JPWO2013129556A1 - Blow-by gas reduction device - Google Patents

Abstract

A blow-by gas chamber (42) connected to the crank chamber (61) by a first communication passage and connected by a second communication passage (84) upstream of the throttle valve (57) in the intake passage is provided. A reed valve (67) is provided in the first communication path so that the blow-by gas flows only to the blow-by gas chamber (42) side. An oil return passage (oil hole) that communicates the lower end of the blow-by gas chamber (42) and the crank chamber (61) is provided. A gas-liquid separation chamber that connects the first communication path and the second communication path (84) is formed in the blow-by gas chamber (42). The oil return passage is formed so that the flow of the blow-by gas is restricted by losing the kinetic energy of the blow-by gas flowing in due to the pressure difference between the blow-by gas chamber (42) and the crank chamber (61). It is possible to provide a blow-by gas reduction device that can keep the manufacturing cost low and keep the pressure in the crank chamber lower than the atmospheric pressure.

Description

  The present invention relates to a blow-by gas reduction device that guides blow-by gas of an engine to an intake passage.

  As a conventional blow-by gas reduction device, for example, as described in Patent Document 1, there is an apparatus that sucks blow-by gas from the crankcase into the intake passage using negative pressure in the intake passage. The blow-by gas reduction device shown in Patent Document 1 employs a configuration in which blow-by gas is sucked from the valve operating cam chamber and guided to the intake passage on the downstream side of the throttle valve. The valve cam chamber and the intake passage are connected by a pipe member. A ventilation valve is provided at an intermediate portion of the pipe member.

  The ventilation valve opens when the pressure in the intake passage is lower than the pressure in the valve operating cam chamber and higher than a predetermined lower limit pressure, and closes when the pressure in the intake passage reaches the lower limit pressure. . That is, when the negative pressure in the intake passage becomes excessively large, the ventilation valve is closed so that blow-by gas is not sucked into the intake passage excessively.

JP-A-8-135429

  The blow-by gas reduction device described in Patent Document 1 has the following two problems. The first problem is that the manufacturing cost increases. This is because the ventilation valve is expensive.

  The second problem is that the pressure in the crank chamber may be higher than atmospheric pressure. This is because the fresh air flows into the valve cam chamber from the intake passage side through the pipe member as the piston rises, and the pressure in the crank chamber communicating with the valve cam chamber relatively increases. This is because the piston descends and the pressure in the crank chamber rises in this state.

  The present invention has been made to solve such a problem, and provides a blow-by gas reduction device capable of keeping the manufacturing cost low and keeping the pressure in the crank chamber lower than the atmospheric pressure. Objective.

  In order to achieve this object, the blow-by gas reduction device according to the present invention is connected to the crank chamber of the engine by a first communication passage and connected to the upstream side of the throttle valve of the intake passage by a second communication passage. When the pressure of the blow-by gas chamber is lower than the pressure of the crank chamber and the pressure of the blow-by gas chamber is in communication with the first communication passage, and the pressure of the blow-by gas chamber is higher than the pressure of the crank chamber A non-pressure actuated check valve that closes the one communication passage, and an oil return passage that communicates the lower end portion of the blow-by gas chamber and the crank chamber, and the blow-by gas chamber includes the first A gas-liquid separation chamber is formed to connect the second communication passage and the second communication passage, and the oil return passage is connected to the blow-in gas flow caused by the pressure difference between the blow-by gas chamber and the crank chamber. Flow of blow-by gas by loss of kinetic energy of Igasu is what is formed so as to be restricted.

  According to the present invention, during engine operation, the negative pressure upstream of the throttle valve in the intake passage is propagated to the blow-by gas chamber via the second communication passage. When the pressure in the intake passage is lower than the pressure in the crank chamber, the check valve opens and blow-by gas in the crank chamber is sucked into the blow-by gas chamber through the first communication passage. At this time, oil drifting in the form of a mist in the crank chamber is also sucked into the blow-by gas chamber together with the blow-by gas.

  The blow-by gas is sucked from the blow-by gas chamber to the upstream side of the throttle valve in the intake passage through the second communication passage. Since the pressure upstream of the throttle valve in the intake passage is higher than the pressure downstream of the throttle valve, an excessively large negative intake pressure does not act on the blow-by gas chamber. That is, blow-by gas does not pass through the gas-liquid separation chamber in the blow-by gas chamber too quickly. For this reason, the mist-like oil sucked into the blow-by gas chamber together with the blow-by gas adheres to the wall of the gas-liquid separation chamber when flowing in the gas-liquid separation chamber. The oil adhering to the wall is returned to the crank chamber through an oil return passage located at the lower end of the blow-by gas chamber.

  On the other hand, when the pressure in the crank chamber is equal to or lower than the pressure in the intake passage, the check valve does not open and the negative pressure in the crank chamber acts on the oil return passage. The oil return passage according to the present invention substantially functions as a throttle. For this reason, even if the pressure in the crank chamber is lower than the pressure in the blow-by gas chamber, the amount of blow-by gas flowing into the crank chamber through the oil return passage is extremely small.

For this reason, in this invention, the backflow of blow-by gas to the crank chamber can be suppressed as much as possible by using only one check valve which is less expensive than the conventional ventilation valve.
Therefore, according to the present invention, it is possible to provide a blow-by gas reduction device that can keep the manufacturing cost low and keep the pressure in the crank chamber lower than the atmospheric pressure.

