Tensioner for motor vehicle accessory drive and accessory drive comprising such tensioner
By designing a tensioner for the accessory drive device, the eccentric rotation axis and the optimized tension arm position are solved in the prior art that it is difficult to effectively maintain the correct tension of the belt span, and the effect of reducing losses and improving efficiency is achieved.
Patent Information
- Application Number
- CN202380056846.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-26
- Filing Date
- 2023-03-07
- Publication Date
- 2025-03-11
AI Technical Summary
When using a reversible motor, it is difficult to effectively maintain the correct tension of the two spans of the belt, resulting in increased losses.
A tensioner for an accessory drive device is designed, including an annular base, a main annular arm, a first tension pulley, a tension arm and a second tension pulley. Loss is reduced by placing the axis TA of the ring 15 in an eccentric position with respect to the axis MA of the motor and optimizing the position of the tension arm 18 .
It realizes that when using a reversible motor, the loss of the accessory drive device is reduced and the efficiency of the system is improved.
Smart Images
Figure CN119604702A_ABST
Abstract
Description
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This patent application claims the priority of Italian Patent Application No. 102022000015750 filed on July 26, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field
[0003] The present invention relates to a tensioner for an accessory drive of a motor vehicle and an accessory drive comprising such a tensioner. Background Art
[0004] The accessory drive of an internal combustion engine generally includes a pulley connected to a drive shaft, a pulley connected to a motor shaft, and may include one or more pulleys for driving other accessories, such as a compressor of an air conditioning system. The accessory drive also includes a belt for transmitting motion between the above pulleys and a tensioner adapted to ensure the correct minimum tension level of the belt and avoid slippage between the belt and the pulleys.
[0005] In a conventional accessory drive, in which the electric motor is an alternator driven by an internal combustion engine, the tensioner acts on the loose span of the belt, ie the span downstream of the engine and upstream of the alternator relative to the direction of movement of the belt.
[0006] In motor vehicles, reversible electric machines are increasingly used instead of conventional alternators, which, in addition to the conventional generator mode, can also be operated according to other modes, for example as regenerative braking (so-called "recovery" condition), or as an additional electric motor acting in combination with the internal combustion engine (so-called "boost" condition).
[0007] The use of a reversible electric machine means that the span of the belt, which is tensioned under operating conditions in which the electric machine is dragged by the internal combustion engine, becomes a slack span when the drive torque is transmitted by the electric machine.
[0008] Therefore, various solutions have been developed that allow ensuring the correct tensioning of both spans of the belt.
[0009] For example, one solution consists in using a tensioner having two arms articulated in a common pin and bearing respective pulleys. The arms are acted upon by the elastic force of a spring which tends to bring the arms closer together so as to keep the pulleys in contact with the respective spans of the belt. An example of such a solution is described in EP 1581753-A. The common axis of the two arms is arranged in the path of the belt.
[0010] The obstacles of the base on which the arm is articulated and of the springs arranged around the common articulation axis of the arm itself are such that these obstacles make this solution unsuitable for applications where there are packaging constraints within the path of the belt, such as, for example, in the case where the drive only provides two pulleys. Furthermore, the arrangement of the arm with respect to the resultant of the forces acting on the pulleys is not optimal.
[0011] Another solution is to mount the tensioner on the motor.
[0012] According to a known solution, the tensioner comprises a base, a first annular element and a second annular element, wherein the base is suitable for being fixed to the base of the motor, the first annular element being rotatable relative to the base around the axis of the motor and supporting the first pulley, and the second annular element being rotatable relative to the base around the axis of the motor and supporting the second pulley.
[0013] A spring acts between the two annular elements, the spring being adapted to exert an elastic force between the elements themselves and to keep the first and second pulleys in contact with the respective spans of the belt.
[0014] A disadvantage associated with the above solutions is the need to operate at relatively high tensions in the belt to allow optimal operation in both recovery and assist conditions.
[0015] According to another known solution, the tensioner comprises a base suitable for being fixed to the motor, an annular element surrounding the axis of the motor relative to the base and carrying a first pulley, and an arm articulated to the annular element and carrying a second pulley.
[0016] The object of the present invention is to achieve a tensioner of the latter type for an accessory drive which has a higher efficiency and allows reducing the losses in the accessory drive. Summary of the invention
[0017] The above object is achieved by a tensioner for an accessory drive according to claim 1 .
[0018] A further object of the invention is to achieve an accessory drive with reduced losses.
