JPH04347032A - Backlash adjusting method for gear driving type balancer - Google Patents

Abstract

PURPOSE:To lower rattling sound by measuring backlash at two places for the point of lowest speed and another two places closest to the point of unbalanced mass every one revolution of a crank shaft in a four cylinder engine, setting backlash at the point where the minimum backlash is indicated, as a target value, and thereby determining a shim to be used for adjusting the distance between axial centers. CONSTITUTION:A balancer assembly is fitted onto a cylinder block 2. Backlash between a crank gear 20 and a balancer gear 22 is measured at two places for the point of lowest speed at the crank angles of 30 deg. and 210 deg., and also at another two places closest to the point of unbalanced mass at the crank angles of 100 deg. and 280 deg., that is, at four places in total. When the width of dispersion for the measured backlash values is within an allowable range, a target shim is so determined that the backlash value at the point indicating the minimum value is made to be a target value. When the width of dispersion is equal to or more than the allowable value, a balancer has to be replaced, and it is then affirmed whether or not backlash is within the allowable range.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlash adjustment method for a gear-driven balancer in a four-cylinder engine.

0002

[Prior Art] In a four-cylinder engine, when the pistons of the No. 1 and No. 4 cylinders are at the top dead center position, the pistons of the No. 2 and No. 3 cylinders are at the bottom dead center position, but the pistons, connecting rods, etc. Due to the unbalance of the inertial force due to the inertial mass, an unbalanced force directed upward remains, and a similar unbalanced force directed upward remains even when the pistons of the No. 2 and No. 3 cylinders are at the top dead center position. Two vertical vibrations occur per crankshaft rotation.

In order to eliminate vibrations caused by the unbalance of inertial force due to the reciprocating inertial mass of the piston, connecting rod, etc., which is unique to this four-cylinder engine, an unbalanced mass is provided to balance the unbalance of inertial force due to the reciprocating inertial mass of the piston, connecting rod, etc. A balance shaft is provided, and the crankshaft 1
A balancer may be provided that rotates two revolutions per rotation. However, if only one balance shaft is provided, the vertical vibration caused by the secondary inertia force generated due to the unbalance of the inertia force due to the reciprocating inertial mass of the piston, connecting rod, etc. will be eliminated, but the horizontal vibration due to the unbalanced mass of the balance shaft itself will be eliminated. Since directional vibration occurs, in order to eliminate this, two balance shafts are installed,
Arrange them left and right and rotate them in the opposite direction to offset the left-right imbalance.

[0004] When two balance shafts are arranged below the crankshaft and the balance shafts are rotated in conjunction with the crankshaft, the rotation transmission method is as follows.
Conventionally, there are chain drive type, belt drive type, and gear drive type. For example, Japanese Patent Laid-Open No. 58-160647 discloses a gear drive type. Compared to chain-driven or belt-driven systems, the gear-driven type has the following advantages: it has less mechanical loss, and it is relatively easy to add a balancer to the cylinder block structure of an existing engine without a balancer without making major changes. While there are advantages, there are also the following problems, and countermeasures must be taken to address them.

[0005]

[Problems to be Solved by the Invention] In other words, a gear-driven balancer produces a relatively loud rattling noise (hereinafter referred to as
This produces a rattling sound. The magnitude of this rattling noise is particularly large when the distance between the axes between the crank gear and the balancer gear becomes large and the substantial backlash between the gears becomes large. If the backlash is made too small in order to reduce this rattling noise, the backlash between the crank gear and balancer gear becomes zero, resulting in gear damage.

[0006] Adjusting the distance between the axes of the crank gear and balancer gear for each engine in order to minimize rattle noise without causing gear damage would require an enormous amount of work and time. It was considered inappropriate to introduce this into an engine assembly line, and even if it could be adjusted, the balance shaft axis would move circularly within the metal clearance range because the balance shaft has an unbalanced mass. , it was thought that the distance between the axes of the crank gear and balancer gear would fluctuate, making it impossible to effectively suppress rattling noise.For this reason, in the past, manufacturing errors were taken to prevent backlash from becoming zero. In anticipation of this, the distance between the gears was set large, and the balancer was installed on the engine cylinder block without adjusting the distance between the crank gear and balancer gear. Therefore, noise countermeasures were sacrificed.

An object of the present invention is to provide a method for adjusting backlash between a crank gear and a balancer gear in order to reduce rattling noise in a gear-driven balancer. However, this inter-gear backlash adjustment method must be a method that can be executed for each engine in a relatively short time without causing damage to the gears due to zero backlash.

