JP6599226B2 - Control device for power split type continuously variable transmission - Google Patents

Description

  The present invention relates to a control device for a power split type continuously variable transmission capable of dividing power input to an input shaft (input shaft) into two systems and transmitting the power to an output shaft (output shaft).

  As a transmission mounted on a vehicle such as an automobile, a continuously variable transmission mechanism that continuously changes engine power, a gear mechanism that transmits engine power without going through a continuously variable transmission mechanism, and a continuously variable transmission mechanism There has been proposed a planetary gear mechanism for synthesizing the power from the gear and the power from the gear mechanism. In this transmission, the power from the engine can be divided into a continuously variable transmission mechanism and a gear mechanism, and the divided powers can be combined by the planetary gear mechanism and transmitted to the wheels.

JP 2004-176890 A

  The applicant has also proposed a transmission capable of dividing and transmitting the power of the drive source into two systems as a power split type continuously variable transmission.

  The power split continuously variable transmission according to the proposal includes a continuously variable transmission mechanism, a parallel shaft gear mechanism, and a planetary gear mechanism. The continuously variable transmission mechanism has the same configuration as a known belt-type continuously variable transmission (CVT). Engine power input to the input shaft is transmitted to the primary shaft of the continuously variable transmission mechanism. The secondary shaft of the continuously variable transmission mechanism is connected to the sun gear of the planetary gear mechanism. The parallel shaft gear mechanism includes a split drive gear that transmits / cuts off the power of the input shaft, and a split driven gear that forms a gear train with the split drive gear and rotates integrally with the carrier of the planetary gear mechanism. An output shaft is connected to the ring gear of the planetary gear mechanism. The rotation of the output shaft is transmitted to the differential gear, and is transmitted from the differential gear to the left and right drive wheels.

  In this power split type continuously variable transmission, a belt mode and a split mode are provided as power transmission modes during forward traveling.

  In the belt mode, the sun gear and the ring gear of the planetary gear mechanism are directly connected. Further, the transmission of power from the input shaft to the split drive gear is interrupted, so that the split drive gear is in a free rotation state (free), and the carrier of the planetary gear mechanism is in a free rotation state. Therefore, the sun gear and the ring gear rotate integrally with the power output from the continuously variable transmission mechanism, and the output shaft rotates integrally with the ring gear. Therefore, in the belt mode, the gear ratio (unit gear ratio) of the power split continuously variable transmission matches the gear ratio (belt gear ratio) of the continuously variable transmission mechanism.

  In the split mode, the direct connection between the sun gear and the ring gear of the planetary gear mechanism is released. Therefore, the sun gear is rotated by the power output from the continuously variable transmission mechanism. On the other hand, power is transmitted from the input shaft to the split drive gear, and the power is shifted from the split drive gear via the split driven gear at a constant split gear ratio and input to the carrier of the planetary gear mechanism. Therefore, in the split mode, the larger the belt speed ratio, the smaller the unit speed ratio, and a speed ratio that is less than or equal to the split speed ratio can be realized.

  When the belt transmission ratio and the split transmission ratio are shifted, a differential rotation occurs between the sun gear and the carrier. Therefore, when the belt mode and the split mode are switched, the belt slips due to the differential rotation. In addition, slipping of a clutch engaged for switching between the belt mode and the split mode may occur. Therefore, switching between the belt mode and the split mode needs to be performed in a state where the belt speed ratio and the split speed ratio substantially match (a state where the sun gear rotation speed and the carrier rotation speed substantially match).

  However, due to various factors such as delay in clutch response, variation in time required for engagement / disengagement of the clutch, and fluctuations in hydraulic pressure that controls the belt transmission ratio of the continuously variable transmission mechanism, there is a difference between the belt transmission ratio and the split transmission ratio. The belt mode or the split mode may be switched in a state where the deviation occurs, and the belt or the clutch may slip. If the belt slips repeatedly, the belt temperature rises and the belt may be seized.

  An object of the present invention is to provide a control device for a power split type continuously variable transmission that can suppress the occurrence of belt seizure caused by slipping of the belt when the belt mode and the split mode are switched.

