Pulley unit for a motor vehicle engine

Abstract

A pulley unit includes a hub configured to be connected to a crankshaft; a pulley coaxial with the hub and supported in a free rotation manner with respect to the hub; a clutch interposed between the hub and the pulley; and an actuator for controlling the clutch. The clutch includes an inner disc rotationally coupled to the hub and having an engagement portion housed inside the pulley; a moving member axially movable between an engagement position, in which the moving member rotationally couples the pulley to the engagement portion of the inner disc, and a disengagement position, in which the pulley is free to rotate with respect to the inner disc; and an elastic element acting on the moving member to push the moving member toward the engagement position.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102020000002686, filed on February 11, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a pulley unit for motor vehicles, and more specifically, to a pulley unit including separable pulleys. Background Technology

[0004] As is well known, motor vehicle engines are typically equipped with belt-driven accessory gearboxes, which include pulleys associated with the crankshaft and multiple pulleys associated with corresponding engine accessories (e.g., motors and compressors for vehicle air conditioning systems).

[0005] In modern engines, the electric motor is often reversible, operating as either a generator (alternator) or an engine depending on the operating conditions. Specifically, when operating as an engine, the electric motor can provide torque other than that of the internal combustion engine, or provide a substitute torque for the internal combustion engine.

[0006] In hybrid applications, or even in conventional applications with start-stop functionality, there is a problem of driving the air conditioning compressor when the internal combustion engine is off. This requires an electric motor to operate the accessory transmission and disconnect the crankshaft from the relevant pulleys.

[0007] Therefore, a pulley unit is known to include a hub configured to be fixed to the crankshaft, pulleys, and a clutch inserted between the hub and pulleys, typically driven by an electromagnetic actuator. The clutch is generally friction-type.

[0008] Friction clutches are known to have some drawbacks.

[0009] The transmittable torque depends on the actuation load, friction surfaces, and diameter. Therefore, to reduce the clutch size, the actuator size must be increased, and vice versa. Consequently, in terms of overall dimensions, it is difficult to find an acceptable compromise among these variables, especially when applied in existing engines and thus subject to predetermined space constraints.

[0010] To address the issue of overall size, clutches with front teeth are typically used, which enable high power transmission within a relatively compact overall size. However, the use of clutches with front teeth is also undesirable due to the high noise levels they generate. Summary of the Invention

[0011] The purpose of this invention is to produce a pulley unit that solves or improves the problems associated with known pulley units.

[0012] The above objective is achieved by a pulley unit comprising:

[0013] A wheel hub configured to be connected to the crankshaft of a motor vehicle and having an axle;

[0014] A pulley that is coaxial with the hub and supported in a manner that allows it to rotate freely relative to the hub;

[0015] The clutch, which is inserted between the hub and the pulley; and

[0016] An actuator that controls the clutch.

[0017] The clutch includes an inner plate and a moving member. The inner plate is rotatably connected to a hub and has a engagement portion housed within a pulley. The moving member is axially movable between an engaged position and a disengaged position. In the engaged position, the moving member rotatably connects the pulley to the engagement portion of the inner plate. In the disengaged position, the pulley rotates freely relative to the inner plate.

[0018] Since the inner plate's engagement portion is housed within the pulley, the additional overall dimensions determined by the presence of the clutch are minimized; therefore, the overall dimensions of the pulley unit can be equal to or slightly larger than the overall dimensions of a conventional pulley unit.

[0019] Furthermore, the radial overlap between the pulley and the inner disc allows for a quieter connection scheme than the front gear.

[0020] Preferably, the elastic element is subjected to a thrust from at least one elastic element toward the joint; thus, the actuator can be a single-acting type.

[0021] Alternatively, a bistable actuator can be used, in which case no elastic element is required.

[0022] According to one embodiment of the invention, the clutch includes a first tooth carried by a pulley and a second tooth carried by an inner disc, the second tooth defining the engagement portion; when arranged radially facing each other, the corresponding tooth gaps of the teeth together form an axial tooth seat, and a moving member carries an engagement element that mates with the tooth seat at the engagement position.

[0023] Preferably, the engaging element is permanently engaged with the tooth of one of the teeth so that the moving member is also rotatably integrated with one of the inner disc and the pulley in the disengaged position.

[0024] This helps to achieve synchronization on the channel between the disengagement and engagement positions.

