PCV System

Abstract

To provide a technology which can reduce a pressure variation width of a blow-by gas transmitted to a PCV valve.SOLUTION: A PCV system includes: a single-cylinder or two-cylinder engine; an intake passage connected to the engine; a PCV passage which is connected to the engine and the intake passage and used to send a blow-by gas from the engine to the intake passage; and a PCV valve disposed in the PCV passage. The PCV passage includes: an upstream passage between the engine and the PCV valve; and a downstream passage between the PCV valve and the intake passage. The upstream passage includes: a first passage; and a second passage arranged parallel to the first passage. A chamber may be provided in at least one of the first passage and the second passage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a PCV system.

Background Art

[0002] The system disclosed in Patent Document 1 includes an engine, an intake passage connected to the engine, a PCV passage (referred to as a "BGV passage" in Patent Document 1) connected to the engine and the intake passage, and a PCV valve disposed in the PCV passage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the system of Patent Document 1, when the engine operates, the piston moves up and down, causing the pressure in the PCV passage to fluctuate. For example, when the piston descends, the pressure in the PCV passage increases, and when the piston ascends, the pressure in the PCV passage decreases.

[0005] In this case, if the engine is a single-cylinder or two-cylinder engine, the pressure fluctuation range within the PCV passage may be large. More specifically, if the engine has three or more cylinders, the different phases of the up-and-down motion of the pistons in each cylinder cause the pressure fluctuations due to the up-and-down motion of each piston to cancel each other out, thus suppressing the pressure fluctuation range within the PCV passage. However, in the case of a single-cylinder engine, this cancellation of pressure fluctuations does not occur, so the pressure fluctuation range within the PCV passage is not suppressed. Also, in the case of a two-cylinder engine, if the phases of the up-and-down motion of the pistons in each cylinder are the same, the pressure fluctuation range within the PCV passage may be large. As a result, the pressure fluctuation range of the blow-by gas transmitted to the PCV valve may be large.

[0006] Therefore, this specification provides a technology that can suppress the pressure fluctuation range of blow-by gas transmitted to the PCV valve. [Means for solving the problem]

[0007] In a first aspect of this technology, the PCV system comprises a single-cylinder or two-cylinder engine, an intake passage connected to the engine, a PCV passage connected to the engine and the intake passage for supplying blow-by gas from the engine to the intake passage, and a PCV valve disposed in the PCV passage. The PCV passage may comprise an upstream passage between the engine and the PCV valve, and a downstream passage between the PCV valve and the intake passage. The upstream passage may comprise a first passage and a second passage parallel to the first passage. A chamber may be provided in at least one of the first passage and the second passage.

[0008] In this configuration, the presence of a chamber in the passage through which blow-by gas flows changes the phase of pressure fluctuations of the blow-by gas within that passage. This allows the phases of pressure fluctuations in the first passage and the second passage to be shifted. As a result, the pressure fluctuations of the blow-by gas in the upstream passage can be canceled out, and the range of pressure fluctuations of the blow-by gas transmitted to the PCV valve can be suppressed.

[0009] In a second embodiment, the diameters of the first passage and the second passage may be different in the first embodiment. In this case, chambers may not be provided in both the first and second passages.

[0010] With this configuration, the diameters of the first passage and the second passage through which the blow-by gas flows are different, which allows the phase of the blow-by gas pressure fluctuations in the first passage and the phase of the blow-by gas pressure fluctuations in the second passage to be shifted. As a result, the blow-by gas pressure fluctuations in the upstream passage can be canceled out, and the range of blow-by gas pressure fluctuations transmitted to the PCV valve can be suppressed.

[0011] In a third embodiment, the lengths of the first passage and the second passage may be different in the first or second embodiment. In this case, chambers may not be provided in both the first and second passages.

[0012] With this configuration, the lengths of the first passage and the second passage through which the blow-by gas flows are different, which allows the phase of the blow-by gas pressure fluctuations in the first passage and the phase of the blow-by gas pressure fluctuations in the second passage to be shifted. As a result, the blow-by gas pressure fluctuations in the upstream passage can be canceled out, and the range of blow-by gas pressure fluctuations transmitted to the PCV valve can be suppressed.

[0013] In the fourth embodiment, in any of the first to third embodiments, chambers may be provided in both the first passage and the second passage. The volume of the chamber provided in the first passage and the volume of the chamber provided in the second passage may be different.

