Control device for internal combustion engine

Abstract

To monitor fixation of a piston ring without providing a temperature sensor for detecting a cylinder wall surface temperature.SOLUTION: A deposit amount DA generated in a ring groove is calculated by using a DA calculation map from fuel injection amount Qf, engine speed NE and a cooling water temperature THW (S11). The deposit amount DA is integrated to determine deposit accumulation amount ΣDA (S12). When the deposit accumulation amount ΣDA exceeds a threshold value α (YES in S13), a failure diagnosis code is set (S14).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine having a piston ring in a ring groove of a piston.

Background Art

[0002] In an internal combustion engine provided with a piston that reciprocates in a cylinder, a piston ring is provided to ensure airtightness between the cylinder and the piston and to control the formation of a lubricating oil film. The piston ring is provided in a ring groove formed in the piston, and as the piston reciprocates, it rotates in the circumferential direction in the ring groove to suitably ensure airtightness and control the lubricating oil film.

[0003] When the piston ring becomes stuck due to carbon sludge or the like deposited in the ring groove, it hinders the ensuring of airtightness and the control of the lubricating oil film. For this reason, it is desired to detect the sticking of the piston ring. For example, Japanese Patent Application Laid-Open No. 6-346789 (Patent Document 1) discloses a sticking monitoring device for a piston ring for a reciprocating engine that provides temperature sensors for detecting the wall surface temperature of the cylinder at two or more positions in the circumferential direction and detects the sticking of the piston ring from the distribution of the wall surface temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the sticking monitoring device of this Patent Document 1, it is necessary to provide two or more temperature sensors per cylinder. For example, in a four-cylinder engine, it is necessary to provide eight or more temperature sensors. Therefore, a large number of temperature sensors are required, and processing for providing the temperature sensors is also required, raising concerns about cost increases.

[0006] An object of the present disclosure is to enable monitoring of piston ring sticking without providing a temperature sensor for detecting the wall temperature of a cylinder.

Means for Solving the Problems

[0007] A control device for an internal combustion engine according to the present disclosure is a control device for an internal combustion engine in which a piston ring is disposed in a ring groove of a piston that reciprocates in a cylinder. The control device includes a deposit estimation means for estimating the deposit accumulation amount deposited in the ring groove based on the operating state of the internal combustion engine, and a stick determination means for determining that there is a possibility that the piston ring is stuck when the deposit accumulation amount estimated by the deposit estimation means exceeds a threshold value.

[0008] Sticking of the piston ring occurs when deposits such as carbon sludge accumulate inside the ring groove and the deposits harden. According to this configuration, the deposit estimation means estimates the deposit accumulation amount deposited in the ring groove based on the operating state of the internal combustion engine. The stick determination means determines that there is a possibility that the piston ring is stuck when the estimated deposit accumulation amount exceeds the threshold value.

[0009] According to this configuration, since the operating state of the internal combustion engine can be obtained by existing sensors or the like, it is possible to monitor the sticking of the piston ring without providing a temperature sensor for detecting the wall temperature of the cylinder.

[0010] Preferably, the deposit estimation means includes a deposit amount calculation unit that calculates the amount of deposits generated in the ring groove per unit period based on the operating state of the internal combustion engine, and the deposit estimation means calculates the deposit accumulation amount by integrating the deposit amount calculated by the deposit amount calculation unit.

[0011] The amount of deposits generated in the ring groove varies depending on the operating state. According to this configuration, the deposit amount calculation unit integrates the deposit amount per unit period, and by integrating this deposit amount, the deposit accumulation amount can be calculated, so that the deposit accumulation amount can be accurately estimated.

[0012] Preferably, the deposit amount calculation unit may calculate the deposit amount based on the rotational speed of the internal combustion engine, the fuel injection amount, and the cooling water temperature.

[0013] According to this configuration, the deposit amount can be calculated using sensors prepared for controlling the internal combustion engine or existing parameters.

[0014] Preferably, when the sticking determination means determines that there is a possibility that the piston ring may stick, an alarm means for giving an alarm may be provided.

[0015] According to this configuration, it is possible to notify the user or the maintenance personnel that there is a possibility that the piston ring may stick.

Advantages of the Invention

[0016] According to the present disclosure, it is possible to monitor the sticking of the piston ring without providing a temperature sensor for detecting the wall temperature of the cylinder.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or corresponding parts in the drawings may be denoted by the same reference numerals and their description may not be repeated.

