From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Detailed description of a change-over coupling mechanism and synchronizing brake for a multi-speed gearbox.
Identifier | ExFiles\Box 136\4\ scan0194 | |
Date | 22th December 1934 guessed | |
2 wheel e₁ being mounted so as to be capable of turning loosely between the shafts a and b with respect to these shafts and the toothed wheel f₁ being mounted loosely on the Cardan shaft b while the toothed wheels e₂ and f₂ are fixed on the lay shaft like the toothed wheel d₂. All these toothed wheels are preferably provided with inclined teeth so as to render them noiseless. Between the toothed wheels d₁ and e₁ and capable of being alternately coupled with them is a change-over coupling g which is slidable on the engine coupling shaft. A further change-over coupling h is provided between the toothed wheels e₁ and f₁, so as to be capable of being coupled with them. This coupling is mounted on the Cardan shaft so as to be capable of sliding thereon but not of turning. It is made in the form of a sleeve and is provided with keyways for one or more sliding wheels such as i₁ which can be brought into engagement with the corresponding toothed wheel or wheels i₂ of the lay shaft. For operating the change-over coupling g, the mechanism shown in Fig. 4 is provided. The dogs of the coupling g are inclined or bevelled at their ends in a similar manner to the dogs of the couplings described in Specification No. 298,186. For changing the speeds, for instance three selector bars are provided which are operated from a common operative lever k and of which one (k₁) acts on the toothed wheel i₁, a second one (k₂) acts on the change-over coupling h, as will be more particularly described hereinafter, and a third one (k₃) acts on the mechanism for shifting the sleeve g.{Mr Griffiths - Chief Accountant / Mr Gnapp} In addition a further suitable selector bar can be provided for the reverse. The selector bar k₂ acts by way of a lever l, and a bar l₂ on a bell crank m₁ which by means of a tension spring m₂ holds another bell crank m₃ which acts on the sleeve g in the position shown in Fig. 4. On the bar l₂ being moved to the left, so that the left-hand arm m¹₁ of the bell crank m₁ is brought into the position m¹¹₁, the pull exerted by the spring m₂ on the bell crank m₃ will cause the latter to turn anticlockwise so that the arm m₃ is moved into the position m¹¹₃ and the sleeve g is moved suddenly into the other extreme position. For facilitating the operation of the change-over coupling h the arrangement provided according to the invention at the rear end of the gear is used. This arrangement consists of a forked lever n which is pivoted at n₀ below the Cardan shaft and embraces the shaft like a stirrup and which engages by means of two cheeks or jaws o₁, o₂ in the groove c of a sleeve p which is slidably splined on a sleeve extension of the toothed wheel f₁. At its two forked ends n₁ and n₂ the lever is made T-shaped and is provided with recesses n¹₁ and n²₂ respectively. In these recesses balls or the like q₁ and q₂ engage, which are held in a bore of the T-shaped end k²₁ of the bar k₂. Under the action of a spring q₃ the balls are spread apart and forced into the recesses n¹₁ and n²₂. The sleeve p is provided at one end with a collar p₁, and at the other end with a coupling bell p₂ which supports the inner cone r₁ of a cone coupling. The cone r₁ coacts with an outer cone r₂ of a coupling bell s which is fixed on the Cardan shaft b. Between the cheeks o₁ and o₂ and the bell p₂, a ball bearing t is interposed, so that the cheeks o₁, o₂ cause an engagement of the coupling r₁ and r₂ to take place practically without friction. On the other hand a friction connection is intentionally provided between the cheeks or jaws and the collar p₁. The coupling r₁, r₂ is disposed in a separate rear chamber of the gear in such a manner that the half diameter of the coupling r¹, r² may be greater than the distance between the main shaft b and the lay shaft c. The mode of operation is as follows: The first speed is formed for instance through the gear members a—g—e₁—e₂—c₂—i₂—i₁—h—b. For putting the second speed into operation the toothed wheel i₁ is disengaged from i₂ by means of the selector bar k₁ and the change-over coupling h is displaced to the right by means of the selector bar k₂ out of the position shown in the figure. At the same time the lever n is also displaced to the right by the locking device, that is to say by the spring loaded balls q₁ and q₂ which engage in the recesses n¹₁ and n²₂ respectively, until the cheeks o₁, o₂ bring the cone coupling r₁, r₂ into engagement by means of the ball bearing t. By this means the toothed wheel f₁ which is in permanent engagement with the lay shaft and the coupling shaft a which is disconnected from the engine by the engine coupling, is brought into frictional engagement with the Cardan shaft b driven from the vehicle and is synchronised with it. On the pressure being increased by the selector bar k₂, being displaced further to the right, the balls q₁, q₂ are forced out of the recesses n¹₁, n²₂ and the