JP2005016644A - Balance shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a balance shaft capable of compatibly establishing a reduction of its weight and maintaining the lubricating performance. <P>SOLUTION: The balance shaft 1 is equipped with a journal 6b supported rotatably by a bearing 2b. On the counter unbalance mass side 8 of the journal 6b, a neck part 9 is formed where the journal width as part thereof is set smaller than the journal width on the unbalance mass side 7. The journal 6b is provided internally with a lubrication passage 11 opening at its outer circumferential surface for supplying the lubricating oil to between the journal 6b and the bearing 2b. The opening 13 of the lubrication passage 11 is positioned in front in the shaft rotating direction of the position where the oil film pressure between the journal 6b and the bearing 2b maximizes. A groove 15 extending from the opening 13 toward the front about the shaft rotating direction to the neck part 9 is formed at the outer circumferential surface of the journal 6b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a balance shaft used for vibration suppression of an internal combustion engine.
[0002]
[Prior art]
During operation of the internal combustion engine, the inertial force generated with the reciprocating movement of the piston causes vibrations. In order to suppress the occurrence of such vibration, it is preferable to cancel the inertial force resulting from the reciprocating movement of the piston as much as possible. Therefore, conventionally, a balance shaft whose center of gravity is shifted from its rotational axis is provided in the internal combustion engine, and the balance shaft is rotated in synchronization with the crankshaft, thereby canceling out the inertial force.
[0003]
In such a balance shaft, lubricating oil is supplied between the journal and a bearing that supports the journal from a lubricating passage that is formed inside and opens to the journal, and an oil film is formed between them (for example, Patent Document 1).
[0004]
Here, the opening of the lubrication passage is set on the anti-unbalance mass side in the journal. This is due to the following reason. Since the center of gravity of the balance shaft is deviated from the axis thereof, the surface pressure between the outer peripheral surface of the journal and the inner peripheral surface of the bearing is different in the circumferential direction. That is, the surface pressure between the journal and the bearing located on the unbalance mass side is higher than the surface pressure located on the anti-unbalance mass side. For this reason, the pressure of the oil film between the journal and the bearing also differs depending on this surface pressure. Therefore, conventionally, the opening of the lubrication passage is formed on the anti-unbalance mass side where the oil film pressure is low.
[0005]
[Patent Document 1]
Japanese Utility Model Publication No. 57-102743 (2nd page, Fig. 1)
[0006]
[Problems to be solved by the invention]
By the way, as described above, since the oil film pressure between the journal and the bearing located on the anti-unbalance mass side is low, the shape on the anti-unbalance mass side is slightly changed so that the contact area between the journal and the bearing becomes small. Even so, the effect of the shape change on the lubrication performance is small. Therefore, for example, as shown in FIGS. 9 and 10, by reducing the weight of the journal 100 by reducing the width (journal width) in the axis L direction on the anti-unbalance mass side of the journal 100, the internal combustion engine is driven. It is possible to reduce the loss and improve the operation efficiency.
[0007]
If the lubricating passage 108 is opened at a portion where the journal width on the anti-unbalance mass side is narrow (narrow portion 104), there is a possibility that the lubricating oil cannot be sufficiently distributed throughout the other portion (wide portion 106). is there. This is not preferable because the oil film thickness or the oil film pressure is insufficient at the position P1 ′ where the oil film on the surface of the journal 100 is the thinnest and the pressure is the highest. Therefore, when the narrow portion 104 is formed, the portion where the opening of the lubricating passage 108 can be formed is limited to the wide portion 106.
[0008]
Here, focusing only on the point that the drive loss is reduced by weight reduction, the larger the formation range of the narrow portion 104, the better. However, in this case, since the formation range of the wide portion 106 becomes small, the formation position of the opening naturally approaches the position P1 ′, and the oil film pressure in the opening becomes high and the lubrication performance is likely to be lowered. On the other hand, from the viewpoint of maintaining the lubrication performance, if the formation range of the wide portion 106 is widened and opened at a position where the oil film pressure is lower, the formation range of the narrow portion 104 is reduced accordingly, and the weight is reduced. Reduction effect decreases.
