Angular contact ramps for driven turbochargers

Abstract

A driven turbocharger (100) for an engine, comprising: a turboshaft (104); a compressor (106) connected to a first location on said turboshaft (104); a turbine (108) connected to a second location on said turboshaft (104); a planetary traction drive (102, 200) coupled to said turboshaft (104) for transferring power to and from the turboshaft (104), said planetary traction drive (102, 200) comprising: a plurality of planetary rollers (110, 210) coupled to said turbo shaft (104); a first ring roller (112, 212) and a second ring roller (114, 214) coupled to beveled traction surfaces (116, 216) on said planetary rollers (110, 210); a toothed ring (118, 218) which is centrally arranged and which is coupled to said first ring roller (112, 212) and said second ring roller (114, 214) via a first angular contact ball ramp (126, 226) and a second angular contact ball ramp (128, 228), such that said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) increase clamping forces in said planetary traction drive (102, 200) when a torque through said toothed ring (118, 218) increases, wherein: said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228) are formed from a plurality of balls in ball races with inclined contact axes, and are shaped to have a tight fit of said balls in said ball races to ensure high efficiency of movement of said balls in said ball races, and wherein said inclined contact axes position said gear ring (118, 218) concentrically with said first ring roller (112, 212) and said second ring roller (114, 214); a transfer gear meshed with said gear ring (118, 218) which transfers power to and from said motor through a transfer unit.

Description

BACKGROUND

[0001] Driven turbochargers are an improvement over conventional turbochargers because they are driven by more than just the exhaust gases, reducing turbo lag in turbocharged engines. Driven turbochargers can also return excess turbine power back to the engine to increase energy efficiency.US 2013 / 0017920 A1 describes a high torque traction drive that uses planetary gears that mesh with the internal teeth of a ring gear, the planetary gears being mounted in rollers whose inner traction surfaces mesh with inclined ring traction surfaces of the traction rings attached to the ring gear, the inclined traction surface causes the rollers to move inward when pushed towards the traction rings, the inward force on the rollers creates a shaft traction surface between a shaft and outer traction surfaces of the roller, so that rotational energy is effectively transferred between the rollers, the shaft and the ring gear.JP 2015-102246 A describes thrust-absorbing planetary gears with inclined roller-shaft traction interfaces for absorbing the thrust generated by a turbine or compressor onto a turboshaft. The inclined traction surfaces on the sun portion of the turboshaft are inclined inward so that the turboshaft remains centered within the planetary gear. DE 11 2010 005 233 T5 describes a super turbocharger using a fixed-ratio, high-speed traction drive coupled to a continuously variable transmission to enable high-speed operation. One high-speed traction drive is used to provide reduction from the high-speed turbine shaft, and a second traction drive provides infinitely variable ratios via a continuously variable transmission. SUMMARY

[0002] The present invention provides a driven turbocharger according to claim 1, a method for generating clamping forces in a planetary traction drive according to claim 5, and a planetary traction drive according to claim 10. Preferred embodiments are subject to the dependent claims. One embodiment of the present invention may therefore comprise a driven turbocharger for an engine, comprising: a turboshaft; a compressor connected to a first location on the turboshaft; a turbine connected to a second location on the turboshaft; a planetary traction drive coupled to the turboshaft for transferring power to or from the turboshaft, the planetary traction drive comprising: a plurality of planetary rollers coupled to the turboshaft; a first ring roller (rolling ring) and a second ring roller (rolling ring) cooperating with chamfered traction surfaces on the plurality of planetary rollers;a centrally located ring gear coupled to the first ring roller and the second ring roller via a first angular contact ball ramp and a second angular contact ball ramp, such that the first angular contact ball ramp and the second angular contact ball ramp increase clamping forces in the planetary traction drive as torque on the ring gear increases, wherein the first angular contact ball ramp and the second angular contact ball ramp consist of a plurality of balls in ball races with inclined contact axes shaped to have a tight fit of the balls in the ball races to ensure highly efficient movement of the balls in the ball races; and the inclined contact axes keep the ring gear concentric with the first ring roller and the second ring roller; a transfer gear meshing with the ring gear, which transfers power to and from the motor through a transfer unit;

