CN113242931A

CN113242931A - Engine

Info

Publication number: CN113242931A
Application number: CN202080007163.6A
Authority: CN
Inventors: 垣地佑树
Original assignee: Yanmar Power Technology Co Ltd
Current assignee: Yanmar Power Technology Co Ltd
Priority date: 2019-03-28
Filing date: 2020-02-10
Publication date: 2021-08-10
Also published as: JP7083083B2; WO2020195249A1; JP2020165333A

Abstract

The engine is provided with an oxidation catalyst, an upstream-side exhaust gas temperature sensor, a downstream-side exhaust gas temperature sensor, and an ECU. The oxidation catalyst is provided in an exhaust passage through which exhaust gas can flow. The upstream-side exhaust gas temperature sensor is provided upstream of the oxidation catalyst in the direction in which the exhaust gas flows, and detects the exhaust gas temperature. The downstream-side exhaust gas temperature sensor is provided downstream of the oxidation catalyst in the direction in which the exhaust gas flows, and detects the exhaust gas temperature. The ECU determines whether or not the oxidation catalyst functions normally based on a correlation between the exhaust gas temperature detected by the upstream-side exhaust gas temperature sensor and the exhaust gas temperature detected by the downstream-side exhaust gas temperature sensor in a state where unburned fuel is not supplied to the oxidation catalyst during operation of the engine.

Description

Engine

Technical Field

The present invention relates to an engine. More specifically, the present invention relates to a structure in which an oxidation catalyst is provided in an exhaust passage of an engine.

Background

Conventionally, an engine provided with an oxidation catalyst in an exhaust passage is known. Patent document 1 discloses such an engine.

The structure of patent document 1 includes: the exhaust gas temperature sensor includes an oxidation catalyst provided in an exhaust pipe, a first exhaust gas temperature sensor provided in the exhaust pipe on an upstream side of the oxidation catalyst, and a second exhaust gas temperature sensor provided in the exhaust pipe on a downstream side of the oxidation catalyst. After the post injection is executed, a determination is made as to whether the oxidation catalyst is abnormal, that is, deteriorated, based on the upstream exhaust gas temperature detected by the first exhaust gas temperature sensor and the downstream exhaust gas temperature detected by the second exhaust gas temperature sensor.

Patent document 1: japanese patent application laid-open No. 2010-203238

In the structure of patent document 1, post injection is required to determine abnormality of the oxidation catalyst. However, since the post injection causes deterioration in fuel consumption and deterioration of the oxidation catalyst, it is desirable to suppress the number of times.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine capable of determining whether or not an oxidation catalyst is functioning normally, even if post-injection is not performed, that is, even if unburned fuel is not supplied to the oxidation catalyst.

The problems to be solved by the present invention are as described above, and means for solving the problems and effects thereof will be described below.

According to an aspect of the present invention, an engine having the following structure is provided. That is, the engine includes an oxidation catalyst, an upstream-side exhaust gas temperature sensor, a downstream-side exhaust gas temperature sensor, and a control device. The oxidation catalyst is provided in an exhaust passage through which exhaust gas can flow. The upstream-side exhaust gas temperature sensor is provided upstream of the oxidation catalyst in the exhaust gas flow direction, and detects the exhaust gas temperature. The downstream-side exhaust gas temperature sensor is provided downstream of the oxidation catalyst in a direction in which the exhaust gas flows, and detects an exhaust gas temperature. The control device determines whether or not the oxidation catalyst functions normally based on a correlation between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor in a state where unburned fuel is not supplied to the oxidation catalyst during engine operation.

Thus, even if unburned fuel is not supplied to the oxidation catalyst during engine operation (even if post-injection is not performed), it is possible to determine whether or not the oxidation catalyst is functioning properly based on the correlation between the exhaust gas temperature on the upstream side and the exhaust gas temperature on the downstream side with respect to the oxidation catalyst. This can reduce the chance of post injection, and therefore can prevent the deterioration of fuel efficiency and the acceleration of the deterioration of the oxidation catalyst due to post injection.

