JP2004124968A - Controller for belt type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a belt type continuously variable transmission improving the durability of a belt by increasing the accuracy in determining the belt slipping. <P>SOLUTION: The generation of belt slipping is determined when a state that a primary rotating speed N<SB>pri</SB>is more than a value obtained by multiplying a maximum change gear ratio of a mechanism by a secondary rotating speed N<SB>sec</SB>, continues for a specific time, and the belt protection control is performed for setting the torque limitation of an engine. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of a control device for a belt-type continuously variable transmission.
[0002]
[Prior art]
The control device of the conventional belt-type continuously variable transmission is provided with a primary rotation speed sensor on the primary pulley, a secondary rotation speed sensor on the secondary pulley, and reading the external teeth provided on the peripheral portions of both pulleys with a sensor. The primary speed and the secondary speed are detected, and the actual speed ratio is calculated from these values. When the actual gear ratio or the gear speed becomes a value that cannot be obtained mechanically, it is determined that the belt is slipping, and a control is performed to increase the pulley clamp pressure by increasing the line pressure and correcting the pressure (see, for example, Patent Document 1). 1).
[Patent Document 1]
JP-A-62-68142 (pages 1 and 2)
[0003]
[Problems to be solved by the invention]
However, in the conventional control device for a belt-type continuously variable transmission, a speed ratio larger than the maximum speed ratio that can be taken by the mechanism is detected instantaneously even when the belt slip does not occur, for the following reason. In some cases, the occurrence of belt slippage may be erroneously determined.
(1) When calculating the actual gear ratio, a plurality of processes such as filtering of a detection pulse are required, so that a detection delay occurs.
(2) At the time of low rotation such as when starting, the detection error of the sensor becomes large.
[0004]
As a result, when the engine torque output is limited in a situation where the occurrence of the belt slip is erroneously determined as described above, there is a problem that the startability is reduced. Further, when the line pressure is increased and corrected, the pulley clamp pressure becomes excessively high, which causes a problem that the belt durability is reduced.
[0005]
On the other hand, even if the shift speed is calculated from the shift ratio calculated as described above, and belt slip is detected from the shift speed, the above problem is not solved.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for a belt-type continuously variable transmission capable of improving belt slippage accuracy and improving belt durability. To provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a primary pulley having a variable pulley interval is provided on a main shaft on the engine side, and a variable pulley interval is provided on a sub-axle on a wheel side arranged in parallel with the main shaft. Is provided with a secondary pulley, a drive belt is wound between the pulleys, and a stepless transmission that continuously changes the speed by controlling the hydraulic pressure of both pulleys and changing the ratio of the winding diameter of the drive belt to both pulleys A speed ratio calculating means for calculating a speed ratio based on the primary pulley rotation speed and the secondary pulley rotation speed, and when the value of the speed ratio is continuously out of the speed ratio region on the mechanism for a predetermined time, belt slippage occurs. Belt slip determining means for determining that a belt slip has occurred.
[0008]
According to a second aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the first aspect, an engine speed detecting unit is provided, and the belt slip determining unit generates a hydraulic pressure sufficient for the engine speed. When the rotational speed is equal to or higher than a predetermined rotational speed estimated to be possible, a belt protection control unit that performs belt protection control when the belt slip is determined to be determined. It is characterized by having been provided.
[0009]
According to a third aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the second aspect, the belt protection control is a control that regulates an upper limit of an engine torque.
[0010]
According to a fourth aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the second aspect, the belt protection control is an upshift.
[0011]
According to a fifth aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the second aspect, the belt protection control is a control for regulating an upper limit of an engine speed.
[0012]
According to a sixth aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the second aspect, the belt protection control is a control for increasing an engine idle speed when the vehicle is stopped by a predetermined speed. It is characterized by.
[0013]
According to a seventh aspect of the present invention, in the control device for a belt-type continuously variable transmission according to the first aspect, an acceleration detecting means for detecting an acceleration of the vehicle is provided, and the belt slip determining means determines whether the detected acceleration is The predetermined time is set to be longer as the value is larger.
[0014]
【The invention's effect】
According to the first aspect of the present invention, when the value of the gear ratio calculated by the gear ratio calculating means continuously deviates from the gear ratio region on the mechanism for a predetermined period of time, the belt slip occurs. Judge that there is. Therefore, when the maximum gear ratio instantaneously becomes a value that cannot be obtained mechanically due to a detection error of the sensor or the like even though the belt slip does not occur, the belt slip is not erroneously determined, and the belt slip is determined. Accuracy can be increased.