  In order to achieve the above object, a control device for a power split continuously variable transmission according to the present invention includes an input shaft, an output shaft, a sun gear, a carrier, and a ring gear, and the ring gear rotates integrally with the output shaft. A planetary gear mechanism provided in a possible manner, a belt-type continuously variable transmission mechanism that continuously transmits power input to the input shaft and transmits it to the sun gear, and power input to the input shaft at a constant gear ratio. A split transmission mechanism that shifts and transmits to the carrier, a first engagement element that is engaged / released to switch transmission / cut-off of power to the carrier by the split transmission mechanism, and the sun gear and the ring gear can rotate integrally. And a second engaging element that is engaged / released to be coupled / separated to / from the power splitting type continuously variable transmission, wherein the first engaging element Mode switching means for switching between a belt mode in which the second engagement element is released and a split mode in which the first engagement element is engaged and the second engagement element is released; An interval time setting means for acquiring a differential rotation speed generated between the sun gear and the carrier at the time of switching between the belt mode and the split mode by the mode switching means and setting an interval time based on the acquired differential rotation speed; A switching restriction means for restricting switching between the belt mode and the split mode by the mode switching means after the interval time is set by the interval time setting means until the set interval time elapses after the start of the predetermined interval; including.

  According to this configuration, the differential rotational speed generated between the sun gear and the carrier when the belt mode and the split mode are switched is acquired, and the interval time is set based on the differential rotational speed. Then, the switching between the belt mode and the split mode is restricted from the start of the predetermined interval until the set interval time elapses.

  When the belt mode and the split mode are switched while the differential rotation is generated between the sun gear and the carrier, and the belt slips, frictional heat is generated in the belt. Since the switching between the belt mode and the split mode is restricted within the interval time, the generation of frictional heat due to the slipping of the belt is suppressed. Therefore, by setting the interval time, the temperature of the belt can be lowered, and the occurrence of image sticking can be suppressed. Further, since the frequency of occurrence of belt slip is reduced, abnormal wear of the belt can be suppressed.

  The start of the interval may be simultaneous with the setting of the interval time, or may be the time when a predetermined time has elapsed since the setting of the interval time.

  The differential rotational speed generated between the sun gear and the carrier is changed at the start of the control for switching between the belt mode and the split mode, that is, the first engaging element and the second engaging element are switched. It may be acquired at the start of the control, or may be acquired when the engagement of the first engagement element or the second engagement element is started during the switching control. Further, it may be acquired at any time from the start of the switching control to the time when the engagement of the first engagement element or the second engagement element is started.

  The interval time may be set to a length according to the heat generation amount estimated based on the differential rotation speed.

  For example, the larger the estimated calorific value, the longer the interval time may be set continuously or stepwise. Accordingly, the belt temperature can be lowered to a temperature at which the occurrence of belt burn-in is suppressed within the interval time, and the belt burn-in can be satisfactorily suppressed.

  The interval time may be set when the number of times of obtaining a differential rotation number equal to or greater than a predetermined value after the elapse of the previously set interval time has reached a predetermined number.

  By setting the predetermined value and the predetermined number of times to appropriate numbers, it is possible to suppress frequent setting of the interval time, and it is possible to suppress frequent switching between the belt mode and the split mode.

  However, the predetermined value may be set to 0, or the predetermined number of times may be set to 1. That is, every time the belt mode and the split mode are switched, an interval time is set, and switching between the belt mode and the split mode within the interval time may be restricted.

  According to the present invention, it is possible to suppress heat generated by belt slippage from being accumulated in the belt. Therefore, it is possible to suppress the occurrence of belt burn-in caused by the slip of the belt when the belt mode and the split mode are switched.

It is a figure which shows the structure of the principal part of the vehicle by which the control apparatus which concerns on one Embodiment of this invention is mounted. It is a skeleton figure which shows the structure of the drive system of a vehicle. It is a figure which shows the state of each engagement element at the time of advance of a vehicle, and reverse drive. It is a collinear diagram which shows the relationship of the rotation speed (rotation speed) of the sun gear of a planetary gear mechanism, a carrier, and a ring gear. It is a figure which shows the relationship between a belt gear ratio and a unit gear ratio. It is a flowchart which shows the flow of the process at the time of mode switching. It is a flowchart which shows the flow of an interval process. It is a map which shows an example of the relationship between work rate, slip time, and interval time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Vehicle configuration>
FIG. 1 is a diagram illustrating a configuration of a main part of a vehicle 1 on which a control device according to an embodiment of the present invention is mounted.

  The vehicle 1 is an automobile that uses the engine 2 as a drive source.

  The engine 2 is provided with an electronic throttle valve for adjusting the amount of intake air into the combustion chamber of the engine 2, an injector (fuel injection device) that injects fuel into the intake air, and an ignition plug that generates electric discharge in the combustion chamber. It has been. The engine 2 is also provided with a starter for starting the engine 2. The output of the engine 2 is transmitted to driving wheels (for example, left and right front wheels) of the vehicle 1 via the torque converter 3 and the power split type continuously variable transmission 4.