In the engine described above, the following configuration is preferably provided. That is, the control device includes a vector calculation unit and a determination unit. The vector calculation unit calculates an upstream temperature change velocity vector and a downstream temperature change velocity vector. The upstream-side temperature change speed vector is based on a change in the exhaust temperature detected by the upstream-side exhaust temperature sensor over a predetermined time period. The downstream-side temperature change speed vector is based on a change in the exhaust temperature detected by the downstream-side exhaust temperature sensor over a predetermined time period. The temperature change speed vector is expressed as a 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 the change in the exhaust temperature. The determination unit performs a first determination as to whether or not a parameter that increases as an angle formed by the upstream temperature change velocity vector and the downstream temperature change velocity vector increases is larger than a predetermined threshold value.

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

In the engine described above, the following configuration is preferably provided. That is, the control device includes a temperature difference calculation unit. The temperature difference calculation unit calculates a temperature difference between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor, during engine operation, without supplying unburned fuel to the oxidation catalyst. The determination unit performs a second determination as to whether or not the absolute value of the temperature difference calculated by the temperature difference calculation unit is greater than a predetermined temperature threshold.

Thus, it is possible to determine whether or not the oxidation catalyst functions normally based on the upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature. Further, since the relationship between the upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature is comprehensively determined from two different viewpoints, the accuracy of the determination result can be improved.

In the engine described above, it is preferable that the control device supply unburned fuel to the oxidation catalyst and diagnose the function of the oxidation catalyst when a state in which it is not determined by the first determination or the second determination that the oxidation catalyst functions normally continues for a predetermined time.

Thus, after the first determination and the second determination are made with temporal continuity, the final determination that the oxidation catalyst is not functioning properly is made by the post injection. Therefore, the chance of post injection can be reliably reduced. Further, it is possible to prevent the oxidation catalyst from functioning normally in actuality but erroneously determined not to function normally.

Drawings

Fig. 1 is a diagram showing an overall configuration of an engine according to an embodiment of the present invention.

Fig. 2 is a block diagram showing the main electrical structure of the engine.

Fig. 3 is a diagram showing a relationship between a temperature change velocity vector relating to a detection result of the upstream-side exhaust gas temperature sensor and a temperature change velocity vector relating to a detection result of the downstream-side exhaust gas temperature.

Fig. 4 is a graph showing the progress of the temperature change rate on the upstream side and the downstream side in comparison between the case where the catalyst is present and the case where the catalyst is absent.

Fig. 5 is a graph showing the progress of the temperature difference between the upstream side and the downstream side in the case where the catalyst is present and in the case where the catalyst is absent.

Fig. 6 is a flowchart showing a process of determining the presence or absence of an oxidation catalyst.

Fig. 7 is a flowchart showing a subroutine for diagnosing the oxidation catalyst by the post injection.

Detailed Description

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

As shown in fig. 1, an engine 1 includes: an intake portion 2, a power generation portion 3, an exhaust portion 4, and an ECU5 as a control device.

The intake portion 2 takes in air from the outside. The intake unit 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 described later via an intake manifold 12, and can flow air taken in from the outside.

The intake manifold 12 is connected to a downstream-side end portion of the intake pipe 11 in a direction in which intake air flows in the intake passage. The intake manifold 12 distributes the air supplied via the intake pipe 11 in accordance with the number of cylinders of the power generation portion 3. The distributed air is supplied to the combustion chamber 23 formed in each cylinder.

The throttle valve 13 is disposed in the middle of the intake passage. The throttle valve 13 changes its opening degree in accordance with a control command from the ECU5, thereby changing the cross-sectional area of the intake passage. This enables adjustment of the amount of air supplied to the intake manifold 12.

The power generation unit 3 includes a cylinder and a cylinder head 21. A piston, a crankshaft, and the like are disposed inside the cylinder block. A plurality of (four in the present embodiment) cylinders 22 are formed in the upper portion of the cylinder block.

A cylinder head 21 is disposed above the cylinder block. The cylinder head 21 and the cylinder block are provided with an intake manifold 12 corresponding to each cylinder 22. An injector 25 or the like for injecting fuel into the intake manifold 12 is mounted on the cylinder head 21.

In each combustion chamber 23, air from the intake manifold 12 is compressed, and then fuel supplied from a fuel supply unit, not shown, is injected by an injector 25. This allows fuel to be combusted in the intake manifold 12, and the piston to reciprocate up and down. The power thus obtained is transmitted to an appropriate device on the downstream side of the power via a crankshaft and the like.

