JPH071024B2 - Engine cylinder block structure - Google Patents

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 supporting the balancer shaft on the cylinder block as described above, the bearing part of the balancer shaft is formed on the bulkhead part connecting the main bearing part of the cylinder block to the cylinder bore part and the skirt part. .

(Problems to be Solved by the Invention) When the balancer shaft as described above is supported by the bearing portion of the bulkhead portion, the balancer shaft is driven to rotate at a high rotation speed and the eccentric load of the balance weight is applied. Due to this, a high surface pressure acts periodically, and therefore the lubrication conditions in the bearing portion are severe.

The bearing portion of the balancer shaft is connected to the cylinder bore portion via the bulkhead portion, and the heat generated by combustion causes the cylinder bore portion to reach a high temperature state, and the heat is transmitted through the bulkhead portion and the balancer shaft. It acts on the bearing part of, the oil temperature rises, and the lubrication conditions become more severe. That is, as the temperature of the bearing portion rises, the oil flowing in the bearing portion deteriorates, which may reduce the lubricating action and cause poor lubrication such as seizure.

In view of the above circumstances, it is an object of the present invention to provide an engine cylinder block structure in which heat transfer from a cylinder bore portion to a bearing portion of a balancer shaft is reduced to improve lubrication conditions. .

(Means for Solving the Problems) In the cylinder block structure of the present invention, when the balancer shaft having the balance weight is supported by the bearing portion of the bulkhead portion, the bulkhead between the bearing portion of the balancer shaft and the cylinder bore portion is supported. It is characterized in that a through hole is formed in the portion to block and reduce heat transfer.

(Operation) In the cylinder block structure, the heat generated by combustion of the engine is radiated to the outside from the cylinder bore through the bulkhead, but the heat generated by the through hole is formed in the bearing of the balancer shaft. A part of the transmission is cut off, the amount of heat transfer is reduced, the temperature rise of the oil fed to the bearing portion is moderated, and the lowering of the oil temperature maintains a good lubricating action.

(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 bulkhead 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-II
It is sectional drawing in a part.

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 arranged between the cylinders of the 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.

Further, a pair of left and right balancer shafts 4 and 5 in which the bulging portion 8 of the cylinder block side wall 1c is incorporated are arranged on both sides of the upper portion 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 communicates the space portions on both sides with the cylinder bore portion 1a in the portion adjacent to the bearing portions 6, 6. Through holes 7, 7 are formed.

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. In the bypass passage 9 and the oil gallery 10, the through holes 7 and 7 are formed between the bearing portions 6 and 6 of the balancer shafts 4 and 5 in the bulkhead portion 3 of the adjacent portion, and the through holes 7 and 7 are formed. The blow-by gas is circulated and heated when cold.

As shown in FIG. 2, the lubricating oil is supplied to the bearing portions 6 of the balancer shafts 4 and 5 by the oil supply passage 11 from the oil gallery 10 to the main bearing portion 2 and the bulk head portion 3 as shown in FIG. Is formed in the middle of the oil supply passage 11, and a branched oil passage 12 horizontally branched from the middle of the oil supply passage 11
The branch oil passages 12 are connected to the bearings 6, 6 and the lubricating oil is pumped to the bearing portions 6, 6 on both sides.

A cooling water passage 14 forming a water jacket is provided on the outer circumference 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. Further, the blow-by gas in the cylinder block 1 and the oil from the cylinder head are blow-by gas passage 17 and oil return passage extending upward from the expansion chamber 1d on the side of the cylinder block 1.
Flowing through 18.

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

The through holes 7, 7 of the bulkhead portion 3 block heat transfer to the bearing portions 6, 6, and in a cold engine state, blowby gas having a high temperature with respect to the operation of the piston accompanying the operation of the engine is Through hole of the bulkhead part 3
The cooling water flowing through the bypass passages 9 and 7 and the oil flowing through the oil gallery 10 are heated, the temperature rises quickly, and the warm-up performance is improved.

(Effect of the Invention) According to the present invention as described above, when the balancer shaft is supported by the bearing portion formed in the bulkhead portion of the cylinder block, the bulkhead portion has a through hole between the bearing portion and the cylinder bore portion. The temperature is reduced in the bearing part by keeping the amount of heat transfer from the cylinder bore part to the bearing part cut off and reducing the lubrication performance of the oil to prevent the occurrence of poor lubrication. can do.

[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, 2 …… Main bearing part 3 …… Bulkhead part 4,5 …… Balancer shaft 4a, 5a …… Balance weight 4b, 5b …… Journal part 6 ... Bearing, 7 ... Through hole 8 ... Swelling, 9 ... Bypass passage 10 ... Oil gallery 11 ... Oil supply passage 12 ... Branched oil passage

Claims (1)

[Claims] 1. A cylinder block of an engine, wherein a balancer shaft having a balance weight is built in a side wall of a cylinder block, and a bearing portion of the balancer shaft is formed in a bulkhead portion, the bearing portion of the balancer shaft and a cylinder bore portion. A cylinder block structure for an engine, characterized in that a through hole is formed in a bulkhead portion between the two.