JP7415308B2 - Fault diagnosis device for crankcase ventilation system - Google Patents

Description

The present invention relates to a failure diagnosis apparatus for a crankcase ventilation system, and more particularly to a failure diagnosis apparatus for a crankcase ventilation system of an engine including a blow-by gas passage connecting a crankcase and an intake passage.

Generally, in automobile engines, it is known that high-pressure combustion gas and unburned gas in the engine combustion chamber leak into the crankcase as blow-by gas beyond the sealing capacity of the piston rings. The engine is provided with a crankcase ventilation system that circulates such blow-by gas in the crankcase to the intake passage using negative pressure in the intake passage, and returns it to the combustion chamber for combustion treatment. In this system, a blowby gas passage is provided that connects the crankcase and the intake passage in order to circulate the blowby gas back into the intake passage.

Conventionally, there is a known technology in which a pressure sensor is provided in such a blow-by gas passage and abnormalities such as gas leakage from the blow-by gas passage or clogging of the blow-by gas passage detected by the pressure sensor are detected (for example, patent Reference 1).

Japanese Patent Application Publication No. 10-184336

However, when detecting failures in the blow-by gas passage due to small-diameter holes on the path of the blow-by gas passage or poor connections between various parts of the blow-by gas passage, which may cause a small amount of gas to escape, variations in the tolerance of the pressure sensor are required. Failures may be erroneously detected due to the influence of

Therefore, it may be possible to detect failures based on the amplitude of pressure pulsations transmitted from inside the crankcase to the blow-by gas passage, rather than the absolute value of the pressure value detected by the pressure sensor, but depending on the operating range of the engine, There is a concern that the pressure pulsation is small and the accuracy of abnormality diagnosis is low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a failure diagnosis device for a crankcase ventilation system that can improve the accuracy of failure diagnosis of a blow-by gas passage. .

In order to achieve the above object, the present invention includes a blow-by gas passage 108 that connects the crankcase 8 and the intake passage 36, a pressure sensor that detects the pressure in the blow-by gas passage, and a pressure sensor that detects the pressure within the blow-by gas passage. A failure diagnosis device for a crankcase ventilation system of an engine, comprising: a diagnostic unit that calculates the amplitude of pressure pulsation in the engine and diagnoses a failure in a blow-by gas passage based on the calculated amplitude of pressure pulsation. The diagnostic unit is characterized in that it is configured to perform failure diagnosis of the blow-by gas passage in a resonant rotational speed region that includes an engine rotational speed that coincides with the natural frequency of pressure pulsations in the intake passage.

According to the present invention configured in this manner, failure diagnosis of the blow-by gas passage is performed in a resonance rotational speed region including an engine rotational speed that coincides with the natural frequency of pressure pulsation in the intake passage. According to the present invention, when diagnosing a fault, the pressure pulsations in the resonant state of the intake passage increase the pressure pulsations in the blow-by gas passage, so the pressure sensor can detect pressure pulsations with a large signal-to-noise ratio. Therefore, for example, when a failure such as a poor connection or a hole in the blow-by gas passage occurs, the degree of reduction in pressure pulsation caused by such failure can be reliably detected by the pressure sensor. As a result, according to the failure diagnosis device for a crankcase ventilation system of the present invention, the accuracy of failure diagnosis of the blow-by gas passage can be improved.

Further, in the present invention, preferably, the diagnostic unit calculates the amplitude of the pressure pulsation based on the difference between the maximum value and the minimum value of pressure detected by the pressure sensor.
According to the present invention configured in this way, the amplitude of pressure pulsation is calculated based on the difference between the maximum value and the minimum value of pressure detected by the pressure sensor, and a failure is diagnosed based on the amplitude of this pressure pulsation. Therefore, a reduction in pressure pulsation due to a failure can be detected more reliably, regardless of the amount of offset of the detected pressure value itself due to, for example, tolerances (variations due to individual differences) of the pressure sensor.

Further, in the present invention, preferably, the blow-by gas passage is provided so as to communicate with the intake passage from the crankcase via the space in the cylinder head cover, and the space in the cylinder head cover is provided with an oil separator, and the blow-by gas passage is preferably provided with a pressure sensor. is provided downstream of the oil separator in the blow-by gas passage.
According to the present invention configured in this manner, since the oil separator is provided in the space within the cylinder head cover, pressure pulsations transmitted from the crankcase side upstream of the oil separator can be attenuated by the oil separator. . Here, when trying to utilize the increase in pressure pulsations in the resonance rotation speed region of the intake passage as in the present invention, the pressure pulsations from the crankcase can become noise. Therefore, according to the present invention in which the pressure sensor is provided on the downstream side (intake passage side) of the oil separator, the S/N ratio of the pressure pulsation detected by the pressure sensor is more reliably increased, and thereby the pressure pulsation transmitted from the intake passage is The degree of reduction in pressure pulsation can be detected more reliably.

Further, in the present invention, preferably, the blow-by gas passage has a first passage communicating from the crankcase to the space inside the cylinder head cover, and one end connected to the cylinder head cover so as to communicate with the space inside the cylinder head cover, and the other end connected to the cylinder head cover so as to communicate with the space inside the cylinder head cover. a second passage whose end is connected to the intake passage, and a pressure sensor is provided in the cylinder head cover.
According to the present invention configured in this way, the blow-by gas passage has a first passage communicating from the crankcase to the space inside the cylinder head cover, and one end connected to the cylinder head cover so as to communicate with the space inside the cylinder head cover. and a second passage whose other end is connected to the intake passage, and the pressure sensor is provided on the head cover. It is possible to more effectively detect failures in the blow-by gas passage due to poor connection to the head cover (dismounted or disconnected) or poor connection to the head cover (dismounted or disconnected).

Further, in the present invention, preferably, an oil separator is provided in the space within the cylinder head cover, and the pressure sensor is provided in the cylinder head cover on the downstream side of the oil separator.
According to the present invention configured in this way, the oil separator is provided in the space inside the cylinder head cover, and the pressure sensor is provided in the cylinder head cover on the downstream side of the oil separator. Transmitted pressure pulsations can be attenuated. Therefore, the pressure sensor detects the resonant pressure pulsations from the intake passage while attenuating the pressure pulsations from the crankcase that can become noise, making it possible to more reliably obtain pressure pulsations with a large signal-to-noise ratio. can.

