PCV flow path leak detection device and vehicle

Abstract

To provide a leak detection device for a PCV flow passage and a vehicle that can isolate a pressure sensor for performing leak detection of blow-by gas, from a corrosive environment to the extent possible.SOLUTION: A leak detection device for a PCV flow passage according to an embodiment of the present disclosure performs leak detection of the PCV flow passage including at least a fresh air line for establishing communication between a crank chamber and an intake air passage constituting an engine, and includes: a pressure sensor communicating with the PCV flow passage, and capable of detecting a pressure in the PCV flow passage; a leak determination unit for determining the presence or absence of a leak of the PCV flow passage on the basis of the pressure in the PCV flow passage when the PCV flow passage is blocked; and an isolation mechanism for isolating the pressure sensor from the PCV flow passage except when determining the presence or absence of a leak of the PCV flow passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a leak detection device that detects a leak occurring in a flow path in a PCV circuit mounted on, for example, a gasoline engine. [Background technology]

[0002] Conventionally, automobile engines have been equipped with a PCV (Positive Crankcase Ventilation) circuit to guide blow-by gas that leaks into the crankcase from the combustion chamber through the gap between the cylinder and piston into the intake passage.

[0003] If a leak occurs in the flow path of the PCV circuit (also called the "PCV flow path") through which the blow-by gas flows for some reason, the blow-by gas will be released into the atmosphere outside the engine. Therefore, for example, Patent Document 1 proposes a technology that measures the pressure inside the crankcase to detect a leak in the PCV flow path and detects the leak based on this pressure.

[0004] Similarly, the leak detection device in Patent Document 2 proposes a pressure sensor attached to the crankcase to measure the pressure inside the crank chamber, and a pressure sensor attached to the intake manifold to measure the pressure inside the intake manifold. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-117176 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-166449 Summary of the Invention [Problem to be solved by the invention]

[0006] However, current technologies, including those described in the above patent documents, cannot be said to satisfy the potential needs for leak detection, and the following problems exist. For example, in the above-mentioned patent document, although highly accurate leak detection is possible in that leak diagnosis is performed based on pressure fluctuations using a pressure sensor, the pressure sensor is exposed to a corrosive environment because blow-by gas flows through the PCV circuit. Since corrosion of such a pressure sensor can result in measurement abnormalities, it is desirable for the above-mentioned leak detection to isolate the pressure sensor from the corrosive environment as much as possible.

[0007] The present disclosure has been made in consideration of the above-mentioned problems as an example, and aims to provide a PCV flow path leak detection device and a vehicle that can isolate a pressure sensor that detects blow-by gas leaks from a corrosive environment as much as possible. [Means for solving the problem]

[0008] In order to solve the above problems, a PCV flow path leak detection device in one embodiment of the present disclosure is a leak detection device that detects leaks in a PCV flow path that includes at least a fresh air line that communicates between a crank chamber that constitutes an engine and an intake flow path, and includes a pressure sensor that communicates with the PCV flow path and is capable of detecting the pressure within the PCV flow path, a leak determination unit that determines whether or not there is a leak in the PCV flow path based on the pressure within the PCV flow path when the PCV flow path is blocked, and a blocking mechanism that blocks the pressure sensor from the PCV flow path except when determining whether or not there is a leak.

[0009] In order to solve the above problems, the vehicle according to the present disclosure is equipped with the engine and PCV flow path leak detection device. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to isolate the pressure sensor that detects the leakage of blow-by gas from a corrosive environment as much as possible. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a fresh air line of an engine mounted on a vehicle according to an embodiment; [Figure 2] 1 is a schematic diagram of an engine equipped with a leak detection device according to an embodiment. [Figure 3] FIG. 2 is a schematic diagram showing a detailed structure of the leak detection device according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing the flow of blow-by gas in the supercharging operation range. [Figure 5] FIG. 2 is an explanatory diagram showing the flow of blow-by gas in the non-supercharged (naturally aspirated) operation range. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, preferred embodiments for implementing the present disclosure will be described. The dimensions, materials, and other design specifications shown in these embodiments are merely examples for facilitating understanding of the present disclosure and do not limit the present disclosure unless otherwise specified. Note that configurations other than those described in detail below can be implemented by appropriately supplementing known engine structures, such as those described in JP 2017-166449 A.