  The vehicle 1 includes a plurality of ECUs (Electronic Control Units) including a CPU and a memory. The plurality of ECUs include a transmission ECU 11. Each ECU is connected so that bidirectional communication by a CAN (Controller Area Network) communication protocol is possible.

  A hydraulic pressure sensor 12, a primary rotation speed sensor 13, a secondary rotation speed sensor 14, and the like are connected to the transmission ECU 11.

  The hydraulic sensor 12 outputs a detection signal corresponding to the hydraulic pressure acting on the movable sheave 66 (see FIG. 2) of the secondary pulley 54 of the power split continuously variable transmission 4. The transmission ECU 11 acquires the hydraulic pressure acting on the movable sheave 66 from the detection signal of the hydraulic sensor 12.

  The primary rotational speed sensor 13 outputs, for example, a pulse signal synchronized with the rotation of the primary shaft 51 (see FIG. 2) of the power split continuously variable transmission 4 as a detection signal. The transmission ECU 11 converts the frequency of the pulse signal input from the primary rotational speed sensor 13 into the rotational speed (primary rotational speed) of the primary shaft 51.

  For example, the secondary rotational speed sensor 14 outputs a pulse signal synchronized with the rotation of the secondary shaft 52 (see FIG. 2) of the power split continuously variable transmission 4 as a detection signal. The transmission ECU 11 converts the frequency of the pulse signal input from the secondary rotational speed sensor 14 into the rotational speed of the secondary shaft 52 (secondary rotational speed).

  The transmission ECU 11 is a hydraulic circuit for supplying hydraulic pressure to each part of the power split continuously variable transmission 4 based on information acquired from detection signals of various sensors and / or various information input from other ECUs. The gear ratio of the power split type continuously variable transmission 4 is controlled by controlling various valves provided at 15.

  In the control of the gear ratio, for example, a shift diagram that defines the relationship between the accelerator opening (the amount of depression of the accelerator pedal), the vehicle speed, and the target rotational speed is used. The shift diagram is stored in the form of a map in a non-volatile memory (ROM, flash memory, EEPROM, or the like) of the transmission ECU 11. Information on the accelerator opening and the vehicle speed is input to the transmission ECU 11 from another ECU. The transmission ECU 11 sets a target rotational speed corresponding to the accelerator opening and the vehicle speed based on the shift map, and the rotational speed (turbine rotational speed) input to the power split continuously variable transmission 4 is the target rotational speed. So that the gear ratio of the power split type continuously variable transmission 4 is changed.

<Configuration of drive system>
FIG. 2 is a skeleton diagram showing the configuration of the drive system of the vehicle 1.

  The torque converter 3 includes a pump impeller 31, a turbine runner 32, and a lockup clutch 33. An E / G output shaft 21 is connected to the pump impeller 31, and the pump impeller 31 is provided so as to be integrally rotatable about the same rotation axis as the E / G output shaft 21. The turbine runner 32 is provided to be rotatable about the same rotation axis as the pump impeller 31. The lockup clutch 33 is provided to directly connect / separate the pump impeller 31 and the turbine runner 32. When the lockup clutch 33 is engaged, the pump impeller 31 and the turbine runner 32 are directly connected, and when the lockup clutch 33 is released, the pump impeller 31 and the turbine runner 32 are separated.

  When the E / G output shaft 21 is rotated in a state where the lockup clutch 33 is released, the pump impeller 31 rotates. When the pump impeller 31 rotates, an oil flow from the pump impeller 31 toward the turbine runner 32 is generated. This oil flow is received by the turbine runner 32 and the turbine runner 32 rotates. At this time, the amplifying action of the torque converter 3 occurs, and the turbine runner 32 generates a power larger than the power (torque) of the E / G output shaft 21.

  In a state where the lockup clutch 33 is engaged, when the E / G output shaft 21 is rotated, the E / G output shaft 21, the pump impeller 31, and the turbine runner 32 are rotated together.

  The power split type continuously variable transmission 4 includes an input shaft 41, an output shaft 42, a continuously variable transmission mechanism 43, a planetary gear mechanism 44, a split drive gear 45, a split driven gear 46, and a speed increase transmission mechanism 47.

  The input shaft 41 is connected to the turbine runner 32 of the torque converter 3 and is provided so as to be integrally rotatable about the same rotation axis as the turbine runner 32.

  The output shaft 42 is provided in parallel with the input shaft 41. An output gear 48 is supported on the output shaft 42 so as not to be relatively rotatable.

