JP2021161871A - EGR system - Google Patents

Abstract

To raise a temperature of at least one inner wall of an intake passage and an EGR passage in which an EGR gas flows with favorable responsiveness, to stably maintain the temperature, and to diagnose the lowering of a function of a heat generation membrane for use in heating as a failure without depending on a warmup state of an engine at proper timing.SOLUTION: An EGR system makes a part of exhaust emission discharged to an exhaust passage 3 from an engine 1 flow to an intake passage 2 as an EGR gas via an EGR passage 12, and makes it recirculate to the engine 1. In the EGR system, heat generation membranes 29, 30 are arranged at least at one inner wall of the intake passage 2 and EGR passages 12, 15 in which the EGR gas flows, and at least a pair of positive electrodes 31, 33 and negative electrodes 32, 34 for carrying electricity to the heat generation membranes 29, 30 are arranged. A failure diagnosis device includes current sensors 78A, 78B for detecting current values at electricity-carrying to the heat generation membranes 29, 30, and an electronic control device (ECU) 80 for determining that failures occur in the heat generation membranes 29, 30 when the detected current values reach a prescribed value or lower.SELECTED DRAWING: Figure 1

Description

The technology disclosed in this specification is an EGR system configured to flow a part of the exhaust gas discharged from the engine to the exhaust passage as EGR gas to the intake passage through the EGR passage and return it to the engine. The present invention relates to an EGR system having a failure diagnosis function.

Conventionally, as this kind of technology, for example, the technology described in Patent Document 1 below (“intake manifold”) is known. In this technique, in the intake manifold, a gas distribution unit that distributes auxiliary gas (EGR gas, PCV gas, etc.) is provided in a plurality of branch pipes that distribute intake air to each cylinder of the engine. A hot water passage section through which hot water using the cooling water of the engine flows is provided adjacent to the gas distribution section. Further, a material having good thermal conductivity (carbon powder-containing resin or insert molding of a metal plate) is provided on the partition wall between the gas distribution section and the hot water passage section. Then, the gas distribution section is efficiently kept warm by the hot water heat of the hot water passage section, and the generation and freezing of condensed water in the gas distribution section are suppressed.

JP-A-2018-44518

However, in the technique described in Patent Document 1, although a material having good thermal conductivity is provided in the partition wall between the gas distribution section and the hot water passage section, the hot water temperature depends on the warm-up state of the engine. , There is a time lag between the heat transfer from hot water and the temperature rise inside the gas distribution section. Therefore, even if a defect occurs in the hot water passage portion or the like, it is difficult to detect the defect in a timely manner.

This disclosed technique has been made in view of the above circumstances, and its purpose is to responsively raise the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows, and to keep the temperature stable. In addition, it is an object of the present invention to provide an EGR system capable of timely diagnosing a functional deterioration of a heating film used for heating as a failure without depending on the warm-up state of the engine.

In order to achieve the above object, the technique according to claim 1 is configured such that a part of the exhaust gas discharged from the engine to the exhaust passage is passed as EGR gas to the intake passage through the EGR passage and returned to the engine. In the EGR system, the heat-generating coating provided on at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows, at least a pair of positive and negative electrodes for energizing the heat-generating coating, and the functional deterioration of the heat-generating coating fail. The purpose is to provide a failure diagnosis device for diagnosing.

According to the configuration of the above technique, by energizing the heating film through the positive electrode and the negative electrode, the heating film generates heat, and at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows is heated. Therefore, by arbitrarily controlling the energization of the heat-generating coating, the temperature and temperature rise of at least one inner wall of the intake passage and the EGR passage provided with the coating are adjusted. Here, if a crack or the like occurs in the heating film between the positive electrode and the negative electrode, the current passage at the crack or the like is cut off, so that the current value decreases (the resistance value increases) by that amount. The function of the heating film deteriorates. In addition, the function of the heat generating film deteriorates, and when the engine is started, the intake passage and the EGR passage through which the EGR gas flows cannot be sufficiently heated, and the amount of condensed water generated in the EGR passage and the like increases. As a result, when the amount of condensed water sucked into the engine increases and the combustion in the engine deteriorates (misfire), the fluctuation of the crank angular velocity becomes large between each cylinder of the engine. According to the configuration of the above technique, the functional deterioration of the heating film is diagnosed as a failure by the failure diagnosis device.

In order to achieve the above object, the technique according to claim 2 is the technique according to claim 1, wherein the failure diagnosis apparatus includes a current detecting means for detecting a current value when the heating film is energized and a detection device. It is an object of the present invention to include a failure determining means for determining that there is a failure in the heating film when the current value to be generated becomes equal to or less than a predetermined value.

According to the configuration of the above technique, in addition to the operation of the technique according to claim 1, when the current value at the time of energization of the heating film is detected by the current detecting means, and the detected current value is equal to or less than a predetermined value. In addition, it is determined by the failure determining means that the heating film has a failure. Therefore, the failure of the heating film is determined in real time without depending on the warm-up state of the engine.

In order to achieve the above object, the technique according to claim 3 is the technique according to claim 1, wherein the failure diagnosis apparatus has a resistance detecting means for detecting the resistance value of the heating film and the detected resistance. The purpose of the present invention is to include a failure determining means for determining that there is a failure in the heating film when the value exceeds a predetermined value.

According to the configuration of the above technique, in addition to the action of the technique according to claim 1, when the resistance value of the heat generating film is detected by the resistance detecting means and the detected resistance value becomes equal to or more than a predetermined value, heat is generated. If there is a failure in the coating film, it is determined by the failure determination means. Therefore, the failure of the heating film is determined in real time without depending on the warm-up state of the engine.

In order to achieve the above object, the technique according to claim 4 is the technique according to claim 1, wherein the failure diagnosis device includes a crank angle speed detecting means for detecting the crank angle speed of the engine and a crank to be detected. The purpose of the present invention is to include a failure determining means for determining that there is a failure in the heating film when the fluctuation of the angular velocity becomes larger than a predetermined value.

According to the configuration of the above technique, in addition to the action of the technique according to claim 1, when the crank angular velocity of the engine is detected by the crank angular velocity detecting means and the fluctuation of the crank angular velocity becomes larger than a predetermined value, a heat generating film is formed. If there is a failure in the engine, it is determined by the failure determination means. Therefore, the failure of the heat generating film is indirectly determined without depending on the warm-up state of the engine. Further, as the crank angular velocity detecting means, a crank angular velocity detecting means used for engine control can be used.

In order to achieve the above object, the technique according to claim 5 is the technique according to claim 1, wherein the failure diagnosis device is provided at at least one place of the heating film to detect the temperature of the heating film. A temperature detecting means and a failure determining means for determining that the heating film has a failure when the increase in the temperature detected after the heating film is energized is smaller than a predetermined value with respect to the temperature detected before the heating film is energized. The purpose is to include.

According to the configuration of the above technique, in addition to the action of the technique according to claim 1, the temperature of the heating film is detected by the temperature / current detecting means, and the temperature of the heating film is applied to the temperature detected before the heating film is energized. When the increase in temperature detected after energization is smaller than a predetermined value, it is determined by the failure determining means that the heating film has a failure. Therefore, the failure of the heating film is directly determined in real time without depending on the warm-up state of the engine.

According to the technique according to claim 1, the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows can be raised with good responsiveness, and the temperature can be stably maintained. In addition, it is possible to timely diagnose the deterioration of the function of the heat generating film used for heating as a failure without depending on the warm-up state of the engine.

According to the technique according to claim 2, the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows can be raised with good responsiveness, and the temperature can be stably maintained. In addition, it is possible to timely diagnose the deterioration of the function of the heat generating film used for heating as a failure without depending on the warm-up state of the engine.

According to the technique of claim 3, the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows can be raised with good responsiveness, and the temperature can be stably maintained. In addition, it is possible to timely diagnose the deterioration of the function of the heat generating film used for heating as a failure without depending on the warm-up state of the engine.

According to the technique of claim 4, the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows can be raised with good responsiveness, and the temperature can be stably maintained. In addition, it is possible to timely diagnose the deterioration of the function of the heat generating film used for heating as a failure without depending on the warm-up state of the engine. Further, as the crank angular velocity detecting means, a rotation speed sensor used for engine control can be used, so that failure diagnosis control can be executed without newly providing the crank angular velocity detecting means.

According to the technique of claim 5, the temperature of at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows can be raised with good responsiveness, and the temperature can be stably maintained. In addition, it is possible to directly and timely diagnose the deterioration of the function of the heating film used for heating as a failure without depending on the warm-up state of the engine.

