Tensioner for an accessory drive of a motor vehicle and accessory drive comprising such a tensioner

Abstract

Double-arm tensioner for an accessory drive (2) of an internal combustion engine (1), comprising: a first arm (11) and a second arm (12) rigidly connected to each other and rotating about a common rotation axis (A); a first pulley (13) connected to the first arm (11) and rotatable about its own first axis (C); a second pulley (14) connected to the second arm (12) and rotatable about its own second axis (E), wherein the first pulley (13) is carried by a working arm (17) linked to the first arm (11) and rotatable with respect to the first arm about a third axis (B) different from the first axis (D); and an elastic element (18) configured to exert on the working arm (17) an elastic force tending to bring the first pulley (13) closer to the second pulley (14), the third axis being internal to the first pulley.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102020000006433, filed on March 26, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a tensioner for an accessory drive for a motor vehicle and an accessory drive including such a tensioner. Background Technology

[0004] An accessory drive for an internal combustion engine typically includes pulleys connected to the crankshaft, pulleys connected to the shaft of the electric motor, and may include one or more pulleys for driving other accessories (such as the compressor of an air conditioning system). The accessory drive also includes: a belt for transmitting motion between these pulleys; and a tensioner configured to ensure the correct minimum tension level of the belt and to prevent slippage between the belt and the pulleys.

[0005] In a traditional accessory drive, the motor is an alternator driven by an engine, and the tensioner acts on the slack span of the belt, which is located downstream of the engine and upstream of the alternator relative to the direction of belt movement.

[0006] In motor vehicles, reversible motors are increasingly being used instead of traditional alternators. These motors can operate in modes other than the traditional generator mode, such as as regenerative brakes or as an auxiliary motor used in conjunction with an internal combustion engine.

[0007] The use of a reversible motor means that the tensioned belt span under operating conditions where the motor is driven by an engine becomes a slack span when the motor transmits the driving torque.

[0008] Therefore, various solutions have been developed to ensure proper tension of the belt span.

[0009] One solution, for example, involves using a tensioner with two arms hinged to a common pivot and carrying respective pulleys. The arms are subject to a spring force that tends to bring them closer together to maintain contact between the pulleys and the corresponding belt span. An example of this solution is described in EP 1581753-A. The common axis of the two arms is arranged within the belt path.

[0010] The dimensions of the base on which the arm is hinged and the dimensions of the springs arranged around the common hinge axis of the arm make this solution unsuitable for applications where there are packaging constraints within the belt path, such as, for example, where the drive has only two pulleys. Furthermore, the arm arrangement is not optimal in terms of the resultant force acting on the pulleys.

[0011] Another solution is to mount the tensioner on the motor.

[0012] According to the first solution, the tensioner includes a first annular element rotatable about the axis of the motor and carrying a first pulley, and a second annular element rotatable about the axis of the motor and carrying a second pulley. A spring acts between the two annular elements to apply a spring force between the two annular elements to maintain the first and second pulleys in contact with the corresponding belt span.

[0013] In another known solution, instead of the second annular element, a circumferential sliding arm is used relative to the annular element and carrying the second pulley; a spring is placed between the annular element and the arm to push the pulley into contact with the belt.

[0014] These solutions are relatively heavy and expensive. Summary of the Invention

[0015] The object of this invention is to provide a tensioner for an accessory drive that has reduced weight and cost compared to known solutions.

[0016] This objective is achieved by the tensioner for the accessory drive as described in claim 1.

[0017] Because of the use of two arms joined together, the load acting on the pulleys in the tensioning span of the belt (“hub load”) is transferred to the slack span, thus facilitating tensioning; however, the presence of a working arm and elastic element in one of the pulleys allows for the filtering of tension spikes under certain operating conditions. Therefore, the belt operates at a lower average tension, and the tensioner can be easily sized to accommodate the lower average load, making it lighter and cheaper.

[0018] Because the working arm is located inside one of the two pulleys, this feature advantage can be obtained without additional burden.

[0019] Using two arms rigidly connected to each other also reduces the overall size around the axis of rotation of the arms, where no springs are used.

[0020] The present invention also relates to an accessory driver according to claim 10. Attached Figure Description

[0021] To better understand the invention, preferred embodiments are described by way of non-limiting examples and with reference to the accompanying drawings, wherein:

[0022] Figure 1 It is a schematic plan view of the transmission system of a motor vehicle equipped with an accessory drive according to the present invention;

[0023] Figure 2 yes Figure 1 A schematic diagram of an accessory drive, which is equipped with a tensioner according to the invention;

[0024] Figure 3 This is a schematic diagram of an accessory driver according to a variant of the present invention;

[0025] Figure 4 This is a front view of a tensioner according to another variant of the invention;

[0026] Figure 5 This is a partial mid-section view of a tensioner according to another embodiment of the present invention.

