JP2547083Y2 - Shim structure of balance shaft casing - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine having a balance shaft for canceling an inertial force due to a reciprocating mass of the engine, and more particularly, to a clearance adjustment interposed between a balance shaft casing and a lower surface of an engine cylinder block. Related to the structure of the shim.

[0002]

2. Description of the Related Art There is known an engine in which a balance shaft driven from a crankshaft via a gear is provided below an engine cylinder block to cancel an inertial force due to a reciprocating mass of an engine piston or the like. An example of a supporting structure for rotatably supporting the balance shaft below the cylinder block is described in Japanese Patent Application Laid-Open No. 58-160647.

[0003] In the supporting structure of the publication, a balance shaft casing provided with a bearing for supporting the balance shaft is used, and this casing is fixed to the lower surface of the engine cylinder block with bolts, so that the balance shaft bearing is supported from the lower surface of the cylinder block. The shaft is held in a predetermined position.

When the balance shaft is driven from the crankshaft via a gear, it is necessary to precisely adjust the distance between the balance shaft and the crankshaft. If the distance between the shafts is not properly adjusted, the backlash of the balance shaft drive gear becomes insufficient or excessive, resulting in a reduction in gear life and an increase in noise.

The adjustment of the distance between the shafts can be performed by interposing an adjustment shim between the balance shaft casing and the lower surface of the cylinder block. That is, the shim is interposed in the mounting bolt portion between the cylinder block and the balance shaft casing, and a predetermined center distance is obtained by adjusting the thickness of the shim. In this case, the shim to be used is usually formed with a disk hole in the form of a disk washer in order to prevent misalignment when tightening the bolt, and the mounting bolt is inserted into this bolt hole to bolt the balance shaft casing. I have to.

[0006]

When the above assembling method is adopted, it is difficult to measure the distance between the shafts. Therefore, the shim thickness is actually adjusted by measuring the backlash of the driving gear. That is, first, a shim of the reference thickness called master shim is assembled into the mounting bolts, and the balance shaft casing is mounted on the lower surface of the cylinder block. In this state, the backlash of the drive gear is measured, and from this backlash amount, The thickness of the shim to be determined is determined, a shim having a required thickness is selected from several types of prepared shims, and the operation of replacing the shim with the master shim is performed. However, when using a washer-type shim as described above,
When this method is employed, the following problem occurs.

First, when the master shim is replaced with a shim having a predetermined thickness, the shim cannot be replaced unless the balance shaft casing is once removed, so that the man-hour is greatly increased and the work efficiency is reduced. In addition, since individual shims are used for each bolt part, the thickness of each shim varies within the shim manufacturing tolerance, so the tightening of the bolts may cause deformation of the balance shaft casing and deterioration of the balance shaft bearing metal This may cause a problem during high-speed operation.

The present invention solves the above-mentioned problems, and when the adjustment at the time of mounting the balance shaft casing is performed by a shim, the number of working steps can be significantly reduced, and deterioration of bearing performance due to variation in shim thickness can be prevented. An object of the present invention is to provide a shim structure of a casing.

[0009]

According to the present invention , a plurality of balance shaft casings are provided on the lower surface of an engine cylinder block , and a plurality of balance shaft casings are provided on both sides of a longitudinal axis of the casing.
A clearance adjustment shim interposed between the balance shaft housing and the cylinder block when mounted in bolt arranged at symmetrical positions with respect to the longitudinal axis by, disposed symmetrically on opposite sides with respect to said axis Wherein each of the shims has a notched bolt receiving groove which opens obliquely toward the axis in the bolt penetrating portion. A structure is provided.

[0010]

The shim can be inserted from both sides without removing the balance casing by providing a notched bolt receiving groove which opens obliquely toward the center axis of the balance casing in the bolt penetration portion of the shim. In addition, since the shims are integrated on one side of the balance casing and arranged so as to be symmetrical with respect to the axis of the balance casing, the types and the number of shims used are reduced. Furthermore, since the shim is formed into an integral shape, the bolt seat surface of each shim can be machined at the same time, so that variations in shim thickness at each bolt seat surface are eliminated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a bottom view showing the balance shaft casing mounting portion on the lower surface of the engine cylinder block 1, and FIG. 2 is a schematic side view of the cylinder block showing the positional relationship between the balance shaft 3 and the crankshaft 5. 2 is drawn upside down for clarity.

As shown in FIG. 2, the balance shaft 3 is provided at a lower portion of the crankshaft 5. A drive gear 7 provided at the shaft end of the crankshaft 5 is driven by an idler gear 9 and a driven gear provided at the shaft end of the balance shaft 3. Driven through 11 and.
FIG. 2 shows a balance shaft casing 13 that supports the balance shaft 3 by a chain line.

In this embodiment, the balance shaft casing 13 is attached to the lower surface of the cylinder block 1 by six bolts 15a to 15f symmetrically arranged with respect to a vertical plane including the central axis of the crankshaft (see FIG. 1). . Also 17
Reference numerals a and 17b denote oil supply holes for the balance shaft bearing and the gear 11 provided near the bolt 15a and 15b mounting portions, respectively, and communicate with oil supply passages provided in the balance shaft casing 13.

