JP2008039011A - Change gear ratio controller of transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a change gear ratio controller of a transmission capable of setting a larger number of gear-change stages than the number of pairs of gears by means of a compact arrangement and of enhancing energy efficiency. <P>SOLUTION: The change gear ratio controller has a change gear ratio control means 43 for setting, according to instructions by a speed change instruction means, a change gear ratio which is set by maximizing the extrusion volume of one of fluid pressure pump motor pumps 12, 13, stopping its rotation, and maximizing the extrusion volume of the other fluid pressure motor pump so that the torque of rotating shafts 8, 10 corresponding to the other fluid pressure pump motor is equal to or less than a predetermined value, and another change gear ratio which assumes a value between change gear ratios determined by two of transmission mechanisms 17, 18, 19, 20 and which is set by setting the extrusion volumes of at least two of the fluid pressure pump motors at a predetermined value close to its maximum. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  According to the present invention, transmission mechanisms having different rotation speed ratios are provided between a plurality of rotation shafts and an output member, and a transmission mechanism that transmits power from the rotation shaft to the output member is selected by engaging a clutch mechanism. The present invention relates to an apparatus for controlling a transmission ratio set by the transmission, which is intended for the transmission configured as described above.

  This type of transmission is known as a twin-clutch stepped transmission, and an example thereof is described in Patent Document 1. The transmission described in Patent Document 1 includes a first input shaft connected to the engine via a first clutch, a second input shaft connected to the engine via a second clutch, an output shaft, A counter shaft connected to the first input shaft via a gear pair, a plurality of gear pairs provided between the first input shaft and the counter shaft and selectively connected by a meshing clutch mechanism; And a plurality of gear pairs which are provided between the two input shafts and the output shaft and are selectively connected by the meshing clutch mechanism. The transmission includes a gear stage that transmits torque from any one of the input shafts to the output shaft through a predetermined gear pair, and any output shaft from the input shaft to the output shaft through the predetermined gear pair and the sub shaft. It is configured to set a gear stage for transmitting torque, and as a result, it is configured to set seven or more gear stages including the reverse gear.

Japanese Patent Application Laid-Open No. 2003-120764

  In the transmission described in Patent Document 1 described above, since the number of shift speeds that can be set is large, the engine can be operated in a state with good fuel efficiency, and the auxiliary shaft is effectively used. The transmission is reduced in size and weight as a whole, and as a result, the fuel consumption of the vehicle can be improved. However, the gear ratio set in the conventional transmission is set by selecting a gear pair involved in power transmission. Therefore, in order to increase the number of gear ratios that can be set (that is, the number of gears), it is necessary to increase the number of gear pairs, and it is difficult to achieve both a multi-stage transmission and a compact transmission. It is. In addition, when setting a predetermined gear ratio, one of the input clutches is maintained in the engaged state, so that power such as hydraulic pressure is consumed in order to maintain the engaged state, and the power associated therewith. Loss may occur and the fuel consumption of the vehicle may deteriorate.

  The present invention has been made by paying attention to the above technical problem, and is a transmission that can be fixedly set in a large number of gear ratios, can be easily made compact, and can improve energy efficiency. An object of the present invention is to provide a gear ratio control device.

  In order to achieve the above object, the invention of claim 1 includes a plurality of rotating shafts to which power is selectively transmitted from a power source, an output member for outputting the power transmitted from these rotating shafts, A plurality of transmission mechanisms arranged between each rotary shaft and the output member; and a clutch mechanism that selectively enables transmission of power between each rotary shaft and the output member via the transmission mechanism. In the transmission gear ratio control apparatus having the transmission, provided for each of the rotary shafts, and controlled so as to have an extrusion volume, torque appears on the rotary shaft, the extrusion volume can be changed, and the motor functions as a motor. Fluid pressure pump motors that can be connected to each other, and the fluid pressure pump motors are connected to each other, and the fluid pressure generated by any one of the fluid pressure pump motors is supplied to the other fluid pressure pump motors. The motor A fluid pressure circuit that functions as a function, a shift instruction means that selectively issues a shift instruction for upshifts and downshifts, and the extrusion volume of any one of the fluid pressure pump motors is set to a predetermined value close to a maximum value or more. The rotation is stopped and the extrusion volume of the other fluid pressure pump motor is set to a predetermined value close to the minimum value or less, and the torque of the rotating shaft corresponding to the other fluid pressure pump motor is set to a predetermined value or less. The transmission ratio is a value between the transmission ratio and the transmission ratio determined by each of the two transmission mechanisms, and the extrusion volume of each of the at least two hydraulic pump motors is set to a predetermined value close to the maximum or more. A transmission ratio control device comprising: a transmission ratio control unit that sets a transmission ratio to be set according to an instruction from the transmission instruction unit.

  According to a second aspect of the present invention, there are provided a plurality of rotating shafts to which power is selectively transmitted from a power source, output members for outputting the power transmitted from the rotating shafts, the rotating shafts and the output members. And a clutch mechanism that selectively enables transmission of power between each rotary shaft and the output member via the transmission mechanism. In the apparatus, a fluid pressure pump motor that is provided for each of the rotating shafts and that is controlled so as to have an extruding volume so that torque appears on the rotating shaft, and the extruding volume can be changed and the motor can function as a motor The fluid pressure pump motors communicate with each other, supply the fluid pressure generated by any one of the fluid pressure pump motors to another fluid pressure pump motor, and cause the other fluid pressure pump motor to function as a motor. A shift instruction means for selectively giving a shift instruction for up-shift and down-shift, and setting the extrusion volume of any one of the fluid pressure pump motors to a predetermined value close to the maximum value or more, A speed ratio set by setting the extrusion volume of the fluid pressure pump motor to a predetermined value which is close to a minimum or less and the torque of the rotating shaft corresponding to the other fluid pressure pump motor is equal to or less than a predetermined value, The transmission ratio is a value between the transmission ratios determined by each of the two transmission mechanisms, the extrusion volume of each of the at least two fluid pressure pump motors is set to be larger than zero, and the power transmission efficiency is a maximum value or a maximum value. A gear ratio control device comprising: a gear ratio control unit that sets a gear ratio that is close to a value according to an instruction from the gear shift instruction unit.

  Further, the invention of claim 3 is the transmission according to claim 1 or 2, wherein the fluid pressure circuit includes a circuit for communicating between the discharge ports and the suction ports of the fluid pressure pump motor. This is a gear ratio control apparatus.