[0009]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a balance shaft capable of achieving both a reduction in weight and maintenance of lubricating performance.
[0010]
[Means for Solving the Problems]
In the following, means for achieving the above object and its effects are described.
First, the invention according to claim 1 includes a journal that is rotatably supported by a bearing and has a narrow portion where the journal width of at least a part of the anti-unbalance mass side portion is narrower than that of the unbalance mass side portion. In the balance shaft in which a lubricating passage for supplying lubricating oil is formed between the journal and the bearing, the opening of the lubricating passage is provided between the journal and the bearing. It is provided at a position on the front side in the axial rotation direction from the position where the oil film pressure is highest, and a groove extending from the opening toward the front side in the axial rotation direction from the opening is formed on the outer peripheral surface of the journal. The gist.
[0011]
According to the above configuration, in order to form the narrow portion over a wide range in the circumferential direction of the journal, the lubrication passage has to be opened at a position where the oil film pressure is relatively high, and therefore a sufficient amount of lubrication can be obtained from the opening. Even when oil cannot be supplied, this is compensated by the supply of lubricating oil from a groove at a position where the oil film pressure is lower than the opening. Accordingly, it is possible to supply a sufficient amount of lubricating oil between the journal and the bearing, and it is possible to achieve a suitable balance between reduction in driving loss of the internal combustion engine and maintenance of the lubricating performance.
[0012]
In addition, the supply of the lubricating oil from the lubricating passage is performed such that the opening of the lubricating passage is formed at a portion where the oil film pressure is lower than the discharge pressure of the lubricating oil discharged from the opening, as in the configuration of claim 2. Is desirable.
[0013]
The gist of the invention according to claim 3 is that, in the balance shaft according to claim 1, the opening of the lubrication passage is formed at a boundary portion between the narrow portion and another portion.
[0014]
According to the above configuration, it is possible to supply the lubricant without unevenness between the journal and the bearing while avoiding as much as possible that the lubricant is hardly supplied from the opening due to the high oil film pressure.
[0015]
Here, if the distance between the edge portion of the groove and each edge portion of the narrow portion is set too short, sufficient sealing performance cannot be obtained, and the lubricant discharged from the opening is removed from the journal and the bearing. There is a risk of leaking excessively from between.
[0016]
On the other hand, according to the configuration of the fourth aspect, by setting the width of the groove located in the narrower portion as the narrower portion, the leakage of the lubricating oil can be suppressed. become.
[0017]
For example, as in the configuration of claim 5, when the width of the narrow portion is set to be narrower as the portion located on the side away from the unbalance mass side portion, the groove is also set correspondingly. In other words, it is desirable that the width of the portion located on the front side in the shaft rotation direction is set to be narrower.
[0018]
In order to suitably suppress such excessive leakage of the lubricating oil, as in the configuration according to claim 6, as in the configuration according to claim 6, both edge portions of the groove edge and the narrow portion. It is desirable to form the groove so that the shortest distance to the is constant.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a balance shaft of an internal combustion engine will be described.
[0020]
The balance shaft 1 shown in FIG. 1 shifts the center of gravity of the balance shaft 1 from the axis L on the journals 6a and 6b that are rotatably supported by the bearings 2a and 2b with respect to the support portions 3a and 3b of the internal combustion engine. And an unbalance mass 5 which is a weight for the purpose. The balance shaft 1 is rotated by transmission of rotation from the output shaft of the internal combustion engine. When the piston reciprocates during engine operation and the balance shaft 1 rotates, the inertia force of the piston is canceled based on the rotation, and the generation of vibration caused by the inertia force is suppressed.