FIG. 1 is a side view of an engine provided with a blow-by gas reduction device according to a first embodiment of the present invention. This figure is drawn with the cylinder body and the oil pan broken. FIG. 2 is an enlarged cross-sectional view of the blow-by gas chamber portion according to the first embodiment. FIG. 3 is a side view of the cylinder body according to the first embodiment, in which a part of the lid of the blow-by gas reduction device is cut away. In the figure, the fracture position in FIG. 2 is indicated by the line II-II. 4 is a cross-sectional view of the cylinder body portion taken along line IV-IV in FIG. FIG. 5A is a front view showing a state in which each component is attached to the plate-like member according to the first embodiment. FIG. 5B is a diagram showing a state in which each component is attached to the plate-like member according to the first embodiment, and FIG. 5B is a sectional view taken along line BB in FIG. 5A. FIG. 5C is a view showing a state in which each component is attached to the plate-like member according to the first embodiment, and FIG. 5C is a cross-sectional view taken along line CC in FIG. 5A. FIG. 6A is a front view of the lid viewed from the plate-like member side. 6B is a cross-sectional view taken along line BB in FIG. 6A. FIG. 7 is a side view of an engine provided with a blow-by gas reduction device according to a second embodiment of the present invention. This figure is drawn with the cylinder body and the oil pan broken. FIG. 8 is a side view of an engine provided with a blow-by gas reduction device according to a third embodiment of the present invention. This figure is drawn with the cylinder body and the oil pan broken. FIG. 9 is a side view of an engine equipped with a blow-by gas reduction device according to a fourth embodiment of the present invention. This figure is drawn with the cylinder body and the oil pan broken. FIG. 10A is a graph showing the relationship between engine speed and crankcase pressure during no-load operation. FIG. 10B is a graph showing a relationship between engine rotation speed and crank chamber pressure during medium load operation. FIG. 10C is a graph showing the relationship between engine speed and crankcase pressure during high load operation.

(First embodiment)
Hereinafter, a first embodiment of a blow-by gas reducing apparatus according to the present invention will be described in detail with reference to FIGS.
An engine 1 shown in FIG. 1 is a two-cylinder DOHC type mounted on a vehicle (not shown). The phase difference between the two pistons 2 of the engine 1 is 360 degrees. In FIG. 1, 3 is a cylinder body, 4 is an oil pan, 5 is a cylinder head, and 6 is a head cover.

  A crankshaft 11 and two balancer shafts 12 and 13 are rotatably provided at the lower portion of the cylinder body 3. The two balancer shafts 12 and 13 are provided at positions where the axis is parallel to the axis of the crankshaft 11 and the crankshaft 11 is sandwiched between them. These balancer shafts 12 and 13 are connected to the crankshaft 11 by gears (not shown) so as to rotate at the same rotational speed as the crankshaft 11 and to rotate in the opposite direction to the crankshaft 11.

  On both sides of the lower portion of the cylinder body 3 adjacent to the two balancer shafts 12 and 13, through-holes 14 and 15 for assembling the balancer shaft are formed. The outer end openings of these through holes 14 and 15 are closed by lids 16 and 17, respectively. The balance weights 12a and 13a of the balancer shafts 12 and 13 rotate through the through holes 14 and 15 as indicated by a two-dot chain line. Therefore, although the two balancer shafts 12 and 13 are accommodated in the lower portion of the cylinder body 3, the cylinder body 3 can be reduced in size and weight, and the balancer shafts 12 and 13 can be combined. Adhesiveness is improved.

An oil passage 21 extending in the vertical direction is formed in one of the two lid bodies 16 and 17 located on the right side in FIG. The oil passage 21 is formed at a position different from the balance weight 13a of the balancer shaft 13 located on the right side in FIG. The oil passage 21 is located on the far side of the paper surface of FIG. 1 with respect to the rotation trajectory of the balance weight 13a.
The upper end of the oil passage 21 is connected to a main oil return passage 23 that extends in the vertical direction on the upper portion of one side wall 22 of the cylinder body 3. The main oil return passage 23 collects oil that has lubricated the lubricated portions of the cylinder head 5. The engine 1 according to this embodiment is mounted on a vehicle in an inclined state so that the side wall 22 of the cylinder body 3 having the main oil return passage 23 is positioned below. In FIG. 1, the horizontal line is indicated by a two-dot chain line L. Hereinafter, the lower side wall is referred to as the lower side wall 22, and the other side wall of the cylinder body 3 positioned on the opposite side of the cylinder axis C is referred to as the upper side wall 24.

  A lower end of the oil passage 21 of the lid body 17 is connected to a lower oil passage 25 in the cylinder body 3. The oil flowing down the oil passage 21 is returned from the lower oil passage 25 through the oil return pipe 26 to the lower portion in the oil pan 4. The oil pan 4 is formed to extend downward from the lower end of the cylinder body 3, and is fixed to the lower end of the cylinder body 3. A baffle plate 31 is attached in the upper part of the oil pan 4 in order to prevent oil from undulating.