[0014] With this configuration, the volume of the chamber in the first passage and the volume of the chamber in the second passage are different, which allows the phase of the blow-by gas pressure fluctuations in the first passage and the phase of the blow-by gas pressure fluctuations in the second passage to be shifted. As a result, the blow-by gas pressure fluctuations in the upstream passage can be canceled out, and the range of blow-by gas pressure fluctuations transmitted to the PCV valve can be suppressed.

[0015] In the fifth embodiment, in any of the first to fourth embodiments, chambers may be provided in both the first passage and the second passage. The distance from the engine to the chamber in the first passage may be different from the distance from the engine to the chamber in the second passage.

[0016] With this configuration, the distance from the engine to the chamber in the first passage and the distance from the engine to the chamber in the second passage are different, which allows the phase of the blow-by gas pressure fluctuations in the first passage and the phase of the blow-by gas pressure fluctuations in the second passage to be shifted. As a result, the blow-by gas pressure fluctuations in the upstream passage can be canceled out, and the range of blow-by gas pressure fluctuations transmitted to the PCV valve can be suppressed.

[0017] In the sixth embodiment, the volume of the chamber provided in the first passage and the volume of the chamber provided in the second passage may be the same as in the fifth embodiment.

[0018] This configuration allows for the suppression of pressure fluctuations in blow-by gas transmitted to the PCV valve with a simple design.

[0019] In a seventh aspect, in any one of the first to sixth aspects, the PCV valve may be disposed closer to the intake passage side than the central portion in the longitudinal direction of the PCV passage.

[0020] According to this configuration, since the PCV valve is away from the engine, the attenuation of the pressure fluctuation of the blow-by gas is increased. Therefore, the pressure fluctuation width of the blow-by gas transmitted to the PCV valve can be suppressed.

Brief Description of the Drawings

[0021] [Figure 1] A diagram schematically showing the PCV system of the embodiment. [Figure 2] A diagram schematically showing the upstream passage of the embodiment. [Figure 3] A diagram showing an example of the pressure fluctuation of the blow-by gas. [Figure 4] A diagram schematically showing the upstream passage of the modification. [Figure 5] A diagram schematically showing the upstream passage of another modification.

Modes for Carrying Out the Invention

[0022] The PCV system of the embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically showing the PCV system 2 of the embodiment. As shown in FIG. 1, the PCV system 2 includes an engine 4, an intake passage 10, an exhaust passage 20, a PCV (Positive Crankcase Ventilation) passage 30, and a fresh air passage 90. The PCV system 2 is a system for refluxing the blow-by gas generated in the engine 4 to the intake passage 10. [[ID=​The engine 4 of the PCV system 2 is a single-cylinder or twin-cylinder engine. The engine 4 comprises a cylinder block 40, a crankcase 42, a head cover 44, a piston 46, and a crankshaft 48. The cylinder block 40 comprises one or two cylinders 60, a plurality of connecting passages 64, an intake port 12, and an exhaust port 22. The following description will be based on a single cylinder 60.

[0024] A piston 46 is housed in the cylinder 60 of the cylinder block 40. A combustion chamber 62 is formed in the area enclosed by the piston 46 and the cylinder 60. A mixture of air and fuel burns in the combustion chamber 62, and the energy from this combustion causes the piston 46 to move up and down (reciprocate) within the cylinder 60. The piston 46 is connected to the crankshaft 48 via a connecting rod 47, and the crankshaft 48 rotates as the piston 46 moves up and down.

[0025] Multiple connecting passages 64 are provided next to the cylinder 60. The connecting passages 64 connect the space inside the crankcase 42 to the space enclosed by the head cover 44.

[0026] The intake port 12 communicates with the combustion chamber 62, and air is introduced into the combustion chamber 62 through the intake port 12. An intake valve 14 is located in the intake port 12 to open and close the intake port 12. The exhaust port 22 communicates with the combustion chamber 62, and exhaust gas generated in the combustion chamber 62 is discharged through the exhaust port 22. An exhaust valve 24 is located in the exhaust port 22 to open and close the exhaust port 22.

[0027] The crankcase 42 is fixed to the lower end of the cylinder block 40. The crankshaft 48 is housed in the crankcase 42. In the PCV system 2, some of the exhaust gas generated in the combustion chamber 62 of the engine 4 leaks into the crankcase 42 through the gap between the piston 46 and the cylinder 60. The exhaust gas that leaks into the crankcase 42 is called blow-by gas.