  The continuously variable transmission mechanism 43 has the same configuration as a known belt-type continuously variable transmission (CVT). Specifically, the continuously variable transmission mechanism 43 includes a primary shaft 51, a secondary shaft 52 provided in parallel with the primary shaft 51, a primary pulley 53 supported by the primary shaft 51 so as not to be relatively rotatable, and a secondary shaft 52. And a secondary pulley 54 supported so as not to rotate relative thereto, and a primary pulley 53 and a belt 55 wound around the secondary pulley 54.

  The primary pulley 53 is disposed so as to face the fixed sheave 61 fixed to the primary shaft 51 with the belt 55 sandwiched between the fixed sheave 61 and is supported by the primary shaft 51 so as to be movable in the axial direction but not to be relatively rotatable. 62. A cylinder (not shown) fixed to the primary shaft 51 is provided on the opposite side of the movable sheave 62 from the fixed sheave 61, and a piston chamber (oil chamber) is formed between the movable sheave 62 and the cylinder. Has been.

  The secondary pulley 54 is disposed so as to be opposed to the fixed sheave 65 fixed to the secondary shaft 52 with the belt 55 sandwiched between the fixed sheave 65 and supported on the secondary shaft 52 so as to be movable in the axial direction but not to be relatively rotatable. 66. A cylinder (not shown) fixed to the secondary shaft 52 is provided on the opposite side of the movable sheave 66 from the fixed sheave 65, and a piston chamber (oil chamber) is formed between the movable sheave 66 and the cylinder. Has been.

  Although not shown, the movable sheave 66 is biased toward the fixed sheave 65 by the elastic force of the bias spring for applying an initial clamping pressure (initial thrust) to the belt 55.

  In the continuously variable transmission mechanism 43, the hydraulic pressure (oil amount) supplied to the piston chambers of the primary pulley 53 and the secondary pulley 54 is controlled, and the groove widths of the primary pulley 53 and the secondary pulley 54 are changed. The belt speed ratio, which is the speed ratio in the continuously variable transmission mechanism 43, is continuously changed continuously.

  Specifically, when the belt speed ratio is lowered, the hydraulic pressure supplied to the piston chamber of the primary pulley 53 is increased. As a result, the movable sheave 62 of the primary pulley 53 moves to the fixed sheave 61 side, and the interval (groove width) between the fixed sheave 61 and the movable sheave 62 is reduced. Accordingly, the winding diameter of the belt 55 around the primary pulley 53 is increased, and the interval (groove width) between the fixed sheave 65 and the movable sheave 66 of the secondary pulley 54 is increased. As a result, the pulley ratio between the primary pulley 53 and the secondary pulley 54 is reduced, and the belt transmission ratio is reduced.

  When the belt transmission ratio is increased, the hydraulic pressure supplied to the piston chamber of the primary pulley 53 is decreased. Thereby, the thrust of the secondary pulley 54 with respect to the belt 55 becomes larger than the thrust of the primary pulley 53 with respect to the belt 55, the interval between the fixed sheave 65 and the movable sheave 66 of the secondary pulley 54 is reduced, and the fixed sheave 61 and the movable sheave The distance from 62 increases. As a result, the pulley ratio between the primary pulley 53 and the secondary pulley 54 is increased, and the belt transmission ratio is increased.

  On the other hand, the thrust of the primary pulley 53 and the secondary pulley 54 needs to be large enough to prevent slippage between the primary pulley 53 and the secondary pulley 54 and the belt 55. Therefore, the hydraulic pressure supplied to each piston chamber of the primary pulley 53 and the secondary pulley 54 is controlled so that a thrust according to the magnitude of the torque input to the input shaft 41 is obtained.

  The planetary gear mechanism 44 includes a sun gear 71, a carrier 72, and a ring gear 73. The sun gear 71 is supported by the secondary shaft 52 so as not to be relatively rotatable. The carrier 72 is fitted on the output shaft 42 so as to be relatively rotatable. The carrier 72 supports a plurality of pinion gears 74 in a rotatable manner. The plurality of pinion gears 74 are arranged on the circumference and mesh with the sun gear 71. The ring gear 73 has an annular shape that collectively surrounds the plurality of pinion gears 74, and meshes with each pinion gear 74 from the outer side in the rotational radial direction of the secondary shaft 52. An output shaft 42 is connected to the ring gear 73, and the ring gear 73 is provided so as to be integrally rotatable about the same rotation axis as the output shaft 42.

  The split drive gear 45 is fitted on the input shaft 41 so as to be relatively rotatable.

  The split driven gear 46 is provided so as to be integrally rotatable about the same rotation axis as the carrier 72 of the planetary gear mechanism 44.