  The baffle plate 31 is formed with a recess 33 for accommodating the oil strainer 32. The recess 33 is formed in a shape in which a part of the baffle plate 31 is recessed downward. A hole 34 into which the lower end of the oil strainer 32 can be inserted is formed at the bottom of the recess 33. Between the bottom of the recess 33 and the oil strainer 32, an annular gap 35 is formed in a plan view that allows oil to pass therethrough. The oil strainer 32 is supported at the lower end of the cylinder body 3 and is connected to an oil suction passage (not shown). The oil suction passage is connected to an oil inlet of an oil pump (not shown).

An extension pipe 36 extending downward is attached to the lower end of the oil strainer 32. As shown in FIG. 1, the lower end of the extension pipe 36 is located below the oil surface 37 of the oil stored in the oil pan 4. That is, the lower end of the extension pipe 36 opens into the oil. For this reason, the oil stored in the oil pan 4 is sucked into the extension pipe 36 from the lower end portion in the oil pan 4 by the operation of the oil pump.
By forming the recess 33 in the baffle plate 31, the oil strainer 32 is positioned substantially above the baffle plate 31. For this reason, by attaching the oil pan 4 to the cylinder body 3, the oil strainer 32 can be correctly arranged so that the extension pipe 36 is positioned at the lower end portion in the oil pan 4.

A blow-by gas chamber 42 of a blow-by gas reduction device 41 according to the present invention is provided above the other lid 16 (the left side in FIG. 1) of the two lids 16 and 17. The blow-by gas chamber 42 is provided on the upper side wall 24 of the cylinder body 3 as will be described in detail later.
Two cylinders 43 into which the piston 2 is fitted are provided on the upper portion of the cylinder body 3.

  The cylinder head 5 has two intake valves 44 and two exhaust valves 45 per cylinder, a valve operating device 48 having cam shafts 46 and 47 for driving the intake valves 44 and the exhaust valves 45, and a cylinder head for each cylinder. A spark plug 49 and a fuel injection valve 50 are provided. The intake port 5 a that is opened and closed by the intake valve 44 opens in a side portion of the cylinder head 5 that is continuous with the upper side wall 24 of the cylinder body 3. The fuel injection valve 50 injects fuel into the intake port 5a. The exhaust port 5 b that is opened and closed by the exhaust valve 45 opens at the side of the cylinder head 5 that is continuous with the lower side wall 22 of the cylinder body 3.

An intake manifold 52 of an intake device 51 is connected to the opening portion of the intake port 5a. For this reason, the blow-by gas chamber 42 is positioned below the intake manifold 52. An exhaust manifold 54 of an exhaust device 53 is connected to the opening portion of the exhaust port 5b.
The intake manifold 52 is provided for each cylinder, extends from the side portion of the cylinder head 5 to above the head cover 6, and is connected to a surge tank 55. The surge tank 55 is formed in a tubular shape, and is supported by the cylinder head 5 so as to extend in the axial direction of the crankshaft 11 above the exhaust manifold 54. A throttle valve 57 is attached to one end of the surge tank 55 in the longitudinal direction via an intake pipe 56.

  As shown in FIG. 1, the intake pipe 56 is formed to extend from the intake system side to the exhaust system side above the head cover 6 when viewed from the axial direction of the crankshaft 11. The throttle valve 57 has a valve body made up of a butterfly valve (not shown), and is provided at an end of the intake pipe 56 on the intake system side. Although not shown, the air that has passed through the air cleaner is guided to the intake pipe 56.

The blow-by gas reduction device 41 separates blow-by gas and oil in the blow-by gas chamber 42 provided in the upper side wall 24, and only blow-by gas is taken into the intake passage (the intake pipe upstream of the throttle valve 57). 56).
As shown in FIG. 2, a through hole 62 that communicates the inside and outside of the crank chamber 61 is formed in the upper portion of the upper side wall 24. A plate-like member 63 is overlaid on the outer surface 24 a of the upper side wall 24. A seal member 64 is provided between the plate member 63 and the outer surface 24a.

The plate-like member 63 is formed of a metal plate that is larger than the opening of the through hole 62, and is fixed to the upper side wall 24 by a fixing bolt 66 (see FIG. 3) together with a lid 65 described later. In this embodiment, the blow-by gas chamber 42 is formed by the plate-like member 63 and the lid body 65.
As shown in FIGS. 2 and 4, a reed valve 67 and a flow path forming plate 68 are attached to a portion of the plate-like member 63 located outside the cylinder body 3.

  As shown in FIGS. 4 and 5, the reed valve 67 includes a valve body 67 a that opens and closes a hole 63 a formed in the plate-like member 63, and a stopper 67 b that restricts the valve body 67 a from opening excessively. ing. One end of the stopper 67b is overlapped with the plate-like member 63, and is fixed to the plate-like member 63 with a mounting bolt 67c penetrating the one end. The mounting bolt 67c is screwed into a nut member 67d located on the opposite side (crank chamber 61 side) of the plate-like member 63.

The reed valve 67 is attached at a position corresponding to the through hole 62 in the plate member 63. In this embodiment, the reed valve 67 constitutes a “negative pressure actuated check valve” according to the present invention. The blow-by gas chamber 42 is connected to the crank chamber 61 by a first communication passage 69 including the through hole 62 and the reed valve 67.
The reed valve 67 brings the first communication passage 69 into a communication state when the pressure in the blow-by gas chamber 42 is lower than the pressure in the crank chamber 61. The reed valve 67 closes the first communication passage 69 when the pressure in the blow-by gas chamber 42 is higher than the pressure in the crank chamber 61.

