JP2017082897A - Control device of power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a fixed member which prohibits the movement of a movable sheave of a primary pulley when traveling with a gear change ratio of a continuously variable transmission as a maximum gear change ratio.SOLUTION: When traveling with a gear change ratio γ of a continuously variable transmission 26 as a maximum gear change ratio γmax, primary pressure Pin is applied so that a value of a pulley hydraulic pressure ratio Pr becomes not larger than a prescribed value within a range in which the maximum gear change ratio γmax is maintained, and thrust for moving a movable sheave 36b of a primary pulley 36 to a side opposite to a nut 90 side is thereby made to act on the movable sheave 36b. Therefore, a belt reaction force inputted to the nut 90 is suppressed, and the stress of the nut 90 is lowered. Furthermore, a variation of the belt reaction force inputted to the nut 90 is alleviated by a damping effect generated by the primary pressure Pin, and a variation of the stress of the nut 90 is also alleviated. By this constitution, when traveling with the gear change ratio γ of the continuously variable transmission 26 as the maximum gear change ratio γmax, the durability of the nut 90 can be improved.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a control device for a power transmission device including a continuously variable transmission of a type in which a transmission element is wound between pulleys.

  It has a primary pulley provided on the input shaft, a secondary pulley provided on the output shaft, and transmission elements (for example, belts and chains) wound around the pulleys, and transmits the power of the driving force source to the driving wheels. A power transmission device including a continuously variable transmission and a hydraulic control circuit that supplies each pulley hydraulic pressure to each pulley is well known. For example, the continuously variable transmission for vehicles described in patent document 1 is it. In such a continuously variable transmission, each pulley has a fixed sheave and a movable sheave, and the groove width of the pulley is changed by the movement of the movable sheave in the axial direction to change the gear ratio. In such a continuously variable transmission, the groove width of the primary pulley is maximized, so that the gear ratio is the largest (that is, the lowest gear ratio on the lowest vehicle speed side (low side)). . When the transmission gear ratio of the continuously variable transmission is set to the maximum transmission gear ratio, secondary pulley hydraulic pressure is applied to the secondary pulley to prevent slippage of the transmission element, but primary pulley hydraulic pressure must be applied to the primary pulley. Absent. In other words, the hydraulic cylinder of the primary pulley is fixed by the fixing member so as not to move in the axial direction of the input shaft, and the movable sheave of the primary pulley is fixed in the axial direction of the input shaft by not being applied with the primary pulley hydraulic pressure. Movement in the direction of the member side is blocked by the fixed member, and the speed ratio of the continuously variable transmission is set to the maximum speed ratio.

JP 2007-177833 A

  By the way, when the gear ratio of the continuously variable transmission is the maximum gear ratio, the reaction force of the transmission element is input to the fixed member that prevents the movement of the movable sheave of the primary pulley via the movable sheave of the primary pulley and the hydraulic cylinder. . Further, the reaction force of the transmission element is greater on the side where the transmission element is applied to the primary pulley than on the side where it is not applied. Therefore, the stress of the fixing member accompanying the input of the reaction force of the transmission element does not become a constant value, but fluctuates across the average value. When the stress of the fixing member fluctuates, it is considered that the load on the fixing member increases as compared with the case where the stress is constant. For this reason, when the speed ratio of the continuously variable transmission is the maximum speed ratio, there is a possibility that the situation is not favorable for the durability of the fixed member.

  The present invention has been made against the background of the above circumstances. The purpose of the present invention is to prevent the movement of the movable sheave of the primary pulley when traveling with the transmission gear ratio of the continuously variable transmission as the maximum transmission gear ratio. Another object of the present invention is to provide a control device for a power transmission device that can improve the durability of the fixing member.