synchronising coupling is uncoupled from the selector bar. The dogs of the sleeve h can now engage without shock in the corresponding dogs of the toothed wheel f₁ and couple the latter 3 with the Cardan shaft. The second speed is thus brought about through the gear members a—c₁—e₁—c₂—f₁—h—b. Let it be assumed that the third speed is the direct speed. For this speed the change-over coupling h is again uncoupled from the toothed wheel f₁ and brought into engagement with the toothed wheel e₁. In the middle position of the change-over coupling h and of the selector bar k₂, the balls q₁ and q₂ again engage in the recesses n¹₁ and n²₂. On the selector bar being displaced further to the left it therefore carries the lever n along with it and presses the cheeks o₁ and o₂ against the collar p₁. Owing to the friction between the stationary cheeks and the collar p₁ which turns with the toothed wheel f₁, the toothed wheel along with the lay shaft and the coupling shaft a, which are in engagement with it, is braked to a certain degree. This braking action has the purpose of bringing the speeds of revolution of the parts h and e₁ which are to be coupled more quickly into correspondence. In the second speed the toothed wheel e₁ runs at a higher speed than the Cardan shaft b. On the coupling h being disengaged from f₁, the toothed wheel is released from the Cardan shaft, the brake acting over the toothed wheel f₁ and the lay shaft on the toothed wheel e₁ which is thereby braked with respect to the Cardan shaft. Thus a more rapid and less noisy engagement of the dogs of h and e₁ becomes possible. The direct drive is by way of the gear members a—g—e₁—h—b. For changing from the third to the fourth speed the coupling parts of e₁ and h remain coupled, while the sleeve g is changed over in the manner described with reference to Fig. 4 by means of the selector bar k₃. This operation can be performed in a known manner without disengaging the engine coupling. When the bell crank m₃ is moved over by means of the selector bar k₃, the lever l₁ and the bar l₂ so that the arm m¹₁ occupies the position m¹¹₁ and the tension spring m₂ exerts a moment on the bell crank m₃ in the opposite direction, the bell crank m₃ is not moved over to actuate the sleeve g since the right-hand dogs of the sleeve are maintained in engagement with the corresponding dogs on the gear wheel e₁ under the action of the torque exerted by the engine. It is only when the engine is throttled and the torque transmitted from the engine to the gear is reduced or ceases entirely that the spring m₂ is able to overcome the friction between the dogs of the members g and e₁ and produce a sudden change-over of the bell crank m₃ and move the sleeve g into its other terminal position, the inclined dogs of the sleeve g and of the toothed wheel d₁ repelling each other until both are running at the same speed and enter into engagement with one another. The gear changes are shown diagrammatically in Fig. 5. I, II, III, IV are the corresponding positions of the common gear lever k and R is the position for the reverse. As will be seen there are two positions for the third speed, according to whether the selector bar k₂ (the sleeve h) is being changed over from the second speed or the selector bar k₃ (sleeve g) from the fourth speed. This makes it possible to cause the synchronising brake p₂ to act only when changing from a lower speed into the third or direct speed, but not when changing over to the third or direct speed from the higher or fourth speed. In the fourth or top speed the drive is by way of the gear members a—g—d₁—d₂—c₂—e₂—e₁—h—b. For changing over from the fourth to the third speed the coupling sleeve g is again moved to the right. When changing from the third to the second speed the change-over coupling h is disengaged from the toothed wheel e₁ and engaged in the toothed wheel f₁, the synchronising coupling r₁, r₂ being again operated. In contradistinction to the synchronising brake p₁ which only becomes operative when changing from a lower to a higher speed by engaging the left-hand dogs h₁, the synchronising coupling p₂ is actuated both when changing up and when changing down by engaging the right-hand dogs h₂, which is of considerable advantage, as it is immaterial for synchronisation which of the two parts to be synchronised is the more rapidly or more slowly moving one. Under certain circumstances, however, the synchronising coupling p₂ could be put into operation, for instance, only when changing over from the higher to the lower speed (III—II). In changing from the second to the first speed the change-over coupling h is again disengaged from the toothed wheel f₁ and in place thereof the sliding wheel i₁ is brought into engagement with the toothed wheel i₂ by means of the selector bar k₁. In the same way a reverse speed wheel which is not shown can be brought into engagement for instance simultaneously with the wheels i₁ and i₂. For these last changes a separate synchronising device is not provided, as it does not seem necessary in view of the practical conditions. In this case as well separate arrangements | ||