The supercharger 14 includes a turbine 27, a shaft 28, and a compressor 29. The compressor 29 is coupled to the turbine 27 via a shaft 28. In this configuration, when the turbine 27 is rotated by the flow of the exhaust gas discharged from the combustion chamber 23, the compressor 29 is rotated. This makes it possible to compress and forcibly suck air purified by an air purifier, not shown.

The exhaust unit 4 discharges the exhaust gas generated in the combustion chamber 23 to the outside. The exhaust unit 4 includes an exhaust pipe 31, an exhaust manifold 32, and an exhaust gas 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 can flow the exhaust gas discharged from the combustion chamber 23.

The exhaust manifold 32 is connected to an upstream-side end portion of the exhaust pipe 31 in the direction in which exhaust gas flows. The exhaust manifold 32 collects exhaust gas generated in each combustion chamber 23 and guides the collected exhaust gas to the exhaust pipe 31.

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

The exhaust gas purification device 33 is disposed in the middle of the exhaust passage. The exhaust gas purification device 33 includes a housing case 35, an oxidation catalyst 36, and a filter 37. The housing case 35 can introduce exhaust gas into the inside and send 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 disposed upstream of the filter 37 in the housing case 35. In this way, the exhaust gas purification apparatus 33 introduces the exhaust gas discharged from the combustion chamber 23 into the housing case 35, and removes carbon monoxide, nitrogen monoxide, particulate matter, and the like contained in the exhaust gas through the oxidation catalyst 36 and the filter 37.

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

The ECU5 controls driving of the engine 1. As shown in fig. 2, the ECU5 is connected with an upstream-side exhaust gas temperature sensor 56, a downstream-side exhaust gas temperature sensor 57, and an engine speed sensor 58. The injector solenoid valve 61 and the notification device 62 are connected to the ECU 5.

The upstream-side exhaust gas temperature sensor 56 is provided in a region on the upstream side of the oxidation catalyst 36 in the housing case 35, and detects the temperature of the exhaust gas (exhaust gas temperature) in the region on the upstream side. The upstream-side exhaust gas temperature sensor 56 outputs the detected temperature of the exhaust gas to the ECU 5.

The downstream-side exhaust gas temperature sensor 57 is provided in a region on the downstream side of the oxidation catalyst 36 in the housing case 35, and detects the exhaust gas temperature in the region on the downstream side. The downstream-side exhaust gas temperature sensor 57 outputs the detected temperature of the exhaust gas to the ECU 5.

In the following description, the temperature of the exhaust gas in the region upstream of the oxidation catalyst 36 in the housing case 35 may be referred to as an upstream exhaust gas temperature. Further, the temperature of the exhaust gas in a region on the downstream side of the oxidation catalyst 36 in the housing case 35 may be referred to as the exhaust gas temperature on the downstream side.

The engine speed sensor 58 is provided near the crankshaft, and detects the engine speed based on the crankshaft speed. 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 can cause the injector 25 to inject fuel into the combustion chamber 23. The injector solenoid valve 61 is opened and closed in accordance with an instruction from the ECU 5. The opening and closing controls the fuel injection state.

The notification device 62 is attached to a machine using the engine 1 and notifies an operator of various conditions to be noted. As the notification device 62, for example, a lamp, a buzzer, or the like can be used.

The ECU5 will be described in detail. The ECU5 includes a vector calculation unit 50, an index calculation unit 51, a temperature difference calculation unit 52, and a determination unit 53.

Specifically, the ECU5 is configured as a computer including an arithmetic unit configured by a CPU or the like and a storage unit configured by a ROM, a RAM, or the like. The arithmetic unit sends control commands to various actuators based on information from various sensors to control various parameters (for example, a fuel injection amount, an air intake amount, and the like) for operating the engine 1. The storage portion stores various programs, and stores a plurality of pieces of control information set in advance regarding control of the engine 1. The ECU5 can operate as the vector calculation unit 50, the index calculation unit 51, the temperature difference calculation unit 52, and the determination unit 53 by the cooperation of the hardware and software described above.

The vector calculation unit 50 calculates the upstream temperature change rate vector and the downstream temperature change rate vector based on changes in the respective temperatures detected by the upstream exhaust gas temperature sensor 56 and the downstream exhaust gas temperature sensor 57 at the same time when the engine 1 is operating, in a state where unburned fuel is not supplied to the oxidation catalyst 36 (a state where post injection is not performed).

