JP2004116597A - Speed-change controller of continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect a continuously variable transmission and reduce a failure in driving even if control information is unavailable in a speed-change controller of the continuously variable transmission. <P>SOLUTION: This speed-change controller includes a speed-change control unit for outputting a control signal to a continuously variable transmission and information send means connected communicably to the speed-change control unit, for sending control information to the control unit. The control unit includes line pressure control means for controlling line pressure Ps of the transmission based on the control information sent and for controlling the line pressure Ps to be a predetermined lower limit value Psm or more when the control information is unavailable. Then since the line pressure control means is controlled to be the line pressure Ps corresponding to the maximum engine torque value Tmax even when the speed-change control unit cannot use control information, the vehicle can be continued to drive and the continuously variable transmission can be protected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shift control device for a continuously variable transmission provided in a vehicle, and more particularly to a technique effective when applied to a case where the shift control device cannot use control information.
[0002]
[Prior art]
A continuously variable transmission (CVT) applied to a power transmission system of a vehicle includes a belt type continuously variable transmission, a toroidal type continuously variable transmission, and the like. Controlled automatically. For example, a belt-type continuously variable transmission has a metal drive belt between a primary pulley provided on an input shaft and a secondary pulley provided on an output shaft, and a cone is controlled by hydraulically controlling the two pulleys. Arbitrarily change the surface spacing. As a result, the diameter of the pulley with which the drive belt comes into contact is changed, and the rotation speed of the output shaft is changed steplessly. As the hydraulic pressure for controlling the continuously variable transmission, there are a primary pressure supplied to a primary pulley for controlling a cone surface interval of the pulley and a line supplied to a secondary pulley for generating a tension corresponding to a transmission torque on a drive belt. There is pressure.
[0003]
The continuously variable transmission is provided with an electronic control unit, that is, an ECU, and executes the above-described hydraulic control based on a control signal from the ECU. When setting the gear ratio, control information indicating an operating state such as a throttle opening, a vehicle speed, and an engine speed is input to the ECU. Based on the control information, the ECU sets the target primary pulley rotation speed with reference to the basic shift characteristic map, and executes the following control so that the actual primary pulley rotation speed converges on the target primary pulley rotation speed. Thus, the gear ratio is set to continuously change from low to overdrive, and the primary pressure corresponding to this gear ratio is set. Further, the ECU estimates an input torque input from the engine to the continuously variable transmission, and sets a line pressure corresponding to the input torque in consideration of the gear ratio.
[0004]
The control information used for the hydraulic control includes information directly input from a sensor to the ECU such as the vehicle speed, and information input to the ECU of the continuously variable transmission via the ECU of the engine such as the engine speed. Many ECUs, such as an ECU for an engine and an ECU for a continuously variable transmission, have a communication system in which ECUs are connected by a communication cable in order to communicate control information between a plurality of ECUs.
[0005]
In such an ECU, the ECU may be initialized, that is, the control information may be reset for control reasons. For example, the information is reset at the time of starting the power supply or at the time of returning from the power-off. When the ECU is reset, the control information is temporarily lost, which may cause a problem in hydraulic control. Therefore, when the control information is reset, a control device for a continuously variable transmission has been developed in which the hydraulic control is prohibited to thereby avoid the fluctuation of the driving force due to the unnecessary shift (for example, Patent Document 1). reference.). This can prevent the driver from feeling uncomfortable.
[0006]
[Patent Document 1]
JP 2001-227639 A
[0007]
[Problems to be solved by the invention]
However, hydraulic control is prohibited when reset of the communication system, communication failure between ECUs, or when control information is not normally input to the ECU of the continuously variable transmission due to a sensor failure or the like. There is a case where failure cannot be avoided just by doing.
[0008]
For example, when the line pressure control for preventing the slip of the drive belt is prohibited and the line pressure is controlled to be constant, if the input torque from the engine increases due to a change in the engine rotation or the like, the drive belt is clamped. The drive belt slips against the pulley due to lack of force. This belt slip not only causes a temporary malfunction in the running of the vehicle, but also causes mechanical damage between the pulley and the belt. In addition, if the hydraulic control is prohibited until normal control information is input, the speed ratio is fixed regardless of the running condition, and thus the running performance may be deteriorated.
[0009]
Further, even in a continuously variable transmission that does not prohibit hydraulic control when control information is not normally input, it is difficult to estimate the input torque, and the line pressure may be set incorrectly.