[0027] Figure 6 yes Figure 5 A cross-sectional view taken along line VI-VI. Detailed Implementation

[0028] refer to Figure 1 Reference numeral 1 indicates the internal combustion engine of a motor vehicle equipped with an accessory drive according to the invention.

[0029] The accessory drive 2 includes: a first pulley 3 connected to the crankshaft 4 of the engine 1 and having an axis EA; a second pulley 5 connected to the shaft 6 of the motor 7 and having an axis MA; and a belt 8 connecting the first pulley 3 and the second pulley 5. The accessory drive may include other pulleys (not shown) for driving other accessories of the engine 1, such as an air conditioning system compressor.

[0030] The accessory drive 2 also includes a double-arm tensioner 10, which includes: a first arm 11 and a second arm 12 rigidly connected together and rotatable about a common axis of rotation A; a first pulley 13 coupled to the first arm 11; and a second pulley 14 coupled to the second arm, as described better later. Axis A is conveniently defined by pins configured to be fixed to the crankcase of the engine 1 by means of screws.

[0031] The first and second pulleys 13 and 14 engage with the corresponding spans 15 and 16 of the belt 8, and are rotatable about the first axis B and the second axis C, respectively. Specifically, the first pulley 13 acts along the direction of rotation of the pulley (refer to...). Figure 2The view (clockwise) shows a span 15 extending between the first pulley 3 and the second pulley 5, while the second pulley 14 acts on a span 16 extending between the second pulley 5 and the first pulley 3, with the same rotational direction as the reference pulley. When the internal combustion engine 1 drives the electric motor 7, the span 16 is the tension span of the belt 8, and the span 15 is the slack span; conversely, when the electric motor 7 drives the internal combustion engine 1 (turbocharged), the span 15 is the tension span, and the span 16 is the slack span.

[0032] The first pulley 13 is connected to the first arm 11 via a working arm 17, which is rotatable relative to the arm 11 about a third axis D different from axis B; the first pulley 13 is rotatable relative to the working arm 17 about axis B. Axes B and D are parallel to each other and parallel to axis A, and their distance is such that axis D is contained within the overall dimensions of pulley 13, i.e., within a cylinder defined by the outer surface of pulley 13.

[0033] The working arm 17 is loaded by a spring 18 so as to push the first pulley 13 toward the second pulley 14 and abut against the section 15 of the belt 8 when in use.

[0034] The working arm 17 is kinematically defined by the distance between axes B and D. The working arm 17 is conveniently constructed via an eccentric device defined by a cylindrical pin having axis B, and the first pulley 13 rotates about axis B via the insertion of a bearing (not shown). The eccentric device has an axial eccentric hole having axis D, in which a pin 19 is received. The pin 19 is rigidly fixed to or integral with the first arm 11. A spring 18... Figure 2 The spring 18 is shown only schematically and is preferably composed of a helical or worm-like torsion spring, with one end connected to the first arm 11 and the other end connected to the working arm 17. In use, the working arm 17 is conveniently oriented such that the plane passing through axes B and D is substantially orthogonal to the load acting on the first pulley 13, in order to maximize the effect of the spring 18 and thus reduce its size.

[0035] The second pulley 14 is connected to the second arm 12 via a loading arm 20, which is rotatable relative to the arm 12 about a fourth axis E different from axis C; the second pulley 14 is rotatable relative to the loading arm 20 about axis C. Axes C and E are parallel to each other and parallel to axis A.

[0036] The loading arm 20 is kinematically defined by the distance d1 between axes C and E. The loading arm 20 is conveniently constructed via an eccentric device defined by a cylindrical pin having axis C, through which the second pulley 14 rotates about axis C by the insertion of a bearing (not shown). This eccentric device has an eccentric axial bore 21 having axis E, in which a locking screw 22 is received and screwed into the second arm 12. The loading arm 20 is used only to bring the belt 8 to nominal tension during installation, as will be better described below, and is then locked relative to the second arm 12 by means of the screw 22. Therefore, in use, the loading arm 20 is rigidly fixed to the second arm 12, and the second pulley 14 rotates about axis C, which is fixed relative to the second arm 12.

[0037] Conveniently, axis A is positioned within the path of belt 8 to minimize the length of arms 11 and 12 and thus their weight. Figure 2 In one embodiment, arms 11 and 12 together define a V-shaped structure that opens toward the first pulley 3.

[0038] Figure 3 A variant is shown in which the arms 11, 12 of the tensioner 10 together define a V-shaped structure that opens toward the second pulley 5.

[0039] The operation of tensioner 10 is as follows.

[0040] When mounted on engine 1, tensioner 10 is configured such that first pulley 13 is locked in a nominal position on first arm 11, for example by means of a conventional locking pin (not shown). Conveniently, the nominal position allows first pulley 13 to remain behind belt 8, i.e., out of the path of belt 8, so that belt can be installed.

