BACKGROUND OF THE INVENTION The present invention generally relates to automotive accessories driving systems

Conventionally, accessory apparatus such as the air conditioning (A/C) compressor unit, the alternator, cooling water circulation pump, power steering hydraulic pump, etc , are directly coupled to the engine crankshaft, via one or more belt-drive transmissions (usually the fan-belt) As a result, these apparatus seldom run in their optimal efficiency range Hence, over- cooling by the A/C unit is experienced during prolong highway cruising speed, whereas poor cooling is attained in idling engine speed - when it is most needed (e g stuck under the blazing sun in a traffic jam) In order to remedy this inherent drawback of the conventional systems, it has already been suggested to incorporate an automatic, constant speed output transmission system, designed to gradually increase the accessories driving speed in idling or low-gear speeds, and decrease the high-gear speed — see U S Patent No 2,720,087 (Groene), proposing a variable transmission device associated with the engine crankshaft

This improvement has, however, certain disadvantages First, the system was applicable only as an OEM product, namely, that it had to be integrated into the automobile production line; secondly, extra space had to be allotted within the engine compartment, and then, due to its complexity and sensitivity would have been quite expensive in production and requiring special care and maintenance The implementation has therefore failed

Particularly concerning the A/C compressor unit working characteristics, it has been ascertained that for average practical purposes, the demand for a truly constant speed transmission need not to be satisfied, but rather be

effectively compromised by using only a single-stage, step-up transmission for the low speed engine operation - cf Fig 5 of the attached drawings

It has been further noted, that compressors of most brands presently marketed (the "wobbling disc" type) are, so to speak, "indifferent" in as much as rotation direction of their driving shaft is concerned In other words, reversal of directions will not damage or otherwise affect the operation of the compressors The same applies to alternators and certain brands of hydraulic pumps, however, the invention will be described and exemplified with particular reference to car air-conditioners where its advantages are most strikingly manifested

It is therefore the general object of the invention to provide an automotive accessory driving system that will overcome the above listed and other deficiencies of the known systems It is a further object of the invention to provide a transmission system which is integratable with the automotive accessory apparatus, as an "after market" item, namely being self-containing in production, neat, compact and easily installable in existing cars

It is still further object of the present invention that the transmission device will constitute a single engine speed, automatically controlled gears arrangement, with direction reversal output

It is a still further object of the invention to employ a planetary gear system in the transmission device, using friction clutches, which can be actuate either electrically or pneumatically

SUMMARY OF THE INVENTION

There is thus provided according to a broad aspect of the invention an automotive accessory driving system comprising means for coupling the

accessory to the automotive engine, means for sensing the engine speed, selectively engagable transmission means for stepping-up the operational speed of the accessory, means for enabling said transmission means upon sensing by the sensing means a reduction of the engine speed below a first pre-set value, and means for disabling the transmission means upon sensing by said sensing means an increase of the engine speed above a second pre¬ set value.

BRIEF DESCRIPTION OF THE DRAWINGS

These and additional aspects, objects, advantages and constructional features of the invention will be more clearly understood in the light of the ensuing description of preferred embodiments of the invention, given by way of example only with reference to the accompanying drawings, wherein- Fig. 1 is a general, schematic perspective view of a typical motor car engine block with several automotive accessories installed thereon;

Fig. 2 is a cross-sectional view of a transmission device for an A/C compressor unit according to a first preferred embodiment of the invention;

Fig. 3 is a section taken along line Ill-Ill of Fig. 2; Fig. 4 is a section taken along line IV-IV of Fig. 2;

Fig. 5 is a diagram of the transmission system operation;

Fig. 6 is a cross-sectional view relating to a second embodiment of the invention;

Fig. 7 is a section taken along line VII-VII of Fig. 6; and Figs. 8 - 10 are schematic representations of the neutral, direct coupling and over-drive stages of the system of Fig. 6, respectively.

Fig 11 is a sectional view of a further embodiment of the invention taken along line ll-ll of Fig 12,

Fig 12 is a section taken along line XI-XI of Fig 11 , and

Figs 13a-13b are schematic representations of the three modes of operation of the system of Figs 11 and 12

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to Fig 1 , there is shown how the main (crankshaft) driving pulley 10 of the engine 12 is couple by belt (or belts) 14 to - among other accessories of the motor car such as alternator 15 - to air-conditioning compressor unit generally designated 16 The compressor 16 is composed of compressor casing 18 and pulley unit 20

Pulley unit 20 is more-or-less of the conventional size and dimensions - although it comprises a planetary gears transmission system; this unique fact is emphasized, since it satisfies the strict space saving requirement governing the design of motorcars in general, and motor engine compartments - in particular

In more detail, as illustrated in Figs 2-4, pulley wheel 22 is freely rotatable about driving axle 24 by ball-bearings 26

