Hydroformed balance shaft

Abstract

An engine balance shaft (20) for an internal combustion engine (24) is provided, the engine balance shaft having a reduced total mass and moment of inertia while having sufficient bending stiffness and sufficient unbalanced mass. The balance shaft (20) is formed by fixedly coupling a counterweight (56), a front bearing journal (68), a rear bearing journal (60), a tail piece (40), and a nose piece (44) to a hollow tube (52). The hollow tube (52) is hydroformed to expand the diameter of the tube and to fasten desired components to the tube.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 869,706, filed on July 2, 2019. Technical Field

[0003] The present invention relates to a balance shaft for an internal combustion engine. More particularly, the present invention relates to a balance shaft formed by assembling components with a hydroformed tube. Background Art

[0004] Internal combustion engines include a balance shaft to balance engine vibrations in order to improve the smooth running and noise of the engine. The balance shaft is usually designed with an offset center of mass that generates a centrifugal force when rotating about the balance shaft main axis. The generated centrifugal force is then directed and rotationally aligned with the engine crankshaft rotation, resulting in the cancellation or reduction of engine vibration forces. Typically, the balance shaft is manufactured by casting the balance shaft. Alternatively, the balance shaft can be forged from a steel bar.

[0005] An engine balancing shaft generally comprises an elongated shaft having an axis of rotation extending in the longitudinal direction of the balancing shaft. The balancing shaft is generally provided with a pair of bearing journals centered on the axis of rotation of the balancing shaft. Needle bearings and / or plane bearings are generally assembled with the bearing journals, allowing the balancing shaft to rotate freely once the balancing shaft is assembled in the internal combustion engine. The bearing journals support the balancing shaft and cope with the centrifugal loads on the balancing shaft.

[0006] When the balancing shaft is assembled in an internal combustion engine, the mass of the balancing shaft is distributed so that the center of mass is spaced from the axis of rotation and is positioned below the axis of rotation. In addition, the mass of the balancing shaft is usually selected and distributed so that there is enough mass at predetermined locations to achieve the unbalanced mass required for a particular application. Although it is desirable to have a low center of mass to achieve the best performance of the balancing shaft, the balancing shaft must have a high moment of inertia of the area so that the balancing shaft has a high bending stiffness.

[0007] However, conventional constructions of balancing shafts, including cast or forged components, typically strive to strike a balance between keeping the total mass low, positioning the required material to achieve the desired imbalance, and constructing the mass body to have a high moment of inertia of the section, so that the balancing shaft has a high bending stiffness. In some constructions, structures must be added along or above the axis of rotation to achieve the bending stiffness required to manage shaft deflection. Additional structures result in additional mass, which does not contribute to the unbalanced mass, typically reduces the imbalance, and requires further mass to be added below the axis of rotation to balance the added structure and achieve sufficient unbalanced mass for a specific application. The additional undesirable mass added to the balancing shaft is further undesirable because it is directly contrary to efforts to reduce component weight to improve engine efficiency when the engine is used in a vehicle. In addition, the increase in the total mass of the balancing shaft increases the moment of inertia of the shaft, thereby reducing the responsiveness and performance of the balancing shaft in the internal combustion engine.

[0008] Therefore, it is desirable to provide a lightweight engine balance shaft with low mass. In addition, it is desirable to provide a balance shaft with a high moment of inertia of area so that the balance shaft has high bending stiffness. It is also desirable to reduce the mass of the balance shaft without sacrificing bending stiffness. In addition, it is desirable to provide a balance shaft with sufficient bending stiffness without the need to position mass at and / or above the axis of rotation. In addition, it is desirable that the balance shaft has a low moment of inertia. Finally, it is desirable to easily customize the balance shaft design for many engine applications while allowing certain components to be reused during manufacturing. Summary of the invention

[0009] An engine balance shaft for an internal combustion engine is provided, having a reduced overall mass while having sufficient bending stiffness and unbalanced mass. The balance shaft is formed by fixedly coupling a counterweight, a front bearing journal, a rear bearing journal, a tail piece, and a nose piece to a hollow tube. The hollow tube is hydroformed to expand the diameter of the tube and to fasten the desired components to the tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Advantages of the present invention will become apparent and better understood by referring to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a perspective view of an engine balance shaft with an external counterweight according to a first embodiment of the present invention;

[0012] Figure 2 In the internal combustion engine Figure 1 A three-dimensional view of the engine balance shaft;

[0013] Figure 3 yes Figure 1 A side view of the balance shaft;

[0014] Figure 4 yes Figure 3 A cross-sectional view of a balance shaft;

[0015] FIG5 is a side view of a known conventional engine balance shaft;

[0016] Fig. 6A yes Figure 3 An enlarged view of a portion 6A of a balancing shaft showing the total mass Tm and the unbalanced mass of the balancing shaft;

[0017] 6B is an enlarged view of a portion 6B of the known balancing shaft of FIG. 5 , showing a total mass Tm′ and an unbalanced mass Tu′ of the known balancing shaft;

[0018] Figure 7 It is before the hydroforming process and forming process Figure 1 Exploded view of the balance shaft;

[0019] Figure 8 yes Figure 7 The tube is deformed by the hydroforming process and the forming process before Figure 7 The counterweight frame is assembled together to form a perspective view of the tube and counterweight frame assembly;

[0020] Fig. 9 After the tube is deformed by the hydroforming process and the forming process Figure 8 A perspective view of the tube and counterweight frame assembly;

[0021] Fig.10 yes Fig. 9 The deformation of the tube and counterweight assembly Figure 7 A stereoscopic view of the nose assembly;

[0022] Fig.11 yes Figure 1 A perspective view of a balance shaft of , showing the welding process for fixedly coupling the nose piece to the tube;

[0023] Fig. 12A The tube is shown along the surface before being deformed by the hydroforming process and the forming process. Figure 8 A cross-sectional view of the tube taken along section line 12A-12A;

[0024] Fig. 12B shows the tube after it has been deformed by the hydroforming process and the forming process Fig. 9 A cross-sectional view of one embodiment of a portion of a tube taken along section line 12B-12B;

[0025] Fig.13 is a perspective view of an engine balance shaft with an internal counterweight according to a second embodiment of the present invention;

[0026] Fig.14 yes Fig.13 A side view of the balance shaft;

[0027] Fig.15 It is before the hydroforming process and forming process Fig.14 an exploded view of a balance shaft of the embodiment of the present invention and showing the tube, internal counterweight, front bearing journal, rear bearing journal, nose piece and tail piece;

[0028] Fig.16 It is before the tube is deformed by the hydroforming process and the forming process Fig.15 The tube and Fig.15 A perspective view of the internal counterweight, rear bearing journal and front bearing journal assembly;

[0029] Fig.17 After the tube is deformed by the hydroforming process and forming process Fig.16 A perspective view of the assembled tube, internal counterweight, front bearing journal, and rear bearing journal;

[0030] Fig.18A The tube is shown along the surface before being deformed by the hydroforming process and the forming process. Fig.15 A cross-sectional view of the tube taken along section line 18A-18A;

[0031] Fig.18B shows the tube after it has been deformed by the hydroforming process and the forming process Fig.17 A cross-sectional view of the tube taken along section line 18B-18B;

[0032] Fig. 18C The tube is shown along the surface before being deformed by the hydroforming process and the forming process. Fig.15 A cross-sectional view of the tube taken along section line 18C-18C;

[0033] Fig.18D shows the tube after it has been deformed by the hydroforming process and the forming process Fig.17 A cross-sectional view of the tube taken along section line 18D-18D;

[0034] Fig.19 yes Fig.17 A perspective view of the tube, internal counterweight, front bearing journal and rear bearing journal assembled with the nose and tail components;

[0035] Fig. 20 yes Fig.13 A perspective view of a balance shaft of , showing the welding process of fixedly coupling the nose and tail pieces to the tube;

[0036] Fig.21is a perspective view of a third embodiment of an engine balance shaft having an internal counterweight, showing the contoured shape that locks the internal counterweight in place within the tube; and

[0037] Fig. 22 is a cross-sectional view of a fourth embodiment of an engine balance shaft, showing Figure 4 Internal counterweights for balance shaft assembly. DETAILED DESCRIPTION

[0038] Referring to the drawings, like numerals designate identical or corresponding parts throughout the several views.

