FR3031784A1 - BALANCING SHAFT AND INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The invention relates to a balancer shaft (10) adapted to be rotated by a crankshaft of an internal combustion engine. The balancer shaft (10) being provided with bearings (12, 13, 14) to be rotatably mounted in a frame of the internal combustion engine as well as a cam (16) for interaction with a roller cam follower (18) for a fuel injection pump. The invention proposes that two of said bearings (12, 13, 14) are placed in close proximity to both axial sides of the cam (16).

Description

The present invention relates to a balancing shaft and an internal combustion engine comprising at least one balancing shaft.

Internal combustion engines may include balancing systems that compensate for engine vibrations due to piston movement. An internal combustion engine sometimes comprises a single balancing shaft, but more generally two balancing shafts rotated in phase opposition by a crankshaft gear of the internal combustion engine. Balancing shafts generally comprise at least one eccentric mass, which causes radial and axial loads increasing with the speed of rotation of the balancing shafts. Balancer shafts are usually mounted in internal combustion engine mounts via ball, needle or roller bearings. It is known from US-A-2011/0247581 that one can equip balancing shafts of single-row ball bearings. Such bearings have uncontrollable axial clearance which will generate significant noise and pollution and have a reduced service life when used to support balancing shafts. It is known from US Pat. No. 7,823,567 B2 that a balance shaft of a cam can be provided for interaction with a cam follower roller for an internal combustion engine fuel injection pump. The integration of a cam in a balancer shaft imposes limitations, concerning the axial play of the balance shaft, which is difficult to meet, especially considering the axial forces generated by the gear wheels of the crankshaft to helical profile. Invention Patent FR 2 913 739 describes a process for manufacturing paired bearings.

It is these drawbacks that the invention intends to remedy by proposing a new internal combustion engine, whose balancing shafts equipped with a cam are supported in rotation more reliably than in the state of the art. To this end, the invention relates to a balancer shaft adapted to be rotated by a crankshaft of an internal combustion engine, said balancing shaft being equipped with bearings for being mounted freely in rotation in an engine frame. internal combustion. The balance shaft has a cam for interaction with a cam follower roller for an internal combustion engine fuel injection pump. This internal combustion engine is characterized in that two of said bearings are placed in close proximity to both axial sides of the cam. It is thus possible to take up the axial loads introduced by the cam follower in a very efficient manner. According to a preferred embodiment, an axial distance between the axial faces of the cam and the axial faces of said two bearings is less than 1 cm, preferably even less than 0.5 cm. In the context of the invention, the expression "in close proximity" means that there is no functional unit or unnecessary space between the cam and the bearings. According to one embodiment of the invention, the balancer shaft comprises an unbalance. The invention proposes that at least one of the two bearings is placed between the unbalance and the cam. Thus, it is possible to use a centrifugal force generated by the eccentric mass of the unbalance in a very efficient manner. In a preferred configuration, a radial clearance of the bearing placed between the unbalance and the cam is greater than the radial clearance of the other of the two bearings. It is thus possible to obtain a homogeneous distribution of the radial forces on the bearings. According to one embodiment of the invention, the balancer shaft is equipped with at least one third bearing placed on one axial side of the opposite unbalance 30 of the cam.

According to one embodiment of the invention, said bearings are double-row rolling element bearings each comprising two rolling-row rolling element bearings paired with each other. Thanks to the invention, the axial play of the bearings which support the rotation of the balance shafts can be canceled, which makes it possible to reduce the noise produced by the bearings, to reduce the wear of the cam follower roller and its track. of rolling and extend their life. According to the advantageous but not obligatory aspects of the invention, such an internal combustion engine may incorporate one or more of the following features, taken in any technically permissible combination: the rolling elements are balls, rollers or needles. In addition, the bearings can be angular or straight contact. According to a preferred embodiment, the single-row rolling element bearings comprise a first ring and a second ring manufactured in such a way that there is an axial gap between the axial surfaces of the first ring and the second ring in a configuration without axial forces. Preferably, these single-row rolling element bearings are paired such that the two rolling-row rolling element bearings, constituting one of the double-row rolling element bearings, have complementary axial gaps. According to a preferred embodiment, the single row ball bearings are deep groove ball bearings whose rings have a toroidal circular groove forming a raceway.