  Furthermore, the invention of claim 4 further comprises a plurality of differential mechanisms provided for each of the rotating shafts in any one of the inventions of claims 1 to 3, wherein each differential mechanism is powered by the power source. An input element to which the rotary shaft is connected, a reaction force element to which the fluid pressure pump motor is connected, and the input element, the output element, and the reaction force element are differentially provided. A transmission gear ratio control device for a transmission, characterized in that it is configured to perform an action.

  A fifth aspect of the present invention is the transmission gear ratio control apparatus according to the fourth aspect of the present invention, wherein the differential mechanism includes a planetary gear mechanism.

  According to the first aspect of the present invention, when the extrusion volume of one of the fluid pressure pump motors is made larger than zero, torque appears on the rotary shaft connected thereto. Therefore, if the transmission mechanism between the rotating shaft and the output member is in a state where torque can be transmitted by the clutch mechanism, the power output from the power source is transmitted to the output member via the transmission mechanism. A gear ratio is set according to the rotation speed ratio of the transmission mechanism. In that case, since any one of the fluid pressure pump motors should be fixed, the power consumed for torque transmission is almost zero, and a predetermined speed change ratio can be set with almost no power loss. it can.

  In the above case, any one of the fluid pressure pump motors functions as a pump, and the fluid pressure generated by the fluid pressure pump motor is supplied to another fluid pressure pump motor. Functions as a motor. At the same time, the transmission mechanism between the rotating shaft connected to the other fluid pressure pump motor and the output member is made to be in a state where torque can be transmitted by another clutch mechanism, so that the power output from the power source is output. Is transmitted to the output member via two transmission mechanisms. That is, transmission of power via fluid pressure occurs in parallel. In that case, since the rotation speed ratio of each transmission mechanism is different, the ratio of the power transmitted through the so-called mechanical means (path) and the ratio of the power transmitted through the fluid are pumps. It is automatically determined by the amount of pressure fluid generated and the pressure. As a result, the set gear ratio is a value between the gear ratio determined according to the rotation speed ratio of one transmission mechanism and the gear ratio determined by the rotation speed ratio of the other transmission mechanism. And since the ratio of the motive power transmitted via each transmission mechanism changes continuously, it will be in a continuously variable transmission state.

  When one of the fluid pressure pump motors functions as a pump and the other fluid pressure pump motor functions as a motor to set the transmission ratio, the extrusion volume of those fluid pressure pump motors is a predetermined value close to the maximum. Set to above. By doing so, the power transmission efficiency at the gear ratio becomes high efficiency close to the power transmission efficiency in the case of setting a so-called fixed gear ratio that transmits power only through one of the transmission mechanisms without passing through the fluid. Become. When a gear ratio is instructed based on a manual operation, either the so-called fixed gear ratio described above or a gear ratio that is an intermediate gear ratio and high transmission efficiency is set. Therefore, since a gear ratio larger than the number of transmission mechanisms can be selected based on manual operation, a transmission having a large number of shift stages can be made compact, and power loss can be prevented or suppressed.

  According to the invention of claim 2, as in the invention of claim 1 above, the speed ratio determined by the rotational speed ratio of the transmission mechanism involved in power transmission and an intermediate value between these speed ratios Is set by a shift instruction based on a manual operation. In the invention of claim 2, the power transmission efficiency by at least two fluid pressure pump motors in which the pushing volume is set to a volume larger than zero for transmission of power to the output member as the intermediate gear ratio is maximum. A gear ratio indicating a value or a value close thereto is set. In other words, the extrusion volume of each fluid pressure pump motor is controlled so that the power transmission efficiency is maximized. Therefore, according to the invention of claim 2, as in the invention of claim 1 above, since a gear ratio larger than the number of transmission mechanisms can be selected based on manual operation, a transmission having a large number of shift stages can be made compact. In addition, power loss can be prevented or suppressed.

  Furthermore, according to the invention of claim 3, power transmission between the fluid pressure pump motors can be performed easily and reliably.

  According to the fourth and fifth aspects of the present invention, it is possible to transmit the power from the power source to the rotating shaft and further to the output member by causing the fluid pressure pump motor to act as a means for generating a reaction force. Since the pump motor does not need to perform a differential action, the configuration can be simplified.

  Next, the present invention will be described based on specific examples. The example shown in FIG. 1 is an example configured as a transmission for a vehicle, and four forward speeds and one reverse speed are set as a so-called fixed speed ratio that can be set by transmitting torque without using fluid. This is a configured example. That is, an input member 2 is connected to a power source (E / G) 1, and torque is transmitted from the input member 2 to the first planetary gear mechanism 3 and the second planetary gear mechanism 4 corresponding to the differential mechanism in the present invention. Configured to communicate.

  The power source 1 may be a general power source used in a vehicle such as an internal combustion engine, an electric motor, or a combination thereof. Further, an appropriate transmission means such as a damper, a clutch, or a torque converter may be interposed between the power source 1 and the input member 2.

  The first planetary gear mechanism 3 is disposed on the same axis as the input member 2, the second planetary gear mechanism 4 is separated outward in the radial direction of the first planetary gear mechanism 3, and the respective central axes are parallel to each other. They are arranged in parallel. These planetary gear mechanisms 3 and 4 correspond to the differential mechanism of the present invention, and an appropriate type planetary gear mechanism such as a single pinion type or a double pinion type can be used. The example shown in FIG. 1 is an example constituted by a single-pinion type planetary gear mechanism, and sun gears 3S and 4S which are external gears, and a ring gear 3R which is an internal gear arranged concentrically with the sun gears 3S and 4S. , 4R, and carriers 3C, 4C holding pinion gears meshed with these sun gears 3S, 4S and ring gears 3R, 4R so as to be rotatable and revolved. The input member 2 is connected to a ring gear 3R in the first planetary gear mechanism 3, and the ring gear 3R serves as an input element.

  Further, a counter drive gear 5 is attached to the input member 2, and an idle gear 6 is engaged with the counter drive gear 5, and a counter driven gear 7 is engaged with the idle gear 6. The counter driven gear 7 is disposed on the same axis as the second planetary gear mechanism 4 and is connected to the ring gear 4R of the second planetary gear mechanism 4 so as to rotate together. Therefore, in the second planetary gear mechanism 4, the ring gear 4R serves as an input element. The ring gears 3R and 4R, which are input elements of the planetary gear mechanisms 3 and 4, are configured so that the counter gear pair includes the idle gear 6, and thus rotate in the same direction.