  The speed increasing transmission mechanism 47 is configured to increase the rotation of the split drive gear 45 and transmit it to the split driven gear 46. Specifically, the speed increasing transmission mechanism 47 is supported by the idle shaft 81 provided in parallel with the input shaft 41 and the output shaft 42 and the idle shaft 81 so as not to be relatively rotatable, and meshes with the split drive gear 45. It includes a first idle gear 82 and a second idle gear 83 that is supported by the idle shaft 81 so as not to be relatively rotatable and meshes with the split driven gear 46. The first idle gear 82 has a smaller diameter and fewer teeth than the split drive gear 45, and the second idle gear 83 has a larger diameter and more teeth than the first idle gear 82.

  The power split type continuously variable transmission 4 includes an output gear mechanism 91 that transmits the rotation of the output gear 48 to the differential gear 6. The output gear mechanism 91 includes an output gear shaft 92 provided in parallel with the output shaft 42, a first output idle gear 93 that is supported by the output gear shaft 92 so as not to rotate relative to the output gear 48, and an output gear 48. A second output idle gear 94 that is supported by the gear shaft 92 so as not to rotate relative to the gear shaft 92 and meshes with the differential gear 6 (the input gear of the differential gear 6) is included.

  The power split type continuously variable transmission 4 includes clutches C1 and C2 and a brake B1.

  The clutch C1 is switched between an engaged state (on) in which the input shaft 41 and the split drive gear 45 are directly coupled (coupled so as to be integrally rotatable) and a released state (off) in which the direct coupling is released.

  The clutch C2 is switched between an engaged state (on) in which the sun gear 71 and the ring gear 73 of the planetary gear mechanism 44 are directly coupled (coupled so as to be integrally rotatable) and a released state (off) in which the direct coupling is released.

  The brake B <b> 1 is switched between an engaged state (on) in which the carrier 72 of the planetary gear mechanism 44 is braked and a released state (off) in which the rotation of the carrier 72 is allowed.

<Power transmission mode>
FIG. 3 is a diagram illustrating states of the clutches C1 and C2 and the brake B1 when the vehicle 1 moves forward and backward. FIG. 4 is a collinear diagram showing the relationship between the rotational speeds (rotational speeds) of the sun gear 71, the carrier 72, and the ring gear 73 of the planetary gear mechanism 44. FIG. 5 is a diagram showing the relationship between the belt transmission ratio and the unit transmission ratio, which is the overall transmission ratio of the power split type continuously variable transmission 4.

  In FIG. 3, “◯” indicates that the clutches C1 and C2 and the brake B1 are engaged. “X” indicates that the clutches C1 and C2 and the brake B1 are in the released state.

  The power split type continuously variable transmission 4 has a belt mode and a split mode as power transmission modes when the vehicle 1 moves forward.

  In the belt mode, as shown in FIG. 3, the clutch C1 and the brake B1 are released, and the clutch C2 is engaged. As a result, the split drive gear 45 is disconnected from the input shaft 41, the carrier 72 of the planetary gear mechanism 44 becomes free (free rotation state), and the sun gear 71 and the ring gear 73 of the planetary gear mechanism 44 are directly connected.

  The power input to the input shaft 41 rotates the primary shaft 51 of the continuously variable transmission mechanism 43 and rotates the primary pulley 53 integrally with the primary shaft 51. The rotation of the primary pulley 53 is transmitted to the secondary pulley 54 via the belt 55 to rotate the secondary pulley 54 and the secondary shaft 52. Since the sun gear 71 and the ring gear 73 of the planetary gear mechanism 44 are directly connected, the sun gear 71, the ring gear 73, and the output shaft 42 rotate together with the secondary shaft 52. Therefore, in the belt mode, as shown in FIG. 5, the unit speed ratio, which is the overall speed ratio of the power split continuously variable transmission 4, matches the belt speed ratio.

  In the split mode, as shown in FIG. 3, the clutch C1 is engaged, and the clutch C2 and the brake B1 are released. Thereby, the input shaft 41 and the split drive gear 45 are directly connected, the carrier 72 of the planetary gear mechanism 44 becomes free, and the sun gear 71 and the ring gear 73 of the planetary gear mechanism 44 are disconnected.

  Part of the power input to the input shaft 41 is transmitted to the primary shaft 51 of the continuously variable transmission mechanism 43, and is transmitted from the primary shaft 51 to the secondary shaft 52 via the primary pulley 53, the belt 55, and the secondary pulley 54, It is transmitted to the sun gear 71 of the planetary gear mechanism 44. On the other hand, a part of the power input to the input shaft 41 is accelerated and transmitted from the split drive gear 45 to the split driven gear 46 via the speed increasing transmission mechanism 47. As a result, the carrier 72 of the planetary gear mechanism 44 rotates integrally with the split driven gear 46.