[0019] This object is achieved by an accessory drive according to claim 15 . BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a better understanding of the invention, preferred embodiments are described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:
[0021] Figure 1 is a schematic front view of an accessory drive device including a tensioner according to the present invention;
[0022] Figure 2yes Figure 1 A front view of a tensioner;
[0023] Figure 3 It is along Figure 2 A cross-sectional view taken along line III-III;
[0024] Figure 4 It is along Figure 2 A partial cross-sectional view taken along line IV-IV of ;
[0025] Figure 5 It is along Figure 2 A partial cross-sectional view taken along line VV of ;
[0026] Figure 6 and Figure 7 The operation of the tensioner varies with its geometric parameters. Figure 1 A graph showing the energy consumed by the accessory drive device;
[0027] Figure 8 is a schematic front view of an accessory drive including a tensioner in accordance with various embodiments of the present invention; and
[0028] Fig. 9 and Fig.10 The operation of the tensioner varies with its geometric parameters. Figure 8 A graph showing the energy consumed by the accessory drive device;
[0029] Fig.11 is a schematic front view of an accessory drive device including a tensioner according to a third embodiment of the present invention;
[0030] Fig.12 yes Fig.11 A front view of a tensioner;
[0031] Fig.13 and Fig.14 is based on Fig.11 Cross-sectional views along lines XIII-XIII and XIV-XIV. DETAILED DESCRIPTION
[0032] refer to Figure 1 , 1 represents an accessory drive device of the internal combustion engine 2.
[0033] The accessory drive 1 comprises a first pulley 3, a second pulley 5 and a belt 8, wherein the first pulley 3 is connected to a drive shaft 4 of the internal combustion engine 2 and has an axis EA, the second pulley 5 is connected to a shaft 6 of an electric motor 7 and has an axis MA, and the belt 8 connects the first pulley 3 and the second pulley 5 together. Optionally, the accessory drive 1 may comprise other pulleys for driving other accessories of the internal combustion engine 2. Figure 1By way of example, a third belt pulley 9 of a compressor of an air-conditioning system is shown.
[0034] The accessory drive device 1 further includes a tensioner 10, which is mounted on the motor 7 and includes ( Figures 2 to 5 ):
[0035] The annular base 11 integrally comprises a flat flange 12 and an annular collar 14, wherein the flat flange 12 is adapted to be fixed to a housing 13 ( Figure 1 ), the annular collar 14 having an axis TA which, in use, does not coincide with the axis MA, as will be better described below, and which extends axially cantilevered from the flange 12;
[0036] A main annular arm 15 (hereinafter referred to as "ring 15") having an axis TA is rotatably supported on the base 11 about the collar 14. Figures 3 to 5 );
[0037] The first tensioning pulley 16 is formed by the outer radial appendage 17 ( Figure 5 ) carries and can rotate relative to the external radial appendage 17 about an axis PA1, the axis PA1 being parallel to the axis MA and the axis TA;
[0038] a tensioning arm 18 rotatably supported on the ring 15 and rotatable relative to the ring 15 about an axis AA parallel to the axis MA and the axis TA and circumferentially spaced relative to the axis PA1 ; and
[0039] A second tensioning pulley 19 is carried by the tensioning arm 18 and is rotatable relative to the tensioning arm about an axis PA2 parallel to the axis MA and to the axis TA.
[0040] More specifically, the ring 15 is interposed axially between a lower bushing 21 which supports the ring 15 axially on the flange 12 and radially relative to the collar 14 of the base 11, and an upper damping ring 22 which is pressed against the ring 15 by means of an elastic or "flex plate" stop ring 23. The stop ring 23 is locked on the collar 14 of the base 11 by a thread rolling operation so as to deform conically and exert an axial force on the damping ring 22.
[0041] The tensioning arm 18 is rotatably mounted on a pin 24 having an axis AA extending axially cantilevered from the ring 15 .
[0042] For this purpose, the tensioning arm 18 is provided with a hub 25 provided with a through hole 26 of axis AA and defining a cylindrical seat 27 coaxial with the hole 26 and open axially towards the ring 15 .
[0043] The pin 24 engages with the hole 26 of the hub 25 by interposing a radial and axial support bushing 28 and is axially locked by a stop ring 28 ′ fitted on the free end of the pin 24 .