[0019] FIG. 1 is a diagram showing a schematic configuration of an engine and its control device according to the present embodiment. The engine 1 is a compression self-ignition internal combustion engine and is a direct injection type diesel engine. The engine 1 may be an in-line type engine or an engine with other cylinder layouts (for example, V-type or horizontal type). In the present embodiment, the engine 1 is mounted on a vehicle and used as a drive source of the vehicle.

[0020] The engine 1 includes an engine body 10, a high-pressure fuel pump 16, a common rail 17, a water pump 19, an air cleaner 20, an intercooler 26, an intake manifold 28, a supercharger 30, an exhaust manifold 50, an exhaust treatment device 55, an EGR device (exhaust gas recirculation device) 60, an engine speed sensor 102, an air flow meter 104, an accelerator opening sensor 106, a coolant temperature sensor 108, and a control device 200.

[0021] The engine body 10 includes a cylinder head 11, a cylinder 12, a piston 13, and a fuel injection valve 15. The cylinder 12 is disposed below the cylinder head 11. The piston 13 is inserted into the cylinder 12 so as to be able to reciprocate vertically. A combustion chamber 14 is formed by a space surrounded by the top of the piston 13, the cylinder head 11, and the cylinder 12.

[0022] The fuel injection valve 15 is an injector provided in the cylinder head 11 and sprays fuel into the combustion chamber 14. The fuel stored in a fuel tank (not shown) is pressurized to a predetermined pressure by a high-pressure fuel pump 16 and supplied to the common rail 17. The fuel supplied to the common rail 17 is supplied to the fuel injection valve 15 and is injected from the nozzle portion of the fuel injection valve 15 into the combustion chamber 14. The fuel injection valve 15 supplies the commanded fuel injection amount Qf into the combustion chamber 14 at the commanded timing (injection timing) in response to a control signal from the control device 200.

[0023] The air cleaner 20 removes foreign substances from the air inhaled from outside the engine 1. One end of the first intake pipe 22 is connected to the air cleaner 20.

[0024] The other end of the first intake pipe 22 is connected to the intake air inlet of the compressor 32 of the supercharger 30. One end of the second intake pipe 24 is connected to the intake air outlet of the compressor 32. The compressor 32 supercharges the air flowing from the first intake pipe 22 and supplies it to the second intake pipe 24. One end of the intercooler 26 is connected to the other end of the second intake pipe 24. The intercooler 26 is an air-cooled or water-cooled heat exchanger that cools the air flowing through the second intake pipe 24.

[0025] One end of the third intake pipe 27 is connected to the other end of the intercooler 26. The other end of the third intake pipe 27 is connected to the intake manifold 28. The intake manifold 28 is connected to the intake port of the engine body 10. An intake throttle valve 25 is provided in the middle of the third intake pipe 27, on the intercooler 26 side from the branch point with the EGR 60 described later. The intake throttle valve 25 adjusts the flow rate of the intake air in response to a control signal from the control device 200.

[0026] The exhaust manifold 50 is connected to the exhaust port of the engine body 10. One end of the first exhaust pipe 52 is connected to the exhaust manifold 50. The other end of the first exhaust pipe 52 is connected to the exhaust gas inlet of the turbine 36 of the supercharger 30. Therefore, the exhaust discharged from the exhaust port of each cylinder is supplied to the turbine 36 via the exhaust manifold 50 and the first exhaust pipe 52.

[0027] One end of the second exhaust pipe 54 is connected to the exhaust gas outlet of the turbine 36. An exhaust gas treatment device 55 including an oxidation catalyst 57, a DPF (Diesel Particulate Filter) 58, and a selective reduction catalyst 56 is connected to the other end of the second exhaust pipe 54. The selective reduction catalyst 56 uses urea (ammonia) supplied from a urea addition valve (not shown) to reduce and purify nitrogen oxides in the exhaust gas.

[0028] The third intake pipe 27 and the exhaust manifold 50 are connected by an EGR device 60 without passing through the combustion chamber 14 of the engine body 10. The EGR device 60 includes an EGR valve 62 and an EGR passage 66. The EGR passage 66 connects the third intake pipe 27 and the exhaust manifold 50. The EGR valve 62 is provided in the middle of the EGR passage 66.