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

The temperature change velocity vectors on the upstream side and the downstream side can be expressed as the sum of a first vector and a second vector that are orthogonal to each other, as shown in fig. 3. The first vector means a horizontal component of the temperature change speed vector shown in fig. 3, and the length thereof indicates a predetermined time for measuring a change in temperature. The predetermined time is arbitrary, and can be, for example, 1 second. The second vector means a component in the vertical direction of the temperature change velocity vector, and the length and the direction thereof indicate the direction and magnitude of the temperature change within the predetermined time. In the example of fig. 3, the second vector faces upward when the temperature change is positive, and faces downward when the temperature change is negative. If the temperature change is gradual, the direction of the temperature change speed vector approaches the horizontal direction. If the temperature change is rapid, the direction of the temperature change velocity vector makes a large angle with the horizontal direction.

The index calculation unit 51 calculates an index I (parameter) based on the angular difference θ between the upstream and downstream temperature change velocity vectors obtained by the vector calculation unit 50.

Specifically, the index I can be obtained by dividing the angular difference θ expressed in units of radians by the circumferential ratio for normalization and multiplying the absolute value of the difference between the temperature change rates on the upstream side and the downstream side by the value of the circumferential ratio for weighting, as shown in the following equation.

I is θ × | difference in temperature change speed between the upstream side and the downstream side |/pi

The index I has a property of becoming larger as the angle difference θ of the temperature change velocity vector is larger. Therefore, the index I actually indicates the strength of the correlation between the exhaust gas temperature on the upstream side and the exhaust gas temperature on the downstream side. Further, even with the same angular difference θ, the calculated index value increases when the temperature change on one of the upstream side and the downstream side follows the temperature change on the other side relatively slowly by the above-described weighting.

In fig. 4, the results of comparing the case where the oxidation catalyst 36 is present with the case where the oxidation catalyst 36 is absent are shown with respect to the temperature change rates on the upstream side and the downstream side. When the machine using the engine 1 performs work, for example, the temperature of the exhaust gas fluctuates in accordance with the fluctuation of the load. Therefore, the temperature change speed on the upstream side oscillates between positive and negative with an amplitude corresponding to the situation.

In the case of the oxidation catalyst 36, as shown in the upper graph of fig. 4, since there is a heat capacity of the catalyst, the temperature change on the downstream side becomes slower than the temperature change on the upstream side. Therefore, the angle difference θ between the upstream-side and downstream-side temperature change velocity vectors becomes large, and therefore the index I described above becomes large. On the other hand, if the oxidation catalyst 36 is removed for some reason, as shown in the lower graph of fig. 4, the temperature change on the downstream side favorably follows the temperature change on the upstream side and largely varies. Therefore, the index I described above becomes small because the angular difference θ between the upstream-side and downstream-side temperature change velocity vectors becomes small.

The temperature difference calculation unit 52 in fig. 2 calculates the temperature difference from the exhaust gas temperatures detected by the upstream exhaust gas temperature sensor 56 and the downstream exhaust gas temperature sensor 57 when the engine 1 is operating, in a state where unburned fuel is not supplied to the oxidation catalyst 36 (a state where post injection is not performed). Specifically, the temperature difference calculation unit 52 calculates a temperature difference between the exhaust gas temperature detected by the upstream exhaust gas temperature sensor 56 and the exhaust gas temperature detected by the downstream exhaust gas temperature sensor 57 at the same timing.

In fig. 5, the development of the difference between the exhaust gas temperatures on the upstream side and the downstream side shows the result of comparing the case where there is the oxidation catalyst 36 with the case where there is no oxidation catalyst 36. In the case of the oxidation catalyst 36, since the temperature on the downstream side does not easily follow the temperature change on the upstream side, a temperature difference is likely to occur as shown in the upper graph of fig. 5. On the other hand, in the case where the oxidation catalyst 36 is not provided, since the temperature on the downstream side changes well following the temperature on the upstream side, as shown in the lower graph of fig. 5, a temperature difference is less likely to occur.

The determination unit 53 in fig. 2 determines whether or not the oxidation catalyst 36 functions normally. The determination includes a determination as to whether or not the oxidation catalyst 36 is provided in the exhaust passage. When the oxidation catalyst 36 is not provided in the exhaust passage for some reason, the determination unit 53 determines that the oxidation catalyst 36 does not function normally.