[0008]

[Means for Solving the Problems] According to the present invention, the above-mentioned object is to provide a gear in which the balance shaft rotates twice for each rotation of the crankshaft due to the meshing of the crank gear attached to the crankshaft and the balancer gear attached to the balance shaft. A backlash adjustment method for a driven balancer is achieved by including the following steps. That is, a step of measuring backlash at a total of 4 points per crankshaft rotation: 2 points of the crankshaft's lowest deceleration point, and 2 points of the closest mass point where the unbalanced mass of the balance shaft is closest to the crank gear; A step of determining a shim for adjusting the distance between the axes of the crank gear and balancer gear so that the backlash at the point showing the minimum backlash value among the four points becomes the target value.

[0009]

[Operation] Analysis of the occurrence of rattle noise revealed that rattle noise occurs twice per crankshaft rotation, and occurs at the crankshaft's maximum deceleration point (the point at which deceleration changes to acceleration). From this, the point at which to manage backlash due to balancer noise is 2 times per crankshaft rotation.
It turns out that this is the crankshaft's lowest deceleration point. In addition, if the backlash between gears becomes less than zero, it may lead to gear damage, and since backlash is minimized at the point where the unbalanced mass of the balance shaft is closest to the crankshaft, this point must also be managed for gear reliability. There is a need to. In the present invention, the backlash measurement point is defined as a rattle generation point and a dangerous point in terms of gear reliability, and by directly managing these points, gear noise and gear damage are effectively prevented.

[0010] Also, normally, when considering the variation width of the four measurement points (for example, 66 microns) in terms of processing accuracy,
Since the target value must be set for the sum of the variation between 4 points (66 microns) and the adjustment variation of each point (for example, ±24 microns), (for example, (2 × 2
4+66+α microns)/2, approximately 60 microns), the target value cannot be set to a small value considering gear damage. For this reason, in terms of processing accuracy, even if gears have small variations in backlash, since gears with large variations are taken into consideration in advance, backlash cannot be reduced. In the present invention, since a target value is determined for the minimum backlash value, the target value can be set small (for example, 30 microns). Therefore, the backlash setting of the product can be reduced. For example, if the variation at four points is 20 microns, if the target value is 60 microns, there is no problem even if it is set to 50-70 microns.
Set to 0-50 microns. In this way, in the present invention, by setting the backlash to a small value, the rattling sound of the balancer is suppressed to a minimum.

[0011] Also, the backlash at the point showing the minimum backlash value among the four measurement points is set to a target value (for example, 3
0 microns), so even if there is a variation in backlash adjustment error (for example, ±24 microns),
It is possible to prevent the occurrence of a state where the backlash is less than zero (for example, 30 microns - 24 microns = 6 microns,
There is still a margin of 6 microns), and gear damage will not occur.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-5 illustrate preferred embodiments of the invention. As shown in FIGS. 3 and 4, in a four-cylinder engine, a first balance shaft housing 6 and a second balance shaft housing 8 are fixed to a cylinder block 2 via a shim 4. cylinder block 2
A crankshaft 10 is rotatably supported by the first
There are two balance shafts 12 between the second balance shaft housing 6 and the second balance shaft housing 8.
, 14 are rotatably supported.

The two balance shafts 12 and 14 are arranged symmetrically below the crankshaft 10. The crankshaft 10 extends in the longitudinal direction of the engine, and the two balance shafts 12, 14 also extend in the longitudinal direction of the engine. The two balance shafts 12 and 14 are arranged near the longitudinal center of the crankshaft 10. The two balance shafts 12 and 14 each have an unbalanced mass 1
6 and 18, and the sum of these unbalanced masses 16 and 18 balances the unbalance of inertial force due to reciprocating inertial masses such as pistons and connecting rods in the vertical direction of the engine.

Of the two balance shafts 12 and 14, one balance shaft 12 is driven by a gear from the crankshaft 10, and the other balance shaft 14 is driven by a gear from the one balance shaft 12. The two balance shafts 12, 14 are rotated in opposite directions, thereby balancing the unbalanced masses 16, 18 in the left-right direction.

[0015] The crankshaft 10 has a crank gear 2.
0 is connected, a balancer gear 22 is connected to the balance shaft 12, and a balancer gear 24 is connected to the balance shaft 14. Then, the crank gear 20 and the balancer gear 22 are engaged with each other, and the balancer gear 22 and the balancer gear 24 are engaged with each other. The meshing region between the crank gear 20 and the balancer gear 22 is offset from the meshing region between the balancer gear 22 and the balancer gear 24 in the longitudinal direction of the engine. The balancer gears 22 and 24 are connected to the balance shaft housing 26 so that the rotation of the balancer gears 22 and 24 does not stir up the oil in the engine oil pan 26.
, 8.