  The gist of the first invention is that: (a) a driving force source having a primary pulley provided on an input shaft, a secondary pulley provided on an output shaft, and a transmission element wound around each pulley; A continuously variable transmission that transmits the motive power to the drive wheels, and a hydraulic control circuit that supplies each pulley hydraulic pressure to each pulley, and the hydraulic cylinder of the primary pulley is fixed in the axial direction of the input shaft by a fixing member. The secondary pulley hydraulic pressure for preventing the transmission element from slipping is applied, and the primary pulley hydraulic pressure is not applied to move the movable sheave of the primary pulley toward the fixed member. In the state blocked by the fixing member, the control device of the power transmission device in which the transmission ratio of the continuously variable transmission is set to the maximum transmission ratio, and (b) the transmission ratio of the continuously variable transmission Shift control for applying the primary pulley oil pressure so that the value of the ratio of the secondary pulley oil pressure to the primary pulley oil pressure is not more than a predetermined value within a range in which the maximum gear ratio can be maintained when traveling at the maximum gear ratio. To include a part.

  According to the first aspect of the present invention, when traveling with the continuously variable transmission as the maximum transmission ratio, the ratio of the secondary pulley hydraulic pressure to the primary pulley hydraulic pressure is a predetermined value within a range in which the maximum transmission ratio can be maintained. Since the primary pulley hydraulic pressure is applied as described below, a thrust for moving the movable sheave of the primary pulley to the side opposite to the fixed member side is applied to the movable sheave. Therefore, the reaction force of the transmission element input to the fixing member is suppressed, and the stress of the fixing member is reduced. Further, due to the damping effect by the primary pulley hydraulic pressure, fluctuations in the reaction force of the transmission element input to the fixing member are alleviated, and fluctuations in the stress of the fixing member are also alleviated. Therefore, the durability of the fixed member that prevents the movement of the movable sheave of the primary pulley can be improved when traveling with the speed ratio of the continuously variable transmission as the maximum speed ratio.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the schematic structure of the vehicle to which this invention is applied, and is a figure explaining the principal part of the control function and various control systems for various control in a vehicle. It is sectional drawing which expands and shows a primary pulley among continuously variable transmissions. It is a figure which shows an example of the distortion of the nut accompanying the input of a belt reaction force. It is a figure which shows an example of the average distortion of a nut. It is a figure which shows an example of the distortion amplitude of a nut. Explains the control operation for improving the durability of the nut that prevents the movement of the movable sheave of the primary pulley when traveling with the main control ratio of the electronic control unit, that is, the gear ratio of the continuously variable transmission as the maximum gear ratio. It is a flowchart to do. It is sectional drawing which expands and shows a primary pulley among continuously variable transmission, Comprising: It is a figure which shows the embodiment different from FIG.

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

  FIG. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrates a control function for various controls in the vehicle 10 and a main part of a control system. In FIG. 1, a vehicle 10 includes an engine 12 as a driving force source for traveling, drive wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14. Yes. The power transmission device 16 is connected to a known torque converter 18 as a fluid transmission device connected to the engine 12, a turbine shaft 20 connected to the torque converter 18, and a turbine shaft 20 in a case 17 as a non-rotating member. The forward / reverse switching device 22, the input shaft 24 connected to the forward / reverse switching device 22, the continuously variable transmission 26 connected to the input shaft 24, the output shaft 28 connected to the continuously variable transmission 26, and the reduction gear device 30 and a differential gear device 32 and the like. In the power transmission device 16 configured as described above, the power of the engine 12 (the torque and the force are synonymous unless otherwise distinguished) is the torque converter 18, the forward / reverse switching device 22, the continuously variable transmission 26, and the reduction gear device 30. Then, it is transmitted to the left and right drive wheels 14 sequentially through the differential gear device 32 and the like.

  The torque converter 18 includes a pump impeller 18 p connected to the engine 12 and a turbine impeller 18 t connected to the turbine shaft 20. The pump impeller 18p controls the speed of the continuously variable transmission 26, generates a belt clamping pressure in the continuously variable transmission 26, or switches the operation of each of the forward clutch C1 and the reverse brake B1 described later. A mechanical oil pump 34 is connected, which is generated by rotationally driving the hydraulic pressure for supplying lubricating oil to each part of the power transmission device 16 by the engine 12.