  The carrier 3C in the first planetary gear mechanism 3 serves as an output element, and a first intermediate shaft 8 corresponding to the rotating shaft in the present invention is coupled to the carrier 3C so as to rotate together. The first intermediate shaft 8 is a hollow shaft into which a motor shaft 9 is rotatably inserted. One end of the motor shaft 9 is a sun gear that is a reaction force element in the first planetary gear mechanism 3. It is connected to 3S so as to rotate together.

  The second planetary gear mechanism 4 has the same configuration, and its carrier 4C serves as an output element, and the second intermediate shaft 10 corresponding to the rotating shaft of the present invention rotates integrally with the carrier 4C. So that they are connected. The second intermediate shaft 10 is a hollow shaft into which a motor shaft 11 is rotatably inserted. One end of the motor shaft 11 is a sun gear that is a reaction force element in the second planetary gear mechanism 4. 4S is connected to rotate integrally.

  The other end of the motor shaft 9 is connected to the output shaft of the variable displacement pump motor 12. The variable displacement pump motor 12 is a fluid pressure (hydraulic) pump capable of changing the discharge capacity, such as a slant shaft pump, a swash plate pump, or a radial piston pump, and is rotated by applying torque to its output shaft. It functions as a motor by discharging pressure fluid (pressure oil) by functioning as a pump and supplying pressure fluid from a discharge port or suction port. In the following description, the variable displacement pump motor 12 is referred to as a first pump motor 12 and is represented as PM1 in the drawing.

  The other end of the motor shaft 11 is connected to the output shaft of the variable displacement pump motor 13. The variable displacement pump motor 13 has the same configuration as the first pump motor 12 on the motor shaft 9 side, and therefore, a fluid capable of changing the discharge capacity, such as an oblique shaft pump, a swash plate pump, or a radial piston pump. A pressure (hydraulic) pump can be employed. In the following description, the variable displacement pump motor 13 is referred to as a second pump motor 13 and is indicated as PM2 in the figure.

  The pump motors 12 and 13 are communicated with each other by oil passages 14 and 15 so that the pressure oil, which is a pressure fluid, can be transferred to each other. That is, the suction ports 12S and 13S are communicated with each other by the oil passage 14, and the discharge ports 12D and 13D are communicated with each other through the oil passage 15. Accordingly, a closed circuit is formed by the oil passages 14 and 15. A mechanism for controlling the hydraulic pressure in the closed circuit will be described later.

  An output shaft 16 corresponding to the output member of the present invention is arranged in parallel with each of the intermediate shafts 8 and 10 described above. A transmission mechanism for setting a predetermined gear ratio is provided between the output shaft 16 and each of the intermediate shafts 8 and 10. The transmission mechanism according to the present invention is not limited to a mechanism that transmits power at a fixed rotational speed ratio (transmission ratio), and a mechanism with a variable transmission ratio can be employed. In the example shown in FIG. A plurality of gear pairs 17, 18, 19, and 20 that transmit power at different gear ratios are employed.

  More specifically, a fourth speed drive gear 17A and a second speed drive gear 18A are arranged on the first intermediate shaft 8 in order from the first planetary gear mechanism 3 side. 17A and the second speed drive gear 18A are rotatably fitted to the first intermediate shaft 8. A fourth speed driven gear 17B meshed with the fourth speed drive gear 17A and a second speed driven gear 18B meshed with the second speed drive gear 18A are attached to the output shaft 16 so as to rotate integrally. Yes.

  Further, a third speed drive gear 19A meshed with the fourth speed driven gear 17B and a first speed drive gear 20A meshed with the second speed driven gear 18B are rotatable on the second intermediate shaft 10. It is made to fit. Accordingly, the fourth speed driven gear 17B also serves as the third speed driven gear, and the second speed driven gear 18B also serves as the first speed driven gear. Here, the rotational speed ratio or gear ratio of each gear pair 17, 18, 19, 20 (ratio of the number of teeth of the driven gear to the number of teeth of each drive gear) will be described. The gear pair 20 for the second gear, the gear pair 18 for the second speed, the gear pair 19 for the third speed, and the gear pair 17 for the fourth speed are configured to become smaller in this order.

  Furthermore, a starting gear pair 21 is provided. The starting gear pair 21 is used to transmit the power to the output shaft 16 together with the first speed gear pair 20 so that the driving force at the time of starting is sufficiently large. A start drive gear 21A attached to the motor shaft 9 on the pump motor 12 side and a start driven gear 21B attached to the output shaft 16 so as to be rotatable are provided.

  A clutch mechanism is provided for allowing each of the gear pairs 17, 18, 19, 20, and 21 described above to transmit torque between any of the intermediate shafts 8 and 10 and the output shaft 16. The clutch mechanism is a mechanism for selectively transmitting torque, and a conventionally known mechanism such as a dog clutch mechanism or a synchronous coupling mechanism (synchronizer) can be employed. FIG. An example of adopting a Nizer is shown.

  The synchronizer basically has a sleeve that rotates together with a rotating shaft, a spline provided on another rotating member that rotates relative to the rotating shaft, and is moved by the sleeve toward the other rotating member. And synchronizer ring. Then, in the process of moving the sleeve to the spline side of the other rotating member, the synchronizer ring gradually makes frictional contact with the rotating member to synchronize the rotating shaft and the rotating member, and in that state the sleeve engages with the spline. Thus, the rotating shaft and the rotating member are connected to each other. On the output shaft 16, a first synchronizer (hereinafter referred to as a first synchronizer) 22 is provided at a position adjacent to the starter driven gear 21B. The first sync 22 moves its sleeve to the left side of FIG. 1 to connect the starter driven gear 21B to the output shaft 16, and the starter gear pair 21 torques between the motor shaft 9 and the output shaft 16. Is configured to communicate.

  On the second intermediate shaft 10, a second synchronizer (hereinafter referred to as a second synchronizer) 23 is provided between the third speed drive gear 19A and the first speed drive gear 20A. The second synchronizer 23 connects the first speed drive gear 20A to the second intermediate shaft 10 by moving the sleeve to the left side in FIG. 1, and the first speed gear pair 20 is connected to the second intermediate shaft 10. Torque is transmitted to and from the output shaft 16. On the other hand, the third speed drive gear 19A is connected to the second intermediate shaft 10 by moving the sleeve to the right in FIG. 1, and the third speed gear pair 19 is connected to the second intermediate shaft 10 and the output shaft 16. Torque is transmitted between the two.

