GB2156016A

GB2156016A - Epicyclic reduction gear with an electromagnetic clutch

Info

Publication number: GB2156016A
Application number: GB08506358A
Authority: GB
Inventors: Yasuo Shimizu
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1984-03-12
Filing date: 1985-03-12
Publication date: 1985-10-02
Also published as: DE3508808A1; GB8506358D0; DE3508808C2; GB2156016B; JPS60192154A; CA1252648A

Abstract

A speed change mechanism for operating auxiliary equipment of an automotive engine at different speeds relative to the engine speed, in which an epicyclic gear train 30 is interposed between an input rotary member 5b and an output rotary member 6e, a warp spring 21 is wound around both said rotary members, and rotation being transferred from said input rotary member to said output rotary member either by a direct-coupled transmission through the wrap spring when tightened or by a change-speed transmission through said epicyclic gear train when the lap spring is loosened. An electromagnetic clutch 40 is operative to tighten and loosen the lap spring in response to a controller sensing a predetermined engine parameter. <IMAGE>

Description

SPECIFICATION Speed change gear mechanism for driving auxiliary equipment This invention relates to a speed change gear mechanism, particularly for use in driving auxiliary automotive equipment at different speeds relative to engine speed.

Auxiliary machinery on an automotive engine, such as for example an alternator, a compressor for the air conditioning system, or a power steering pump, are normally driven by a direct drive transmission means from an end portion of the engine crankshaft, usually through pulleys and belts. Therefore, the auxiliary machinery is always driven at a rotational speed proportional to the running speed of the engine. However, most auxiliary machinery does not require to run at a rotational speed above a given level and therefore in the high-speed operation of the engine it is desirable that excessive rotation of the auxiliary machinery be avoided by a speed change gear, thereby to reduce the fuel consumption of the engine, improve the durability of the auxiliary machinery, decrease noise, and to allow a reduction in the size and weight of the auxiliary machinery.

A speed change gear mechanism for this purpose has already been proposed by the present application in Japanese Published Patent Application No. 1 77727 published on 1 8th October 1 983. However, that speed change gear mechanism comprises a system wherein the operation of a lap spring for causing engagement and disengagement of an input rotary member and an output rotary member, for either direct coupling or speed change, is controlled by a mechanical centrifugal clutch. As a result, the input rotational speed at which engagement or disengagement of the clutch occurs is a fixed predetermined value, and therefore the rotational speed for operation of the reduction transmission cannot be changed, for example in accordance with the running state of the engine.

Although a mechanical centrifugal clutch is advantageous in durability as compared with an electromagnetic clutch, it is inferior to an electromagnetic clutch in response efficiency at the time of engagement or disengagement.

Viewed from one aspect the present invention provides a speed change mechanism for driving auxiliary equipment from an engine, including a reduction gear train arranged to be connected or disconnected by a clutch, operating means controllable from externally of the clutch for causing selective engagement and disengagment of the clutch, and control means responsive to at least one predetermined parameter for causing operation of said operating means.

Viewed from another aspect of the present invention provides a speed change mechanism comprising a epicyclic gear train interposed between an input rotary member and an output rotary member, a lap spring wound around both said rotary members for rotation to be selectively transferred from said input rotary member to said output rotary member either by direct-coupled transmission through the lap spring when tightened or by a changespeed transmission through said epicyclic gear train when the lap spring is loosened, an electromagnetic clutch operatively connected to the lap spring, and control means for controlling the electromagnetic clutch for selectively tightening or loosening the lap spring at a predetermined input rotational speed established according to at least one predetermined parameter.

Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 is a sectional elevational view of a first embodiment of a speed change mechanism according to this invention, taken on the central axis of the mechanism; Figure 2 is a sectional view similar to Fig. 1 and showing a second embodiment of the invention; and Figures 3 to 10 are diagrammatic illustrations of various embodiments of the invention, Figs. 3 and 4 being representative of the embodiments of Figs. 1 and 2 respectively, and Figs. 5 to 10 representative of six further embodiments.