[0010]
An object of the present invention is to protect a continuously variable transmission even when control information cannot be used in a transmission control device for a continuously variable transmission.
[0011]
Another object of the present invention is to reduce traveling problems even in a case where control information cannot be used in a shift control device for a continuously variable transmission.
[0012]
[Means for Solving the Problems]
The transmission control device for a continuously variable transmission according to the present invention transmits the rotation of the input-side rotator driven by the engine to the output-side rotator by continuously changing the rotation of the input-side rotator via a power transmission element. A shift control unit for a continuously variable transmission that drives drive wheels via the shift control unit, the shift control unit outputting a control signal to the continuously variable transmission, and the shift control unit being communicably connected to the shift control unit; Information transmission means for transmitting control information to a unit, wherein the shift control unit controls the line pressure of the continuously variable transmission using the control information transmitted from the information transmission means, When the information cannot be used, a line pressure control means for controlling the line pressure to be equal to or higher than a predetermined lower limit value is provided. Thus, even when the transmission control unit cannot receive the control information or cannot use the received control information, it is possible to avoid slippage of the power transmission element. Therefore, the traveling of the vehicle can be continued, and the continuously variable transmission can be protected.
[0013]
The shift control device for a continuously variable transmission according to the present invention is characterized in that the predetermined lower limit is a line pressure for transmitting a maximum engine torque. As a result, a sufficient line pressure can be set for the output of the engine, and slippage of the power transmission element can be reliably avoided.
[0014]
In the shift control device for a continuously variable transmission according to the present invention, the shift control unit controls line pressure based on the predetermined lower limit value when transmission of torque between the engine and the drive wheels is interrupted. It has a prohibition means for prohibition. This prohibits the supply of excessive line pressure to the continuously variable transmission. Therefore, the durability of the continuously variable transmission can be improved.
[0015]
The shift control device for a continuously variable transmission according to the present invention is characterized in that the shift control unit includes a speed ratio control unit that controls a speed ratio using a line pressure based on the predetermined lower limit. As a result, the gear ratio can be changed from the start to the high-speed running, and the minimum traveling performance of the vehicle can be ensured.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a schematic diagram showing a shift control device of a continuously variable transmission mounted on a vehicle 10. As shown in FIG. 1, the vehicle 10 is provided with a plurality of control units 11 to 13, and these control units 11 to 13 output control signals to respective operating units provided in the vehicle 10. As the control units, an engine control unit 11, a CVT control unit 12, which is a speed change control unit, and a brake control unit 13, are provided, and these control units 11 to 13 are communicably connected to each other. The control units 11 to 13 are connected by a communication cable 14 such as an optical fiber cable, and a so-called in-vehicle LAN (Local Area Network) is constructed so that control signals of the control units 11 to 13 and the like are mutually communicated. ing. It should be noted that the control units 11 to 13 may be communicably connected not only by communication using the communication cable 14 but also by radio.
[0018]
To these control units 11 to 13, detection signals indicating the running condition of the vehicle type and the operating condition of the driver are input from various sensors (not shown). Based on these various signals, the engine control unit 11 outputs control signals to a fuel injection mechanism, an ignition mechanism, and the like of the engine 15 to control engine output by controlling engine speed and the like. Further, the brake control unit 13 adjusts the brake oil pressure by outputting a control signal to a valve unit 17 provided in the brake oil pressure system 16, for example, to prevent tire lock during braking or tire slip during acceleration or turning. The braking force of each of the brakes 18a and 18b is controlled so as to avoid it. Further, the CVT control unit 12 outputs a control signal to the continuously variable transmission 19 and the speedometer 20 to adjust the operating oil pressure in the continuously variable transmission 19 to perform the continuously variable transmission, and to change the vehicle speed to the speedometer. 20 is displayed.
[0019]
FIG. 2 is a schematic diagram showing the continuously variable transmission 19 controlled by the CVT control unit 12. As shown in FIG. 2, the continuously variable transmission 19 is a belt-type continuously variable transmission, in which the rotation of a crankshaft 21 of the engine 15 is transmitted from a torque converter 22 via a forward / reverse switching device 23. And a secondary shaft 25 that is parallel thereto.