[0028] The head cover 44 is fixed to the upper end of the cylinder block 40. The space enclosed by the head cover 44 communicates with the space inside the crankcase 42 via a communication passage 64. A portion of the blow-by gas from inside the crankcase 42 flows into the space enclosed by the head cover 44 through the communication passage 64.

[0029] Next, the intake passage 10, exhaust passage 20, PCV passage 30, and fresh air passage 90 connected to the engine 4 will be described. The intake passage 10 is connected to the intake port 12 of the engine 4. The downstream end of the intake passage 10 is connected to the intake port 12, and the upstream end of the intake passage 10 is open to the atmosphere. The intake passage 10 is a passage for supplying air from the atmosphere to the combustion chamber 62 of the engine 4. A throttle valve 16 is located in the intake passage 10 to adjust the passage cross-sectional area of ​​the intake passage 10. By adjusting the opening of the throttle valve 16, the amount of air supplied to the engine 4 is adjusted.

[0030] The exhaust passage 20 is connected to the exhaust port 22 of the engine 4. The upstream end of the exhaust passage 20 is connected to the exhaust port 22, and the downstream end of the exhaust passage 20 is open to the atmosphere. The exhaust passage 20 is a passage for discharging exhaust gas generated by the engine 4 to the outside. For example, a filter (not shown) for purifying the exhaust gas is placed in the exhaust passage 20.

[0031] The PCV passage 30 is connected to the crankcase 42 and the intake passage 10 of the engine 4. The upstream end of the PCV passage 30 is connected to the crankcase 42, and the downstream end of the PCV passage 30 is connected to the intake passage 10. The downstream end of the PCV passage 30 is connected to the intake passage 10 downstream of the throttle valve 16 (i.e., on the intake port 12 side of the engine 4). The PCV passage 30 is a passage for sending blow-by gas from the crankcase 42 to the intake passage 10. A PCV valve 50 is located in the PCV passage 30.

[0032] In the example shown in Figure 1, the PCV valve 50 is located upstream of the longitudinal center of the PCV passage 30 (i.e., towards the crankcase 42). In a modified example, the PCV valve 50 may be located downstream of the longitudinal center of the PCV passage 30 (i.e., towards the intake passage 10). That is, in the modified example, the PCV valve 50 is located closer to the intake passage 10 than to the crankcase 42 in the longitudinal direction of the PCV passage 30. In the modified example, the length of the PCV passage 30 from the upstream end (i.e., from the crankcase 42) to the PCV valve 50 is longer than the length of the PCV passage 30 from the PCV valve 50 to the downstream end (i.e., to the intake passage 10).

[0033] The PCV valve 50 opens and closes the PCV passage 30. When the PCV valve 50 is open, blow-by gas from the crankcase 42 is sent to the intake passage 10. When the PCV valve 50 is closed, blow-by gas is no longer sent to the intake passage 10. The PCV valve 50 opens and closes, for example, based on a command from the ECU (Engine Control Unit).

[0034] The PCV passage 30 comprises an upstream passage 32 between the crankcase 42 and the PCV valve 50, and a downstream passage 34 between the PCV valve 50 and the intake passage 10. The upstream end of the upstream passage 32 is connected to the crankcase 42, and the downstream end of the upstream passage 32 is connected to the PCV valve 50. The upstream end of the downstream passage 34 is connected to the PCV valve 50, and the downstream end of the downstream passage 34 is connected to the intake passage 10.

[0035] As shown in Figure 2, the upstream passage 32 comprises a case-side passage 36 connected to the crankcase 42, a valve-side passage 38 connected to the PCV valve 50, and a first passage 70 and a second passage 72 located between the case-side passage 36 and the valve-side passage 38. The first passage 70 and the second passage 72 branch off from the case-side passage 36 and merge into the valve-side passage 38. The first passage 70 and the second passage 72 are arranged in parallel with each other. The blow-by gas flowing through the case-side passage 36 is divided into the first passage 70 and the second passage 72. The blow-by gas flowing through the first passage 70 and the second passage 72 merge in the valve-side passage 38.

[0036] A first chamber 52 is provided in the first passage 70. The first chamber 52 has a larger volume than the first passage 70. In a cross-section perpendicular to the longitudinal direction of the first passage 70, the cross-sectional area of ​​the first chamber 52 is larger than the cross-sectional area of ​​the first passage 70.

