Phase-shifting drive device with return spring for internal combustion engine camshaft

Abstract

A drive device with phase shift for a camshaft of a motor vehicle internal combustion engine, comprising a drive pinion surrounding a ring having internal cavities, a camshaft mounting hub having bosses on its contour fitted into the cavities, separating chambers of a rotary actuator, a transverse plate (12) connected to the ring, closing one side of the cavities with its front face, a spiral return spring (20) disposed on the rear face of the plate (12), and axial pins (14, 16, 26) for guiding the spring (20) and driving its ends (22, 24), the plate (12) having pins (14, 18, 26) that are formed directly from the same material. Figure 3

Description

Title of the invention: PHASE-SHIFTING DRIVE DEVICE WITH RETURN SPRING FOR SHAFT A THERMAL ENGINE CAMS

[0001] The present invention relates to a device for driving a camshaft of a thermal engine by a pinion, comprising a phase shift system equipped with a return spring, as well as a thermal engine and a motor vehicle comprising this drive device.

[0002] A type of thermal engine camshaft drive device, presented in particular by document US-A1-2015075461, comprises a pinion receiving a chain driven by the crankshaft of the engine, fixed to a crown comprising two internal cavities which extend peripherally.

[0003] Each cavity receives a boss arranged on the contour of a hub fixed at the end of the camshaft, with a seal which separates in the peripheral direction, on each side of this boss, a chamber receiving pressurized oil.

[0004] By supplying the two bosses to the two chambers on the same side, a rotary cylinder is thus formed which allows the angular position of the pinion to be shifted in phase with respect to the camshaft. By applying oil pressure to the two chambers on the other side, a double-acting rotary cylinder is obtained which allows the pinion to return to its original position.

[0005] As a variant, known camshaft drive devices comprise a spring arranged in a spiral in the plane of the pinion, which, by bearing on the hub, applies a permanent rotational torque to the crown to obtain its return to the original position. It is thus possible to simplify the control of the device by using a single-acting rotary cylinder comprising a single oil inlet applying pressure in the direction of the phase shift, the return being effected by the effect of the spring.

[0006] In this case it is known to close the chambers by a transverse plate receiving the spring on its opposite face, and to arrange parallel to the axis of rotation pins inserted in holes in the hub and the plate in order to guide the spring, and drive its ends which applies the return torque.

[0007] However, in this case, several axial holes must be made on the hub and the plate, then the tightened pins must be inserted inside, which must have guarantees of resistance over time to withstand the alternating bending forces applied to them. This type of assembly poses problems of complexity in machining the parts, which must have precise adjustments to obtain sufficient tightening, and of difficult assembly of the pins, which results in long operating times and high costs.

[0008] The present invention aims in particular to avoid these problems of the prior art.

[0009] To this end, it proposes a device for driving with phase shift a camshaft of a motor vehicle thermal engine, comprising a drive pinion surrounding a crown having internal cavities, a hub for fixing on the camshaft having on its contour bosses fitted in the cavities, separating chambers of a rotary jack, a transverse plate linked to the crown, closing by a front face one side of the cavities, a spiral return spring arranged on the rear face of the plate, and axial pins for guiding the spring and driving its ends, this device being remarkable in that the plate comprises pins which are formed directly in the same material.

[0010] An advantage of this drive device is that with the plate produced directly with its axial pins formed with the same material, a single part is obtained which can combine the functions of guiding and driving one end of the spring. This avoids the machining of several holes, and the complexity of assembling several pins which must withstand alternating bending forces. Assembly times are reduced, and the costs of purchasing and managing different pins to be assembled are avoided, which reduces the cost price of the device.

[0011] The training device according to the invention may further comprise one or more of the following features, which may be combined with each other.

[0012] Advantageously, the plate comprises a drive pin for the radially outer end of the spring.

[0013] In this case, advantageously the drive pin comprises an end shoulder for axially holding the spring.

[0014] Advantageously, the plate comprises spring guide pins which are smooth.

[0015] Advantageously, the plate comprises a central drilling comprising internal bosses receiving guide pins.

[0016] In particular, the plate may comprise two internal bosses each receiving a guide pin.

[0017] Advantageously, the hub comprises an axial pin for fixing the inner end of the spring which is formed directly in the same material.

[0018] Advantageously, the axial pins are formed from a blank of the plate or hub produced by forging a metallic material.

[0019] The invention also relates to a thermal engine equipped with a camshaft, remarkable in that it comprises a drive device comprising any one of the preceding characteristics, which is fixed at the end of this camshaft.

[0020] The invention further relates to a motor vehicle comprising a heat engine, remarkable in that this engine is equipped with a drive device comprising any of the preceding features, which is fixed to the end of a camshaft.

[0021] The invention will be better understood and other characteristics and advantages will appear more clearly on reading the description given below by way of example, with reference to the appended drawings in which:

[0022] [Fig-1] is a view of a drive device according to the prior art, without the spring

[0023] [Fig.2] is a detail view of this drive device including the spring; and

[0024] [Fig.3] is a view of the plate with the spring of a drive device according to the invention.

