Continuously variable transmission

p0001The invention relates to a transmission having the features according to the preamble of Claim first

p0002For gear units with a power arm with variable speed and a power arm with constant speed a summation sums the output of the two power branches, and transmit it via a mechanical transmission to drive a vehicle.

p0003There are numerous known gear, where a hydrostatic unit having a pump and a hydraulic motor forms the continuously variable power branch. If the mechanical power branch interrupted by a clutch, the hydraulic power branch transfers the entire performance. If the hydrostatic zeroed, the mechanical power branch transfers the entire performance. Between these two operating points, the power distribution is determined by the control of the hydrostatic and thus regulates the output speed continuously. Such transmissions are used inter alia for tractors and other machinery.

p0004In other transmissions of the aforementioned type a mechanical continuously variable transmission, ZB forms a variator as a continuously variable transmission, the continuously variable power branch. Since this transmission can not be set to a zero speed, they are only a starting clutch for a drive with internal combustion engines.

p0005Basically for both types of transmissions that the effort and the size of the continuously variable power branch is greater, the higher the torque to be transmitted and the greater the conversion range. To keep the variator small, the overall gear ratio of the transmission is divided by switchable gear stages into several forward and reverse speed ranges. In any driving range the variator moves through its entire adjustment range from maximum to minimum or vice versa. In the end positions reached to be switched switching elements of the gear synchronous speed, so that can be switched smoothly and without load interruption.

p0006However, the circuit complexity increases with the number of switching stages, as hereby increases the number of switching elements. Usually one uses frictional shifting elements in the form of wet multi-plate clutches or - brakes, which are connected by hydraulic actuators with pistons and numerous sealing elements. Your no-load losses are relatively large because the oil between the blades causes drag torques.

p0007The invention has for its object to provide a transmission having a continuously variable driving power over several driving ranges, the number of driving ranges should be kept small without the continuously variable power branch is too large or overworked.

p0008It is achieved according to the invention by the features of claim 1.

p0009The invention provides a mechanical, power-split transmission with a plurality, preferably four forward speed ranges is provided. Thereby, the variator can be kept small. For the circuit of the four forward driving ranges and two reverse driving ranges only four planetary gear sets, the four clutches and two brakes are required. For three forward ranges reduces the number of planetary gear sets to three with otherwise largely identical components. Thus, can be covered with lower and higher demands on driving ranges with the same transmission concept applications.

p0010In addition, has a favorable effect that the variator is driven by an input gear stage at a constant speed increasing ratio. This variator is charged only by a relatively small torque for the same power, and it can be dimensioned correspondingly small. However, the translation stage must be considered in the overall gear ratio; but in the subsequent gear stages are high torque with good efficiency and low wear easier to control than the variator.

p0011In the description and in the claims, various features are shown and described in conjunction. The expert will look at the combined features expediently in terms of tasks to be solved individually and combine them to form further reasonable combinations.

p0012In the drawing, an embodiment of the invention is illustrated and further advantages will be explained in connection with the figures.

p0013It shows:<ul><li>Fig. 1 shows diagrammatically a continuously variable transmission with a continuously variable transmission as a variator in one of two power branches, and</li><li>FIG. 2 a table switching logic.</li></ul>

p0014A prime mover, not shown, drives the continuously variable transmission via a drive shaft 2, which is mounted in a housing 1 of the transmission and on which a gear 17 is fixedly mounted, which forms an input stage with a constant speed increasing ratio with a gear 18, a short input constant called.

p0015The gear 18 drives a primary conical pulley pair 12 of a variator 3, which is arranged on a counter shaft 5 and a encircling element 19, for. Example, a chain, a belt or push belt, is in operative connection with a secondary conical pulley pair 13. The ratio of the variator 3 is adjustable by the primary cone pulleys 12 and secondary conical disks 13 are adjusted accordingly.

p0016For this purpose are generally used hydraulic actuators, which are electronically controlled by a microprocessor, depending on engine, vehicle or operating parameters using characteristics, maps or fuzzy rules. Details are not shown here. The variator 3 is the main component of the continuously variable power branch.

p0017On the countershaft 5 is located a further gear 14, which is arranged via a gear 15 on a secondary drive shaft 23, coaxial with the drive shaft 2, a gear 16 at the input of a summing gear 4 drives.