  The forward / reverse switching device 22 includes a double pinion type planetary gear device 22p, a forward clutch C1, and a reverse brake B1. The sun gear 22s of the planetary gear device 22p is connected to the turbine shaft 20, the carrier 22c of the planetary gear device 22p is connected to the input shaft 24, and the ring gear 22r of the planetary gear device 22p is selectively connected to the case 17 via the reverse brake B1. It is connected to. The carrier 22c and the sun gear 22s are selectively connected via the forward clutch C1. The forward clutch C1 and the reverse brake B1 are known hydraulic friction engagement devices. In the forward / reverse switching device 22 configured as described above, when the forward clutch C1 is engaged and the reverse brake B1 is released, a forward power transmission path is formed. When the reverse brake B1 is engaged and the forward clutch C1 is released, a reverse power transmission path is formed. When both the forward clutch C1 and the reverse brake B1 are released, the forward / reverse switching device 22 is in a neutral state (power transmission cut-off state) in which power transmission is cut off. Thus, the forward clutch C1 and the reverse brake B1 are hydraulic engagement devices that connect and disconnect the power transmission path between the engine 12 and the continuously variable transmission 26.

  The continuously variable transmission 26 includes a primary pulley 36 with a variable effective diameter provided on the input shaft 24, a secondary pulley 38 with a variable effective diameter provided on the output shaft 28, and the pulleys 36, 38. A belt-type non-rotating belt that transmits a power of the engine 12 to the drive wheel 14 side through a frictional force between the pulleys 36 and 38 and the transmission belt 40. It is a step transmission.

  The primary pulley 36 includes a fixed sheave 36a coupled to the input shaft 24, and a movable sheave 36b provided so as not to rotate relative to the shaft portion of the fixed sheave 36a around the axis C1 and to move in the direction of the axis C1. And a hydraulic actuator 36c for applying a primary thrust Win (= primary pressure Pin × pressure receiving area) in the primary pulley 36 for changing the V groove width between the sheaves 36a and 36b. Further, the secondary pulley 38 is provided with a fixed sheave 38a provided integrally with the output shaft 28, and is not rotatable relative to the shaft portion of the fixed sheave 38a around the axis C2 and is movable in the direction of the axis C2. The movable sheave 38b and a hydraulic actuator 38c that applies a secondary thrust Wout (= secondary pressure Pout × pressure receiving area) in the secondary pulley 38 for changing the V groove width between the sheaves 38a and 38b. . The primary pressure Pin is a primary pulley hydraulic pressure supplied to the hydraulic actuator 36c by the hydraulic control circuit 50 provided in the power transmission device 16, and the secondary pressure Pout is a secondary pulley supplied to the hydraulic actuator 38c by the hydraulic control circuit 50. It is hydraulic. The oil pressures Pin and Pout are pulley oil pressures that apply thrusts Win and Wout that press the movable sheaves 36b and 38b toward the fixed sheaves 36a and 38a, respectively.

  In the continuously variable transmission 26, the primary pressure Pin and the secondary pressure Pout are respectively regulated by the hydraulic pressure control circuit 50, whereby the primary thrust Win and the secondary thrust Wout are respectively controlled. As a result, the V-groove widths of the pulleys 36 and 38 are changed to change the engagement diameter (effective diameter) of the transmission belt 40, and the transmission gear ratio (gear ratio) γ (= input shaft rotational speed Nin / output shaft rotational speed Nout). ) And the frictional force between the pulleys 36, 38 and the transmission belt 40 (that is, the clamping pressure; hereinafter referred to as belt clamping pressure) is controlled so that the transmission belt 40 does not slip. That is, by controlling the primary pressure Pin (the primary thrust Win is also agreed) and the secondary pressure Pout (the secondary thrust Wout is also agreed), the actual speed ratio γ is set to the target speed ratio γtgt while preventing the transmission belt 40 from slipping. Is done.