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

The determination unit 53 compares the temperature difference obtained by the temperature difference calculation unit 52 with a predetermined threshold value. If the temperature difference is greater than the threshold value, the determination unit 53 determines that the oxidation catalyst 36 is provided, and if the temperature difference is less than the threshold value, the determination unit 53 determines that the oxidation catalyst 36 is not provided.

Next, the process for determining whether or not the oxidation catalyst 36 is normally provided in the exhaust passage will be described in detail with reference to fig. 6. Fig. 6 is a flowchart showing a process for determining the installation state of the oxidation catalyst 36.

In the present embodiment, when the engine 1 is in the normal operating state, the determination unit 53 provided in the ECU5 performs the first determination and the second determination in order to determine whether or not the oxidation catalyst 36 is normally disposed in the exhaust passage. The control performed by the ECU5 will be described in detail below with reference to the flowchart of fig. 6.

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 by combustion of fuel in the combustion chamber 23. Both the first determination and the second determination are performed in a state where unburned fuel is not supplied to the oxidation catalyst 36 (a state where post injection is not performed).

The flow shown in fig. 6 starts at an appropriate timing after the engine 1 is started. When the process is started, the ECU5 first determines whether or not a predetermined determination condition is satisfied (step S101). The determination condition includes a case where the engine is in a normal operation 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 the idling state but in the normal operation state. When the engine speed is less than the predetermined speed, it is determined that the engine 1 is not in the normal operating state. When the above determination condition is not satisfied, the determination in step S101 is repeated.

In the case where the determination condition is satisfied in the determination of step S101, the ECU5 acquires the upstream-side exhaust gas temperature based on the detection result of the upstream-side exhaust gas temperature sensor 56, and acquires the downstream-side exhaust gas temperature based on the detection result of the downstream-side exhaust gas temperature sensor 57 (step S102).

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

When two temperature change velocity vectors are obtained, the index calculation unit 51 calculates the index I from the above equation using the angle difference θ between the vectors. Based on the index I, the determination unit 53 determines whether or not the oxidation catalyst 36 is normally disposed in the exhaust passage (first determination, step S104). Specifically, when the index I is larger than the threshold value, it is determined that the oxidation catalyst 36 is normally provided in the exhaust passage. On the other hand, when the index I is equal to or less than the threshold value, it is determined that there is a possibility that the oxidation catalyst 36 is not normally provided in the exhaust passage. The threshold value may be determined by an experiment or the like as appropriate.

The ECU5 checks the result of the first determination described above (step S105). If the oxidation catalyst 36 is normally provided in the exhaust passage, the value of the counter is reset to zero (step S106). The counter is related to conditions for diagnosis of the oxidation catalyst 36 accompanying the after-injection described later, and details thereof will be described later. After that, the process returns to step S101.

When it is determined in the determination of step S105 that there is a possibility that the oxidation catalyst 36 is not normally provided in the exhaust passage, the temperature difference calculation unit 52 calculates the temperature difference between the current upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature. The determination unit 53 determines whether or not the oxidation catalyst 36 is normally disposed in the exhaust passage based on the temperature difference (second determination, step S107). Specifically, when the absolute value of the temperature difference is larger than the threshold value, it is determined that the oxidation catalyst 36 is normally provided in the exhaust passage. On the other hand, when the absolute value of the temperature difference is equal to or less than the threshold value, it is determined that there is a possibility that the oxidation catalyst 36 is not normally provided in the exhaust passage. The threshold value may be determined by an experiment or the like as appropriate.

The ECU5 checks the result of the above-described second determination (step S108). If the oxidation catalyst 36 is normally provided in the exhaust passage, the value of the counter is reset to zero (step S106). After that, the process returns to step S101.

If it is determined in the determination of step S108 that there is a possibility that the oxidation catalyst 36 is not normally provided in the exhaust passage, the ECU5 increments the value of the counter by 1 (step S109). After that, the ECU5 determines whether or not the value of the counter is equal to or greater than a threshold value (step S110). The threshold value is arbitrary, and for example, the value of the counter in the case where the determination period continues for about several hours can be determined supposedly by repeating the determination period from step S101 to step S110 once in 1 second.

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

The diagnosis of the oxidation catalyst 36 by the post injection is well known, but is briefly described with reference to fig. 7.

When the subroutine of fig. 7 is called up in step S111 of fig. 6, the ECU5 first performs post injection (step S201). The post injection means that fuel is injected from the injector 25 at the timing after the fuel is combusted so that unburned fuel is supplied to the oxidation catalyst 36 via the exhaust passage.