[0013] [Engine 10] First, the configuration of an engine 10 mounted on a vehicle in a preferred embodiment of the present disclosure will be described with reference to Figures 1 and 2. Note that examples of vehicles suitable for this embodiment include two-wheeled vehicles and four-wheeled vehicles equipped with a known transmission, and may also be known hybrid vehicles equipped with an electric motor.

[0014] The engine 10 of this embodiment may be a horizontally opposed four-cylinder engine in which cylinder bores 13 formed in two cylinder blocks 12 are arranged opposite each other across a crankshaft 11. A crankcase 14 is integrally formed with the cylinder blocks 12. A cylinder head 15 is fixedly disposed on the cylinder block 12 on the side opposite the crankcase 14.

[0015] The crankshaft 11 is rotatably supported via known bearings in the crank chamber CR defined by the crankcase 14. A piston 18 connected to the crankshaft 11 via a connecting rod 17 is slidably provided in the cylinder bore 13. Therefore, the space surrounded by the cylinder bore 13, the cylinder head 15, and the crown surface of the piston 18 functions as a combustion chamber 19 of the engine 10 in this embodiment.

[0016] An intake port 20 and an exhaust port 21 are formed in the cylinder head 15 so as to communicate with the combustion chamber 19. The tip of an intake valve 22 is positioned between the intake port 20 and the combustion chamber 19. The tip of an exhaust valve 23 is positioned between the exhaust port 21 and the combustion chamber 19. A well-known intake valve cam 25 and exhaust valve cam 26 are provided in a cam chamber surrounded by the cylinder head 15 and the head cover 24.

[0017] Of these, the intake valve cam 25 abuts against the other end of the intake valve 22 and rotates under the action of the intake camshaft, thereby moving the intake valve 22 back and forth in the axial direction. On the other hand, the exhaust valve cam 26 abuts against the other end of the exhaust valve 23 and rotates under the action of the exhaust camshaft, thereby moving the exhaust valve 23 back and forth in the axial direction.

[0018] 2, an intake passage 28 including a known intake manifold 27 is connected to the upstream side of the intake port 20 of this embodiment. This intake passage 28 is provided with a known air cleaner 32, a compressor 31b of a turbocharger 31, an intercooler 33, a throttle valve 34, and the like.

[0019] The downstream side of the exhaust port 21 of this embodiment is connected to an exhaust flow path 30 including a known exhaust manifold 29. As described above, the engine 10 of this embodiment is configured to include a known turbocharger 31. Therefore, the exhaust gas discharged from the combustion chamber 19 passes through the exhaust port 21, is collected in the exhaust manifold 29, and then is guided to the turbocharger 31.

[0020] The exhaust gas generated by this combustion is guided to the turbine 31a of the turbocharger 31 via the exhaust port 21 and the exhaust manifold 29. After the turbocharger 31 rotates the turbine 31a, the exhaust gas is purified by a known catalyst 35 provided in the exhaust flow path 30 and then discharged outside the vehicle.

[0021] The engine 10 of this embodiment also has a fresh air line 36A that guides air (fresh air) to the crankcase 14. The fresh air line 36A communicates, for example, between the air cleaner 32 and the compressor 31b in the intake flow path 28 and the crank chamber CR formed in the crankcase 14. There are no particular restrictions on the material of the fresh air line 36A, and a known material used for fresh air lines, such as that disclosed in JP 2017-166449 A, may be used.

[0022] The fresh air line 36A and the intake flow path 28 are connected via a first flow path opening / closing valve 102. This allows a control device (leak determination unit 120) described below to block or connect the fresh air line 36A to the intake flow path 28 via the first flow path opening / closing valve 102. Note that various known valve mechanisms capable of blocking the flow of gas may be applied as the first flow path opening / closing valve 102.