[0044] The torsion spring 29, the end portion 30 of which is housed in the seat 27 of the hub 25 and constrained to its own opposite end (not visible in the figure), exerts on the tensioning arm 18 a force tending to bring the pulleys 16 and 19 closer together, thus keeping the pulleys 16 and 19 in contact with the corresponding spans 8a, 8b of the belt 8 arranged on the opposite side of the second pulley 5 (taking into account the direction of movement of the belt 8 (which is referred to as the direction of movement of the belt 8)). Figure 1 is in clockwise direction), respectively downstream and upstream of the second pulley 5).
[0045] According to the invention, the rotation axis TA of the ring 15 does not coincide with the axis MA of the pulley 5 of the motor 7. In particular, the axis TA is symmetrical relative to the axis MA in static equilibrium relative to the resultant HL ( Figure 1 ) direction.
[0046] The inner diameter of the collar 14 is dimensioned to allow the tensioner 10 to be mounted on the motor 7 in the presence of the second pulley 5, with the obstruction being Figure 3 Therefore, this diameter must be at least equal to the outer diameter of the second pulley 5 plus twice the distance between the axis TA and the axis MA (hereinafter referred to as "eccentricity").
[0047] Figure 6 is a graph showing the values of energy consumed by operating the drive device 1 for various positions A, B, ..., H of the axis TA around the axis MA during the WLTP homologation cycle, expressed in equivalent emissions [g CO2 / km], and under the condition that the axis TA coincides with the axis MA (eccentricity 0). Each of the positions A, B, ..., H has an eccentricity equal to 8 mm and the angular spacing between the various positions is equidistant by 45°, as shown in the following table:
[0048]
[0049] Table 1
[0050] By looking at the values associated with the graph, it is apparent that the point having an eccentricity facing the opposite side with respect to the hub load HL has a lower loss value than the condition without eccentricity (point MA).
[0051] According to a preferred embodiment of the present invention, the axis TA is within an angle of 180°, and more preferably within an angle of 90°, with its vertex coinciding with MA and the line of action of the hub load HL as a bisector. Figure 6 Highlighted with cross-hatching.
[0052] The optimum point O associated with lower losses is displaced from the opposite side of the tensioning arm 18 relative to the line of action of the hub load HL. Figures 1 to 5 In the embodiment in which the tensioning arm 18 is located to the left of the hub load HL, the condition of optimum eccentricity which minimizes the energy consumed in the authorized cycle is located to the right of the line of action of the hub load HL.
[0053] Figure 7 is a graph showing the values of the energy consumed for operating the drive device 1 during the WLTP approval cycle, expressed in equivalent emissions [g CO2 / km], as a function of the eccentricity rTA of the axis TA relative to the axis MA and of the angle αTA, i.e. the direction of the eccentricity (measured in ° starting from the axis of the abscissa of the graph): it can be clearly seen how this energy decreases with increasing eccentricity and has a minimum value.
[0054] In this case, for an eccentricity equal to 8 mm, the minimum value (3467 g CO2 / km) is at αTa=38.18°.
[0055] Obviously, the eccentricity cannot be increased infinitely to avoid interference between the ring 15 and the second pulley 5 and to inhibit blocking of the tensioner 10 during operation.
[0056] Figure 8 A different embodiment of the invention is shown in which a first tensioning pulley 16 carried by the ring 15 acts on the span 8b of the belt 8 and a second tensioning pulley 19 carried by the tensioning arm 18 acts on the span 8a of the belt 8. In other words, in this case, the tensioning arm 18 is located to the right of the line of action of the hub load HL and the first tensioning pulley 16 is located to the left.
[0057] Fig. 9 and 10 Equivalent to Figure 6 and Figure 7 , and there are completely consistent results.
[0058] Points A, B, ..., H are selected using the same criteria (8 mm eccentricity, 45° angular spacing around the axis MA).
[0059]
[0060]
[0061] Table 2
[0062] Also in this case, by looking at Fig. 9 From the graph of the values associated with , it is obvious that the point with the eccentricity facing the opposite side with respect to the hub load HL has a lower loss value than the condition without eccentricity (point MA).
[0063] According to a preferred embodiment of the present invention, the axis TA is within an angle of 180°, and more preferably within an angle of 90°, with its vertex coinciding with MA and the line of action of the hub load HL as the bisector. Fig. 9 Highlighted with cross-hatching.
[0064] The optimum point O associated with lower losses is displaced from the opposite side of the tensioning arm 18 relative to the line of action of the hub load HL. Figure 8 In the embodiment in which the tensioning arm 18 is located to the right of the hub load HL, the condition of optimum eccentricity which minimizes the energy consumed in the authorized cycle is located to the left of the line of action of the hub load HL.