Referring to Fig. 1, a speed change gear mechanism generally designated T is fixed on an end portion of a crankshaft 2 of an engine 1 with a bolt 4 through a key 3, and a planetary or epicyclic gear train 30 and an electromagnetic clutch 40 are provided between an input shaft 5 on the input side of the speed change gear mechanism and a pulley case 6 on the output side.

The epicyclic gear train 30 comprises a ring gear 31 consisting of an internal gear formed on the inside of the outer perimeter of a flange 5a fixed on the input shaft 5, a plurality of planet gears 32 (normally three) engaging therewith, a carrier 33 journaling the planet gears 32 rotatably and also rotatable itself, and a non-rotatable sun gear 34 located centrally to engage the planet gears 32.

The pulley case 6 on the output side has a plurality of pulleys 6b, on each of which an auxiliary machine driving belt is wound, the pulleys being formed on the circumference of a bowl-like body 6a. A central boss of the pulley case is journaled on an end portion of the input shaft 5 in both fluid-tight and rotational relationship through an oil seal 7 and a bearing 8. The epicyclic gear train 30 is enclosed within the pulley case 6. A rear cover 6', comprising an annular back plate Sc and the annular rotor 41 of the electromagnetic clutch 40, joined together solidly at the outer perimeter, is clamped on the rearward open face of the pulley case 6, on the engine side, by bolts 9.

A hollow fixed shaft 10 is supported on the input shaft 5 through an oil seal 11 and a bearing 1 2. The fixed shaft 10 is supported and prevented from rotating by a bracket 15 mounted on the case 1 a of the engine 1 by means of a bolt 14, through a buffer 13 made of rubber or the like. The inner perimeter of the back plate 6c is supported on the outer perimeter of the fixed shaft 10 by an oil seal 16 and a bearing 17. The back plate 6c has an axially extending flange 6d extending to the flange 5a of the input shaft 5, on its outer perimeter. A conventional type of oneway clutch 18 is fitted between the inner perimeter of the flange 6d and the planet gear carrier 33.

A hollow shaft portion 34a of the sun gear 34 is loosely fitted on the outer perimeter of the input shaft 5, with a suitable gap left therebetween, and its end portion on the engine side is coupled to an end portion of the fixed shaft 10 opposite thereto through an Oldham type coupling 1 9.

The electromagnetic clutch 40 comprises an annular solenoid 42 enclosed in a case 42a which is fixed on the bracket 15, an annular rotor 41, and an annular armature 43 disposed opposite the solenoid coil 42 and on the other side of the rotor 41. A circular-arc slit 41b is provided in the rotor 41, and a non-magnetic material 20 such as rubber copper alloy, aluminum alloy or the like is fitted fluid-tightly in the slit 41 b. The armature 43 is mounted on the end portion of a thin platelike spring case 23 which in turn is mounted on the flange 5a of the input shaft 5. The case 23 surrounds a lap spring 21 the function of which is described hereinafter. The case 23 prevents the lap spring 21 from springing outward as a result of centrifugal force, and holds the armature 43 at a suitable gap from the rotor 41. Further, the case 23 has a multitude of through holes 23a disposed irregularly.Any metallic powder present in the lubricating oil for the epicyclic gear train 30 in the pulley case 6 is discharged from the epicyclic gear train by way of the through holes 23a as a result of the centrifugal force, but is prevented from re-entering the area of the epicyclic gear train by the wall of the case 23 between the through holes 23a.

An input side drum face 5b and an output side drum face 6e are formed in approximately the same circumferential plane on flange 5a of the input shaft 5 and flange 6d of the back plate 6c, respectively, and the multiplex winding of lap spring 21, which may be either rectangular or circular in section, is positioned to extend over and cover both of the drum faces 5b, 6e. An input side end portion 21a of the lap spring 21 is fixedly mounted in an engaging groove formed on the outer perimeter of the flange 5a of the input shaft 5, and an output side end portion 21 b is fixedly mounted on the armature of the electromagnetic clutch 40. The tightening direction of the lap spring 21 coincides with a rotating direction of the flange 5a.