Further, in the present invention, preferably, the diagnostic unit prohibits failure diagnosis when the throttle valve opening is smaller than a predetermined set opening.
According to the present invention configured in this way, failure diagnosis is prohibited when the throttle valve opening is smaller than a predetermined set opening. Here, when the throttle valve opening degree is small, the pressure pulsation itself in the intake passage becomes small, so the degree of reduction in pressure pulsation when the blow-by gas passage fails also becomes small. Therefore, by prohibiting failure diagnosis when the throttle valve opening is smaller than a predetermined set opening, erroneous diagnosis can be suppressed.

Further, in the present invention, preferably, the connection position of the blow-by gas passage to the intake passage is a position upstream of the throttle valve of the intake passage, and the natural frequency of the pressure pulsation in the intake passage is such that the natural frequency of the pressure pulsation in the intake passage is This is the natural frequency of pressure pulsations in the intake passage between the connection position to the passage and the position of the intake valve.
According to the present invention configured in this way, it is possible to more effectively increase the pressure pulsation in the blow-by gas passage and improve the accuracy of failure diagnosis for the blow-by gas passage.

According to the failure diagnosis device for a crankcase ventilation system of the present invention, it is possible to improve the accuracy of failure diagnosis of a blow-by gas passage.

1 is a schematic configuration diagram of an engine to which a failure diagnosis device for a crankcase ventilation system according to an embodiment of the present invention is applied. 2 is a schematic diagram showing a schematic configuration of a crankcase ventilation system of the engine shown in FIG. 1. FIG. 1 is a control block diagram of a failure diagnosis device for a crankcase ventilation system according to an embodiment of the present invention. FIG. 5 is a flowchart showing a control process executed by a diagnosis unit of a failure diagnosis device for a crankcase ventilation system according to an embodiment of the present invention. 5 is a diagram showing a threshold value of the amplitude of pressure pulsation used in the control flow of FIG. 4, an example of a detected value of a pressure sensor detected during normal times, and an example of a detected value of a pressure sensor detected during a failure. FIG. . FIG. 3 is a diagram illustrating an example of pressure pulsations in the intake passage of the engine according to the embodiment of the present invention when the engine is operating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A failure diagnosis apparatus for a crankcase ventilation system according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

First, referring to FIG. 1, a schematic configuration of an engine to which a failure diagnosis apparatus for an engine crankcase ventilation system according to an embodiment of the present invention is applied will be described. FIG. 1 is a schematic configuration diagram of an engine to which a failure diagnosis device for a crankcase ventilation system according to an embodiment of the present invention is applied.

First, the configuration around the engine block of the engine 1 will be explained.
As shown in FIG. 1, the engine 1 includes a cylinder head 2, a cylinder head cover (hereinafter referred to as a head cover) 4 provided so as to cover a valve train (a camshaft, a VVL 34, etc. not shown) provided in the cylinder head 2, It has a cylinder block 6, a crankcase 8, and an oil pan 9. The engine 1 of this embodiment is a turbocharger-equipped diesel engine mounted on a vehicle, and includes a crankcase ventilation system 10, which will be described later. Incidentally, the crankcase ventilation system 10 may be applied to a gasoline engine, or may be applied to an engine not equipped with a turbo supercharger.

The cylinder block 6 is formed with cylinders 12 (a plurality of cylinders), and each cylinder 12 is provided with a piston 14 . A crankshaft 18 is connected to the piston 14 via a connecting rod 16, so that the piston 14 reciprocates within the cylinder 12.
A cavity 20 is formed in the top surface of the piston 14, and this cavity 20 is partitioned by the ceiling surface on the cylinder head 2 side to form a combustion chamber 20 when the piston 14 is near the top dead center. The engine 1 is provided with an engine rotation speed sensor 22 that detects the rotation speed of the engine 1 by detecting the rotational angular position of the crankshaft 18.

The cylinder head 2 has an intake port 24 and an exhaust port 26 formed therein. The intake port 24 and the exhaust port 26 are connected to the combustion chamber 20 through an intake port opening 24a and an exhaust port opening 26a formed in the ceiling surface of the combustion chamber 20 (lower surface of the cylinder head 2). The intake port 24 and the exhaust port 26 are provided with an intake valve 28 and an exhaust valve 30 that open and close openings 24a and 26a of the combustion chamber 20, respectively.

Further, the cylinder head 2 is provided with an injector 32 that injects fuel. This injector 32 is provided so that its fuel injection port faces the combustion chamber 20 from the ceiling surface of the combustion chamber 20, and is configured to inject fuel directly into the combustion chamber 20 near compression top dead center.

The engine 1 includes a variable valve lift mechanism (hereinafter referred to as VVL) 34 that adjusts the lift amount of the intake valve 28 and the exhaust valve 30. This VVL 34 adjusts the respective lift amounts of the intake valve 28 and the exhaust valve 30. The VVL 34 is provided in the cylinder head 2 along with a camshaft (not shown) and the like, and a head cover 4 is provided to cover them.

Next, the configuration of the intake and exhaust system of the engine 1 will be explained.
The engine 1 includes an intake passage 36 for introducing intake air into the combustion chamber 20 via the intake port 24, and an exhaust passage 38 for discharging exhaust gas from the combustion chamber 20 via the exhaust port 26.

First, an air cleaner 40 for filtering intake air is provided at the upstream end of the intake passage 36, and an air flow sensor 42 is provided near the downstream side of the air cleaner 40 for detecting the flow rate of intake air taken into the intake passage 36. is provided. Further, a surge tank 44 is provided at the downstream end of the intake passage 36 . Although not shown, the intake passage 36 on the downstream side of the surge tank 44 is configured as an independent passage that branches for each of the plurality of cylinders 12, and the downstream end of each independent passage is connected to the intake port 24 of each cylinder 12. each connected.