[0023] The engine 10 of this embodiment also has a scavenging line 37 for scavenging blow-by gas present in the crank chamber CR formed in the crankcase 14. Such scavenging line 37 connects the crank chamber CR with the intake manifold 27. There are no particular restrictions on the material of the scavenging line 37, and known materials used for scavenging lines, such as those disclosed in Japanese Patent Application Laid-Open No. 2017-166449, may be used.

[0024] 2, a second flow path opening / closing valve 104 is provided at a connection between the scavenging line 37 and the crank chamber CR, for connecting or blocking the scavenging line 37 to the crank chamber CR. As with the first flow path opening / closing valve 102 described above, various known valve mechanisms capable of blocking the flow of gas may be applied as the second flow path opening / closing valve 104.

[0025] A known oil catch tank 38 is provided below the turbocharger 31. Oil stored in this oil catch tank 38 is sucked by a known scavenge pump 39 and returned to the oil pan of the engine 10 via a suction line 40. The oil catch tank 38 is also connected to a crank chamber CR formed in the crankcase 14 by a balance line 41.

[0026] The balance line 41 has the function of equalizing the pressure in the oil catch tank 38 with the pressure in the crank chamber by connecting the crank chamber CR with the oil catch tank 38. The balance line 41, together with the fresh air line 36A and the scavenging air line 37, constitutes the PCV system in the engine 10. Therefore, in this embodiment, the flow path formed by the fresh air line 36A, the scavenging line 37, and the balance line 41 is defined as a PCV flow path.

[0027] <Leak detection device 100> Next, the configuration of the leak detection device 100 will be described with reference to Figure 3. The leak detection device 100 is configured to have the function of detecting leaks in the PCV flow path that includes at least the fresh air line 36A that connects the crank chamber CR and the intake flow path 28 that constitute the engine 10 described above.

[0028] More specifically, the leak detection device 100 of this embodiment includes the first flow path opening / closing valve 102, the pressure sensor 110, the leak determination unit 120, and the cutoff mechanism 130. The pressure sensor 110 is connected to the PCV flow path and has a function of detecting the pressure in the PCV flow path. There are no particular limitations on the pressure sensor 110, and any known pressure sensor may be used.

[0029] 3, the pressure sensor 110 of this embodiment is provided in a branch line 36B that branches off from the fresh air line 36A. In this way, the branch line 36B of this embodiment is provided branching off from the fresh air line 36A, so that the pressure in the fresh air line 36A can be measured via the branch line 36B.

[0030] As shown in the figure, the branch line 36B of this embodiment is provided with an opening 36Ba with a reduced flow path diameter. This opening 36Ba is formed in the inner wall of the branch line 36B so that a plug member 132 (described later) can close it from the fresh air line 36A side.

[0031] The leak determination unit 120 has a function of determining whether or not there is a leak in the PCV flow path based on the pressure in the PCV flow path when the PCV flow path is blocked. Such a leak determination unit 120 may be configured as a control device including one or more electronic control units (ECUs).

[0032] The structure of the control device is not limited to the above, and may be configured, for example, by a known computer having one or more processors such as a CPU (Central Processing Unit) and one or more memories such as RAM (Random Access Memory) or ROM (Read Only Memory) communicably connected to the processor. Also, part or all of the above-mentioned control device may be configured with updatable firmware or the like, or may be a program module executed by instructions from the processor.

[0033] The cutoff mechanism 130 is configured to have a function of cutting off the pressure sensor 110 from the PCV flow path except when the leak determination unit 120 is determining whether or not there is a leak. More specifically, the cutoff mechanism 130 of this embodiment includes a one-way valve 131 provided upstream of the pressure sensor 110 in the branch line 36B, as can be seen from FIG.