[0020]
The primary shaft 24 is provided with a primary pulley 26 which is an input-side rotating body. The primary pulley 26 is a fixed pulley 26a integrated with the primary shaft 24, and a ball spline or the like is attached to the primary shaft 24 in opposition thereto. And a movable pulley 26b slidably mounted in the axial direction, and the interval between the cone surfaces of the pulleys 26a and 26b, that is, the pulley groove width is variable. The secondary shaft 25 is provided with a secondary pulley 27 which is an output side rotating body. The secondary pulley 27 is a fixed pulley 27a integrated with the secondary shaft 25, and a movable pulley 26b And a movable pulley 27b slidably mounted in the axial direction in the same manner as described above, and the pulley groove width is variable.
[0021]
A drive belt 28, which is a power transmission element, is stretched between the primary pulley 26 and the secondary pulley 27, and the groove width of both pulleys 26 and 27 is changed to wrap the drive belt 28 around the respective pulleys. Is changed, the rotation of the primary shaft 24 is transmitted to the secondary shaft 25 in a stepless manner. If the winding diameter of the drive belt 28 around the primary pulley 26 is Rp and the winding diameter around the secondary pulley 27 is Rs, the speed ratio is Rs / Rp.
[0022]
The rotation of the secondary shaft 25 is transmitted to the drive wheels 31a and 31b via a gear train having a reduction gear 29 and a differential device 30, and in the case of front wheel drive, the drive wheels 31a and 31b become front wheels. .
[0023]
In order to change the groove width of the primary pulley 26, a plunger 32 is fixed to the primary shaft 24, and a primary cylinder 33 that slidably contacts the outer peripheral surface of the plunger 32 is fixed to the movable pulley 26b. A drive oil chamber 34 is formed by the main cylinder 32 and the primary cylinder 33. On the other hand, in order to change the groove width of the secondary pulley 27, a plunger 35 is fixed to the secondary shaft 25, and a secondary cylinder 36 slidably in contact with the outer peripheral surface of the plunger 35 is fixed to the movable pulley. A driving oil chamber 37 is formed by the plunger 32 and the secondary cylinder 36. Each groove width is set by adjusting the primary pressure Pp introduced into the primary driving oil chamber 34 and the secondary pressure Ps introduced into the secondary driving oil chamber 37.
[0024]
The torque converter 22 has a pump-side shell 38 connected to the crankshaft 21 and a turbine runner 40 connected to the torque converter output shaft 39. The torque converter 22 is fixed to the pump-side shell 38 on the torque converter output shaft 39. A lock-up clutch 42 that engages with the front cover 41 is attached. An apply chamber 43 is formed on one side of the lock-up clutch 42, and a release chamber 44 is formed on the other side.
[0025]
Adjusted hydraulic oil is supplied to the apply chamber 43 and the release chamber 44. When the pressure of the hydraulic oil in the release chamber 44 is reduced, the lock-up clutch 42 is engaged with the front cover 41 by the hydraulic pressure supplied to the apply chamber 43. Together, they are in a directly connected state, that is, a lock-up state. On the other hand, the hydraulic pressure supplied to the release chamber 44 is increased to circulate the hydraulic oil from the release chamber 44 through the apply chamber 43 in the torque converter 22, thereby releasing the lock-up clutch 42 and disengaging the torque converter 22 directly. Is activated. Then, by adjusting the hydraulic pressure supplied to the release chamber 44, the lock-up clutch 42 enters a slip state with respect to the front cover 41, that is, a half-clutch state.
[0026]
The forward / reverse switching device 23 includes a planetary gear, a clutch, a brake, and the like, and switches the power transmission path from the torque converter output shaft 39 to the primary shaft 24 by performing engagement control of the clutch and the brake. Can be. A clutch cylinder 45a is fixed to the torque converter output shaft 39, and a clutch piston 45b is slidably provided in the clutch cylinder 45a. A clutch hub 46 is fixed to the primary shaft 24, and a multi-plate forward clutch 47 is provided between the clutch cylinder 45a and the clutch hub 46. A hydraulic oil chamber 45 is formed between the clutch cylinder 45a and the clutch piston 45b, and by supplying hydraulic pressure to the hydraulic oil chamber 45, the forward clutch 47 is operated between an engaged state and a released state.