  In the continuously variable transmission 26, for example, when the primary pressure Pin is increased, the V groove width of the primary pulley 36 is narrowed to reduce the speed ratio γ, that is, the continuously variable transmission 26 is upshifted. When the primary pressure Pin is lowered, the V groove width of the primary pulley 36 is widened to increase the gear ratio γ, that is, the continuously variable transmission 26 is downshifted. Therefore, when the V-groove width of the primary pulley 36 is minimized, the minimum speed ratio γmin (the speed ratio on the highest vehicle speed side, the highest Hi) is formed as the speed ratio γ of the continuously variable transmission 26. Further, when the V-groove width of the primary pulley 36 is maximized, the maximum speed ratio γmax (the speed ratio on the lowest vehicle speed side, the lowest) is formed as the speed ratio γ of the continuously variable transmission 26. The target speed ratio γtgt is realized by the mutual relationship between the primary thrust Win and the secondary thrust Wout, while the primary pressure Pin and the secondary pressure Pout prevent the transmission belt 40 from slipping (belt slip). The target gear shift is not realized only by one pulley hydraulic pressure (thus agreeing with thrust).

  The vehicle 10 includes an electronic control device 60 including a control device for the power transmission device 16. The electronic control unit 60 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM and follows a program stored in the ROM in advance. Various controls of the vehicle 10 are executed by performing signal processing. For example, the electronic control unit 60 is adapted to execute output control of the engine 12, shift control including belt clamping pressure control of the continuously variable transmission 26, etc., for engine control, hydraulic control, etc. as necessary. It is divided into two parts.

  The electronic control unit 60 includes various actual values (for example, engine rotational speed Ne, turbine, etc.) based on detection signals from various sensors (for example, various rotational speed sensors 70, 72, 74, 76, accelerator opening sensor 78, etc.) provided in the vehicle 10. Rotational speed Nt, input shaft rotational speed Nin, output shaft rotational speed Nout corresponding to vehicle speed V, accelerator opening degree θacc, etc.) are supplied. Further, the electronic control device 60 outputs various output signals (for example, an engine output control command signal Se for controlling the output of the engine 12) to each device (for example, the engine 12, the hydraulic control circuit 50, etc.) provided in the vehicle 10. A hydraulic control command signal Sccvt for hydraulic control related to the shift of the step transmission 26, a hydraulic control command signal Sclt for hydraulic control related to the engagement operation of the forward clutch C1 and the reverse brake B1, and the like.

  FIG. 2 is an enlarged sectional view of the primary pulley 36 in the continuously variable transmission 26. In FIG. 2, the primary pulley 36 is supported by a case 17 (not shown in FIG. 2) via bearings 80 and 82 so as to be rotatable around an axis C1. The hydraulic actuator 36 c of the primary pulley 36 adopts a double piston structure, includes a hydraulic cylinder 84, and has two oil chambers 86 and 88 in series in the hydraulic cylinder 84. The movable sheave 36b is pressed toward the fixed sheave 36a by the primary thrust Win generated by the primary pressure Pin supplied to the oil chambers 86 and 88 (see the two-dot chain line). The hydraulic cylinder 84 of the primary pulley 36 is fixed so as not to move in the direction of the axis C of the input shaft 24 by a nut 90 as a fixing member. Therefore, as shown by the solid line in FIG. 2, the movable sheave 36b is prevented from moving in the direction of the nut 90 in the direction of the axis C1 by the nut 90. In this state, the V The groove width is the maximum. In order to achieve this state, it is not necessary to apply the primary pressure Pin to the hydraulic actuator 36c, and the secondary pressure Pout for preventing belt slipping may be supplied to the hydraulic actuator 38c of the secondary pulley 38. Therefore, the continuously variable transmission 26 is applied with the secondary pressure Pout for preventing belt slippage, and the primary pressure Pin is not applied, so that the movement of the movable sheave 36b of the primary pulley 36 toward the nut 90 side is prevented. In this state, the speed ratio γ of the continuously variable transmission 26 is set to the maximum speed ratio γmax.