The flow path forming plate 68 is fixed in a standing state on the plate member 63.
As shown in FIGS. 2 and 4, a cover 71 is attached to a portion of the plate-like member 63 that faces the inside of the cylinder body 3. This cover 71 is for preventing the oil in the cylinder body 3 from jumping into the hole 63a of the plate-like member 63, and covers the hole 63a from the horizontal direction and the upper side in cooperation with the plate-like member 63. ing. A space 71a between the plate-like member 63 and the cover 71 is open only downward when the reed valve 67 is closed.

An oil hole 72 is formed in the lower end portion of the plate-like member 63 located below the reed valve 67 as shown in FIGS. 2, 3 and 5A. The oil hole 72 is formed so as to penetrate the plate-like member 63.
The position where the oil hole 72 is formed is not limited to a position below the reed valve 67, and can be appropriately changed as long as it is a lower end portion in the blow-by gas chamber 42.

  That is, the oil hole 72 may be provided only on the side opposite to the reed valve 67 {the lower end portion of a third air chamber 93 (see FIG. 3) described later} across the convex portion indicated by reference numeral 66a in FIG. It can be provided in both air chambers. The convex portion 66 a is a portion through which the fixing bolt 66 passes through the lid body 65, and is formed so as to protrude into the blow-by gas chamber 42. In the case where the oil hole 72 is provided only in one air chamber, the oil in the lower part of the air chamber where the oil hole 72 does not exist overflows into the air chamber on the opposite side through a notch 74a described later. In order to guide the oil from the air chamber where the oil hole 72 does not exist to the air chamber where the oil hole 72 exists, the communication hole 72a is formed in the convex portion 66a located at the lower end of the blow-by gas chamber 42 as shown by a two-dot chain line. It may be formed.

  The hole diameter (passage cross-sectional area) of the oil hole 72 is formed to an optimal dimension that prevents passage of blow-by gas without hindering the outflow of oil. The optimum hole diameter of the oil hole 72 is a hole diameter in which the flow of the blowby gas is regulated by losing the kinetic energy of the blowby gas flowing into the oil hole 72 due to the pressure difference between the blowby gas chamber 42 and the crank chamber 61. .

Further, as shown in FIG. 3, the vertical position of the oil hole 72 is a position close to the lower end of the opening edge of the through hole 62 and is positioned slightly above the lower end. In this embodiment, the oil hole 72 constitutes the “oil return passage” according to claim 1, and the “through hole” as defined in the invention according to claim 2.
As shown in FIG. 1, the engine 1 according to this embodiment is inclined as described above in the in-vehicle state. For this reason, as shown in FIG. 1, the plate-like member 63 and the lid 65 according to this embodiment are directed obliquely upward in the in-vehicle state. Since the plate-like member 63 and the lid body 65 are inclined in this way, the oil hole 72 is directed obliquely downward at the lowest position of the blow-by gas chamber 42, so that the oil is in the blow-by gas chamber 42. It will not stay in.

  The lid body 65 forms the blow-by gas chamber 42 in cooperation with the plate-like member 63. As shown in FIGS. 2 and 4, the lid 65 has a rectangular tube-shaped frame 65 a and a bottom plate 65 b that closes one opening of the frame 65 a. It is formed in a box shape that opens to the front. The lid 65 is attached to the upper side wall 24 so as to overlap the plate-like member 63. As shown in FIG. 2, a seal member 73 is provided between the frame body 65 a of the lid body 65 and the plate-like member 63.

  As shown in FIG. 3, FIG. 6A and FIG. 6B, a plurality of partition plates 74 to 76 are integrally formed in the lid body 65 by integral molding in order to form an inversion flow path A in the blow-by gas chamber 42. Is formed. FIG. 6A depicts the lid 65 as viewed from the plate-like member 63 side. The plurality of partition plates includes a vertical partition plate 74, a lower partition plate 75, and an upper partition plate 76. The vertical partition plate 74 divides the blow-by gas chamber 42 in the lid 65 into a check valve portion 77 and a gas-liquid separation portion 78. The lower partition plate 75 extends obliquely downward from the lower portion of the vertical partition plate 74 into the gas-liquid separator 78. The upper partition plate 76 extends obliquely downward into the gas-liquid separation part 78 from the frame body 65a. These partition plates 74 to 76 are formed so as to protrude from the bottom plate 65 b toward the plate member 63. The partition plates 74 to 76 are in contact with the plate member 63 in a state where the frame body 65a is attached to the plate member 63, or are opposed to each other through a minute gap in which air hardly flows. Is formed.

  As shown in FIG. 3, the vertical partition plate 74 is formed at a position where the reed valve 67 can be accommodated in the check valve portion 77. A notch 74 a for communicating the check valve 77 and the gas-liquid separator 78 is formed in the lower part of the vertical partition plate 74. As shown in FIGS. 3 and 4, the flow path forming plate 68 attached to the plate member 63 is positioned so as to be adjacent to the notch 74a. In other words, the plate 68 is provided at a position where the plate 68 can be seen through the notch 74a from the check valve portion 77 side.