The schematic block diagram which shows the engine system which concerns on 1st Embodiment. FIG. 5 is a side view showing an outline of an intake manifold provided with an EGR gas distributor according to the first embodiment. FIG. 3 is a perspective view showing the EGR gas distributor as viewed from the front side according to the first embodiment. FIG. 5 is a plan view showing an EGR gas distributor according to the first embodiment. The front view which shows the EGR gas distributor according to 1st Embodiment. FIG. 4 is a cross-sectional view taken along the line AA of FIG. 4 showing a gas chamber of an EGR gas distributor according to a first embodiment. FIG. 3 is a perspective view showing the outside of the upper casing according to the first embodiment. FIG. 5 is a plan view showing the inside of the upper casing according to the first embodiment. FIG. 3 is a perspective view showing the inside of the lower casing according to the first embodiment. FIG. 5 is a plan view showing the inside of the lower casing according to the first embodiment. FIG. 8 is a plan view according to FIG. 8 showing the configuration of the upper current sensor according to the first embodiment. FIG. 10 is a plan view according to FIG. 10 showing a configuration of a lower current sensor according to the first embodiment. FIG. 5 is a flowchart showing the contents of energization control for the heat generating film according to the first embodiment. The required energization time map referred to in order to obtain the required energization time according to the intake intake temperature at start and the cooling water temperature at start according to the first embodiment. The flowchart which shows the content of the failure diagnosis control of a heating film which concerns on 1st Embodiment. A failure determination current value map referred to in order to obtain a failure determination current value according to the intake intake temperature at the time of starting according to the first embodiment. FIG. 11 is a plan view according to FIG. 11 showing the configuration of the upper resistance sensor according to the second embodiment. FIG. 12 is a plan view according to FIG. 12, showing the configuration of the lower resistance sensor according to the second embodiment. FIG. 5 is a flowchart showing the contents of failure diagnosis control of the heating film according to the second embodiment. A failure determination resistance value map referred to in order to obtain a failure determination resistance value according to the intake intake temperature at the time of starting according to the second embodiment. FIG. 5 is a flowchart showing the contents of failure diagnosis control of the heating film according to the third embodiment. An EGR starting water temperature map referred to for determining the EGR starting water temperature according to the intake air temperature according to the third embodiment. According to the third embodiment, the graph which shows the 30 degree time taken every time the crank angle advances by 30 degrees. The graph which shows the change of 30 degree time and the crank angle in a normal state according to 3rd Embodiment. The graph which shows the change of 30 degree time and the crank angle at the time of failure according to 3rd Embodiment. FIG. 4 is a plan view according to FIG. 8 showing the inside of the upper casing according to the fourth embodiment. FIG. 10 is a plan view according to FIG. 10 showing the inside of the lower casing according to the fourth embodiment. FIG. 5 is a flowchart showing the contents of failure diagnosis control of the heating film according to the fourth embodiment. The graph which shows the relationship between the number of functional deteriorations and the amount of condensed water generated in relation to the 4th Embodiment. FIG. 5 is a schematic configuration diagram showing another engine system according to the fifth embodiment. FIG. 5 is a plan view showing an EGR gas distributor according to another embodiment. FIG. 5 is a plan view showing an EGR gas distributor according to another embodiment.

Hereinafter, some embodiments in which the EGR system is embodied in a gasoline engine system will be described.

<First Embodiment>
First, the first embodiment will be described in detail with reference to the drawings.

[About the engine system]
FIG. 1 shows a schematic configuration diagram of a gasoline engine system of this embodiment (hereinafter, simply referred to as an “engine system”). The engine system mounted on the automobile includes an engine 1 having a plurality of cylinders. The engine 1 is a 4-cylinder, 4-cycle reciprocating engine and includes well-known configurations such as a piston and a crankshaft. The engine 1 is provided with an intake passage 2 for introducing intake air into each cylinder and an exhaust passage 3 for deriving exhaust gas from each cylinder of the engine 1. The intake passage 2 is provided with an air cleaner 9, a throttle device 4, and an intake manifold 5 from the upstream side thereof. In addition, this engine system includes a high pressure loop type exhaust gas recirculation device (EGR device) 11.

The throttle device 4 is arranged in the intake passage 2 upstream of the intake manifold 5, and the butterfly type throttle valve 4a is opened and closed with a variable opening degree according to the accelerator operation of the driver, so that the amount of intake air flowing through the intake passage 2 is driven. Is designed to be adjusted. The intake manifold 5 is mainly composed of a resin material, is arranged in the intake passage 2 directly upstream of the engine 1, and has one surge tank 5a into which the intake air is introduced and the intake air introduced into the surge tank 5a in the engine 1. It includes a plurality of (four) branch pipes 5b branched from the surge tank 5a for distribution to each cylinder. The exhaust manifold 6 and the catalyst 7 are provided in the exhaust passage 3 in order from the upstream side thereof. For example, a three-way catalyst is built in the catalyst 7 in order to purify the exhaust gas.

The engine 1 is provided with a fuel injection device (not shown) for injecting fuel corresponding to each cylinder. The fuel injection device is configured to inject the fuel supplied from the fuel supply device (not shown) into each cylinder of the engine 1. In each cylinder, a combustible air-fuel mixture is formed by the fuel injected from the fuel injection device and the intake air introduced from the intake manifold 5.

The engine 1 is provided with an ignition device (not shown) corresponding to each cylinder. The igniter is configured to ignite the flammable mixture in each cylinder. The combustible air-fuel mixture in each cylinder explodes and burns due to the ignition operation of the ignition device, and the exhaust gas after combustion is discharged from each cylinder to the outside via the exhaust manifold 6 and the catalyst 7. At this time, the piston (not shown) moves up and down in each cylinder, and the crankshaft (not shown) rotates to obtain power to the engine 1.

[About the EGR system]
The EGR system of this embodiment includes an EGR device 11. The EGR device 11 is configured to flow a part of the exhaust gas discharged from each cylinder of the engine 1 to the exhaust passage 3 as an exhaust gas recirculation gas (EGR gas) to the intake passage 2 and return the exhaust gas to each cylinder of the engine 1. .. The EGR device 11 adjusts the flow rate of the exhaust gas recirculation passage (EGR passage) 12, the exhaust gas recirculation cooler (EGR cooler) 13 for cooling the EGR gas flowing through the EGR passage 12, and the EGR gas flowing through the EGR passage 12. Exhaust gas recirculation valve (EGR valve) 14 and EGR gas flowing through the EGR passage 12 to each cylinder of the engine 1 to distribute the EGR gas to each branch pipe 5b of the intake manifold 5. A device (EGR gas distributor) 15 is provided. The EGR passage 12 includes an inlet 12a and an outlet 12b. The inlet 12a of the EGR passage 12 is connected to the exhaust passage 3 upstream of the catalyst 7, and the outlet 12b of the passage 12 is connected to the EGR gas distributor 15. In this embodiment, the EGR gas distributor 15 constitutes the final stage of the EGR passage 12. In the EGR passage 12, the EGR valve 14 is provided downstream of the EGR cooler 13, and the EGR gas distributor 15 is provided downstream of the EGR valve 14.

In this EGR device 11, when the EGR valve 14 is opened, a part of the exhaust gas flowing through the exhaust passage 3 flows through the EGR passage 12 as EGR gas, and passes through the EGR cooler 13, the EGR valve 14, and the EGR gas distributor 15. It is distributed to each branch pipe 5b of the intake manifold 5, and further distributed to each cylinder of the engine 1 to be circulated.

[About EGR gas distributor]
FIG. 2 shows a schematic side view of the intake manifold 5 provided with the EGR gas distributor 15. The state shown in FIG. 2 shows the arrangement state of the intake manifold 5 attached to the engine 1 in the vehicle, and the upper and lower portions thereof are as shown in FIG. The intake manifold 5 includes a surge tank 5a and a plurality of branch pipes 5b (only one is shown), as well as an outlet flange 5c for connecting the outlet of each branch pipe 5b to the engine 1. In this embodiment, the EGR gas distributor 15 is provided on the upper side of each branch pipe 5b near the uppermost portion of each branch pipe 5b in order to distribute the EGR gas to each of the branch pipes 5b.

FIG. 3 shows a perspective view of the EGR gas distributor 15 as viewed from the front side. FIG. 4 shows the EGR gas distributor 15 in a plan view. FIG. 5 shows the EGR gas distributor 15 in a front view. FIG. 6 shows the gas chamber of the EGR gas distributor 15 with a cross-sectional view taken along the line AA of FIG. The appearance and structure of the intake manifold 5 and the EGR gas distributor 15 shown in FIGS. 2 to 5 show an example of the disclosed technology. As shown in FIGS. 3 to 5, the EGR gas distributor 15 is mainly composed of a resin material and has a horizontally long shape as a whole, and in the longitudinal direction X thereof, as shown in FIG. 1, the intake manifold 5 It is arranged so as to cross the plurality of branch pipes 5b. In this embodiment, the EGR gas distributor 15 is formed in advance separately from the intake manifold 5 and is retrofitted to the intake manifold 5. In this embodiment, the EGR gas distributor 15 is roughly divided into three parts, that is, a gas introduction passage 21 into which the EGR gas is introduced and one gas chamber 22 in which the EGR gas introduced into the gas introduction passage 21 is collected. (The inner diameter thereof is larger than that of the gas introduction passage 21.) And a plurality of (four) gas distribution passages 23 (four) that are branched from the gas chamber 22 and distribute EGR gas from the gas chamber 22 to each branch pipe 5b. Its inner diameter is smaller than that of the gas introduction passage 21 and the gas chamber 22). The gas introduction passage 21 and the gas chamber 22 constitute an example of the gas passage in the disclosed technology.