p0018The summing gear 4 has four planetary gear sets with sun gears S, planet P, ring gears and planetary carriers H T, to which the planet P are rotatably supported. The Planet P mesh with the sun gears S and the ring gears H. Depending on to what planet set include the individual gear components, they are also marked to the letter with a corresponding number, eg., S1 represents the sun gear of the first planetary gear set.

p0019The summing 4 shifted by four clutches K1, K2, K3, K4 and two brakes B1 and B2 in four forward ranges and two reverse ranges R1, R2. The schematic circuitry of FIG. 2 indicates which switching element in which traveling area closed. The switching elements are not marked with a cross are open. Although switching between the operating ranges in the synchronous state, ie, to be switched circuit elements have reached the same speed, the switching elements are overlapping closed or opened.

p0020The gear wheel 16 drives the planet carrier and the ring gear T1 H2 at a constant speed, while the secondary conical pulley pair 13 drives the sun gear S1 via a secondary shaft 20 at a variable speed. The accumulated number of revolutions is in the first driving range on the ring H3 and forwarded the clutch K1 and an intermediate shaft 22 to the sun gear S3 of the third planetary gear set. The sun gear S3 drives via the planet P3 to the satellite carrier T3, which is connected to an output shaft of the sixth

p0021When the brake B1 which is connected with the ring gear and the sun gear S4 H3, is closed, the first forward driving range is switched; when the brake B2, which is connected with the ring gear H4, is closed, the first reverse range R1 is connected.

p0022In the second driving range, the clutch K2 is closed. The variable speed will be forwarded directly via the clutch K2 and the intermediate shaft 22 to the sun gear S3. The brakes B1 and B2 act as the first driving range and determine the forward and reverse direction.

p0023In the third driving range, the clutch connects the planet carrier K3 T2 T3 to the planet carrier, which is connected to the output shaft. 6 It's just a forward range possible, which is determined by the accumulated by the first and second planetary gear speed.

p0024In the fourth operating range, is also possible only in forward driving direction, the clutches K2 and K4 are closed so that the planet carrier T3 is driven directly from the secondary conical pulley pair. 13

p0025A simplified version may with largely the same components be realized that the second planetary gear set with the sun gear S2, the planetary P2, the planet carrier T2 and the ring gear H2 is omitted and instead of the planet carrier T1 connected by a dashed line connection 24 at the clutch K3 is. Instead of the third forward range, the planet carrier T3 is now driven at a constant speed with the clutch K3. During this time, the variator 3 is moved back to its original state and thus prepared for the fourth operating range, in the then can be switched without any interruption by the clutches K2 and K4 are closed and the clutch K3 opens. A flattening of the acceleration curve can be compensated by an intervention in the motor control.

p0026A clutch 9, the PTO shaft 23 connect via a reduction stage with gears 10, 11 with an engine speed-dependent PTO. 8

numeral

p0027<dl id="dl0001" compact="compact"><dt>1</dt><dd>housing</dd><dt>2</dt><dd>drive shaft</dd><dt>3</dt><dd>variator</dd><dt>4</dt><dd>summing</dd><dt>5</dt><dd>Countershaft</dd><dt>6</dt><dd>output shaft</dd><dt>7</dt><dd>axle differential</dd><dt>8th</dt><dd>PTO</dd><dt>9</dt><dd>coupling</dd><dt>10</dt><dd>gear</dd><dt>11</dt><dd>gear</dd><dt>12</dt><dd>Primary conical disks</dd><dt>13</dt><dd>Secondary cone pulleys</dd><dt>14-18</dt><dd>gear</dd><dt>19</dt><dd>encircling</dd><dt>20</dt><dd>secondary shaft</dd><dt>21</dt><dd>coupling shaft</dd><dt>22</dt><dd>intermediate shaft</dd><dt>23</dt><dd>PTO shaft</dd><dt>24</dt><dd>connection</dd><dt>B1</dt><dd>brake</dd><dt>B2</dt><dd>brake</dd><dt>H1 - H4</dt><dd>ring gear</dd><dt>P1 - P4</dt><dd>planet</dd><dt>S1 - S4</dt><dd>sun</dd><dt>T1 - T4</dt><dd>planet carrier</dd><dt>K1 - K4</dt><dd>coupling</dd></dl>