The lower partition plate 75 located in the gas-liquid separation unit 78 extends obliquely downward from the vertical partition plate 74 in the gas-liquid separation unit 78 toward the frame body 65a. A first space 79 is formed between the tip of the lower partition plate 75 and the frame body 65a.
The upper partition plate 76 extends obliquely downward from the frame body 65 a toward the vertical partition plate 74 in the gas-liquid separator 78. A second space 80 is formed between the tip of the upper partition plate 76 and the vertical partition plate 74.

  As shown in FIG. 3, a lower end portion of a blow-by gas pipe 82 is attached to a portion of the frame body 65 a located above the upper partition plate 76 via a pipe joint 81. The gas-liquid separator 78 and the pipe 82 communicate with each other through a pipe joint 81. As shown in FIG. 1, the upper end portion of the pipe 82 is connected to the upstream side of the throttle valve 57 in the intake pipe 56 via a pipe joint 83. That is, the blow-by gas chamber 42 is connected to the intake passage by the second communication passage 84 including the pipe 82 and the pipe joints 81 and 83.

  That is, the intake negative pressure upstream of the throttle valve 57 is transmitted to the blow-by gas chamber 42 via the second communication passage 84, so that the blow-by gas in the blow-by gas chamber 42 passes through the second communication passage 84. It is sucked into the intake passage.

As shown in FIG. 3, the reversing flow path A includes a plurality of air chambers 91 to 94 provided in the blow-by gas chamber 42 and relatively narrow first to first air passages that communicate with each other. 3 communication holes 95 to 97. In this embodiment, the reversible flow path A constitutes the “gas-liquid separation chamber” in the present invention. The “gas-liquid separation chamber” referred to in the present invention is not limited to the reversible flow path shown in this embodiment, and various types can be considered. For example, it is possible to adopt a configuration in which a plurality of expansion chambers communicate with each other through a relatively narrow communication path. In this case, the blow-by gas flows repeatedly by expanding and contracting, and the blow-by gas and oil are separated in this process.
The plurality of air chambers include a first air chamber 91 connected to the first communication passage 69, a second air chamber 92 connected to the second communication passage 84, and a space between these air chambers. The third and fourth air chambers 93 and 94 are provided. The third air chamber 93 is formed below the lower partition plate 75. The fourth air chamber 94 is formed between the lower partition plate 75 and the upper partition plate 76.

  The first air chamber 91 and the third air chamber 93 are connected to each other by a first communication hole 95 formed by a notch 74 a of the vertical partition plate 74. The blow-by gas that has flowed into the third air chamber 93 from the first communication hole 95 hits the plate 68. For this reason, the flow direction of the blow-by gas that has flowed into the third air chamber 93 can be changed in the third air chamber 93. The lowermost portion of the first air chamber 91 and the lowermost portion of the third air chamber 93 are communicated with the crank chamber 61 through the oil hole 72.

The third air chamber 93 and the fourth air chamber 94 are connected to each other by a second communication hole 96 formed by the first space 79.
The fourth air chamber 94 and the second air chamber 92 are connected to each other by a third communication hole 97 formed by the second space 80.
The first to third communication holes 95 to 97 are connected to the air chamber 91 so that the first communication passage 69 and the second communication passage 84 are connected via the plurality of air chambers 91 to 94. ~ 94 communicate with each other. That is, the gas-liquid separator 78 in the blow-by gas chamber 42 is formed so that the blow-by gas flows from the bottom to the top.

  The cross-sectional area (passage cross-sectional area) of the opening portions of the first to third communication holes 95 to 97 is smaller than the cross-sectional area (passage cross-sectional area) of the second to fourth air chambers 92 to 94. Here, the cross-sectional area is an area of a cross section orthogonal to the direction in which the blow-by gas flows. For this reason, the flow velocity of the blow-by gas flowing through the second to fourth air chambers 92 to 94 is lower than the flow velocity of the blow-by gas flowing through the first to third communication holes 95 to 97.

  In the blowby gas reduction device 41 configured in this way, the intake passage becomes negative pressure during engine operation, whereby the intake negative pressure is propagated from the intake passage to the blowby gas chamber 42 via the second communication passage 84. The The intake negative pressure is propagated from the second air chamber 92 of the blow-by gas chamber 42 to the first air chamber 91 through the fourth air chamber 94 and the third air chamber 93. Then, the reed valve 67 is opened and the blow-by gas in the crank chamber 61 is sucked into the blow-by gas chamber 42 through the first communication passage 69. At this time, oil (not shown) drifting in the form of a mist in the crank chamber 61 is also sucked into the blow-by gas chamber 42 together with the blow-by gas.

  The blow-by gas is sucked from the blow-by gas chamber 42 through the second communication passage 84 to the upstream side of the throttle valve 57 in the intake passage. Since the pressure upstream of the throttle valve 57 in the intake passage is higher than the pressure downstream of the throttle valve, an excessively large negative intake pressure does not act on the blow-by gas chamber. That is, the blow-by gas does not pass through the reversing flow path A in the blow-by gas chamber 42 too quickly, but flows along the wall of the reversing flow path A.

  For this reason, the mist-like oil sucked into the blow-by gas chamber 42 together with the blow-by gas adheres to the walls of the blow-by gas chamber 42 and the partition plates 74 to 76 when flowing through the reversible flow path A. The oil adhering to the walls and the partition plates 74 to 76 flows downward by gravity and returns to the crank chamber 61 through the oil hole 72 located at the lower end portion of the flow path A. As a result, only the blowby gas is sucked from the blowby gas chamber 42 into the intake passage.

