature sensor 57 over a predetermined period of time. A temperature change rate vector is expressed as the sum of a first vector and a second vector that are orthogonal to each other. The length of the first vector indicates the predetermined time. The direction and length of the second vector indicate the direction and magnitude of change in the exhaust temperature. The determining unit 53 determines whether or not the index I, which increases as the angle (angle difference θ) between the upstream temperature change rate vector and the downstream temperature change rate vector increases, is greater than a predetermined threshold. A first determination is made.

Thus, it is possible to determine whether or not the oxidation catalyst 36 is normally installed based on the change speed of the exhaust gas temperature on the upstream side and the change speed of the exhaust gas temperature on the downstream side.

Moreover, in the engine 1 of this embodiment, the ECU 5 includes a temperature difference calculator 52 . The temperature difference calculator 52 calculates the exhaust temperature detected by the upstream side exhaust temperature sensor 56, the exhaust temperature detected by the downstream side exhaust temperature sensor 57, and the Calculate the temperature difference between The determination unit 53 makes a second determination to determine whether the absolute value of the temperature difference calculated by the temperature difference calculation unit 52 is greater than a predetermined temperature threshold.

Accordingly, it is possible to determine whether or not the oxidation catalyst 36 is normally installed based on the exhaust temperature on the upstream side and the exhaust temperature on the downstream side. In addition, since the relationship between the upstream side exhaust temperature and the downstream side exhaust temperature is comprehensively determined from two different viewpoints, the accuracy of the determination result can be improved.

In the engine 1 of the present embodiment, the ECU 5 detects that the oxidation catalyst 36 is not properly installed in the exhaust passage for a predetermined period of time. 36 is supplied with unburned fuel to diagnose the installation state of the oxidation catalyst 36 (diagnosis of the function of the oxidation catalyst 36).

As a result, the final judgment that the oxidation catalyst 36 is not present (the oxidation catalyst 36 is not functioning normally) is made after the first judgment and the second judgment are made (repeatedly) with temporal continuity. , will be performed using post-injection. Therefore, the chance of post-injection can be reliably reduced. In addition, it is possible to prevent erroneous determination that the oxidation catalyst 36 is not installed even though it is actually installed.

Although the preferred embodiments of the present invention have been described above, the above configuration can be modified, for example, as follows.

In the above embodiment, both the first determination and the second determination are performed to determine whether or not the oxidation catalyst 36 is normally installed in the exhaust passage when the engine 1 is in a normal operating state. However, instead of this, only the first determination may be performed.

The order of the first determination and the second determination is arbitrary. The determination unit 53 may first perform the second determination, and if the second determination does not determine that the oxidation catalyst 36 is normally installed in the exhaust passage, the first determination may be performed.

The determination condition shown in step S101 is not limited to the above, and can be determined as appropriate. For example, the determination condition can be changed to determine the operating state of the engine and the state of the atmospheric pressure.

The exhaust purification device 33 is not limited to the above, and may be configured to further include, for example, an SCR (Selective Catalytic Reduction) device.

The formula for the index I related to the first determination may be changed so as not to consider weighting. Also, normalization may be omitted.

Instead of the index I, the ECU 5 may calculate, for example, a correlation coefficient representing the strength of the correlation between the upstream temperature change rate and the downstream temperature change rate. In this case, the determination unit 53 compares the obtained correlation coefficient with a threshold value, and determines that the oxidation catalyst 36 is normally installed if the correlation coefficient is equal to or less than the threshold value. However, from the viewpoint of simplification of calculation processing, it is preferable to obtain the angle difference θ between the vectors as described above.

A final determination as to whether the oxidation catalyst 36 is normally installed in the exhaust passage may be made based on the result of at least one of the first determination and the second determination without performing the post-injection.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as described herein.

<Additional remarks of the invention>
According to the aspect of the present invention, an engine having the following configuration is provided. Specifically, the engine includes an oxidation catalyst, an upstream exhaust temperature sensor, a downstream exhaust temperature sensor, and a control device. The oxidation catalyst is installed in an exhaust passage through which exhaust gas can flow. The upstream exhaust temperature sensor is installed upstream of the oxidation catalyst in the direction in which the exhaust gas flows, and detects the exhaust temperature. The downstream exhaust temperature sensor is installed downstream of the oxidation catalyst in the direction in which the exhaust gas flows, and detects the exhaust temperature. The control device correlates the exhaust temperature detected by the upstream side exhaust temperature sensor and the exhaust temperature detected by the downstream side exhaust temperature sensor in a state where unburned fuel is not supplied to the oxidation catalyst during engine operation. Based on the relationship, it is determined whether the oxidation catalyst is functioning normally.

