JP5262867B2 - Control device for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of an automatic transmission by controlling an excessive inertia torque working on the automatic transmission on sudden braking. <P>SOLUTION: If a driver operates a brake pedal (YES at S106) while an actual vehicle speed is lower than a threshold value (YES at S100) and driving wheels are idling on a low-&mu; road (YES at S102, S104), an ECU controlling a belt-type continuously variable transmission executes upshift control for decreasing a transmission ratio by a predetermined value (S108), and also executes clamping-force increasing control for increasing a belt clamping pressure by a predetermined value (S110). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to control of an automatic transmission for a vehicle, and more particularly to control of a belt type continuously variable transmission.

  A belt-type continuously variable transmission (CVT) mounted on a vehicle is used by being wound around a primary pulley connected to an engine, a secondary pulley connected to a drive wheel, and these pulleys. Belt. The primary pulley and the secondary pulley are each provided with a pair of sheaves whose groove width can be changed steplessly, and by changing the groove width of each pulley, the belt winding radius with respect to each pulley changes. As a result, the gear ratio can be continuously changed steplessly.

  In such a belt type continuously variable transmission, for example, Japanese Patent Application Laid-Open No. 2004-124968 discloses a technique for improving the belt durability by improving the accuracy of belt slip determination.

  In the control device for a belt type continuously variable transmission disclosed in Japanese Patent Application Laid-Open No. 2004-124968, the state in which the primary rotational speed is equal to or greater than the value obtained by multiplying the maximum speed ratio that can be taken by the mechanism by the secondary rotational speed continues for a predetermined time. When this happens, it is determined that belt slip has occurred, and belt protection control is performed to limit engine torque. Thereby, when the maximum gear ratio instantaneously becomes a value that cannot be taken by the mechanism due to a detection error of the sensor or the like, it is possible to improve the accuracy of determination of belt slip without erroneously determining belt slip. Furthermore, by limiting the engine torque, the input torque to the primary pulley can be suppressed and belt slippage can be prevented.

JP 2004-124968 A JP 2004-316717 A JP-A-7-217713

  By the way, when the driving wheel is idling on a road surface with a very low frictional resistance (so-called low μ road) and is suddenly braked (locked), excessive braking torque from the driving wheel side (attempts to suppress the rotation of the transmission). Torque) acts on the continuously variable transmission. Due to this brake torque, an excessive inertia torque (torque to continue the rotation of the transmission) from the engine side is input to the continuously variable transmission. Therefore, in a belt type continuously variable transmission that transmits power by frictional force, there is a risk of causing belt slip.

  However, if the engine torque is simply limited as in the control device disclosed in Japanese Patent Application Laid-Open No. 2004-124968, an excessive brake torque that acts during sudden braking and an excessive inertia torque that acts due to this brake torque. Is difficult, and there is a possibility that the belt slip described above cannot be suppressed.

  The present invention has been made to solve the above-described problems, and its object is to improve the durability of an automatic transmission by suppressing an excessive inertia torque that acts on the automatic transmission during sudden braking. It is to provide a control device that can.

  A control device according to a first aspect of the invention controls an automatic transmission for a vehicle that shifts the rotation of a driving force source and transmits it to driving wheels. The control device includes a determination unit that determines whether or not the vehicle is traveling on a low-friction road surface that causes slipping of drive wheels, and protects the automatic transmission when the vehicle is traveling on a low-friction road surface. And a control unit that executes shift control for changing a gear ratio of the automatic transmission.

  In the control device according to the second aspect of the invention, the shift control is an upshift control that changes the gear ratio of the automatic transmission to the high speed side.

A control device according to a third aspect of the invention includes a first detection unit that detects an actual traveling speed of the vehicle,
And a second detector for detecting the rotational speed of the drive wheel. The determination unit determines that the vehicle is traveling on the low friction road surface when the rotational speed of the drive wheel is higher than the speed according to the actual travel speed. The control unit executes the upshift control when the vehicle is traveling on the low friction road surface and when the actual traveling speed is lower than the predetermined speed.

  The control device according to a fourth aspect of the present invention further includes a third detection unit that detects whether or not a braking force that suppresses rotation of the drive wheels has occurred. The control unit performs upshift control when the vehicle is traveling on a low friction road surface and when braking force is generated.

  In the control device according to the fifth invention, the automatic transmission is a continuously variable transmission that transmits power by a belt wound around a first pulley connected to a driving force source and a second pulley connected to a driving wheel. It is a transmission. When the vehicle is traveling on a low-friction road surface, the control unit executes nipping pressure increase control for increasing the nipping pressure of the belt in addition to the upshift control.