A timing belt 26 is wound on a pulley 25 mounted on the crankshaft 2 of the engine 1.

An electrical power supply 45, such as a battery, is connected to the solenoid coil 42 through a current carrying switch 44, and the switch 44 is controlled by a controlled signal from an electronic controller 46. When the speed change gear mechanism is used to operate the auxiliary machinery of an engine, the electronic controller 46 outputs an ON signal to energize the solenoid coil 42 when the engine running speed is at or below a predetermined value.

The manner of operation of the above described first embodiment of the invention now will be described.

First, in an operating condition in which the rotational speed of the crankshaft 2 of the engine 1 is at a predetermined value or below, the controller 46 closes the current carrying switch 44 to energise the solenoid coil 42 to thereby close the magnetic circuit connecting the case 42a of the solenoid coil 42, the rotor 41 and the armature 43, as indicated by the irregular circle of arrows in the lower portion of Fig. 1, on the electromagnetic clutch 40. Thus the armature 43 is attracted to the solenoid coil 42 to engage the rotor 41 on the output side with a predetermined binding force, thereby causing the lap spring 21 to be wound up by the turning force of the input shaft 5 and to contract in diameter, thereby to tighten down onto the drum faces 5b and 6e and thus to connect and unite the said drum faces.Accordingly, the input shaft 5 on the input side and the pulleys 6b on the output side rotate together to consitutute a one-to-one direct-coupled transmission system. The planet gears 32 rotate on their axes and revolve around the sun gear 34 in accordance with the rotation of the ring gear 31.

This causes a reduction in the speed of rotation of the carrier 33 to less than that of the input shaft 5 and the pulley case 6, the difference in speed of rotation being accom modated by the idling of the one-way clutch 18.

Next, in an operating condition where the rotational speed of the crankshaft 2 of the engine 1 exceeds the aforementioned predetermined value, the controller 46 opens the current carrying switch 44 to deenergise the solenoid coil 42, whereby the armature 43 and the rotor 41 are disengaged from each other. Consequently, the lap spring 21 loosens by reason of its own recoil strength and centrifugal force, to release its binding engagement with the drum faces 5b and 6e. Once again, the planet gears 32 rotate on their axes and revolve around the sun gear 34 according to the speed of rotation of the ring gear 31 which rotates together with the input shaft 5.This results in a reduction in the speed of rotation of the carrier 33, which is transferred to the pulley case 6 through the rear cover 6' by way of the one-way clutch 1 8. Thus, a reduction transmission system is provided for reducing the speed of rotation of the pulley case 6 at the predetermined reduction gear ratio of the epicyclic gear train 30 relative to the speed of rotation of the crankshaft 2 of the engine 1.

In the second embodiment illustrated in Fig.

2, the annular armature 43 of an electromagnetic clutch 40' is L-shaped in section. The input side end portion 21a of the lap spring 21 is bent radially outward and coupled to an end portion of an axial flange 43a of the armature 43, whilst the output side end portion 21b of the spring is bent radially inward and fixed in an engaging groove formed on the carrier 33, which functions also as a back plate. The armature 43 has its radial flange 43b urged toward the flange 5a of the input shaft 5 by an annular spring 44 interposed between it and the armature rotor 41, thereby pressing the input side end portion 21a of the lap spring 21 onto the flange 5a at all times.

The carrier 33 of the epicyclic gear train 30 is formed as part of, or joined to, plate 6c, and hence is rotatable together with the rotor 41.

The one-way clutch 1 8 is fitted between the sun gear 34 and its shaft 34a and permits the sun gear 34 to rotate relative to the fixed shaft 10 only in the same direction as the ring gear 31. Other than this, the construction of this second embodiment is the same as the first embodiment.