[0039] exist Figure 1 An engine balance shaft 20 is shown in FIG. 1 , illustrating an embodiment of a balance shaft 20 formed using a hydroforming process. An internal combustion engine 24 typically includes one or more balance shafts 20, such as Figure 2 As shown. The novel balance shaft 20 rotates about the rotation axis 28 to balance the vibration of the engine 24. Figure 2 As shown, each end 32, 32' of the novel balance shaft 20 is typically connected to a gear 36 or a sprocket 36A. The selection and configuration of the gear 36 and / or sprocket 36A fixedly connected to the novel balance shaft 20 is based on the requirements of the specific engine 24. The first end 32 and the second end 32' of the novel balance shaft 20 are respectively configured with a tail piece 40 and a nose piece 44. The tail piece 40 and the nose piece 44 are customized to be fixedly coupled with one or more drive features such as the gear 36, the sprocket 36A, etc., and are fixedly coupled according to the requirements of the specific engine 24 application. Typically, the one or more drive features are assembled with the nose piece 44 during the manufacture of the engine 24.

[0040] By using Figure 1 The novel assembly configuration of the balancing shaft 20 can remove non-useful mass along the rotation axis 28 , thereby resulting in a more optimized cross section of the balancing shaft 20 .

[0041] Figure 3 and Figure 4 A side view and a cross-sectional view of a first embodiment of a novel balancing shaft 20 are shown respectively. Figure 3 , the novel balance shaft 20 includes a hollow tube 52, a counterweight frame 56, and a nose piece 44, the hollow tube 52 having been hydroformed. The hydroforming process provides unique advantages by being able to form / shape the hollow tube 52 in a manner that is not possible with standard casting, forging, and press-fit construction methods. Forging or casting the counterweight frame 56 can concentrate mass in a location that is most conducive to minimizing overall mass and maximizing imbalance.

[0042] Figure 1The first embodiment shown illustrates a counterweight frame 56 added to the novel balance shaft 20. The tail piece 40, the rear bearing journal 60, and the front bearing journal 68 are integrated into the counterweight frame 56. The hollow tube 52 preferably comprises a seamless hollow tube 52 of a metal material having a yield strength lower than the yield strength of the counterweight frame 56. In one embodiment, the hollow tube 52 is a seamless steel tube. The tail piece 40 and the nose piece 44 are formed of steel, ductile iron, or the like.

[0043] Go to Figure 4 The counterweight frame 56 is a one-piece forged frame or cast frame including steel, ductile iron, etc. The counterweight frame 56 includes a main frame body 56A extending between opposite rearward ends 56B and forward ends 56C. Figure 7 As shown, each of the rear bearing journal 60 and the front bearing journal 68 has a cylindrical body 60, 68, wherein the rear channel 160A and the front channel 160B extend through the corresponding rear bearing journal 60 and the front bearing journal 68. Each of the rear bearing journal 60 and the front bearing journal 68 has a rear longitudinal axis 26A and a front longitudinal axis 26B extending through the corresponding rear channel 160A and the front channel 160B. The rear longitudinal axis 26A of the rear bearing journal 60 is aligned with the front longitudinal axis 26B of the front bearing journal 68. Each of the rear bearing journal 60 and the front bearing journal 68 is fixedly coupled to the main frame body 56A so that the rear longitudinal axis 26A and the front longitudinal axis 26B of each of the rear bearing journal 60 and the front bearing journal 68 are aligned to define the rotation axis 28 of the novel balance shaft 20. Rear passage 160A and front passage 160B through rear bearing journal 60 and front bearing journal 68 are aligned and configured to receive hollow tube 52. Rotational axis 28 of balance shaft 20 is defined by rear longitudinal axis 26A of rear bearing journal 60 and front longitudinal axis 26B of front bearing journal 68.

[0044] Likewise Figure 4 As shown, the support ring 82 is positioned adjacent the forward end 56C of the counterweight frame 56. Figure 7 , the support ring 82 has a cylindrical shape and a ring mounting surface 82B, wherein the ring channel 160C extends longitudinally through the support ring 82, and the mounting surface 82B is configured to engage the nose piece 44 in a mating manner. The ring longitudinal axis 26C extends through the ring channel 160C of the support ring 82. Similar to the front bearing journal 68 and the rear bearing journal 60, the support ring 82 is aligned on the counterweight frame 56 so that the rotation axis 28 passes through the ring longitudinal axis 26C of the support ring 82.

[0045] In addition, the rear passage 160A defined by the inner surface 60A of the rear bearing journal 60 and the end wall 84 extending across the rear passage 160A form a recess 162 to receive the rear end 88 of the hollow tube 52, such as Figure 4After the hollow tube 52 is inserted into the rear bearing journal 60, the front bearing journal 68 and the support ring 82 of the counterweight frame 56, the front end 92 of the hollow tube 52 is generally positioned flush with the ring mounting surface 82B of the support ring 82. However, based on the requirements of the specific engine 24 application, the front end 92 of the hollow tube 52 can be recessed or extended beyond the ring mounting surface 82B of the support ring 82.

[0046] The total mass Tm of the novel balancing shaft 20 includes two component masses, which are further defined as a balancing mass Tb and an unbalanced mass Tu. The total mass Tm is the simple sum of its component parts Tb and Tu. The balancing mass Tb is considered balanced with respect to the axis of rotation 28 of the novel balancing shaft 20. The center of mass Cb of the balancing mass Tb is located on the axis of rotation 28. In contrast, the unbalanced center of mass Cu of the unbalanced mass Tu is offset from the axis of rotation 28 by a radial distance Ru. Figure 3 and Fig. 6A The positions of the unbalanced mass center Cu, the balanced mass center Cb and the total mass center Cm, as well as the relative sizes of the unbalanced mass Tu, the balanced mass Tb and the total mass Tm are schematically illustrated. The diagram shows the relative values ​​of the parameters Cu, Cb, Cm, Tu, Tb, Ru, rather than the actual values.

[0047] Back to Figure 3 , the novel balancing shaft 20 has a total mass Tm and a center of mass Cm. The total mass Tm is actually the weight of the novel balancing shaft 20. Recall that the novel balancing shaft 20 has an unbalanced mass Tu, which is located at a radial distance Ru from the axis of rotation 28. During operation of the novel balancing shaft 20 rotating about its axis of rotation 28, the above-mentioned unbalanced mass Tu causes the rotating shaft 20 to appear unbalanced, resulting in a radial force from the balancing shaft 20 through the rear support journal 60 and the front support journal 68 and then transmitted to the engine 24 structure. Depending on the counterweight configuration, the radial force may also be an overturning moment. Those skilled in the art manipulate this force or moment transmitted to the engine 24 to counteract and thereby reduce or eliminate the engine 24 vibration caused by operation. The required values ​​of the unbalanced mass Tu, the unbalanced center of mass Cu, and the radial distance Ru are formulated for each specific engine 24 application, wherein different engine 24 configurations and displacements require optimal values ​​of Tu, Cu, and Ru to ensure smooth and vibration-free operation. The desired unbalanced mass Tu of the novel balance shaft 20 is selected based on operating conditions within the engine 24. As previously described, desired responsiveness and engine efficiency may be achieved by minimizing the moment of inertia I and total mass Tm of the novel balance shaft 20 to as low a value as practical.

[0048] Total mass Tm, balancing mass Tb, unbalanced mass Tu and radial distance Ru of unbalanced mass center Cu from rotation axis 28 affect moment of inertia I of novel balancing shaft 20. Adjustment mass Tm, balancing mass Tb and unbalanced mass Tm directly affect moment of inertia I of novel balancing shaft 20.

[0049] It is noteworthy that the novel balance shaft 20 relies on a hollow tube 52 having an air gap 108 along the rotation axis 28, such as Figure 4 As shown. Including air voids 108 within hollow tube 52 reduces the mass at and above the rotational axis 28 of the novel balance shaft 20. The novel balance shaft 20 includes a contoured portion 112 within hollow tube 52 to impart bending stiffness, rather than relying on mass located near the rotational axis 28 to impart bending stiffness, as shown. Figure 1 and Figure 4 As shown. Figure 1 , the profile portion 112 includes an arcuate upper profile surface 112A extending between the rear support journal 60 and the front support journal 68. In addition, the arcuate upper profile surface 112A may include one or more grooves 112B, ridges 112C, etc. selected to impart bending stiffness to the hollow tube 52. The upper profile surface 112A of the profile portion 112 is also selected in part to provide clearance for mating parts in the engine 24, if desired. Finally, repositioning the upper profile surface 112 of the hollow tube 52 near and / or below the axis of rotation 28 further facilitates the formation of the unbalanced mass Tu and the location of the unbalanced center of mass Cu.