Further, in the intake passage 36, a compressor 48 of an exhaust turbo supercharger 46 is provided between the air flow sensor 42 and the surge tank 44, and the operation of the compressor 48 supercharges the intake air. As will be described later, the compressor 48 is operated by the rotation of a turbine 50 which is operated by exhaust pressure.

Further, in the intake passage 36, between the compressor 48 of the exhaust turbo supercharger 46 and the surge tank 44, an intercooler 52 for cooling the air compressed by the compressor 48 and a throttle valve 54 are arranged in order from the upstream side. is provided. The throttle valve 54 adjusts the amount of air taken into the combustion chamber 20 of each cylinder 12 by changing the cross-sectional area of the intake passage 36. The throttle valve 54 is provided with a throttle valve opening sensor 56 that detects the rotation angle of its shaft to detect the opening of the throttle valve 54 . The surge tank 44 is also provided with an intake gas temperature sensor 58 that detects the temperature of the gas sucked into the cylinder 12 of the engine 1, and an intake pressure sensor 60 that detects the pressure of the gas sucked into the cylinder 12 of the engine 1. It is being

Next, a turbine 50 of an exhaust turbo supercharger 46 is provided in the exhaust passage 38 . The above-mentioned compressor 48 is connected to the turbine 50, and when the turbine 50 rotates due to the exhaust gas flow, the rotation is transmitted to the compressor 48, and the compressor 48 is operated. Note that the upstream portion of the exhaust passage 38 is constituted by an exhaust manifold having independent passages branched for each of the plurality of cylinders 12 and connected to the exhaust ports 26, and a gathering part where the respective independent passages come together. ing.

A VGT throttle valve 62 is provided near the upstream side of the turbine 50 in the exhaust passage 38, and by controlling the opening degree (throttling amount) of this VGT throttle valve 62, the flow rate of exhaust gas to the turbine 50 is controlled. Can be adjusted. This determines the rotational speed of the turbine 50 rotated by the exhaust gas flow, that is, the pressure ratio of the compressor 48 of the exhaust turbocharger 46 (the gas pressure immediately after flowing out from the compressor 48 relative to the gas pressure immediately before flowing into the compressor 48). ratio) can be adjusted.

Further, in the exhaust passage 38, an exhaust purification device 64 is provided downstream of the turbine 50 of the exhaust turbo supercharger 46 to purify harmful components in the exhaust gas. This exhaust gas purification device 64 is provided with a particulate filter 66 that collects particulates such as soot in the exhaust gas, and is provided upstream of the particulate filter 66 and carries platinum or platinum plus palladium. It is provided downstream of the oxidation catalyst 68 that oxidizes CO and HC in the exhaust gas and the particulate filter 66, and processes (traps) NOx in the exhaust gas to suppress the NOx from being discharged into the atmosphere. It has a lean NOx catalyst 70. The particulate filter 66 and the oxidation catalyst 68 are housed in a first case 72 , and the lean NOx catalyst 70 is housed in a second case 74 that is separate from the first case 72 .

Next, the EGR device of the engine 1 will be explained.
The engine 1 includes two EGR devices 76 and 78 that recirculate part of the exhaust gas flowing through the exhaust passage 38 to the intake passage 36. The first EGR device 76 is a device for circulating high-pressure exhaust gas that includes a high-pressure EGR passage 80, and the second EGR device 78 is a device for circulating low-pressure exhaust gas that includes a low-pressure EGR passage 82. It is a device.

The high-pressure EGR passage 80 connects the exhaust passage 38 on the upstream side of the turbine 50 of the exhaust turbocharger 46 and the intake passage 36 on the downstream side of the compressor 48. More specifically, the high-pressure EGR passage 80 includes a portion of the exhaust passage 38 between the exhaust manifold and the turbine 50 of the exhaust turbo supercharger 46, and a portion of the intake passage 36 between the throttle valve 54 and the surge tank 44. Connect with. As shown in FIG. 1, the high-pressure EGR passage 80 extends between a connecting portion 38a with the exhaust passage 38 and a connecting portion 36a with the intake passage 36. An exhaust pressure sensor 83 that detects the pressure of exhaust gas exhausted from the engine 1 is provided near the upstream side of the connection portion 38a of the high-pressure EGR 50 in the exhaust passage 38.

The high pressure EGR passage 80 includes a cooler side passage (first high pressure EGR passage) 84 for cooling and recirculating exhaust gas, and a cooler bypass side passage (second high pressure EGR passage) for recirculating exhaust gas at the same temperature. ) 86.
The cooler side passage 84 is provided with a high-pressure EGR cooler 88 for cooling exhaust gas passing therethrough. The cooler bypass side passage 86 is configured as a passage that bypasses the high pressure EGR cooler 88.
On the downstream side of the high-pressure EGR cooler 88 in the cooler-side passage 84, there is a cooler-side EGR valve (first high-pressure EGR valve) 90 that changes the cross-sectional area of the cooler-side passage 84, and an opening degree of the cooler-side EGR valve 90 is detected. A cooler-side EGR valve opening sensor 91 is provided.

The cooler bypass side passage 86 also includes a cooler bypass side EGR valve (second high pressure EGR valve) 92 that changes the cross-sectional area of the cooler bypass side passage 86, and a cooler bypass side EGR valve 92 that detects the opening degree of the cooler bypass side EGR valve 92. A bypass side EGR valve opening sensor 93 is provided.

In this embodiment, the two EGR valves 90 and 92 are configured as high-pressure EGR valves (HP-EGR valves) that adjust the amount of exhaust gas circulating through the high-pressure EGR passage 80.

The low pressure EGR passage 82 connects the exhaust passage 38 on the downstream side of the turbine 50 and the intake passage 36 on the upstream side of the compressor 48. More specifically, the low-pressure EGR passage 82 includes a portion of the exhaust passage 38 between the particulate filter 66 and the lean NOx catalyst 70 (a portion between the first case 72 and the second case 74) and the intake passage 36. A portion between the air flow sensor 42 and the compressor 48 is connected. As shown in FIG. 1, the low-pressure EGR passage 82 extends between a connection part 38b with the exhaust passage 38 and a connection part 36b with the intake passage 36.