[0041] At this stage, loosen screw 22.

[0042] Once the belt is installed, the loading arm 20 rotates about axis E, easily rotated using a dedicated wrench (with a wrench holder on the arm itself, not shown) to bring the belt 8 to the predetermined nominal tension. At this point, screw 22 is tightened, thus securing the loading arm 20 to the second arm 12. Finally, the working arm 17 is unlocked by pulling out the locking pin; the action of spring 18 causes the working arm 17 to rotate about axis D, thereby bringing the first pulley 13 into the mounting position.

[0043] In use, the tensioner 10 rotates freely about axis A under the resultant force exchanged between the pulleys 13 and 14 and the corresponding spans 15 and 16 of the belt. Specifically, during the transition where span 16 changes from tension to slack (and therefore span 15 changes from slack to tension), the tensioner 10 rotates clockwise about axis A, referencing... Figure 2As shown in the diagram; conversely, during the transition of span 15 from slack to taut (and thus span 16 from taut to slack), tensioner 10 rotates counterclockwise.

[0044] The load on pulley 13 or 14, which is matched with the tension span, is transmitted through two arms 11, 12 to the pulley acting on the slack span, thereby determining its tension.

[0045] Spring 18 acts on the working arm 17, giving the tensioner 10 a second degree of freedom (in addition to rotation about axis A); the elasticity of spring 18 allows tension peaks to be filtered out during transitions, thus reducing the average load acting on the tensioner itself. This reduces the weight of the tensioner, saving materials and cost. Since the B-axis is housed within pulley size 13, the working arm 17 can also be constructed with minimal material consumption and without introducing any additional space requirements.

[0046] exist Figure 2 and Figure 3 In the example shown, the two arms are slender elements that form a V-shaped structure; this configuration is not necessary and can be replaced by, for example, a triangular or curved structure. It should be understood that, from a kinematic point of view, this structure must define two arms.

[0047] Figure 4 Different embodiments of the tensioner 10 are shown below, and their relationship with [other components] is discussed below. Figure 2 and Figure 3 The differences in the implementation forms are described, and the same reference numerals are used to denote the parts that are the same as or correspond to the parts that have been described.

[0048] exist Figure 4 In the tensioner 10 (see enlarged detail view), the working arm 17 and the loading arm 20 are associated with the same pulley 13, which can be easily rotated on the arm 12 about an axis C that is fixed relative to the arm.

[0049] exist Figure 4 In the illustrative example shown, the two arms 17, 20 are defined by an eccentric device housed within each other. Specifically, the loading arm 20 comprises a cylindrical pin having an outer cylindrical surface with an axis D, an eccentric hole 21 through which a locking screw 22 with an axis E is mounted. The loading arm 20 is thus rotatable about axis E to change the position of axis D during installation and then locks in a position corresponding to the nominal belt tension 8.

[0050] The working arm 17 is conveniently constructed via a second eccentric device defined by a pin having an outer cylindrical surface with axis B, about which the first pulley 13 rotates. The second eccentric device has an eccentric axial bore with axis D, in which the loading pin 20 is received. The spring 18... Figure 4 The image is shown only schematically, and is preferably composed of a helical or worm-shaped torsion spring, with one end connected to the loading pin 20 and the other end connected to the working arm 17.

[0051] Figure 5 and Figure 6 An example of the working arm 17 and loading arm 20 combined together is shown.

[0052] The loading arm 20 is in the form of an elongated plate, contacting the end 23 of the arm 11 on one side of the pulley 13. The loading arm 20 is provided with a pin 27 having an axis D, which is received in a hole 24 in the arm 11 and a hole 28 having an axis E. The distance between the axis D and the axis E is equal to R, such that the hole 28 faces the groove 26.

[0053] Screw 27 is installed through slot 26 and hole 28 in arm 11, which engages with centering portion 29. Screw 27 is assembled such that head 30 axially abuts against arm 11 on the side opposite to pulley 13.

[0054] Screw 27 engages nut 31, on which spacer 32 is fitted to serve as a pivot for working arm 17. The latter is constituted by an eccentric device with an outer cylindrical surface having axis B, on which pulley 13 is mounted by means of bearing 33. Nut 31 has an end flange 34, which allows the spacer 32 to be axially blocked on the annular protrusion 35 of loading arm 20.

[0055] A helical torsion spring 18 is coaxial with the annular protrusion 35 and is arranged between the loading arm 20 and the working arm 17. One end of the helical torsion spring 18 is linked to the loading arm 20, and the other end is linked to the working arm 17 (not shown). The spring 18 serves a dual purpose: to apply torque to the working arm 17 to maintain contact between the pulley 13 and the belt 8, and to apply axial force to the working arm 17 to axially bias it against the end flange 34 of the nut screw 31, with a polymer ring 35 arranged between the two. The working arm 17 is radially supported on the spacer 32 by a polymer bushing 36. The materials of the ring 35 and the bushing 36 are chosen to achieve the desired damping of oscillations of the working arm 17.