[0003] An embodiment of the present invention may therefore further comprise a method for providing clamping forces in a planetary traction drive, comprising the steps of: providing a sun shaft; coupling a plurality of planetary rollers to the sun shaft; coupling a first ring roller and a second ring roller to the plurality of planetary rollers via inclined traction surfaces on the plurality of planetary rollers; providing a gear ring centrally disposed between the first ring roller and the second ring roller;Coupling the gear ring to the first ring roller via a first angular contact ball ramp, and to the second ring roller via a second angular contact ball ramp, such that the first angular contact ball ramp and the second angular contact ball ramp increase a clamping force in the planetary traction drive as the torque across the gear ring increases, wherein the first angular contact ball ramp and the second angular contact ball ramp consist of a plurality of balls in ball races with inclined contact axes that are shaped to have a close fit of the balls in the ball races to enable highly efficient movement of the balls in the ball races, the inclined contact axes keep the gear ring concentric with the first ring roller and the second ring roller;

[0004] An embodiment of the present invention may therefore further comprise a planetary traction drive comprising: a sun shaft; a plurality of planetary rollers coupled to the sun shaft; a first ring roller and a second ring roller coupled to inclined traction surfaces on the plurality of planetary rollers;a centrally disposed ring gear coupled to the first ring roller and the second ring roller via a first angular contact ball ramp and a second angular contact ball ramp, such that the first angular contact ball ramp and the second angular contact ball ramp increase a clamping force in the planetary traction drive as torque across the ring gear increases, wherein the first angular contact ball ramp and the second angular contact ball ramp consist of a plurality of balls in ball races with inclined contact axes shaped to have a close fit of the balls in the ball races to enable highly efficient movement of the balls in the ball races, the inclined contact axes keep the ring gear concentric with the first ring roller and the second ring roller; FIGURE DESCRIPTION Fig. 1 is an isometric view of a driven turbocharger with a planetary traction drive. Fig. 2 is a cross-sectional view of an embodiment of a planetary traction drive with inclined ball ramps. Fig. Figure 3 is a graphical representation of axial force versus applied torque for an angular contact ball ramp and a non-angular contact ball ramp. Fig. 4 is an enlarged cross-sectional view of an embodiment of a ring assembly for the planetary traction drive according to Fig. 2. Fig. 5 is an exploded view of one embodiment of a ring assembly for the planetary traction drive of Fig. 2. DESCRIPTION

[0005] Fig. 1 is an isometric view of a driven turbocharger 100 with a planetary traction drive 102. Turboshaft 104 is connected to the compressor 106 and turbine 108, and the planetary traction drive 102 is coupled to the turboshaft 104 to transfer power to and from the turboshaft 104. The planetary traction drive 102 consists of a plurality of planetary rollers 110 coupled to the turboshaft 104, a first ring roller 112 and a second ring roller 114 coupled to inclined traction surfaces 116 on the planetary rollers 110, and a gear ring 118. Gear ring 118 meshes with the transfer gear 120, which in turn is coupled to the transfer unit 122. Transfer unit 122 transfers power between rotor 124 and planetary traction drive 102. Gear ring 118 is coupled to first ring roller 112 and second ring roller 114 via a first angular contact ball ramp 126 and a second angular contact ball ramp 128.When torque is applied to the gear ring 118, the first angular contact ball ramp and the second angular contact ball ramp push the first ring roller 112 and the second ring roller 114 away from the gear ring 118. This, in turn, increases the normal forces on the inclined traction surfaces 116 of the planetary rollers 110 and increases the clamping force in the planetary traction drive 102. The increased clamping force increases the torque capacity of the planetary traction drive 102 with an increased level of torque flow, thereby improving the efficiency and characteristics of the planetary traction drive 102.During high torque operation, the first angular ball ramp 126 and the second angular ball ramp 128 provide a high level of clamping force in the planetary traction drive 102 to prevent slippage, and during low torque operation, the first angular ball ramp 126 and the second angular ball ramp 128 relax the clamping forces in the planetary traction drive 102 to improve the life and efficiency of the planetary traction drive 102.

[0006] The operation of a driven turbocharger 100 is shown in US 8 561 403 B2, published on October 22, 2013, entitled “Super-Turbocharger Having a High Speed ​​Traction Drive and a Continuously Variable Transmission,” US 8 668 614 B2, published on March 11, 2014, entitled “High Torque Traction Drive,” US 8 608 609 B2, published on December 17, 2013, entitled “Symmetrical Traction Drive,” and US 9 670 832 B2, published on June 6, 2017, entitled “Thrust Absorbing Planetary Traction Drive Superturbo.”