The axis of the balancer gear 22 and the crank gear 2
The distance between the shim 4 and the axial center, and thus the backlash between gears, changes depending on the thickness of the shim 4. This shim thickness selection is set to reduce balancer noise. However, it should be ensured that the backlash is not set too small and a state where the backlash is zero will occur due to variations in gear machining accuracy and backlash adjustment. In order to make this type of backlash adjustment possible, we investigated the mechanism by which balancer gear noise is generated.

FIG. 2 shows the results of analyzing the rattling sound caused by the balancer when the engine is idling. As shown in FIG.
This occurs at positions where the crankshaft 10 has rotated 30° and 210° from the top dead center position of the piston of the first cylinder. In terms of crank rotation fluctuations, the positions of 30° and 210° are the maximum deceleration points of the crank, and correspond to the points where deceleration changes to acceleration. That is, during deceleration, the teeth of the crank gear 20 hit the front side of the teeth of the balancer gear 22 in the rotating direction, but during acceleration, the teeth of the crank gear 20 change to hit the rear side of the teeth of the balancer gear 22 in the rotating direction. Since there is a backlash gap between the gears, it is thought that the collision results in a collision, which generates the noise. At the 30° and 210° positions of the crankshaft 10, the unbalanced mass 16 of the balance shaft 12 is on the far side from the crankshaft 10, as shown in FIG. It is located far from the shaft 10 by approximately the metal clearance, and the backlash between the gears is large. Therefore, the collision sound becomes louder. From the above rattle noise analysis, we found that the two points (30°, 2
10°) is considered to be a desirable reference point for noise reduction and backlash management.

[0018] In adjusting the backlash, it is necessary to control the backlash so that it does not become less than zero, also from the viewpoint of preventing damage to the gear. Since the balance shaft 12 has an unbalanced mass 16, the balance shaft 12
The shaft center performs circular motion by the amount of metal clearance of the bearing. As a result, the backlash between gears varies depending on the rotational position of the unbalanced mass 16. When the unbalanced mass 16 of the balance shaft 12 comes to the position closest to the crankshaft 10 (100° and 280° in crank angle after the piston top dead center), the backlash is at its smallest. It appears twice per revolution of the shaft 10. This point also becomes a desirable reference point in managing backlash.

[0019] In order to suppress gear noise, it is better to reduce the amount of backlash as much as possible. However, backlash cannot be reduced to less than zero due to gear reliability. Taking these two conditions into account, the backlash is measured at the four reference points shown in Figure 1, and then the backlash at the point that shows the minimum value of the four points above is adjusted to the target value. do.

FIG. 5 is a flowchart showing an example of steps according to this backlash adjustment method. This adjustment method has two stages. The first stage is a stage for determining the target shim, and the second stage is a stage for checking whether the amount of backlash is within the tolerance. An essential condition of the invention lies in steps 104, 110 of the first stage.

FIG. 5 will be explained in more detail. First, in step 102, a balancer assembly (including a balance shaft, balancer gear, and balance shaft housing) is assembled to a cylinder block via a master shim. The thickness of the master shim is set larger than that of the shim 4 that is actually assembled into the engine so that the measured backlash does not become less than zero.

Next, in step 104, the amount of backlash between the crank gear 20 and the balancer gear 22 is calculated for the balancer assembly assembled via the master shim.
Measurement is performed at four points shown in Figure 1. That is, crank angle 3
The amount of backlash is measured at a total of four points: two points of maximum deceleration of the crankshaft at 0° and 210°, and two points closest to the crankshaft of the unbalanced mass at crank angles of 100° and 280°.

Backlash is measured by restricting the rotation of either the crank gear 20 or the balancer gear 22, and measuring how much the other moves in the circumferential direction within the range of backlash in terms of gear pitch circle equivalent diameter. Do it by doing this. Measurement is performed by magnifying the rotation of the gear with a lever and measuring the amount of movement of the tip of the lever with a dial gauge.

Next, in step 106, it is determined whether the variation range of backlash values (maximum value - minimum value of backlash values) at the four measurement points obtained is within a predetermined variation tolerance value (for example, 66 microns). Determine. If it is within the allowable value, proceed to step 110;
If the tolerance is exceeded, the balancer is determined to be defective in step 108, and another balancer is selected for replacement, and the process returns to step 102.