EGR gas is introduced into the gas inlet 24 of the gas introduction passage 21. An EGR passage 12 is connected to the gas inlet 24. An inlet flange 24a for connecting the EGR passage 12 is provided around the gas inlet 24. The gas introduction passage 21 includes a passage portion 21a extending from the gas inlet 24 and branch passage portions 21b and 21c bifurcated from the passage portion 21a. The gas inlet 24 opens to the front side of the EGR gas distributor 15. The passage portion 21a wraps around from the front side to the rear side of the distributor 15 and continues to the branch passage portions 21b and 21c. The gas chamber 22 has a horizontally long tubular shape. The gas chamber 22 collects the EGR gas introduced into the gas introduction passage 21 from the gas inlet 24. The plurality of gas distribution passages 23 branch off from the gas chamber 22 on the front side of the gas chamber 22. In this embodiment, each gas distribution passage 23 extends obliquely downward from the gas chamber 22 toward each branch pipe 5b and opens.

As shown in FIG. 6, in this embodiment, the EGR gas distributor 15 is composed of two members, an upper casing 26 and a lower casing 27. An upper flange 26a is formed on the outer periphery of the upper casing 26, and a lower flange 27a is formed on the outer periphery of the lower casing 27. The upper casing 26 and the lower casing 27 are integrated by joining the upper flange 26a and the lower flange 27a by welding to form the EGR gas distributor 15.

As shown in FIG. 6, in this embodiment, the heat generating coatings 29 and 30 are provided on the inner wall of the EGR gas distributor 15. That is, the upper heat generating film 29 is provided on the inner wall of the portion of the upper casing 26 that constitutes the gas chamber 22. A lower heating film 30 is provided on a portion of the lower casing 27 that constitutes the gas chamber 22. Further, at both ends of the upper heating film 29 in the width direction (horizontal direction in FIG. 6), a pair of upper positive electrodes 31 for energizing the upper heating film 29 are formed between the inner wall of the upper casing 26 and the upper heating film 29. And the upper negative electrode 32 is provided. At both ends in the width direction of the lower heating film 30, a pair of lower positive electrodes 33 and lower negative electrodes 34 for energizing the lower heating film 30 are provided between the inner wall of the lower casing 27 and the lower heating film 30. .. In this embodiment, the upper heat-generating coating 29 and the lower heat-generating coating 30 have the same thickness and are provided so as to cover almost the entire inner wall of the portion of the upper casing 26 and the lower casing 27 that constitutes the gas chamber 22. .. In this embodiment, although not shown, the inner walls of the portions of the upper casing 26 and the lower casing 27 that form the gas introduction passage 21 are also provided with the upper heating coating 29 and the lower heating coating 30 as well as the inner wall of the gas chamber 22. An upper positive electrode 31 and an upper negative electrode 32, and a lower positive electrode 33 and a lower negative electrode 34 are provided. Further, as shown in FIGS. 3 to 5, in the EGR gas distributor 15, the upstream end portion (near the inlet flange 24a) and the downstream end portion (branch passage portion 21b) of the gas introduction passage 21 and one end of the gas chamber 22. Each of the portion and the intermediate portion is provided with an upper positive terminal 31a and an upper negative terminal 32a extending from the positive electrodes 31 and 33 and the negative electrodes 32 and 34, and a lower positive terminal 33a and a lower negative terminal 34a, respectively. By energizing the heat-generating coatings 29 and 30 from these terminals 31a, 32a, 33a, 34a via the electrodes 31, 32, 33, 34, the heat-generating coatings 29 and 30 generate heat, and the EGR gas distributor 15 generates heat. The inner walls of the gas introduction passage 21 and the gas chamber 22 are heated.

FIG. 7 shows the outside of the upper casing 26 in a perspective view. FIG. 8 shows the inside of the upper casing 26 in a plan view. FIG. 9 shows the inside of the lower casing 27 in a perspective view. FIG. 10 shows the inside of the lower casing 27 in a plan view. As shown in FIG. 8, the upper positive electrode 31 (black-painted line) and the upper negative electrode 32 (white line) are provided along the upper flange 26a so as to face each other on the inner wall of the upper casing 26, respectively. As shown with a gauze in FIG. 8, the upper heat generating coating 29 is provided between the upper positive electrode 31 and the upper negative electrode 32 facing each other so as to cover almost the entire inner wall of the upper casing 26. As shown in FIGS. 9 and 10, the lower positive electrode 33 (black-painted line) and the lower negative electrode 34 (white line) are provided along the lower flange 27a on the inner wall of the lower casing 27, respectively. As shown with a gauze in FIG. 10, the lower heating film 30 is provided between the lower positive electrode 33 and the lower negative electrode 34 facing each other so as to cover almost the entire inner wall of the lower casing 27.

A ground wiring is provided on each of the heat generating coatings 29 and 30. In this embodiment, the EGR gas distributor 15 is connected (attached) to the EGR passage 12 via its inlet flange 24a. As shown in FIG. 3, the inlet flange 24a is provided with a conductive metal collar 25 in its bolt hole. The ground wiring 25a of each of the heat generating coatings 29 and 30 is connected to the metal collar 25. The inlet flange 24a is connected to another flange provided on the upstream side of the EGR passage 12 via a bolt inserted through the metal collar 25. In this case, the upstream side of the EGR passage 12 is connected to the vehicle body via a conductive metal and is grounded. Therefore, by connecting the inlet flange 24a to another flange of the EGR passage 12, it is possible to ground the heat generating coatings 29 and 30.

[About heat-generating film]
Here, the heat generating coatings 29 and 30 will be described. As the heat-generating coatings 29 and 30, for example, "heating coating" manufactured by Toyo Drylube Co., Ltd. can be used. This heat-generating coating is a dry coating in which various conductive pigments are mixed and dispersed in a special binder, and the entire coating can be heated by supplying electric power to the coating via electrodes. The current applied to the blended conductive pigment (conductor) changes to thermal energy (Joule heat), and heat generation efficiency can be obtained. Its features are as follows. (1) The heat generation characteristics can be exhibited at a low voltage. (2) Since it generates heat in a planar shape, it generates heat more uniformly than nichrome wire. (3) It is possible to reduce the thickness and weight. (4) It has excellent flexibility and can be formed into a film. (5) Arbitrary heat generation characteristics can be obtained by adjusting the coating film thickness, electrode length, distance between electrodes, and the like.

[About the electrical configuration of the engine system]
Next, an example of the electrical configuration of the engine system will be described. In FIG. 1, various sensors and the like 71 to 79 provided in the engine system constitute an operating state detecting means for detecting the operating state of the engine 1. The water temperature sensor 71 provided in the engine 1 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 1 and outputs an electric signal according to the detected value. The rotation speed sensor 72 provided in the engine 1 detects the rotation angle (crank angle) of the crankshaft of the engine 1 and uses the change in the crank angle (crank angle speed) as the rotation speed (engine rotation speed) NE of the engine 1. Detects and outputs an electric signal according to the detected value. The rotation speed sensor 72 corresponds to an example of the crank angular velocity detecting means in the disclosed technology. The air flow meter 73 provided in the vicinity of the air cleaner 9 detects the intake air amount Ga flowing through the air cleaner 9, and outputs an electric signal according to the detected value. The intake pressure sensor 74 provided in the surge tank 5a detects the intake pressure PM in the intake passage 2 (surge tank 5a) downstream of the throttle device 4, and outputs an electric signal according to the detected value. The throttle sensor 75 provided in the throttle device 4 detects the opening degree (throttle opening degree) TA of the throttle valve 4a and outputs an electric signal corresponding to the detected value. The oxygen sensor 76 provided in the exhaust passage 3 between the inlet 12a of the EGR passage 12 and the catalyst 7 detects the oxygen concentration Ox in the exhaust and outputs an electric signal according to the detected value. The intake air temperature sensor 77 provided at the inlet of the air cleaner 9 detects the temperature (intake air temperature) THA of the outside air sucked into the air cleaner 9, and outputs an electric signal according to the detected value. Further, each of the current sensors 78A and 78B provided in the vicinity of the EGR gas distributor 15 detects each current value UPAP and DWAP when the heat generating coatings 29 and 30 are energized, and outputs an electric signal corresponding to the detected value. do. That is, the upper current sensor 78A detects the current value (upper current value) UPAP of the upper heating film 29, and the lower current sensor 78B detects the current value (lower current value) DWAP of the lower heating film 30. ing. FIG. 11 shows the configuration of the upper current sensor 78A with a plan view according to FIG. FIG. 12 shows the configuration of the lower current sensor 78B with a plan view according to FIG. As shown in FIG. 11, an upper positive wiring 41 is connected to each upper positive terminal 31a, and an upper current sensor 78A is provided on the upper positive wiring 41. Similarly, as shown in FIG. 12, a lower positive wiring 43 is connected to each lower positive terminal 33a, and a lower current sensor 78B is provided on the lower positive wiring 43. A ground wiring 25a is connected to each of the upper minus terminal 32a and the lower minus terminal 34a. These current sensors 78A and 78B correspond to an example of the current detecting means in this disclosure technique. Further, the ignition switch (IG switch) 79 provided in the driver's seat detects the start or stop of the engine 1 by the driver's investigation and outputs the detection signal.