[0025] According to another embodiment of the invention, the pulley unit includes a torsional vibration damper in which a clutch is integrated. Attached Figure Description

[0026] To better understand the present invention, preferred embodiments are described below by way of non-limiting examples and with reference to the accompanying drawings, wherein:

[0027] Figure 1 This is a partial axial cross-sectional view of the pulley unit according to the first embodiment of the present invention;

[0028] Figure 2 yes Figure 1 A segmented, exploded 3D view of the pulley unit;

[0029] Figure 3 Shown in segmented 3D diagrams and enlarged scale Figure 1 Components of the clutch in a pulley unit;

[0030] Figure 4 yes Figure 3 Partial cross-sectional view of the component;

[0031] Figure 5 yes Figure 1 variants of the unit and Figure 4 Similar partial cross-sectional views;

[0032] Figure 6 and Figure 7 This is a partial axial cross-sectional view of the second embodiment of the present invention at two different operating positions;

[0033] Figure 8 This is a partial axial cross-sectional view of the third embodiment of the present invention;

[0034] Figure 9 This is a partial axial cross-sectional view of the fourth embodiment of the present invention; and

[0035] Figure 10 yes Figure 9 Component diagram of the pulley unit. Detailed Implementation

[0036] refer to Figure 1 and Figure 2 The pulley unit for an internal combustion engine 2 (partially shown) used in a motor vehicle is generally indicated by reference numeral 1.

[0037] The pulley unit 1 includes a hub 3 configured to be fixed to a crankshaft 6 of an engine 2 by a plurality of screws 4; a pulley 7; and a clutch 8 for selectively engaging / disengaging the pulley 7 from the hub 3. The hub 3, pulley 7, and clutch 8 have a common axis A, which coincides with the axis of the crankshaft 6 during use.

[0038] The pulley 7 includes an annular tooth crown 9, which has a multi-groove profile 10 on the outside to mate with the multi-V belt (not shown) of the accessory transmission.

[0039] The clutch 8 includes an inner disc 12 and an outer ring 15. The inner disc 12 is fixed to the hub 3 by a plurality of screws 13 (the plurality of screws 13 are tightened together with the inner disc 12 and the torsional vibration damper 14, which is not part of the present invention); the outer ring 15 is supported relative to the inner disc 12 in an angularly free manner by bearings 16. The outer ring 15 is fixed to the tooth crown 9 of the pulley 7, for example, by force engagement.

[0040] The inner disc 12 has external teeth 18, which define a plurality of tooth gaps 19, the plurality of tooth gaps 19 having semi-circular profiles that are equidistant from each other at an angle. Figure 3 and Figure 4 ).

[0041] The outer ring 15 includes corresponding inner teeth 20, which define a plurality of semi-circular tooth gaps 21. The plurality of semi-circular tooth gaps 21 are equidistant from each other at an angle, and their number is even. They also have the same angular pitch as the tooth gaps 19 of the outer teeth 18 of the inner disc 12.

[0042] Therefore, when the inner disc 12 and the outer ring 15 are angularly synchronized, the tooth gaps 19 and 21 of the corresponding teeth face each other radially and together form a basically cylindrical tooth seat 22.

[0043] The clutch 8 also includes a main disc 23 fixed to the hub 3 (e.g. by force engagement) and a secondary disc 24 having an annular shape, the secondary disc 24 being axially inserted between the inner disc 12 and the outer ring 15 on one side and the main disc 23 on the other side.

[0044] A ring spring 25, such as a disc spring, diaphragm spring, or coil spring, is axially inserted between the main disc 23 and the secondary disc 24 to push the secondary disc axially toward the inner disc 12 and the outer ring 15. Conveniently, the spring 25 does not directly contact the secondary disc 24 to avoid slippage and wear during transition, but a thrust ring 32 is inserted between the secondary disc 24 and the spring itself.

[0045] Sub-board 24 ( Figure 3 and Figure 4 The outer ring 15 is axially slidably assembled onto the collar 33 via the bushing 34, the collar 33 being formed by the main disc 23. The secondary disc 24 carries a plurality of axial pins 26 spaced at an angle to each other, the number of axial pins 26 being the same as that of the gear seat 22, and generally engaging the gear seat in a gapped manner under the thrust of the spring 25, thereby keeping the outer ring 15 (and thus the pulley 7) rotatably connected to the inner disc 12 (and thus to the hub 3).

[0046] The pulley unit 1 finally includes an actuator 27 (e.g., an electromagnet) configured to overcome the action of the spring 25 and move the secondary disc 24 axially from the engagement position to the release position. In the release position, the pin 26 retracts from the tooth seat 22 and releases the inner disc 12 from the tooth crown 9 of the pulley 7.