[0027]
A sun gear 48 is fixed to the primary shaft 24, and a carrier 50 having a plurality of two types of planetary pinion gears 49a and 49b rotatably fixed to the clutch cylinder 45a. The two types of planetary pinion gears 49a and 49b are engaged with each other to form a pair, the planetary pinion gear 49a and the sun gear 48 are engaged, and the planetary pinion gear 49b and the ring gear 51 are engaged. That is, the sun gear 48 and the ring gear 51 are engaged via the two types of planetary pinion gears 49a and 49b. A brake cylinder 53a is fixed to the case 52 accommodating the forward / reverse switching device 23, and a brake piston 53b is slidably provided in the brake cylinder 53a. A multi-plate retraction brake 54 is provided between the case 52 and the ring gear 51. A hydraulic oil chamber 53 is formed between the brake cylinder 53a and the brake piston 53b. By supplying hydraulic pressure to the hydraulic oil chamber 53, the reverse brake 54 is operated in an engaged state and a released state.
[0028]
First, when the forward clutch 47 and the reverse brake 54 are both released, the torque converter output shaft 39 and the primary shaft 24 are disconnected, and the forward / reverse switching device 23 operates to the neutral position where power is not transmitted. When the forward clutch 47 is engaged, the rotation of the torque converter output shaft 39 is transmitted to the primary shaft 24 as it is, and the forward / reverse switching device 23 operates to the forward position where power is transmitted in the forward direction.
[0029]
When the reverse brake 54 is engaged after the forward clutch 47 is released, the carrier 50 rotates together with the primary shaft 24 by fixing the ring gear 51. When the carrier 50 rotates, the planetary pinion gear 49b rotates while engaging the inner periphery of the ring gear 51, and transmits reverse rotation to the sun gear 48 to the sun gear 48 via the paired planetary pinion gear 49a with respect to the torque converter output shaft 39. . Therefore, when the reverse brake 54 is engaged, the rotation of the torque converter output shaft 39 is transmitted in the reverse direction to the primary shaft 24, and the forward / reverse switching device 23 operates to the reverse position for transmitting the power in the reverse direction.
[0030]
FIG. 3 is a schematic diagram showing a hydraulic control system and an electronic control system of the continuously variable transmission 19. As shown in FIG. 3, hydraulic oil in an oil pan is supplied to the drive oil chambers 34 and 37 by an oil pump 55 driven by the engine 15 or an electric motor. The secondary pressure passage 56 connected to the discharge port of the oil pump 55 communicates with the drive oil chamber 37 and also communicates with the secondary pressure port of the secondary pressure regulating valve 57. The line pressure, that is, the secondary pressure Ps, supplied to the drive oil chamber 37 by the secondary pressure adjustment valve 57 is adjusted to a pressure that gives the drive belt 28 a tension necessary for torque transmission. In other words, when the engine output is large, such as when traveling on an uphill, the secondary pressure Ps is increased to prevent the drive belt 28 from slipping, while the engine output is reduced, as when traveling on a downhill. Is smaller, the secondary pressure Ps is reduced, so that the loss of the oil pump 55 is reduced and the transmission efficiency of the drive belt 28 is improved.
[0031]
The secondary pressure passage 56 is connected to a secondary pressure port of the primary pressure regulating valve 58 via a communication oil passage 59, and the primary pressure port of the primary pressure regulating valve 58 is connected to the primary side driving oil chamber 34 via the primary pressure passage. Is communicated to. The primary pressure Pp is adjusted by the primary pressure adjusting valve 58 to a value corresponding to the target gear ratio, the vehicle speed, and the like, and the gear ratio is controlled by changing the groove width of the primary pulley 26. The secondary pressure regulating valve 57 and the primary pressure regulating valve 58 are proportional solenoid valves, respectively. The secondary pressure Ps and the primary pressure Pp are controlled by controlling current values supplied from the CVT control unit 12 to the respective solenoid valves 57a and 58a. Is adjusted. A solenoid valve (not shown) for adjusting the pressure of the release chamber 44 to set the lock-up clutch 42 to the engaged state, the released state, and the slip state is also a proportional solenoid valve, and a CVT control unit is provided for this solenoid valve. A control signal is sent from the control unit 12. Further, a solenoid valve (not shown) for adjusting the pressure of the hydraulic oil chambers 45 and 53 to switch the power transmission path of the forward / reverse switching device 23 is also a proportional solenoid valve, and the CVT control unit 12 also controls this solenoid valve. A control signal is sent.