  Returning to FIG. 1, the electronic control unit 60 includes an engine output control unit, that is, an engine output control unit 62, and a shift control unit, that is, a shift control unit 64.

  The engine output control unit 62 sets a target engine torque Tetgt for obtaining a driving force (driving torque) corresponding to the accelerator opening θacc, and a throttle signal, an injection signal, and an ignition so as to obtain the target engine torque Tetgt. An engine output control command signal Se such as a timing signal is output to a throttle actuator, a fuel injection device, and an ignition device, respectively.

  The shift control unit 64 is configured to control the primary pressure based on the accelerator opening Acc and the vehicle speed V so as to achieve the target speed ratio γtgt of the continuously variable transmission 26 while preventing belt slippage of the continuously variable transmission 26. A target value of Pin (hereinafter referred to as target primary pressure Pintgt) and a target value of secondary pressure Pout (hereinafter referred to as target secondary pressure Pouttgt) are determined, and hydraulic control corresponding to the target primary pressure Pintgt and target secondary pressure Pouttgt, respectively. Command signal Sccv is output to hydraulic control circuit 50.

  Specifically, the shift control unit 64 applies the vehicle speed V and the accelerator opening degree Acc to a relationship (for example, a shift map) that is obtained and stored experimentally or in advance (ie, a predetermined shift map). To set the target input shaft rotational speed Nintgt. The speed change control unit 64 calculates a target speed ratio γtgt (= Nintgt / Nout) based on the target input shaft rotational speed Nintgt. Further, the shift control unit 64 sets the target secondary pressure Pouttgt by applying the gear ratio γ and the input torque Tin of the continuously variable transmission 18 to a predetermined relationship (for example, belt clamping pressure map). The shift control unit 64 calculates a target secondary thrust Wouttgt (= Pouttgt × pressure receiving area) based on the target secondary pressure Pouttgt. The transmission control unit 64 applies the target transmission ratio γtgt to a predetermined relationship (thrust ratio map) between the target transmission ratio γtgt and the thrust ratio τ (= Wout / Win) for realizing the target transmission ratio γtgt. To calculate the thrust ratio τ. The shift control unit 64 calculates the target primary thrust Wintgt (= Wouttgt / τ) based on the calculated thrust ratio τ and the target secondary thrust Wouttgt. The shift control unit 64 calculates a target primary pressure Pintgt (= Wintgt / pressure receiving area) based on the target primary thrust Wintgt. The shift control unit 64 determines the primary command oil pressure Pins from which the target primary pressure Pintgt is obtained and the secondary command oil pressure Pouts from which the target secondary pressure Pinutgt is obtained by, for example, feedforward control, and uses the primary command oil pressure Pins and the secondary command oil pressure Pouts as oil pressure. The control command signal Scvt is output to the hydraulic control circuit 50. The hydraulic control circuit 50 regulates the primary pressure Pin and the secondary pressure Pout in accordance with the hydraulic control command signal Sccv. The primary command oil pressure Pins may be corrected by feedback control so that the speed ratio γ matches the target speed ratio γtgt. The secondary command oil pressure Pouts may be corrected by feedback control so that the detected value of the secondary pressure Pout by the secondary pressure sensor matches the target secondary pressure Pouttgt.