[0047] Although the actuator is preferably electromagnetic, other types (such as hydraulic or pneumatic) may also be used.

[0048] In the example shown, the electromagnet 27 includes a coil 28 encapsulated in a fixed retainer 29 made of ferromagnetic material. Conveniently, the retainer 29 is fixed to the engine block by a special bracket (not shown) and supported relative to the main plate 23 by bearings 30. The retainer is closed at the front by the main plate 23, which is conveniently provided with a plurality of openings 17 (…). Figure 2 This is to ensure that the magnetic current generated by coil 28 is not shielded when energized. Coil 28 is provided with electrical terminals (not shown), which are configured to be connected to the vehicle's electrical system.

[0049] Pin 26 is conveniently provided with a convex or conical head 31, the diameter of which is conveniently smaller than the diameter of gear seat 22 by an amount sufficient to account for dimensional tolerances and position. Furthermore, to reduce noise during connection, backlashes 19, 21 may have a flared end 35 on the side facing the sub-disc 24. Figure 2 Alternatively, a flare can be provided on pin 26.

[0050] Similarly, in order to reduce the impact noise generated during engagement and when the transmission torque oscillates, pin 26 has a circumferential seat near sub-disc 24 for accommodating a corresponding resilient annular element 36, for example in the form of an O-ring made of resilient material.

[0051] Unit 1 is conveniently lubricated with grease. To retain the grease, a seal 37 is provided between the cage 29 and the pulley 7.

[0052] As can be partially seen from the above description, the operation of pulley unit 1 is as follows.

[0053] Without energizing coil 28, spring 25 holds the secondary disc 24 in an engaged position with the teeth 19, 21 and crown 9 of the inner disc 12. When coil 28 is energized, the secondary disc 24 of clutch 8 is axially attracted and released, in which pin 26 is withdrawn from the toothed seat 22 of pulley 7. In this position, even when crankshaft 6 is stationary, crown 9 is free relative to inner disc 12 and can rotate under the drive of accessory drive belt.

[0054] In this way, the air conditioning system compressor can be driven even when the internal combustion engine is off.

[0055] When coil 28 is de-energized, the thrust of spring 25 resets auxiliary disc 24 to the engaged position and reconnects pulley 7 to crankshaft. The flare 35 facilitates this connection and allows for engagement with substantially synchronized pulley and crankshaft operation, thus enabling proper control of the auxiliary transmission motor. The presence of the elastic annular element 36 further reduces the noise level of the connection.

[0056] Figure 5 A variant embodiment of pulley unit 1 is shown, wherein pin 26 is permanently engaged with teeth 18 of inner disc 12.

[0057] For this purpose, the tooth 18 and the head 31 of the pin have a greater axial extension, so that there is an engagement area even when the sub-disc 24 is in the release position.

[0058] In this way, only synchronization between the secondary ring 24 and the crown 9 is required in the channel from the release position to the engagement position, and the engagement operation becomes easier and quieter.

[0059] Figure 6 and Figure 7 A second embodiment of the present invention is shown, which is generally indicated by reference numeral 100. Only the parts that differ from unit 1 are described below. Parts that are equivalent to or correspond to those already described are indicated by the same reference numerals.

[0060] In this design, the main disc 23 is integrated with the pulley 7, rather than with the hub 3. Specifically, the main disc has an outer peripheral edge 101 and a tubular inner peripheral edge 102, wherein the outer peripheral edge 101 is fitted into the tooth crown 9, while the tubular inner peripheral edge 102 is coaxial with the hub 3; a seal 103 is inserted between the inner peripheral edge 102 and the hub 3.

[0061] Furthermore, in this configuration, the main disk 23 is provided with multiple openings 17, which are closed on the front by an annular plug 104 made of plastic material, so as to... Figure 1 The proposed design would not shield the magnetic current that recloses through the secondary ring 24.

[0062] However, in this case, according to and reference Figure 5 The scheme is similar to but opposite to the one described above, in which the secondary ring 24 is rotatably integrated with the pulley 7 through a permanent connection between the pin 26 and the internal teeth 20 of the outer ring 15.

[0063] Therefore, the magnetic circuit consists of a fixed part (the cage 29 of the coil 28) and a rotating part, the rotating part being formed by the main disk 23 and the secondary ring 24, and there is no contact between the actuator 27 and the secondary ring 24. Therefore, the transmission of the actuation load does not require the use of a bearing between the fixed and rotating parts.