Further comprised is a friction disc-type clutches, effective to engage the pulley wheel 22 to friction surface 30a of planetary gear housing 30 (details of the electric current supply for actuating to the clutch 28, and related construction, have been omitted for sake of clarity and as being of any conventional design)

Gear system housing 30 comprises internal gear crown 32 (constituting the "annulus" of the planetary system as will be explained below), and is rotatably supported on the one hand by axle 24 via a unidirectional roller

clutch 34, and on the other hand by ball bearing 38 placed between flange 30a and portion 36a of compressor casing cover plate 36

The planetary gear system comprises four (or any other suitable number) of "planet" or "satellite" gears 40, 41 , 42 and 43, and "sun" gear 44

The planets 40-43 are coupled to each other via a toroidal cage member 46 by means of axle pins 40a, 41a, 42a and 43a passing through the respective gears 40-43, each provided with a roller bearing (40b, 41b, 42b, 43b) for free rotation thereabout The cage member 46 is rotatable about a hub-like portion 36b of the casing cover 36 by bearing 48

The sun gear 44 is dπvingly coupled to the axle 24 by key 50

A second electromagnetic friction clutch 54 is provided, operatively associated with the cage 46, to selectively lock it against any rotation by engagement thereof to the (fixed) compressor casing cover 36

The operation of the transmission system 20 will now be described As readily understood from the foregoing descπption, there are available three modes of operation

A - none of clutches 28 and 54 are energized (the "neutral" position), B - only clutch 28 is activated ( the "direct coupling" position), and

C - both clutches 28 and 54 are activated (the "over-drive" position)

Let us first assume that the free-wheeling, unlocked direction of the one¬ way roller clutch 34 is opposite to the rotational direction of the pulley 22 by engine 12 (i e as driven by the belt 14) In the neutral position (A), the pulley 22 merely rotates, which represents the disengaged or OFF position of the A/C system

Upon actuation of the first clutch 28 and the engagement of the pulley 22 to the casing 30, the one-way clutch 34 becomes instantaneously locked against the compressor driving axle 24. The axle 24 is therefore rotated at the same speed, i.e. at a transmission ratio of 1:1. Since the sun gear 44 is keyed to the axle 24, it will also become driven by the same speed. The planets 40-43 will not spin about their axes, but are freely rotatable along with the cage 46 orbiting around the sun gear 44.

Hence, no change of transmission ratio is contributed by the planetary system as such. This mode of operation (B) is suitable for high speed, highway cruising velocities.

For lower driving speeds and especially idling, mode (C) is used, namely wherein the cage arresting friction clutch 54 is also operated. To this end, any known type of converter means, such as a manifold vacuum responsive switch, tachometer switch, and the like, can be employed, which will become triggered upon dropping of the crankshaft revolutions below a pre-set value.

Once locked against orbital movement, the planets 40-43 will positively transfer the rotation of the annulus 32 to the sun gear 44, however, at higher ratio [depending of the number of annulus teeth ( = pitch) divided by the pitch of the sun gear], and in a direction opposite to that of the pulley wheel 22 (and the casing 30).

Due to the change of directions, one-way clutch 34 will become unlocked (free-wheeling), and thus not interfere with the casing 30 (and the pulley wheel 22) continuing rotation in their former, normal direction.

The practical transmission ratio is about 2.0-2.5:1 , taking into consideration the dimensions of standard A/C units (mainly the compressor housing diameter and the pulley wheel diameter)

Since the normal idling speed of most cars is 900-1000 rpm, and assuming a ratio of about 1:1 between the crankshaft 10 (Fig. 1) and the pulley wheel 22 - the compressor speed will be about 2000-2500 rpm, namely quite-close to the optimum working conditions.

Upon accelerating the motor up to a pre-set rpm of the crankshaft, the transmission will become switched back to the "direct coupling" position thereof (B), together with direction reversal of the axle 24, and so forth.

Fig. 5 is self-explanatory in view of the foregoing description, clearly showing that the working range of the compressor is always kept above the selected minimum of 2000 rpm ~ rather than dropping to the actual idling speed of 900 rpm.

It will be readily appreciate that the transmission unit 20 is of an extremely simple and compact design; it's installation - whether originally (O.E.M.) or as an "after market" product (converting conventional A/C units in existing vehicles) - does not upset the layout and space requisites of the engine compartment.

Furthermore, compressors of smaller ratings can be used, with an entailed saving on fuel consumption, yielding however the same results in terms of efficiency and passengers' comfort.

Reference shall now be made to the embodiment of Figs. 6 -10, wherein similar reference numerals have been used to denote analogous parts and components. As readily noted, the A/C transmission system 120 of Fig. 6 differs from that of Fig. 2 mainly in that the pulley wheel 122 is integrated with the casing 130. An additional planets cage 146' for the planets 140-143 is provided (mirror image of cage 146) rotatable on bearing 148'. The cage 146' is adapted to be arrested against the casing 130 by a second electromagnetic friction clutch 154'.

No one-way clutch is included, as will become clear from the following explanation (see also Figs. 8 - 10).