[0015]
According to the second aspect of the present invention, the belt slip determination means determines that belt slip has occurred when the engine speed is equal to or higher than a predetermined speed that is estimated to be able to generate sufficient oil pressure, and the belt protection is performed. Perform control. On the other hand, when the engine speed is low, the belt protection control is not performed.
[0016]
Therefore, a failure of the hydraulic circuit, for example, a belt slip caused by a stick or the like of the electro-hydraulic control valve can be reliably detected in a short period of time, and the durability of the belt can be improved. On the other hand, with respect to belt slippage caused when the engine rotation is unstable, excessive belt protection control is not performed, and deterioration of running performance can be prevented.
[0017]
According to the third aspect of the present invention, since the upper limit of the engine torque is regulated to regulate the upper limit of the input torque to the primary pulley, the input torque can be surely suppressed to prevent the belt from slipping.
[0018]
According to the fourth aspect of the present invention, by performing the upshift, it is possible to increase the transmittable input torque, and it is possible to prevent belt slippage.
[0019]
According to the fifth aspect of the invention, by limiting the upper limit of the engine speed, it can be considered that the upper limit of the engine torque is limited. Therefore, the input torque to the primary pulley can be reliably suppressed to prevent belt slippage.
[0020]
According to the invention described in claim 6, the discharge amount of the oil pump driven by the engine when the vehicle is stopped can be ensured by increasing the engine idle speed by a predetermined speed when the vehicle is stopped. Therefore, it is possible to secure a sufficient pulley clamping pressure even at the time of starting when a large load is applied to the pulley, and it is possible to prevent belt slippage.
[0021]
According to the seventh aspect of the present invention, by setting the predetermined time for judging a state in which the maximum speed ratio is exceeded as the acceleration is larger, the erroneous detection can be prevented and the durability of the belt can be improved.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a control system of an engine and a belt-type continuously variable transmission 3 (hereinafter abbreviated as CVT) according to the embodiment.
[0023]
1 is a torque converter, 2 is a lock-up clutch, 3 is a CVT, 4 is a primary speed sensor, 5 is a secondary speed sensor, 6 is a hydraulic control valve unit, 8 is an oil pump driven by an engine, and 9 is CVT control. The unit 10 is an accelerator opening sensor, 11 is an oil temperature sensor, 18 is an engine, 19 is an engine control unit (hereinafter abbreviated as ECU), 16 is an engine speed sensor, and 17 is a throttle opening sensor.
[0024]
The engine 18 is provided with a plurality of injectors for injecting fuel and an electronically controlled throttle operated by an electric actuator. The ECU 19 issues a fuel injection command and an electronic control throttle opening command for each injector.
[0025]
The ECU 19 basically includes a signal from the engine speed sensor 16 for detecting the engine speed Ne, a signal from the accelerator opening sensor 10 for detecting the accelerator pedal operation amount APS of the driver, and a throttle opening corresponding to the engine load. A signal from the throttle opening sensor 17 for detecting the degree TVO is input, and an output torque control command, an engine idling speed control command when the vehicle is stopped, and fuel injection is cut until the engine speed decreases to a predetermined speed during deceleration. And outputs a fuel cut control command for improving the fuel consumption.
[0026]
A torque converter 1 is connected to the engine output shaft as a rotation transmission mechanism, and a lock-up clutch 2 that directly connects the engine and the CVT 3 is provided.
The output side of the torque converter 1 is connected to the ring gear 21 of the forward / reverse switching mechanism 20. The forward / reverse switching mechanism 20 includes a planetary gear mechanism including a ring gear 21 connected to the engine output shaft 12, a pinion carrier 22, and a sun gear 23 connected to the transmission input shaft 13. The pinion carrier 22 is provided with a reverse brake 24 for fixing the pinion carrier 22 to the transmission case, and a forward clutch 25 for integrally connecting the transmission input shaft 13 and the pinion carrier 22.
[0027]
A primary pulley 30 a of the CVT 3 is provided at an end of the transmission input shaft 13. The CVT 3 includes the primary pulley 30a, the secondary pulley 30b, a belt 34 that transmits the rotational force of the primary pulley 30a to the secondary pulley 30b, and the like. The primary pulley 30a is provided with a fixed conical plate 31 that rotates integrally with the transmission input shaft 13, and is arranged opposite to the fixed conical plate 31 to form a V-shaped pulley groove, and the primary pulley 30a is shifted by hydraulic pressure acting on the primary pulley cylinder chamber 33. The movable conical plate 32 is movable in the axial direction of the machine input shaft 13.