[0065] Fig.10 The graph of φ shows even more clearly how the energy consumed to operate the drive device 1 decreases with increasing eccentricity and has a minimum value.
[0066] In this case, for an eccentricity of 8 mm, the minimum value (3237 g CO2 / km) is at αTa = 59.22°.
[0067] Fig.11 There is schematically shown an accessory drive 1 which is completely similar to the previous drive, provided with a tensioner 40 according to a third embodiment of the invention.
[0068] Tensioner 40( Figure 12 to Figure 14 ) is functionally equivalent to reference Figures 2 to 5 The tensioner 10 is described hereinbelow and its structural differences are described below, with the same reference numerals being used to identify parts that are the same as or correspond to parts already described.
[0069] The tensioner 40 comprises a base 11 which integrally comprises an arcuate flange 12 which, in use, faces a circumferential portion of a housing of a motor (not shown) and is adapted to be fixed to said housing by means of a plurality of screws 41. The base 11 further comprises an annular collar 14 which extends in a plane parallel to the plane of the flange 12 and is cantileveredly connected to the flange 12 by means of a stepped joint portion 42.
[0070] As will be better described below, a collar 14 having an axis TA which, in use, does not coincide with the axis MA, is axially spaced from the flange 12 so as to extend beyond the second pulley 5 in the axial direction so as to face the second pulley 5 axially.
[0071] The tensioner 40 further comprises, in a manner similar to that described with respect to the tensioner 10:
[0072] A main arm 15, having an axis TA, is rotatably supported by the collar 14 ( Fig.13 and Fig.14 );
[0073] The first tensioning pulley 16 is formed by an outer radial attachment 17 ( Fig.12 and Fig.14 ) is carried, the first tensioning pulley 16 can rotate relative to the main arm 15 about an axis PA1 parallel to the axis MA and the axis TA, and cooperates with the span 8a of the belt 8;
[0074] a tensioning arm 18 rotatably supported on the ring 15 and rotatable relative to the ring 15 about an axis AA parallel to the axis MA and the axis TA and circumferentially spaced relative to the axis PA1 ; and
[0075] A second tensioning pulley 19 , carried by the tensioning arm 18 , is rotatable relative to the tensioning arm about an axis PA2 parallel to the axes MA and TA and acts on the span 8 b of the belt 8 .
[0076] The mode of connection of the main arm 15 to the collar 14 and of the tensioning arm 18 to the main arm 15 is identical to that described with reference to the tensioner 10 .
[0077] According to the invention, as already indicated, the rotation axis TA of the main arm 15 of the tensioner 40 does not coincide with the axis MA of the second pulley 5 of the motor 7. In particular, the axis TA is symmetrical relative to the axis MA in static equilibrium conditions relative to the resultant HL ( Fig.11 ) direction.
[0078] The relative arrangement of the axes TA, MA, PA1 and PA2 is identical to that of the corresponding axes of the tensioner 10, and the kinematic and dynamic behavior of the tensioner 40 is very similar to that of the tensioner 10. Therefore, in terms of energy savings and eccentricity optimization, the same data explained above with reference to the tensioner 10 apply.
[0079] Since in this case the collar 14 and the main arm 15 are arranged facing the second pulley 5 instead of surrounding it, no restriction is imposed on their size in the radial direction. This allows to free up the size and positioning of the collar 14 and the main arm 15 with respect to the eccentricity value, which can then be increased without increasing the radial obstruction of the tensioner 40.
[0080] According to a variant embodiment of the tensioner 40, the first tensioning pulley 16 carried by the main arm 15 acts on the span 8b of the belt 8, and the second tensioning pulley 19 carried by the tensioning arm 18 acts on the span 8a of the belt 8. In other words, in this case, the tensioning arm 18 is located to the right of the line of action of the hub load HL, and the first tensioning pulley 16 is located to the left.
[0081] According to a further variant embodiment, the main arm 15 and / or the tensioning arm 18 may be supported by rolling bearings instead of sliding bearings.
[0082] By examining the features of the invention, the advantages which the invention allows to obtain are evident.
[0083] In particular, by arranging the axis of the ring 15 in an eccentric position relative to the axis of the electric motor, advantages can be achieved with regard to the energy consumed for operating the accessory drive and thus reducing emissions.
[0084] Finally, it is clear that modifications and variations may be made to the described embodiments without departing from the scope of protection defined by the claims.