As a result, when the engine is running, even if unburned fuel is not supplied to the oxidation catalyst (even if post-injection is not performed), it is possible to reduce the can be used to determine whether the oxidation catalyst is functioning normally. Therefore, it is possible to reduce the number of opportunities for post-injection, so that it is possible to prevent deterioration of fuel consumption and promotion of deterioration of the oxidation catalyst due to post-injection.

The engine described above preferably has the following configuration. That is, the control device includes a vector calculation section and a determination section. The vector calculator calculates an upstream temperature change speed vector and a downstream temperature change speed vector. The upstream temperature change speed vector is based on a change in the exhaust temperature detected by the upstream exhaust temperature sensor over a predetermined period of time. The downstream temperature change speed vector is based on the change in the exhaust temperature detected by the downstream exhaust temperature sensor over a predetermined period of time. The temperature change rate vector is expressed as the sum of a first vector and a second vector that are orthogonal to each other. The length of the first vector indicates the predetermined time. The direction and length of the second vector indicate the direction and magnitude of change in the exhaust temperature. The determination unit determines whether or not a parameter that increases as an angle between the upstream temperature change rate vector and the downstream temperature change rate vector increases is greater than a predetermined threshold. make a judgment.

Accordingly, it is possible to determine whether the oxidation catalyst is functioning normally based on the change speed of the exhaust gas temperature on the upstream side and the change speed of the exhaust gas temperature on the downstream side.

The engine described above preferably has the following configuration. That is, the control device includes a temperature difference calculator. The temperature difference calculation unit calculates the exhaust temperature detected by the upstream side exhaust temperature sensor, the exhaust temperature detected by the downstream side exhaust temperature sensor, and Calculate the temperature difference between The determination section performs a second determination to determine whether or not the absolute value of the temperature difference calculated by the temperature difference calculation section is greater than a predetermined temperature threshold.

Accordingly, it is possible to determine whether the oxidation catalyst is functioning normally based on the exhaust temperature on the upstream side and the exhaust temperature on the downstream side. In addition, since the relationship between the upstream side exhaust temperature and the downstream side exhaust temperature is comprehensively determined from two different viewpoints, the accuracy of the determination result can be improved.

In the above-described engine, the control device controls the oxidation catalyst when a state in which neither the first determination nor the second determination indicates that the oxidation catalyst is functioning normally continues for a predetermined period of time. It is preferable to diagnose the function of the oxidation catalyst by supplying unburned fuel to the .

As a result, the final determination that the oxidation catalyst is not functioning normally is made using the post-injection after the first determination and the second determination are made with temporal continuity. Therefore, the chance of post-injection can be reliably reduced. In addition, it is possible to prevent erroneous determination that the oxidation catalyst is not functioning normally when it actually functions normally.

1 engine 5 ECU (control device)
36 oxidation catalyst 50 vector calculator 52 temperature difference calculator 53 determination unit 56 upstream exhaust temperature sensor 57 downstream exhaust temperature sensor θ angle difference (angle)

Claims (3)

an oxidation catalyst installed in an exhaust passage through which exhaust gas can flow;
The temperature of the exhaust gas upstream of the oxidation catalyst in the direction of exhaust gas flow and the temperature of the exhaust gas downstream of the oxidation catalyst in the direction of exhaust gas flow when the engine is running and no post-injection is performed. a temperature difference calculator that calculates the difference;
Determination [1] for determining whether or not the oxidation catalyst is functioning normally by determining whether or not the absolute value of the temperature difference calculated by the temperature difference calculation unit is greater than a predetermined temperature threshold. ] and a determination unit for performing
engine. an oxidation catalyst installed in an exhaust passage through which exhaust gas can flow;
During engine operation, a temperature difference calculation unit for calculating a temperature difference between an exhaust temperature upstream of the oxidation catalyst in the direction of exhaust gas flow and an exhaust temperature downstream of the oxidation catalyst in the direction of exhaust gas flow. and,
Determination [1] for determining whether or not the oxidation catalyst is functioning normally by determining whether or not the absolute value of the temperature difference calculated by the temperature difference calculation unit is greater than a predetermined temperature threshold. ] and a determination unit for performing
The determination unit
A temperature change speed vector on the upstream side based on a change in exhaust gas temperature on the upstream side of the oxidation catalyst in the direction of exhaust gas flow over a predetermined period of time, and an exhaust gas temperature on the downstream side of the oxidation catalyst in the direction of exhaust gas flow. By determining whether or not a parameter that increases as the angle formed by the downstream temperature change rate vector based on the change in the predetermined time increases is greater than a predetermined threshold value, the oxidation catalyst normally operates. perform determination [2] to determine whether it is functioning;
engine . The determination unit determines that, when a state in which neither the determination [1] nor the determination [2] determines that the oxidation catalyst is functioning normally continues for a predetermined period of time, to diagnose the functioning of the oxidation catalyst;
3. An engine according to claim 2.

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