  Since the split gear ratio, which is the gear ratio between the split drive gear 45 and the split driven gear 46, is constant and unchanged (fixed), in the split mode, if the power input to the input shaft 41 is constant, the planetary gear mechanism The rotation of the 44 carriers 72 is held at a constant speed. Therefore, when the belt speed ratio is increased, the rotational speed of the sun gear 71 of the planetary gear mechanism 44 is decreased, so that the rotational speed of the ring gear 73 (output shaft 42) of the planetary gear mechanism 44 is indicated by a broken line in FIG. Goes up. As a result, in the split mode, the unit transmission ratio decreases as the belt transmission ratio increases.

  The rotation of the output shaft 42 in the belt mode and the split mode is transmitted to the differential gear 6 via the output gear 48. Thereby, the drive shafts 7 and 8 of the vehicle 1 rotate in the forward direction.

  In the reverse mode for moving the vehicle 1 backward, as shown in FIG. 3, the clutches C1 and C2 are released and the brake B1 is engaged. Thereby, the split drive gear 45 is disconnected from the input shaft 41, the sun gear 71 and the ring gear 73 of the planetary gear mechanism 44 are disconnected, and the carrier 72 of the planetary gear mechanism 44 is braked.

  The power input to the input shaft 41 is transmitted to the secondary shaft 52 via the primary shaft 51, primary pulley 53, belt 55, and secondary pulley 54 of the continuously variable transmission mechanism 43, and the planetary gear mechanism is integrated with the secondary shaft 52. 44 sun gears 71 are rotated. Since the carrier 72 of the planetary gear mechanism 44 is braked, when the sun gear 71 rotates, the ring gear 73 of the planetary gear mechanism 44 rotates in the opposite direction to the sun gear 71. The rotation direction of the ring gear 73 is opposite to the rotation direction of the ring gear 73 during forward movement (belt mode and split mode). Then, the output shaft 42 rotates integrally with the ring gear 73. The rotation of the output shaft 42 is transmitted to the differential gear 6 via the output gear 48. Thereby, the drive shafts 7 and 8 of the vehicle 1 rotate in the reverse direction.

<Processing during mode switching>
FIG. 6 is a flowchart showing the flow of processing at the time of mode switching.

  In the control of the gear ratio of the power split type continuously variable transmission 4, there is a case where switching between the belt mode and the split mode (hereinafter simply referred to as “mode switching”) is required. The mode switching is achieved by switching the clutches C1 and C2, and is performed in a state where the belt speed ratio substantially matches the split speed ratio. That is, the hydraulic pressure supplied to the clutches C1 and C2 is controlled in a state where the belt gear ratio substantially matches the split gear ratio, and the released clutch C1 (engagement side) is engaged, and the engaged clutch By releasing C2 (release side), the belt mode is switched to the split mode. Conversely, the clutch C1 (release side) in the engaged state is released and the clutch C2 (engagement side) in the released state is engaged in a state where the belt speed ratio substantially matches the split speed ratio. Switch from mode to belt mode.

  When it is necessary to switch between the belt mode and the split mode, the transmission ECU 11 executes a mode switching process shown in FIG.

  In the mode switching process, it is determined whether or not the current time is within the interval time (step S1). The interval time is a time set by the interval process. The interval process will be described later.

  If the current time is within the interval time (YES in step S1), mode switching is prohibited (step S2).

  On the other hand, if the interval time has not been set and the current time is not within the interval time (NO in step S1), mode switching is permitted (step S3), and switching of the clutches C1 and C2 is started for mode switching. The

  Then, the interval process is executed (step S4), and the mode switching process is terminated.

<Interval processing>
FIG. 7 is a flowchart showing the flow of interval processing.

  In the interval process, it is determined whether or not an interval flag provided in the RAM of the transmission ECU 11 is on (step S11). The interval flag is a flag indicating whether or not to set an interval time at the next mode switching.

  When the interval flag is not on, that is, when the interval flag is off (NO in step S11), the differential rotational speed between the sun gear 71 of the planetary gear mechanism 44 and the carrier 72 is calculated (step S12). The differential rotational speed between the sun gear 71 and the carrier 72 is calculated by subtracting the rotational speed of the sun gear 71 from the rotational speed of the carrier 72. The rotational speed of the sun gear 71 is the same as the secondary rotational speed obtained from the output signal of the secondary rotational speed sensor 14. The rotation speed of the carrier 72 is calculated by dividing the primary rotation speed obtained from the output signal of the primary rotation speed sensor 13 by the split gear ratio.