  Here, the durability of the nut 90 in the primary pulley 36 will be described with reference to FIG. When the transmission gear ratio γ of the continuously variable transmission 26 is the maximum transmission gear ratio γmax, the movable sheave 36b is prevented from moving in the direction of the nut 90 by the nut 90. The reaction force of the transmission belt 40 (hereinafter referred to as belt reaction force; see arrow A in the figure) is input to the nut 90. Along with this, strain (stress) is generated in the nut 90. Originally, the initial axial force (see arrow B in the figure) accompanying the nut fastening is input to the nut 90. The belt reaction force increases as the belt clamping pressure corresponding to the input torque Tin of the continuously variable transmission 18 increases. If the belt clamping pressure of the continuously variable transmission 26 increases, a belt reaction force exceeding the initial axial force is input to the nut 90. Further, the belt reaction force is greater on the side where the transmission belt 40 is not applied than on the side where the transmission belt 40 is not applied. Therefore, as shown in FIG. 3, the distortion of the nut 90 due to the input of the belt reaction force does not become a constant value, but fluctuates with an average distortion in between, so this fluctuation appears as a distortion amplitude of the nut 90. . It is considered that the load on the nut 90 increases as the strain amplitude of the nut 90 increases. For this reason, when the speed ratio γ of the continuously variable transmission 26 is the maximum speed ratio γmax, the nut 90 is not in a preferable traveling state in terms of durability.

  It is considered that the durability of the nut 90 is improved if the average strain of the nut 90 is reduced. As shown in FIG. 4, the average strain of the nut 90 increases as the secondary pressure Pout increases, and increases as the primary pressure Pin increases. Therefore, reducing the average distortion of the nut 90 may lead to a reduction in the belt clamping pressure of the continuously variable transmission 26, which may make it difficult to prevent belt slippage.

  On the other hand, it is considered that the durability of the nut 90 is also improved by suppressing the strain amplitude of the nut 90. As shown in FIG. 5, the strain amplitude of the nut 90 increases as the secondary pressure Pout increases, but decreases as the primary pressure Pin increases. When the primary pressure Pin is increased, the average strain of the nut 90 is increased, but the increase of the average strain is moderate, and the strain amplitude of the nut 90 is sharply reduced as compared with the increase of the load of the nut 90 due to the increase of the average strain. Therefore, the load reducing effect of the nut 90 is greater.

  Incidentally, as described above, when the speed ratio γ of the continuously variable transmission 26 is set to the maximum speed ratio γmax, it is not necessary to supply the primary pressure Pin. In other words, by supplying the primary pressure Pin, there is a possibility that the speed ratio γ of the continuously variable transmission 26 cannot be maintained at the maximum speed ratio γmax. The thrust ratio τ (= Wout / Win) for realizing the target gear ratio γtgt is determined in advance. The larger the thrust ratio τ, the larger the gear ratio γ (that is, the continuously variable transmission 26 is reduced). Shifted). That is, there is a minimum value of the thrust ratio τ that can maintain the maximum speed ratio γmax. If the primary pressure Pin is supplied, the thrust ratio τ is reduced, but if the value is equal to or greater than the minimum thrust ratio τ, the maximum speed ratio γmax can be maintained. Therefore, the primary pressure Pin is supplied within a range in which the maximum speed ratio γmax can be maintained, and the distortion amplitude of the nut 90 is reduced. As can be seen from FIG. 5, the greater the secondary pressure Pout, the more the strain pressure of the nut 90 cannot be reduced unless the primary pressure Pin is increased. The value of the ratio of the secondary pressure Pout to the primary pressure Pin (hereinafter referred to as pulley hydraulic pressure ratio Pr (= Pout / Pin)) is set to a predetermined value or less to reduce the strain amplitude of the nut 90. This predetermined value is, for example, an upper limit value of a predetermined pulley hydraulic pressure ratio Pr for sufficiently obtaining the effect of improving the load on the nut 90.

  When traveling with the speed ratio γ of the continuously variable transmission 26 set to the maximum speed ratio γmax, the speed change control unit 64 keeps the maximum speed ratio γmax within the range in which the maximum speed ratio γmax can be maintained, The primary pressure Pin is applied. That is, the speed change control unit 64, during traveling at the maximum speed ratio γmax, sets the value of the pulley hydraulic pressure ratio Pr to a value equal to or greater than the value of the pulley hydraulic ratio Pr that is the minimum thrust ratio τ value that can maintain the maximum speed ratio γmax. In addition, a hydraulic pressure control command signal Sccv for applying the primary pressure Pin is output to the hydraulic pressure control circuit 50 so as to be equal to or less than the predetermined value.