Next, the ECU5 acquires the upstream-side exhaust gas temperature based on the detection result of the upstream-side exhaust gas temperature sensor 56, and acquires the downstream-side exhaust gas temperature based on the detection result of the downstream-side exhaust gas temperature sensor 57 (step S202).

If the information of the temperature is obtained, the ECU5 uses the temperature to perform diagnosis regarding the oxidation catalyst 36 (step S203). The diagnosis includes determination of the presence or absence of the oxidation catalyst 36 in addition to deterioration of the oxidation catalyst 36 and the like. In this diagnosis, if it is determined that the oxidation catalyst 36 is not present, the ECU5 operates the notification device 62 to notify the operator of the presence of the oxidation catalyst, thereby prompting the operator to pay attention to the presence of the oxidation catalyst. At this time, in order to prevent deterioration of the emission, the limited operation for partially limiting the output of the engine 1 may be automatically and forcibly shifted.

By performing the above control, the first determination and the second determination can be made as to whether or not the oxidation catalyst 36 is normally installed when the engine 1 is in the normal operating state. That is, although the presence of the oxidation catalyst 36 is accurately determined by the post injection, if the presence of the oxidation catalyst 36 can be confirmed by the first determination and the second determination before the accurate determination, the presence of the oxidation catalyst 36 is determined without performing the post injection.

In the present embodiment, the actual post-injection is a case where it is determined that the absence of the oxidation catalyst 36 continues for a time (for example, several hours) corresponding to the count threshold value in step S110 in both the first determination and the second determination. Therefore, the opportunity of the post injection can be greatly reduced, and therefore, the fuel efficiency can be prevented from being deteriorated and the oxidation catalyst 36 can be prevented from being deteriorated.

As described above, the engine 1 of the present embodiment includes the oxidation catalyst 36, the upstream-side exhaust gas temperature sensor 56, the downstream-side exhaust gas temperature sensor 57, and the ECU 5. The oxidation catalyst 36 is provided in an exhaust passage through which exhaust gas can flow. The upstream-side exhaust gas temperature sensor 56 is provided upstream of the oxidation catalyst 36 in the exhaust gas flow direction, and detects the exhaust gas temperature. The downstream-side exhaust gas temperature sensor 57 is provided on the downstream side of the oxidation catalyst 36 in the exhaust gas flow direction, and detects the exhaust gas temperature. The ECU5 determines whether or not the oxidation catalyst 36 is normally disposed in the exhaust passage (normally functions) based on the correlation between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor 56 and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor 57 in a state where unburned fuel is not supplied to the oxidation catalyst 36 during engine operation.

Thus, even if unburned fuel is not supplied to the oxidation catalyst 36 (even if post injection is not performed) during operation of the engine 1, it is possible to determine whether or not the oxidation catalyst 36 is normally disposed in the exhaust passage based on the correlation between the exhaust gas temperature on the upstream side and the exhaust gas temperature on the downstream side with respect to the oxidation catalyst 36. Therefore, the chance of the post injection can be reduced, and thus deterioration of fuel efficiency and promotion of deterioration of the oxidation catalyst 36 due to the post injection can be prevented.

In the engine 1 of the present embodiment, the ECU5 includes the vector calculation unit 50 and the determination unit 53. The vector calculation unit 50 calculates the upstream temperature change velocity vector and the downstream temperature change velocity vector. The upstream-side temperature change speed vector is based on a change in the exhaust temperature detected by the upstream-side exhaust temperature sensor 56 over a predetermined time period. The downstream-side temperature change speed vector is based on a change in the exhaust temperature detected by the downstream-side exhaust temperature sensor 57 over a predetermined time period. The temperature change speed vector is expressed as the sum of a first vector and a second vector which are orthogonal to each other. The length of the first vector represents a prescribed time. The direction and length of the second vector indicate the direction and magnitude of the change in exhaust temperature. The determination unit 53 performs a first determination as to whether or not the index I, which increases as the angle (angle difference θ) between the upstream temperature change velocity vector and the downstream temperature change velocity vector increases, is larger than a predetermined threshold value.

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

In the engine 1 of the present embodiment, the ECU5 includes the temperature difference calculation unit 52. The temperature difference calculation unit 52 calculates the temperature difference between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor 56 and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor 57 during engine operation, without supplying unburned fuel to the oxidation catalyst 36. The determination unit 53 performs a second determination as to whether or not the absolute value of the temperature difference calculated by the temperature difference calculation unit 52 is larger than a predetermined temperature threshold.