This engine system further includes an electronic control unit (ECU) 80 that controls the system. Various sensors and the like 71 to 79 are connected to the ECU 80, respectively. Further, in addition to the heat generating coatings 29 and 30 of the EGR valve 14 and the EGR gas distributor 15, an injector (not shown) and an ignition coil (not shown) are connected to the ECU 80. The ECU 80 corresponds to an example of failure determination means in this disclosure technique. Further, in this embodiment, the current sensors 78A, 78B and the ECU 80 constitute an example of the failure diagnosis device in the disclosed technology. As is well known, the ECU 80 includes a central processing unit (CPU), various memories, an external input circuit, an external output circuit, and the like. Predetermined control programs related to various controls are stored in the memory. The CPU performs fuel injection control, ignition timing control, EGR control, and energization control for each of the heat generating coatings 29 and 30 based on a predetermined control program based on the detection signals of various sensors and the like input via the input circuit. In addition, failure diagnosis control and the like of each of the heat generating coatings 29 and 30 are executed.

In this embodiment, the ECU 80 controls the EGR valve 14 according to the operating state of the engine 1 in the EGR control. Specifically, the ECU 80 controls the EGR valve 14 to be fully closed during engine 1 stop, idle operation, deceleration operation, and acceleration operation, and during other operations, the target EGR is determined according to the operating state. The opening degree is obtained, and the EGR valve 14 is controlled to the target EGR opening degree. At this time, when the EGR valve 14 is opened, the engine 1 discharges the exhaust gas to the exhaust passage 3, and a part of the exhaust gas is used as EGR gas in the EGR passage 12, the EGR cooler 13, the EGR valve 14, and the EGR gas distributor 15. It flows into the intake passage 2 (intake manifold 5) via the above, and is returned to each cylinder of the engine 1.

[Regarding energization control for heating film]
Here, the energization control for each of the heat generating coatings 29 and 30 of the EGR gas distributor 15 will be described. FIG. 13 shows the contents of the energization control by a flowchart.

When the process shifts to this routine, in step 100, the ECU 80 determines whether or not the IG is turned on, that is, the engine 1 has started to start, based on the detection signal from the IG switch 79. If the determination result is affirmative, the ECU 80 shifts the process to step 110, and if the determination result is negative, the ECU 80 shifts the process to step 170.

In step 110, the ECU 80 determines the intake air temperature THA, the intake air temperature when the engine is started, that is, the intake air temperature when the IG is on (intake air temperature at start) STHA, and the time when the engine is started, based on the detected values of the water temperature sensor 71 and the intake air temperature sensor 77. Cooling water temperature (cooling water temperature at start-up) STHW is taken in respectively.

Next, in step 120, the ECU 80 determines whether or not the intake air temperature THA is higher than "-20 ° C.". "-20 ° C" is an example of the determination value. If the determination result is affirmative, the ECU 80 shifts the process to 130, and if the determination result is negative, the ECU 80 shifts the process to step 160.

In step 130, the ECU 80 sets the energization time (required energization time) THT (unit: [sec]) required for each of the heat generating coatings 29 and 30 after the start according to the intake intake temperature STHA at the start and the cooling water temperature STHW at the start. calculate. For example, as shown in FIG. 14, the ECU 80 obtains the required energization time THT (unit: [sec]) according to the start intake intake temperature STHA and the start cooling water temperature STHW by referring to the required energization time map. ..

Next, in step 140, the ECU 80 takes in the elapsed time (time after IG on) TIG that started measurement after IG is turned on.

Next, in step 150, the ECU 80 determines whether or not the TIG time after the IG is turned on is shorter than the required energization time THT. If the determination result is affirmative, the ECU 80 shifts the process to step 160, and if the determination result is negative, the ECU 80 shifts the process to step 170.

In step 120 or step 160, the ECU 80 turns on the energization of the heat generating coatings 29 and 30 in order to heat the EGR gas distributor 15. After that, the ECU 80 returns the process to step 100.

On the other hand, in step 170 after shifting from step 100 or step 150, the ECU 80 turns off the energization of the heat generating coatings 29 and 30 in order to stop the heating of the EGR gas distributor 15. After that, the ECU 80 returns the process to step 100.

According to the above-mentioned energization control, the ECU 80 starts energizing the heat generating coatings 29 and 30 after the ignition (IG) is turned on, and continues energizing for the required energization time THT. Further, the ECU 80 changes the required energization time THT for each of the heat generating coatings 29 and 30 according to the intake intake temperature STHA at the start and the cooling water temperature STHW at the start. Specifically, the ECU 80 sets the required energization time THT longer as the intake intake temperature STHA at start and the cooling water temperature STHW at start become lower. Further, the ECU 80 is adapted to constantly turn on the energization of the heat generating coatings 29 and 30 when the intake air temperature THA becomes a predetermined value (-20 ° C.) or less.

Here, when each of the heat generating coatings 29 and 30 of the EGR gas distributor 15 has a functional deterioration related to heat generation, even if the above-mentioned energization control is executed, the heat generating coatings 29 and 30 aim at the EGR gas distributor 15. There is a risk that it will not be able to heat as it passes. For example, as shown by a two-dot chain line in FIG. 8, when a lateral crack K1 is formed along the arrangement of the electrodes 31 and 32 in the upper heating film 29, the current passage at that location is cut off, so that amount is increased. The current value decreases (the resistance value increases), and the function related to heat generation of the upper heating film 29 deteriorates. Therefore, in this embodiment, the failure diagnosis control of the heat generating coatings 29 and 30 is executed. As shown by the alternate long and short dash line in FIG. 8, when a vertical crack K2 that intersects the arrangement of the electrodes 31 and 32 is formed in the upper heating film 29, the current passage at that location is largely cut off. Therefore, the functional deterioration of the upper heating film 29 does not matter.

[About failure diagnosis control of heating film]
Here, the failure diagnosis control for the heat generating coatings 29 and 30 of the EGR gas distributor 15 will be described. FIG. 15 shows the contents of the failure diagnosis control by a flowchart.

When the process shifts to this routine, in step 200, the ECU 80 takes in the starting intake air temperature STHA based on the detected value of the intake air temperature sensor 77.

Next, in step 210, the ECU 80 calculates the failure determination current value D1 according to the start-up intake air temperature STHA. The failure determination current value D1 means a predetermined current value for determining a failure of the heat generating coatings 29 and 30. Normally, when the engine is started after the engine is stopped for a long time, the temperature of the entire engine 1 is equivalent to the outside air temperature (intake air temperature THA), so that the intake air temperature THA is equivalent to the temperatures of the heat generating films 29 and 30. It can be estimated that there is. Therefore, the normal current value (normal resistance value) with respect to the temperatures of the heat generating coatings 29 and 30 can be estimated by substituting the intake air temperature STHA at the time of starting. The ECU 80 can obtain the failure determination current value D1 according to the intake intake temperature STHA at the time of starting, for example, by referring to the failure determination current value map as shown by the thick solid line in FIG. The thin solid line in FIG. 16 indicates the normal current value. In this failure determination current value map, the failure determination current value D1 is set so as to gradually decrease between a predetermined maximum value and a minimum value as the intake intake temperature STHA at start becomes higher. In this embodiment, the normal current value (normal resistance value) with respect to the temperature of each heat generating film 29, 30 is estimated by the intake intake temperature STHA at the start, but the temperature of each heat generating film 29, 30 is directly measured. Therefore, the normal current value (normal resistance value) with respect to the temperature of each of the heat generating coatings 29 and 30 can be estimated.

Next, in step 220, the ECU 80 determines whether or not there is a heating request for the heat generating coatings 29 and 30. The ECU 80 can determine that there is a heating request, for example, when the determination in step 120 is negative or when the determination in step 150 is affirmative in the above-mentioned energization control. If the determination result is affirmative, the ECU 80 shifts the process to step 230, and if the determination result is negative, the ECU 80 returns the process to step 200.

In step 230, the ECU 80 turns on the energization of the heat generating coatings 29 and 30.

Next, in step 240, the ECU 80 determines the current value (upper current value) UPAP of the upper heating coating 29 and the lower heating coating 30 one second after the start of energization based on the detected values of the upper current sensor 78A and the lower current sensor 78B. The current value (lower current value) DWAP is taken in. Here, the reason why the current values UPAP and DWAP 1 second after the start of energization are taken in is to avoid the inrush current at the initial stage of energization and to obtain stable current values UPAP and DWAP.

Next, in step 250, the ECU 80 determines whether or not the upper current value UPAP is larger than the failure determination current value D1. If the determination result is affirmative, the ECU 80 shifts the process to step 260, and if the determination result is negative, the ECU 80 shifts the process to step 270.

In step 260, the ECU 80 determines that the upper heating film 29 is normal because a sufficient current is flowing through the upper heating film 29.