  On the other hand, when the pressure in the crank chamber 61 is equal to or lower than the pressure in the intake passage, the reed valve 67 does not open and the negative pressure in the crank chamber 61 acts on the oil hole 72. Since the oil hole 72 according to this embodiment substantially functions as a throttle, even if the pressure in the crank chamber 61 is lower than the pressure in the blow-by gas chamber 42, the oil hole 72 flows back to the crank chamber 61 through the oil hole 72. The amount of blow-by gas that is produced is very small.

For this reason, in this embodiment, the backflow of blow-by gas to the crank chamber 61 can be suppressed as much as possible by using only one reed valve 67 which is less expensive than the conventional ventilation valve.
Therefore, according to this embodiment, it is possible to provide a blow-by gas reduction device that can keep the manufacturing cost low and keep the pressure in the crank chamber lower than the atmospheric pressure.

  The reversible flow path A according to this embodiment is formed by a plurality of air chambers 91 to 94 and relatively narrow first to third communication holes 95 to 97 that communicate with each other. ing. The plurality of air chambers include a first air chamber 91 connected to the first communication passage 69 and a second air chamber 92 connected to the second communication passage 84. The communication holes 95 to 97 allow the air chambers to communicate with each other so that the first communication passage 69 and the second communication passage 84 are connected via the plurality of air chambers.

For this reason, the flow velocity of the blow-by gas flowing through the reversing channel A increases when the blow-by gas passes through the communication holes 95 to 97, and the blow-by gas exits from the communication holes 95 to 97 and enters each air chamber. Decreases rapidly by entering. On the other hand, the flow rate of oil increases when passing through the communication holes 95 to 97, and then gradually decreases after the oil enters the air chamber. The reason why the flow rate of oil gradually decreases is because the inertial mass of oil is larger than the inertial mass of blow-by gas. That is, since the oil will fly in a direction different from the blow-by gas in the air chamber, the oil easily hits the wall of the reversible flow path A.
Therefore, according to this embodiment, it is possible to provide a blow-by gas reduction device that can capture oil more reliably.

  The first communication passage 69 according to this embodiment includes a through hole 62 that penetrates the side wall of the cylinder body 3 and the check valve that includes a reed valve 67. The blow-by gas chamber 42 is formed by a plate-like member 63 overlaid on the outer surface 24 a of the upper side wall 24, and a lid body 65 overlaid on the plate-like member 63. The reed valve 67 is provided at a portion corresponding to the through hole 62 in the plate member 63. The inversion flow path A is formed by a plurality of partition plates 74 to 76 that are provided on the lid body 65 so as to protrude toward the plate-like member 63. The second communication path 84 includes a pipe 82 and pipe joints 81 and 83 extending from the lid 65 to the intake pipe 56 on the upstream side of the throttle valve.

  For this reason, according to this embodiment, since the blow-by gas chamber 42 is provided at the side of the cylinder body 3, interference between the blow-by gas chamber 42 and the intake device 51 can be avoided, and the engine 1 can be downsized. Can be planned. That is, when the blow-by gas chamber 42 is provided in the vicinity of the head cover 6, members such as the intake pipe 56, the surge tank 55, and the intake manifold 52 that are located above the head cover 6 are placed above or to the side of the blow-by gas chamber 42. It must be formed to bypass. When the intake device 51 is formed in this way, the height of the engine increases or the width of the engine increases, and the engine becomes larger as described above.

The blow-by gas chamber 42 according to this embodiment is partitioned by a check valve portion 77 where the check valve is located, and the check valve portion 77 by a part of the partition plate (vertical partition plate 74). And a gas-liquid separator 78. The gas-liquid separator 78 is formed such that blow-by gas flows from the bottom to the top.
For this reason, oil can be separated from blow-by gas by gravity. Therefore, according to this embodiment, it is possible to provide a blow-by gas reduction device with a large amount of oil trapped.

  The oil return passage according to this embodiment is formed by an oil hole 72 (through hole) that penetrates a plate-like member 63 that is a wall that partitions the blow-by gas chamber 42 and the crank chamber 61. For this reason, since the oil hole 72 can be formed with high accuracy by machining so that the hole diameter becomes as designed, the blow-by gas is reliably prevented from flowing back into the crank chamber 61 through the oil hole 72. Can do. Further, according to this embodiment, since a member that functions exclusively as an oil return passage is unnecessary, a blow-by gas reduction device that is easy to manufacture and inexpensive can be provided.

(Second Embodiment)
The oil return passage can be formed as shown in FIG. In FIG. 7, the same or equivalent members as described with reference to FIGS. 1 to 6 are given the same reference numerals, and detailed description thereof is omitted.

  A blow-by gas reduction device 41 shown in FIG. 7 includes a first oil return pipe 101 located outside the cylinder body 3 and a second oil return pipe 102 located in the crank chamber 61. These pipes 101 and 102 are for returning the oil in the blow-by gas chamber 42 into the crank chamber 61. The oil hole 72 shown in the first embodiment is not formed in the plate-like member 63 according to this embodiment.