[0050] Therefore, if Figure 1 As shown, the formation of the profile portion 112 increases the bending stiffness of the hollow tube 52, so that less mass is required along the rotation axis 28 to prevent the novel balance shaft 20 from bending. In addition, the formation of the profile portion 112 removes some of the mass of the hollow tube 52 below the rotation axis 28, so that the unbalanced mass Tu is increased. The formation of the profile portion 112 can also affect the unbalanced radius Ru. Adjusting the profile portion 112 can adjust the unbalanced mass Tu and the unbalanced radius Ru within a certain range, potentially allowing the characteristics of the novel balance shaft 20 to be fine-tuned for different engine 24 applications. If only a small change in the unbalanced mass Tu and the radius Ru of the unbalanced center of mass Cu is required, the change can be achieved by adjusting the upper profile surface 112A of the profile portion 112 so that more or less mass is moved below the rotation axis 28. Therefore, a small change in the profile portion 112 can actively affect the amount of unbalanced mass Tu and the radial distance Ru of the unbalanced center of mass Cu for fine-tuning the novel balance shaft 20 used in multiple engine 24 applications.

[0051] By comparing Figure 5 and Figure 3, illustrating the advantages of the novel balancing shaft 20 over the conventional balancing shaft structure 20 '. FIG. 5 shows an exemplary conventional balancing shaft 20 ', which has a general shape and volume similar to Figure 3 . In contrast to the novel balance shaft 20, the conventional balance shaft 20' has a counterweight frame 56' with integrated front and rear bearing journals 68' and 60', a tail piece 40', a nose piece 44', and an upper frame portion 52'. The rear bearing journal 60' and the front bearing journal 68' are aligned to define the axis of rotation 28' when the conventional balance shaft 20' is included in the engine 24. In addition, the tail piece 40' and the nose piece 44' are configured to interface with the gear 36 and / or the sprocket 36A.

[0052] As shown in FIGS. 5 and 6B , the conventional balancing shaft 20 ′ has a total mass Tm′, a balancing mass Tb′, and an unbalanced mass Tu′, the total mass Tm′ having a center of mass Cm′ spaced a distance Rm′ from the rotation axis 28′, the balancing mass Tb′ having a center of mass Cb′ aligned with the rotation axis 28′, and the unbalanced mass Tu′ having a center of mass Cu′ spaced a distance Ru′ from the rotation axis 28′. Since the hollow tube 52 of the novel balancing shaft 20 has been replaced with a cast / forged metal, as represented by element 52′ of FIG. 5 , the total mass Tm′ of the conventional balancing shaft 20′ is greater than the total mass Tm of the novel balancing shaft 20. Depending on the distribution of the air gap 108 around the rotation axis 28, the balancing mass Tb′ may increase or decrease relative to the balancing mass Tb of the novel balancing shaft 20. The change in balancing mass Tb′ may shift the position of the center of mass Cm′ within the conventional balancing shaft 20′ compared to the balancing mass Tb of the novel balancing shaft 20. Likewise, the unbalanced mass Tu′ may be increased or decreased relative to the unbalanced mass Tu of the novel balancing shaft 20 based in part on the geometry of the conventional balancing shaft 20 ′ and the change in balancing mass Tb′.

[0053] In essence, the conventional balance shaft 20' of FIG. 5 relies on cast / forged metal to ensure sufficient moment of inertia of area along the axis of rotation 28' to resist bending. FIGS. 5 and 6B illustrate representative locations of the unbalanced center of mass Cu' and center of mass Cm', as well as representative sizes of the total mass Tm', balancing mass Tb', and unbalanced mass Tu', for a conventional balance shaft 20' having the same approximate volume as the novel balance shaft 20. Adjusting the total mass Tm', balancing mass TV, unbalanced mass Tu', and the radial distance Ru' of the unbalanced center of mass Cu' from the axis of rotation 28' affects the moment of inertia I of the conventional balance shaft 20'. These illustrations do not represent the actual values ​​of these parameters Cu', Cm', Tu, Tm', Tb', and Ru'.

[0054] The conventional balance shaft 20' of FIG5 is more difficult to fine-tune for multiple engine 24 applications than the novel balance shaft 20. For example, while mass may be removed from the conventional balance shaft 20' to reduce the unbalanced mass Tu' and potentially adjust the radius Ru' of the unbalanced center of mass Cu', removing mass at and / or above the axis of rotation 28' directly affects the bending stiffness of the conventional balance shaft 20'.

[0055] Instead, by adjusting Figure 1 The profile portion 112 of the novel balancing shaft 20 can slightly change the radius Ru of the unbalanced mass center Cu, the balancing mass Tb, and the unbalanced mass Tu without affecting the total mass Tm of the novel balancing shaft 20. Therefore, since the total mass Tm is not affected by the change of the profile portion 112, the change of the profile portion 112 will more directly affect the balancing mass Tb, the unbalanced mass Tu, and the radius Ru of the unbalanced mass center Cu.

[0056] Furthermore, it is more difficult to adjust the unbalanced mass Tu' of the conventional balancing shaft 20' than to adjust the unbalanced mass Tu of the novel balancing shaft 20. Slight changes in the unbalanced mass Tu, the balancing mass Tb and the radius Ru of the unbalanced center of mass Cu can be achieved in the novel balancing shaft 20 simply by adjusting the shape of the profile portion 112. Repositioning the profile portion 112 relative to the rotation axis 28 has a direct effect on the unbalanced mass Tu and the radius Ru of the unbalanced center of mass Cu. Furthermore, as described with respect to Figure 13-Figure 22 As shown in the additional embodiment of the novel balance shaft 20, if desired, additional mass can be placed within the air gap 108 in the hollow tube 52 to adjust the unbalanced mass Tu and correspondingly adjust the radius Ru of the unbalanced center of mass Cu without modifying certain tools required during manufacturing.

[0057] Fig. 6A 6B illustrate a representative comparison of the center of mass Cm, Cm', total mass Tm, Tm', unbalanced center of mass Cu, Cu', unbalanced mass Tu, Tu', balanced mass Tb, Tb', and radial distances Ru, Ru' of the unbalanced center of mass Cu, Cu' of the novel balancing shaft 20 and the conventional balancing shaft 20', respectively. It is assumed that each of the novel balancing shaft 20 and the conventional balancing shaft 20' has the same overall shape and volume. However, because the novel balancing shaft 20 includes the air gap 108, the total mass Tm of the novel balancing shaft 20 is less than the total mass Tm' of the conventional balancing shaft 20'.

[0058] Go to Fig. 6A, the novel balancing shaft 20 is shown as having a center of mass Cm spaced a distance Rm from the axis of rotation 28. Although the center of mass Cm is not determined by the axis of rotation 28 of the novel balancing shaft 20, the distance Rm is shown for comparison purposes. In addition, the magnitude of the total mass Tm and the balancing mass Tb are represented by the lengths of arrows Tm and Tb, respectively. Similarly, the magnitude of the unbalanced mass Tu is represented by the length of arrow Tu, where the unbalanced center of mass Cu is spaced a radial distance Ru from the axis of rotation 28. Since the balancing mass Tb does not constitute a part of the unbalanced mass Tu, the length of arrow Tu is shown as being less than the length of arrow Tm. Similarly, the radial distance Ru of the unbalanced center of mass Cu may be a greater distance from the axis of rotation 28 than the radial distance Rm of the center of mass Cm. The unbalanced center of mass Cu is the center of mass of the unbalanced mass Tu, not the center of mass Cm of the novel balancing shaft 20.

[0059] Examining FIG6B , the center of mass Cm′ of the conventional balancing shaft 20′ is shown as being spaced apart from the axis of rotation 28′ by a distance Rm′. The magnitude of the total mass Tm′ of the conventional balancing shaft 20′ is represented by the length of the arrow Tm′. Fig. 6A Compared with the total mass Tm shown in FIG6B , the total mass Tm' is larger than the total mass Tm because the air gap 108 of the novel balance shaft 20 has been replaced by the solid metal in the conventional balance shaft 20'. In contrast, the distance Rm' of the center of mass Cm' of FIG6B is shown as Fig. 6A The radial distance Rm' of the center of mass Cm' of the conventional balancing shaft 20' may be less than the radial distance Rm of the center of mass Cm of the novel balancing shaft 20 for the same reason that the total mass Tu' of the conventional balancing shaft 20' is greater than the total mass Tu of the novel balancing shaft 20. Replacing the air gap 108 of the novel balancing shaft 20 with the cast / forged metal in the conventional balancing shaft 20' moves the relative position Rm' of the center of mass Cm' of the conventional balancing shaft 20'.

