JP2013036370A - Blow-by gas circulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and weight of an engine.SOLUTION: In a crankshaft 10, there are formed: separation passages 26a, 26b which are opened at outer circumferential surfaces of crank webs 15a, 15b and extend in the radial direction; axial passages 27a, 27b extending in the axial direction; and radial passages 28a, 28b formed at journals 14a, 14b extending in the radial direction to make outer circumferential surfaces of the journals 14a, 14b communicate with the axial passages 27a, 27b. Communication grooves 32a, 32b communicating with the radial passages 28a, 28b are formed at inner circumferential surfaces of slide bearings 31a, 31b for supporting the journals 14a, 14b of the crankshaft 10. Exhaust passages 33a, 33b for supplying blow-by gas to the intake system are formed in a crank case 11.

Description

  The present invention relates to a blow-by gas recirculation device that reduces blow-by gas leaking from a combustion chamber into a crankcase into the combustion chamber.

  From the engine combustion chamber, blow-by gas leaks into the crankcase through the gap between the piston and the cylinder wall. In order to reduce the blow-by gas to the combustion chamber for combustion treatment, the engine is provided with a blow-by gas recirculation device. Lubricating oil is mixed into the blow-by gas in the crank chamber, so in order to reduce the blow-by gas in the crank chamber to the combustion chamber using the blow-by gas recirculation device, the blow-by gas is separated into gas and liquid to separate the oil droplets. Need to be separated from.

  In order to perform gas-liquid separation while guiding the blow-by gas in the crank chamber to the outside of the crank chamber, an in-shaft passage for guiding the gas to the outside of the crank chamber is formed in the crankshaft. The in-shaft passage has a separation passage that opens to the balance weight of the crankshaft, that is, the outer peripheral surface of the crank web and extends radially to the center portion of the crankshaft, and an axial passage that extends from the center portion of the separation passage to the journal. ing.

  In order to guide the blow-by gas flowing into the axial passage to the outside of the crankcase, Patent Document 1 incorporates a blow-by gas collector between two bearings supporting the end of the crank shaft, and a breather pipe A blow-by gas discharge device adapted to be connected is described. In the crankcase deaeration device described in Patent Document 2, a connection passage extending in the axial direction is formed on the central axis on one end portion side of the crankshaft, and this connection passage is opened on an end surface of the crankshaft. . On the other hand, a connecting passage extending in parallel to the central axis is formed on the other end portion side of the crankshaft, and this connecting port communicates with a hollow chamber in the crankcase, and blow-by gas is connected to a connecting pipe communicating with the hollow chamber. It is supplied to an intake device, that is, an intake system. Further, Patent Document 3 describes a blow-by gas / oil separation device in which a communication passage formed in the central axis of the crankshaft is opened in a passage formed between a cylinder block and an outer front cover. Has been.

Japanese Patent No. 2776984 JP-A-9-242524 JP-A-8-246836

  In the conventional blow-by gas recirculation device, in order to circulate the blow-by gas to the intake system, an axial passage formed in the axial direction of the crankshaft and a radial direction opening to the outer peripheral surface of the crank web and reaching the axial passage A separation passage extending to the crankshaft is formed in the crankshaft, and oil droplets that flow into the separation passage together with blow-by gas are returned to the crank chamber by centrifugal force. In order to supply blow-by gas from which oil droplets have been separated by centrifugal force to an intake system, a blow-by gas collector is incorporated between two bearings and a breather pipe is connected thereto, as described in Patent Document 1. In this case, it is necessary to provide a blow-by gas collector in addition to the bearings in the crankcase, and the engine cannot be reduced in size and weight.