  One end of the first oil return pipe 101 is connected to a lid body 65 that forms the blow-by gas chamber 42 by a pipe joint 103. The pipe joint 103 communicates the inside of the first oil return pipe 101 and the lower end portion in the blow-by gas chamber 42 in the same manner as the pipe joint 81 described above. The position where the pipe joint 103 is attached can be changed as appropriate as long as it is the lower end of the blow-by gas chamber 42. That is, one end of the first oil return pipe 101 can be connected to the check valve portion 77 or the gas-liquid separation chamber 78 of the blow-by gas chamber 42.

  The other end portion of the first oil return pipe 101 is connected to the lid body 16 located below the lid body 65 by a pipe joint 104. The pipe joint 104 has a pipe body (not shown) that penetrates the lid body 16. One end of the second oil return pipe 102 is connected to the tube. That is, the other end (lower end) of the first oil return pipe 101 is connected to one end (upper end) of the second oil return pipe 102 via the pipe joint 104. The other end of the second oil return pipe 102 extends downward along the side wall 24 of the cylinder body 3 and is inserted into the oil pan 4. The lower end of the second oil return pipe 102 is located above the oil level 105 of the oil during engine operation.

  In this embodiment, the first and second oil return pipes 101 and 102 and the pipe joints 103 and 104 constitute an oil return passage 106. In other words, the oil separated from the blow-by gas in the blow-by gas chamber 42 is returned from the lower end portion in the blow-by gas chamber 42 to the crank chamber 61 through the oil return passage 106.

  The passage cross-sectional area and length of the oil return passage 106 are such that the kinetic energy of the blow-by gas flowing into the oil return passage 106 is lost due to the pressure difference between the blow-by gas chamber 42 and the crank chamber 61, and the flow of the blow-by gas is reduced. It is formed to a regulated size. For this reason, since the oil return passage 106 substantially functions as a throttle, even if the pressure in the crank chamber 61 is lower than the pressure in the blow-by gas chamber 42, the oil return passage 106 passes through the oil return passage 106 and enters the crank chamber 61. The amount of blow-by gas that flows in is very small.

  When the oil return passage 106 is formed by pipe members (first and second oil return pipes 101 and 102 and the pipe joints 103 and 104) as shown in this embodiment, the length of the pipe member The aperture effect can be adjusted by changing. Therefore, according to this embodiment, it is possible to easily realize an oil return passage that has both a function of discharging oil from the blow-by gas chamber 42 and a function of regulating the flow of blow-by gas.

(Third embodiment)
The oil return passage can be formed as shown in FIG. In FIG. 8, the same or equivalent members as described with reference to FIGS. 1 to 7 are given the same reference numerals, and detailed description thereof is omitted.
The lower end portion of the second oil return pipe 102 shown in FIG. 8 is inserted into the oil stored in the oil pan 4 during engine operation. That is, the lower end of the second oil return pipe 102 is positioned in the oil stored at the bottom of the crank chamber.

  Therefore, according to this embodiment, since the lower end of the pipe member (second oil return pipe 102) constituting the oil return passage 106 is closed with oil, the blow-by gas chamber 42 is blown into the crank chamber 61. It is possible to more reliably prevent the gas from flowing backward.

(Fourth embodiment)
The oil return passage can be formed as shown in FIG. 9, the same or equivalent members as those described with reference to FIGS. 1 to 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  A box member 107 is provided at an intermediate portion of the first oil return pipe 101 shown in FIG. A space 108 communicating with the first oil return pipe 101 is formed in the box member 107. This space 108 is for canceling the pulsation of the gas in the crank chamber 61 that is propagated from the crank chamber 61 to the blow-by gas chamber 42 through the second oil return pipe 102 and the first oil return pipe 101. It is. That is, the negative pressure pulsation propagated in the oil return passage 106 toward the blow-by gas chamber 42 is canceled by the box member 107.

  For this reason, in the blow-by gas reduction device 41 shown in this embodiment, the negative pressure in the crank chamber 61 transmitted from the first oil return pipe 101 to the blow-by gas chamber 42 becomes substantially constant. Therefore, according to this embodiment, it is possible to provide a blow-by gas reduction device in which blow-by gas is more difficult to flow out of the blow-by gas chamber.

  The blow-by gas chamber 42 according to each embodiment described above is provided in the cylinder body 3. However, in the present invention, the blow-by gas chamber 42 can be provided in the head cover 6. In the case of adopting this configuration, the oil return passage can be formed by an oil return pipe that passes from the head cover 6 into the engine or outside the engine 1.

  When the blow-by gas reduction device according to the present invention was prototyped and the pressure in the crank chamber 61 was measured, results as shown in FIGS. 10A to 10C were obtained. 10A to 10C are graphs showing the relationship between the engine rotation speed and the crank chamber pressure. In measuring the pressure of the crank chamber 61, the form of the oil return passage was changed as the specifications A to E.

The oil return passage of the specification A is an oil return hole having a hole diameter of 4 mm and is formed at three locations of the blow-by gas chamber 42.
The oil return passage of the specification B is an oil return hole having a hole diameter of 4 mm, and is formed at one place of the blow-by gas chamber 42.
The oil return passage of the specification C is an oil return hole having a hole diameter of 3 mm, and is formed at one place of the blow-by gas chamber 42.
The oil return passage of the specification D is an oil return hole having a hole diameter of 2 mm, and is formed at one place of the blow-by gas chamber 42. The oil hole 72 shown in the first embodiment described above corresponds to the oil return hole of the specification D.
Unlike the oil hole 72, the oil return path of the specification E is an oil return pipe having a hole diameter of 4 mm, and a dedicated oil return path is connected thereto. The downstream end of the oil return passage is positioned in the oil stored at the bottom of the crank chamber even during engine operation. The oil return passage 106 shown in the third embodiment described above corresponds to the oil return hole of the specification E.