The low pressure EGR passage 82 is provided with a low pressure EGR cooler 94 that cools the exhaust gas passing through the passage. Furthermore, on the downstream side of the low pressure EGR cooler 94 in the low pressure EGR passage 82, there is a low pressure EGR valve (LP-EGR valve) 96 that changes the cross-sectional area of the low pressure EGR passage 82, and an opening degree of the low pressure EGR valve 96 is detected. A low pressure EGR valve opening sensor 97 is provided.

An exhaust shutter valve 98 is provided in the exhaust passage 38 at a portion downstream of the connection portion 38b of the low-pressure EGR passage 82 and upstream of the lean NOx catalyst 70. The exhaust shutter valve 98 changes the cross-sectional area of a portion of the exhaust passage 38 downstream of the connecting portion 38b of the low-pressure EGR passage 82 and upstream of the lean NOx catalyst 70. When its cross-sectional area is reduced (when the opening degree of the exhaust shutter valve 98 is reduced), the pressure at the connecting portion 38a of the low-pressure EGR passage 82 in the exhaust passage 38 increases, and the exhaust passage of the low-pressure EGR valve 96 in the low-pressure EGR passage 82 increases. The differential pressure between the 38 side and the intake passage 36 side increases. Therefore, by controlling the opening degrees of the low pressure EGR valve 96 and the exhaust shutter valve 98, the amount of recirculation of exhaust gas through the low pressure EGR passage 82 is adjusted.

Further, in this embodiment, the engine 1 is controlled by a PCM (Power-train Control Module) 100. The PCM 100 is a controller based on a well-known microcomputer, and is composed of a central processing unit (CPU) that executes programs, a memory such as RAM or ROM that stores programs and data, and input/output of electrical signals. and an input/output (I/O) bus. This PCM 100 constitutes a diagnostic unit in this embodiment (see FIG. 3).

Next, the crankcase ventilation system in this embodiment will be explained with reference to FIGS. 1 and 2. FIG. 2 is a schematic diagram showing a schematic configuration of the crankcase ventilation system of the engine shown in FIG. 1.
As shown in FIGS. 1 and 2, the crankcase ventilation system 10 of this embodiment communicates the inside of the crankcase 8 with the space 102 inside the head cover 4, and the gas G inside the crankcase 8 (see FIG. 2) a first communication passage 104 that allows gas G to flow into the space 102; and a second communication passage 106 that communicates the space 102 in the head cover 4 with the intake passage 36 and allows the gas G that has flowed into the space 102 to circulate back to the intake passage 36. A blow-by gas passage 108 is provided.

A space 102 within the head cover 4 also constitutes this blow-by gas passage 108.
The space 102 is a closed space formed by the cylinder head 2 and the head cover 4 and includes a partition plate (not shown).

In this embodiment, the first communication passage 104 is a passage formed in the cylinder block 6, and the second communication passage 106 is composed of a hose. The hose 106 serving as the second communication passage has one end 106a attached to the head cover 4 and the other end 106b attached to the intake passage 36 so as to communicate with the space 102 inside the head cover 4 and the intake passage 36. There is.

An oil separator 110 is provided in the space 102 in the head cover 4 in the blow-by gas passage 108 to separate gas and oil in the blow-by gas G flowing from the first communication passage 104. The oil separator 110 allows the separated oil to be returned to the crankcase 8 side, and the separated gas G to be passed to the second communication path 106 side.
As described above, the blow-by gas passage 108 is provided to communicate with the intake passage 36 from the crankcase 8 via the space 102 in the head cover 4.

As shown in FIGS. 1 and 2, in the space 102 in the head cover 4, a space 102a on one side across the oil separator 110 communicates with the first communication path 104, and a space 102b on the other side across the oil separator 110. is in communication with the second communication path 106. A pressure sensor 112 is attached to the head cover 4 to detect the pressure value within the blow-by gas passage 108 (space 102).

In this embodiment, the pressure sensor 112 is provided so as to face the space 102b on the other side described above, so that the pressure sensor 112 detects the pressure value of the blow-by gas G in the space 102 on the downstream side of the oil separator 110. It is set up to do so. In addition, as a modification, the pressure sensor (112) may be attached to another location of the blow-by gas passage 108.

Here, a technical matter in which the pressure pulsations in the intake passage 36 that occur during operation of the engine 1 increase the pressure pulsations of the blow-by gas in the blow-by gas passage 108 due to resonance in the intake passage 36 will be described.
First, when the engine 1 is operating, the intake valve 28 opens and closes the intake port opening 24a at predetermined time intervals depending on the engine speed, so that the intake pressure flowing in the intake passage 36 has a predetermined frequency. Pulsation occurs. Such pressure pulsations (pressure oscillations/periodic pressure fluctuations) within the intake passage 36 are added to the pressure of the blow-by gas flowing within the blow-by gas passage 108 connected to the intake passage 36, and the pressure pulsations are transmitted.

Here, the length of the inside of the intake passage 36 is the length of the intake system including the intake passage 36 (for example, the system including the intake passage 36, the throttle valve 54, the intercooler 52, the compressor 48, etc. as shown in FIG. It has a natural frequency (natural frequency in the intake passage) whose main factor is the diameter and diameter. When such a natural frequency matches the frequency of pressure pulsations within the intake passage 36, the pressure pulsations within the intake passage 36 increase due to resonance.

In other words, when the engine speed is such that the frequency of pressure pulsations (in the intake passage 36) that match the natural frequency of the intake system is generated, the pressure pulsations have a resonance peak. , the pressure pulsations within the intake passage 36 increase. Additionally, along with this, the pressure pulsations of the gas within the blow-by gas passage 108 connected to the intake passage 36 also increase. In this embodiment, such an engine speed is referred to as "an engine speed that matches the natural frequency of pressure pulsations in the intake passage."