  When the differential rotation speed is calculated, it is determined whether or not the differential rotation speed is greater than or equal to a predetermined value (step S13). The predetermined value may be set based on, for example, the differential rotational speed between the sun gear 71 and the carrier 72 that may cause the belt 55 to slip when the mode is switched.

  When the differential rotation speed is less than the predetermined value (NO in step S13), the subsequent processing is not performed and the interval processing is terminated.

  If the differential rotation speed is equal to or greater than the predetermined value (YES in step S13), the count value N of the differential rotation counter provided in the RAM of the transmission ECU 11 is incremented (step S14).

  Subsequently, it is determined whether or not the incremented count value N is a predetermined number or more (step S15). The predetermined number is based on the number of repetitions that may cause seizure of the belt 55 when mode switching is repeated in a state where a differential rotation of a predetermined value or more occurs between the sun gear 71 and the carrier 72. Should be set.

  If the count value N is less than the predetermined number (NO in step S15), the interval process is terminated.

  If the count value N is greater than or equal to the predetermined number (YES in step S15), the interval flag is turned on (step S16). That is, the interval flag is turned on when the number of times of mode switching reaches a predetermined number in a state where a differential rotational speed of a predetermined value or more is generated between the sun gear 71 and the carrier 72.

  After the interval flag is turned on, the count value N of the differential rotation counter is reset to 0 (step S17), and the interval process ends.

  On the other hand, when the interval flag is on (step S11), the belt transmission torque capacity is calculated (step S18). The belt transmission torque capacity can be calculated from the belt speed ratio, the turbine speed, and the clamping pressure applied to the belt 55. The clamping pressure is obtained by multiplying the hydraulic pressure supplied to the secondary pulley 54 by the area of the movable sheave 66 of the secondary pulley 54 that receives the hydraulic pressure (pressure receiving area), and the multiplied hydraulic pressure acts on the movable sheave 66 and the secondary pulley. It is calculated by adding the spring force of 54 bias springs. The oil pressure supplied to the secondary pulley 54 is detected by the oil pressure sensor 12 (see FIG. 1). The pressure receiving area of the movable sheave 66, the centrifugal hydraulic pressure acting on the movable sheave 66, and the spring force of the bias spring are values determined by the configuration of the secondary pulley 54, and are known values.

  Further, the differential rotation speed between the sun gear 71 and the carrier 72 is calculated (step S19). The method of calculating the differential rotation speed is as described above.

  Thereafter, the work rate due to the slip of the belt 55 is calculated. The power (kW) is calculated by multiplying the product of the belt transmission torque capacity (N · m) and the differential rotation speed (rpm) by 2π / 60 for unit conversion.

  Further, the slip time is calculated (step S20). The slip time is a time during which a transient state in which both the clutches C1 and C2 are engaged while slipping during the clutch C1 and C2 switching is continued, specifically, toward the engagement side of the clutches C1 and C2. This is the time from when the hydraulic pressure supply is started until the hydraulic pressure supplied to the release side is reduced to zero.

  Thereafter, an interval time corresponding to the work rate and the slip time is set (step S21). The relationship between the work rate, slip time, and interval time is stored in the form of a map in the nonvolatile memory of the transmission ECU 11. An example of the map is shown in FIG. 8, and is created so that the interval time is set longer as the work rate is larger and the slip time is longer. Numerical values not shown on the map may be obtained by interpolation, for example. By multiplying the work rate and the slip time, the amount of heat (heat generation amount) generated by the slip of the belt 55 can be calculated. Therefore, the interval time set according to the work rate and the slip time is the slip time of the belt 55. It is time according to the calorific value by.

  When the interval time is set, the interval time starts immediately (step S22). That is, the interval time starts simultaneously with the setting. When the interval time is started, a timer for measuring the elapsed time from the start is started. When the time measured by the timer coincides with the interval time, the interval time ends.

  Note that the concept of “simultaneous” is not a strict one. For example, even if there is a processing time lag from the setting of the interval time to the start of the timer, when the interval time is set and when the interval time starts ( At the start of the interval).

  After the start of the interval time, the interval flag is turned off (step S23), and the interval process is ended.

<Effect>
As described above, the differential rotation speed generated between the sun gear 71 and the carrier 72 at the time of mode switching is acquired, and the interval time is set based on the differential rotation speed. When the interval time is set, mode switching is limited until the interval time elapses.