[0028]
The secondary pulley 30b is provided on the driven shaft 38. The secondary pulley 30 b has a fixed conical plate 35 that rotates integrally with the driven shaft 38, a V-shaped pulley groove disposed opposite to the fixed conical plate 35, and a driven shaft 38 formed by hydraulic pressure acting on the secondary pulley cylinder chamber 37. And a movable conical plate 36 that can move in the axial direction.
[0029]
A drive gear (not shown) is fixed to the driven shaft 38. The drive gear is formed of a driven wheel and a drive wheel (not shown) through a pinion, a final gear, and a differential device provided on the idler shaft. Drive the drive shaft to the drive wheels.
[0030]
The torque input from the engine output shaft 12 to the CVT 3 is transmitted to the CVT 13 via the torque converter 1 and the forward / reverse switching mechanism 20. The rotational force of the transmission input shaft 13 is transmitted to the differential via a primary pulley 30a, a belt 34, a secondary pulley 30b, a driven shaft 38, a drive gear, an idler gear, an idler shaft, a pinion, and a final gear.
[0031]
At the time of the power transmission as described above, the movable conical plate 32 of the primary pulley 30a and the movable conical plate 36 of the secondary pulley 30b are moved in the axial direction to change the contact position radius with the belt 34, so that the primary pulley 30a The rotation ratio with the secondary pulley 30b, that is, the gear ratio, can be changed. Such control of changing the width of the V-shaped pulley groove is performed by hydraulic control of the primary pulley cylinder chamber 33 or the secondary pulley cylinder chamber 37 via the CVT control unit 9.
[0032]
The CVT control unit 9 includes a primary rotation speed N _pri from the primary rotation speed sensor 4, a secondary rotation speed N _sec from the secondary rotation speed sensor 5, a primary pulley pressure P _pri from the primary pressure sensor 14, and a signal from the secondary pressure sensor 15. secondary pulley pressure _{P sec,} etc. are input. In addition, information such as the acceleration of the vehicle body and each sensor value calculated from, for example, the driven wheel sensor 17a is transmitted and received through communication with the ECU 19, and a control signal is calculated based on these input signals and transmitted to the hydraulic control valve unit 6. Outputs control signal.
[0033]
The hydraulic control valve unit 6 drives each electronic control valve and a step motor 54 described later based on the control signal calculated by the CVT control unit 9, and applies a control pressure to the primary pulley cylinder chamber 33 and the secondary pulley cylinder chamber 37. The shift control is performed by supplying.
[0034]
FIG. 2 is a circuit diagram illustrating a hydraulic circuit of the belt-type continuously variable transmission according to the embodiment.
Reference numeral 40 denotes a pressure regulator valve that regulates the discharge pressure of the oil pump 8 supplied from the oil passage 41 as a line pressure (pulley clamp pressure). An oil passage 42 communicates with the oil passage 41. The oil passage 42 is connected to a shift control valve 50 that supplies control oil pressure to the primary pulley cylinder chamber 33 of the CVT 3, and is connected to a pulley pressure supply oil passage 48 that supplies a clamp pressure for clamping the belt 34 to the secondary pulley cylinder chamber 37. It is connected via a pressure reducing valve 49. The oil passage 43 connected to the oil passage 42 supplies the original pressure of the pilot valve 55.
[0035]
The pressure reducing valve 49 drives a solenoid according to a control signal from the CVT control unit 9, and controls the secondary pulley pressure P _sec by feedback control (closed loop control).
[0036]
The shift control valve 50 is provided with a suction port 50a connected to the oil passage 42, a supply port 50b for supplying oil pressure to the primary pulley cylinder chamber 33, a drain port 50c for draining oil pressure, and a control signal from the CVT control unit 9. An actuating step motor 54 is connected by a link 52, thereby forming a mechanical feedback mechanism.