  In the deaeration device described in Patent Document 2, blowby gas from which oil droplets are centrifuged is supplied to a hollow chamber in the crankcase through a communication passage, and the blowby gas is returned from the hollow chamber to the intake system. . However, it is necessary to form a hollow chamber in the crankcase, and this type of blow-by gas recirculation device cannot reduce the size and weight of the engine. Further, as described in Patent Document 3, in order to return the blow-by gas from which oil droplets have been centrifuged to the intake device, a front cover that forms a passage there between is provided outside the cylinder block. Still, the engine cannot be reduced in size and weight. Thus, none of the conventional blow-by gas recirculation devices has the problem that it is not possible to reduce the size and weight of the engine.

  An object of the present invention is to provide a blow-by gas recirculation device that can achieve a reduction in size and weight of an engine.

  The blow-by gas recirculation device of the present invention is a blow-by gas recirculation device for discharging the blow-by gas in the crank chamber of the crankcase to the outside, and is formed to open to the outer peripheral surface of the crank web and to extend radially to the crank web. A separation passage, an axial passage formed in the crankshaft extending in the axial direction and communicating with a central portion of the separation passage, and an outer peripheral surface of the journal formed in a radial direction on the journal and the axial passage. An in-shaft passage having a radial passage communicating therewith, a communication groove formed on an inner peripheral surface of a slide bearing for supporting the journal of the crankshaft in communication with the radial passage, and the communication to the crankcase And an exhaust passage that is formed in communication with the groove and supplies blow-by gas to the intake system.

  The blow-by gas recirculation device is characterized in that the communication groove is formed in an arc shape, and the communication groove communicates with the radial passage in the process of moving the piston from the top dead center to the bottom dead center. The blow-by gas recirculation device according to the present invention is characterized in that an oil droplet return passage for communicating the communication groove and the crank chamber is formed in the crankcase. The blow-by gas recirculation device of the present invention includes a first slide bearing that supports a journal on one end side of the crankshaft and a second slide bearing that supports a journal on the other end side of the crankshaft, respectively. Each of the communication grooves communicating with an exhaust passage for supplying the blow-by gas to an intake system is formed.

  According to the present invention, since the communicating groove communicating with the radial passage formed in the crankshaft is formed in the slide bearing, there is no need to provide additional parts such as a blow-by gas collector in addition to the bearing as in the prior art. The blow-by gas and oil droplets can be separated to return the blow-by gas to the intake system. By using a slide bearing provided in the crankcase, the blow-by gas can be returned and the oil droplets can be separated from the gas with a simple structure, greatly increasing the manufacturing cost of an engine having a blow-by gas recirculation device. Can be reduced.

  Providing an oil droplet return flow path in the crankcase can improve the separation performance between blow-by gas and oil droplets. In particular, when the engine is used in an inclined state, the separation performance is lowered in the prior art, but by providing an oil droplet return passage, the separation performance can be improved even if the engine is used in an inclined state. .

It is sectional drawing which shows the engine provided with the blowby gas recirculation apparatus which is one embodiment of this invention. It is an AA line expanded sectional view in FIG. It is the BB sectional view taken on the line in FIG. It is a time chart which shows the up-and-down movement stroke of a piston. It is sectional drawing which shows the principal part of the blowby gas recirculation apparatus which is other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The engine shown in FIG. 1 is a sectional view showing a one-cylinder four-cycle engine, and has a crankcase 11 on which a crankshaft 10 is rotatably mounted. A piston 13 is incorporated in a cylinder 12 provided in the crankcase 11 so as to reciprocate in the axial direction. Both end portions of the crankshaft 10 are journals 14a and 14b. On the axially inner sides of the respective journals 14a and 14b, balance weights extending in the radial direction, that is, crank webs 15a and 15b are integrally provided. Arms 16a and 16b extending in the opposite direction to the crank webs 15a and 15b are integrated with the base ends of the crank webs 15a and 16b. A crank pin 17 is provided between the arms 16 a and 16 b, and a large end portion of a connecting rod 18 for connecting the piston 13 to the crank shaft 10 is fitted to the crank pin 17. A small end portion of the connecting rod 18 is fitted to a piston pin 19 attached to the piston 13.