Thus, it is possible to determine whether or not the oxidation catalyst 36 is normally provided based on the upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature. Further, since the relationship between the upstream-side exhaust gas temperature and the downstream-side exhaust gas 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 ECU5 supplies unburned fuel to the oxidation catalyst 36 to perform a diagnosis regarding the installation state of the oxidation catalyst 36 (a diagnosis regarding the function of the oxidation catalyst 36) when it is not determined by either the first determination or the second determination that the state in which the oxidation catalyst 36 is normally installed in the exhaust passage continues for a predetermined time.

Thus, after the first determination and the second determination are made continuously (repeatedly) over time, the final determination is made that the oxidation catalyst 36 is not present (the oxidation catalyst 36 does not function normally) by the post injection. Therefore, the chance of post injection can be reliably reduced. In addition, it is possible to prevent the oxidation catalyst 36 from being actually set but erroneously determined not to be set.

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

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

The order of the first determination and the second determination is arbitrary. The determination unit 53 may perform the second determination first, and perform the first determination when it is not determined that the oxidation catalyst 36 is normally provided in the exhaust passage by the second determination.

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

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

The formula of the index I relating to the first determination may be changed without considering the weighting. In addition, normalization may also be omitted.

Instead of the index I, the ECU5 may calculate a correlation coefficient indicating the strength of the correlation between the temperature change rate on the upstream side and the temperature change rate on the downstream side, for example. 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 the calculation process, it is preferable to obtain the angular difference θ of the vectors as described above.

The final determination as to whether or not the oxidation catalyst 36 is normally provided 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 after injection.

It is clear that many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that the present invention can be practiced by methods other than those described in the present specification within the scope of the claims.

Description of the reference numerals

1 … engine; 5 … ECU (control device); 36 … an oxidation catalyst; a 50 … vector calculation unit; 52 … temperature difference calculating part; a 53 … determination unit; 56 … upstream side exhaust gas temperature sensor; a downstream side exhaust gas temperature sensor 57 …; θ … angle difference (angle).

Claims

1. An engine, characterized by comprising:

an oxidation catalyst provided in an exhaust passage through which exhaust gas can flow;

an upstream-side exhaust gas temperature sensor that is provided upstream of the oxidation catalyst in a direction in which exhaust gas flows and that detects an exhaust gas temperature;

a downstream-side exhaust gas temperature sensor that is provided downstream of the oxidation catalyst in a direction in which exhaust gas flows and that detects an exhaust gas temperature; and

and a control device that determines whether or not the oxidation catalyst functions normally based on a correlation between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor in a state where unburned fuel is not supplied to the oxidation catalyst during engine operation.

2. The engine of claim 1,

the control device comprises a vector calculation unit and a determination unit,

the vector calculation unit calculates an upstream temperature change rate vector based on a change in the exhaust temperature detected by the upstream exhaust temperature sensor within a predetermined time and a downstream temperature change rate vector based on a change in the exhaust temperature detected by the downstream exhaust temperature sensor within a predetermined time,

the temperature change speed vector is expressed as a sum of a first vector and a second vector which are orthogonal to each other,

the length of the first vector represents the prescribed time,

the orientation and length of the second vector represent the orientation and magnitude of the change in exhaust temperature,

the determination unit performs a first determination as to whether or not a parameter that increases as an angle formed by the upstream temperature change velocity vector and the downstream temperature change velocity vector increases is larger than a predetermined threshold value.

3. The engine of claim 2,

the control device is provided with a temperature difference calculation part,

the temperature difference calculation unit calculates a temperature difference between the exhaust gas temperature detected by the upstream side exhaust gas temperature sensor and the exhaust gas temperature detected by the downstream side exhaust gas temperature sensor in a state where unburned fuel is not supplied to the oxidation catalyst during engine operation,

the determination unit performs a second determination as to whether or not the absolute value of the temperature difference calculated by the temperature difference calculation unit is greater than a predetermined temperature threshold.

4. The engine of claim 3,

the control device supplies unburned fuel to the oxidation catalyst and diagnoses the function of the oxidation catalyst when a state in which it is not determined whether the oxidation catalyst functions normally by the first determination or the second determination continues for a predetermined time.