[0007] Fig. Figure 2 is a cross-section of one embodiment of a planetary traction drive 200 with angular contact ramps 226, 228. When torque is applied to the gear ring 218, a first angular contact ramp 226 and a second angular contact ramp 228 push a first ring roller 212 and a second ring roller 214 away from the gear ring 218, increasing the normal forces on the inclined traction surfaces 260 of the planetary rollers 210, resulting in an increased clamping force on the planetary traction drive 200 to increase its torque capacity. The normal forces between the planetary rollers 210 and the sun shaft 204 are also increased. Fig. 1, sun shaft 204 corresponds to turbo shaft 104. Ball races 230 of a first angular contact ball ramp 226 and a second angular contact ball ramp 228 are inclined in two directions so that they operate with torque in either direction through the planetary traction drive 200. Ring gear 218 meshes with transfer gear 220 to transfer power to and from the planetary traction drive 200. Ring gear 218 is completely fixed by the first angular contact ball ramp 226 and the second angular contact ball ramp 228 and has no additional support layer, so it is necessary for the first angular contact ramp and the second angular contact ball ramp to support ring gear 218 concentrically with the first ring roller 212 and the second ring roller 214, both for balanced rotation of ring gear 218 and to ensure proper meshing of ring gear 218 and transfer gear 220.The first angular contact ball ramp 226 and the second angular contact ball ramp 228 consist of a plurality of balls 234 located in a plurality of ball tracks 230. Contact axes 232 of the first angular contact ball ramp 226 and the second angular contact ball ramp 228, in which the balls 240 contact the ball tracks 230, are inclined, with components in both axial and radial directions. This restricts the gear ring 218 to a proper concentric position, even during contact between balls 234 and ball tracks 230, allowing a tight fit between the balls 234 and ball tracks 230, with the curve radius of the ball guides 230 being larger than the radius of the balls 234.This tight fit is beneficial for the first angular contact ball ramp 226 and the second angular contact ball ramp 228 because it reduces rolling friction between balls 234 in ball raceways 230, increasing the efficiency of the first angular contact ball ramp and the second angular contact ball ramp, resulting in a linear clamping force distribution of the planetary traction drive 200. If the contact axes 232 were not inclined and were directed only in an axial direction, a tight fit of the ball 234 to the ball raceways 230 would be necessary to keep the gear ring 218 concentric with the first ring roller 212 and the second ring roller 214, which would increase friction, decrease efficiency, and increase wear in the ball raceways.Additionally, the tight fit of the balls 234 in the ball races 230 allows the balls 234 to have a range of diameters and still provide proper function for the first angular contact ball ramp 226 and the second angular contact ball ramp 228. The ball diameter 234 can be adjusted to compensate for part tolerances in the planetary traction drive 200 and can simultaneously be used to set a desired preload of normal forces on the inclined traction surfaces 260 of the planetary rollers 210.

[0008] Fig. 3 is a graphical representation of axial forces 340 plotted against an applied torque 342 for an angular contact ball ramp 344 and a non-angular contact ball ramp 346. The non-angular contact ball ramp 346 requires ball races with a high fit around the gear ring 218 of Fig. 2 in its position. Because of this tight fit, the non-angular contact ramp 346 has high friction when loaded. This leads to lower performance, as can be seen from the low rate of increase of the axial force 340 versus the applied torque 342, as well as the large hysteresis 348 when the non-angular contact ramp 346 is unloaded. This large hysteresis 348 results in over-clamping of the planetary traction drive 200 from Fig. 2 under certain operating conditions, reducing efficiency and the service life of the planetary traction drive 200. The angular contact ball ramp 344 has ball races with a lower fit because the inclined contact axes provide the necessary alignment / positioning of the gear ring 218. This enables low rolling friction and high efficiency of the angular contact ball ramp 344. As a result, the performance of the angular contact ball ramp 344 is higher, with very low hysteresis, so the clamping forces on the planetary traction drive 200 are more uniform, resulting in higher efficiency and service life of the planetary traction drive 200.