  A cylinder head 21 is mounted on the top of the cylinder 12, and a combustion chamber 22 is formed by the cylinder head 21, the inner peripheral surface of the cylinder 12, and the piston 13. An intake port and an exhaust port (not shown) are formed in the cylinder head 21, and an ignition plug (not shown) that ignites the mixed gas supplied into the combustion chamber 22 is provided in the cylinder head 21. When the air-fuel mixture supplied into the combustion chamber 22 is ignited by the spark plug in a state compressed by the upward movement of the piston 13, the air-fuel mixture in the combustion chamber burns, and the piston 13 is driven downward. FIG. 1 shows a state where the piston 13 has moved to the position of the bottom dead center. An intake valve (not shown) that opens and closes the intake port and an exhaust valve (not shown) that opens and closes the exhaust port are driven to open and close by a camshaft provided in the cylinder head 21. A timing transmission device 24 meshing with a gear 23 attached to the crankshaft 10 is stretched over a gear (not shown) attached to the camshaft, and the intake valve and the exhaust valve are driven to open and close by the crankshaft 10, respectively. From the engine combustion chamber 22 to the crank chamber 25 in the crankcase 11, the blow-by gas leaks through the gap between the joint gap between the piston 13 and the piston ring 13 a and the inner peripheral wall of the cylinder 12.

  In each crank web 15a, 15b, separation passages 26a, 26b that open to the respective outer peripheral surfaces are formed to extend in the radial direction. Even if the oil droplets mixed in the blow-by gas enter the separation passages 26a and 26b together with the blow-by gas, the oil droplets are out of the radial direction by the centrifugal force applied to the oil droplets in the separation passages 26a and 26b extending in the radial direction. Will be scattered. Since the density of the oil droplets is about 800 times that of the gas, even if the oil droplets enter the separation passages 26a and 26b together with the blow-by gas, the oil droplets are returned to the crank chamber 25 by centrifugal force. .

  At both ends of the crankshaft 10, axial passages 27a and 27b communicating with the radial center portions of the separation passages 26a and 26b are formed extending in the axial direction. Each of the axial passages 27a and 27b is formed by drilling from the end face of the crankshaft 10 with a drill, and each end face is closed after processing. The journals 14a and 14b are formed with radial passages 28a and 28b extending in the radial direction. The radial passage 28a opens on the outer peripheral surface of the journal 14a, and the radial passage 28b opens on the outer peripheral surface of the journal 14b. Yes. As the number of radial passages 28a and 28b, a plurality of radial passages 28a and 28b may be formed in the radial direction, or may be formed so as to penetrate the journals 14a and 14b.

  The separation passage 26a, the axial passage 27a, and the radial passage 28a constitute an in-shaft passage 29a. Similarly, the separation passage 26b, the axial passage 27b, and the radial passage 28b constitute an in-shaft passage 29b. In FIG. 1, the left in-shaft passage 29a forms a first in-shaft passage, The in-shaft passage 29b forms a second in-shaft passage. The sliding bearing 31a forms a first sliding bearing, and the sliding bearing 31b forms a second sliding bearing.

  The crankcase 11 is provided with sliding bearings 31a and 31b for rotatably supporting the journals 14a and 14b at both ends of the crankshaft 10. As shown in FIG. 2, a communication groove 32a communicating with the radial passage 28a extends in the circumferential direction and is formed in an arc shape on the inner peripheral surface of the slide bearing 31a. As shown in FIG. 2, under the process in which the piston 13 is driven from the top dead center (TDC) to the bottom dead center (BDC), an arcuate shape is formed so that the communication groove 32a communicates with the radial passage 28a. The circumferential length of the communication groove 32a is set. In the case shown in FIG. 2, when the crankshaft 10 rotates clockwise as indicated by an arrow in FIG. 2, the radial passage 28a starts to communicate with the communication groove 32a before the piston 13 reaches the top dead center. After 13 reaches the bottom dead center, it communicates to an angle slightly past the bottom dead center. A communication groove 32b communicating with the radial passage 28b is also formed in an arc shape on the inner peripheral surface of the slide bearing 31b in the circumferential direction, and has the same shape as the communication groove 32a.