Balls are disposed between the races and are held at regular circumferential spacing by a cage. The bearing is mounted with a certain radial and axial internal clearance, which depends on the diameter of the bottom grooves of the rings, the diameter of the balls, and the radius of the races in cross section by an axial plane.

The internal clearance of the bearing results in the possibility of a slight radial displacement exerted on one ring relative to the other, under the action of a radial or axial force exerted on one of the rings.

Thanks to the ability to withstand high axial loads, the invention allows the combination of a cam with a helical profile gear on the same balancer shaft. For bearing matching, the bearings are manufactured and selected which, when arranged side by side and face to face, form an assembly which has an axial clearance close to zero and a certain contact angle between the balls and the balls. runways in order to operate by supporting both radial load and axial load. The manufacture of single-row ball bearings may include a grinding step to reduce the width of one of the rings, which are first manufactured with equal axial width. By width is meant the axial dimension of a frontal radial surface to the other. The assembly thus formed forms a rolling bearing operating with an axial clearance very close to zero and capable of supporting axial and radial loads. According to one embodiment of the invention, the bearings allowing the rotation of the balancing shaft are in oblique contact. In another embodiment of the invention, the bearings allowing rotation of the balancer shaft are in straight contact.

According to one embodiment, the actual axial differences are measured for a plurality of bearings and the bearings having complementary or zero deviations are matched. The selection of the bearings for the appairment can also be performed by measuring the relative distances of the radial end surfaces of the rings and by applying opposite axial forces. The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an internal combustion engine according to its principle, given by way of non-limiting example with reference to the attached drawings in which: - Figure 1 is a sectional view of an internal combustion engine according to the invention; FIG. 2 is an enlarged view of detail II of FIG. 1. A balancer shaft 10 of an internal combustion engine M is shown in FIG. 1. The engine M comprises a frame B. The internal combustion engine M comprises a crankshaft (not shown), one end of which is provided with a gear wheel. The toothed wheel of the crankshaft is engaged with a toothed wheel 20 of the balancer shaft 10, which is rotatably mounted in two supports 22 of the frame B. The rotation of the balancer shaft 10 in the supports is allowed by three radial bearings 12, 13 and 14 double row 10 of rolling elements on a first side of the helical gear wheel 20. A fourth axial bearing 15 is placed on a second side of the gear wheel. The balancer shaft 10 has an eccentric or unbalanced mass 42 which provides the desired compensation for vibrations due to the displacement of the pistons, which are not shown for the sake of clarity. According to the invention, the balancer shaft 10 includes a cam 16 for interaction with a cam follower roller 18 for a fuel injection pump. The first bearing 12 is placed on a first end of the balancer shaft 10 in close proximity to the axial side of the cam 16 spaced apart from the gear wheel 20. A second bearing 13 is placed on the balancer shaft 10 in the immediate vicinity of the axial side of the cam 16 facing the gear wheel 20. It is thus possible to take up the axial loads 25 introduced by the cam follower 18 in a very efficient manner. An axial distance between the axial faces of the cam 16 and the axial faces of the bearings 12 and 13 is less than 1 cm, preferably even less than 0.5 cm. The balance shaft 10 comprises an unbalance 42. The second bearing 13 30 is placed between the unbalance 42 and the cam. Thus, it is possible to use a centrifugal force generated by the eccentric mass of the unbalance 42 in a very efficient manner. The radial clearance of the bearing 13 placed between the unbalance 42 and the cam 16 is greater than the radial clearance of the first bearing 12. It is thus possible to obtain a homogeneous distribution of the radial forces on the bearings 12, 13 and 14. The third bearing 14 is placed on an axial side of the unbalance 42 spaced from the cam 16. In practice, the internal combustion engine comprises two balance shafts 10 and each of these balancing shafts can be rotatably mounted using four or more bearings . The double row rolling element bearings 12, 13 and 14 each comprise two bearings 12a, 12b; 13a; 13b; 14a and 14b to a row of rolling elements paired with each other. The bearings 12a, 12b; 13a; 13b; 14a and 14b to a row of rolling elements are bearings with straight contacts. In particular, each of the two bearings 12a, 12b; 14a, 14b to a row of rolling elements comprises a first ring and a second ring manufactured in such a way that there is an axial gap between the axial surfaces of the first ring and the second ring, in a configuration without axial forces. The bearings 12a, 12b; 13a, 13b, 14a and 14b to a row of rolling elements are selected and paired such as the bearings 12a, 12b; 13a; 13b; 14a and 14b to a row of rolling elements constituting one of rolling bearings 12, 13, 14 double row of rolling elements have complementary axial deviations. According to one embodiment, the double row rolling element bearings 12, 13 and 14 are lubricated by a lubricating oil of the internal combustion engine M. According to one embodiment, the double row bearings 12, 13 and 14 rolling elements are equipped with seals which maintain, in a rolling chamber defined by said seals, a lubricant, such as an oil or a grease, disposed before assembling said seals with the bearing rings.