[0037] A second chamber 54 is provided in the second passage 72. The second chamber 54 has a larger volume than the second passage 72. In a cross-section perpendicular to the longitudinal direction of the second passage 72, the cross-sectional area of ​​the second chamber 54 is larger than the cross-sectional area of ​​the second passage 72. The volume of the second chamber 54 is smaller than the volume of the first chamber 52.

[0038] As shown in Figure 1, the fresh air passage 90 is connected to the intake passage 10 and the head cover 44 of the engine 4. The upstream end of the fresh air passage 90 is connected to the intake passage 10, and the downstream end of the fresh air passage 90 is connected to the head cover 44. The upstream end of the fresh air passage 90 is connected to the intake passage 10 upstream of the throttle valve 16 (i.e., on the atmospheric side). The fresh air passage 90 is a passage for supplying a portion of the air flowing through the intake passage 10 to the space enclosed by the head cover 44. An on / off valve 92 is provided in the fresh air passage 90 to open and close the fresh air passage 90. When the on / off valve 92 is opened, air is sent to the space enclosed by the head cover 44.

[0039] In the PCV system 2 described above, when the engine 4 operates, the piston 46 moves up and down (reciprocates), causing the pressure of the blow-by gas in the crankcase 42 to fluctuate, and consequently, the pressure in the PCV passage 30 may fluctuate. For example, when the piston 46 moves down, the pressure in the PCV passage 30 increases, and when the piston 46 moves up, the pressure in the PCV passage 30 decreases. That is, as shown in Figure 3, the pressure in the PCV passage 30 is high when the crank angle is 0° + 360° × n (n = an integer greater than or equal to 0), and low when the crank angle is 180° + 360° × n (n = an integer greater than or equal to 0).

[0040] (effect) The PCV system 2 of the embodiment has been described above. As is clear from the above description, the PCV system 2 includes a PCV passage 30 that sends blow-by gas from the engine 4 to the intake passage 10, and a PCV valve 50 located in the PCV passage 30. The PCV passage 30 includes an upstream passage 32 between the engine 4 and the PCV valve 50, and a downstream passage 34 between the PCV valve 50 and the intake passage 10. The upstream passage 32 includes a parallel first passage 70 and a second passage 72. In the PCV system 2, the volume of the first chamber 52 provided in the first passage 70 and the volume of the second chamber 54 provided in the second passage 72 are different.

[0041] With this configuration, the configuration of the first passage 70 and the configuration of the second passage 72 are asymmetrical due to the first chamber 52 and the second chamber 54, so that the phase of the blow-by gas pressure fluctuations in the first passage and the phase of the blow-by gas pressure fluctuations in the second passage can be shifted. As a result, the blow-by gas pressure fluctuations can be canceled out in the upstream passage 32, and the range of blow-by gas pressure fluctuations transmitted to the PCV valve 50 can be suppressed. If the engine 4 is a single-cylinder or two-cylinder engine, the range of pressure fluctuations in the PCV passage 30 may be large, but with the above configuration, the range of blow-by gas pressure fluctuations transmitted to the PCV valve 50 can be suppressed by shifting the phase of the pressure fluctuations in the first passage and the phase of the pressure fluctuations in the second passage.

[0042] Furthermore, in a configuration where the PCV valve 50 is positioned closer to the intake passage 10 than the longitudinal center of the PCV passage 30, the PCV valve 50 is further away from the engine 4, resulting in greater attenuation of blow-by gas pressure fluctuations. Therefore, the range of blow-by gas pressure fluctuations transmitted to the PCV valve 50 can be further suppressed.

[0043] (modified version) (1) In a modified example, as shown in Figure 4, the distance from the crankcase 42 of the engine 4 to the first chamber 52 and the distance from the crankcase 42 to the second chamber 54 may be different. This makes it possible to shift the phase of the blow-by gas pressure fluctuation in the first passage 70 and the phase of the blow-by gas pressure fluctuation in the second passage 72. In this case, the volume of the first chamber 52 and the volume of the second chamber 54 may be the same. With this configuration, the range of blow-by gas pressure fluctuations transmitted to the PCV valve 50 can be suppressed with a simple configuration.

[0044] (2) In other modifications, as shown in Figure 5, the PCV system 2 may be configured to have a first chamber 52 but no second chamber 54. Alternatively, the PCV system 2 may be configured to have a second chamber 54 but no first chamber 52. That is, it is sufficient that a chamber is provided in at least one of the first passage 70 and the second passage 72. With this configuration as well, pressure fluctuations of the blow-by gas in the upstream passage 32 can be canceled out, and the range of pressure fluctuations of the blow-by gas transmitted to the PCV valve 50 can be suppressed.