[0034] As will be described later, the one-way valve 131 is configured to be in an open state when the fresh air line 36A is in a negative pressure state and to be in a closed state when the fresh air line 36A is in a positive pressure state. More specifically, the one-way valve 131 of this embodiment is configured to include an opening 36Ba as a valve seat provided on the inner wall of the branch line 36B, a plug member 132 as a valve body that closes or opens the opening 36Ba, and an elasticity imparting member 133 that is connected to the plug member 132 and presses the plug member 132 against the opening 36Ba.

[0035] 3, the elasticity applying member 133 is provided on the bottom surface 36Bb of the branch line 36B and applies pressure to the plug member 132 attached to the tip side so as to pull it toward the opening 36Ba. A known elastic spring, for example, can be used as the elasticity applying member 133. In this embodiment, the plug member 132 closes the opening 36Ba due to the action of the elasticity applying member 133, unless a negative pressure state occurs inside the fresh air line 36A (described later).

[0036] In this embodiment, for example, when the fresh air line 36A is blocked from the intake flow path 28 via the first flow path opening / closing valve 102 and the fresh air line 36A is placed under negative pressure, the plug member 132 is disengaged from the opening 36Ba by the action of this negative pressure, thereby connecting the pressure sensor 110 to the fresh air line 36A.

[0037] In other words, in the leak detection device 100 of this embodiment, when detecting a blow-by gas leak, the pressure sensor 110 is connected to the fresh air line 36A only when the fresh air line 36A is brought into a negative pressure state via the first flow path opening / closing valve 102, and the pressure sensor 110 can be isolated from the fresh air line 36A except when the above-mentioned leak detection is being performed.

[0038] This makes it possible to isolate the pressure sensor 110, which detects blow-by gas leaks, from the corrosive environment as much as possible, thereby preventing a decrease in the accuracy of leak detection and reducing the frequency of maintenance.

[0039] In this embodiment, as shown in FIG. 3, a branch line 36B is provided to the fresh air line 36A, and the pressure sensor 110 is arranged in the branch line 36B via the blocking mechanism 130. However, the leak detection device 100 of this embodiment may be applied to any part that is constantly in communication with the internal pressure of the crankshaft.

[0040] <Blow-by gas flow during turbocharged and non-turbocharged (naturally aspirated) operation> Next, the timing of leak detection in this embodiment will be explained using the flow state of blow-by gas during supercharged operation and non-supercharged (naturally aspirated) operation. Note that non-supercharged operation in this embodiment also includes naturally aspirated operation of an engine that is not equipped with a supercharger 31.

[0041] That is, the above-mentioned fresh air line 36A and scavenging line 37 are mainly used to discharge blow-by gas from inside the crankcase CR. Here, the direction of the blow-by gas flowing through the fresh air line 36A and the scavenging line 37 differs depending on whether the engine 10 is operating in a non-supercharged (naturally aspirated) state where the intake air to the engine 10 is not supercharged or in a supercharged state where the intake air is supercharged by the supercharger 31. The following description will continue using the fresh air line 36A of the PCV flow path as an example.

[0042] That is, first, during the above-described supercharging operation, as shown in Fig. 4, the internal pressure generated in the intake manifold 27 increases due to the supercharging action of the supercharger 31. Therefore, the internal pressure of the crank chamber CR also becomes higher than that of the fresh air line 36A, fresh air cannot flow from the intake passage 28 to the fresh air line 36A, air flows back from the crankcase 14, and blow-by gas inside the crankcase 14 cannot be collected.

[0043] That is, in the supercharged state described above, if the first flow path opening / closing valve 102 is open, there is a possibility that blow-by gas in the crankcase 14 will flow into the fresh air line 36A, and if the first flow path opening / closing valve 102 is closed, there is a possibility that the internal pressure of the fresh air line 36A will increase. Therefore, even if leak detection is attempted in this supercharged state, if the first flow path opening / closing valve 102 is open, contamination of the pressure sensor 110 by blow-by gas will progress, and if the first flow path opening / closing valve 102 is closed, the plug member 132 will be maintained in a closed state in which it is pressed against the opening 36Ba.