[0029] The EGR valve 62 is a regulating valve that adjusts the flow rate of the EGR gas flowing through the EGR passage 66 in response to a control signal from the control device 200. By adjusting the opening degree of the EGR valve 62, the EGR rate (the ratio of the EGR gas amount to the intake gas amount supplied to the engine body) is adjusted. A part of the exhaust gas in the exhaust manifold 50 is returned to the intake side as EGR gas via the EGR device 60, thereby reducing the combustion temperature in the combustion chamber 14 and reducing the generation amount of NOx. Also, since a part of the intake air is replaced by the EGR gas, the air excess ratio in the combustion chamber 14 decreases.

[0030] The supercharger 30 includes a compressor 32 and a turbine 36. A compressor wheel 34 is housed within the housing of the compressor 32, and a turbine wheel 38 is housed within the housing of the turbine 36. The compressor wheel 34 and the turbine wheel 38 are connected by a connecting shaft 42 and rotate integrally. Therefore, the compressor wheel 34 is rotationally driven by the exhaust energy of the exhaust gas supplied to the turbine wheel 38.

[0031] The engine rotation speed sensor 102 detects the rotation speed of the crankshaft, which is the output shaft of the engine 1, as the engine rotation speed NE. The air flow meter 104 detects the flow rate of the fresh air (intake air volume) Qin introduced into the first intake pipe 22. The accelerator opening sensor 106 detects the accelerator opening AP, which is the depression amount of the accelerator pedal. The coolant temperature sensor 108 detects the coolant temperature THW of the engine 1. These sensors output signals indicating the detection results to the control device 200.

[0032] The control device 200 controls the operation of the engine 1. The control device 200 includes a CPU (Central Processing Unit) 201 that performs various processes, a memory 202 that includes a ROM (Read Only Memory) that stores programs and data and a RAM (Random Access Memory) that stores the processing results of the CPU, etc., and an input / output port (not shown) for communicating information with the outside. The above-described sensors (for example, the engine rotation speed sensor 102, the air flow meter 104, the accelerator opening sensor 106, and the coolant temperature sensor 108, etc.) are connected to the input port. Devices to be controlled (for example, the fuel injection valve 15, the intake throttle valve 25, and the EGR valve 62, etc.) are connected to the output port.

[0033] The control device 200 executes predetermined arithmetic processing based on signals from each sensor and device, as well as maps and programs stored in the memory 202. Then, based on the result of the arithmetic processing, the control device 200 controls the fuel injection valve 15, the intake throttle valve 25, the EGR valve 62, etc.

[0034] For example, the control device 200 calculates the fuel injection amount Qf from a fuel injection amount map stored in the memory 202 using the accelerator opening AP and the engine rotational speed NE. Also, the control device 200 calculates the fuel injection timing from a fuel injection timing map stored in the memory 202 using the accelerator opening AP and the engine rotational speed NE. Then, when the calculated fuel injection timing arrives, the control device 200 controls the fuel injection valve 15 to inject fuel corresponding to the fuel injection amount Qf.

[0035] The piston 13 is provided with piston rings 18 to ensure airtightness between the cylinder 12 and the piston 13 and to control the formation of a lubricating oil film. The piston rings 18 are provided to fit into ring grooves formed in the piston 13, and in the present embodiment, they are composed of a top ring 18a, a second ring 18b, and an oil ring 18c. When deposits such as combustion products (carbon sludge) accumulate in the ring grooves, the piston 13 (ring grooves) and the piston rings 18 stick together. When the piston rings 18 stick, as the piston 13 reciprocates, the piston rings 18 cannot move freely within the ring grooves, which hinders ensuring airtightness and controlling the lubricating oil film, and for example, an oil blow-by phenomenon may occur.

[0036] In Patent Document 1, a temperature sensor for detecting the wall temperature of the cylinder 12 at two or more positions in the circumferential direction is provided, and sticking of the piston rings is detected from the wall temperature distribution. For this reason, processing for providing a temperature sensor in the cylinder 12 is required. Also, for example, when the engine 1 is a four-cylinder engine, it is necessary to provide eight or more temperature sensors, which raises a concern about cost increase.

[0037] In the present embodiment, based on the operating state that can be specified by an existing sensor or the like for controlling the engine 1, the amount of deposit deposited in the ring groove is estimated to monitor the sticking of the piston ring 18 without providing a temperature sensor for detecting the wall temperature of the cylinder 12.

