JPH071004B2 - Engine cylinder block structure - Google Patents

Abstract

PURPOSE:To effectively utilize space, by spreading the upper of cylinder block side walls, which form swollen parts with built-in balancer shafts, in the lengthwise direction of an engine to form spread chambers and forming an oil return passage through the spread chamber. CONSTITUTION:A pair of right and left balancer shafts 4, 5, built in swollen parts 8 of cylinder block side walls 1c, are provided to be arranged in upper both sides of a main bearing part 2 of a cylinder block 1. In the cylinder block side walls 1c, spread chambers 1d, which are formed protruding to the outside while spreading in the lengthwise direction of the cylinder block 1, are provided to be arranged in the upper of the swollen parts 8. An oil return passage 18, which extends in the vertical direction, passes through the spread chamber 1d, and the spread chamber 1d is opened downward so as to constitute one part of said oil return passage 18.

Description

TECHNICAL FIELD The present invention relates to a cylinder block structure of an engine in which a balancer shaft is built in a cylinder block.

(Prior Art) Conventionally, for example, as shown in Japanese Patent Publication No. 57-44863, in order to cancel the vibration due to the secondary reciprocal inertial force generated in the vertical direction due to the operation of the multi-cylinder engine. In addition, a technique is known in which a balancer shaft having a balance weight is rotationally driven in association with the rotation of a crankshaft.

Further, in order to incorporate the balancer shaft in the cylinder block as described above, generally, the side wall of the cylinder block is formed to bulge outward and is installed in this bulging portion. On the other hand, an oil return passage is formed in the cylinder block in the vertical direction to return the oil from the cylinder head to the oil pan.

(Problems to be Solved by the Invention) When the balancer shaft is built in the side wall of the cylinder block as described above, a large load acts on the bearing portion due to the eccentric load of the balance weight as the balancer shaft rotates. Therefore, it is necessary to improve the support rigidity.

On the other hand, the return oil flowing down from the cylinder head by the oil return passage formed in the cylinder block is
There is a problem that the oil immediately enters the crankcase from the oil return port, is agitated by the crankshaft, and air is mixed into the oil to cause turbidity. Further, the oil mist is mixed in the blow-by gas, and the oil consumption increases.

In view of the above circumstances, the present invention provides a cylinder block structure for an engine, which improves rigidity of a side wall of a cylinder block that incorporates a balancer shaft, prevents turbidity of return oil, and separates blow-by gas from oil. It is intended.

(Means for Solving Problems) In the cylinder block structure of the present invention, the balancer shaft is built in the bulging portion formed on the side wall of the cylinder block, and the side wall of the cylinder block above the bulging portion is arranged in the longitudinal direction of the engine. The present invention is characterized in that an enlarged chamber is formed by enlarging and an oil return passage from above is formed through the enlarged chamber.

(Operation) In the above cylinder block structure, the expansion chamber is formed above the bulging portion of the cylinder block containing the balancer shaft, and this expansion chamber improves the rigidity of the side wall of the cylinder block, which in turn increases the support rigidity of the balancer shaft. improves. In particular, the expansion chamber can reinforce the connecting node portion between the cylinder portion and the skirt portion of the cylinder block, and the rigidity is improved.

Also, the direction of the return oil flowing down the oil return passage is changed in the expansion chamber formed on the way and the flow velocity is eased, the amount of oil directly hitting the crankshaft is reduced, and the oil turbidity due to the mixing of air is eliminated, In addition, the generation of oil mist is reduced, and the mixing of oil in blow-by gas is reduced. Further, the blow-by gas flows upward through the expansion chamber, but the mixed oil in the blow-by gas is separated and removed by the oil separation action due to the change of the passage area and direction by the expansion chamber, and the oil consumption is reduced.

(Examples) Examples of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view of the cylinder block at the bore center, FIG. 2 is a cross-sectional view of the bulk bed portion between the bores, FIG. 3 is a side view, and FIG. 1 is an I-I portion of FIG. And Fig. 2 is II-
It is a sectional view in the II portion.

A plurality of bore portions 1a are arranged in series at the center of the upper portion of the cylinder block 1, and a piston (not shown) is fitted in the bore portion 1a so as to be vertically reciprocally movable. Also, cylinder block 1
Has a skirt portion 1b extending on both sides of the lower portion, and the bore portion 1a
A main bearing portion 2 that supports a crankshaft 25 (see FIG. 4) is disposed below the. The main bearing portion 2 is installed between cylinders of a bore portion 1a arranged in series, and the main bearing portion 2, the bore portion 1a and the skirt portion 1b are connected by a bulkhead portion 3 having a partition shape.

A pair of left and right balancer shafts 4 and 5 built in the bulging portion 8 of the cylinder block side wall 1c are disposed on both upper sides of the main bearing portion 2. This left and right balancer shaft
4,5 includes balance weights 4a and 5a formed eccentrically, and front and rear end and intermediate journal portions 4b and 5b are supported by bearing portions 6 and 6 formed on the bulkhead portion 3. The bulkhead portion 3 having the bearing portions 6, 6 for supporting the balancer shafts 4, 5 has through holes 7, 8 for communicating the space portions on both sides.
7 are formed.

