WO2014167314A1

WO2014167314A1 - A gear box

Info

Publication number: WO2014167314A1
Application number: PCT/GB2014/051094
Authority: WO
Inventors: Neil John RAYNER; Steven John POOTE
Original assignee: Paratus Developments Limited
Priority date: 2013-04-08
Filing date: 2014-04-08
Publication date: 2014-10-16
Also published as: GB2514995A; GB201306279D0

Abstract

An efficient electronic gearbox is described suitable for use as: an automotive overdrive, a retrofitted automotive overdrive, a reverse gear, and useful in wind turbines and marine applications. The gearbox enables a direct drive coupling between an input shaft (2) and an output shaft (5) or shifting to drive through one or more gear trains to provide a mechanical advantage and/or reverse gear. When shifted to the direct drive mode the gear train (12, 13, 15, 16) is uncoupled from the drive input and output. Shifting is facilitated by synchromeshes (11, 19, 20) actuated by electronically controlled actuators which obviate mechanical linkages.

Description

A GEAR BOX

Technical field

[001] The present invention concerns a gear box which may be used in a range of mechanical power transmissions including, but not limited to; automotive, marine and wind turbine systems.

Prior art

[002] Figure 1 shows two views of a prior art gearbox from WO2007/028986 developed by the present inventor. The gear box has a power input shaft 101 and a collinearly aligned output shaft 102. A plurality of gears 103, 104, 105 and 106 arranged in a gear train and also capable of coupling the input and output shafts. A synchromesh self-shifting clutch 113 is operable to couple the input shaft 101 and a sliding gear 104. An electrical actuator 107 serves as a control to displace a piston 108 and the sliding gear 104 to actuate the self-shifting clutch. Actuating the self-shifting clutch causes the gear box to switch from a direct drive condition shown in the top view of figure 1 and indicated by the arrow D to an indirect drive condition shown in the bottom view and indicated by arrow D'. In the direct drive condition the input shaft 101 couples with the output shaft by means of a sleeve 9 which is axially displaceable by the piston 8 with respect to adjacent ends of the input and output shafts. Each circumferential surface of each respective end of the input shaft and output shaft is splined at 101 , 1 12 to cooperate with corresponding splines on the inner surface of the sleeve 109. A ratchet, pawl and clutch arrangement ensures the speeds of the input shaft 101and output shaft 102 match and the splines align before the input and output shafts are directly coupled by axial displacement of the sleeve 109.

[003] When the actuator 107 displaces the piston 108 to the right as in the lower

indirect drive view, sleeve 109 disengages the splines 11 1 of input shaft 101. The cylindrical gear 103 is coupled with the input shaft 101 and the sliding gear 104 couples with the output shaft via gear 106 and a clutch 110. The principle advantage of this arrangement is that the gears of the gear train are not driven to rotate when the input and output shafts are disengaged. In other conventional gear boxes the gears of the gear train are always driven in rotation thereby wasting power, increasing vibration, generating noise and causing wear.

[004] GB2473340 discloses a gear box generally similar to WO2007/028986 and also developed by the present inventor. In GB 2473340 a supplementary input shaft couples to the gearbox via an SSS clutch.

[005] In the gear boxes of WO2007/028986 and GB2473340 (the entire contents of each of WO2007/028986 and GB2473340 are incorporated herein by reference) at least the gear and meshed gear of the gear train are always driven to rotate with the output shaft.

[006] It is an object of the present invention to provide improvements to the previously described gear boxes, notably in at least one of: mechanical efficiency, weight, bulk, production costs and reliability.

Statement of invention

[007] According to a first aspect of the present invention there is provided a gearbox having an input shaft, an output shaft and a gear train to indirectly couple the output shaft to the input shaft wherein;

the gear train includes an input shaft gear mounted coaxially on the input shaft and meshing with an upstream gear of the gear train, and

an output shaft gear coaxially mounted on the output shaft and meshing with a downstream gear of the gear train, wherein each of the input gear and the output gear can be selectively coupled and uncoupled from the respective input and output shafts by a synchromesh.

[008] The input shaft gear is mounted onto the input shaft via a bearing to rotate freely.

Preferably the drive shaft acts as the hub of a synchromesh. A synchromesh is splined onto the drive shaft to be axially displaceable. The synchromesh supports axially extending teeth arranged to mesh with axially facing teeth on the input shaft gear when the synchromesh is displaced to an engaged condition whereby the input shaft gear is coupled to the input shaft. Reversing the displacement uncouples the input gear from the input shaft. A synchroniser ring may be provided to act between the slider teeth and the axial gear teeth to ensure synchronous meshing of the gears.