[0021]
The axial length (journal width) of a part of the anti-unbalance mass side 8 located on the outer circumferential surface of one journal 6b of the balance shaft 1 and opposite to the unbalance mass side 7 is the unbalance mass side. 7 shorter than the journal width. As a result, the anti-unbalance mass side 8 becomes light, so that the center of gravity of the balance shaft 1 can be shifted from the axis L by a desired amount without making the unbalance mass 5 too heavy. Therefore, as compared with the case where the journal width on the anti-unbalance mass side 8 is not shortened as described above, the entire balance shaft 1 can be reduced in weight by making the unbalance mass 5 unnecessary. . In addition, the part (narrow part 9) with the short journal width in the anti-unbalance mass side 8 is formed so that the part located in the side away from the unbalance mass side 7 may become short.
[0022]
Inside the balance shaft 1, a lubricating passage 11 that receives supply of lubricating oil from the oil passage 10 of the support portion 3 a is provided so as to extend in the axial direction. In the lubrication passage 11, a portion located inside the journal 6a extends toward the outer peripheral surface of the journal 6a and communicates with an annular groove 12 formed on the outer peripheral surface. Then, lubricating oil is supplied to the portion from the oil passage 10 through the annular groove 12. A part of the lubricating oil supplied from the oil passage 10 to the annular groove 12 enters between the outer peripheral surface of the journal 6a and the inner peripheral surface of the bearing 2a. As a result, an oil film is formed between the outer peripheral surface of the journal 6a and the inner peripheral surface of the bearing 2a, and lubrication therebetween is performed.
[0023]
A portion of the lubrication passage 11 located inside the journal 6b extends toward the outer peripheral surface of the journal 6b and opens on the outer peripheral surface. The lubricating oil flowing in the lubricating passage 11 is discharged from the opening 13 of the lubricating passage 11 between the outer peripheral surface of the journal 6b and the inner peripheral surface of the bearing 2b. As a result, an oil film is formed between the outer peripheral surface of the journal 6b and the inner peripheral surface of the bearing 2b, and lubrication therebetween is performed. Then, the lubricating oil after being used for lubrication between the outer peripheral surface of the journal 6b and the inner peripheral surface of the bearing 2b flows down from both edges in the axial direction of the journal 6b.
[0024]
FIG. 2 shows a cross-sectional structure of the balance shaft 1 of FIG. 1 viewed from the direction of the arrow AA.
In FIG. 2, the balance shaft 1 rotates in the direction of arrow B by the rotation transmission from the output shaft of the internal combustion engine. In FIG. 2, the gap between the journal 6b and the bearing 2b is exaggerated more than the actual gap so that the understanding is easy.
[0025]
As shown in FIG. 2, the center of gravity G of the balance shaft 1 is deviated from the axis L as described above. For this reason, the balance shaft 1 rotates along the inner peripheral surface of the bearing 2b around the circle center M of the bearing 2b. And the oil film pressure in each position of the outer peripheral surface of the journal 6b when the balance shaft 1 rotates in this way becomes substantially the same distribution irrespective of the rotation phase.
[0026]
FIG. 3 shows the oil film pressure at each position on the outer peripheral surface of the journal 6b in the state shown in FIG.
As shown in FIG. 3, the thickness of the oil film in contact with the journal 6b is the smallest at a position P1 slightly retarded from the lower end of the outer peripheral surface of the journal 6b (backward in the rotational direction of the balance shaft 1 (axis)). The pressure will be the highest. The oil film pressure increases exponentially toward the position P1 at the position on the advance side (front side in the axial rotation direction) from the position P1, and at the position on the retard side (back side in the shaft rotation direction) from the position P1. As it moves away from P1, it decreases rapidly. Since the balance shaft 1 (FIG. 2) rotates with such a pressure distribution, the part where the opening 13 is formed is regulated as follows.
[0027]
That is, first, as described above, in the journal 6b, there is a possibility that the lubricating oil may not be sufficiently distributed to the entire portion other than the narrow portion 9 (wide portion 14). The opening 13 cannot be formed.