  Further, on the first intermediate shaft 8, a third synchronizer (hereinafter referred to as a third synchronizer) 24 is provided between the second speed drive gear 18A and the fourth speed drive gear 17A. The third synchronizer 24 moves the sleeve to the left side in FIG. 1 to connect the second speed drive gear 18A to the first intermediate shaft 8, and the second speed gear pair 18 is connected to the first intermediate shaft 8. Torque is transmitted to and from the output shaft 16. On the other hand, the fourth speed drive gear 17A is connected to the first intermediate shaft 8 by moving the sleeve to the right in FIG. 1, and the fourth speed gear pair 17 is connected to the first intermediate shaft 8 and the output shaft 16. Torque is transmitted between the two.

  Furthermore, a reverse synchronizer (hereinafter referred to as “R synchro”) 25 is provided on the motor shaft 11 on the second pump motor 13 side at a position adjacent to the shaft end of the second intermediate shaft 10. The R synchro 25 connects the motor shaft 11 and the second intermediate shaft 10, that is, the sun gear 4S and the carrier 4C in the second planetary gear mechanism 4 by moving the sleeve to the right in FIG. The entire planetary gear mechanism 4 is configured to rotate integrally.

  Each of the synchros 22, 23, 24, and 25 can be configured to be switched by manual operation, but can be configured to perform so-called automatic control instead. In that case, for example, an appropriate actuator (not shown) for moving the above-described sleeve in the axial direction may be provided, and the actuator may be electrically controlled.

  As described above, the transmission shown in FIG. 1 is configured such that the torque output from the power source 1 is transmitted to the output shaft 16 via any one of the intermediate shafts 8 and 10 or the motor shafts 9 and 11. Has been. A differential 30 is connected to the output shaft 16 through a transmission means 29 such as a gear mechanism or a winding transmission mechanism such as a chain, and the power is output from this to the left and right axles 31.

  Furthermore, a sensor for detecting the operating state of the transmission is provided. Specifically, the input rotation speed sensor 32 for detecting the rotation speed Nin of the input member 2 or the counter drive gear 5 integrated therewith, the output rotation speed sensor 33 for detecting the rotation speed Nout of the axle 31, the first A rotation speed sensor 34 for detecting the rotation speed NPM1 of the pump motor 12 and a rotation speed sensor 35 for detecting the rotation speed NPM2 of the second pump motor 13 are provided.

  Next, a fluid pressure circuit (hydraulic circuit) for controlling the pump motors 12 and 13 will be described. The closed circuits 14 and 15 communicating with the pump motors 12 and 13 are provided with charge pumps (sometimes referred to as boost pumps) 36 for supplying fluid (specifically oil). Yes. The charge pump 36 is for compensating for the shortage of oil due to leakage from the closed circuit, and is driven by the power source 1 or a motor (not shown) to pump oil from the oil pan 37. It is designed to supply a closed circuit.

  The discharge port of the charge pump 36 communicates with the oil passage 14 and the oil passage 15 in the closed circuit via check valves 38 and 39, respectively. The check valves 38 and 39 are configured to open in the discharge direction from the charge pump 36 and close in the opposite direction. Further, a relief valve 40 for adjusting the discharge pressure of the charge pump 36 is communicated with the discharge port of the charge pump 36. The relief valve 40 is configured to open and discharge oil to the oil pan 37 when a pressure higher than the sum of the elastic force by the spring and the pilot pressure or the pressing force by the solenoid is applied. The discharge pressure is set to a pressure corresponding to the pilot pressure.

  Further, a relief valve 41 is provided between the suction port 12 </ b> S of the first pump motor 12 and the oil passage 15. In other words, the relief valve 41 is provided in parallel with the first pump motor 12 so as to communicate the oil passages 14 and 15. The relief valve 41 is configured to maintain the discharge pressure at a preset pressure when pressure oil is discharged from the suction port 12S of the first pump motor 12 or the suction port 13S of the second pump motor 13. ing. A relief valve 42 is provided between the discharge port 13 </ b> D of the second pump motor 13 and the oil passage 14. In other words, the relief valve 42 is provided in parallel with the second pump motor 13 so as to communicate the oil passages 14 and 15. The relief valve 42 is configured to maintain the discharge pressure at a preset pressure when pressure oil is discharged from the discharge port 13D of the second pump motor 13 or the discharge port 12D of the first pump motor 12. ing.

  The pumping capacity of each of the pump motors 12, 13 and the synchros 22, 23, 24, 25 are configured to be electrically controlled, and an electronic control unit (ECU) 43 is provided for that purpose. The electronic control unit 43 is configured mainly with a microcomputer, and receives the number of rotations of a predetermined rotating member and other detection signals, and the input signals and information stored in advance. In addition, the calculation is performed based on the program, and the command signal is output according to the calculation result.

  Furthermore, a shift device 44 is provided. The shift device 44 selects a position such as stop (P: parking), reverse (R: reverse), neutral (N), forward (D: drive), manual (M: manual), and upshift and downshift. Alternatively, the selection of individual gear ratios such as the first speed to the seventh speed is performed manually. For example, each position is selected by moving the shift lever 45 along a guide groove (not shown), and the shift lever 45 is moved from the manual position to either the left or right or the front or back centered here. An upshift signal to be upshifted and a downshift signal to be downshifted by one stage are output. Alternatively, each position of the first speed to the seventh speed is provided, and the shift lever 45 is moved to those so-called shift position to output a signal instructing each shift speed (speed ratio). Has been. Therefore, the shift device 44 is electrically connected to the electronic control device 43. The shift device 44 corresponds to the shift instructing means of the present invention, selectively instructing upshift and downshift, or a predetermined speed ratio on the adjacent high speed side or a predetermined speed ratio on the adjacent low speed side. Direct instructions are given.