In step 110, a target shim is determined to set the backlash at the point showing the minimum value of the backlash value to the target value at the point showing the minimum value among the four measurement points. For example, if the backlash values measured at four points using the master shim were 125 microns, 130 microns, 145 microns, and 150 microns, and the target value was 30 microns, then the point that showed the minimum value of 125 microns To set the backlash value of 30 microns to target shim 4, set the backlash value to 95 microns (=12
A thin shim with a thickness of 5-30 microns (5 to 30 microns) may be selected. In this way, the target sim is determined. Then, in step 112, the master sim is replaced with the target sim. This allows the minimum backlash to be set to the target value.

Next, the process proceeds to step 114 of the second stage, where the cylinder block 2 and balancer housings 6, 8 are assembled.
The backlash between the crank gear 20 and the balancer gear 22 when the target shim 4 is interposed therebetween is measured again at the four measurement points. And step 1
In step 16, is the adjusted backlash value of the point showing the minimum backlash value (target point) within the range of the target value (30 microns in the above example) ± a constant value (for example, 24 microns)? If it is not within this range, there is a problem in selecting the target shim, so the process proceeds to step 118, replaces the target shim with another shim, and returns to step 114 again.

In step 120, it is checked whether the backlash at any of the four measurement points other than the target point is within an allowable value. For example, it is checked whether the maximum deceleration point of the crankshaft is within a range of 5 to 105 microns, and the closest mass point is within a range of 15 to 135 microns. If it is within this range, it is assumed that the backlash adjustment is complete and the process proceeds to step 122, where the backlash adjustment for that balancer is completed.If it is not within this range, the process proceeds to step 118 and the target shim is replaced with another shim. The process returns to step 114 again.

In the above backlash adjustment, the time required for backlash adjustment and target shim determination in steps 104, 106, and 108 of the first stage is approximately 45 minutes.
seconds, steps 114, 116, 1 of the second stage
The time required for checking 20 is about 45 seconds, so it is a short time, and the balancer assembly and backlash adjustment can be carried out on the engine assembly line.

[0029]

Effects of the Invention The effects of the above backlash adjustment method are as follows. First, normally (for example, when using an average value), the target value cannot be set small considering variations in machining accuracy, but since the minimum value is used, the target value can be set small, and furthermore, backlash can be reduced. If the variation is small, the backlash can be further reduced, so the backlash setting of the product can be reduced, and rattle noise can be effectively suppressed. Second, by directly managing the points where rattling noise occurs (the two points at the lowest crank deceleration point) and the points at risk of gear reliability (the two points closest to the mass), rattle noise can be suppressed and gear damage can be prevented. Can be done effectively.

Thirdly, in order to adjust the backlash at the point showing the minimum value of the four measurement points to the target value, the backlash due to the dispersion of the backlash at the four points when the gear machining accuracy is poor is determined to be less than zero. Occurrence can be prevented. Fourth, there are only four measurement points, and the master shim only needs to be replaced with the target shim once, so backlash adjustment can be done in a relatively short time and can be incorporated into the engine assembly line. .

[Brief explanation of the drawing]

FIG. 1 is a front view of a crank gear and a balancer gear showing measurement points in a backlash adjustment method for a gear-driven balancer according to the present invention.

FIG. 2 is a diagram illustrating the relationship between crank rotational fluctuations, the rotational position of an unbalanced mass of a balance shaft, and the generation timing of a rattling sound, showing an analysis state of the rattling sound.

FIG. 3 is a front view of a gear-driven balancer according to an embodiment of the present invention.

FIG. 4 is a side view of the device of FIG. 3;

FIG. 5 is a flowchart showing the order of operations for backlash adjustment.

[Explanation of symbols]

2 Cylinder block 4 Shim 6 (first) balance shaft housing 8 (
2nd) balance shaft housing 10 crankshaft 12 balance shaft 14 balance shaft 16 unbalance mass 18 unbalance mass 20 crank gear 22 balancer gear 24 balancer gear

Claims (1)

[Claims] 1. A backlash adjustment method for a gear-driven balancer in which the balance shaft rotates twice for each rotation of the crankshaft due to engagement between a crank gear attached to the crankshaft and a balancer gear attached to the balance shaft, the method comprising: For each rotation, backlash is measured at a total of 4 points: the 2 points of the crankshaft's lowest deceleration point, and the 2 points of the closest mass where the unbalanced mass of the balance shaft is closest to the crank gear.
A back of a gear-driven balancer, characterized in that a shim for adjusting the distance between the axes of a crank gear and a balancer gear is determined so that the backlash at a point showing the minimum backlash value among the points becomes a target value. Lash adjustment method.