[0028]
Further, the lubricating oil discharged from the opening 13 flows in the direction opposite to the rotation direction of the balance shaft 1 on the outer peripheral surface of the journal 6b. For this reason, in order to supply a sufficient amount of lubricating oil to the position P1 (FIG. 2), it is necessary to form the opening 13 in the wide portion 14 at a position on the front side in the axial rotation direction from the position P1.
[0029]
Furthermore, since this part is a region where the oil film pressure increases as it approaches the position P1, if the opening 13 is formed in a part of the part where the oil film pressure is higher than the discharge pressure of the lubricating oil, the oil film pressure The discharge of the lubricating oil is hindered and the discharge becomes difficult. Therefore, in order to smoothly supply the lubricating oil, it is desirable to form the opening 13 at a portion where the discharge pressure of the lubricating oil is higher than the oil film pressure.
[0030]
Therefore, in the present embodiment, in consideration of such a situation, the discharge pressure and the oil film pressure are equal under the engine operation state where the discharge pressure is the lowest in front of the position P1 in the axial rotation direction. The opening 13 is formed at a position P2 on the front side in the axial rotation direction from the position. That is, the opening 13 is provided at the position P2 where at least the function of discharging the lubricating oil from the opening 13 can be ensured even when the discharge pressure becomes low during operation of the internal combustion engine.
[0031]
Here, the previous FIG. 3 shows the distribution of the oil film pressure in the state where the opening 13 and the groove 15 described later are not provided. When the opening 13 and the groove 15 are provided on the outer peripheral surface of the journal 6b, the oil film pressure decreases. Therefore, if the setting of the opening 13 in the above-described manner is performed based on the above distribution, the discharge pressure of the lubricating oil is surely higher than the oil film pressure. And the discharge function is secured.
[0032]
And based on the arrangement position of the opening 13 set in this way, the formation range of the narrow portion 9 is set as follows in order to obtain the greatest effect on the weight reduction of the balance shaft 1 described above.
[0033]
That is, the narrow portion 9 is formed with the previous position P2 as a starting point in the axial rotation direction toward the front in the rotational direction. Thus, by setting the position P2 as a starting point, the formation range of the narrow portion 9 is set as wide as possible while ensuring the function of discharging the lubricating oil to the wide portion 14 side. Further, in the state where the center of gravity of the balance shaft 1 is located at the lowest position (the state shown in FIG. 2) on the rear side in the axial rotation direction from the position P1, the position described above is based on the vertical line N passing through the axis L. A position P3 that is symmetrical with respect to P2 is set at the boundary between the narrow portion 9 and the wide portion 14, that is, the end point. In this way, by setting the position P3 as the end point, in other words, by forming the narrow portion 9 at a point-symmetrical position with respect to the unbalance mass 5 with respect to the axis L, the narrow portion 9 is disposed. The position is set to a position where the weight balance between the unbalance mass side 7 and the anti-unbalance mass side 8 of the balance shaft 1 is not lost.
[0034]
By the way, the function of discharging the lubricating oil is secured by providing the opening 13 at the position P2. However, when the opening 13 is formed at the position P2, if the discharge pressure is reduced and the difference between the discharge pressure and the oil film pressure is reduced, the discharge amount of the lubricating oil is reduced and the required amount can be secured. There is a risk of disappearing. Therefore, in the present embodiment, the following grooves 15 are provided in order to compensate for the shortage of the discharge amount.
[0035]
Hereinafter, the specific shape of the groove 15 will be described with reference to FIGS.
4 shows a cross-sectional structure of the balance shaft 1 of FIG. 1 viewed from the direction of the arrow CC, and FIG. 5 shows a front structure of the balance shaft 1 of FIG. 4 viewed from the direction of the arrow D.
[0036]
As shown in FIGS. 4 and 5, a groove 15 extending from the opening 13 to the front side in the axial rotation direction is formed on the outer peripheral surface of the journal 6 b. The groove 15 is formed by, for example, a technique of pressing a tool against the outer peripheral surface of the journal 6b in which the opening 13 is previously formed to plastically deform the outer peripheral surface.