  Next, the operation of the power transmission device described above will be described. FIG. 2 is a chart collectively showing the operation states of the pump motors (PM1, PM2) 12, 13 and the synchros 22, 23, 24, 25 when setting the respective gear positions. “OFF” for each of the pump motors 12 and 13 makes the pump capacity substantially zero, does not generate pressure oil even if the output shaft is rotated, and the output shaft is not supplied even if hydraulic pressure is supplied. A state where the rotor does not rotate (free) is indicated, and “LOCK” indicates a state where the rotation of the rotor is stopped. Furthermore, “hydraulic pressure generation” indicates a state in which the pump capacity is made larger than substantially zero and pressure oil is discharged, and thus the corresponding pump motors 12 and 13 function as pumps. “Hydraulic pressure recovery” indicates a state in which pressure oil discharged from one pump motor 13 (or 12) is supplied to function as a motor, and therefore the corresponding pump motor 12 (or 13) has a shaft torque. The generated torque is transmitted to the corresponding motor shafts 9 and 11 and the intermediate shafts 8 and 10.

  In addition, “right” and “left” for each of the synchros 22, 23, 24, and 25 indicate the positions of the sleeves in the respective synchros 22, 23, 24, and 25 in FIG. 1, and the parentheses are downshifted. The stand-by state, the brackets indicate the stand-by state for upshifting, and “◯” reduces drag by setting the corresponding synchro 22, 23, 24, 25 to the OFF state (neutral position). “●” indicates that the corresponding synchro 22, 23, 24, 25 is set to the OFF state (neutral position) and is in the neutral state.

  When the neutral position is selected by the shift device 44 and the neutral (N) state is set, the pump motors 12 and 13 are turned off, and the sleeves of the synchros 22, 23, 24, and 25 are in the center. Set to position. Therefore, none of the gear pairs 17, 18, 19, 20, 21 is in a neutral state that is not connected to the output shaft 16. That is, the pump motors 12 and 13 are controlled so that the extrusion volume (pump capacity) becomes substantially zero. As a result, a so-called idling state is established, so that even if torque is transmitted from the power source 1 to the ring gears 3R, 4R of the planetary gear mechanisms 3, 4, no reaction force acts on the sun gears 3S, 4S. Therefore, torque is not transmitted to the intermediate shafts 8 and 10 connected to the carriers 3C and 4C that are output elements.

  When the shift position is switched to a travel position such as a drive position, the sleeve of the first sync 22 is moved to the left in FIG. 1 and the sleeve of the second sync 23 is moved to the left in FIG. Therefore, the starting drive gear 21A is connected to the motor shaft 9, the first pump motor 12 and the output shaft 16 are connected, and the first speed drive gear 20A is connected to the second intermediate shaft 10 to be the second planetary gear mechanism. 4 is the output element 4 and the output shaft 16 is connected. That is, the first speed that is the fixed gear ratio is set. At the same time, the extrusion volume of each pump motor 12, 13 is controlled to be larger than zero.

  Therefore, the second pump motor 13 is driven by the power of the power source 1 distributed by the second planetary gear mechanism 4 and functions as a pump. Therefore, the second pump motor 13 gives reaction force torque accompanying generation of hydraulic pressure to the motor shaft 11 and the sun gear 4S. This is described as “hydraulic pressure generation” in FIG. Therefore, torque is transmitted to the carrier 4 </ b> C by the differential action of the second planetary gear mechanism 4, and the torque is transmitted to the output shaft 16 via the first speed gear pair 20.

  On the other hand, the hydraulic pressure generated by the second pump motor 13 is discharged from the suction port 13S and supplied to the suction port 12S of the first pump motor 12. As a result, the first pump motor 12 functions as a motor. This is described as “hydraulic pressure recovery” in FIG. In this way, the power transmitted to the first pump motor 12 is transmitted to the output shaft 16 via the starting gear pair 21. Therefore, in the driving state from the start to the first speed, both so-called mechanical power transmission via the second planetary gear mechanism 4 and power transmission via the hydraulic pressure are generated, and the combined power of these powers is generated. Appears on the output shaft 16. Further, the gear ratio in this process becomes a value larger than the first speed which is a fixed gear ratio, and the gear ratio changes continuously or steplessly.

  Thus, when the speed of the power source 1 and the vehicle speed change to the first speed gear ratio, the extrusion volume of the first pump motor 12 is set to zero, and the extrusion volume q2 of the second pump motor 13 is set to the maximum. As a result, the rotation of the second pump motor 13 is substantially locked. That is, the motor shaft 11 and the second pump motor 13 connected thereto are fixed. At the same time, the first sync 22 is set to the OFF state. As a result, the sun gear 4S of the second planetary gear mechanism 4 is fixed, and the first planetary gear mechanism 3 is not involved in the transmission of power to the output shaft 16, so that the power output from the power source 1 is the second planetary gear. It is transmitted to the output shaft 16 via the mechanism 4 and the first speed gear pair 20. That is, a fixed gear ratio determined by the gear ratio of the first speed gear pair 20 is set. In this case, since the first pump motor 12 and the motor shaft 9 connected thereto are idled, no torque appears on the first intermediate shaft 8.

  In the case of upshifting from the first speed which is the fixed gear ratio, the sleeve of the third sync 24 is moved to the left side in FIG. 1 and the second speed drive gear 18A is connected to the first intermediate shaft 8. The R synchro 25 is kept in a neutral state. Further, when the sleeve of the third synchro 24 is engaged with the second speed drive gear 18A, synchronous control is performed so that the rotation speed of the sleeve of the third synchro 24 matches the rotation speed of the second speed drive gear 18A. The synchronization control is performed in the same manner when the sleeves of the synchros 22, 23, 24, and 25 are engaged with the mating members.

  In this state, the extrusion volume of the first pump motor 12 is gradually increased toward the maximum. In the standby state for upshifting to the second speed, the first pump motor 12 rotates in the reverse direction, and thus functions as a pump by gradually increasing the extrusion volume. That is, hydraulic pressure is generated (indicated as “hydraulic pressure generation” in FIG. 2), and at the same time, a reaction force torque associated therewith appears on the motor shaft 9. As a result, transmission of power through the first planetary gear mechanism 3 and the second speed gear pair 18 is gradually performed. Further, the hydraulic pressure generated by the first pump motor 12 is supplied to the second pump motor 13 and functions as a motor (indicated as “hydraulic pressure recovery” in FIG. 2), and therefore the second pump motor 13 and the second planetary gear. Power is transmitted through the gear mechanism 4 and the first speed gear pair 20. Therefore, the speed ratio in the process of shifting from the first speed to the second speed is a value between the speed ratio of the first speed and the speed ratio of the second speed and is a continuously changing speed ratio. . That is, a continuously variable transmission state in which the gear ratio continuously changes is obtained. This is the same during the period from the start to the speed ratio of the first speed and between the fixed speed ratios. Therefore, the above-described transmission can function as a continuously variable transmission.