[0037]
When the spool 50d is moved by the drive of the step motor 52 and the hydraulic pressure is supplied to the primary pulley cylinder chamber 33, the movable pulley moves due to a change in the gear ratio, and this movement causes the spool 50d to drive the step motor 54 again. By driving in the reverse direction, the supply of hydraulic pressure is stopped, so that a desired gear ratio can be obtained. On the other hand, when the spool 50d is moved by the driving of the step motor 52 and the hydraulic pressure of the primary pulley cylinder chamber 33 is discharged, the movable pulley moves due to a change in the gear ratio, and this movement again causes the direction opposite to the driving of the spool 50d. , The discharge of the hydraulic pressure is stopped, and a desired gear ratio can be obtained.
[0038]
The hydraulic pressure drained from the pressure regulator valve 40 is supplied to the clutch regulator valve 60 via the oil passage 46. As described above, by adjusting the oil pressure lower than the oil pressure generated by the pressure regulator valve 40 by the clutch regulator valve 60, the oil pressure supplied as the engagement pressure of the forward clutch 25 does not become higher than the pulley clamp pressure. .
[0039]
The oil passage 46 communicates with the oil passage 42 and an oil passage 44 having an orifice 45. The clutch regulator valve 60 regulates the oil pressure in the oil passage 46 and the oil passage 61. The oil pressure in the oil passage 61 is supplied to the select switching valve 80 and the select control valve 90.
[0040]
Reference numeral 55 denotes a pilot valve for setting a constant supply pressure to the lock-up solenoid 71 and the select switching solenoid 70 via the oil passage 56. The output pressure of the select switching solenoid 70 is supplied from the oil passage 73 to the select switching valve 80, and controls the operation of the select switching valve 80. The output pressure of the lock-up solenoid 71 is supplied from the oil passage 72 to the select switching valve 80.
[0041]
A select switching valve 80 is operated by a select switching solenoid 70. The select switching valve 80 is connected as an input port to an oil passage 72 for supplying a signal pressure from a lock-up solenoid 71, an oil passage 61 regulated by a clutch regulator valve 60 is connected, and a select control valve 90 The regulated oil passage 93 is connected. Further, an oil passage 81 for supplying forward clutch pressure to the manual valve 100 is connected as an output port, an oil passage 82 for supplying oil pressure to a lock-up clutch control valve (not shown) is connected, and a spool 92 of the select control valve 90 is connected. Is connected, and a drain oil passage 84 for draining the hydraulic pressure is connected.
[0042]
Reference numeral 90 denotes a select control valve which is operated by a lock-up solenoid 71 supplied from an oil passage 83. The select control valve 90 is connected, as an input port, to an oil passage 62 regulated by the clutch regulator valve 60 and an oil passage 83 for supplying a signal pressure of the lock-up solenoid 71. Then, the hydraulic pressure is adjusted by controlling the communication state between the oil passage 62 and the oil passage 93.
[0043]
Next, the operation will be described.
[Belt slip judgment control processing]
FIG. 3 is a flowchart showing the flow of the belt slip determination control process in the CVT control unit 9.
[0044]
In step S101, it is determined whether the primary rotation speed N _pri detected by the primary rotation speed sensor 4 is equal to or more than a predetermined value, for example, 500 rpm. If it is not less than 500 rpm, the process proceeds to step S102, and if it is less than 500 rpm, the process proceeds to step S107. This is because if the primary rotation speed N _pri becomes 500 rpm or less, the detection noise of the primary rotation speed sensor 4 increases, and in this case, slip determination is not performed, thereby reducing erroneous determination of belt slip. is there.
[0045]
In step S102, it is determined whether or not the detected primary rotational speed N _pri is a speed ratio that can be obtained mechanically (suitably for the mechanism) by determining whether the primary rotational speed N _pri is the maximum speed ratio 2.7 and the secondary rotational speed N _sec . Judgment is made based on whether the value is equal to or larger than the multiplied value. If the primary speed N _pri is equal to or greater than the value obtained by multiplying the maximum speed ratio 2.7 by the secondary speed N _sec , the process proceeds to step S103, and the primary speed N _pri is increased to the maximum speed ratio 2.7. It is smaller than multiplied by the rotational speed _{N sec} value, the process proceeds to step S107.
[0046]
In step S103, it is determined whether or not the belt slip occurs while the oil pump 8 is operating normally, based on whether or not the engine speed Ne is equal to or higher than a predetermined value, for example, 600 rpm. When the engine speed Ne is equal to or higher than 600 rpm, the process proceeds to step S104, and when the engine speed Ne is lower than 600 rpm, the process proceeds to step S107.
[0047]
In step S104, the timer counts down.