[0060] Compare Fig. 6A6B , although the magnitude of the total mass Tm' of the conventional balancing shaft 20' is greater than the magnitude of the total mass Tm of the novel balancing shaft 20, the unbalanced mass Tu' of the conventional balancing shaft 20' may be less than the unbalanced mass Tu of the novel balancing shaft 20. This difference in unbalanced masses Tu, Tu' is due to the fact that the novel balancing shaft 20 has an air gap 108, while the conventional balancing shaft 20' lacks the air gap 108. The actual difference in unbalanced masses Tu', Tu of the conventional balancing shaft 20' compared to the novel balancing shaft 20 depends in part on the actual geometry of the two balancing shafts 20, 20' and the volume and position of the air gap 108 of the novel balancing shaft 20. Therefore, the actual unbalanced mass Tu' may be equal to, greater than and / or less than the unbalanced mass Tu of the novel balancing shaft 20. It is also noted that the radial distance Ru' of the unbalanced center of mass Cu' of the conventional balancing shaft 20' is also affected by replacing the air gap 108 of the novel balancing shaft 20 with a cast / forged metal. For the same total volume within the balancing shafts 20 , 20 ′, the conventional balancing shaft 20 ′ has a greater total mass Tm′ than the novel balancing shaft 20 and a potentially smaller unbalanced mass Tu′ than the novel balancing shaft 20 .

[0061] exist Figure 7 In the illustrated embodiment, the tail piece 40 of the novel balance shaft 20 is integrally formed with the counterweight frame 56. In contrast, the nose piece 44 is formed as a separate piece 44 that is press-fitted into the hollow tube 52 after the hollow tube 52 is assembled with the counterweight frame 56. Both the tail piece 40 and the nose piece 44 are customized and designed for a specific engine 24 application and for being handled in a variety of manufacturing assembly and machining processes. One or both of the tail piece 40 and the nose piece 44 can be manufactured as separate pieces 40, 44 and assembled with the counterweight frame 56 and / or the hollow tube 52 using some known process. As previously described with respect to Figure 2 As disclosed, a gear 36 or sprocket 36A may be mounted to each end 32, 32' of the novel balance shaft 20. Thus, the tail piece 40 and nose piece 44 are generally configured to cooperatively engage with a selected gear 36 and / or sprocket 36A specifically for a particular engine 24 application. One advantage of embodiments having separate tail pieces 40 and / or nose pieces 44 is that by using different tail pieces 40 and nose pieces 44 with the same counterweight frame 56 and hollow tube 52, the novel balance shaft 20 may be customized for different engine 24 applications having different gear 36 / sprocket 36A attachment requirements.

[0062] refer to Figure 4, the novel balance shaft 20 optionally includes features for attachment to components such as gears 36 / sprockets 36A, and also optionally includes features configured for use during manufacturing. For example, the rearward end 56B of the tailpiece 40 includes a first cavity 120 aligned with the axis of rotation 28 of the novel balance shaft 20 and a second cavity 124 offset from the axis of rotation 28. The first cavity 120 includes a cylindrical wall 128 terminating at a conical end 132. The second cavity 124 also includes a cylindrical wall 136. However, the second cavity 124 terminates with a generally flat surface 140. Both the first cavity 120 and the second cavity 124 are typically used as positioning and / or clamping features during manufacturing. Therefore, the first cavity 120 and the second cavity 128 shown can vary in configuration, including omitting one or two of these cavities 120, 124. Alternatively, other positioning features and mounting features can be integrated into the tailpiece 40 for machining, operation of the assembly, and for mounting components such as gears 36.

[0063] Figure 7 Shown before assembly Figure 1 An exploded view of the novel balancing shaft 20. Reference Figure 7 , the novel balance shaft 20 includes a hollow tube 52, a nose piece 44, and a counterweight frame 56. The hollow tube 52 has a cylindrical sidewall 52A extending between the opposite rear end 88 and the front end 92 of the hollow tube 52. The cylindrical sidewall 52A has opposite inner surfaces 52B and outer surfaces 52C. Although the hollow tube 52 is shown as a cylindrical hollow tube 52, in some embodiments, as a non-limiting example, the hollow tube 52 can have other shapes such as a rectangular hollow tube 52. The hollow tube 52 includes a metal material having a yield strength lower than the yield strength of the counterweight frame 56. The tube channel 152 extends longitudinally through the hollow tube 52 between the opposite rear end 88 and the front end 92 of the hollow tube 52, forming a first end opening 88A and an opposite second end opening 92A. In addition, the hollow tube 52 has a tube longitudinal axis 28A defined between center points CPI, CP2 of the first end opening 88A and the second end opening 92A. Figure 4 As shown. Tube passage 152 forms air gap 108 within hollow tube 52. Hollow tube 52 has an outer diameter 156A, which is selected to cooperate with rear passage 160A and front passage 160B through rear bearing journal 60 and front bearing journal 68 and ring passage 160C through support ring 82. In addition, hollow tube 52 has an inner diameter 156B and a wall thickness 156C, as shown in FIG. Figure 4 The hollow tube 52 together with the profile portion 112 provide bending stiffness to the finished shaft 20 .

[0064] Back to Figure 7, the counterweight frame 56 is formed from steel, ductile iron, etc. by using a casting and / or forging process. The counterweight frame 56 may also include machined surfaces and features required by the specific engine 24 application. The counterweight frame 56 provides the main unbalanced mass Tu for the novel balance shaft 20. The counterweight frame 56 can vary in size, shape, volume, etc. to provide the desired unbalanced mass Tu and radius Ru of the unbalanced center of mass Cu for a specific application. However, the counterweight frame 56 will include at least the front support journal 68 and the rear support journal 60 and the support ring 82. Optionally, in some embodiments, the front support journal 68 and the rear support journal 60 and / or the support ring 82 can be formed as separate parts relative to the counterweight frame 56 and attached to the counterweight frame 56. In the case where the front support journal 68 and / or the rear support journal 60 are formed as separate parts, various assembly methods can be used to attach the front support journal 68 and / or the rear support journal 60 to the counterweight frame 56. Figure 7 In the illustrated embodiment, the front and rear bearing journals 68 , 60 and the support ring 82 are preferably formed integrally with the counterweight frame 56 .

[0065] As in Figure 4 , the counterweight frame 56 includes a cylindrical recess 162 formed by the inner surface 60A of the rear bearing journal 60 and the end wall 84. The recess 162 and the inner diameter 184 of the rear bearing journal 60 are sized and configured to matingly engage the rear end 88 of the hollow tube 52. In some embodiments, the recess 162 may include a locating feature for centering and / or positioning the rear end 88 of the hollow tube 52.

[0066] Likewise Figure 4 As shown, the counterweight frame 56 includes a lip 168 extending longitudinally away from the counterweight frame 56, forming an ear 168 configured to matingly engage and support the nose piece 44. Figure 7 The lip 168 is arcuate and has ends 168A, 168B that are generally aligned with the side edges 56D, 56E of the counterweight frame 56. The counterweight frame 56 has an arcuate inner surface 56F that extends between the side edges 56D, 56E and extends longitudinally between the end wall 84 of the recess 162 and the ring mounting surface 82B of the support ring 82. Figure 4 , the lip 168 has an upper lip surface 168C that is offset from the inner surface 56F of the counterweight frame 56. The radial space between the upper lip surface 168C of the lip 168 and the inner surface 56F of the counterweight frame 56 is configured to matingly engage and support a flange 180 that extends circumferentially around the nose piece 44.

[0067] refer to Figure 4, the inner surface 56F of the counterweight frame 56 is configured to cooperatively engage the outer surface 52C of the hollow tube 52. In addition, each of the rear bearing journal 60, the front bearing journal 68, and the support ring 82 has an inner diameter 184, which is configured to cooperatively match the outer diameter 156A of the hollow tube 52. The inner diameter 184 is selected to facilitate assembly with the hollow tube 52, that is, the inner diameter 184 is preferably selected to be slightly larger than the outer diameter 156A of the hollow tube 52.