[0064] In this configuration, the spring 25 is inserted between the secondary ring 24 and the plug 104, which are rotatably fixed to each other; thus, the spring 25 will not slip, thereby preventing wear.

[0065] The plug 104 has an annular protrusion 105, which is configured to be in a disengaged position of the sub-ring 24 due to the magnetic attraction of the coil 28. Figure 7 It is used in conjunction with pin 26 to attenuate actuation noise.

[0066] Figure 8 Another embodiment variation is shown, which is generally denoted by reference numeral 40. The following description focuses only on the parts that differ from the described unit 1. Parts that are equivalent to or correspond to those already described are denoted by the same reference numerals.

[0067] In unit 40, the sub-disc 24 is internally guided on the hub 3 via a grooved connector 41. Conveniently, the grooved connector is disposed between an outer annular element 42 and a washer 43, wherein the outer annular element 42 is fixed to the inner circumference of the sub-disc 24, while the washer 43 is force-fitted into the hub 3 and axially inserted between the shoulder of the hub and the bearing 30.

[0068] In the pulley unit 40, the spring 25 is composed of a helical spring, which is inserted between the main plate 23 and the cup-shaped part 44, which is assembled onto the auxiliary plate 24 by a riveting member 45.

[0069] The teeth 18 and 20 of the inner disc 12 and the outer ring 15 are further disposed on the corresponding rings 46 and 47, and can be conveniently pressed onto them by force engagement. The outer ring 15 has a C-shaped cross section and is internally supported on the inner disc 12 by a bushing 49 made of a plastic material with a low coefficient of friction.

[0070] Pin 26 is provided with a head 50 having a spherical front profile to facilitate engagement with teeth 18, 20.

[0071] Unit 40 is lubricated with grease. To prevent dirt from entering and to prevent grease leakage, gaskets 51 and 52 are provided between the outer ring 15 of the clutch 8 and the damper 14, and between the main plate 23 and the retaining plate 53 of the coil 28 to the engine block retainer 29.

[0072] The operation of unit 40 is similar to that of the described unit 1.

[0073] Figure 9 A third embodiment of the present invention is shown, which is generally indicated by reference numeral 60.

[0074] The pulley unit 60 includes a filter unit 61, which includes a drive member 62 having an inner disc 12 integrated with the hub 3 and an outer ring 63 provided with a plurality of radial spokes 64 (conveniently two). The filter unit 61 also includes an outer shell 65 formed by two half-shells, one half-shell consisting of a pulley 7 and the other half-shell consisting of a cover 66 forcefully fitted into the tooth crown 9 of the pulley.

[0075] The inner disk 12 and the outer ring 63 can be selectively connected to each other via a sliding toothed coupling 66, which is formed by the outer teeth 66 of the inner disk 12 and the inner teeth 67 of the outer ring 63. The outer ring 63... Figure 9 The device is movable between the shown engagement position and the unengaged position (not shown). A disc spring 69 is inserted between the outer ring 63 and the axial end wall 70 of the cover, such that the outer ring 63 normally abuts against the end stop 71 fixed to the pulley 7.

[0076] A circumferential arc spring 75 is arranged between the spokes 64 and the housing 65 (see also) Figure 10 For this purpose, the housing 65 forms a protrusion 76, thereby providing a shoulder for the spring. Conveniently, the spring 75 has an end received in the slider 77, which mates with the spokes 64 and the protrusion 76.

[0077] Based on the above description, the connection between the outer ring 63 and the pulley 7 is not rigid, but is provided by the spring 75.

[0078] Similar to the description of unit 1, pulley unit 60 includes an electromagnetic actuator 27, which is provided with a ring coil 28, which is arranged in a fixed position facing the outside of the wall 68 of the cover 65.

[0079] The wall 68 is provided with a plurality of openings 78, which are closed on the front by annular plugs 79 made of plastic material to prevent the magnetic current generated by the coil 28 from reclosing through the wall 68 and to allow the magnetic current to reach the outer ring 62 and reclosing through the outer ring.

[0080] Therefore, when the coil 28 is excited, the coil 28 overcomes the action of the spring 68 and attracts the outer ring 62 toward the wall 69, thereby separating the inner disk 12 from the outer ring 62.

[0081] Similarly, in this case, such as in Figure 6 and Figure 7 In this design, there is no contact between the fixed part and the rotating part of the magnetic circuit.

[0082] As can be partially seen from the above description, the operation of unit 60 is as follows.