[009] The output shaft gear is mounted on the output shaft via a bearing to rotate freely relative to the output shaft. An output synchroniser is splined onto the output shaft to be axially displaceable. The output synchroniser is provided with axially facing teeth arranged to mesh with oppositely facing teeth on the output shaft gear when the slider is displaced axially towards the output shaft gear.

Synchronous meshing of the output shaft gear teeth and the output shaft slider teeth may be ensured by an output synchroniser ring. [010] When each of the input gear and output gear are uncoupled from the respective input and output shafts no energy is applied to keep the gears of the gear train spinning with a consequent potential reduction in energy use, bearing wear, tooth wear, vibration, heat and noise generation.

[01 1] According to a second aspect of the present invention there is provided a

gearbox having an input shaft and an output shaft, a shaft coupling mechanism to directly couple the output shaft to the input shaft, wherein; the shaft coupling mechanism comprises a synchromesh.

[012] Preferably adjacent ends of the input shaft and output shaft are collinearly

aligned. The shaft coupling mechanism may comprise a sleeve which is preferably permanently coupled to the input shaft end and axially displaceable. towards and away from the collinearly adjacent output shaft end. An axially fast synchromesh may be coupled to the output shaft end so that the displacement of the sleeve towards the output shaft end will cause the sleeve to couple with the synchromesh and hence the output shaft. In some applications the sleeve may be coupled permanently to the output shaft and the sleeve synchromesh mounted on the input shaft.

[013] According to a third aspect of the present invention there is provided a gearbox having an input shaft and an output shaft and a gear train to indirectly couple the output shaft to the input shaft wherein;

the gear train includes an input shaft gear mounted coaxially on the input shaft and meshing with an upstream first gear of the gear train, and

an output shaft gear coaxially mounted on the output shaft and meshing with a downstream output gear of the gear train, wherein each of the input gear and the output gear can be selectively coupled and uncoupled from the respective input and output shafts by a synchromesh; and

a shaft coupling mechanism to directly couple and uncouple the output shaft to the input shaft, wherein; the shaft coupling mechanism comprises a synchromesh.

[014] Preferably each or any of the synchromeshes may be actuated by one or more electronically controlled actuator motors. This facilitates retrofitting the gearbox as an overdrive or reverse gear by avoiding the need for mechanical linkages. The actuators may be controlled by a manual switch or actuated by a robot controller or remote control.

Brief description of drawings

[015] Embodiments of a gear box constructed in accordance with the present invention will now be described, by way of example only, with reference to the

accompanying illustrative figures, in which:

figure 2A is a diagram of a gear box in direct drive mode;

figure 2B is a diagram of a gear box in an intermediate condition;

figure 2C is a diagram of the gear box in an overdrive mode;

figure 3 is a plan view of the gear box implemented in a wind turbine;

figure 4 is a plan view of the gear box of figure 3 with the casing removed;

figure 5 is a left side elevation of the gear box of figure 4;

figure 6 is a perspective view of the gear box of figures 4 and 5 from above and the rear; and figure 7 is a bottom view of the gear box of figures 3 to 6 with a sleeve and synchroniser selector fork omitted.

Detailed description of the drawings

[016] Figure 3 shows a wind turbine assembly comprising a turbine 1 mounted to rotate a turbine driven input shaft 2 which drives through a gearbox 3 to drive a generator 4 via an output shaft 5. The gear box 3 comprises a casing 6 which encases a gear assembly illustrated diagrammatically in figures 2A and 2B and in detail in figures 4 to 7.

[017] The input shaft 2 is coaxial and collinear with the output shaft 5 and separated by a small gap 7 so that the input shaft and output shaft can be decoupled to spin around their axis at different speeds. A sleeve 8 is mounted onto the end of the input shaft 2. The sleeve 8 is irrotatably coupled to the end of the input shaft 2 by means of splines 9. The splines 9 extend from the end of the input shaft 2 adjacent the output shaft 5 to allow the sleeve 8 to be displaced axially. The Sleeve 8 includes a radially extending part 8a adapted to engage the splines and a sleeve part 8b which extends axially towards the output shaft 5. When in the direct drive mode shown in figure 2A, the sleeve 8 is displaced towards the output of the gear box so that the sleeve portion 8b bridges the gap 7. The sleeve portion 8b includes an annular recess which accommodates a rotary sleeve bearing 10 mounted onto the adjacent end of the output shaft 5. In this direct drive mode an axial face of the sleeve portion 8b engages a sleeve synchroniser 1 1. The sleeve synchroniser 11 is mounted onto output shaft splines 5a extending from the end adjacent the input shaft. The sleeve synchroniser 1 1 is made axially fast by conventional means such as a key or circlip or engagement with a feature such as a shoulder provided on the output shaft 5. In this direct drive mode torque applied by the turbine to the input shaft 2 is transmitted as indicated by the arrow D through the sleeve 8 and input shaft synchroniser 1 1 to the output shaft 5 without any gearing.