[0048]
In step S105, it is determined whether or not the state in which the primary rotation speed N _pri has exceeded the mechanically obtainable maximum gear ratio has continued for a predetermined time, based on whether or not the countdown of the timer has ended. Note that the predetermined time is set to a time during which a reading error occurring when the vehicle can normally take acceleration can be excluded from the belt slip determination. For example, the predetermined time is set to 0.2 sec. This predetermined time may be changed based on the acceleration detected from 17a. In this case, as shown in FIG. 6, by setting the predetermined time longer as the acceleration is larger and set shorter as the acceleration is smaller, it is possible to prevent both erroneous detection and improve the durability of the belt. If the countdown has ended, the process proceeds to step S106, and if the countdown has not ended, the present control is ended.
[0049]
In step S106, it is determined that belt slippage has occurred, belt protection control is performed, and the present control ends.
[0050]
In step S107, the timer is initialized, and the control ends.
[0051]
[Belt protection control processing when belt slippage is determined]
FIG. 4 is a flowchart showing the flow of the belt protection control process when the belt slippage is determined in the CVT control unit 9.
[0052]
In step S201, the target position of the step motor 54 is set to the overdrive-side operation limit.
[0053]
In step S202, the drive speed of the step motor 54 is set to a predetermined value.
[0054]
In step S203, a command to limit the engine speed Ne to a predetermined value or less is output to the ECU 19.
[0055]
In step S204, a command to increase the idle speed to a predetermined value is output to the ECU 19.
[0056]
In step S205, it is determined whether or not the actual position of the step motor 54 has reached the overdrive-side operation limit. If it is the operation limit, the process proceeds to step S206, and if it is not the operation limit, the process proceeds to step S209.
[0057]
In step S206, the timer counts down.
[0058]
In step S207, it is determined whether or not a predetermined time has elapsed since the actual position of the step motor 54 reached the overdrive-side operation limit, that is, an instruction to set the gear ratio to the maximum Hi is output, and then the pulley is moved to the overdrive-side operation limit. It is determined whether or not the movement has occurred based on whether or not the countdown of the timer has ended. If the countdown has been completed, the process proceeds to step S208. If the countdown has not been completed, the process proceeds to step S209.
[0059]
In step S208, a command to set the torque limit of the engine 20 to 70 Nm is output to the ECU 19, and the control ends.
[0060]
In step S209, a command to set the torque limit of the engine 20 to 50 Nm is output to the ECU 19, and the control ends.
[0061]
[Belt protection control when determining belt slippage]
FIG. 5 is a time chart showing the belt protection control operation when the belt slippage is determined.
[0062]
At t1, the pulley ratio (speed ratio) exceeds the maximum speed ratio on the mechanism. At this time, in the flowchart of FIG. 3, the flow proceeds to step S101 → step S102 → step S103 → step S104 → step S105.
[0063]
That is, in step S101, it is determined that the primary rotational speed Npri is 500 rpm or more, and in step S102, it is determined that the primary rotational speed Npri is at least the mechanically possible maximum gear ratio 2.7 or more. Subsequently, it is determined in step S103 that the engine speed Ne is equal to or greater than 600 rpm, the timer is counted down in step S104, and it is determined in step S105 that the countdown has not been completed.
[0064]
At t2, since 0.2 sec, which is a predetermined time, has elapsed since the speed ratio exceeded the mechanical maximum speed ratio, in the flowchart of FIG. 3, the process proceeds to step S101 → step S102 → step S103 → step S104 → step S105 → step S106. It becomes the flow which advances.
[0065]
That is, it is determined in step S105 that the countdown has ended, and it is determined in step S106 that belt slippage has occurred, and belt holding control is performed. In the belt holding control, in the flowchart of FIG. 4, the flow proceeds to step S201 → step S202 → step S203 → step S204 → step S205 → step S209.
[0066]
That is, the target position of the step motor 54 is set to the overdrive-side operation limit in step S201, and the drive speed of the step motor 54 is set to a predetermined value in step S202. Then, a command to limit the engine speed Ne to a predetermined value or less is output to the ECU 19 in step S203, and a command to increase the idle speed to the predetermined value is output to the ECU 19 in step S204. Next, in step S205, it is determined that the actual position of the step motor 54 has not reached the overdrive-side operation limit, and in step S209, a command to set the torque limit of the engine 20 to 50 Nm is output to the ECU 19.