[0083] Without energizing coil 28, spring 68 holds outer ring 63 in the engaged position. In this position, pulley 7 is rotatably connected to hub 3 via spring 75 of filter unit 70, which filters torsional vibrations of crankshaft.

[0084] When coil 28 is energized, the secondary disc 24 of clutch 8 is axially attracted and enters the released position. In this position, even if crankshaft 6 is stationary, the toothed crown 9 is free relative to the inner disc 12 and can rotate under the drive of the accessory drive belt.

[0085] Finally, it is obvious that modifications and changes can be made to the described pulley units 1, 100, 40, and 60 without departing from the scope defined by the claims. In particular, units 1 and 40 can be provided with a filter unit instead of the torsional vibration damper 14, just like unit 60.

Claims

1. A pulley unit, comprising: - a hub (3) configured to be connected to a crankshaft of a motor vehicle and having an axis (A); - a pulley (7) coaxial with the hub (3) and supported in a free-rotating manner with respect to the hub; - a clutch (8) interposed between the hub (3) and the pulley (7); and - an actuator (27) for controlling the clutch (8), wherein the clutch (8) comprises an inner disc (12) rotationally coupled to the hub (3) and having an engagement portion (18; 67) housed inside the pulley (7), and a mobile member (24, 63) axially movable between an engagement position, in which the pulley (7) is rotationally coupled to the engagement portion (18; 64) of the inner disc (12), and a disengagement position, in which the pulley (7) is free to rotate with respect to the inner disc (12), wherein the engagement portion comprises a tooth (18).

2. The unit of claim 1, wherein, - at least one elastic element (25) acting at least indirectly on the mobile member (24) to bias it towards the engagement position.

3. The unit of claim 1, wherein, - the clutch (8) comprises a first tooth (20) carried by the pulley (7) and a second tooth (18) carried by the inner disc (12), the second tooth (18) defining the engagement portion, respective tooth spaces (19, 21) of the teeth (18, 20) jointly forming an axial tooth seat (22) when arranged radially facing each other; the mobile member (24) carries an engagement element (26) cooperating with the tooth seat (22) in the engagement position.

4. The unit of claim 3, wherein, - the engagement element permanently cooperates with a tooth space (19, 20) of one of the teeth to rotationally fix the mobile member (24) to one of the inner disc (12) and the pulley (7) also in the disengagement position.

5. The unit of claim 3, wherein, - the tooth spaces (19, 21) have a substantially semicircular profile and the tooth seat (22) is cylindrical, and the engagement element is an axial pin (26) carried by the mobile member (24).

6. The unit of claim 3, wherein, - a guide element (35) is included to facilitate the engagement (8) of the engagement element (26) in the tooth seat (22).

7. The unit of claim 5, wherein, - an elastic element (36) is included interposed between the pin (26) and the respective tooth seat (22) in the engagement position.

8. The unit of claim 3, wherein, - the first tooth (20) is carried by an annular element (15; 47) internally coupled to the pulley (7).

9. The unit of claim 8, wherein, - the annular element is supported on the inner disc by a bearing or bushing.

10. The unit of claim 1, wherein, - the mobile member (24) is a disc coaxial with the hub (3).

11. The unit of claim 10, wherein, - the disc (24) is guided to slide on the hub (3) or on an additional disc (23) carried by the hub (3).

12. The unit of claim 1, wherein, - a filtering unit (61) is included configured to filter torsional vibrations.

13. The unit of claim 12, wherein, Said filtering unit (61) comprises a drive member (62) equipped with said inner disc (12) and a plurality of radial spokes (64) which can be coupled to said pulley (7) by means of a plurality of circumferential springs (75).

14. The unit of claim 13, wherein, Said spokes (64) are carried by an outer ring (63) separate from said inner disc (12) and which can be selectively coupled to said inner disc by means of said clutch (66).

15. The unit of claim 14, wherein, Said clutch (66) comprises a sliding toothed coupling between said inner disc (12) and said outer ring (63).

16. The unit of claim 15, wherein, Said outer ring (63) of said drive member (62) constitutes said mobile member.

17. The unit of claim 1, wherein, Said actuator comprises an electromagnet (27) housed in a fixed position and an armature rotating around said axis (A) of said hub (3).

18. The unit of claim 17, wherein, Said mobile member consists of said armature of said electromagnet (27).

19. The unit of claim 18, wherein, It comprises a member (76, 194) which is rigidly rotating with said pulley (7) and which is axially interposed between said electromagnet (27) and said mobile member.

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