On the other hand, in step 270, the ECU 80 determines that the upper heating film 29 has failed because a sufficient current does not flow through the upper heating film 29. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

After that, the process shifts from step 260 or step 270, and in step 280, the ECU 80 determines whether or not the lower current value DWAP is larger than the failure determination current value D1. If the determination result is affirmative, the ECU 80 shifts the process to step 290, and if the determination result is negative, the ECU 80 shifts the process to step 300.

In step 290, the ECU 80 determines that the lower heating film 30 is normal because a sufficient current is flowing through the lower heating film 30.

On the other hand, in step 300, the ECU 80 determines that the lower heating film 30 has failed because a sufficient current does not flow through the lower heating film 30. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

After that, the ECU 80 returns the process from step 290 or step 300 to step 200.

According to the above-mentioned failure diagnosis control, when the detected upper current value UPAP becomes equal to or less than the failure determination current value D1 (predetermined value), the ECU 80 determines that the upper heating film 29 has a failure and detects it. When the lower current value DWAP becomes equal to or less than the failure determination current value D1 (predetermined value), it is determined that the lower heating film 30 has a failure.

That is, the ECU 80 is adapted to diagnose the failure of the heat generating films 29 and 30 based on the current decrease allowance (which is also the resistance increase allowance) when the heat generating films 29 and 30 are energized. Here, since it becomes difficult for the current to flow through the heat-generating coatings 29 and 30 by the amount of cracks in the heat-generating coatings 29 and 30, a failure can be diagnosed by determining the current decrease. In order to identify the cracked portion in each of the heat generating coatings 29 and 30, it is necessary to detect the current value for each electrode, but the configuration may be complicated. However, since the amount of condensed water generated is substantially proportional to the surface area of the non-heat-generating portion in each of the heat-generating coatings 29 and 30, it is possible to guarantee the function (detection of functional deterioration) related to heat generation even if the cracked portion cannot be specified.

Here, since the upper current value UPAP and the lower current value DWAP can change depending on the temperature of each heating film 29,30 itself, the above-mentioned failure determination current value D1 is corrected by the temperature of each heating film 29,30. It can also be configured to.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the EGR gas flowing through the EGR passage 12 is introduced into the gas introduction passage 21 of the EGR gas distributor 15, and flows while branching from the introduction passage 21 to the gas chamber. It gathers in 22, is suitably distributed from the plurality of gas distribution passages 23 to each branch pipe 5b of the intake manifold 5, is distributed to each cylinder of the engine 1, and is circulated.

Here, in the EGR gas distributor 15 (EGR passage), the generation of condensed water becomes a problem. However, in the EGR gas distributor 15, when the heat generating coatings 29 and 30 are energized via the positive electrodes 31 and 33 and the negative electrodes 32 and 34, the heat generating coatings 29 and 30 generate heat and the gas introduction passage. The inner walls of each of the 21 and the gas chamber 22 are heated. Therefore, by arbitrarily controlling the energization of the heat generating coatings 29 and 30, the temperature and temperature rise of the inner walls of the gas introduction passage 21 and the gas chamber 22 in which the coatings 29 and 30 are provided are adjusted. Therefore, the temperature of the inner wall of the EGR gas distributor 15 (EGR passage) can be raised with good responsiveness, and the temperature can be stably maintained. As a result, it is possible to suppress the generation and freezing of condensed water inside the EGR gas distributor 15.

According to the configuration of this embodiment, the negative electrodes 32 and 34 of the heat generating coatings 29 and 30 are connected to the ground wiring 25a on the metal collar 25 provided on the inlet flange 24a (joint) of the EGR gas distributor 15 (EGR passage). Since it is connected, it is not necessary to separately ground the ground wiring 25a. Therefore, the heat generating coatings 29 and 30 can be grounded without wiring outside the EGR gas distributor 15.

According to the configuration of this embodiment, as described above, the generation of condensed water can be suppressed in the EGR gas distributor 15, so that there is less concern that the condensed water will flow from the EGR gas distributor 15 to each branch pipe 5b. Therefore, the degree of freedom in arranging the EGR gas distributor 15 in the intake manifold 5 is increased. For example, move the EGR gas distributor 15 away from the current position (a position close to the outlet flange 5c) shown by the solid line in FIG. 2 and away from the outlet flange 5c (engine) as shown by the two-point chain line in FIG. In this case, since the EGR gas distributor 15 is moved away from the engine 1, it is possible to suppress the adhesion and accumulation of deposits on the tip of the gas distribution passage 23. , The inner diameter of the gas distribution passage 23 can be reduced to suppress the attenuation of the intake pulsation and the decrease in the engine output. Further, the tip opening of the gas distribution passage 23 can be made flush with the inner wall of the branch pipe 5b, and the resistance of the intake air flow can be minimized.

[About the operation and effect of the failure diagnosis device]
According to the configuration of the failure diagnosis device described above, when cracks or the like occur in the heat generating coatings 29 and 30 between the positive electrodes 31 and 33 and the negative electrodes 32 and 34, the current passage at the cracks and the like. The current value decreases (the resistance value increases) by that amount, and the functions of the heat generating coatings 29 and 30 deteriorate. If the functions of the heat generating coatings 29 and 30 are deteriorated, the EGR gas distributor 15 cannot be sufficiently heated when the engine 1 is started, and the amount of condensed water generated by the EGR gas distributor 15 increases. As a result, when the amount of condensed water sucked into the engine 1 increases and the combustion in the engine 1 deteriorates (misfire), the fluctuation of the crank angular velocity becomes large between the cylinders of the engine 1. According to the configuration of this embodiment, the functional deterioration related to heat generation of the heat generating coatings 29 and 30 is diagnosed as a failure by the current sensors 78A and 78B and the ECU 80 (fault diagnosis device). Specifically, the current values UPAP and DWAP when energization of the heat generating coatings 29 and 30 are detected by the current sensors 78A and 78B, and the detected current values UPAP and DWAP are the failure determination current values D1 (predetermined value). When the following cases are obtained, the ECU 80 determines that each of the heat generating coatings 29 and 30 has a failure. Therefore, the failure of each of the heat generating coatings 29 and 30 is determined in real time without depending on the warm-up state of the engine 1. Therefore, it is possible to make a timely diagnosis without depending on the warm-up state of the engine 1 as a failure of the functional deterioration of the heat generating coatings 29 and 30 used for heating.

In this embodiment, the ECU 80 calculates the failure determination current value D1 according to the intake intake temperature STHA at the time of starting for the failure determination. Therefore, even if the resistance value of each heating film 29, 30 changes depending on the intake air temperature STHA at the time of starting, and the ease of current flow in each heating film 29, 30 changes (even if the ease of heat generation changes), that is the case. After being supplemented, it is determined that each of the heat generating coatings 29 and 30 has a failure. Therefore, it is possible to accurately diagnose the failure of the heat generating coatings 29 and 30 according to the temperature environment at the time of starting the engine 1.

<Second Embodiment>
Next, the second embodiment will be described in detail with reference to the drawings. In the following description, components equivalent to those in the first embodiment will be described with the same reference numerals, omitting description, and focusing on different points.

[About failure diagnosis control of heating film]
This embodiment is different from the first embodiment in particular in terms of the content of failure diagnosis control. In this embodiment, instead of diagnosing the failure of each heating film 29, 30 based on the upper current value UPAP and the lower current value DWAP, the resistance value (upper resistance value) UPOM of the upper heating film 29 and the resistance of the lower heating film 30 The failure of each of the heat generating coatings 29 and 30 is diagnosed based on the value (lower resistance value) DWOM.

Therefore, in this embodiment, the upper resistance value UPOM and the lower resistance value DWOM are detected. FIG. 17 shows the configuration of the upper resistance sensor 88A with a plan view according to FIG. FIG. 18 shows the configuration of the lower resistance sensor 88B with a plan view according to FIG. As shown in FIG. 17, an upper resistance sensor 88A is provided between the upper positive wiring 41 and the ground wiring 25a. Similarly, as shown in FIG. 18, a lower resistance sensor 88B is provided between the lower positive wiring 43 and the ground wiring 25a. These resistance sensors 88A and 88B detect the upper resistance value UPOM and the lower resistance value DWOM, respectively, and output the detection signals to the ECU 80. These resistance sensors 88A and 88B correspond to an example of resistance detecting means in this disclosure technique. Further, in this embodiment, the resistance sensors 88A, 88B and the ECU 80 constitute an example of the failure diagnosis device in the disclosed technology.

FIG. 19 shows the contents of the failure diagnosis control in this embodiment by a flowchart. When the process shifts to this routine, in step 400, the ECU 80 takes in the starting intake air temperature STHA based on the detected value of the intake air temperature sensor 77.