[0045] (3) In other modifications, the diameter of the first passage 70 and the diameter of the second passage 72 may be different. This configuration also allows the pressure fluctuations of the blow-by gas to cancel each other out in the upstream passage 32, thereby suppressing the range of pressure fluctuations of the blow-by gas transmitted to the PCV valve 50. In this case, the upstream passage 32 does not need to be equipped with chambers (first chamber 52 and second chamber 54).

[0046] (4) In other modifications, the lengths of the first passage 70 and the second passage 72 may be different. This configuration also allows for the cancellation of blow-by gas pressure fluctuations in the upstream passage 32, thereby suppressing the range of blow-by gas pressure fluctuations transmitted to the PCV valve 50. In this case, the upstream passage 32 does not need to be equipped with chambers (first chamber 52 and second chamber 54).

[0047] (5) In other modifications, the upstream passage 32 may include a third passage (not shown) in parallel with the first passage 70 and the second passage 72.

[0048] (6) In the above embodiment, the upstream end of the PCV passage 30 was connected to the crankcase 42 of the engine 4, but the configuration is not limited to this. In a modified example, the upstream end of the PCV passage 30 may be connected to the head cover 44 of the engine 4. In this configuration, blow-by gas in the space enclosed by the head cover 44 is sent to the intake passage 10 through the PCV passage 30.

[0049] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0050] 2: PCV system, 4: engine, 10: intake passage, 12: intake port, 14: intake valve, 16: throttle valve, 20: exhaust passage, 22: exhaust port, 24: exhaust valve, 30: PCV passage, 32: upstream passage, 34: downstream passage, 36: case side passage, 38: valve side passage, 40: cylinder block, 42: crankcase, 44: head cover, 46: piston, 47: connecting rod, 48: crankshaft, 50: PCV valve, 52: first chamber, 54: second chamber, 60: cylinder, 62: combustion chamber, 64: connecting passage, 70: first passage, 72: second passage, 90: fresh air passage, 92: on / off valve

Claims

1. A single-cylinder or two-cylinder engine, An intake passage connected to the engine, A PCV passage is connected to the engine and the intake passage, and supplies blow-by gas from the engine to the intake passage. The PCV passage includes a PCV valve, The PCV passage comprises an upstream passage between the engine and the PCV valve, and a downstream passage between the PCV valve and the intake passage. The upstream passage comprises a first passage and a second passage parallel to the first passage. A PCV system in which a chamber is provided in at least one of the first passage and the second passage.

2. A single-cylinder or two-cylinder engine, An intake passage connected to the engine, A PCV passage is connected to the engine and the intake passage, and supplies blow-by gas from the engine to the intake passage. The PCV passage includes a PCV valve, The PCV passage comprises an upstream passage between the engine and the PCV valve, and a downstream passage between the PCV valve and the intake passage. The upstream passage comprises a first passage and a second passage parallel to the first passage. A PCV system in which the diameter of the first passage and the diameter of the second passage are different.

3. A single-cylinder or two-cylinder engine, An intake passage connected to the engine, A PCV passage is connected to the engine and the intake passage, and supplies blow-by gas from the engine to the intake passage. The PCV passage includes a PCV valve, The PCV passage comprises an upstream passage between the engine and the PCV valve, and a downstream passage between the PCV valve and the intake passage. The upstream passage comprises a first passage and a second passage parallel to the first passage. A PCV system in which the length of the first passage and the length of the second passage are different.

4. A PCV system according to any one of claims 1 to 3, Chambers are provided in both the first passage and the second passage. A PCV system in which the volume of the chamber provided in the first passage and the volume of the chamber provided in the second passage are different.

5. A PCV system according to any one of claims 1 to 3, Chambers are provided in both the first passage and the second passage. A PCV system in which the distance from the engine to a chamber provided in the first passage is different from the distance from the engine to a chamber provided in the second passage.

6. A PCV system according to claim 5, A PCV system in which the volume of the chamber provided in the first passage and the volume of the chamber provided in the second passage are the same.

7. A PCV system according to any one of claims 1 to 3, A PCV system in which the PCV valve is located on the intake passage side of the longitudinal center of the PCV passage.

8. A PCV system according to any one of claims 1 to 3, A throttle valve is provided in the intake passage to adjust the cross-sectional area of ​​the intake passage. A PCV system in which the downstream end of the PCV passage is connected to the intake passage downstream of the throttle valve.

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