  In the process in which the piston 13 moves from the top dead center toward the bottom dead center, the inside of the crank chamber 25 is compressed by the piston 13, and under this process, the radial passages 28a and 28b are connected to the communication groove 32a. , 32b, the blowby gas is pressurized and introduced into the in-shaft passages 29a, 29b.

  The crankcase 11 is formed with exhaust passages 33a and 33b communicating with the respective communication grooves 32a and 32b. The crankcase 11 is provided with intake pipes 35a and 35b communicating with the exhaust passages 33a and 33b by joints 34a and 34b. Blow-by gas discharged into the exhaust passages 33a and 33b is not shown through the intake pipes 35a and 35b. Supplied to the intake system.

  As shown in FIGS. 2 and 3, an oil droplet return flow path 36 is formed in the crankcase 11 in order to connect the communication groove 32 a and the crank chamber 25. Oil droplets that have flown in the blow-by gas through the axial passage 27a and the radial passage 28a to the communication groove 32a without being separated from the blow-by gas in the separation passage 26a are supplied to the crank chamber by the oil drop return passage 36. 25 is returned. A gap is formed between the opening on the crank chamber 25 side of the oil droplet return flow path 36 so as not to be covered by the step of the crankshaft 10. However, as indicated by a two-dot chain line in FIG. 3, a concave groove 37 communicating with the opening may be formed on the inner surface of the crankcase 11. The crankcase 11 is provided with a similar oil droplet return passage for communicating the communication groove 32 b with the crank chamber 25. As shown in FIG. 2, the oil droplet return passage 36 is formed to communicate with the downstream side in the rotation direction of the crankshaft of the arc-shaped communication groove 32b, and the oil droplets flowing into the communication groove 32a are journals. The oil 14 is guided to the oil droplet return flow path 36 in a state of adhering to the outer peripheral surface of 14a, and is returned from the oil droplet return flow channel 36 into the crank chamber 25. Thereby, the separation efficiency of blow-by gas and oil droplets can be increased.

  FIG. 4 is a time chart showing the vertical movement stroke of the piston 13. The four-stroke engine compresses the intake stroke when the piston 13 moves downward from the top dead center (TDC) position toward the bottom dead center (BDC) position and the upward movement toward the top dead center of the piston 13. A compression stroke to be performed, an expansion stroke in which the air-fuel mixture is ignited and burned by the spark plug in a compressed state, and the piston 13 is moved downward toward the bottom dead center position by the combustion pressure, and the piston 13 is moved upward. And an exhaust stroke for exhausting the combustion gas. The crankshaft 10 is converted into rotational motion by the upward movement and downward movement of the piston 13.

  In the above-described engine, the blow-by gas leaked into the crank chamber 25 is mixed with oil droplets scattered in the crank chamber 25 to form a mixed fluid. The mixed fluid is separated into gas and oil droplets by centrifugal force applied to the oil droplets whose density is extremely higher than that of the gas when flowing in the separation passages 26a and 26b where the centrifugal force works from the radially outer side toward the inner side. Most of the oil droplets are returned to the crank chamber 25. The gas from which the oil droplets have been separated flows into the communication grooves 32a and 32b through the axial passages 27a and 27b and the radial passages 28a and 28b. In FIG. 4, when the piston 13 moves downward from the top dead center position toward the bottom dead center position and the pressure in the crank chamber 25 becomes higher than the atmospheric pressure, the radial passages 28a and 28b are connected to the communication grooves 32a and 32b. You will communicate. On the other hand, when the piston 13 moves upward from the bottom dead center position toward the top dead center position and becomes lower than the atmospheric pressure, the radial passages 28a and 28b are closed.