Although not specifically illustrated in Fig.

2, electrical components corresponding to the current carrying switch 44, the power supply 45, and the controller 46 in Fig. 1 are also provided in this second embodiment.

In the operation of this embodiment, in an operating condition where the rotational speed of the engine 1 is at a predetermined value or below, contrary to the first embodiment, the controller does not supply current to the solenoid coil 42, but rather the armature 43 is pressed against the flange 5a of the input shaft 5 by the spring 44 to engage therewith, the lap spring 21 is thereby tightened by the rotation of the input shaft 5, and therefore the input side drum face 5b and the output side drum face 6e are joined together to constitute a direct-coupled tranmission system.As a result, the ring gear 31, the carrier 33 and the rotor 41 rotate together, whereby the planet gears 32 and the sun gear 34 would be locked to rotate together with the ring gear, but free rotation of the sun gear 34 is accommodated by idling of the one-way clutch 1 8 between the sun gear 34 and the shaft 34a.

In an operating condition of the embodiment of Fig. 2 where the rotational speed of the engine exceeds the said predetermined value, a current is supplied to the solenoid coil 42, and the armature 43 is thereby attracted towards the rotor 41 by the solenoid coil 42 in opposition to the force of the spring 44, thereby becoming concurrently disengaged from the flange 5a of the input shaft 5 and engaged with the rotor 41, whereby the lap spring 21 is loosened to disconnect the input side drum face 5b from the output side drum face 6e. Consequently, the planet gears 32 rotate on their axes and also revolve in the same direction as the ring gear 31 rotating together with the input shaft 5.Since this rotating motion urges the sun gear to rotate counter to the ringe gear 31, the one-way clutch is engaged, and the speed of rotation of the carrier 33 and the rotor 41 is reduced in line with the intrinsic reduction gear ratio of the epicyclic gear, thus constituting a reduction transmission system.

Figs. 3 to 10 represent various embodiments of the invention in block diagram form for ease of understanding of various modifications and combinations that may be used, and for clarity and comparison like reference characters represent like parts in all the embodiments.

Fig. 5 shows a third embodiment in which the arrangement of the epicyclic gear train 30 and the one-way clutch 1 8 is the same as in the first embodiment, but the operation of the electromagnetic clutch and the lap spring is the same as in the second embodiment.

Fig. 6 shows a fourth embodiment in which the arrangement of the epicyclic gear train 30 and the one-way clutch 1 8 is the same as in the second embodiment, but the operation of the electromagnetic clutch and the lap spring is the same as in the first embodiment.

Fig. 7 shows a fifth embodiment in which the ring gear 31 of the epicyclic gear train 30 is on the fixed side, the carrier 33 is disposed on the output side, and the sun gear 34 on the input side, the one-way clutch 1 8 being disposed between the carrier 33 and the output. The electromagnetic clutch is of the same construction as in the first embodiment.

Fig. 8 shows a sixth embodiment in which the ring gear 31 is on the output side, the carrier 33 is on the fixed side, the sun gear 34 is on the input side, and the one-way clutch 1 8 is disposed between the ring gear 31 and the output. The planet gear system 32 comprises two idle gears engaging with each other. The electromagnetic clutch is of the same construction as in the first embodiment.

Fig. 9 shows a seventh embodiment in which the ring gear 31 is on the fixed side, the carrier 33 is on the output side, the sun gear 34 is on the input side, and the one-way clutch 1 8 is disposed between the ring gear 31 and the fixed side. The electromagnetic clutch is of the same construction as the second embodiment.

Fig. 10 shows an eighth embodiment in which the ring gear 31 is on the output side, the carrier 33 is on the fixed side, the sun gear 34 is on the input side, and the one-way clutch 18 is disposed between the carrier 33 and the fixed side. As in the case of the sixth embodiment, the planet gear system 32 comprises two idle gears engaging with each other. The electromagnetic clutch is of the same construction as in the second embodiment.