Next, in step 410, the ECU 80 calculates the failure determination resistance value E1 according to the start-up intake air temperature STHA. The failure determination resistance value E1 means a predetermined resistance value for determining a failure of the heat generating coatings 29 and 30. Normally, when the engine is started after the engine is stopped for a long time, the temperature of the entire engine 1 is equivalent to the outside air temperature (intake air temperature THA), so that the intake air temperature THA is equivalent to the temperatures of the heat generating films 29 and 30. It can be estimated that there is. Therefore, the normal resistance value (normal current value) with respect to the temperatures of the heat generating coatings 29 and 30 can be estimated by substituting the intake air temperature STHA at the time of starting. The ECU 80 can obtain the failure determination resistance value E1 according to the intake intake temperature STHA at the time of starting, for example, by referring to the failure determination resistance value map as shown by the thick solid line in FIG. The thin solid line in FIG. 20 indicates the normal resistance value. In this failure determination resistance value map, the failure determination resistance value E1 is set so as to gradually increase between a predetermined minimum value and a maximum value as the intake intake temperature STHA at the start becomes higher. In this embodiment, the normal resistance value (normal current value) with respect to the temperature of each heat generating film 29, 30 is estimated by the intake intake temperature STHA at the start, but the temperature of each heat generating film 29, 30 is directly measured. Therefore, the normal resistance value (normal current value) with respect to the temperature of each of the heat generating coatings 29 and 30 can be estimated.

Next, in step 42, the ECU 80 takes in the upper resistance value UPOM of the upper heating film 29 and the lower resistance value DWOM of the lower heating film 30 based on the detected values of the resistance sensors 88A and 88B.

Next, in step 430, the ECU 80 determines whether or not the upper resistance value UPOM is lower than the failure determination resistance value E1. If the determination result is affirmative, the ECU 80 shifts the process to step 440, and if the determination result is negative, the ECU 80 shifts the process to step 450.

In step 440, the ECU 80 determines that the upper heating film 29 is normal because the resistance value of the upper heating film 29 is sufficiently low.

On the other hand, in step 450, the ECU 80 determines that the upper heating film 29 has failed because the resistance value of the upper heating film 29 is not sufficiently low. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

After that, in step 460 after shifting from step 440 or step 450, the ECU 80 determines whether or not the lower resistance value DWOM is lower than the failure determination resistance value E1. If the determination result is affirmative, the ECU 80 shifts the process to step 470, and if the determination result is negative, the ECU 80 shifts the process to step 480.

In step 470, the ECU 80 determines that the lower heating film 30 is normal because the resistance value of the lower heating film 30 is sufficiently low.

On the other hand, in step 480, the ECU 80 determines that the lower heating film 30 has failed because the resistance value of the lower heating film 30 is not sufficiently low. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

After that, the ECU 80 returns the process from step 470 or step 480 to step 400.

According to the above-mentioned failure diagnosis control, when the detected upper resistance value UPOM becomes the failure determination resistance value E1 (predetermined value) or more, the ECU 80 determines that the upper heating film 29 has a failure and detects it. When the lower resistance value DWOM becomes equal to or higher than the failure determination resistance value E1 (predetermined value), it is determined that the lower heating film 30 has a failure.

[About the operation and effect of the failure diagnosis device]
According to the configuration of the failure diagnosis device described above, when cracks or the like occur in the heat generating coatings 29 and 30 between the positive electrodes 31 and 33 and the negative electrodes 32 and 34, the current passage at the cracks and the like. Therefore, the resistance value increases (the current value decreases) by that amount, and the functions of the heat generating coatings 29 and 30 deteriorate. According to the configuration of this embodiment, the functional deterioration related to the heat generation of the heat generating coatings 29 and 30 is diagnosed as a failure by the resistance sensors 88A and 88B and the ECU 80 (fault diagnosis device). Specifically, when the resistance values UPOM and DWOM of the heat generating coatings 29 and 30 are detected by the resistance sensors 88A and 88B, and the resistance values UPOM and DWOM are equal to or higher than the failure determination resistance value E1 (predetermined value). , It is determined by the ECU 80 that each of the heat generating coatings 29 and 30 has a failure. Therefore, the failure of each of the heat generating coatings 29 and 30 is determined in real time without depending on the warm-up state of the engine 1. Therefore, it is possible to make a timely diagnosis without depending on the warm-up state of the engine 1 as a failure of the functional deterioration of the heat generating coatings 29 and 30 used for heating.

In this embodiment, the ECU 80 calculates the failure determination resistance value E1 according to the intake intake temperature STHA at the time of starting for the failure determination. Therefore, even if the resistance value of each heating film 29, 30 changes depending on the intake air temperature STHA at the time of starting, and the ease of current flow in each heating film 29, 30 changes (even if the ease of heat generation changes), that is the case. After being supplemented, it is determined that each of the heat generating coatings 29 and 30 has a failure. Therefore, it is possible to accurately diagnose the failure of the heat generating coatings 29 and 30 according to the temperature environment at the time of starting the engine 1.

<Third Embodiment>
Next, the third embodiment will be described in detail with reference to the drawings.

[About failure diagnosis control of heating film]
This embodiment is different from each of the above-described embodiments in the content of failure diagnosis control. In this embodiment, instead of diagnosing the failure of each heating film 29,30 based on the upper current value UPAP and the lower current value DWAP or the upper resistance value UPOM and the lower resistance value DWOM, each heating film is based on the crank angle speed of the engine 1. It is designed to diagnose failures of 29 and 30. That is, when the function related to heat generation of the heat generating coatings 29 and 30 deteriorates, the EGR gas distributor 15 cannot be sufficiently heated when the engine 1 is started, and the amount of condensed water generated by the EGR gas distributor 15 increases. As a result, when the amount of condensed water sucked into the engine 1 increases and the combustion in the engine 1 deteriorates (misfire), the fluctuation of the crank angular velocity becomes large between the cylinders. In this embodiment, the failure of each of the heat generating coatings 29 and 30 is diagnosed under such an assumption. The ECU 80 corresponds to an example of failure determination means in this disclosure technique. Then, in this embodiment, the rotation speed sensor 72 and the ECU 80 constitute an example of the failure diagnosis device in the disclosed technology. FIG. 21 shows the contents of the failure diagnosis control by a flowchart.

When the process shifts to this routine, in step 600, the ECU 80 takes in the intake air temperature THA and the cooling water temperature THW based on the detected values of the intake air temperature sensor 77 and the water temperature sensor 71.

Next, in step 610, the ECU 80 calculates the EGR start water temperature THAWEGR according to the intake air temperature THA. The ECU 80 can obtain the EGR start water temperature THAWEGR corresponding to the intake air temperature THA by referring to the EGR start water temperature map as shown in FIG. 22, for example. In this EGR start water temperature map, the higher the intake air temperature THA, the smaller the EGR start water temperature THAWEGR is set between a predetermined maximum value and a minimum value.

Next, in step 620, the ECU 80 determines whether the cooling water temperature THW is higher than the temperature "5 ° C." lower than the EGR start water temperature THAWEGR. "5 ° C" is an example. If the determination result is affirmative, the ECU 80 shifts the process to step 630, and if the determination result is negative, the ECU 80 returns the process to step 600.

In step 630, the ECU 80 determines whether the cooling water temperature THW is lower than the EGR start water temperature THAWEGR. If the determination result is affirmative, the ECU 80 shifts the process to step 640, and if the determination result is negative, the ECU 80 shifts the process to step 670.

In step 640, the ECU 80 takes in the crank angular velocity fluctuation value AΔt30 (i). The ECU 80 can obtain the crank angular velocity fluctuation value AΔt30 (i) by a separate calculation process described below.

That is, as shown in FIG. 23, the ECU 80 takes in the time taken each time the crank angle advances by "30 degrees" during the period of 720 ° C.A (while the crankshaft makes two rotations) as the 30 degree time t30. This 30 degree time t30 is a substitute value for the crank angular velocity. The value obtained by dividing the crank angle of "30 degrees" by the time t30 of 30 degrees corresponds to the crank angular velocity. FIG. 23 graphically shows the 30-degree time t30 taken every time the crank angle advances by 30 degrees.

Next, the ECU 80 sequentially takes in the difference between the front and rear 30 degree time t30 between 720 ° C.A as the 30 degree time difference Δt30 (1), Δt30 (2), Δt30 (3), ... Δt30 (n).

Next, the ECU 80 obtains the crank angular velocity fluctuation value AΔt30 (i) by integrating a series of 30-degree time differences Δt30 (1) to Δt30 (n) that are sequentially taken in. That is, the ECU 80 obtains the total of the changes in the 30-degree time t30 between 720 ° C.A as the crank angular velocity fluctuation value AΔt30 (i) (crank angular velocity fluctuation).

Here, the crank angle speed fluctuation value AΔt30 (i) indicates the degree of rotational fluctuation of the crankshaft, and as shown in FIG. 24, each 30 degree time difference Δt30 (1) to Δt30 (n) is relatively small and is a value before and after. When the fluctuation of the value is relatively small, it means that the rotation fluctuation of the crankshaft is small, and as shown in FIG. 25, when the value is relatively large and the fluctuation of the front-rear value is relatively large, the rotation of the crankshaft It means that the fluctuation is large. When the value of the crank angular velocity fluctuation value AΔt30 (i) is relatively large, it indicates that the combustion state in the engine 1 is unstable (misfire or engine stall is likely to occur), and when the value is relatively small, it means that the combustion state is unstable. Indicates that the combustion state is stable (misfire and engine stall are unlikely to occur). FIG. 24 is a graph showing changes in the 30 degree time t30 (thick line) and the crank angle (solid line) in the normal state. FIG. 25 graphically shows changes in the 30-degree time t30 (thick line) and the crank angle (solid line) at the time of failure.