  As described above, when the communication grooves 32a and 32b are provided with a valve function, only the gas having a predetermined pressure or higher can be discharged to keep the crank chamber 25 at an arbitrary pressure.

  Since the oil droplets mixed with the gas in the communication grooves 32a and 32b are always circulated to the crank chamber 25 by the oil droplet return passage 36, it is possible to completely prevent the lubricating oil from being discharged outside the engine. The separation performance between gas and oil droplets can be improved. That is, the pressure in the crank chamber 25 is lower than the pressure in the communication grooves 32a and 32b. Therefore, when the crank chamber 25 and the crank chamber 25 are communicated with each other by the small-diameter oil droplet return passage 36, the communication chambers 32a and 32b are connected to the crank chamber. A minute flow can be created in the cylinder 25, and the lubricating oil mixed in the communication grooves 32a and 32b can be constantly circulated into the crank chamber 25.

  As shown in FIG. 1, communication grooves 32a and 32b are provided in both sliding bearings 31a and 31b corresponding to the journals 14a and 14b at both ends of the crankshaft 10. Function can be obtained. However, when the diameters of the journals 14a and 14b are small and the diameter of the axial passage cannot be increased, the flow grooves 32a and 32b are provided in both the sliding bearings 31a and 31b as shown in FIG. Is preferably ensured.

  5 is a cross-sectional view showing the main part of a blow-by gas reflux device according to another embodiment of the present invention.

  In the case shown in FIG. 5, the communication groove 32a formed in the sliding bearing 31a of the crankcase 11 is annular. Thus, the radial passage 28a always communicates with the communication groove 32a regardless of the position of the piston 13 in the vertical direction. The radial passage 28a is formed through the journal 14a. FIG. 5 shows the structure of the left journal 14a in FIG. 1, but the communication groove 32b in the other journal 14b may also be annular. As shown in FIG. 5, in the case of a continuous communication mode, if a check valve is provided in the exhaust passages 33a and 33b, the same valve function as that shown in FIG. 2 can be provided.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, FIG. 1 shows a single cylinder engine, but the present invention can also be applied to a multi-cylinder engine.

10 Crankshaft 11 Crankcase 12 Cylinder 13 Piston 13a Piston ring 14a, 14b Journal 15a, 15b Crank web 21 Cylinder head 22 Combustion chamber 25 Crank chamber 26a, 26b Separation passage 27a, 27b Axial passage 28a, 28b Radial passage 29a, 29b In-shaft passages 31a, 31b Sliding bearings 32a, 32b Communication grooves 33a, 33b Exhaust passage 36 Oil droplet return passage

Claims (4)

A blow-by gas recirculation device for discharging the blow-by gas in the crank chamber of the crankcase to the outside,
A separation passage formed in the outer peripheral surface of the crank web and extending radially in the crank web; an axial passage formed in the crankshaft extending in the axial direction communicating with a central portion of the separation passage; and the journal An axial passage having a radial passage formed to extend in the radial direction and communicating the outer peripheral surface of the journal and the axial passage;
A communication groove formed on an inner peripheral surface of a slide bearing that supports the journal of the crankshaft and communicated with the radial passage;
A blow-by gas recirculation device having an exhaust passage formed in the crankcase so as to communicate with the communication groove and supplying blow-by gas to an intake system.   2. The blowby gas recirculation device according to claim 1, wherein the communication groove is formed in an arc shape, and the communication groove communicates with the radial passage in a process in which a piston moves from a top dead center toward a bottom dead center. Blowby gas recirculation device characterized.   The blowby gas recirculation device according to claim 1 or 2, wherein an oil droplet return passage for communicating the communication groove and the crank chamber is formed in the crankcase.   4. The blow-by gas recirculation device according to claim 1, wherein a first sliding bearing that supports a journal on one end of the crankshaft and a journal on the other end of the crankshaft are supported. The blow-by gas recirculation device, wherein the communication groove is formed in communication with an exhaust passage for supplying the blow-by gas to the intake system.

Images