[018] The gearbox of figures 2A and 2B includes a gear train comprising an input gear provided by first gear 12, meshed with a second gear 13. Second gear 13 is coupled via a lay or secondary shaft 14 to a third gear 15. Third gear 15 is meshed with an output gear provided by a fourth gear 16 mounted around the output shaft 5. The first gear 12 is mounted by means of a first gear bearing 17 for rotation about the input shaft 2. Fourth gear 16 is mounted for rotation around the output shaft 5 by means of a bearing 18.

[019] A first gear synchroniser 19 is mounted around a portion of the input shaft 2

immediately downstream (towards the output shaft) of the first gear 12. The first gear synchroniser 19 is rotationally coupled to the input shaft by engagement with the input shaft splines 9. In the direct drive mode shown in figure 2A the first gear synchroniser 19 is displaced downstream so that the first gear 12 is uncoupled from the input shaft 2.

[020] A fourth gear synchroniser 20 is mounted downstream of the fourth gear 16. The fourth gear synchroniser 20 is coupled to the output shaft by engagement with the output shaft splines 5a. As shown in figure 2A the fourth gear synchroniser 20 is displaced axially downstream of the fourth gear 16 to uncouple the fourth gear from the output shaft 5. Thus as shown in figure 2A little or no torque is transmitted to the gear train from the input or output shafts. [021] The gearbox shown provides an overdrive gear with a higher output speed than input speed. To select the overdrive gear the sleeve 8 is displaced axially upstream, i.e. towards the turbine. By displacing the sleeve 8 towards the turbine the sleeve 8 is disengaged from the sleeve synchroniser 11 and the input and output shafts are uncoupled.

[022] As the sleeve 8 is further displaced upstream it engages the first gear

synchroniser 19 and displaces the first gear synchroniser towards the first gear 12. The first gear synchroniser will spin the first gear 12 up to match the input shaft speed and in the process will apply torque to the gear train coupled with the first gear 12. The gear box is now in an intermediate condition shown in figure 2B.

[023] The fourth gear synchroniser 20 is displaced upstream after the intermediate condition to engage the fourth gear 16, As the fourth gear synchroniser engages the fourth gear 16 the output shaft 5 is spun up to the match the rotational speed of the fourth gear 16 and the overdrive mode of the gearbox is achieved as shown in figure 2C.

[024] The process is reversed to shift from the overdrive mode to the direct drive mode, the fourth gear synchroniser is disengaged from the fourth gear by axial displacement downstream. The sleeve 8 is then displaced axially downstream to uncouple the first gear 12 from the input shaft. Further displacement of the sleeve 8 downstream towards the output shaft causes the sleeve to engage the sleeve synchromesh 1 1. Sleeve synchromesh 1 1 will match the input and output shaft speeds and directly couple the input and output shafts. [025] Figures 3 to 7 show the gearbox 2 in greater detail. Figure 3 shows a wind turbine 21 , coupled to a turbine shaft 22. The turbine shaft 22 can be braked by a disc brake 24 and is supported by a turbine shaft bearing 25. The turbine shaft 22 is coupled to an intermediate shaft 23a by means of a flange 23 to drive through the gearbox in housing 26 to a generator 27. Electrically powered actuators 28, 29 and 30 are mounted on the housing cover 26.

[026] The intermediate shaft 23a is coupled to the input shaft 2 via a clutch

mechanism. Any clutch mechanism may be used but in this embodiment the clutch mechanism is provided by a slide pawl set and internal spur gear 31. A slide pawl set actuator 28 forms part of a slide pawl actuator assembly including an actuator member 28a which transmits a linear motion of the actuator 28 to a slide pawl assembly 31a. The axial displacement of the slide pawl assembly couples and uncouples the intermediate shaft 23a with the input shaft 2. This particular type of slide pawl clutch addresses a problem particular to a wind turbine. Wind speed is rarely constant. The generator and gear box assembly has substantial inertia. If the wind turbine slows suddenly as a result of a drop in wind speed the lack of a pawl clutch between the turbine and gear box would result in undesirable energy transfer from the gear box and generator assembly to the turbine. The pawl clutch ensures that energy can Only be transmitted from the turbine to the gear box and generator assembly.

[027] The pawl clutch assembly 31 is mounted inside the gear box casing and is

integral with the gear box. At least where the gear box is installed in a wind turbine application this reduces the steps to assemble the turbine. [028] The pawl clutch assembly 31 also provides a neutral condition.

[029] Input shaft 2 runs through the first gear bearing 17 which supports the first gear 12. As can be seen diagrammatically in figures 2A to 2C the region of the input shaft from the first gear bearing 17 to an upstream end has splines 9.