[0032]
A primary pulley rotational speed sensor 60 is provided near the primary pulley 26 to detect the primary pulley rotational speed Np of the primary pulley 26, and a secondary pulley rotational speed Ns of the secondary pulley 27 is detected to detect the secondary pulley rotational speed Ns of the secondary pulley 27. A secondary pulley rotation speed sensor 61 is provided near the pulley 27, and detection signals from these sensors 60 and 61 are transmitted to the CVT control unit 12. Further, a pressure sensor 62 for detecting a secondary pressure Ps in the drive oil chamber 37 is connected to the CVT control unit 12, and the secondary pressure Ps is transmitted. Further, detection signals from the accelerator switch 63, the brake switch 64, and the range detection sensor 65 are also transmitted to the CVT control unit 12.
[0033]
Further, a detection signal from the engine speed sensor 66 for detecting the engine speed Ne and a detection signal from various sensors 67 are transmitted to the CVT control unit 12 via the engine control unit 11 communicably connected to the CVT control unit 12. Sent to. A detection signal from the throttle opening sensor 68 for detecting the throttle opening θ is transmitted to both the engine control unit 11 and the CVT control unit 12.
[0034]
The CVT control unit 12 stores a CPU 12a that calculates control signals for the solenoid valves 57a and 58a based on signals from respective sensors and the like, and stores control data and control programs such as tables, maps, and arithmetic expressions. A ROM, a RAM for temporarily storing data, an input / output port, and the like are provided.
[0035]
FIG. 4 is a block diagram showing a shift control circuit provided in the CVT control unit 12, and each block is shown as a functional configuration. Hereinafter, pressure regulation control of the secondary pressure Ps for applying tension to the drive belt 28 will be described.
[0036]
First, the throttle opening θ and the engine speed Ne are input to the input torque calculator 71. Next, the engine torque Te is estimated by referring to the engine torque map stored in the ROM based on the throttle opening θ and the engine speed Ne. The input torque Ti input to the continuously variable transmission 19 is calculated from Ti = f (Ne, θ) by adding the engine torque Te to the amplification factor of the torque converter 22 and the like.
[0037]
On the other hand, the primary speed ratio Np and the secondary pulley speed Ns are input to the actual speed ratio calculating section 72, and the actual speed ratio i is calculated from these by i = Np / Ns. Next, the actual speed ratio i is input to the required secondary pressure setting unit 73, and the required secondary pressure Psu per unit torque is set in an increasing function corresponding to the actual speed ratio i.
[0038]
The input torque Ti and the required secondary pressure Psu are input to the target secondary pressure calculation unit 74, and the required target secondary pressure Pss under this driving condition is calculated by Pss = Ti · Psu · Ks. Note that Ks is a slight safety factor. The target secondary pressure Pss as the line pressure instruction value is input to the solenoid current setting unit 75, and the solenoid current Is corresponding to the target secondary pressure Pss is output to the solenoid valve 57a.
[0039]
The target secondary pressure Pss is set according to the input torque Ti and the actual gear ratio i. For example, when the engine torque Te is output large by depressing the accelerator, the input torque Ti is also set large to clamp the drive belt 28. The secondary pressure Ps is also set high. Further, since the required secondary pressure Psu is set according to the actual speed ratio i, the secondary pressure Ps is set high when the actual speed ratio i is large and the required transmission torque is high, while the actual speed ratio i is low. When the required transmission torque is small due to the decrease, the secondary pressure Ps is set low. For this reason, the belt slip can be prevented according to the running condition, and the necessary minimum clamping force can always be generated.
[0040]
Subsequently, the pressure regulation control of the primary pressure Pp set for performing the shift will be described. First, in order to set the target primary pulley rotation speed Npd, the actual speed ratio i and the throttle opening θ are input to the target primary pulley rotation speed setting unit 76. Based on the actual speed ratio i and the throttle opening θ, the target primary pulley rotation speed Npd is set by referring to a speed change characteristic map stored in the ROM. Next, the target primary pulley rotation speed Npd and the secondary pulley rotation speed Ns are input to the target speed ratio calculation unit 77, and the target speed ratio is is calculated by is = Npd / Ns. Then, the target speed ratio is and the actual speed ratio i are input to the speed change pressure calculating unit 78, and the correction pressure according to the deviation between the two speed ratios is, i so that the actual speed ratio i converges to the target speed ratio is. ΔPp is calculated by ΔPp = f (i-is).
[0041]
On the other hand, in order to calculate the required primary pressure Ppd corresponding to the secondary pressure Ps, the following control is executed by the hydraulic ratio control system. First, the input torque Ti, the required secondary pressure Psu and the secondary pressure Ps are input to the torque ratio calculation unit 79, and the torque ratio Kt is calculated by Kt = Ti / (Ps / Psu). Here, the torque ratio Kt is a ratio between the maximum torque (Ps / Psu) that can be transmitted at the current secondary pressure Ps and the current input torque Ti.