[0037]
The groove 15 opens the lubricating passage 11 even at a position on the front side in the axial rotation direction from the position where the opening 13 is formed, that is, at a position where a relatively large amount of lubricating oil can be supplied because the oil film pressure is low. As a result, the lubricating oil is discharged from the groove 15 in addition to the opening 13, so that the above shortage is compensated.
[0038]
In addition, it is necessary to ensure a certain amount of space between the both end edge portions and the edge portion of the groove 15 on the outer peripheral surface of the journal 6b. If the interval is too short, sufficient sealing performance cannot be obtained, so that the lubricating oil discharged from the opening 13 leaks excessively between the journal 6b and the bearing 2b, and lubrication between them can be performed appropriately. This is because it disappears.
[0039]
Therefore, the width of the groove 15 is set to be narrower as the portion is located on the side away from the unbalance mass side 7 so as to correspond to the shape of the narrow portion 9. Specifically, the groove 15 is formed such that the shortest distance between the edge of the groove 15 and both edges in the axial direction of the journal 6b is a predetermined length a or more. Note that the predetermined length a is set by obtaining a value capable of suppressing the amount of leakage of the lubricating oil below an allowable value by experiments or the like.
[0040]
In this embodiment, it is not always necessary to form the opening 13 at a position where the discharge pressure of the lubricating oil is higher than the oil film pressure. If the discharge pressure is higher than the oil film pressure at least in the middle of the groove 15, the lubricating oil bypasses through the groove 15, that is, the portion having a low flow resistance, and the journal 6 b and the bearing 2 b are removed from the lubricating passage 11. This is because the lubricating oil flows between the two. On the other hand, in the present embodiment, since the discharge pressure is higher than the oil film pressure in the opening 13, a sufficient discharge amount is secured.
[0041]
As described above, according to the present embodiment, the effects described below can be obtained.
(1) The opening 13 is formed at the position P2 on the front side in the axial direction of rotation with respect to the position P1 where the oil film pressure between the journal 6b and the bearing 2b is highest, and the narrow portion from the opening 13 toward the front side in the direction of axial rotation. A groove 15 extending to 9 is formed. For this reason, in order to form the narrow portion 9 over a wide range in the circumferential direction of the journal 6b, the opening 13 has to be opened at a position where the oil film pressure is relatively high. Even when oil cannot be supplied, this is compensated by the supply of lubricating oil from the groove 15 formed at a position where the oil film pressure is low. Therefore, a sufficient amount of lubricating oil can be supplied between the journal 6b and the bearing 2b, and it is possible to achieve a suitable balance between reducing the weight and maintaining the lubricating performance.
[0042]
(2) Since the opening 13 is formed at the position P2 where the oil film pressure between the journal 6b and the bearing 2b is lower than the discharge pressure of the lubricant, the function of discharging the lubricant from the lubricant passage 11 is secured. be able to.
[0043]
(3) Since the opening 13 is formed at the boundary between the narrow portion 9 and the wide portion 14, it is avoided as much as possible that the supply of lubricating oil from the opening 13 becomes difficult due to the high oil film pressure. On the other hand, the lubricating oil can be supplied without deviation between the journal 6b and the bearing 2b.
[0044]
(4) Since the width of the groove 15 located in the narrow width portion 9 is set to be narrower as the width of the narrow width portion 9 is narrower, sufficient sealing performance is ensured and lubrication discharged from the opening 13 is achieved. It becomes possible to accurately suppress the oil from leaking excessively between the journal 6b and the bearing 2b.
[0045]
The embodiment described above may be modified as follows.