  FIG. 3 schematically shows changes in the extrusion volumes of the pump motors 12 and 13 during the upshift process from the first speed to the second speed described above. In the state where the first speed (1st) which is a fixed gear ratio is set, the extrusion volume q1 of the first pump motor 12 is set to zero (or less than a predetermined value close to the minimum), and the second pump motor 13 The extrusion volume q2 is the maximum (max) or more than a predetermined value close to it. Accordingly, the first pump motor 12 and the motor shaft 9 connected to the first pump motor 12 run idle, and the pressure oil cannot flow from the second pump motor 13 to the first pump motor 12. Therefore, the second pump motor 13 becomes locked. From this state, the extrusion volume q1 of the first pump motor 12 is first gradually increased. As a result, hydraulic pressure is generated in the first pump motor 12, and this is supplied to the second pump motor 13, so that the second pump motor 13 acts as a motor. That is, power is transmitted between the pump motors 12 and 13 via the pressure oil.

  Thus, when the extrusion volume q1 of the first pump motor 12 reaches the maximum (max), the extrusion volumes q1 and q2 of the first and second pump motors 12 and 13 both become the maximum or close to a predetermined value close to this. Thereafter, the extrusion volume q2 of the second pump motor 13 is gradually reduced while maintaining the extrusion volume q1 of the first pump motor 12 at a maximum or close to a predetermined value close to this. And the 2nd speed which is a fixed gear ratio is set when the extrusion volume q2 of the 2nd pump motor 13 becomes zero (or below predetermined value near minimum). That is, power is transmitted only through the second speed gear pair 18 of each gear pair, and a gear ratio according to the rotation speed ratio of the second speed gear pair 18 is set.

  The pressure in the oil passages 14 and 15 according to the change in the extrusion volumes q1 and q2 changes as shown in FIG. FIG. 4 shows the actual value of the oil pressure measured by the present inventors. The oil pressure in the oil passages 14 and 15 is in a state where the extrusion volumes q1 and q2 of the pump motors 12 and 13 are both maximized. The lowest. On the other hand, the volumetric efficiency of the pump motors 12 and 13 decreases as the pressure increases. This is consistent with the results measured by the inventors. That is, FIG. 5 shows the volumetric efficiency of the pump motor measured by the present inventors, and the volumetric efficiency of the pump motor decreases as the pressure increases.

  After all, in the gear ratio between the first speed and the second speed, which is the fixed gear ratio (fixed stage), the power transmission is the most at the gear ratio set by maximizing the extrusion volumes q1, q2 of the pump motors 12, 13. Increases efficiency. The result of the transmission efficiency measured by the present inventors is shown in FIG. 6, and the maximum value of the transmission efficiency appears when the extrusion volumes q1 and q2 of the pump motors 12 and 13 are maximized.

  The gear ratio control device according to the present invention is the above when the above-mentioned shift device 44 issues a one-step upshift instruction from the first speed, or when a one-step downshift instruction is issued from the second speed. The transmission ratio is set to a maximum value or a value close to this. Specifically, the extrusion volumes q1 and q2 of the pump motors 12 and 13 are controlled to the maximum, or controlled to a extrusion volume not less than a predetermined value close to the maximum value.

  In FIG. 6, “x” marks indicate actual measurement values, and among these actual measurement values, the actual measurement values indicated by the symbol P0 set the extrusion volumes q1 and q2 of the pump motors 12 and 13 by the non-regulating solenoid valve. The actual measurement value in the case of the configuration is shown. When the extruding volumes q1 and q2 are set to the maximum value by the non-regulating solenoid valve, the hydraulic pressure from the non-regulating solenoid valve hardly flows out, so that the power loss is reduced and the power transmission as a whole. Increases efficiency.

  The motor shaft 9 is substantially fixed by making the extrusion volume of the first pump motor 12 substantially maximum as described above, and stopping its rotation or becoming close to a stop state. In addition, the second pump motor 13 is set to the OFF state. Accordingly, since the sun gear 3S is fixed in the first planetary gear mechanism 3, the power input to the ring gear 3R is output from the carrier 3C to the second speed drive gear 18A via the intermediate shaft 8. On the other hand, the second pump motor 13 is in the OFF state, and the R synchro 25 and the second synchro 23 arranged coaxially with the second pump motor 13 are in the OFF state and the sleeve is in the neutral position. The motor 13 and the second planetary gear mechanism 4 are not involved in power transmission. Accordingly, the second speed, which is a fixed gear ratio determined by the gear ratio of the second speed gear pair 18, is set.

  Similarly, the third speed is achieved by moving the sleeve of the second synchro 23 to the right in FIG. 1 to connect the third speed drive gear 19A to the second intermediate shaft 10, and the second pump motor 13 push-out volume. Is maximized, as in the case of the first speed, the motor shaft 11 and the second pump motor 13 are fixed, and the other synchros 22 and 24 are turned off. Accordingly, the power is transmitted to the output shaft 16 via the third speed gear pair 19, and the third speed, which is a fixed gear ratio, is set. Further, in the fourth speed, the sleeve of the third synchro 24 is moved to the right side in FIG. 1 to connect the fourth speed drive gear 17A to the first intermediate shaft 8, and the extrusion volume of the first pump motor 12 is maximized. As a result, as in the case of the second speed, the motor shaft 9 and the first pump motor 12 are fixed, and the other synchros 23 and 25 are turned off. Therefore, power is transmitted to the output shaft 16 via the fourth speed gear pair 17 and the fourth speed, which is a fixed gear ratio, is set.

  Even in the state between these fixed speed ratios of the second speed to the fourth speed, the extrusion volumes q1 and q2 of the pump motors 12 and 13 can be set to a maximum or a predetermined value close to the maximum. In this case as well, the transmission efficiency exhibits a maximum value, and a gear ratio that is an intermediate value between the fixed gear ratios can be set. FIG. 7 shows the transmission efficiency and the power transmission ratio by the fluid at each fixed gear ratio and an intermediate gear ratio. The transmission efficiency at the point marked with “★” in FIG. 7 is the transmission efficiency at the intermediate gear ratio of the fixed gear ratio. The gear ratio control apparatus according to the present invention uses this to set the gear ratio between the fixed gear ratios by a one-stage upshift or downshift gearshift operation from the fixed gear ratio. Yes. Specifically, the synchros 22, 23, and 24 are operated on the upshift side or the downshift side, and the state controls the extrusion volumes of the pump motors 12 and 13 to a maximum or a predetermined value close to the maximum, respectively. .