[0042]
The torque ratio Kt and the actual speed ratio i are input to the hydraulic ratio setting unit 80. Here, since the actual speed ratio i in the steady state is the oil pressure ratio between the secondary pressure Ps and the primary pressure Pp, the oil pressure ratio Kp is a function of the actual speed ratio i. Further, since the hydraulic pressure ratio Kp is a function of the torque ratio Kt, the hydraulic pressure ratio Kp is obtained by Kp = f (Kt / i). Then, the hydraulic pressure ratio Kp and the secondary pressure Ps are input to the required primary pressure calculation section 81, and the required primary pressure Ppd for balancing with the secondary pressure Ps is calculated based on the hydraulic pressure ratio Kp. The necessary primary pressure Ppd is calculated by Ppd = Kp · Ps−gp, taking into consideration the centrifugal oil pressure gp of the primary cylinder 33 portion based on the primary pulley rotation speed Np.
[0043]
Then, the required primary pressure Ppd and the correction pressure ΔPp are input to the target primary pressure calculation unit 82, and the target primary pressure Pps as the primary pressure instruction value is calculated. Note that the target primary pressure Pps is calculated by Pps = Ppd + ΔPp during an upshift and by Pps = Ppd−ΔPp during a downshift. Then, the target primary pressure Pps is input to the solenoid current setting unit 83, and a solenoid current Ip corresponding to the target primary pressure Pps is output toward the solenoid valve 58a. As a result, the gear ratio is steplessly changed by the operation of the primary pulley 26, and the vehicle 10 travels smoothly from the start to the high-speed travel.
[0044]
The control information transmitted to the CVT control unit 12 to control the secondary pressure Ps, which is the line pressure, includes, for example, the engine speed Ne and the throttle opening θ used when setting the input torque Ti. As described above, there is control information transmitted from the engine control unit 11, the engine speed sensor 66, and the throttle opening sensor 68 as information transmission means. By using these pieces of control information, the input torque Ti from the engine 15 is calculated, and a secondary pressure Ps for generating a clamping force on the drive belt 28 based on the input torque Ti is set.
[0045]
Here, when the control information input to the CVT control unit 12 cannot be used, for example, a failure of the CVT control unit 12 or the engine control unit 11, a poor connection between the control units, the engine speed sensor 66, the throttle opening, or the like. If the engine speed Ne and the throttle opening θ as the control information are not transmitted normally due to a failure of the sensor 68, the input torque Ti cannot be calculated normally.
[0046]
In addition, even when the CVT control unit 12 or the engine control unit 11 returns from an initial state such as immediately after the power supply is started or after the power is turned off, it may not be possible to judge control information communication for a while. There is a possibility that Ti cannot be calculated. This is because the delay time is set in the control program of the control unit in order to accurately determine the communication, and the determination is suspended until confirmation information from the engine control unit 11 is sent. It is. That is, even if control information can be received for a while after initialization, a state occurs in which the control information cannot be used.
[0047]
As described above, when the control information cannot be received or when the received control information cannot be used, the CVT control unit 12 cannot calculate the input torque Ti and the secondary torque corresponding to the engine output at this time. The pressure Ps cannot be set. For this reason, the clamping force on the drive belt 28 is insufficient depending on the fluctuation of the engine output, so that the drive belt 28 may slip. The belt slip not only makes traveling of the vehicle 10 difficult but also causes mechanical damage to the continuously variable transmission 19.
[0048]
Therefore, the CPU 12a provided in the CVT control unit 12 and functioning as a line pressure control unit controls the secondary pressure Ps according to the flowchart shown in FIG. As shown in FIG. 5, in step S1, it is determined whether or not the CVT control unit 12 is in the initialization state. If it has not been initialized, the process proceeds to step S2, where it is determined whether a communication failure has occurred in the CVT control unit 12. On the other hand, if it has been initialized, the process proceeds to step S3, where it is stored in the CVT control unit 12. The maximum engine torque value Tmax, which is the maximum engine torque, is replaced with the value of the input torque Ti. When the input torque Ti is replaced in step S3, in subsequent step S4, a lower limit secondary pressure Psm as a predetermined lower limit value is set based on the replaced input torque Ti, and a secondary pressure Ps equal to or higher than the lower limit secondary pressure Psm is used. The operation of the pulley 27 is controlled. The setting of the lower limit secondary pressure Psm based on the input torque Ti to be replaced is executed according to the block diagram shown in FIG.