Further, the pressure pulsation increases even in a predetermined engine speed range before and after the resonance peak of the pressure pulsation in the intake passage 36. In this embodiment, such an engine rotation speed region is referred to as a "resonant rotation speed region." In this resonance rotation speed region, as the pressure pulsation of the intake air in the intake passage 36 increases, the pressure pulsation in the blow-by gas passage 108 also increases.

In particular, the natural frequency of the intake system that increases the pressure pulsations in the blow-by gas passage 108 is determined by 36 (intake system).
In this embodiment, as will be described later, the crankcase ventilation system utilizes the natural frequency of pressure pulsations within the intake passage 36 from the position of the intake valve 28 to the position where the blow-by gas passage 108 is connected. 10 failures (failures of the blow-by gas passage 108) are diagnosed.

Next, a control system of a failure diagnosis device for a crankcase ventilation system according to this embodiment will be explained with reference to FIG. FIG. 3 is a control block diagram of a failure diagnosis device for a crankcase ventilation system according to an embodiment of the present invention.

As shown in FIG. 3, the PCM 100 includes an output signal related to the rotation speed of the engine 1 from the engine rotation speed sensor 22, and an output signal related to the opening degree of the throttle valve 54 from the throttle valve opening sensor 56. A signal and an output signal relating to the pressure value in the blow-by gas passage 108 from the pressure sensor 112 are input.

Based on the input signal from the engine speed sensor 22 and the input signal from the throttle valve opening sensor 56, the PCM 100 controls the first and second high pressure EGR valves (HP-EGR valves) 90 and 92, and the low pressure EGR valve. (LP-EGR valve) 96 and throttle valve 54.

For example, in the present embodiment, the PCM 100 uses the low-pressure EGR passage 82 based on the input signals from the engine speed sensor 22 and the throttle valve opening sensor 56, that is, based on the engine speed Ne and the engine rotational load Te. A low-pressure EGR target recirculation amount, which is a target value of the exhaust gas recirculation amount, and a high-pressure EGR target recirculation amount, which is a target value of the exhaust gas recirculation amount by the high-pressure EGR passage 80, are determined.

Further, in this embodiment, the PCM 100 uses low pressure EGR and high pressure EGR depending on the operating range of the engine 1.
That is, in a low load region of the engine 1, the high pressure EGR valves (HP-EGR) 90, 92 and the low pressure EGR valve (LP-EGR valve) 96 are controlled so that exhaust gas is recirculated through the high pressure EGR passage 80. Specifically, while the low pressure EGR valve 96 is closed, the opening degrees of the first and second high pressure EGR valves 90 and 92 are controlled to an opening degree that allows the determined high pressure EGR target recirculation amount to be obtained.

In addition, the PCM 100 controls the high pressure EGR valves (HP-EGR) 90 and 92 and the low pressure EGR valve (LP-EGR) 96 so that exhaust gas is recirculated through the low pressure EGR passage 82 in the medium to high load region of the engine 1. do. Specifically, while closing the first and second high-pressure EGR valves 90 and 92, the opening degree of the low-pressure EGR valve 96 is controlled to an opening degree that allows the determined low-pressure EGR target recirculation amount to be obtained. In the present embodiment, the opening degree of the low pressure EGR valve 96 is controlled (determined) based on the controlled opening degree of the exhaust shutter valve 98, so that a target low pressure EGR recirculation amount can be obtained.
Furthermore, as a modification, all of the EGR valves 90, 92, and 96 may be closed in a predetermined high load region so that the exhaust gas is not recirculated by EGR.

Note that the above-described determination of the EGR target recirculation amount and control of the high-pressure EGR valves 90, 92 and low-pressure EGR valve 96 according to the rotational load of the engine 1 are executed based on a predetermined map stored in the PCM 100. Note that the PCM 100 stops the recirculation of exhaust gas by EGR when the combustion efficiency of the engine 1 decreases due to the operation of EGR (for example, when the engine water temperature is low).

Although not shown in FIG. 3, the PCM 100 controls the injector 32, VVL 34, VGT throttle valve 62, and exhaust shutter valve 98 based on input signals from the engine speed sensor 22 and throttle valve opening sensor 56. do.

Furthermore, the PCM 100 according to the present embodiment, as described below, based on the input signal from the engine rotation speed sensor 22, the input signal from the throttle valve opening sensor 56, and the input signal from the pressure sensor 112, A failure diagnosis of the crankcase ventilation system 10 is performed, and when a failure is diagnosed, the notification device 120 notifies the driver or the like of the failure. A failure of the crankcase ventilation system 10 is, for example, a disconnection or tearing of the hose 106, and the notification device 120 is, for example, an indicator provided on an instrument panel.

Next, with reference to FIGS. 4 to 6, the content of the control process for failure diagnosis executed by the diagnosis unit (PCM) of the failure diagnosis apparatus for the crankcase ventilation system according to the embodiment of the present invention will be explained. FIG. 4 is a flowchart showing the control process executed in the diagnosis unit of the failure diagnosis device for the crankcase ventilation system according to the embodiment of the present invention, and FIG. 5 shows the amplitude of pressure pulsation used in the control flow of FIG. FIG. 6 is a diagram showing the threshold value of the engine according to the embodiment of the present invention, an example of the detection value of the pressure sensor detected during normal times, and an example of the detection value of the pressure sensor detected at the time of failure. FIG. 3 is a diagram showing an example of pressure pulsations in the intake passage when the engine is operating.

As shown in FIG. 4, the PCM 100 first reads output signals (sensor values) from the engine speed sensor 22, throttle valve opening sensor 56, and pressure sensor 112 in S1. In S1, the PCM 100 calculates the engine rotational speed Ne, the throttle valve opening TVO, the engine rotational load Te, and the pressure value P in the blow-by gas passage 108 based on these read values.

Next, in S2, as a first failure diagnosis condition, it is determined whether the engine rotational load Te read in S1 is within a predetermined rotational load range T1, and as a second failure diagnosis condition, in S1 It is determined whether the read engine speed Ne is within the resonance region R1 of the intake system.