[0038] FIG. 2 is a flowchart showing the process of piston ring sticking monitoring control executed by the control device 200. This flowchart is repeatedly processed at predetermined intervals during the operation of the engine 1. In step (hereinafter, step is abbreviated as "S") 10, the fuel injection amount Qf, the engine speed NE, and the coolant temperature THW are acquired. The fuel injection amount Qf is the fuel injection amount Qf calculated from the fuel injection amount map stored in the memory 202 using the accelerator opening AP and the engine speed NE. The engine speed NE is the engine speed NE detected by the engine speed sensor 102, and the coolant temperature THW is the coolant temperature THW detected by the coolant temperature sensor 108.

[0039] In the subsequent S11, the deposit amount DA is calculated from the fuel injection amount Qf, the engine speed NE, and the coolant temperature THW acquired in S10. The deposit amount DA is the amount of deposit generated in the ring groove per unit time. In the present embodiment, the unit time is set to the calculation cycle (interrupt processing cycle) of this flowchart. The calculation cycle may be, for example, 500 ms. The deposit amount DA is calculated using a DA calculation map with the fuel injection amount Qf, the engine speed NE, and the coolant temperature THW as parameters.

[0040] FIG. 3 is a diagram for explaining an example of a method for creating a DA calculation map. FIG. 3(A) is a map of the ring groove temperature Tr (Tr map) with the fuel injection amount Qf, the engine rotational speed NE, and the coolant temperature THW as parameters. This Tr map is obtained by experiments or simulations in which the fuel injection amount Qf, the engine rotational speed NE, and the coolant temperature THW are variously set. Then, from the relationship between the ring groove temperature Tr obtained by experiments or the like and the deposit amount DA generated in the ring groove per unit time, a map of the deposit amount DA with the fuel injection amount Qf, the engine rotational speed NE, and the coolant temperature THW as parameters, shown in FIG. 3(B), is created.

[0041] FIG. 4 is a diagram showing an example of a DA calculation map. The DA calculation map stores, in the memory 202, the map of the deposit amount DA created in FIG. 3(B) (shown in the lower part of FIG. 4) as a calculation table (two-dimensional map) of the deposit amount DA with the fuel injection amount Qf and the engine rotational speed NE as parameters for each coolant temperature THW. In S11, using the DA calculation map shown in FIG. 4, the deposit amount DA is calculated from the fuel injection amount Qf, the engine rotational speed NE, and the coolant temperature THW. For points (numerical values) not present in the DA calculation map, the deposit amount DA is calculated by linear interpolation.

[0042] The piston ring 18 is composed of a top ring 18a, a second ring 18b, and an oil ring 18c. Ring grooves corresponding to each ring are formed in the piston 13, and deposits are generated and deposited in each ring groove. The DA calculation map is a map showing the amount of deposit generated per unit time in the ring groove where the deposit accumulates the most (the deposit amount is large). In the present embodiment, the DA calculation map in FIG. 4 is a map for the ring groove of the top ring 18a, but depending on the characteristics / specifications of the engine, etc., it may also be the case of the second ring 18b or the oil ring 18c.

[0043] In the subsequent S12, the deposit accumulation amount ΣDA is calculated. The deposit accumulation amount ΣDA is calculated by adding the deposit amount DA calculated in S11 to the previous value ΣDAp of the deposit accumulation amount ΣDA. The deposit accumulation amount ΣDA is the integrated value of the deposit amount DA.

[0044] In S13, it is determined whether the deposit accumulation amount ΣDA exceeds the threshold value α. The threshold value α is a value at which the piston ring 18 (in this embodiment, the top ring 18a) shows a sign of sticking due to the deposit accumulated in the ring groove, and is set in advance by experiments or the like. If the deposit accumulation amount ΣDA exceeds the threshold value α, it is determined that the piston ring 18 may stick, and an affirmative determination is made to proceed to S14. If the deposit accumulation amount ΣDA is less than or equal to the threshold value α, a negative determination is made to proceed to S15.

[0045] In S14, a fault diagnosis code of the in-vehicle fault diagnosis device (OBD (On Board Diagnostics)) is set. This fault diagnosis code is stored in the memory 202, and when the engine 1 is being maintained, the maintenance personnel can read the code using a scan tool to inform the maintenance personnel that there is a sign of sticking of the piston ring 18. Note that when setting the fault diagnosis code, the MIL (Malfunction Indication Lamp) 300 may be lit to prompt the user to maintain the engine 1. After S14, proceed to S15.

[0046] In S15, the deposit accumulation amount ΣDA calculated in S12 is written as the previous value ΣDAp to the memory 202, and the current routine is terminated.