[0009] Fig. 4 is an enlarged cross-sectional view of one embodiment of ring assembly 400 for the planetary traction drive 200 of Fig. 2. The gear ring 418 is centrally located, with a first ring roller 412 and a second ring roller 414 on either side. A first angular contact ball ramp 426 and a second angular contact ball ramp 428 couple the first ring roller 412 and the second ring roller 414 to the gear ring 418 and force the first ring roller 412 and the second ring roller 414 to move away from the gear ring 418 when torque is applied to the gear ring 418. Shown is a single ball 434 in a ball race 430 of the first angular contact ball ramp 426 from among the plurality of balls in ball races for the first angular contact ball ramp 426 and the second angular contact ball ramp 428. The contact axis 432 of ball 434 in ball race 430 is inclined so that the contact axis 432 has components in both radial and axial directions.This allows the ring gear 480 to be held concentrically with the first ring roller 412 and the second ring roller 414 by the first angular contact ball ramp 426 and the second angular contact ball ramp 428, while allowing a tight fit of ball 434 in ball races 430. Also shown are a first ball cage 150 and a second ball cage 452, which can be used to help hold the balls, such as ball 434, in the first angular contact ball ramp 426 and the second angular contact ball ramp 428. As can be seen, the ball races 430 of the first angular contact ball ramp 426 and the second angular contact ball ramp 428 are offset on the ring gear so that the forces on the ring gear 418 from the first angular contact ball ramp 426 and the second angular contact ball ramp 428 are more evenly distributed, allowing for the use of thinner material.

[0010] Fig. 5 is an exploded view of one embodiment of a ring assembly 500 for the planetary traction drive 200 of Fig.2. A first ring roller 512 and a second ring roller 514 are disposed on opposite sides of the gear ring 518 and are coupled to the gear ring 518 via a first angular contact ball ramp 526 and a second angular contact ball ramp 528. The balls 534 lie in ball races 530 so that when torque is applied to the gear ring 518, the balls 534 roll in the ball guide 530 to push the first ring roller 512 and the second ring roller 514 away from the gear ring 518. Additionally, a first ball cage 550 and a second ball cage 552 may be used to assist in retaining balls 534 in the first angular contact ball ramp 526 and the second angular contact ball ramp 528.As can be seen, the ball races 530 of the first angular contact ball ramp 526 and the second angular contact ball ramp 528 are offset on the gear ring 518 to balance the forces on the gear ring 518 generated by the first angular contact ball ramp 526 and the second angular contact ball ramp 528; further, this allows for the use of a thinner material.

[0011] The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed; other modifications and variations may be possible in light of the above disclosure. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to enable those skilled in the art to best utilize the invention in various embodiments and various modifications. It is intended that the following claims be interpreted to include other alternative embodiments of the invention except insofar as limited by the prior art.