Here, the first and second failure diagnosis conditions will be explained.
First, in this embodiment, as a first failure diagnosis condition, the rotational load range T1 for which failure diagnosis is performed is set in the range of 20 kN to 1/2 of the maximum load of the engine 1 (T1 = 20 kN to 1/2 2T _MAX ).
In this way, by setting the lower limit to 20 kN and setting the light load region smaller than 20 kN as the diagnosis prohibited region, it is possible to prevent the pressure pulsation detected by the pressure sensor 112 from becoming too small and resulting in a false diagnosis. That's what I do.

On the other hand, by setting the upper limit value to 1/2 of the maximum rotational load and setting the rotational load area exceeding 1/2 of the maximum load as a diagnosis prohibited area, the presence or absence of a failure can be reliably diagnosed. There is. This is because the pressure pulsations in the intake system are large in the rotational load region on the high load side, which exceeds 1/2 of the maximum load, so even if the crankcase ventilation system 10 is out of order, it will be detected by the pressure sensor 112. This is because there is a concern that the pressure pulsations caused by the
Note that the range T1 from 20 kN to 1/2 of the maximum load described above is just an example, and may be set to a range having other values depending on the specifications of the engine 1 and the like.

Next, the second fault diagnosis condition, "resonance region of the intake system", is the "resonant rotation speed region" mentioned above, which corresponds to the engine rotation speed that matches the natural frequency of the pressure pulsation in the intake passage 36. This is the resonant rotational speed region that includes In this embodiment, as described above, the natural frequency in the intake passage 36 from the position of the intake valve 28 to the position where the blow-by gas passage 108 is connected is used as the natural frequency of the pressure pulsation in the intake passage 36. are doing.

In this embodiment, the natural frequency (Hz) in the intake passage 36 from the position of the intake valve 28 to the position where the blow-by gas passage 108 is connected is determined in advance, and the engine rotation speed Ne that matches the natural frequency is determined in advance. is set at approximately 1450 (rpm). Further, the resonance rotation speed region is set to 1300 to 1600 rpm.
In this way, in S2, the resonance range R1 of the intake system, which is the second failure diagnosis condition, is set to 1300 to 1600 rpm (see FIG. 5).

Each setting value mentioned above is based on, for example, the experimental results of actually operating the engine 1 as shown in Fig. 1, or the simplified model of the engine 1 as shown in Fig. 2 and subjecting it to experimental analysis. Configurable. Note that the engine rotation speed (rpm) that matches the natural frequency (Hz) can be calculated from the opening/closing timing of the intake valve 28 and the like.

As shown in FIG. 4, in S2, if the engine rotational load Te read in S1 is within the predetermined rotational load range T1, and the engine rotational speed Ne read in S1 is in the resonance region R1 of the intake system, , the process proceeds to S3 assuming that the first and second failure diagnosis conditions are satisfied. If it is determined in S2 that the first and second failure diagnosis conditions are not met, the process returns to S1 and the processes in S1 and S2 are repeated until the first and second failure diagnosis conditions are satisfied.

Next, in S3, as a third failure diagnosis condition, it is determined whether the throttle valve opening TVO read in S1 is equal to or greater than a predetermined throttle valve opening TVO1.
In this embodiment, the predetermined throttle valve opening TVO1 is set to 20% of the maximum opening (fully open). Thus, in S3, the third failure diagnosis condition is the throttle valve opening of 20% to 100%. In other words, in S3, a throttle valve opening TVO of less than 20% is set as a diagnosis prohibition condition, thereby preventing the pressure pulsation detected by the pressure sensor 112 from becoming too small and causing a false diagnosis. .

This is because, especially when the throttle valve 54 is fully closed, the pressure pulsation becomes small and there is a high risk of misdiagnosis, so by setting an area smaller than 20% as a failure diagnosis prohibited area, misdiagnosis can be reliably suppressed. It was designed to do so. Note that the predetermined throttle valve opening degree TVO1 may be set to other numerical values, such as 10% or 25%, depending on the specifications of the engine 1 and the like.

As mentioned above, the natural frequency in the intake passage is mainly determined by the length and diameter of the intake system including the intake passage 36 (see FIG. 2), so the opening degree of the throttle valve 54 is smaller than, for example, 20%, the length that affects the natural frequency of the intake system becomes substantially short, and the natural frequency may become high. Further, if the opening degree of the throttle valve 54 is smaller than, for example, 20%, the pressure pulsation itself may become a factor of attenuation.
The predetermined throttle valve opening TVO1 may be determined by taking these factors into consideration. Note that when the natural frequency changes depending on the throttle valve opening, the value of the second fault diagnosis area described above may be changed depending on the throttle valve opening.

As shown in FIG. 4, in S3, if the throttle valve opening degree TVO is equal to or greater than the predetermined throttle valve opening degree TVO1, it is assumed that the third failure diagnosis condition is satisfied, and the process proceeds to S4. If it is determined in S3 that the third failure diagnosis condition is not satisfied, the process returns to S1 and the processes of S1 to S3 are repeated until the first to third failure diagnosis conditions are satisfied.

Next, the process proceeds to S4, and the amplitude of pressure pulsation (Peak to Peak) P _PP for a predetermined period is calculated from the output value of the pressure sensor 112 (pressure value in the blow-by gas passage 108) read in S1. In this S4, if a detected value of a pressure sensor having pulsation as shown in FIG. 6 is obtained, the amplitude of the pressure pulsation is calculated from the difference between the maximum value and minimum value within several cycles (3 cycles in FIG. 6). Calculate. Note that 3 cycles is an example, and the amplitude of the pressure pulsation may be the difference between the maximum value and the minimum value within other cycle numbers depending on the engine speed Ne etc. The difference from the minimum value may be taken as the amplitude of pressure pulsation.

Next, the process proceeds to S5, and it is determined whether the pressure amplitude P _PP calculated in S4 is less than or equal to a predetermined threshold value. The predetermined threshold value is a threshold value A as shown in FIG. 5, where the vertical axis is the pressure pulsation amplitude value P _PP calculated in S5 and the horizontal axis is the engine rotation speed. In this embodiment, the pressure pulsation itself increases as the engine speed Ne increases, so the threshold value A itself is set so that the higher the engine speed Ne becomes, the higher the threshold value becomes. Such a threshold value is determined in advance through experiments, model analysis, etc., and is stored in the memory of the PCM 100.