[0056] Figure 5 and Figure 6 The operation of the tensioner in the middle is similar to Figure 4 During installation, nut 31 is loosened to allow loading arm 20 to rotate about axis D, and working arm 17 is conveniently locked relative to loading arm 20 by locking pin (not shown).

[0057] Once the nominal belt tension is reached, nut 31 is tightened onto screw 27, thereby locking loading arm 20 onto first arm 11 by friction. Once unlocked, working arm 17 is loaded by spring 18 to hold pulley 13 against belt 8.

[0058] The advantages provided by the present invention are obvious from the analysis of the tensioner according to the present invention.

[0059] In particular, the tensioner’s structural design can be optimized to reduce its weight and cost by using arms that are rigidly connected to each other and a loading arm that is contained within the overall size of one of the pulleys.

[0060] Finally, it is obvious that modifications and variations can be made to the described tensioner without departing from the scope of protection of this invention.

[0061] In particular, the technical solutions for the construction of the working arm and the loading arm may differ from the embodiments described.

[0062] In addition, refer to Figures 4 to 6 In this scheme, the working arm 17 and the loading arm 20 can be arranged between the second arm 12 and the second pulley 14, instead of between the first arm 11 and the first pulley 13.

[0063] Figure 2 and Figure 3 The solution can also be reversed, linking the working arm 17 to the second arm 12 and the loading arm 20 to the first arm 11.

[0064] Therefore, the terms “first arm,” “second arm,” “first pulley,” and “second pulley” in the claims are used only to distinguish one arm from another, and one pulley from another, and are not limited to the specific construction described; these terms are interchangeable and may refer to each of the arms and pulleys.

[0065] Finally, the common axis of rotation of the arms can be outside the belt path, rather than inside.

Claims

1. A double-arm tensioner for an accessory drive (2) of an internal combustion engine (1), comprising: The first arm (11) and the second arm (12) are rigidly connected to each other and can rotate about a common axis of rotation (A); The first pulley (13) is pivotally connected to the first arm (11) and is rotatable about the first axis (B); The second pulley (14) is pivotally connected to the second arm (12) and is capable of rotating about the second axis (C); A working arm (17) is hinged to the first arm (11) about a third axis (D) different from the first axis (B), and the first pulley (13) is carried by the working arm (17); and An elastic element (18) is configured to apply a spring force to the working arm (17) that tends to bring the first pulley (13) closer to the second pulley (14). The third axis (D) is located within the contour of the first pulley (13). The tensioner includes a loading arm (20) pivotally connected to one of the first arm (11) and the second arm (12), the loading arm (20) being rotatable relative to the first arm (11) or the second arm (12) about a fourth axis (E) different from the first axis (B) or correspondingly different from the second axis (C), the fourth axis (E) being within the profile of the first pulley (13) or correspondingly within the profile of the second pulley (14).

2. The tensioner according to claim 1, wherein, The working arm (17) includes an eccentric device.

3. The tensioner according to claim 2, wherein, The eccentric device is defined by a pin having an outer cylindrical surface whose axis coincides with the first axis (B), and the eccentric device is provided with an eccentric axial hole whose axis coincides with the third axis (D), and the axial hole engages with a pin (19) carried by the first arm (11).

4. The tensioner according to claim 1, wherein, The loading arm (20) includes an eccentric device.

5. The tensioner according to claim 1, wherein, The loading arm (20) is supported by the second arm (12).

6. The tensioner according to claim 1, wherein, The loading arm (20) is supported by the first arm (11).

7. The tensioner according to claim 6, wherein, The working arm (17) is supported by the loading arm (20).

8. The tensioner according to claim 7, wherein, The loading arm (20) and the working arm (17) consist of two eccentric devices that accommodate each other.

9. The tensioner according to claim 1, wherein, The first arm (11) and the second arm (12) form a V-shaped structure.

10. An accessory drive for an internal combustion engine, comprising: A first pulley (3), a second pulley (5), and a belt (8), wherein the first pulley (3) is connected to the drive shaft of an internal combustion engine, the second pulley (5) is connected to the shaft (6) of an electric motor, and the belt (8) cooperates with the first pulley (3) and the second pulley (5), characterized in that the accessory drive includes a tensioner (10) as described in any one of claims 1-9 above.

11. The accessory driver according to claim 10, wherein, The common axis of rotation (A) of the first arm (11) and the second arm (12) is inside the path of the belt (8).

12. The accessory driver according to claim 10, wherein, The common axis of rotation (A) of the first arm (11) and the second arm (12) is outside the path of the belt (8).

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