Next, returning to the flowchart of FIG. 21, in step 650, the ECU 80 adds the number of processes N (i) of the average crank angular velocity fluctuation value AΔt30av by “1”.

Next, in step 660, the ECU 80 calculates the average crank angular velocity fluctuation value AΔt30av (i) according to the following formula, and then returns the process to step 600.
AΔt30av (i) = [AΔt30av (i-1) * (N-1) + AΔt30] / N

On the other hand, in step 670 after shifting from step 630, the ECU 80 determines whether or not the cooling water temperature THW is lower than "85 ° C.". Here, misfire of the engine 1 due to condensed water can occur regardless of the presence or absence of EGR execution. Therefore, in this embodiment, the failure determination is performed from the temperature at the start of EGR to "85 ° C." in the cooling water temperature THW. When the cooling water temperature THW is "85 ° C" or higher, condensed water is not generated. Therefore, the misfire that occurs when the cooling water temperature THW is "85 ° C" or higher is caused by factors other than condensed water. It can be judged that it was done. On the other hand, it can be determined that the misfire that occurred when the cooling water temperature THW was equal to or higher than the temperature at the start of EGR and lower than "85 ° C." was mainly caused by condensed water. "85 ° C" is an example. If the determination result is affirmative, the ECU 80 shifts the process to step 680, and if the determination result is negative, the ECU 80 returns the process to step 600.

In step 680, the ECU 80 takes in the crank angular velocity fluctuation value AΔt30.

Next, in step 690, the ECU 80 determines whether or not the crank angular velocity fluctuation value AΔt30 is larger than the value obtained by adding the margin value α to the average crank angular velocity fluctuation value AΔt30av. The margin value α is a value for avoiding erroneous detection due to variation or the like and ensuring that misfire can be detected reliably. If the determination result is affirmative, the ECU 80 shifts the process to step 700 assuming that the fluctuation of the crank angular velocity has deteriorated. If this determination result is negative, it is assumed that the fluctuation of the crank angular velocity has not deteriorated, and the process proceeds to step 720.

Next, in step 700, the ECU 80 adds the failure determination number NHTR (i) by "1".

Next, in step 710, the ECU 80 determines whether or not the failure determination number NHTR (i) is smaller than the predetermined determination value F1. If the determination result is affirmative, the ECU 80 shifts the process to step 720, and if the determination result is negative, the ECU 80 shifts the process to step 730.

In step 720, the ECU 80 determines that the heat generating coatings 29 and 30 are normal, assuming that there are few failures, and returns the process to step 600.

In step 730, the ECU 80 determines that each of the heat generating coatings 29 and 30 has a failure, assuming that there are many failures, and returns the process to step 600. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

According to the above-mentioned failure diagnosis control, when the detected crank angular velocity fluctuation value AΔt30 becomes larger than the value (predetermined value) obtained by adding the margin value α to the average crank angular velocity fluctuation value AΔt30av, each heat generating film 29 , 30 is determined to have a failure, and when the failure determination frequency NHTR (i) becomes a determination value F1 or more, each of the heat generating coatings 29, 30 is determined to be a failure.

[About the operation and effect of the failure diagnosis device]
According to the configuration of the failure diagnosis device described above, when cracks or the like occur in the heat generating coatings 29 and 30 between the positive electrodes 31 and 33 and the negative electrodes 32 and 34, the current passage at the cracks and the like. The current value decreases (the resistance value increases) by that amount, the functions of the heat generating coatings 29 and 30 deteriorate, and the EGR gas distributor 15 cannot be sufficiently heated. As a result, when the engine 1 is started, the amount of condensed water generated by the EGR gas distributor 15 increases, the amount of condensed water sucked into the engine 1 increases, and the combustion in the engine 1 deteriorates (misfire). According to the configuration of this embodiment, the functional deterioration related to heat generation of the heat generating coatings 29 and 30 is diagnosed as a failure by the rotation speed sensor 72 and the ECU 80 (fault diagnosis device). Specifically, the 30 degree time t30 (crank angular velocity) of the engine 1 is detected by the rotation speed sensor 72, and the fluctuation of the crank angular velocity, that is, the crank angular velocity fluctuation value AΔt30, is obtained by adding the margin value α to the average crank angular velocity fluctuation value AΔt30av. When it becomes larger than the value (predetermined value), the ECU 80 determines that each of the heat generating coatings 29 and 30 has a failure. Therefore, the failure of the heat generating coatings 29 and 30 is indirectly determined without depending on the warm-up state of the engine 1. Therefore, it is possible to make a timely diagnosis without depending on the warm-up state of the engine 1 as a failure of the functional deterioration of the heat generating coatings 29 and 30 used for heating. Here, as the rotation speed sensor 72, the rotation speed sensor 72 used for engine control can be used, so that failure diagnosis control can be executed without newly providing the crank angle detecting means.

In this embodiment, the ECU 80 is adapted to perform failure diagnosis between the temperature at the start of EGR and the temperature at which the cooling water temperature THW reaches "85 ° C.". It can be determined that the misfire that occurred when the cooling water temperature THW was equal to or higher than the temperature at the start of EGR and lower than "85 ° C." was mainly caused by condensed water. In this embodiment, although the failure of each of the heat generating coatings 29 and 30 is indirectly diagnosed based on the fluctuation of the crank angular velocity, it is possible to execute the failure diagnosis with higher accuracy.

<Fourth Embodiment>
Next, the fourth embodiment will be described in detail with reference to the drawings.

[About the temperature sensor of the heating film]
FIG. 26 shows the inside of the upper casing 26 with a plan view according to FIG. FIG. 27 shows the inside of the lower casing 27 in a plan view according to FIG. As shown in FIG. 26, a plurality of upper temperature sensors 81 for detecting the temperature of the upper heating film 29 are provided at a plurality of locations of the upper heating film 29. As shown in FIG. 27, a plurality of lower temperature sensors 82 for detecting the temperature of the lower heating film 30 are provided at a plurality of locations of the lower heating film 30. These temperature sensors 81 and 82 detect the temperature of each part of the corresponding heat generating coatings 29 and 30, and output the detected value to the ECU 80.
[About failure diagnosis control of heating film]
This embodiment is different from each of the above-described embodiments in the content of failure diagnosis control. In this embodiment, the failure of each heat generating film 29, 30 is diagnosed based on the temperature of each heat generating film 29, 30 detected by the temperature sensors 81, 82. The ECU 80 corresponds to an example of failure determination means in this disclosure technique. Then, in this embodiment, the temperature sensors 81, 82 and the ECU 80 constitute an example of the failure diagnosis device in the disclosed technology. FIG. 28 shows the contents of the failure diagnosis control by a flowchart.

When the process shifts to this routine, in step 800, the ECU 80 determines whether or not there is a heating request for each of the heat generating coatings 29 and 30. The ECU 80 can determine that there is a heating request, for example, when the determination in step 120 is negative or when the determination in step 150 is affirmative in the above-mentioned energization control. If the determination result is affirmative, the ECU 80 shifts the process to step 810, and if the determination result is negative, the ECU 80 returns the process to step 800.

Next, in step 810, the ECU 80 takes in the initial coating temperature STHTR for each of the heat generating coatings 29 and 30 detected by the temperature sensors 81 and 82, respectively.

Next, in step 820, the ECU 80 turns on the energization of the heat generating coatings 29 and 30.

Next, in step 830, the ECU 80 determines whether or not a predetermined time has elapsed after energization. If the determination result is affirmative, the ECU 80 shifts the process to step 840, and if the determination result is negative, the ECU 80 returns the process to step 800.

Next, in step 840, the ECU 80 takes in the coating temperature THTR for each of the heat generating coatings 29 and 30 detected by the temperature sensors 81 and 82, respectively.

Next, in step 850, based on the initial coating temperature STHTR and coating temperature THTR taken in for each of the temperature sensors 81 and 82, the rising temperature ΔTHTR at each part where the temperature sensors 81 and 82 are provided is set to the next. Each is calculated by the calculation formula.
ΔTHTR = THTR-STHTR

Next, in step 860, the ECU 80 takes in the function deterioration number NTNG. The functional decrease number NTNG means the number of portions where the rising temperature ΔTHTR becomes smaller than a predetermined determination value. FIG. 29 graphically shows the relationship between the number of functional declines NTNG and the amount of condensed water generated. As shown in FIG. 29, it can be seen that in the EGR gas distributor 15, the amount of condensed water generated increases linearly as the number of functional declines NTNG increases.

Next, in step 870, the ECU 80 determines whether or not the function deterioration number NTNG is larger than the predetermined determination value C1. If the determination result is affirmative, the ECU 80 shifts the process to step 880, and if the determination result is negative, the ECU 80 shifts the process to 890.