[0049]
If it is determined in step S2 that there is a communication failure, the process proceeds from step S3 to step S4, and the operation of the secondary pulley 27 is controlled in the same manner as described above, while if it is determined that no communication failure has occurred, step S5 is performed. The input torque Ti is calculated from the engine speed Ne and the throttle opening θ, and the operation of the secondary pulley 27 is controlled by the secondary pressure Ps based on the calculated input torque Ti.
[0050]
As described above, when the control information cannot be used due to the initialization of the CVT control unit 12 or communication failure and it becomes difficult to calculate the input torque Ti, the maximum engine torque value Tmax can be transmitted. The secondary pressure Ps is set to a numerical value. Thus, even if the engine output rises to the maximum, a sufficient clamping force is applied to the drive belt 28, so that belt slip can be avoided. Therefore, the vehicle 10 can be driven and mechanical damage to the continuously variable transmission 19 can be avoided.
[0051]
Although the secondary pulley 27 is controlled by the secondary pressure Ps that is equal to or higher than the lower limit secondary pressure Psm corresponding to the maximum engine torque value Tmax, the secondary pulley 27 may be controlled by the pressure of the lower limit secondary pressure Psm itself. Further, the lower limit secondary pressure Psm is not limited to the pressure corresponding to the maximum engine torque value Tmax, and may be set to a pressure corresponding to another engine torque value. For example, the secondary pressure Ps immediately before the control information can no longer be used may be used as the lower limit secondary pressure Psm.
[0052]
Further, when initialization or communication failure occurs during traveling of the vehicle 10, the CPU 12a provided in the CVT control unit 12 and functioning as a speed ratio control means obtains the input torque Ti according to the flowchart of FIG. The secondary pressure Ps is set based on the torque Ti, and the primary pressure Pp for performing the shift control is set according to the block diagram of FIG. As a result, even when initialization or communication failure occurs, the gear ratio can be controlled using the secondary pressure Ps that is equal to or higher than the lower limit secondary pressure Psm. You can drive.
[0053]
In addition, when the control information returns to a state where control information can be used after a certain period of time has elapsed after the initialization, or when a state where control information is input after returning from a communication failure, the control information is used. The input torque Ti is calculated based on a certain engine speed Ne and the throttle opening θ, and the secondary pressure Ps is set based on the input torque Ti. As a result, the hydraulic pressure supplied to the drive belt 28 and the pulleys 26 and 27 can be made appropriate, and wear and fatigue failure of the drive belt 28 and the pulleys 26 and 27 can be prevented. The durability of the transmission 19 can be improved.
[0054]
Further, when the CPU 12a provided in the CVT control unit 12 and functioning as a prohibiting means does not transmit the power from the engine 15 to the drive wheels 31a and 31b by operating the forward / reverse switching device 23 to the neutral position, the CPU 12a performs the steps shown in FIG. The secondary pressure Ps control shown in S3 and S4 is prohibited. As described above, when the engine 15 and the driving wheels 31a and 31b are electrically separated from each other, since a large load is not applied to the continuously variable transmission 19, the control is performed by the initialization of the CVT control unit 12 or a communication failure. Even when the information cannot be used, the control of the secondary pressure Ps according to the maximum engine torque value Tmax is prohibited. For this reason, it is possible to prevent an excessive supply of hydraulic pressure to the drive belt 28 and the pulleys 26 and 27, reduce the load on the oil pump 55, and prevent wear and fatigue failure of the continuously variable transmission 19. be able to. Note that the CVT control unit 12 stores in advance the minimum secondary pressure Ps required when the forward / reverse switching device 23 is operated to the neutral position, and when the replacement control is prohibited, It is controlled to the value of the secondary pressure Ps.
[0055]
The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the invention. For example, the CVT control unit 12 estimates the engine output based on the engine speed Ne and the throttle opening θ, but may use the intake air amount or the intake air pressure as control information. Alternatively, the engine torque itself may be received.
[0056]
Further, the torque transmission between the engine 15 and the drive wheels 31a and 31b is interrupted by operating the forward / reverse switching device 23 to the neutral position. The torque transmission may be interrupted by using a clutch. Needless to say, an electric motor or the like may be used as the engine 15.