In "Mode A" operation, clutches 154 and 154' are de-energized, and casing 130, with annulus gear 132 are rotated by the engine's belt (not shown).

As a result of compressor axle 124 being slightly loaded (by friction and certain back-pressure of the compressor), the planets 140 - 143 will tend to idly orbit about the sun gear 144, namely not transmitting any rotational movement thereto.

A "neutral" mode of operation is thus gained. The "direct coupling", highway cruising, 1 . 1 ratio mode of operation ("B") is attained by energizing only clutch 154'. Cage 146' will become gripped by the casing 130 and positively driven therewith. The free-wheeling orbital rotation of the planets 140-143 will change into unified movement, whereby the planets do not spin, but are held fixed against both the annulus 132 and the sun gear 144, and therefor function to relay the rotation from the former to the latter.

The sun gear 144, being directly coupled to axle 124, will thus drive the compressor by the same speed, i.e. that of the pulley 122. Switching to the over-drive, step-up transmission mode of operation is now attained by disengaging clutch 154' and engaging the second clutch 154. This will start the spinning of the planets 140-143 over their respective axles 140a-143a and transmit the revolutions of the annulus 132, multiplied by the applicable ratio factor (2.0 to 2.5 -- see above), to the sun gear 144, again in the opposite direction - as described in connection with the former embodiment; the operational characteristics represented in Fig. 5 apply as well to this embodiment.

In order not to cause possible shocks by the abrupt reversal of directions, the switching-over from the "high gear" to the "low gear" positions,

and vice-versa, should be cushioned or absorbed, e.g. by allowing a certain time lag between the release and the actuation of clutches 154 and 154' (or 28 and 54) sufficient for the moving parts to come to a standstill. Turning now to the third embodiment of the invention, the system 220 of Figs. 11 and 12 is similar to that of Fig. 6 of the Parent Application, but pneumatically controlled - rather than electrically.

Essentially comprised are compressor axle 224 and pulley wheel 222 integrally formed with casing 230, and annulus 232 meshed with four planets 240 - 243 freely rotatable about their respective axle pins 240a - 243a. The pin axles are carried by (unified) cage member 246. Sun gear 244 is mounted to the compressor axle 224 (key 250) and meshes with all four planets 240 - 243.

The transmission casing 230 is rotatable about a front, roller bearing 226 and rear, needle bearing 238. Bearing 238 is mounted around a stationary cylinder or flange 260, affixed to the compressor housing wall 236.

A pair of pneumatic (or hydraulic — see below) plungers are displaceably accommodated within the cylinder 260 : Rear plunger 262 (with gaskets 262a and 262b), and front plunger 264 (with gaskets 264a and 264b). The plungers 262, 264 are both of annular shape, situated one within the other as shown, but independently movable, the first under pressure supplied through conduit 266, and the second - by pressure admitted via conduit 268 and extension passage 268a leading to gap 268b left between the upstream side of the plunger 262 and the downstream side of the plunger 264. Movement of the front plunger 264 is relayed to friction discs clutch 254' by a series of four pins 270, abutting against the plunger 262 intermediate a thrust needle bearing 272, and against the bias of compression coil springs 274. The discs of the clutch 254 are, alternately, coupled to the cage 246 and to flange 260 affixed to housing wall 236.

Friction clutch 254 is operable by the circular rib 264a of the front plunger 264, against compression coil spring 276, to arrest and immobilize the cage 246. The alternate actuation of the clutches 254 and 254' is attained by applying pressure/relief commands through the conduits 268, 266 - as represented by the arrows depicted in Fig. 1 , and will be more clearly understood consulting the schematic representation of figs 13a - 13c, readily verifying that the operation of the transmission system 220 is identical to the electro-magnetic clutches version 120 according to Figs. 6 and 7.

The pneumatic version presents, however, two major and unique advantages: saving of the electrical energy demanded for the actuation and maintaining the grip of the magnetic clutches; and, should the vehicles not be already equipped with a pressurized air source (e.g. air-breaks as in most trucks and busses) -- the air conditioner compressor proper can fulfill, in addition, the function of supplying pressurized fluid (the cooling gas -- in this context) to the respective plungers in the requested manner (Fig. 3). Alternatively, the system can be operated hydraulically, either by the existing equipment of the respective vehicle, or by an auxiliary system. In all other respects, the system is comparable and analogous to that of the preceding embodiment.

While the invention has been described with specific reference to A/C systems, it will be readily understood that it applies also to other automotive accessories where the change of the main driving axle direction does not alter the operational performance, e.g. alternators. Those skilled in the art will readily appreciate that numerous changes, modifications and variations are applicable to the invention as herein exemplified without departing from its scope as defined in and by the appended claims.

Thus, for example transmissions other than planetary may be employed, comprising more than one-e.g. two or three-stages, confined in a unified casing and being exchangeable with or mountable to the A/C (or other accessory device) housing