[0067]
Here, the overdrive-side operation limit refers to a position where the step motor 54 is further moved to the upshift side than the position of the minimum speed ratio in terms of the speed ratio. The reason for moving to this position is that the pulley pressure supply oil passage 48 that supplies the hydraulic pressure to the secondary pulley 30b fails (for example, the pressure reducing valve 49 is locked, the line pressure is generated, but the secondary pulley pressure P _sec is low). This is because the torque capacity can be ensured by the mechanical stoppers of the primary pulley and the secondary pulley by setting the pulley position to the minimum gear ratio side even when the vehicle is in the state), and belt slippage can be prevented. In general, the input torque that can be transmitted by the pulley increases as the gear ratio decreases.
[0068]
Incidentally, when the pressure of the pressure regulator valve 40 fails and the primary pulley pressure P _pri and the secondary pulley pressure P _sec are both low, even if the step motor 54 is moved to the overdrive-side operation limit, the pulley ratio becomes intermediate due to insufficient hydraulic pressure. Stay at pulley position.
[0069]
At t3, since the actual position of the step motor 54 has reached the operation limit on the overdrive side, in the flowchart of FIG. 4, step S201 → step S202 → step S203 → step S204 → step S205 → step S206 → step S207 → step S209. It is a flow to go.
[0070]
That is, it is determined in step S205 that the actual position of the step motor 54 has reached the overdrive-side operation limit, and the timer is counted down in step S206. Subsequently, it is determined in step S207 that the countdown has not been completed, and a command to set the torque limit of the engine 20 to 50 Nm is continuously output in step S209.
[0071]
This is because, when the secondary pulley pressure _Psec is low, torque transmission cannot be performed unless the position of the step motor 54 has reached the overdrive-side operation limit, so that the torque limit of the engine 20 is kept low. Further, as described above, when the pressure regulator valve 40 fails, the pulley ratio remains at the intermediate pulley position, so that it is necessary to reduce the torque limit in order to suppress belt slippage.
[0072]
At t4, since a predetermined time has elapsed since the actual position of the step motor 54 reached the overdrive-side operation limit, in the flowchart of FIG. 4, step S201 → step S202 → step S203 → step S204 → step S205 → step S205 → step S207 → step S207 → The flow proceeds to step S208.
[0073]
That is, it is determined in step S207 that the countdown has ended, and a command to set the torque limit of the engine 20 to 70 Nm is output to the ECU 19 in step S208.
[0074]
Next, effects will be described.
(1) When the state where the primary rotational speed N _pri exceeds a value obtained by multiplying the maximum gear ratio 2.7 that can be taken mechanically by the secondary rotational speed N _sec for a predetermined period of time, it is determined that a belt slip has occurred. Therefore, erroneous determination of belt slippage can be prevented when the maximum gear ratio instantaneously becomes a value that cannot be obtained mechanically due to detection errors of the primary and secondary rotation speed sensors 4 and 5, and the accuracy of belt slip determination is improved. Can be enhanced.
[0075]
(2) When the engine speed Ne is equal to or higher than 600 rpm, that is, when it is estimated that a sufficient line pressure has been generated, it is determined that the belt slip has occurred under the above conditions, so that the hydraulic circuit fails. For example, belt slippage caused by, for example, a stick of an electro-hydraulic control valve or the like can be reliably detected in a short time from the occurrence, and the durability of the belt can be improved. On the other hand, when the engine speed Ne is less than 600 rpm, the belt slippage that occurs when the engine speed is unstable is not excessively controlled by the belt protection, so that it is possible to prevent the traveling performance from deteriorating.
[0076]
(3) When it is determined that belt slippage has occurred, the engine speed Ne is limited to a predetermined value or less, the target position of the step motor 54 is set to the overdrive-side operation limit, and the torque of the engine 20 is limited. In order to suppress the amount to 50 Nm, the pressure reducing valve 49 that supplies the hydraulic pressure to the secondary pulley 30b is locked, and even when the line pressure is generated but the secondary pulley pressure _Psec is low, the pulley position is shifted to the most overdrive side. By doing so, the torque capacity can be secured by the mechanical stoppers of the primary pulley and the secondary pulley, and belt slippage can be prevented. Further, even if the pressure regulator valve 40 fails and the pulley ratio remains at the intermediate pulley position due to insufficient hydraulic pressure, belt slippage can be prevented.
[0077]
(4) When it is determined that belt slippage has occurred, in order to increase the idle speed when the vehicle is stopped, secure the discharge amount of the oil pump 8 when the vehicle is stopped to prevent the belt slippage when starting. Can be.