-In the said embodiment, the shape of the groove | channel 15 is not restricted to the shape shown in FIG. As such a groove, for example, it is possible to form a groove 25 having a shape extending with a uniform width as shown in FIG. In short, if the shortest distance between both edge portions of the journal 6b and the edge portion of the groove is set to a predetermined length a or more, the shape of the groove is changed within a range that does not hinder the lubrication performance. Is possible. As shown in FIG. 7, a groove 35 extending in such a shape that the shortest distance between the edge and both ends of the journal 6b is kept constant at the predetermined length a is formed as such a groove. Also good. According to such a configuration, the width of the groove can be widened, and the discharge amount of the lubricating oil can be more suitably ensured.
[0046]
In the above embodiment, the present invention is applied to the balance shaft 1 having the narrow portion 9 in which the journal width is gradually shortened toward the anti-unbalance mass side 8. The present invention is also applicable to a balance shaft in which a narrow portion 41 and a wide portion 42 are formed in a step shape as shown in FIG. In this configuration, in order to set the shortest distance between the edge portion of the opening 13 and both edge portions of the journal 43 to a predetermined length a or more, the boundary between the narrow portion 41 and the wide portion 42 is set. It is necessary to set the position at the front side in the axial rotation direction from the position where the opening 13 is formed. However, even in this configuration, the formation range of the narrow portion 41 can be set wider by setting the formation position of the opening 13 to the rear side in the axial rotation direction than the configuration in which only the opening 13 is provided. Thus, it is possible to achieve a suitable balance between reduction in driving loss of the internal combustion engine and maintenance of the lubricating performance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a balance shaft and a support structure thereof according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the balance shaft of FIG. 1 as viewed from the direction of arrow AA.
FIG. 3 is a graph showing the oil film pressure at each position on the outer peripheral surface of the journal.
4 is a cross-sectional view of the balance shaft of FIG. 1 as viewed from the direction of arrow CC.
5 is a front view of the journal of FIG. 4 as viewed from the direction of arrow D. FIG.
FIG. 6 is a front view showing a modified example of the groove.
FIG. 7 is a front view showing a modified example of the groove.
FIG. 8 is a front view showing a modified example of the journal.
FIG. 9 is a side view of a balance shaft showing the shape of a conventional journal.
10 is a front view of the journal of FIG. 9 as viewed from the direction of arrow Z. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Balance shaft, 2a, 2b ... Bearing, 3a, 3b ... Support part, 5 ... Unbalance mass, 6a, 6b, 43 ... Journal, 7 ... Unbalance mass side, 8 ... Unbalance mass side, 9, 41 ... Narrow part, 10 ... oil passage, 11 ... lubricating passage, 12 ... annular groove, 13 ... opening, 14, 42 ... wide part, 15, 25, 35 ... groove.

Claims (6)

The journal is supported rotatably by a bearing, and has a journal having a narrow portion where the width of at least a part of the non-unbalance mass side portion is narrower than that of the unbalance mass side portion. In the balance shaft in which a lubricating passage for supplying lubricating oil is formed between the bearing and the bearing,
The opening of the lubrication passage is provided at a position on the front side in the axial rotation direction with respect to the position where the oil film pressure between the journal and the bearing is highest, and the outer peripheral surface of the journal is provided on the outer circumferential surface from the opening to the front side in the axial rotation direction. The balance shaft is characterized in that a groove extending toward the narrow portion is formed. The balance shaft according to claim 1, wherein the opening of the lubricating passage is formed at a portion where the oil film pressure is lower than the discharge pressure of the lubricating oil discharged from the opening. The balance shaft according to claim 1 or 2, wherein the opening of the lubrication passage is formed at a boundary portion between the narrow portion and another portion. The balance shaft according to any one of claims 1 to 3, wherein a width of the groove positioned in the same portion is set to be narrower as the width of the narrow portion is narrower. 5. The balance according to claim 4, wherein the width of the narrow portion is set to be narrower as a portion located on a side farther from the unbalance mass side portion, and the width of the groove is set correspondingly. 6. shaft. The balance shaft according to any one of claims 1 to 5, wherein the groove is formed so that a shortest distance between the edge portion and both edge portions of the narrow portion is constant.

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