[0068] Back to Figure 7 The nose piece 44 is preferably made of a metal material such as steel, ductile iron, etc. Figure 7 In the illustrated embodiment, the nose member 44 has a generally cylindrical body portion 192 that extends between the flange 180 and the front end 196 of the nose member 44. Since the nose member 44 is configured to cooperatively engage the gear 36 or sprocket 36A when assembled as part of the engine 24, the shape and size of the nose member 44 can vary greatly. Figure 3 , the main body portion 192 of the nose piece 44 optionally has a profile 192A that tapers at an angle 192B toward the axis of rotation 28. The angle 192B and profile 192A are selected based on the assembly requirements of the selected gear 36 or sprocket 36A. Figure 4 The internal features 204, 208 of the nose member 44 and the nose passage 212 are shown in FIG. Figure 4 In the illustrated embodiment, the nose piece 44 includes a recessed cylindrical hole 204 extending along the rotation axis 28 of the nose piece 44. The threaded hole 208 extends away from the recessed cylindrical hole 204 along the rotation axis 28. The nose passage 212 extends into the holes 204, 208. The recessed hole 204 and the threaded hole 208 are designed and configured to engage with the bolts inserted into the nose passage 212. Typically, the bolts are used to fixedly couple the gear 36 / sprocket 36A to the nose piece 44. The recessed hole 204 can also be used as a fastening position for machining and assembly processes. Similar to the outer surface 192A of the nose piece 44, the internal holes 204, 208 are designed and configured based on the desired engine 24 application. Therefore, the recessed internal holes 204, 208 can have different configurations, including omitting one or two holes 204, 208 according to the requirements of the specific embodiment.

[0069] Likewise Figure 4 As shown, the flange 180 of the nose piece 44 has a first mounting surface 180A, which is configured to cooperate with the ring mounting surface 82B of the support ring 82. A cylindrical first protrusion 220 protrudes perpendicularly away from the first mounting surface 180A of the nose piece 44, and the cylindrical first protrusion 220 is configured to cooperate with the tube passage 152 passing through the hollow tube 52. The first protrusion 220 terminates at an end surface 224, as shown in FIG. Figure 7 shown.

[0070] exist Figure 8-Figure 11 It is shown in Figure 1 A novel assembly method of a balance shaft 20. Reference Figure 8 , the hollow tube 52 is inserted into the counterweight frame 56 along the rotation axis 28 and through the rear passages 160A and 160B in the front support journal 68 and the rear support journal 60 and the ring passage 160C in the support ring 82 to form the subassembly 20-1. When the hollow tube 52 is fully inserted into the counterweight frame 56, the front end 92 is adjacent to the ring mounting surface 82B of the support ring 82. The outer diameter 156A (eg, Figure 7 ) is designed to be sized to facilitate insertion into the counterweight frame 56. In addition, Figure 7 In the illustrated embodiment, when the hollow tube 52 is initially inserted into the front bearing journal 68 and the rear bearing journal 60 , the hollow tube 52 has a cylindrical shape. Fig. 12A The hollow tube 52 is shown along Figure 8 The cross-sectional view taken along section line 12A-12A of FIG. 1 shows the shape of the hollow tube 52 before the side wall 52A is hydroformed and deformed. Figure 8 , when the hollow tube 52 is initially inserted into the front bearing journal 68 and the rear bearing journal 60, the longitudinal axis 28A of the hollow tube 52 is generally aligned with the rotation axis 28 through the front bearing journal 68 and the rear bearing journal 60. The subassembly 20-1 undergoes the following Fig. 9 The hydroforming process and forming process shown are performed to form the subassembly 20-2. In the hydroforming process H, a fluid is inserted along arrow H to pressurize the interior 108 of the hollow tube 52, causing the outer surface 52C to expand, as shown by arrow HI. The hydroforming process H forces the outer surface 52C of the hollow tube 52 to expand, so that the counterweight frame 56, the rear support journal 60, the front support journal 68 and the support ring 82 are fully seated with the hollow tube 52. The hydroforming process H eliminates the gap G between the hollow tube 52, the rear support journal 60, the front support journal 68 and the support ring 82, and locks the hollow tube 52 in the appropriate position on the counterweight frame 56. After the hydroforming process H and the forming process are completed, the fluid inserted into the hollow tube 52 is removed from the hollow tube 52.

[0071] Subassembly 20-1 undergoes a forming process F, by Fig. 9 As shown by arrows F, pressure F is applied to the hollow tube 52 to deform the outer surface 52C of the hollow tube 52 into a contoured portion 112 extending between the front support journal 68 and the rear support journal 60. The pressure F is applied to the hollow tube 52 using a die, a moving slide, etc. In one embodiment, the hollow tube 52 is pressurized during the hydroforming process H, wherein during the forming process F, a certain amount of pressure is maintained within the hollow tube 52 as the external deformation occurs.

[0072] Fig. 12B FIG. 5 shows an embodiment of the cross-sectional shape of the hollow tube 52 after the side wall 52A is hydroformed and deformed. Before the hydroforming process and the forming process, the hollow tube 52 has a cylindrical shape, such as Fig. 12A As shown. Fig. 9 During the hydroforming process H and the forming process F shown, the contoured portion 112 of the outer surface 52C of the hollow tube 52 is deformed into an upper contoured surface 112A having one or more grooves 112B and ridges 112C, as shown in FIG. Fig. 12B The contoured portion 112 of the hollow tube 52 has a non-cylindrical shape after being deformed by the hydroforming process H and the forming process F. The contoured portion 112 increases the bending stiffness of the hollow tube 52. Various contoured portions 112 may be selected for the hollow tube 52 based in part on the amount of bending stiffness desired for a particular engine 24 application.

[0073] Fig. 9 The illustrated hydroforming process H and forming process F may be performed simultaneously on the subassembly 20-1, or separately, depending on the desired manufacturing process flow. Furthermore, the hydroforming process H may be performed before or after the forming process F. Completion of both the hydroforming process H and the forming process F transforms the subassembly 20-1 into the subassembly 20-2. The labeling of the various subassemblies 20-1, 20-2, etc. is purely descriptive, reflecting the various manufacturing stages shown in the drawings.

[0074] Fig.10 The end 224 of the nose piece 44 is shown inserted into the tube passage 152 of the hollow tube 52, as indicated by arrow N. In some embodiments, the end 224 of the nose piece 44 is pressed into the hollow tube 52 to form the subassembly 20-3. Fig.13 , the subassembly 20-3 is selectively welded using a laser welding process or any other welding process, as shown by elements 232 and 232', to fixedly couple the nose piece 44 to the hollow tube 52 and / or the support ring 82. The nose piece 44 is welded to the hollow tube 52, the counterweight frame 56 and / or the support ring 82 using laser processes 232, 232', etc., to form Figure 1 and Fig.11 The novel balancing shaft 20 shown. Alternatively, the nose piece 44 can be press-fitted as an assembly method using mechanical interference. For example, the nose piece 44 can be fixedly coupled to the hollow tube 52 by an elastic interference fitting between the nose piece 44 and the tube passage 152 in the hollow tube 52.

[0075] exist Figure 13-Figure 20 A second embodiment of the novel balancing shaft 20A is shown in FIG. Although the first embodiment of the novel balancing shaft 20 includes an external counterweight frame 56, Fig.13The second embodiment 20A shown includes an internal weight 240. As in the first embodiment, the novel balance shaft 20A includes a hollow tube 52", which provides sufficient bending stiffness for the novel balance shaft 20A. The internal weight 240 is inserted into the hollow tube 52", as further described below. The bend B formed in the hollow tube 52" increases the bending stiffness of the novel balance shaft 20A.

[0076] refer to Fig.13 and Fig.14 The second embodiment of the novel balance shaft 20A includes the front bearing journal 68B and the rear bearing journal 60B, the tail piece 40A and the nose piece 44A. The front bearing journal 68B and the rear bearing journal 60B are aligned to define the rotation axis 28. The hollow tube 52" is formed so that the rear support journal 60B and the front support journal 68B are aligned with the rotation axis 28 and the internal counterweight 240 is spaced apart from the rotation axis 28. In the second embodiment of the novel balance shaft 20A, each specific functional area (nose component 44A, tail component 40A, rear support journal 60B, front support journal 68B, internal counterweight 240) is individually placed at a desired location on the hollow tube 52" along the length of the hollow tube 52". The hollow tube 52" is then pressurized from the inside of the tube channel 152' of the hollow tube 52" during the hydroforming process H to expand the diameter 156A' of the hollow tube 52" and lock the selected pieces 60B, 68B in the appropriate position. After the hydroforming process H has been completed, certain pieces, such as the tail component 40A and / or the nose component 44A, are assembled with the hollow tube 52".