  When the belt mode and the split mode are switched while the differential rotation occurs between the sun gear 71 and the carrier 72 and the belt 55 slips, frictional heat is generated in the belt 55. Since the mode switching is limited within the interval time, the generation of frictional heat due to the slip of the belt 55 is suppressed. Therefore, by setting the interval time, the temperature of the belt 55 can be lowered, and the occurrence of seizure of the belt 55 can be suppressed. Further, since the frequency of occurrence of slippage of the belt 55 is reduced, abnormal wear of the belt 55 can be suppressed.

  The interval time is set to a time according to the amount of heat generated by the belt 55 slipping. Specifically, the interval time is set to be longer as the calorific value is larger. As a result, the temperature of the belt 55 can be lowered to a temperature at which the occurrence of seizure of the belt 55 is suppressed within the interval time. Therefore, image sticking of the belt 55 can be satisfactorily suppressed.

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, in the above-described embodiment, the next mode switching is performed when the number of times the mode switching has been performed in a state where a differential rotational speed greater than or equal to a predetermined value occurs between the sun gear 71 and the carrier 72. It is assumed that the interval time is set at the time. Instead, a configuration may be employed in which an interval time is set at the next mode switching when the number of mode switching performed within a predetermined time reaches a predetermined number.

  Further, the interval time may be set every time the mode is switched.

  The start of the interval time is assumed to be simultaneous with the setting of the interval time, but may be the time when a predetermined time has elapsed since the setting of the interval time.

  Although the interval time is set according to the work rate (differential rotation speed, belt transmission torque capacity) and the slip time, it may be set according to other parameters in addition to the work rate and the slip time.

  For example, since each part of the power split type continuously variable transmission 4 is cooled by supplying oil (lubricating oil), the lower the oil temperature, the shorter the interval time is set (the higher the oil temperature, the longer the interval time). It may be set for a long time).

  In the configuration in which the oil pump is driven by the engine 2, the higher the rotational speed of the engine 2, the higher the capacity of the oil pump. Therefore, the higher the rotational speed of the engine 2, the shorter the interval time is set. The lower the number, the longer the interval time may be set).

  The higher the air temperature in the engine compartment, the higher the temperature of each part of the power split type continuously variable transmission 4, and the lower the temperature of each part, the more easily the belt 55 reaches the temperature at which seizure occurs. Therefore, the interval time may be set longer as the temperature in the engine compartment is higher.

  Further, the interval time may be changed between when the belt mode is switched to the split mode and when the split mode is switched to the belt mode. For example, when switching from the belt mode to the split mode, the interval time may be set shorter than when switching from the split mode to the belt mode. Since the mode switching performed after switching from the belt mode to the split mode is switching from the split mode to the belt mode, switching from the split mode to the belt mode is prohibited if the interval time is set to a short time. It becomes difficult to be done. Thus, switching from the split mode to the belt mode is performed, and the unit transmission ratio (belt transmission ratio) is increased, so that the torque transmitted to the drive wheels of the vehicle 1 can be quickly increased. As a result, the acceleration performance of the vehicle 1 can be improved.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

4 Power split type continuously variable transmission 11 Transmission ECU (mode switching means, interval time setting means, switching restriction means)
41 Input shaft 42 Output shaft 43 Continuously variable transmission mechanism 44 Planetary gear mechanism 45 Split drive gear (split transmission mechanism)
46 Split driven gear (split transmission mechanism)
47 Speed increase transmission mechanism (split transmission mechanism)
71 Sun gear 72 Carrier 73 Ring gear C1 Clutch (first engagement element)
C2 clutch (second engagement element)

Claims (1)

A planetary gear mechanism having an input shaft, an output shaft, a sun gear, a carrier and a ring gear, wherein the ring gear is provided so as to rotate integrally with the output shaft, and the power input to the input shaft is steplessly A belt-type continuously variable transmission mechanism that changes the speed and transmits it to the sun gear, a split transmission mechanism that changes the power input to the input shaft at a constant transmission ratio and transmits it to the carrier, and the split transmission mechanism A first engagement element engaged / released to switch transmission / cut-off of power to the carrier, and a first engagement element engaged / released to couple / separate the sun gear and the ring gear so as to be integrally rotatable. A control device used in a power split continuously variable transmission having a configuration including two engaging elements,
A belt mode in which the first engagement element is released and the second engagement element is engaged; and the first engagement element is engaged and the second engagement element is released. Mode switching means for switching between split mode;
When the mode switching means switches between the belt mode and the split mode, a differential rotational speed generated between the sun gear and the carrier is acquired, and an interval time is set based on the acquired differential rotational speed. Interval time setting means;
After the interval time is set by the interval time setting means, the switching of the belt mode and the split mode by the mode switching means is restricted from the start of a predetermined interval until the set interval time elapses. And a switching restricting means.

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