  FIG. 6 shows the main part of the control operation of the electronic control unit 60, that is, the nut 90 that prevents the movement of the movable sheave 36b of the primary pulley 36 when traveling with the speed ratio γ of the continuously variable transmission 26 set to the maximum speed ratio γmax. 5 is a flowchart for explaining a control operation for improving durability, and is repeatedly executed, for example, while the vehicle 10 is traveling.

  In FIG. 6, first, in step (hereinafter, step is omitted) S10 corresponding to the function of the speed change control unit 64, it is determined whether or not the speed ratio γ of the continuously variable transmission 26 is the maximum speed ratio γmax. . Alternatively, it may be determined whether the target speed ratio γtgt of the continuously variable transmission 26 is the maximum speed ratio γmax. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is affirmative, in S20 corresponding to the function of the shift control unit 64, the primary pressure Pin is set so that the value of the pulley hydraulic pressure ratio Pr is equal to or less than the predetermined value within a range where the maximum gear ratio γmax can be maintained. Is granted.

  As described above, according to this embodiment, when traveling with the transmission gear ratio γ of the continuously variable transmission 26 set to the maximum transmission gear ratio γmax, the value of the pulley hydraulic pressure ratio Pr is within the range in which the maximum transmission gear ratio γmax can be maintained. Since the primary pressure Pin is applied so as to be equal to or less than the predetermined value, a thrust for moving the movable sheave 36b of the primary pulley 36 to the side opposite to the nut 90 side is applied to the movable sheave 36b. Therefore, the belt reaction force input to the nut 90 is suppressed, and the stress of the nut 90 is reduced. Further, due to the damping effect by the primary pressure Pin, fluctuations in the belt reaction force input to the nut 90 are alleviated, and fluctuations in the stress of the nut 90 are also alleviated. Therefore, when traveling with the speed ratio γ of the continuously variable transmission 26 set to the maximum speed ratio γmax, the durability of the nut 90 that prevents the movement of the movable sheave 36b of the primary pulley 36 can be improved.

  Further, according to the present embodiment, the belt reaction force is suppressed, and the wear and buckling of the piston in the hydraulic actuator 36c of the primary pulley 36 can be reduced by the damping effect by the primary pressure Pin. Since the stress of the nut 90 is reduced and the fluctuation of the stress of the nut 90 is alleviated, the load on the nut 90 is alleviated and the durability of the screw portion including the nut 90 is improved. Thereby, the structure of a screw part can be simplified and the freedom degree of the structure increases.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the hydraulic actuator 36c of the primary pulley 36 employs a double piston structure and has the two oil chambers 86 and 88 in series in the hydraulic cylinder 84. Absent. FIG. 7 is an enlarged cross-sectional view of the primary pulley 36, showing an embodiment different from FIG. In FIG. 7, the hydraulic actuator 36 c of the primary pulley 36 includes a hydraulic cylinder 92 and has one oil chamber 94 in the hydraulic cylinder 92. The movable sheave 36b is pressed toward the fixed sheave 36a by the primary thrust Win generated by the primary pressure Pin supplied to the oil chamber 94. Further, the hydraulic cylinder 92 is fixed so as not to move in the direction of the axis C of the input shaft 24 by the nut 90 in a state of contacting the nut 90. Further, the movable sheave 36b is in contact with the hydraulic cylinder 92 and is prevented from moving in the direction of the nut 90 in the direction of the axis C1 by the nut 90, and the V groove width of the primary pulley 36 is maximized. The present invention can be applied even to the primary pulley 36 having a structure as shown in FIG.