[0085] For example, the approval cycle may be another type of approval cycle other than the WLTP approval cycle described above.
Claims
1. A tensioner for an accessory drive device of an internal combustion engine (2), the drive device (1) comprising at least one first pulley (3), at least one second pulley (5) and a belt (8), the at least one first pulley (3) being connected to a drive shaft (4) of the internal combustion engine (2) and having a first axis (EA), the at least one second pulley (5) being connected to a motor (7) and having a second axis (MA), the belt (8) being wound around at least the first pulley (3) and the second pulley (5), the tensioner (10) comprising: - a base (11) suitable for being fixed to a housing (13) of the electric motor (7); - a main arm (15) rotatable relative to the base (11) about a third axis (TA); - a first tensioning pulley (16) carried by the main arm (15) and rotatable relative to the main arm about its own axis (PA1); - a tensioning arm (18) carried by the main arm (15) and articulated to the main arm (15) about a fourth axis (AA); - a second tensioning pulley (19) carried by the tensioning arm (18) and rotatable relative to the tensioning arm about its own axis (PA2); and - elastic means (29) acting on the main arm (15) and the tensioning arm (18) to push the first tensioning pulley (16) and the second tensioning pulley (19) into contact with the corresponding spans (8a; 8b) of the belt (8), Characterized in that the third axis (TA) is displaced relative to the second axis (MA) in an eccentric direction chosen so as to minimize the energy required to operate the drive device (1) in an authorized cycle.
2. The tensioner according to claim 1, wherein: The approval cycle is the WLTP approval cycle.
3. The tensioner according to claim 1 or 2, wherein: The eccentric direction extends on the opposite side of the direction of the resultant force (HL) of the forces exerted by the belt (8) on the second pulley (5) relative to the second axis (MA).
4. The tensioner according to claim 3, wherein: The eccentric direction is located within an angle of 180° with the second axis (MA) as the origin and the line of action of the resultant force (HL) as the bisector.
5. The tensioner according to claim 3, wherein: The eccentric direction is located within an angle of 90° with the second axis (MA) as the origin and the line of action of the resultant force (HL) as the bisector.
6. The tensioner according to any one of claims 2 to 5, wherein: The third axis (TA) is located relative to the tensioning arm (18) on the opposite side of the line of action of the resultant force (HL).
7. A tensioner according to any one of the preceding claims, wherein: The main arm (15) is annular.
8. A tensioner according to any one of the preceding claims, wherein: The base (11) and the main arm (15) have corresponding openings, the size of which is designed to accommodate the second pulley (5), and the eccentricity of the third axis (TA) relative to the second axis (MA) is selected within the maximum possible value to avoid interference with the second pulley (5).
9. The tensioner according to claim 8, wherein: The eccentricity of the third axis (TA) relative to the second axis (MA) is chosen to be the largest possible value in order to avoid interference with the second pulley (5).
10. The tensioner according to any one of claims 1 to 7, wherein: The base (11) includes a flange (12) for connecting to the housing (13) of the motor (7), and is configured so that the main arm (15) is supported in a position facing the second pulley (5).
11. The tensioner according to claim 10, wherein: The first tension pulley (16) and the second tension pulley (19) extend axially from one side of the flange (12) from the main arm (15) and from the tension arm (18), respectively.
12. A tensioner according to any one of the preceding claims, wherein: The main arm (15) is axially interposed between the base (11) and an annular stop element (23).
13. The tensioner according to claim 12, wherein: The stop element (23) is elastic and applies an axial load to a damping ring (22) axially interposed between the stop element (23) and the main arm (15).
14. The tensioner according to claim 13, comprising a bushing (21) interposed between the main arm (15) and the base (11) to support the main arm (15) radially and axially relative to the base (11).
15. An accessory drive device, comprising: At least one first pulley (3), which is connected to the drive shaft (4) of the internal combustion engine (2) and has a first axis (EA); at least one second pulley (5), which is connected to the motor (7) and has a second axis (MA); a belt (8), which is wound around at least the first pulley (3) and the second pulley (5); and a tensioner (10) according to any of the preceding claims.
16. The driving device according to claim 15, wherein: The first tensioning pulley (16) and the second tensioning pulley (19) of the tensioner act on spans (8a, 8b) of the belt (8) arranged on opposite sides of the second pulley (5).
17. A drive device according to any one of the preceding claims, wherein: At least one of the main arm (15) and the tensioning arm (18) is supported by a rolling bearing.