[030] The first gear synchroniser 19 is shown in figures 3 to 7 in the direct drive mode with synchroniser dog teeth 19a disengaged from first gear dog teeth 12a.

[031] The sleeve 8 is mounted onto the splines 9 upstream of the first gear

synchroniser 19. The sleeve 8 is engaged by a sleeve actuator assembly 30a which is linearly displaceable in the axial direction by the operation of the actuator 30. Thus the sleeve 8 can be displaced axially as previously described.

[032] The output shaft 5 is collinear with the end of the input shaft 2 and encircled by the sleeve bearing 10 at the upstream end. To maintain the alignment of the tubular input and output shafts the sleeve portion 8b of the sleeve 8 encircles the sleeve bearing 10.

[033] Splines 5a are formed onto the upstream end of the output shaft 5 and extend downstream as shown in figure 7. The sleeve synchroniser 11 is received onto the output shaft 5 to engage the splines 5a. The sleeve synchroniser 11 is made axially fast to the output shaft 5 by conventional means not shown. Such axial fastening means may include one or more circlips received into an annular groove in the shaft, and/or a shoulder formed on the output shaft 5. Similar conventional axial fastening means may be used as required to make any of the components of the gear box axially fast where required. The sleeve synchroniser 11 bears dog teeth 34 which face upstream to mesh with axially extending dog teeth 35 borne on an axially downstream face of the sleeve 8 when the sleeve 8 is displaced downstream to engage the direct drive mode.

[034] The fourth gear 16 is mounted downstream of the sleeve synchroniser 1 1 and is freely rotatable on the fourth gear bearing 18 when in the direct drive mode. The fourth gear synchroniser 20 is mounted on the output shaft 5 downstream of the fourth gear 16 and engages the output shaft splines 5a. The fourth gear synchroniser 20 is mounted to be axially displaceable by the operation of the fourth gear synchroniser actuator 29 which is arranged to linearly displace a fourth gear actuator assembly 29a.

[035] When the fourth gear actuator 29 urges the fourth gear synchroniser towards the fourth gear 16 dog teeth 36 extending upstream from the fourth gear

synchroniser 20 synchronise and mesh with dog teeth 37 projecting downstream from the downstream face of the fourth gear to couple the fourth gear to the output shaft 5.

[036] The gearbox has been described with reference to use in a wind turbine and has only one indirect drive gear train. However, as has previously been described in figure 4 of the applicant's earlier filed application, the principles of this gearbox can be applied by the skilled person to provide additional gear trains for multiple different gear ratios, including, or alternatively, a reverse gear ratio.

Claims

1. A gearbox having an input shaft and an output shaft and a gear train to indirectly couple the output shaft to the input shaft wherein;

the gear train includes an input shaft gear mounted to rotate freely on the input shaft and meshing with an upstream gear of the gear train, and

an output shaft gear mounted to rotate freely on the output shaft and meshing with a downstream gear of the gear train, wherein the input shaft gear can be selectively coupled and uncoupled from the input shaft by means of an input shaft gear synchromesh and

the output gear can be selectively coupled and uncoupled from the output shaft by an output gear synchromesh; and

a shaft coupling mechanism to directly couple and uncouple the output shaft to the input shaft, wherein; the shaft coupling mechanism comprises a shaft coupling synchromesh.

2. A gearbox according to claim 1 wherein

the shaft coupling mechanism comprises a sleeve displaceable in the direction of the shaft axis to engage and disengage the shaft coupling synchromesh.

3. A gearbox according to claim 2 wherein the input shaft gear synchromesh is displaced to couple and uncouple the input gear by displacement of the sleeve.

4. A gearbox according to claim 3 wherein the displacement of the sleeve is displacement to disengage the shaft coupling synchromesh.

5. A gearbox according to any of claims 2 to 4 wherein the sleeve is displaceable by means of a sleeve actuator.

6. A gearbox according to any one of claims 2 to 5 wherein the output gear synchromesh is displaced by an output gear actuator to couple and uncouple the output gear.

7. A gearbox according to any one of claims 2 to 6 wherein the sleeve is irrotatably coupled to one of the input or output shafts and encircles a rotary sleeve bearing mounted on the other of the input or output shaft to maintain the alignment of the input and output shafts.

8. A gearbox according to any one of the preceding claims wherein the output gear synchromesh is controlled to couple the output gear subsequent to coupling of the input gear.

9. A gearbox according to claim 8 wherein the output gear synchromesh is controlled to uncouple the output gear before the input gear is uncoupled.

10. A gearbox according to any one of the preceding claims having a pawl clutch mounted in casing of the gearbox to selectively couple and uncouple the input shaft with a drive shaft.

11. A gearbox according to claim 1 and as herein described with reference to the accompanying illustrative figures.