[0077] Go to Fig.14 , a second embodiment of the novel balancing shaft 20A has a total mass Tm, wherein the magnitude of the total mass Tm is indicated by the relative length of arrow Tm. The total mass Tm includes the mass of the hollow tube 52", the rear support journal 60B, the front support journal 68B, the tail piece 40A and the nose piece 44A, and the internal counterweight 240. The total mass Tm has a center of mass Cm spaced apart from the axis of rotation 28 by a radial distance Rm. Although the center of mass Cm is determined by the weight distribution of the novel balancing shaft 20A regardless of the axis of rotation 28, for comparison purposes, the center of mass Cm is shown as being spaced apart from the axis of rotation 28 by a radius Rm. The novel balancing shaft 20A has a balancing mass Tb, which has a center of mass Cb on the axis of rotation 28, wherein the magnitude of the balancing mass Tb is indicated by the relative length of arrow Tb. The balancing mass Tb is a portion of the total mass Tm that is uniformly distributed around the axis of rotation 28.

[0078] Likewise Fig.14 As shown, the novel balancing shaft 20A has a remaining unbalanced mass Tu having an unbalanced center of mass Cu spaced apart radially from the axis of rotation 28 by a distance Ru. Figure 3 As described in the first embodiment of the novel balancing shaft 20 shown, the unbalanced mass Tu does not include the balancing mass Tb. Therefore, the magnitude of the unbalanced mass Tu is less than the magnitude of the total mass Tm of the novel balancing shaft 20A. The center of mass Cm of the novel balancing shaft 20A is represented as Cm spaced apart from the axis of rotation 28 by a radial distance Rm. The general position of the center of mass Cm is shown for comparison with the unbalanced center of mass Cu. The mass Tc of the internal counterweight 240 and the center of mass Cc of the internal counterweight 240 are also shown. The center of mass Cc of the internal counterweight 240 is shown spaced apart from the axis of rotation 28 by a radial distance Rc. The mass Ts of the novel balancing shaft 20A excluding the mass Tc of the internal counterweight 240 is represented as element Ts. Fig.14 The radial positions of the unbalanced mass center Cu, the mass center Cm of the novel balancing shaft 20A, the mass center Cc of the internal counterweight 240, and the sizes of the total mass Tm, the balancing mass Tb, the unbalanced mass Tu, the counterweight mass Tc and the balancing shaft mass Ts shown are shown in outline to represent relative values ​​and do not represent the actual values ​​of these parameters Cu, Cm, Cc, Cb, Tu, Tm, Ts, Tc, Tb, Ru.

[0079] Fig.14 The lengths of the arrows Tu, Tm, Tc, Ts, Tb shown represent the relative sizes of the unbalanced mass Tu, the total mass Tm, the balancing shaft mass Ts, the balancing mass Tb, and the counterweight mass Tc. For example, the counterweight mass Tc is added to the balancing shaft mass Ts to obtain the total mass Tm of the novel balancing shaft 20. It should be understood that adjusting the size and position of the mass Tc of the internal counterweight 240 directly affects the total mass Tm, the balancing mass Tb, and the unbalanced mass Tu of the novel balancing shaft 20A. In addition, adjusting the mass Tc of the internal counterweight 240 and the radial distance Rc of the center of mass Cc of the counterweight from the axis of rotation 28 directly affects the size and radial position Ru of the unbalanced mass Tu. It is worth noting that the relative positions of the centers of mass Cc, Cm, Cu, Cb in the longitudinal direction along the novel balancing shaft 20A do not represent the relative longitudinal positions of these centers of mass Cc, Cm, Cu, Cb. The centers of mass Cc, Cm, Cu, Cb are spaced apart in the longitudinal direction purely for illustrative purposes. In fact, the centers of mass Cc, Cm, Cu, Cb can potentially be aligned in the longitudinal direction depending on the location and configuration of the tail piece 40A, nose piece 44A, rear support journal 60B, front support journal 68B and internal counterweight 240 attached to the novel balance shaft 20A and the profile of the hollow tube 52".

[0080] refer to Fig.14In principle, the unbalanced mass Tu, the radial position Ru of the unbalanced mass center Cu, and other parameters such as the total mass Tm and the balancing mass Tb are usually selected to achieve the desired moment of inertia I for a specific engine 24 application. The value of the unbalanced mass Tu and the value of the radial distance Ru from the unbalanced mass center Cu can be adjusted within a certain range to achieve the target moment of inertia I. Therefore, increasing and / or decreasing the magnitude of one or both of the unbalanced mass Tu and the radial distance Ru will affect the actual moment of inertia I of the novel balancing shaft 20A.

[0081] Since the radial distance Ru between the unbalanced mass Tu and the unbalanced mass center Cu can be adjusted by changing the mass Tc of the internal counterweight 240, Fig.14 The second embodiment of the novel balance shaft 20A has significant advantages over the conventional cast / forged shaft 20' (such as shown in Figure 5). Therefore, if it is necessary to fine-tune the moment of inertia I of the novel balance shaft 20A, the mass Tc of the internal counterweight 240 can be increased and / or decreased within a certain range. Therefore, the novel balance shaft 20A can be adjusted only by changing the mass Tc of the internal counterweight 240 to be used in multiple engine 24 applications that require a certain range of moments of inertia I. For example, the unbalanced mass Tu can be selectively increased by increasing the mass Tc of the internal counterweight 240. In addition, increasing the mass Tc of the internal counterweight 240 can also increase the radial position Ru of the unbalanced center of mass Cu. Since increasing the mass Tc of the internal counterweight 240 can potentially increase the radial position Ru of the unbalanced center of mass Cu and the size of the unbalanced mass Tu, a small change in the mass Tc of the internal counterweight 240 can significantly affect the moment of inertia I of the novel balance shaft 20A. Likewise, reducing the mass Tc of the internal counterweight 240 can directly affect the radial position Ru of the unbalanced mass center Cu and the size of the unbalanced mass Tu.

[0082] Go to Fig.15 The novel balance shaft 20A includes a hollow tube 52", the hollow tube 52" having a cylindrical side wall 52A extending between opposite ends 88', 92' of the tube 52". A cylindrical tube passage 152' extends longitudinally through the hollow tube 52" between the opposite rear end 88' and front end 92'. The hollow tube 52" has an outer diameter 156A', an inner diameter 156B' and a wall thickness 156C'. Preferably, the hollow tube 52" comprises a seamless hollow tube 52" of a metal material having a yield strength lower than the yield strength of the metal material forming the front support journal 68B and the rear support journal 60B.

[0083] Fig.15Also shown in FIG. 4 are tail piece 40A, nose piece 44A, internal counterweight 240, rear support journal 60B, and front support journal 68B. Each of tail piece 40A, nose piece 44A, rear support journal 60B, front support journal 68B, and internal counterweight 240 is preferably formed of steel, ductile iron, or the like.

[0084] The internal weight 240 is preferably a rectangular rod having an outer surface 244 extending between opposite ends 248, 252, such as Fig.15 As shown. Alternatively, the internal weight 240 may be a cylindrical rod, or may include a contoured shape. Any shape of the internal weight 240 may be selected as long as the internal weight 240 is sized to fit within the tube passage 152' passing through the hollow tube 52".

[0085] like Fig.15 As shown, for some embodiments, the front support journal 68B and the rear support journal 60B can have the same size and shape. In other embodiments, the front support journal 68B can have a different size and / or a different shape than the rear support journal 60B. Each of the rear support journal 60B and the front support journal 68B is formed by a cylindrical outer wall 60C, 68C extending between the opposite ends 60D, 60E, 68D, 68E. The rear channel 160A' and the front channel 160B' extend through the corresponding rear support journal 60B and the front support journal 68B, and the corresponding rear support journal 60B and the front support journal 68B are configured to engage with the outer diameter 156A' of the hollow tube 52". Specifically, the inner diameter 160 of the rear channel 160A' and the front channel 160B' extending through the rear support journal 60B and the front support journal 68B is greater than the outer diameter 156A' of the hollow tube 52". In addition, each rear bearing journal 60B and front bearing journal 68B optionally includes a flange 260 extending circumferentially around the outer surface 60C, 68C adjacent each end 60D, 60E, 68D, 68E of the respective rear bearing journal 60B and front bearing journal 68B. The flange 260 forms a groove 264 on the outer surface 60C, 68C of each of the rear bearing journal 60B and front bearing journal 68B to support a needle bearing or a plain bearing as required by the specific application.