[0047] According to this embodiment, based on the fuel injection amount Qf, the engine speed NE, and the coolant temperature THW, the deposit amount DA generated in the ring groove per unit time is calculated from the DA calculation map, and the deposit accumulation amount ΣDA is calculated by integrating the deposit amount DA. Then, when the deposit accumulation amount ΣDA exceeds the threshold value α, it is determined that the piston ring 18 may become stuck, a failure diagnosis code is set, or the MIL 300 is lit to notify of the sign of the sticking of the piston ring 18. Therefore, based on the operating state that can be specified by an existing sensor or the like for controlling the engine 1, by estimating the deposit accumulation amount deposited in the ring groove, it is possible to monitor the sticking of the piston ring 18 without providing a temperature sensor for detecting the wall surface temperature of the cylinder 12.

[0048] Note that the process of S12 in FIG. 2 corresponds to the "deposit estimation means" of the present disclosure, and the process of S13 corresponds to the "stick determination means" of the present disclosure. Also, the process of S11 corresponds to the "deposit amount calculation unit" of the present disclosure.

[0049] In this embodiment, the DA calculation map is set as the amount of deposits generated in the ring groove per unit time. However, for example, it may be set as the amount of deposits generated for each predetermined rotation speed of the engine 1 (for example, every 500 rotations). In this case, the process of the flowchart in FIG. 2 may be interrupt-processed every time the engine 1 rotates a predetermined number of times (for example, every 500 rotations).

[0050] In this embodiment, the deposit amount DA was calculated from the fuel injection amount Qf, the engine rotational speed NE, and the coolant temperature THW. In an engine in which the fuel injection timing has a significant influence on the amount of deposits generated in the ring groove, the deposit amount DA may be calculated from parameters including the fuel injection timing. Also, in an engine in which the lubricating oil temperature has a significant influence on the amount of deposits generated in the ring groove, the deposit amount DA may be calculated using the lubricating oil temperature in addition to, or instead of, the coolant temperature THW. Note that when the EGR rate affects the amount of deposits generated in the ring groove, the deposit amount DA may be corrected by the EGR rate.

[0051] The engine 1 of this embodiment was a compression self-ignition internal combustion engine (diesel engine), but may be a spark ignition internal combustion engine (gasoline engine).

[0052] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Description of Reference Numerals

[0053] 1 Engine, 10 Engine block, 11 Cylinder head, 12 Cylinder, 14 Combustion chamber, 15 Fuel injection valve, 16 High-pressure fuel pump, 17 Common rail, 18 Piston ring, 18a Top ring, 18b Second ring, 18c Oil ring, 20 Air cleaner, 22 First intake pipe, 24 Second intake pipe, 25 Intake throttle valve, 26 Intercooler, 27 Third intake pipe, 28 Intake manifold, 30 Supercharger, 32 Compressor, 34 Compressor wheel, 36 Turbine, 38 Turbine wheel, 42 Connecting shaft, 50 Exhaust manifold, 52 First exhaust pipe, 54 Second exhaust pipe, 55 Exhaust gas treatment device, 56 Selective reduction catalyst, 57 Oxidation catalyst, 58 DPF, 60 EGR device, 62 EGR valve, 66 EGR passage, 102 Engine speed sensor, 104 Airflow meter, 106 Accelerator pedal opening sensor, 108 Cooling water temperature sensor, 200 Control device, 201 CPU, 202 Memory, 300 MIL.

Claims

1. A control device for an internal combustion engine having a piston ring disposed in a ring groove of a piston that reciprocates within a cylinder, deposit estimation means for estimating the amount of deposit accumulated in the ring groove based on the operating state of the internal combustion engine, stick determination means for determining that there is a possibility that the piston ring may stick when the amount of deposit estimated by the deposit estimation means exceeds a threshold value, and comprising: The deposit estimation means has a deposit amount calculation unit that calculates the amount of deposit generated in the ring groove per unit period based on the operating state of the internal combustion engine, The deposit estimation means calculates the deposit accumulation amount by integrating the deposit amount calculated by the deposit amount calculation unit, a control device for an internal combustion engine.

2. The control device for an internal combustion engine according to claim 1, wherein the deposit amount calculation unit calculates the deposit amount based on the rotational speed, fuel injection amount, and cooling water temperature of the internal combustion engine.

3. The control device for an internal combustion engine according to claim 1 or claim 2, further comprising alarm means for giving an alarm when it is determined by the stick determination means that there is a possibility that the piston ring may stick.

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