  Further, the reverse gear will be described. When the reverse position is selected by the shift device 44, the sleeve 22 of the first sync 22 is moved to the left side of FIG. 1, and the sleeve of the R sync 25 is moved to the right side of FIG. And the other syncs 23 and 24 are set to the OFF state. Therefore, when the second intermediate shaft 10 and the motor shaft 11 are connected by the R sync 25, the sun gear 4S of the second planetary gear mechanism 4 and the carrier 4C are connected, and the entire second planetary gear mechanism 4 is substantially the same. Integrated. The start drive gear 21 </ b> A is connected to the motor shaft 9, that is, the rotor of the first pump motor 12.

  Therefore, the power transmitted from the power source 1 to the second planetary gear mechanism 4 is transmitted to the second pump motor 13 as it is, and this is driven, and the second pump motor 13 generates hydraulic pressure. Since the second synchro 23 is in the OFF state, power is not transmitted from the second planetary gear mechanism 4 or the second intermediate shaft 10 to the output shaft 16. On the other hand, the extrusion volume of the first pump motor 12 is controlled to a volume larger than zero, for example, the maximum volume. As a result, the first pump motor 12 functions as a motor by the hydraulic pressure supplied from the second pump motor 13 and outputs torque to the motor shaft 9. In that case, since the hydraulic pressure is supplied to the first pump motor 12 from the discharge port 12D, the first pump motor 12 rotates in the reverse direction. Then, the torque is transmitted to the output shaft 16 via the starting gear pair 21, so that a reverse state is established. That is, in the reverse speed, power is transmitted via hydraulic pressure, and in FIG. 2, this is indicated as “hydraulic pressure recovery” for the first pump motor 12 and “hydraulic pressure generation” for the second pump motor 13.

  As described above, in the transmission ratio control apparatus according to the present invention for the transmission shown in FIG. 1, the power transmission efficiency is the maximum value or close to the intermediate transmission ratio of the fixed transmission ratio determined by the gear pair. The gear ratio indicating the value is set as a gear ratio (or gear position) that is instructed based on manual operation. Therefore, in the above specific example, the first to fourth speeds, which are so-called fixed speed ratios determined according to the respective gear pairs 17, 18, 19, and 20, and a total of seven speed ratios in the middle three speed ratios. The gear ratio can be selected and set by manual operation. Therefore, since the number of required gear pairs can be reduced with respect to the number of settable shift speeds, the overall configuration of the transmission can be made compact, and the in-vehicle performance and fuel efficiency can be improved. . Further, in order to set the fixed gear ratio, power is not particularly consumed, and the gear ratio having an intermediate value of the fixed gear ratio is set in a state where the volumetric efficiency of each of the pump motors 12 and 13 is maximum or close to the maximum. Therefore, energy efficiency can be improved, and consequently the fuel consumption of the vehicle can be improved.

  The above example is an example in which the intermediate transmission ratio of the fixed transmission ratio is set by setting the extrusion volumes q1 and q2 of the pump motors 12 and 13 to the maximum or a predetermined value close to the maximum. In the transmission having the configuration shown in FIG. 1, it is also possible to execute the shift from the fixed gear ratio by changing both the extrusion volumes q1 and q2 of the pump motors 12 and 13. In this case, since the extrusion volumes q1 and q2 do not become the maximum value or the predetermined value close to the maximum, the intermediate gear ratio of the fixed gear ratio is set as follows.

  That is, since the power transmission efficiency is affected by the oil pressure in the oil passages 14 and 15 and the volumetric efficiency of the pump motors 12 and 13, the transmission efficiency changes in the process of shifting between the fixed gear ratios. To do. Even in such a case, there is a gear ratio in which the transmission efficiency shows a maximum value as in the case shown in FIG. 6 or FIG. This gear ratio is not set when either of the extrusion volumes q1 and q2 of the pump motors 12 and 13 is maximized, but the extrusion volumes q1 and q2 are set to zero or larger than the minimum respectively. This is the transmission ratio obtained. Therefore, the gear ratio may not be uniquely determined from the extrusion volumes q1 and q2 of the pump motors 12 and 13, so the gear ratio at which the transmission efficiency shows the maximum value and the control state of the pump motors 12 and 13 are determined. This may be determined experimentally and determined as an intermediate gear ratio of the fixed gear ratio. In that case, it is good also as a gear ratio which shows the transmission efficiency higher than the average value of the transmission efficiency in the middle state of a fixed gear ratio. In such a case, the gear ratio set by the gear shift instruction based on manual operation may deviate somewhat from the gear ratio at which the transmission efficiency shows the maximum value, but the difference between the transmission efficiency and the maximum value is slight. This is not a problem.

  Even when the gear ratio set by the gear shift instruction based on manual operation is configured as described above, the extrusion volumes q1 and q2 of the pump motors 12 and 13 are controlled to a maximum value or a predetermined value close to the maximum value. As in the case of setting the gear ratio, energy efficiency can be improved, and the number of required gear pairs or transmission mechanisms can be relatively reduced, so that the transmission should be compact as a whole. Can do. As a result, the fuel consumption of the vehicle can be improved.

  It should be noted that the present invention is not limited to the above specific example, and the fixed gear ratio may be greater than the fourth speed, or vice versa. Even in this case, it is possible to select and set an intermediate gear ratio between the fixed gear ratios based on a manual operation. In principle, when the number of fixed gear ratios is n, the number (2n-1) of gear ratios can be set based on manual operation without particularly impairing energy efficiency. . Further, it is not necessary to provide an intermediate gear ratio (gear) between all the fixed gear ratios, and a gear ratio (gear) may be appropriately provided in consideration of a step width between the gear ratios. Good.

  Further, the transmission targeted by the present invention connects the casing and the rotor of the fluid pressure pump motor to the rotating members on the input side and the output side, respectively, so that the fluid pressure pump motor itself performs a differential function. In this case, the planetary gear mechanism as the differential mechanism described above can be omitted. Furthermore, in the above specific example, a configuration in which two intermediate shafts corresponding to the rotary shaft of the present invention are provided is shown. However, in the present invention, three or more rotary shafts are provided, and the number of fluid pressure pump motors is increased accordingly. May increase.