[0086] like Fig.14 and Fig.15As shown, the tail piece 40A includes a generally cylindrical main body portion 272 extending between the end 32 of the tail piece 40A and a second mounting surface 276. The second mounting surface 276 is generally perpendicular to the longitudinal axis of the tail piece 40A. The generally cylindrical main body portion 272 may include a tapered surface or may be a multi-faceted shape. The main body portion 272 is selectively configured to engage with a gear 36 / sprocket 36A within a specific engine 24. Therefore, the size and shape of the tail piece 40A can vary based on the requirements of the specific engine 24 application. Preferably, the main body portion 272 is designed and sized so that the outer diameter 280 of the main body portion 272 is equal to or greater than the inner diameter 156B' of the hollow tube 52". In addition, Fig.15 The illustrated embodiment includes a cylindrical second protrusion 284 extending away from the second mounting surface 276 of the tail piece 40A, wherein an end surface 288 of the second protrusion 284 defines an opposite end 288 of the tail piece 40A. The second protrusion 284 is designed and shaped to fit within the tube passage 152' of the hollow tube 52". More specifically, the outer diameter 290 of the second protrusion 284 is smaller than the inner diameter 156B' of the hollow tube 52", as shown in FIG. Fig.14 Furthermore, when the second protrusion 284 is inserted into the tube passage 152' of the hollow tube 52", the second mounting surface 276 will frictionally engage with the rear end portion 88 of the hollow tube 52".

[0087] like Fig.14 and Fig.15 As shown, the nose piece 44A has a generally cylindrical body portion 272' that extends between the end surface 304 and the second mounting surface 276'. The outer diameter 280' of the body portion 272' is equal to or greater than the inner diameter 156B' of the hollow tube 52", as shown in FIG. Fig.14 As shown. The second mounting surface 276' is configured to frictionally engage with the front end portion 92 of the hollow tube 52". The cylindrical second protrusion 284' extends vertically away from the second mounting surface 276' and terminates at an end surface 288'. The second protrusion 284' has an outer diameter 290' that is designed and dimensioned to fit within the tube passage 152' of the hollow tube 52". More specifically, the outer diameter 290' is smaller than the inner diameter 156B' of the hollow tube 52". In addition, the outer diameter 290' is smaller than the outer diameter 280' of the main body portion 272' of the nose member 44A. The attachment portion 192' extends away from the end surface 304 of the nose member 44A, and the attachment portion 192' is configured to cooperatively engage with the gear 36 / sprocket 36A as required for a specific engine 24 application. Fig.14 and Fig.15In the illustrated embodiment, the attachment portion 192' includes a tapered sidewall 192A' extending from the end surface 304 of the nose member 44A to the end 196'. The nose passage 212 extends from the end 196' of the nose member 44A toward the end surface 304 and is configured to receive a bolt or other hardware to fixedly couple the gear 36 / sprocket 36A to the nose member 44A. Fig.14 and Fig.15 In the illustrated embodiment, the attachment portion 192' and the nose passage 212 are configured to have a longitudinal axis 28 aligned with the rotational axis 28 when the novel balance shaft 20A is fully assembled. Fig.14 As shown, the second protrusion 284 of this embodiment has a longitudinal axis 308 that is offset from the longitudinal axis 28 of the nose passage 212 and the attachment portion 192'. However, the overall configuration, shape and size of the nose member 44A may be adjusted for other embodiments of the novel balancing shaft 20A intended for different applications. Fig.15 As shown, the nose piece 44A includes a second mounting surface 276' and a protrusion 288' so that the nose piece 44A can be assembled with the hollow tube 52".

[0088] exist Figure 16-Figure 20 The assembly method of the second embodiment of the novel balance shaft 20A is shown in FIG. Fig.16 , the internal counterweight 240 is inserted into the tube passage 152' extending longitudinally through the hollow tube 52". In addition, the hollow tube 52" is inserted through the rear passage 160A' and the front passage 160B' in the rear support journal 60B and the front support journal 68B. Alternatively, the front support journal 68B and the rear support journal 60B are slid along the hollow tube 52" to position the rear support journal 60B and the front support journal 68B at a predetermined position. The internal counterweight 240 and the rear support journal 60B, the front support journal 68B are assembled with the hollow tube 52" to form Fig.16 Axle subassembly 20-4 is shown.

[0089] Next, subcomponent 20-4 undergoes Fig.17 The hydraulic forming process H shown, in which one or both of the rear end portion 88' and the front end portion 92' of the hollow tube 52" are sealed, and fluid is inserted into the hollow tube 52", as shown by arrow H. The fluid pressure within the tube passage 152' of the hollow tube 52" applies pressure radially outward, as shown by arrow HI, expanding the outer surface of the side wall 52A' of the hollow tube 52". The hollow tube 52" expands during the hydraulic forming process H to securely seat the rear support journal 60B and the front support journal 68B on the hollow tube 52". After the hydraulic forming process H and the forming process F are completed, the fluid is removed from the tube passage 152' passing through the hollow tube 52".

[0090] Likewise Fig.17As shown, the hollow tube 52" undergoes a forming process F, wherein a force F is applied to the hollow tube 52" to bend the hollow tube 52" into a desired profile 316. Fig.17 In the illustrated embodiment, the forming process F repositions the center portion 320, the rear portion 324, and the front portion 328 spaced apart from the rotation axis 28. Preferably, the hollow tube 52" is formed by a mold or a moving slide when the hollow tube 52' is pressurized. Various embodiments with a range of overall profiles 316 are envisioned to support different engine 24 applications. Additionally, in some embodiments, the forming process F can lock the internal counterweight 240 in place within the hollow tube 52". In other embodiments, the internal counterweight 240 can be formed into a new shape within the hollow tube 52" during the forming process F.

[0091] Fig.17 The illustrated hydroforming process H and forming process F may be performed simultaneously on the subassembly 20-4, or individually, depending on the desired manufacturing process flow. In addition, the hydroforming process H may be performed before or after the forming process F. Completion of both the hydroforming process H and the forming process F transforms the subassembly 20-4 into the subassembly 20-5. The descriptions of the various subassemblies 20-4, 20-5, etc. are purely descriptive, reflecting the various manufacturing stages shown in the accompanying drawings. The exemplary manufacturing process includes the following steps: placing the subassembly 20-4 on the lower forming tool, closing the upper forming tool against the lower forming tool, pressurizing the hollow tube 52" (by inserting a fluid into the tube channel 152' of the hollow tube 52") to hydroform the hollow tube 52" so that the hollow tube 52" expands to seat the rear support journal 60B and the front support journal 68B. When the hollow tube 52" is pressurized, a force F is applied to the hollow tube 52" by a mold or a movable slide to form a contour shape 316. After the hydroforming process H and the forming process F are completed, the pressure is removed from the hollow tube 52" by removing the remaining fluid in the hollow tube 52".

[0092] Figures 18A-18D Some changes in the shape of the hollow tube 52" during the hydroforming process H and the forming process F are shown. Fig.18A Shown along Fig.15 The cross-sectional view of the hollow tube 52" taken along section line 18A-18A shows that the side wall 52A' of the hollow tube 52" is initially cylindrical. Fig.18B Shown along Fig.17 The cross-sectional view of the hollow tube 52" along the section line 18B-18B shows the bend B in the side wall 52A'. In addition, the portion 340 of the hollow tube 52" has been spaced apart from the rotation axis 28 during the forming process F, as shown in FIG. Fig.18B shown.

[0093] Fig. 18CShown along Fig.15 The cross-sectional view of the hollow tube 52" along the section line 18C-18C shows that before the hydraulic forming process H and the forming process F, the hollow tube 52" has a circular shape. Fig.18D It is shown that after the hydroforming process H and the forming process F, the hollow tube 52" is Fig.17 Specifically, the central portion 320 of the hollow tube 52" is deformed into a rounded rectangular cross-sectional shape. The bend B in the hollow tube 52" together with the change in the cross-section in the selected portion 320 of the hollow tube 52" increases the bending stiffness of the hollow tube 52". In addition, repositioning the portion 320 of the hollow tube 52" below the rotation axis 28 can adjust the amount of unbalanced mass Tu and the moment of inertia I of the balance shaft 20A.

[0094] After the hydroforming H process and the forming F process are completed, the subassembly 20-5 is assembled with the tail component 40A and the nose component 44A, as shown in FIG. Fig.19 As shown. The second protrusions 284, 284' of the tail member 40A and the nose member 44A are inserted into the opposite rear end portions 88' and front end portions 92' of the hollow tube 52" to form the subassembly 20-6. In one embodiment, the second protrusions 284, 284' are press-fitted into the tube passage 152' of the hollow tube 52" so that the second mounting surfaces 276, 276' are seated against the respective rear end portions 88' and front end portions 92' of the hollow tube 52".