[0078]
(5) Although it is possible to determine the slippage of the belt on the condition that the difference between the target oil pressure and the actual oil pressure is large, the surface of the belt and the pulley deteriorates due to aging, and the friction coefficient μ decreases. If hydraulic pressure is generated but the belt slips, belt slip cannot be detected. On the other hand, by detecting the belt slip by the method of the present embodiment, it is possible to reliably detect the belt slip even in a situation where the belt slip occurs despite the actual oil pressure reaching the target oil pressure. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main unit of a vehicle including a belt-type continuously variable transmission according to an embodiment.
FIG. 2 is a circuit diagram illustrating a configuration of a hydraulic circuit according to the embodiment.
FIG. 3 is a flowchart illustrating a flow of a belt slip determination control process in a CVT control unit.
FIG. 4 is a flowchart showing a flow of a belt protection control process at the time of belt slippage determination in a CVT control unit.
FIG. 5 is a time chart showing a belt protection control operation when a belt slippage is determined.
FIG. 6 is a map showing a predetermined time set according to acceleration.
[Explanation of symbols]
Reference Signs List 1 torque converter 2 lock-up clutch 3 belt-type continuously variable transmission 4 primary speed sensor 5 secondary speed sensor 6 hydraulic control valve unit 8 oil pump 9 control unit 10 accelerator opening sensor 11 oil temperature sensor 12 engine output shaft 13 speed change Machine input shaft 14 primary pressure sensor 15 secondary pressure sensor 16 engine speed sensor 17 throttle opening sensor 17a driven wheel sensor 18 engine 19 engine control unit (ECU)
Reference Signs List 20 forward / backward switching mechanism 31 fixed cone plate 32 movable cone plate 33 primary pulley cylinder chamber 34 belt 35 fixed cone plate 36 movable cone plate 37 secondary pulley cylinder chamber 38 driven shaft 40 pressure regulator valve 41, 42, 43, 44, 46 oil Line 45 Orifice 49 Pressure reducing valve 50 Pilot valve 51 Oil line 60 Clutch regulator valve 61 Oil line 70 Select switching solenoid 71 Lock-up solenoid 72, 73 Oil line 80 Select switching valve 81, 82, 83, 84 Oil line 90 Select control valve 91 Spool valve 92 Spring 93 Oil passage 100 Manual valve 101 Oil passage 102 Orifice

Claims (7)

A primary pulley with a variable pulley interval is provided on the main shaft on the engine side, a secondary pulley with a variable pulley interval is provided on a sub-shaft on the wheel side arranged in parallel with the main shaft, and a drive belt is wound between both pulleys, In a continuously variable transmission that continuously changes the speed by controlling the hydraulic pressure of both pulleys and changing the ratio of the winding diameter of the drive belt to both pulleys,
Speed ratio calculating means for calculating a speed ratio based on the primary pulley rotation speed and the secondary pulley rotation speed,
Belt slip determining means for determining that belt slip has occurred when the value of the speed ratio has been continuously deviated from the speed ratio region on the mechanism for a predetermined time;
A control device for a belt-type continuously variable transmission, comprising: The control device for a belt-type continuously variable transmission according to claim 1,
Providing an engine speed detecting means,
The belt slip determination means is means for determining that belt slip has occurred when the engine speed is equal to or higher than a predetermined speed that is estimated to be able to generate sufficient hydraulic pressure,
A control device for a belt-type continuously variable transmission, comprising: belt protection control means for performing belt protection control when it is determined that belt slippage has occurred. 3. The control device for a belt-type continuously variable transmission according to claim 2, wherein the belt protection control is a control for regulating an upper limit of an engine torque. 3. The control device for a belt-type continuously variable transmission according to claim 2, wherein the belt protection control is an upshift. 3. The control device for a belt-type continuously variable transmission according to claim 2, wherein the belt protection control is a control for regulating an upper limit of an engine speed. 3. The belt-type continuously variable transmission according to claim 2, wherein the belt protection control is a control for increasing an engine idle speed when the vehicle is stopped by a predetermined speed. Machine control device. The control device for a belt-type continuously variable transmission according to claim 1,
Providing acceleration detection means for detecting the acceleration of the vehicle,
The control device for a belt-type continuously variable transmission, wherein the belt slip determination unit sets the predetermined time longer as the detected acceleration is larger.

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