Reference numeral 21 in FIGS. 1 and 2 shows a shim for adjusting the center distance D (FIG. 2) according to the present invention. In this embodiment, the shim
21 are arranged one on each side with respect to the crank axis,
One shim covers the entire mounting bolt on one side. The shims on both sides have the same shape as shown in FIG. 3, and can be used on both sides of the casing 13 by turning the shims upside down.

As shown in FIG. 3, the shim 21 has a shape along the contact surface between the casing 13 and the lower surface of the cylinder block 1, and is formed integrally in the longitudinal direction along the crank axis. In this embodiment, the shim 21 has a shape in which a masking portion 23 for preventing oil from leaking from a connection portion between the oil supply holes 17a and 17b is provided integrally. Shim 21 bolts when mounting
Notch-shaped bolt grooves 25a to 25c are provided at portions where the holes 15 are inserted.

Each of the bolt grooves 25a to 25c is opened obliquely to the axis of symmetry 14 of the casing 13 and substantially parallel to each other. The reason why the bolt grooves 25a to 25c are opened obliquely is to avoid the interference between the oil supply hole masking portion 23 and the bolt groove 25a. Oil supply holes 17a, 17b
Usually, in order to prevent oil from leaking from the connection portion, the bolts 15a and 15b are arranged in the vicinity of the bolts 15a and 15b so as to securely tighten the bolts. Masking part 23 with 25c
Inevitable interference with In this embodiment, the
This problem is solved by inserting 21 obliquely with respect to the axis of symmetry 14.

The shim 21 reduces the number of processing steps by precisely processing only the periphery of the bolt grooves 25a to 25c and the masking portion 23 (shaded portions in FIG. 3) and managing them to predetermined tolerances. In addition, several kinds of shims 21 having different thicknesses are manufactured in advance so that variations due to processing tolerances of respective parts such as the cylinder block 1 and the balance shaft casing 13 can be adjusted.

The mounting of the balance shaft casing 13 using the shim 21 of the present invention is performed in the following procedure. First, sim
Instead of 21, a master shim having a reference thickness is assembled, the balance shaft casing 13 is assembled, and the bolts 15 a to 15 f are tightened with a predetermined tightening torque. The master shim has substantially the same shape as the shim 21, but has a constant thickness. Next, in this state, the backlash between the idler gear 9 and the gear 11 of the balance shaft is measured, and the thickness of the shim 21 to be used is determined according to the backlash amount.

Then, a shim of a required thickness is selected from the stock.
After selecting 21, remove the master shim by loosening the bolts 15a to 15f. At this time, the bolts 15a to 15f need only be loosened to the extent that the shim can be inserted and removed, and it is not necessary to completely remove the balance shaft casing 13 as in the related art.
After the master shim is extracted, the shim 21 having the required thickness selected above is inserted from an oblique direction of the casing 13, and the bolts 15a to 15f are tightened again with a predetermined tightening torque, thereby completing the mounting operation.

As described above, in the present invention, the bolt groove in which the shim 21 can be inserted obliquely with respect to the symmetry axis
By providing the 25, the distance between the shafts can be adjusted without removing the balance shaft casing 13, so that the work efficiency is greatly improved. In addition, since the shim 21 can simultaneously machine the masking portion 23 and the thickness control portions around the bolt grooves 25a to 25c, variations in thickness at these portions can be reduced. Therefore, there has been a case where a conventional shim is used. Variations in shim thickness at each bolt portion can be eliminated, and a problem that contact of the bearing metal is deteriorated after mounting can be prevented.

Furthermore, in the present invention, since the shims having the same shape are used on both sides of the balance casing, the types of shims are unified into one type, and the number of shims is reduced to two by integrating the bolt portions. (Conventionally, bolts 15a, 15
In part b, a shim of a different shape from that of the parts 15c to 15d is used for masking the lubrication hole, and two types of shims are required. Needed). As a result of the reduction in the types and the number of shims, the product cost of the shim can be reduced as a whole, and further, inventory management is facilitated, and the automatic shim supply device is advantageously reduced in size.

[0022]

[Effects of the Invention] The present invention makes it possible to drastically reduce the man-hour for mounting the balance shaft casing by adopting the above-mentioned shim shape, and to reduce the costs required for the manufacture, supply, inventory control, etc. of the shim. The effect that can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the mounting of a balance casing when the shim of the present invention is used.

FIG. 2 is a diagram showing a positional relationship between a crankshaft and a balance shaft.

FIG. 3 is a diagram showing an example of a shim shape according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine cylinder block 3 ... Balance shaft center axis line 5 ... Crank shaft 7, 9, 11 ... Gear 13 ... Balance shaft casing 15a to 15f ... Bolt 21 ... Shim

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshinori Shirai 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Katsuya Narusawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 56) References JP-A 2-83352 (JP, U) JP-A-62-163643 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] The method according to claim 1] balance shaft casing to the lower surface engine cylinder block, of the casing longitudinal axis
Each side a clearance adjustment shim interposed between the balance shaft housing and the cylinder block when mounted in bolt arranged at symmetrical positions with respect to the longitudinal axis by a plurality, relative to the axis 2 of the same shape arranged symmetrically on both sides
A shim structure for a balance shaft casing, comprising: a plurality of shims, wherein each of the shims has a notched bolt receiving groove which opens obliquely toward the axis in the bolt penetration portion.