[0025] Figures 1 and 2 show a drive device 2 comprising a pinion 4 for receiving the movement coming from the crankshaft of the thermal engine, surrounding a crown 6 receiving inside a hub 8 which is fixed by screws engaged in holes 10 on the end of a camshaft not shown, arranged along an axis of rotation A. The camshaft is arranged axially on a front side AV of the drive device 2.

[0026] The hub 8 has on its contour bosses fitted in interior cavities of the crown 6, with a seal, to form at least on the same side of the bosses a chamber receiving pressurized oil in order to apply a rotational torque between this crown and the camshaft which gives a phase shift of the angular position of the pinion 4.

[0027] A circular plate 12 arranged transversely is fixed by its front face on the crown 6 to close the cavities arranged in this crown.

[0028] The plate 12 comprises on its rear face a spirally wound spring 20, of square section, comprising a radially outer end forming an outer loop 22 wound around an axial outer end pin 14 which is crimped into a bore in this plate. The outer end pin 14 comprises an end shoulder axially holding the outer loop of the spring 22.

[0029] The inner end of the spring 20 also comprises an inner loop 24 which is wound around a groove of an inner end axial pin 16 which is crimped into a bore of the hub 8, the groove ensuring the axial retention of this end.

[0030] An external axial guide pin 18 fixed on the plate 12 near the outer end of the spring 22, provides guidance inside the first outer turn of this spring. Two internal axial guide pins 26 fixed on the hub 8, at the edge of the circular central bore 28 of the plate 12, provide internal guidance of the inner turn of the spring 20.

[0031] An elastic connection is obtained between the plate 12 and the hub 8 by the spring 20, which ensures a permanent return torque of one element relative to the other allowing to form a single-acting rotary cylinder inside the drive device. Guidance and centering of the inner coil of the spring 20 are also obtained by the inner end pin 16 and by the two inner guide pins 26, and guidance of its last outer coil by the outer guide pin 18.

[0032] With this drive device according to the prior art 2, it is necessary to provide five axial drillings on the plate 12 and the hub 8 made with precision to reliably crimp the five pins 14, 16, 18, 26, which represents delicate operations requiring a particular adjustment to obtain a strong hold. With these drilling operations, the supply of the pins 14, 16, 18, 26, and their assembly, significant operating times and high costs are obtained.

[0033] [Fig. 3] shows the plate 12 of a drive device according to the invention, comprising in a single piece, formed with the same material, the external end pin 14 comprising its shoulder, and the external guide pin 18.

[0034] The central bore 28 of the plate 12 comprises two inwardly facing bosses 30, each receiving an internal guide pin 26 which is formed from the same material as the plate.

[0035] In particular, the plate can be produced by forging a metallic material making it possible to produce the internal bosses 30, and the blanks of the pins 14, 18, 26 which are then machined to complete the profile of these pins.

[0036] In a similar manner the internal end pin 16 can be formed directly in the material of the hub 8.

[0037] The precise machining of the holes to receive pins 14, 16, 18, 26, the supply of these pins and their assembly are avoided. In addition, a high resistance of the pins is ensured, which are not likely to become dislodged.

Claims

Claims

1. A drive device with phase shift for a camshaft of a motor vehicle thermal engine, comprising a drive pinion (4) surrounding a crown (6) having internal cavities, a hub (8) for fixing to the camshaft having on its contour bosses fitted into the cavities, separating chambers of a rotary cylinder, a transverse plate (12) connected to the crown (8), closing by a front face one side of the cavities, a return spiral spring (20) arranged on the rear face of the plate (12), and axial pins (14, 16, 18, 26) for guiding the spring (20) and driving its ends (22, 24), characterized in that the plate (12) comprises pins (14, 18, 26) which are formed directly from the same material.

2. Drive device according to claim 1, characterized in that the plate (12) comprises a drive pin (14) of the radially outer end (22) of the spring (20).

3. Drive device according to claim 2, characterized in that the drive pin (14) has an end shoulder for axially holding the spring (20).

4. A drive device according to any preceding claim, characterized in that the plate (12) has spring guide pins (18, 26) which are smooth.

5. A drive device according to any one of the preceding claims, characterized in that the plate (12) has a central bore (28) comprising internal bosses (30) receiving guide pins (26).

6. Drive device according to claim 5, characterized in that the plate (12) comprises two internal bosses (30) each receiving a guide pin (26).

7. A drive device according to any one of the preceding claims, characterized in that the hub (8) comprises an axial pin (16) for fixing the inner end of the spring (24) which is formed directly from the same material.

8. A drive device according to any one of the preceding claims, characterized in that the axial pins (14, 16, 18, 26) are formed from a blank of the plate (12) or the hub (8) made by forging a metallic material.

9. Thermal engine equipped with a camshaft, characterized in that it comprises a drive device (2) according to any one of the preceding claims, which is fixed at the end of this camshaft.

10. Motor vehicle comprising a heat engine, characterized in that this engine is equipped with a drive device (2) according to any one of claims 1 to 8, which is fixed at the end of a camshaft.

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