[0095] Fig. 20 The final step in the assembly process of the novel balance shaft 20A is shown. The subassembly 20-6 selectively undergoes one or more welding processes to secure the tail member 40A and the nose member 44A to the hollow tube 52", forming the novel balance shaft 20A. One or more laser welds 232 are formed near the rear end 88' and the front end 92' of the hollow tube 52" to fixedly couple the tail member 40A and the nose member 44A to the hollow tube 52". Other methods of attaching the tail member 40A and the nose member 44A may be used, such as welding, adhesives, mechanical fasteners, etc. Alternatively, the tail member 40A and the nose member 44A may be press-fitted as in an assembly method using mechanical interference.

[0096] Fig.21 A third embodiment of a novel balancing shaft 20B is shown. The third embodiment is similar to Figure 13-Figure 20 The second embodiment shown is assembled using the same steps. However, the internal weight 240A of the shaft 20B is smaller than Fig.19The novel internal weight 240 of the balance shaft 20A is shown. In addition, ridges 112C' and / or grooves 112B' are formed around the outer circumference of the internal weight 240A to lock the internal weight 240A in place within the hollow tube 52".

[0097] Fig. 22 An embodiment of a novel balancing shaft 20C is shown. The novel balancing shaft 20C has Figure 1 The external counterweight frame 56 and Fig.13 The internal weight 240B in the embodiment shown. Fig. 22 In the embodiment of the present invention, the internal weight 240B is inserted into the air gap 108 of the hollow tube 52 before the hollow tube 52 is subjected to the hydroforming process H and the forming process F. The option of including the internal weight 240B in combination with the external weight frame 56 further increases the flexibility of the novel balance shaft 20-20C.

[0098] One benefit of the novel engine balance shaft is that the novel balance shaft has a reduced mass compared to a conventional cast / forged balance shaft. Additionally, a second benefit is that the novel balance shaft has a high cross-sectional moment of inertia, which enables the novel balance shaft to have a high bending stiffness. A third benefit is that the novel balance shaft has sufficient bending stiffness without the need to position mass at and / or above the axis of rotation. A fourth benefit is that the novel balance shaft has a lower moment of inertia than a conventional cast / forged balance shaft having a similar profile. A fifth benefit is that the novel balance shaft design can be easily customized for a variety of engine applications. Finally, a sixth benefit is that the novel balance shaft design allows certain components to be reused during the manufacture of embodiments for different engine applications.

[0099] The present invention has been described in an illustrative manner, and it should be understood that the terms used are intended to have the nature of descriptive text, rather than restrictive. In accordance with the above teachings, many modifications and variations of the present invention are possible. Therefore, it should be understood that within the scope of the appended claims, the present invention may be implemented differently from the specific description.

Claims

1. An engine balance shaft for an internal combustion engine, the balance shaft comprising: a hollow tube having a sidewall extending between a rear end and a front end of the hollow tube and a tube passage extending longitudinally through the hollow tube between the rear end and the front end of the hollow tube to form a first end opening and an opposing second end opening; a front bearing journal having a first cylindrical wall with a front passage extending between opposite ends of the first cylindrical wall, the front passage being configured such that at least a portion of the hollow tube passes through the front passage; a rear bearing journal having a second cylindrical wall, wherein a rear passage extends between opposite ends of the second cylindrical wall, the rear passage being configured such that at least the portion of the hollow tube passes through the rear passage; a counterweight frame, the counterweight frame being configured to be fixedly coupled to the hollow tube; The balance shaft includes a tail member fixedly coupled to the rear end portion of the hollow tube; When the tail piece is assembled with the hollow tube, the tail piece surrounds the first end opening of the hollow tube; and The counterweight frame is integrally formed with the tail member, the front bearing journal and the rear bearing journal; wherein after the hollow tube is assembled with the front and rear bearing journals by passing the portion of the hollow tube through the front and rear passages, and after the hollow tube is assembled with the counterweight frame, the hollow tube is enlarged by a hydroforming process to fixedly couple the front and rear bearing journals to the hollow tube; and wherein the counterweight frame is fixedly coupled to the side wall of the hollow tube when the hollow tube is expanded by the hydroforming process, the balancing shaft includes a nose component fixedly coupled to the front end portion of the hollow tube, and when the nose component is assembled with the hollow tube, the nose component surrounds the second end opening of the hollow tube.

2. The engine balance shaft according to claim 1, wherein: Each of the hollow tube, the front bearing journal, the rear bearing journal, the tail piece, and the nose piece is formed of metal.

3. The engine balance shaft according to claim 2, wherein: Each of the front bearing journal and the rear bearing journal has a respective front longitudinal axis and a rear longitudinal axis; as well as After the hollow tube has been inserted through the front and rear bearing journals, the axis of rotation of the balancing shaft is defined by an imaginary reference line passing through the front and rear longitudinal axes.

4. The engine balance shaft according to claim 3, wherein: The hollow tube includes a profile portion extending between the rear bearing journal and the front bearing journal.

5. The engine balance shaft according to claim 4, wherein: The profile portion includes one or more grooves and ridges.

6. The engine balance shaft according to claim 4, wherein: The hollow tube includes a first metal having a first yield strength; The front bearing journal and the rear bearing journal include a second metal having a second yield strength; and The first yield strength is lower than the second yield strength.

7. The engine balance shaft according to claim 6, wherein: The nose piece includes a first mounting surface and a first protrusion extending away from the first mounting surface, the first protrusion being configured to fit within the second end opening of the hollow tube; and The first projection is inserted into the tube passage through the second end opening until the front end of the hollow tube frictionally engages the first mounting surface.

8. The engine balance shaft according to claim 1, wherein: The side wall of the hollow tube is deformed to form a profile portion extending in a longitudinal direction of the hollow tube, the profile portion being configured to increase the bending stiffness of the hollow tube beyond the bending stiffness of the hollow tube measured before the hollow tube is assembled with the front and rear bearing journals.

9. The engine balance shaft according to claim 8, wherein: The hollow tube is a seamless tube comprising steel; The counterweight frame comprises steel and / or ductile iron; and The hollow tube has an air void within the tube passageway passing through the hollow tube.

10. The engine balance shaft according to claim 9, wherein: The nose piece is fixedly coupled to the hollow tube via a weld extending between the nose piece and one or more of the sidewall of the hollow tube, a support ring extending from the counterweight frame, and / or the counterweight frame.

11. The engine balance shaft according to claim 9, wherein: The nose piece is fixedly coupled to the hollow tube by a resilient interference fitting between the nose piece and the tube passage in the hollow tube.

12. The engine balance shaft according to claim 1, wherein: The balance shaft also includes an internal weight that is inserted into an air void within the tube passage of the hollow tube and is locked in place within the hollow tube when the hollow tube is expanded by the hydroforming process.

13. The engine balance shaft according to claim 12, wherein: The internal counterweight is positioned within the hollow tube between the front and rear bearing journals.

14. The engine balance shaft according to claim 13, wherein: The tail piece includes a second mounting surface and a second protrusion extending away from the second mounting surface, the second protrusion being configured to fit within the first end opening of the hollow tube; and The second projection is inserted into the tube passage through the first end opening until the rear end of the hollow tube frictionally engages the second mounting surface.

15. The engine balance shaft according to claim 14, wherein: The side wall of the hollow tube is deformed to form a profile portion extending in a longitudinal direction of the hollow tube, the profile portion being configured to increase the bending stiffness of the hollow tube beyond the bending stiffness of the hollow tube measured before the hollow tube is assembled with the front and rear bearing journals.

16. The engine balance shaft according to claim 15, wherein: The hollow tube is a seamless tube comprising steel; and The hollow tube has an air void within the tube passageway passing through the hollow tube.

17. The engine balance shaft according to claim 16, wherein: The tail piece is fixedly coupled to the hollow tube via a weld extending between the tail piece and the sidewall of the hollow tube.

18. The engine balance shaft according to claim 17, wherein: The nose piece is fixedly coupled to the hollow tube by a weld extending between the nose piece and the sidewall of the hollow tube.

19. The engine balance shaft according to claim 16, wherein: The tail piece is fixedly coupled to the hollow tube via a resilient interference fitting between the tail piece and the tube passage in the hollow tube.

20. The engine balance shaft according to claim 19, wherein: The nose piece is fixedly coupled to the hollow tube by a resilient interference fitting between the nose piece and the tube passage in the hollow tube.

21. The engine balance shaft according to claim 16, wherein: Each of the front bearing journal and the rear bearing journal has a respective front longitudinal axis and a rear longitudinal axis; The front longitudinal axis and the rear longitudinal axis are aligned to define an axis of rotation of the balance shaft; and The internal counterweight has a center of mass that is offset from the axis of rotation of the balance shaft.

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