As in the case of the relation between the first embodiment and the third embodiment and also the relation between the second embodiment and the fourth embodiment, a speed change operation by controlling the current supplied to the electromagnetic clutch can be reversed in the fifth and sixth embodiments in which the electromagnetic clutch 40 is of the same construction as in the first embodiment, and also in the seventh and eighth embodiments in which the electromagnetic clutch 40' is of the same construction as in the second embodiment, by having such electromagnetic clutch replaced by the electromagnetic clutches 40' and 40 shown in the second embodiment and the first embodiment.

As described above, in these embodiments of the invention, the tightening and loosening of the lap spring is effected by the electromagnetic clutch, whereby increased efficiency is achieved in the engagement or disengagement of the clutch as compared with a conventional mechanical centrifugal clutch. Further, the electromagnetic clutch controls tightening and loosening of the lap spring at a selected input rotational speed established according to a predetermined parameter, such as engine rotational speed or the like, by means of the controller. Therefore a value of the input rotational speed can be set electrically with ease, with no replacement being required for either the electromagnetic clutch itself or the parts thereof, unlike the mechanical centrifugal clutch which requires replacement of parts such as flyweight, spring or the like.As a result an improved matching of the engine and auxiliary machinery is facilitated.

Further, by using an electromagnetic clutch to control the tightening and loosening of the lap spring, the wrapping boosting effect of the lap spring reduces the required binding force of the clutch, and therefore a small electromotive force is sufficient to operate the electromagnetic clutch, whereby the solenoid coil of the electromagnetic clutch can be reduced in size and weight, and only a small current is required for operation, thereby reducing energy losses.

It is to be clearly understood that there are no particular features of the foregoing specification, or of any claims appended hereto, which are at present regarded as being essential to the performance of the present invention, and that any one or more of such features or combinations thereof may therefore be included in, added to, omitted from or deleted from any of such claims if and when amended during the prosecution of this application or in the filing or prosecution of any divisional application based thereon.

Claims

1. A speed change mechanism for driving auxiliary equipment from an engine, including a reduction gear train arranged to be connected or disconnected by a clutch, operating means controllable from externally of the clutch for causing selective engagement and disengagement of the clutch, and control means responsive to at least one predetermined parameter for causing operation of said operating means.

2. A mechanism as claimed in claim 1, wherein said operating means includes electromagnetic clutch means and said control means is arranged to selectively supply electrical current thereto for causing engagement and disengagement.

3. A speed change mechanism comprising an epicyclic gear train interposed between an input rotary member and an output rotary member, a lap spring wound around both said rotary members for rotation to be selectively transferred from said input rotary member to said output rotary member either by directcoupled trnnsmission through the lap spring when tightened or by a change-speed transmission through said epicyclic gear train when the lap spring is loosened, an electromagnetic clutch operatively connected to the lap spring, and control means for controlling the electromagnetic clutch for selectively tightening or loosening the lap spring at a predetermined input rotational speed established according to at least one predetermined parameter.

4. A mechanism as claimed in claim 3, wherein said electromagnetic clutch comprises a solenoid coil fixed on static member, a rotor opposite to the solenoid coil, and an armature opposite to the rotor and engaging with one end of said lap spring, said input rotary member including said rotor, and said output rotary member including said armature.

5. A mechanism as claimed in claim 3 or 4, wherein said epicyclic gear train comprises a ring gear rotatable together with said input rotary member, a sun gear fixed on a static member, a planet gear engaging the ring gear and the sun gear, and a carrier holding the planet gear and rotatable together with said output rotary member, said lap spring being arranged to tighten on said ring gear and said carrier concurrently for connecting said in response to the operating state of said electro magnetic clutch.

6. Speed change mechanism substantially as hereinbefore described with reference to the accompanying drawings.