  In the above-described embodiment, the primary pressure Pin is applied when traveling with the speed ratio γ of the continuously variable transmission 26 set to the maximum speed ratio γmax, but this is not a limitation. For example, when the vehicle is traveling at the maximum gear ratio γmax and the input torque Tin of the continuously variable transmission 18 that is in an unfavorable traveling state due to the durability of the nut 90 is applied, In this embodiment, the pressure Pin is applied and the primary pressure Pin is not applied during inertial traveling with the accelerator off (in other words, during driven traveling) even during traveling at the maximum gear ratio γmax. Also good.

  In the above-described embodiment, the range in which the maximum gear ratio γmax is maintained is that the movable sheave 36b of the primary pulley 36 remains in contact with the piston (or the movable sheave 36b remains in contact with the hydraulic cylinder 92). However, the present invention is not limited to this mode. For example, the range in which the maximum speed ratio γmax is maintained may be a range in which the substantially maximum speed ratio γmax is maintained. The movable sheave 36b is slightly separated from the piston (or the movable sheave 36b is slightly separated from the hydraulic cylinder 92). ) May be included. When slightly spaced apart, the stress of the nut 90 is further reduced, and the fluctuation of the stress of the nut 90 is further alleviated. When traveling at the maximum gear ratio γmax, there are times when the vehicle 10 starts, acceleration, and the like. Further, a power transmission having a power transmission path A via a continuously variable transmission and a power transmission path B via a gear mechanism different from the power transmission path A between the input shaft and the output shaft. In the case where a gear ratio larger than the maximum gear ratio γmax is formed in the power transmission path B, there is no device during the travel switching from the travel using the power transmission path B to the travel using the power transmission path A. The vehicle travels with the speed ratio γ of the step transmission 26 set to the maximum speed ratio γmax.

  In the above-described embodiment, the engine 12 is exemplified as the driving force source. However, the present invention is not limited to this aspect. For example, an engine such as an internal combustion engine is used as the driving force source, but another prime mover such as an electric motor can be used alone or in combination with the engine 12. Further, the power of the engine 12 is transmitted to the continuously variable transmission 26 via the torque converter 18, but this is not a limitation. For example, instead of the torque converter 18, another fluid transmission device such as a fluid coupling (fluid coupling) having no torque amplification function may be used. Alternatively, this fluid transmission device is not necessarily provided. Moreover, although the transmission belt 40 was illustrated as a transmission element of the continuously variable transmission 26, it is not restricted to this aspect. For example, the transmission element may be a transmission chain. In this case, the continuously variable transmission is a chain-type continuously variable transmission, but in a broad sense, the concept of a belt-type continuously variable transmission may include a chain-type continuously variable transmission.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

12: Engine (power source)
14: drive wheel 16: power transmission device 24: input shaft 26: continuously variable transmission 28: output shaft 36: primary pulley 36b: movable sheave 38: secondary pulley 40: transmission belt (transmission element)
50: Hydraulic control circuit 60: Electronic control device (control device)
64: Shift control unit 84, 92: Hydraulic cylinder 90: Nut (fixing member)

Claims (1)

A continuously variable transmission having a primary pulley provided on the input shaft, a secondary pulley provided on the output shaft, and a transmission element wound around each pulley, and transmitting the power of the driving force source to the driving wheel; A hydraulic control circuit that supplies each pulley hydraulic pressure to each pulley, and the hydraulic cylinder of the primary pulley is fixed by a fixing member so as not to move in the axial direction of the input shaft, and the transmission element slips. In the state where the secondary pulley hydraulic pressure for preventing is applied and the primary pulley hydraulic pressure is not applied so that the movement of the movable sheave of the primary pulley to the fixed member side is blocked by the fixed member, the continuously variable transmission A control device for a power transmission device in which the transmission ratio is the maximum transmission ratio,
When traveling with the gear ratio of the continuously variable transmission as the maximum gear ratio, the ratio of the secondary pulley oil pressure to the primary pulley oil pressure is within a predetermined value within a range in which the maximum gear ratio can be maintained. A control device for a power transmission device, comprising: a shift control unit that applies the primary pulley hydraulic pressure.

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