In step 880, the ECU 80 determines that the heat-generating coatings 29 and 30, that is, at least one of the upper heating-generating coating 29 and the lower heating-generating coating 30, is out of order because the number of functional deteriorations is large. In this case, the ECU 80 can store the failure determination result in the memory and execute a predetermined notification process.

On the other hand, in step 890, the ECU 80 determines that the heat generating coatings 29 and 30 are normal because the number of functional deteriorations NTNG is not large.

According to the above-mentioned failure diagnosis control, the ECU 80 has an increase temperature of the coating temperature THTR detected after energization of the heat generating coatings 29 and 30 with respect to the initial coating temperature STHTR detected before energization of the heating coatings 29 and 30. When ΔTHTR (increase) is smaller than a predetermined value, it is determined that each of the heat generating coatings 29 and 30 has a failure.

[About the operation and effect of the failure diagnosis device]
According to the configuration of the failure diagnosis device described above, when cracks or the like occur in the heat generating coatings 29 and 30 between the positive electrodes 31 and 33 and the negative electrodes 32 and 34, the current passage at the cracks and the like. The current value decreases (the resistance value increases) by that amount, and the functions of the heat generating coatings 29 and 30 deteriorate. According to the configuration of this embodiment, the functional deterioration related to heat generation of the heat generating coatings 29 and 30 is diagnosed as a failure by the temperature sensors 81 and 82 and the ECU 80 (fault diagnosis device). Specifically, the coating temperature THTRs of the heating coatings 29 and 30 are detected by the temperature sensors 81 and 82, and the heating coatings 29 and 30 with respect to the initial coating temperature STHTR detected before the heating coatings 29 and 30 are energized. When the rising temperature ΔTHTR (increase) of the coating temperature THTR detected after energization is smaller than a predetermined value, the ECU 80 determines that each of the heating coatings 29 and 30 has a failure. Therefore, the failure of the heat generating coatings 29 and 30 is directly determined in real time without depending on the warm-up state of the engine 1. Therefore, it is possible to directly diagnose in a timely manner without depending on the warm-up state of the engine 1 as a failure of the functional deterioration of the heat generating coatings 29 and 30 used for heating.

In particular, in this embodiment, the ECU 80 generates heat when the number of sensors in which the temperature rise ΔTHTR of the detection result is smaller than the predetermined value is larger than the predetermined determination value C1 among the plurality of temperature sensors 81 and 82. It is finally determined that the coatings 29 and 30 have a failure. Therefore, the accuracy of failure determination can be arbitrarily adjusted by setting the determination value C1 as necessary.

<Fifth Embodiment>
Next, the fifth embodiment will be described in detail with reference to the drawings.

[About the intake passage through which EGR gas flows]
This embodiment is different from each of the above-described embodiments in that a heat-generating coating is provided in the engine system. In each of the above-described embodiments, the configurations of the heat generating coatings 29 and 30 provided on the inner walls of the casings 26 and 27 of the EGR gas distributor 15 (EGR passage) and the failure diagnosis device thereof have been described. On the other hand, in this embodiment, a case where the heat generating coatings 29 and 30 of each embodiment and the configuration related to the failure diagnosis device are provided not in the EGR gas distributor 15 but in the intake passage through which the EGR gas flows will be described. do.

That is, FIG. 30 shows another engine system in a schematic configuration diagram. As shown in FIG. 30, in this engine system, a supercharger 8 is provided in the intake passage 2 and the exhaust passage 3 of the engine 1, and a low-pressure loop type EGR device 17 is provided between the intake passage 2 and the exhaust passage 3. Is provided. The supercharger 8 includes a compressor 8a provided in the intake passage 2, a turbine 8b provided in the exhaust passage 3, and a rotating shaft 8c for integrally rotating the compressor 8a and the turbine 8b. The compressor 8a is arranged in the intake passage 2 upstream of the throttle device 4. An intake throttle valve 18 and an air cleaner 9 are provided in the intake passage 2 upstream of the compressor 8a. The turbine 8b is arranged in the exhaust passage 3 between the exhaust manifold 6 and the catalyst 7. The surge tank 5a is provided with an intercooler 10. The EGR passage 12 constituting the EGR device 17 has its inlet 12a connected to the exhaust passage 3 downstream of the catalyst 7, and its outlet 12b connected to the intake passage 2 between the compressor 8a and the intake throttle valve 18. .. The EGR passage 12 is provided with an EGR cooler 13 and an EGR valve 14.

In FIG. 30, each of the heat generating coatings 29 and 30 of each of the above-described embodiments and the portion of the intake passage 2 provided with the configuration related to the failure diagnosis device are shown with a gauze. That is, in this embodiment, in the portion of the intake passage 2 between the outlet 12b of the EGR passage 12 and the compressor 8a, the portion of the intake passage 2 between the compressor 8a and the engine 1, and the intake manifold 5, each of the embodiments. Each of the heat generating coatings 29 and 30 and the failure diagnosis device thereof are provided.

[About the operation and effect of the failure diagnosis device]
According to the configuration of the EGR system of this embodiment described above, the operations and effects of the respective heat-generating coatings 29 and 30 and the portion of the intake passage 2 and the intake manifold 5 provided with the configurations related thereto are as follows. Equivalent action and effect can be obtained.

It should be noted that this disclosure technique is not limited to each of the above-described embodiments, and a part of the configuration may be appropriately modified and implemented within a range that does not deviate from the purpose of the disclosure technique.

(1) In the first to fourth embodiments, as shown in FIG. 4, a gas introduction passage 21 (including a passage portion 21a and two branch passage portions 21b and 21c) and one gas chamber 22 (their thereof). The EGR gas distributor 15 is provided from the inner diameter (the inner diameter is larger than that of the gas introduction passage 21) and the four gas distribution passages 23 (the inner diameter thereof is smaller than that of the gas introduction passage 21 and the gas chamber 22). Configured. On the other hand, as shown in the plan view of the EGR gas distributor 51 in FIG. 31, the gas chamber 52 and each gas distribution passage 53 can be configured to have the same inner diameter as the gas introduction passage 54. Further, by dividing the gas chamber 52 in FIG. 31 into two at the intermediate portion, the entire EGR gas distributor 57 can be configured into a tournament shape as shown in the plan view of the EGR gas distributor 57 in FIG. 32. ..

(2) In each of the above embodiments, the failure of the upper heating film 29 and the lower heating film 30 provided in the EGR gas distributor 15, the intake passage 2 through which the EGR gas flows, and the intake manifold 5 is diagnosed. It can also be configured to individually diagnose a particular site of each exothermic coating.

This disclosed technology can be used for intake passages and EGR passages through which EGR gas flows in gasoline engines and diesel engines.

1 Engine 2 Intake passage 3 Exhaust passage 5 Intake manifold (intake passage)
12 EGR passage 15 EGR gas distributor (EGR passage)
29 Upper heating film 30 Lower heating film 31 Upper positive electrode 32 Upper negative electrode 33 Lower positive electrode 34 Lower negative electrode 51 EGR gas distributor (EGR passage)
57 EGR gas distributor (EGR passage)
72 Rotation speed sensor (crank angular velocity detecting means)
78A upper current sensor (current detecting means)
78B lower current sensor (current detection means)
80 ECU (Failure determination means)
81 Upper temperature sensor (temperature detection means)
82 Lower temperature sensor (temperature detecting means)
88A Upper resistance sensor (resistance detection means)
88B lower resistance sensor (resistance detection means)

Claims (5)

In an EGR system configured to flow a part of the exhaust gas discharged from the engine to the exhaust passage as EGR gas to the intake passage through the EGR passage and return it to the engine.
A heat-generating coating provided on at least one inner wall of the intake passage and the EGR passage through which the EGR gas flows,
At least a pair of positive and negative electrodes for energizing the heating film,
An EGR system including a failure diagnosis device for diagnosing a functional deterioration of the heating film as a failure. In the EGR system according to claim 1,
The failure diagnosis device determines that the heating film has a failure when the current detecting means for detecting the current value when the heating film is energized and the detected current value is equal to or less than a predetermined value. An EGR system comprising a failure determining means for performing. In the EGR system according to claim 1,
The failure diagnosis device includes a resistance detecting means for detecting the resistance value of the heating film and a failure determination for determining that the heating film has a failure when the detected resistance value is equal to or higher than a predetermined value. An EGR system comprising means. In the EGR system according to claim 1,
The failure diagnosis device determines that the crank angular velocity detecting means for detecting the crank angular velocity of the engine and the heat-generating coating have a failure when the detected fluctuation of the crank angular velocity becomes larger than a predetermined value. An EGR system comprising a failure determination means. In the EGR system according to claim 1,
The failure diagnosis device is provided at least in one place of the heat-generating coating, and is a temperature detecting means for detecting the temperature of the heat-generating coating and the heat-generating coating with respect to the temperature detected before energization of the heat-generating coating. An EGR system comprising a failure determining means for determining that the heating film has a failure when the increase in temperature detected after energization of the heating film is smaller than a predetermined value.

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