If it is determined in S5 that the pressure amplitude _PPP is equal to or less than a predetermined threshold, the process proceeds to S6, where it is determined whether the time during which the pressure amplitude _PPP is equal to or less than a predetermined threshold continues for a predetermined period of time. Determine. In this embodiment, in order to reliably determine that the crankcase ventilation system is out of order, the predetermined time is set to about several seconds (3 to 10 seconds).

If it is determined in S6 that the time during which the pressure amplitude P _PP is below the predetermined threshold has continued for a predetermined period of time, the process proceeds to S7 and it is determined that the crankcase ventilation system (CV system) is malfunctioning ( diagnosis) and is notified by the notification device 120.

Here, FIG. 5 shows three examples of failures in which the pressure amplitude P _PP is equal to or less than the threshold value A. In FIG. 5, a failure (case 1) occurs when the hose 106 is disconnected from the crankcase 8, a failure (case 2) occurs when the hose 106 disconnects from the intake passage 36, and a failure (case 3) occurs when the hose 106 is disconnected from the intake passage 36. ) is an experimental example showing a case where a tear occurs in the hose 106. In both cases, the resonance region R1 of the intake system shows a small value that is significantly decreased compared to when the CV system 10 is normal, and the CV system 10 is malfunctioning (for example, the hose 106 is disconnected or torn). It can be seen that it is possible to reliably detect.

In addition, even in the engine speed range other than the resonance region R1 of the intake system, the pressure values at the time of failure (cases 1-3) are smaller than the pressure values at normal times, but this difference is due to the resonance region of the intake system. smaller than R1. In this manner, it can be seen that in the present embodiment, a failure in the crankcase ventilation system 10 can be reliably detected by comparing and determining the threshold value A in the resonance region R1 of the intake system, as determined in S2.

Next, in S5, if it is determined that the pressure amplitude P _PP exceeds the predetermined threshold, the process proceeds to S8, and it is determined whether the time in which the pressure amplitude P _PP exceeds the predetermined threshold continues for a predetermined period of time. Determine. In this embodiment, the predetermined time is set to about several seconds (3 to 10 seconds) in order to reliably determine that the crankcase ventilation system is operating normally.
If it is determined in S8 that the time during which the pressure amplitude P _PP exceeds the predetermined threshold continues for a predetermined period of time, the process proceeds to S9 and it is determined that the CV system 10 is operating normally. In this case, notification by the notification device 120 is not performed.

Next, the main effects of the failure diagnosis device for a crankcase ventilation system according to the embodiment of the present invention will be explained.
The failure diagnosis device for the crankcase ventilation system 10 according to the embodiment of the present invention includes a blow-by gas passage 108 that connects the crankcase 8 and the intake passage 36, a pressure sensor 112 that detects the pressure in the blow-by gas passage 108, A diagnostic unit (PCM) 100 that calculates the amplitude of pressure pulsation of the pressure detected by the pressure sensor 112 and diagnoses a failure of the blow-by gas passage 108 based on the calculated amplitude of the pressure pulsation. The unit 100 is configured to perform failure diagnosis of the blow-by gas passage 108 in a resonance rotation speed region (R1) that includes an engine rotation speed that matches the natural frequency of pressure pulsations within the intake passage 36.

According to the embodiment of the present invention configured in this way, the failure diagnosis of the blow-by gas passage 108 is performed in the resonance rotation speed region (R1) including the engine rotation speed that matches the natural frequency of pressure pulsation in the intake passage 36. conduct. In this embodiment, when diagnosing a fault, the pressure pulsations (pressure oscillations/periodic pressure fluctuations) in the resonance state of the intake passage 36 increase the pressure pulsations of the blow-by gas passage 108, so the pressure sensor 112 large pressure pulsations can be detected. Therefore, for example, when a failure such as a poor connection or a hole occurs in the blow-by gas passage 108, the pressure sensor 112 can reliably detect the degree of reduction in pressure pulsation caused by such a failure. As a result, according to the failure diagnosis device for the crankcase ventilation system of this embodiment, the accuracy of failure diagnosis of the blow-by gas passage 108 can be improved.

Further, according to the present embodiment, the diagnostic unit 100 calculates the amplitude of the pressure pulsation based on the difference between the maximum value and the minimum value of the pressure detected by the pressure sensor 112, and calculates the amplitude of the pressure pulsation based on the amplitude of the pressure pulsation. Since a failure is diagnosed, a reduction in pressure pulsation due to a failure can be detected more reliably, regardless of the offset amount of the detected pressure value itself, which is caused by, for example, tolerances (variations due to individual differences) of the pressure sensor 112. I can do it. In other words, when detecting a failure based on the size itself or the average value of the pressure value detected by a pressure sensor, for example, there is a possibility that a failure will be erroneously detected due to variations in the detected value due to the tolerance of the pressure sensor. In this embodiment, such false detection can be suppressed.

Further, according to the present embodiment, since the oil separator 110 is provided in the space 102 within the cylinder head cover 4, the pressure pulsations transmitted from the crankcase 8 side upstream of the oil separator 110 are attenuated by the oil separator 110. be able to. Here, when trying to utilize the increase in pressure pulsations in the resonance rotation speed region of the intake passage 36 as in the present embodiment, the pressure pulsations from the crankcase 8 can become noise. Therefore, according to the present embodiment in which the pressure sensor 112 is provided downstream (on the intake passage side) of the oil separator 110, the S/N ratio of the pressure pulsations detected by the pressure sensor 112 is more reliably increased, and as a result, the The degree of decrease in the pressure pulsation transmitted from 36 can be detected more reliably.