Further, in the cylinder block side wall 1c, an expansion chamber 1d is formed above the bulging portion 8 containing the balancer shafts 4 and 5 so as to protrude outward and expand in the longitudinal direction of the cylinder block 1. Has been done. Above expansion room
In the right part of FIG. 2, 1d passes through the oil return passage 18 extending in the vertical direction, and the lower portion is opened so as to form a part of the oil return passage 18. On the other hand, in the left-side expansion chamber 1d, a vertically extending blow-by gas passage 17 also passes, and the lower part thereof is opened so as to form a part of the blow-by gas passage 17.

A bypass passage 9 through which cooling water flows is formed in the lower portion of the bore portion 1a of the cylinder block 1 so as to extend in the longitudinal direction of the cylinder block 1 and integrally with the bore portion 1a. Further, an oil gallery 10 which extends in the longitudinal direction of the cylinder block 1 is also formed in the lower portion of the bore portion 1a opposite to the bypass passage 9. The bypass passage 9 and the oil gallery 10 are formed adjacent to the inside of the expansion chambers 1d, 1d.

As shown in FIG. 2, the lubricating oil is supplied to the bearing portions 6, 6 of the balancer shafts 4, 5 as described above.
An oil feed passage 11 is formed in the bulkhead portion 3 from the main bearing portion 2 from the main bearing portion 2, and a branched oil passage 12 horizontally branched from the middle of the oil feed passage 11 has bearing portions 6 on both sides.
The oil for lubrication is pumped to the bearings 6, 6 on both sides by being connected to the bearings 6, 6.

A cooling water passage 14 forming a water jacket is provided on the outer periphery of the bore portion 1a of the cylinder block 1. On the other hand, on the side surface of the cylinder block 1, the inflow port 9a of the bypass passage 9 is opened.
Is a thermostat case 16 for mounting the thermostat 15
Via a water pump (not shown) attached to the water pump body 19 through the thermostat.
15 opens and closes communication to the water pump. Further, the thermostat case 16 is provided with a heater return passage connection port 16a.

On the other hand, as shown in FIG. 4, the drive mechanism for the balancer shafts 4 and 5 has a drive gear 20 fixed to the front end of the left balancer shaft 4 and an intermediate gear 21 having a gear 21 meshing with the drive gear 20. A shaft 22 is provided on the cylinder block 1, and a chain sprocket 23 that rotates integrally with the gear 21 is fixed to the intermediate shaft 22. A chain sprocket 24 is provided at the front end of the right balancer shaft 5.

And the chain sprocket 26 of the crankshaft 25
And a chain 27 is respectively wound around the intermediate shaft 22 and the chain sprockets 23 and 24 of the right balancer shaft 5, and the right balancer shaft 5 remains as it is with respect to the rotation of the crankshaft 25 and the left balancer shaft 4
Are rotationally driven via the intermediate shaft 22, and the left and right balancer shafts 4 and 5 are rotationally driven in mutually opposite directions. The balancer shafts 4 and 5 are rotationally driven at a speed twice that of the crankshaft 25, and the rotational phase is such that the balance weights 4a and 5a are eccentric downward when the piston is at the top dead center or the bottom dead center. It is provided to do. In addition,
28 is a chain tensioner, and 29 and 30 are guide members.

In the above-mentioned structure, the bulging portion 8 of the cylinder block side wall 1c in which the balancer shafts 4 and 5 are built is formed such that the thermostat case 16 is continuous on the front end side to increase the rigidity, and from the middle portion to the rear portion. The expansion chamber 1d is continuously formed to increase the rigidity.

Further, the expansion chamber 1d of the oil return passage 18 reduces the flow velocity of the oil, and when the engine is cold, the return oil whose temperature has risen due to the operation of the engine comes into contact with the portion of the bypass passage 9 inside. The cooling water flowing through the tank is heated, the temperature rises quickly, and the warm-up performance is improved.

(Effect of the Invention) According to the present invention as described above, since the expansion chamber is formed by utilizing the upper space of the bulging portion containing the balancer shaft, the expansion chamber can be formed compactly, and
By connecting the side wall of the cylinder block and the bulging portion by the expansion chamber and particularly reinforcing the joint portion, the rigidity of the entire cylinder block can be improved and the support rigidity of the balancer shaft can be increased.

Further, it is possible to reduce the flow velocity of the return oil in the expansion chamber and reduce the agitation by the crankshaft to suppress the inclusion of bubbles in the oil and to separate the oil in the blow-by gas.

[Brief description of drawings]

FIG. 1 is a sectional view of the cylinder block at the center of the bore in one embodiment of the present invention, FIG. 2 is a sectional view between the bores of the cylinder block, FIG. 3 is a side view of the cylinder block, and FIG. 4 is a balancer shaft. It is a principal part front view which shows a drive mechanism. 1 ... Cylinder block, 1a ... Bore part 1b ... Skirt part, 1c ... Side wall 1d ... Expansion chamber, 2 ... Main bearing part 3 ... Bulkhead part 4,5 ... Balancer shaft 4a, 5a ... … Balance weights 4b, 5b …… Journal part 6 …… Bearing part, 8 …… Swelling part 16 …… Thermostat case 17 …… Blow-by gas passage 18 …… Oil return passage

Claims (1)

[Claims] 1. A balancer shaft having a balance weight is built in a bulging portion formed on a side wall of a cylinder block, and a side wall of the cylinder block above the bulging portion is enlarged in a longitudinal direction of an engine to form an expansion chamber, A cylinder block structure for an engine, wherein an oil return passage from above is formed through the expansion chamber.