Claims

[1] A driven turbocharger (100) for an engine, comprising: a turboshaft (104); a compressor (106) connected to a first location on said turboshaft (104); a turbine (108) connected to a second location on said turboshaft (104); a planetary traction drive (102, 200) coupled to said turboshaft (104) for transferring power to and from the turboshaft (104), said planetary traction drive (102, 200) comprising: a plurality of planetary rollers (110, 210) coupled to said turbo shaft (104); a first ring roller (112, 212) and a second ring roller (114, 214) coupled to beveled traction surfaces (116, 216) on said planetary rollers (110, 210); a toothed ring (118, 218) which is centrally arranged and which is coupled to said first ring roller (112, 212) and said second ring roller (114, 214) via a first angular contact ball ramp (126, 226) and a second angular contact ball ramp (128, 228), such that said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) increase clamping forces in said planetary traction drive (102, 200) when a torque through said toothed ring (118, 218) increases, wherein: said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228) are formed from a plurality of balls in ball races with inclined contact axes, and are shaped to have a tight fit of said balls in said ball races to ensure high efficiency of movement of said balls in said ball races, and wherein said inclined contact axes position said gear ring (118, 218) concentrically with said first ring roller (112, 212) and said second ring roller (114, 214); a transfer gear meshed with said gear ring (118, 218) which transfers power to and from said motor through a transfer unit. [2] The driven turbocharger (100) according to claim 1, wherein said plurality of ball races of said first angular ball ramp (126, 226) are arranged offset from said plurality of ball races on said second angular ball ramp (128, 228) on said gear ring (118, 218). [3] The driven turbocharger (100) of any one of claims 1 or 2, wherein a first ball cage and a second ball cage assist in retaining said plurality of balls in said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228). [4] The driven turbocharger (100) according to any one of the preceding claims, wherein a diameter of said plurality of balls in said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) is selected to establish a desired preload of normal forces on said inclined traction surfaces (116, 216) of said plurality of planetary rollers (110, 210). [5] A method for generating clamping forces in a planetary traction drive (102, 202), comprising the steps of: Providing a solar wave (204); coupling a plurality of planetary rollers (110, 210) to said sun shaft (204); coupling a first ring roller (112, 212) and a second ring roller (114, 214) to said plurality of planetary rollers (110, 210) by beveled traction surfaces (116, 216) on said plurality of planetary rollers (110, 210); Providing a toothed ring (118, 218) which is arranged centrally between said first ring roller (112, 212) and said second ring roller (114, 214); Coupling said gear ring (118, 218) to said first ring roller (112, 212) by a first angular contact ball ramp (126, 226), and to said second ring roller (114, 214) by a second angular contact ball ramp (128, 228) such that said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) increase clamping forces in said planetary traction drive (102, 200) as a torque through said gear ring increases, wherein; said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) are formed from a plurality of balls in ball races with inclined contact axes, and are shaped to have a close fit of said balls in said ball races to ensure high efficiency of movement of said balls in said ball races, and said inclined contact axes hold said gear ring (118, 218) concentric with said first ring roller (112, 212) and said second ring roller (114, 214). [6] The method of claim 5, wherein said plurality of ball raceways on said first angular ball ramp (126, 226) are offset from said plurality of ball raceways on said second angular ball ramp (128, 228) on said gear ring (118, 218). [7] Method according to one of claims 5 or 6, further comprising: Providing a first ball cage and a second ball cage that assists in retaining said balls in said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228). [8] Method according to one of the preceding claims 5 to 7, further comprising: Connecting a turbine (108) and a compressor (106) to said sun shaft (204) to form a turbo shaft (104); Engaging said gear ring (118, 218) with a transfer gear connecting said planetary traction drive (102, 200) to a transfer unit that transfers power between said planetary traction drive (102, 200) and an engine to form a driven turbocharger (100). [9] Method according to one of the preceding claims 5 to 8, wherein diameters of the balls of said plurality of balls in said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) are selected so that a desired preload of normal forces on said inclined traction surfaces (116, 216) of said plurality of planetary rollers (110, 210) is determined. [10] Planetary traction drive (102, 200) comprising: a solar wave (204); a plurality of planetary rollers (110, 210) coupled to said sun shaft (104); a first ring roller (112, 212) and a second ring roller (114, 214) coupled to beveled traction surfaces (116, 216) on said plurality of planetary rollers (110, 210); a toothed ring (118, 218) which is centrally arranged and which is coupled to said first ring roller (112, 212) and said second ring roller (114, 214) via a first angular contact ball ramp (126, 226) and a second angular contact ball ramp (128, 228) such that said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) increase a clamping force in said planetary traction drive (102, 200) when a torque through said toothed ring (118, 218) increases, wherein; said first angular contact ball ramp (126, 226) and said second angular contact ball ramp (128, 228) are formed from a plurality of balls in ball races with inclined contact axes, and are shaped to have a tight fit of said balls in said ball races to ensure high efficiency of movement of said balls in said ball races, and said inclined contact axes place said gear ring (118, 218) concentric with said first ring roller (112, 212) and said second ring roller (114, 214). [11] Planetary traction drive (102, 200) according to claim 10, wherein said plurality of ball races of said first angular ball ramp (126, 226) are arranged offset from said plurality of ball races of said second angular ball ramp (128, 228) on said gear ring (118, 218). [12] The planetary traction drive (102, 200) of claim 10 or 11, wherein a first ball cage and a second ball cage assist in retaining said plurality of balls in said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228). [13] Planetary traction drive (102, 200) according to one of the preceding claims 10 to 12, wherein diameters of the balls of said plurality of balls in said first angular ball ramp (126, 226) and said second angular ball ramp (128, 228) are selected such that a desired preload of normal forces on said inclined traction surfaces (116, 216) of said plurality of planetary rollers (110, 210) is determined.

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