Appearance of bearings 12a, 12b; 13a; 13b; 14a and 14b eliminates the noise generated by the operation of the bearings 12, 13 and 14 by eliminating the axial play. As shown in Figure 2 for the bearing 12 only, the bearing 12 has a first bearing 12a single row of balls and a second bearing 12b single row of balls. Each of the bearings 12a and 12b respectively comprises a row of balls disposed between an inner ring and an outer ring. The bearings 12a and 12b are contiguous to each other along an axis of rotation which also corresponds to the longitudinal axis of the bearings 12a and 12b. The inner rings and the outer rings are contiguous to one another by a surface contact between the lateral faces of the bearing 12a and the lateral faces of the bearing 12b opposite the lateral faces of the bearing 12a. The technical features of the embodiments and variants described above may be combined within the scope of the present invention as defined in the claims.

Claims (10)

REVENDICATIONS1. Balancing shaft (10) adapted to be rotated by a crankshaft of an internal combustion engine, said balancer shaft (10) being provided with bearings (12, 13, 14) to be freely rotatably mounted in a frame of the internal combustion engine and a cam (16) for interaction with a cam follower roller (18) for a fuel injection pump, characterized in that two of said bearings (12, 13, 14) are placed in close proximity to both axial sides of the cam (16). 2. balancing shaft according to claim 1, characterized in that an axial distance between the axial faces of the cam and the axial faces of said two bearings is less than 1 cm. Balancing shaft according to one of the preceding claims, characterized in that the balance shaft (10) comprises an unbalance (42) and in that at least one of said two bearings is placed between the unbalance ( 42) and the cam (16). Balancing shaft according to one of the preceding claims, characterized in that a radial clearance of the bearing (13) placed between the unbalance (42) and the cam (16) greater than the radial clearance of the other of the two bearings (12). Balancing shaft according to one of claims 3 and 4, characterized in that said balancing shaft (10) is equipped with at least one third bearing (12, 13, 14) placed on an axial side of the unbalance (42) spaced from the cam (18). 303 1,784 9 6. balancing shaft according to one of the preceding claims, characterized in that said bearings (12, 13, 14) are double-row rolling element bearings. 5 7. balancing shaft according to claim 6, characterized in that said two bearings (12, 13, 14) comprise two bearings (12a, 12b; 14a, 14b) with a row of rolling elements paired with each other. 'other. Balancing shaft according to Claim 7, characterized in that each of the two rolling element bearings (12a, 12b, 14a, 14b) comprises a first ring and a second ring manufactured in such a way that it there is an axial gap between axial surfaces of the first ring and the second ring in a configuration without axial forces, the bearings (12a, 12b; 14a, 14b) with a row of rolling elements being paired in such a way that the 15 rolling-element bearings (12a, 12b; 14a, 14b) constituting one of the double-row roller bearings (12, 13, 14) have complementary axial deviations. 9. balancing shaft according to one of the preceding claims, characterized in that said balancing shaft (10) comprises a toothed wheel 20 (20) helical profile. 10. Internal combustion engine comprising a balancing shaft according to one of the preceding claims.