[0044] On the other hand, during the non-supercharged (naturally aspirated) operation described above, as shown in Figure 5, the internal pressure in the intake manifold 27 is not higher than that described above, and the piston movement in the engine 10 causes the pressure inside the crankcase 14 to become negative relative to the fresh air line 36A.

[0045] That is, when the engine 10 is in a non-supercharged (naturally aspirated) state, scavenging is possible through the scavenging line 37 when the first flow path opening / closing valve 102 is open, and blow-by gas in the crankcase 14 flows out to the scavenging line 37, while fresh air (new air) is introduced into the crankcase 14 from the intake flow path 28 via the fresh air line 36A.

[0046] Therefore, during non-supercharged (naturally aspirated) operation, air containing blow-by gas does not flow back from the crankcase 14 into the fresh air line 36A, and the leak determination unit 120 can detect blow-by gas leaks during the above-mentioned non-supercharged (naturally aspirated) operation. That is, when the leak determination unit 120 detects the above-mentioned leak, it first controls the first flow path opening / closing valve 102 to close the first flow path opening / closing valve 102 .

[0047] When the first flow path opening / closing valve 102 is closed, the fresh air line 36A is put into a negative pressure state, and the plug member 132 is removed from the opening 36Ba against the elastic force of the elasticity imparting member 133. This places the fresh air line 36A and the pressure sensor 110 in communication via the branch line 36B, making it possible to measure the pressure value in the fresh air line 36A (PCV flow path).

[0048] If the pressure value measured by the pressure sensor 110 at this time is equal to or greater than a predetermined value, the leak determination unit 120 can determine that a leak may be occurring in the PCV flow path due to some factor. On the other hand, if the pressure value measured by the pressure sensor 110 drops to a predetermined value, the leak determination unit 120 can determine that there is no leak in the PCV flow path. The predetermined value may vary depending on the number of cylinders and specifications of the engine 10, but can be set in advance through experiments, simulations, or the like.

[0049] As described above, with the leak detection device 100 of this embodiment and the vehicle equipped with the leak detection device 100, the pressure sensor 110 is placed in a blow-by gas environment only when detecting a blow-by gas leak, thereby isolating the pressure sensor from corrosion as much as possible.

[0050] Although the preferred embodiments and modifications of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the present disclosure may attempt further modifications to these embodiments and modifications within the scope of the technical ideas set forth in the claims, and it is understood that these modifications also naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0051] 10 Engine 28 Intake passage 36A Fresh Air Line 36B Branch Line 100 Leak Detection Device 110 Pressure Sensor 120 Leak detection unit 130 Shut-off mechanism 131 One-way valve 132 Plug member 133 Elasticity imparting member

Claims

1. A leak detection device for detecting a leak in a PCV flow path including at least a fresh air line that connects a crank chamber and an intake flow path of an engine, a pressure sensor communicating with the PCV flow path and capable of detecting the pressure in the PCV flow path; a leak determination unit that determines whether or not there is a leak in the PCV flow path based on the pressure in the PCV flow path when the PCV flow path is blocked; a blocking mechanism that blocks the pressure sensor from the PCV flow path except when determining whether or not there is a leak; A leak detection device comprising:

2. 2. The leak detection device according to claim 1, wherein the pressure sensor is provided in a branch line branching from the fresh air line in the PCV flow path.

3. The blocking mechanism includes: a one-way valve provided in the branch line upstream of the pressure sensor, the one-way valve being opened when the fresh air line is in a negative pressure state and being closed when the fresh air line is in a positive pressure state; The leak detection device of claim 2 .

4. The one-way valve is a plug member for closing or opening an opening provided in an inner wall of the branch line; an elasticity imparting member connected to the plug member and pressing the plug member against the opening; comprising: The leak detection device of claim 3 .

5. A vehicle equipped with the leak detection device according to any one of claims 1 to 4.

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