  FIG. 10A shows a case where the engine is operated in a no-load state such as idling operation. In this case, when the oil return passage of the specification A is used, the inside of the crank chamber 61 is in a positive pressure state over the entire engine speed. Further, in this case, by using the oil return passages of the specification D and the specification E, the inside of the crank chamber 61 is kept in a negative pressure state over the entire engine speed. As for the state in the crank chamber 61, a state in which the positive pressure is instantaneously and a state in which the negative pressure is instantaneously negative are repeated even during the four strokes of the engine. The instantaneous positive pressure state is eliminated by opening the reed valve 67 and discharging the blow-by gas in the crank chamber 61 to the blow-by gas chamber 42. The fact that the pressure in the crank chamber 61 is kept at a negative pressure means that the reed valve 67 is operating correctly without the outside air being sucked into the crank chamber 61 from the oil return hole.

  FIG. 10B shows a case where the engine is operated so as to obtain an intermediate throttle load. Also in this case, when the oil return passage of the specification A is used, the inside of the crank chamber 61 becomes a positive pressure over the entire engine speed. In this case, if the oil return passages of specifications B and C are used, the crank chamber 61 is in a positive pressure state or a pressure higher than the necessary minimum negative pressure at some engine speeds. End up. When the oil return passages of specification D and specification E are used, the inside of the crank chamber 61 is maintained in a negative pressure state over the entire engine speed.

  FIG. 10C shows a case where the engine is operated so that the throttle is fully opened (high load). In this case, when the oil return passage of the specification A is used, the inside of the crank chamber 61 becomes a positive pressure at a part of the engine rotation speed. Further, by using the oil return passages of the specifications C to E, the inside of the crank chamber 61 is kept at a negative pressure over the entire engine speed.

  From the above results, in the engine blow-by gas reduction device used in the experiment, the inside of the crank chamber 61 is spread over the entire engine speed by using the oil return passages of the specifications D and E regardless of the engine load conditions. Negative pressure is maintained. The oil return passage of the specification D has a simple structure and can reduce the manufacturing cost.

  Accordingly, as shown in FIGS. 10A to 10C, by optimizing the oil return passage so that the passage of blow-by gas is suppressed without impeding the oil outflow, the inside of the crank chamber 61 is always kept at a negative pressure. Proven to be preserved. Further, it has been proved that the inside of the crank chamber 61 is always kept at a negative pressure by connecting a dedicated oil return passage (oil return pipe) even if the diameter of the oil return hole is large. By using the oil return pipe, even if the downstream end of the oil return passage is open above the oil level in the crank chamber 61 as shown in FIGS. Since it is hindered, the same effect as described above can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Cylinder body, 24 ... Upper side wall, 41 ... Blow-by gas reduction apparatus, 42 ... Blow-by gas chamber, 56 ... Intake pipe, 57 ... Throttle valve, 61 ... Crank chamber, 62 ... Through-hole, 63 ... Plate , 65 ... lid, 67 ... reed valve (check valve), 69 ... first communication passage, 72 ... oil hole, 74 ... vertical partition plate, 75 ... lower partition plate, 76 ... upper partition plate, 77 ... Check valve part, 78 ... Gas-liquid separation part, 82 ... Pipe, 84 ... Second communication path, 91 ... First air chamber, 92 ... Second air chamber, 93 ... Third air chamber, 94: fourth air chamber, 95-97: first to third communication holes, 101: first oil return pipe, 102: second oil return pipe, 103, 104: pipe joint, 105: oil level 106: Oil return passage, 107: Box member, A: Inverted flow path.

Claims (5)

A blow-by gas chamber connected to the crank chamber of the engine by a first communication path and connected by a second communication path upstream of the throttle valve of the intake path;
When the pressure in the blow-by gas chamber is lower than the pressure in the crank chamber, the first communication passage is in a communication state, and when the pressure in the blow-by gas chamber is higher than the pressure in the crank chamber, the first communication passage is closed. A negative pressure actuated check valve, and
An oil return passage communicating the lower end of the blow-by gas chamber and the crank chamber;
A gas-liquid separation chamber that connects the first communication path and the second communication path is formed in the blow-by gas chamber,
The oil return passage is formed so as to restrict the flow of blow-by gas by losing the kinetic energy of the blow-by gas flowing in due to the pressure difference between the blow-by gas chamber and the crank chamber. apparatus.   2. The blow-by gas reduction device according to claim 1, wherein the oil return passage is formed by a through-hole penetrating a wall that partitions the blow-by gas chamber and the crank chamber.   2. The blowby gas reduction apparatus according to claim 1, wherein the oil return passage is formed by a pipe member that communicates the blowby gas chamber and the crank chamber.   4. The blow-by gas reduction device according to claim 3, wherein the lower end of the pipe member is positioned in the oil stored in the bottom of the crank chamber.   4. The blow-by gas reduction apparatus according to claim 3, wherein a space for canceling pulsation in the crank chamber is formed at an intermediate portion of the pipe member.

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