Further, according to the present embodiment, the blow-by gas passage 108 has a first communication passage (first passage) 104 that communicates from the crankcase 8 to the space 102 inside the cylinder head cover 4, and one end 106a inside the cylinder head cover 4. and a second communication passage (second passage) 106 connected to the cylinder head cover 4 so as to communicate with the space 102 of Failure of the blow-by gas passage 108 due to a hole in the second communicating passage 106 made up of a hose, a poor connection to the intake passage 36 (disconnected or disconnected), a poor connection to the head cover 4 (dismounted or disconnected), etc. can be detected more effectively.

Further, according to the present embodiment, the oil separator 110 is provided in the space 102 within the cylinder head cover 4, and the pressure sensor 112 is provided in the cylinder head cover 4 on the downstream side of the oil separator 110. , pressure pulsations transmitted from the crankcase 4 can be attenuated. Therefore, the pressure sensor 112 detects the resonant pressure pulsations from the intake passage 36 while attenuating the pressure pulsations from the crankcase 8 that can become noise, so it can more reliably detect pressure pulsations with a large S/N ratio. Obtainable.

Further, according to the present embodiment, failure diagnosis is prohibited when the opening degree TVO of the throttle valve 54 is smaller than a predetermined set opening degree TVO1 (for example, 20%). Here, when the throttle valve opening degree TVO is small, the pressure pulsation itself in the intake passage 36 becomes small, so the degree of reduction in pressure pulsation when the blow-by gas passage 108 fails also becomes small. Therefore, by prohibiting failure diagnosis when the throttle valve opening degree TVO is smaller than the predetermined set opening degree TVO1, erroneous diagnosis can be suppressed.

Further, according to the present embodiment, the connection position 106b of the blow-by gas passage 108 to the intake passage 36 is a position upstream of the throttle valve 54 of the intake passage 36, and the natural frequency of the pressure pulsation in the intake passage 36 is , which is the natural frequency of the pressure pulsation in the intake passage 36 between the connection position 106b of the blow-by gas passage 108 to the intake passage 36 and the position of the intake valve 28, so that the pressure pulsation in the blow-by gas passage 108 can be more effectively suppressed. can be increased, thereby improving the accuracy of failure diagnosis of the blow-by gas passage 108.

1 Engine 2 Cylinder head 4 Cylinder head cover 6 Cylinder block 8 Crankcase 10 Crankcase ventilation system (CV system)
12 Cylinder 14 Piston 18 Crankshaft 20 Piston cavity/combustion chamber 22 Engine speed sensor 24 Intake port 26 Exhaust port 28 Intake valve 30 Exhaust valve 32 Injector 34 Variable valve lift mechanism (VVL)
36 Intake passage 38 Exhaust passage 46 Exhaust turbo supercharger 48 Compressor 50 Turbine 52 Intercooler 54 Throttle valve 56 Throttle valve opening sensor 64 Exhaust purification device 66 Particulate filter 68 Oxidation catalyst 70 Lean NOx catalyst 76, 78 EGR device 80 High pressure EGR passage 82 Low pressure EGR passage 84 Cooler side passage 86 Cooler bypass side passage 90 Cooler side EGR valve/first high pressure EGR valve (HP-EGR valve)
91 Cooler side EGR valve opening sensor 92 Cooler bypass side EGR valve/second high pressure EGR valve (HP-EGR valve)
93 Cooler bypass side EGR valve opening sensor 96 Low pressure EGR valve (LP-EGR valve)
97 Low pressure EGR valve opening sensor 100 PCM/control unit/failure diagnosis unit 102 Space inside head cover (blow-by gas passage)
102a Space on one side 102b Space on the other side 104 First communication passage (blow-by gas passage)
106 Second communication path/hose (blow-by gas path)
106a One end of the second communication path/attachment part (connection part) to the cylinder head cover 4
106b The other end of the second communication passage/attachment part (connection part) to the intake passage 36
108 Blow-by gas passage 110 Oil separator 112 Pressure sensor

Claims (7)

a blow-by gas passage connecting the crankcase and the intake passage;
a pressure sensor that detects the pressure in the blow-by gas passage;
A crankcase for an engine, comprising: a diagnostic unit that calculates the amplitude of pressure pulsation of the pressure detected by the pressure sensor and diagnoses a failure in the blow-by gas passage based on the calculated amplitude of the pressure pulsation. A ventilation system failure diagnosis device,
The diagnostic unit is characterized in that it is configured to perform a failure diagnosis of the blow-by gas passage in a resonance rotational speed region that includes an engine rotational speed that matches the natural frequency of pressure pulsation in the intake passageway. Fault diagnosis device for crankcase ventilation system. The failure diagnosis device for a crankcase ventilation system according to claim 1, wherein the diagnosis unit calculates the amplitude of the pressure pulsation based on a difference between a maximum value and a minimum value of pressure detected by the pressure sensor. The blow-by gas passage is provided to communicate with the intake passage from the crankcase via a space within the cylinder head cover,
An oil separator is provided in the space inside the cylinder head cover,
3. The failure diagnosis device for a crankcase ventilation system according to claim 1, wherein the pressure sensor is provided downstream of the oil separator in the blow-by gas passage. The blow-by gas passage has a first passage communicating from the crankcase to the space inside the cylinder head cover, one end connected to the cylinder head cover so as to communicate with the space inside the cylinder head cover, and the other end connected to the intake passage. a second passage connected to the
The failure diagnosis device for a crankcase ventilation system according to any one of claims 1 to 3, wherein the pressure sensor is provided on the cylinder head cover. An oil separator is provided in the space inside the cylinder head cover,
5. The failure diagnosis device for a crankcase ventilation system according to claim 4, wherein the pressure sensor is provided on the cylinder head cover downstream of the oil separator. 6. The failure diagnosis device for a crankcase ventilation system according to claim 1, wherein the diagnosis unit prohibits the failure diagnosis when the throttle valve opening is smaller than a predetermined opening. The connection position of the blow-by gas passage to the intake passage is a position upstream of the throttle valve of the intake passage,
Claim 1: The natural frequency of the pressure pulsations in the intake passage is the natural frequency of the pressure pulsations in the intake passage between a connection position of the blow-by gas passage to the intake passage and a position of the intake valve. 7. A failure diagnosis device for a crankcase ventilation system according to any one of items 6 to 6.

Images