[0057]
Further, a belt type continuously variable transmission is described as an example of the continuously variable transmission, but the present invention is not limited to this, and may be applied to a toroidal type continuously variable transmission. The toroidal type continuously variable transmission has an input disk as an input-side rotating body and an output disk as an output-side rotating body, and the rotation of the input disk is transmitted via a power roller as a power transmission element. Continuously variable transmission transmitted to the output disk. The change of the gear ratio is performed by tilting the center axis of the power roller and moving the contact point between the disk and the roller in the radial direction of the disk. In this toroidal-type continuously variable transmission, the line pressure is a pressure for setting a pressing force of a roller against a disk.
[0058]
Note that, even when the control information cannot be used when the engine 15 is stopped or until the start of the engine 15 is determined, even if the secondary pressure Ps control shown in steps S3 and S4 in FIG. 5 is prohibited. good.
[0059]
【The invention's effect】
According to the present invention, even when the transmission control unit cannot use the control information, the line pressure control unit controls the line pressure to be equal to or higher than the predetermined lower limit value to avoid slippage of the power transmission element. Can be. Therefore, the traveling of the vehicle can be continued, and the continuously variable transmission can be protected.
[0060]
Further, by setting the predetermined lower limit to the line pressure for transmitting the maximum engine torque, it is possible to set a sufficient line pressure with respect to the output of the engine, and to surely avoid slippage of the power transmission element. it can.
[0061]
Further, when the transmission of torque between the engine and the driving wheels is interrupted, the prohibiting means prohibits the control of the line pressure based on the predetermined lower limit, so that the supply of the excessive line pressure to the continuously variable transmission is prohibited. Is forbidden. Therefore, the durability of the continuously variable transmission can be improved.
[0062]
Further, the speed ratio control means can change the speed ratio from the start to the high-speed running by controlling the speed ratio using the line pressure based on the predetermined lower limit value, thereby securing the minimum traveling performance of the vehicle. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a shift control device of a continuously variable transmission according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a continuously variable transmission.
FIG. 3 is a schematic diagram showing a hydraulic control system and an electronic control system of the continuously variable transmission.
FIG. 4 is a block diagram showing a shift control circuit of the continuously variable transmission.
FIG. 5 is a flowchart showing a procedure for controlling a secondary pressure.
[Explanation of symbols]
10 vehicles
11 Engine control unit (information transmission means)
12 CVT control unit (transmission control unit)
12a CPU (line pressure control means, inhibition means, speed ratio control means)
15 Engine
19 continuously variable transmission
26 Primary pulley (input side rotating body)
27 Secondary pulley (output side rotating body)
28 Drive belt (power transmission element)
66 Engine speed sensor (information transmission means)
68 Throttle opening sensor (information transmission means)
Ps Secondary pressure (line pressure)
Psm Lower limit secondary pressure (predetermined lower limit)
Ne engine speed (control information)
θ Throttle opening (control information)
Tmax Maximum engine torque value (Maximum engine torque)

Claims (4)

A continuously variable transmission that changes the rotation of an input-side rotating body driven by an engine in a stepless manner through a power transmission element and transmits the rotation to an output-side rotating body, and drives driving wheels through the output-side rotating body. A shift control device,
A shift control unit that outputs a control signal to the continuously variable transmission;
An information transmission unit that is communicably connected to the shift control unit and transmits control information to the shift control unit;
The shift control unit controls the line pressure of the continuously variable transmission using the control information transmitted from the information transmitting unit, and when the control information cannot be used, the line pressure is increased to a predetermined lower limit or more. A transmission control device for a continuously variable transmission, comprising: a line pressure control means for controlling the speed. 2. The shift control device for a continuously variable transmission according to claim 1, wherein the predetermined lower limit is a line pressure for transmitting a maximum engine torque. 3. The transmission control device for a continuously variable transmission according to claim 1, wherein the transmission control unit is configured to control a line based on the predetermined lower limit value when transmission of torque between the engine and the drive wheels is interrupted. 4. A shift control device for a continuously variable transmission, comprising a prohibition unit for prohibiting pressure control. 4. The transmission control device for a continuously variable transmission according to claim 1, wherein the transmission control unit includes a transmission ratio control unit that controls a transmission ratio using a line pressure based on the predetermined lower limit value. 5. A shift control device for a continuously variable transmission, comprising:

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