  Furthermore, in the present invention, a mechanism such as a belt or a chain may be used instead of the gear pair. In the case of using a gear mechanism having a differential action in the present invention, for example, a double pinion type planetary gear mechanism can be used instead of the single pinion type planetary gear mechanism, or a differential gear mechanism of another configuration is used. You can also Further, the power source may be connected to the idle gear of the counter gear pair described above instead of being directly connected to one of the differential mechanisms. In addition, the shift instruction means in the present invention is not limited to the so-called lever type described above, and may be constituted by a switch.

  On the other hand, as an actuator such as a solenoid valve for setting the extrusion volume of the fluid pressure pump motor to a maximum or a predetermined value close to the maximum, an actuator that cuts off the current and maintains the extrusion volume can be used. . In this way, energy consumption is eliminated or reduced even when a gear ratio intermediate between the fixed gear ratios is maintained, which is advantageous in improving fuel consumption.

1 is a skeleton diagram schematically showing an example of a transmission according to the present invention. FIG. It is a table | surface which shows collectively the operation state of each pump motor and each synchro at the time of setting each gear ratio. It is a schematic diagram which shows the change of the extrusion volume in the process of setting the gear ratio of the intermediate value of a fixed gear ratio. It is a figure which shows typically the change of the pressure of the oil path in the process, or a hydraulic circuit. It is a figure which shows the relationship between the pressure of a pump motor, and volumetric efficiency. It is a figure which shows the measured value of the transmission efficiency between fixed gear ratios. It is a figure which shows the transmission efficiency in each fixed gear ratio, and the intermediate gear ratio, and the transmission ratio of the power through a fluid.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power source (E / G), 2 ... Input member, 3 ... 1st planetary gear mechanism, 4 ... 2nd planetary gear mechanism, 8 ... 1st intermediate shaft, 9 ... Motor shaft, 10 ... 2nd intermediate shaft, DESCRIPTION OF SYMBOLS 11 ... Motor shaft, 12 ... Variable displacement pump motor (first pump motor), 13 ... Variable displacement pump motor (second pump motor), 14, 15 ... Oil passage, 16 ... Output shaft, 17, 18, 19 , 20 ... Gear pair, 22 ... First synchronizer (first synchronizer), 23 ... Second synchronizer (second synchronizer), 24 ... Third synchronizer (third synchronizer), 43 ... Electronic control unit (ECU), 44... Shift device.

Claims (5)

A plurality of rotating shafts selectively transmitting power from a power source, an output member that outputs the power transmitted from these rotating shafts, and a plurality of shafts disposed between each rotating shaft and the output member In a transmission gear ratio control device having a transmission mechanism and a clutch mechanism that selectively enables transmission of power between each rotary shaft and the output member via the transmission mechanism,
A fluid pressure pump motor that is provided for each of the rotating shafts, and that is controlled to have an extrusion volume so that torque appears on the rotating shaft, the extrusion volume can be changed and the motor can function as a motor;
A fluid pressure circuit that causes the fluid pressure pump motors to communicate with each other, supplies fluid pressure generated by one of the fluid pressure pump motors to another fluid pressure pump motor, and functions the other fluid pressure pump motor as a motor; ,
Shift instruction means for selectively giving upshift and downshift instructions;
The extrusion pressure of any one of the fluid pressure pump motors is set to a predetermined value close to the maximum value or more, the rotation is stopped, and the extrusion volume of the other fluid pressure pump motors is set to a predetermined value close to the minimum value or less to reduce the other fluid pressure. This is a gear ratio that is a value between the gear ratio set when the torque of the rotating shaft corresponding to the pump motor becomes a predetermined value or less and the gear ratio determined by each of the two transmission mechanisms. And a gear ratio control means for setting a gear ratio set by setting the extrusion volumes of each of the at least two fluid pressure pump motors to a predetermined value close to the maximum or more according to an instruction from the gear shift instruction means. A transmission ratio control device for a transmission. A plurality of rotating shafts selectively transmitting power from a power source, an output member that outputs the power transmitted from these rotating shafts, and a plurality of shafts disposed between each rotating shaft and the output member In a transmission gear ratio control device having a transmission mechanism and a clutch mechanism that selectively enables transmission of power between each rotary shaft and the output member via the transmission mechanism,
A fluid pressure pump motor that is provided for each of the rotating shafts, and that is controlled to have an extrusion volume so that torque appears on the rotating shaft, the extrusion volume can be changed and the motor can function as a motor;
A fluid pressure circuit that causes the fluid pressure pump motors to communicate with each other, supplies fluid pressure generated by one of the fluid pressure pump motors to another fluid pressure pump motor, and functions the other fluid pressure pump motor as a motor; ,
Shift instruction means for selectively giving upshift and downshift instructions;
The extrusion pressure of any one of the fluid pressure pump motors is set to a predetermined value close to the maximum value or more, the rotation is stopped, and the extrusion volume of the other fluid pressure pump motors is set to a predetermined value close to the minimum value or less to reduce the other fluid pressure. This is a gear ratio that is a value between the gear ratio set when the torque of the rotating shaft corresponding to the pump motor becomes a predetermined value or less and the gear ratio determined by each of the two transmission mechanisms. A gear ratio that sets the extrusion volume of each of the at least two fluid pressure pump motors to be larger than zero and sets the gear ratio at which the power transmission efficiency becomes a maximum value or a value close to the maximum value in accordance with an instruction from the shift instruction means. A transmission ratio control device for a transmission, comprising: a ratio control means.   The gear ratio control apparatus for a transmission according to claim 1 or 2, wherein the fluid pressure circuit includes a circuit that connects discharge ports and suction ports of the fluid pressure pump motor. A plurality of differential mechanisms provided for each of the rotating shafts;
Each differential mechanism has an input element to which power is transmitted from the power source, an output element to which the rotary shaft is connected, and a reaction force element to which the fluid pressure pump motor is connected. 4. The transmission gear ratio control device according to claim 1, wherein the output element and the reaction force element are configured to perform a differential action.   5. The transmission gear ratio control device according to claim 4, wherein the differential mechanism includes a planetary gear mechanism.

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