A control device according to a sixth aspect of the invention includes a first detection unit that detects the rotational speed of the first pulley,
A second detection unit that detects a rotation speed of the second pulley, and the control unit calculates a slip ratio indicating a degree of slipping of the belt based on the rotation speed of the first pulley and the rotation speed of the second pulley. When the vehicle is traveling on a low friction road surface, upshift control is executed, and the belt clamping pressure is feedback-controlled so as to reduce the slip ratio below a predetermined ratio.

  According to the present invention, it is possible to suppress an excessive inertia torque that acts on the automatic transmission during sudden braking, and thus it is possible to improve the durability of the automatic transmission.

It is a figure which shows the structure of the vehicle by which the control apparatus which concerns on the 1st Embodiment of this invention is mounted. It is a figure which shows the relationship between the gear ratio of a belt type continuously variable transmission, and an output shaft torque. It is a figure which shows the relationship between the gear ratio of a belt-type continuously variable transmission, allowable input torque, and belt clamping pressure. It is a functional block diagram of a control device concerning a 1st embodiment of the present invention. It is a figure which shows the processing flow of the control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the processing flow of the control apparatus which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
With reference to FIG. 1, a power train of a vehicle including a control device according to the present embodiment will be described. In this embodiment, the case where the belt type continuously variable transmission 300 is used as the automatic transmission will be described. However, the automatic transmission to which the control device according to the present invention can be applied is a belt type continuously variable transmission. For example, it may be a toroidal continuously variable transmission or a stepped automatic transmission.

  As shown in FIG. 1, the power train of this vehicle is connected to engine 100, torque converter 200, forward / reverse switching device 290, belt type continuously variable transmission 300, differential gear 800, and differential gear 800. Drive wheels (not shown), driven wheels (not shown) to which power from the engine 100 is not transmitted, an ECU (Electronic Control Unit) 8000, and a hydraulic control unit 1100.

  The output shaft of engine 100 is connected to the input shaft of torque converter 200. Engine 100 and torque converter 200 are connected by a rotating shaft. An output shaft rotational speed (engine rotational speed) NE of engine 100 is detected by engine rotational speed sensor 430.

  The torque converter 200 includes a lock-up clutch 210 that directly connects the input shaft and the output shaft, a pump impeller 220 on the input shaft side, a turbine impeller 230 on the output shaft side, and a one-way clutch 250. It is comprised from the stator 240 which expresses an amplification function. Torque converter 200 and belt type continuously variable transmission 300 are connected by a rotating shaft. The output shaft rotational speed NT (turbine rotational speed NT) of the torque converter 200 is detected by the turbine rotational speed sensor 400.

  An oil pump 260 is provided between the torque converter 200 and the belt type continuously variable transmission 300. The oil pump 260 is a gear pump, for example, and operates as the pump impeller 220 on the input shaft side rotates. The oil pump 260 supplies hydraulic pressure to various solenoids of the hydraulic control unit 1100.

  The belt type continuously variable transmission 300 is connected to the torque converter 200 via a forward / reverse switching device 290. The belt type continuously variable transmission 300 includes an input side primary pulley 500, an output side secondary pulley 600, and a metal belt 700 wound around the primary pulley 500 and the secondary pulley 600. Primary pulley 500 includes a fixed sheave fixed to the primary shaft and a movable sheave supported on the primary shaft so as to be slidable only. The secondary pulley 600 includes a fixed sheave fixed to the secondary shaft and a movable sheave supported by the secondary shaft so as to be slidable only.

  The rotation speed (primary pulley rotation speed) NIN of the primary pulley 500 is detected by the primary pulley rotation speed sensor 410, and the rotation speed (secondary pulley rotation speed) NOUT of the secondary pulley 600 is detected by the secondary pulley rotation speed sensor 420. .

  Hydraulic oil is supplied to and discharged from hydraulic actuators (both not shown) of the primary pulley 500 and the secondary pulley 600, respectively. The speed change is performed by continuously changing the groove width between the fixed sheave and the movable sheave of each pulley 500, 600, thereby changing the belt wrapping radius to a larger or smaller value.

  The hydraulic control unit 1100 controls the hydraulic actuator of the primary pulley 500 so that the gear ratio of the belt-type continuously variable transmission 300 (primary pulley rotation speed NIN / secondary pulley rotation speed NOUT) becomes the target gear ratio transmitted from the ECU 8000. Controls the hydraulic pressure supplied.

  Further, the hydraulic control unit 1100 is supplied to the hydraulic actuator of the secondary pulley 600 so as to develop a tension necessary for transmitting the torque by pressing the movable sheave of the secondary pulley 600 toward the fixed sheave to sandwich the belt. Control the hydraulic pressure.

  The forward / reverse switching device 290 includes a double pinion planetary gear, a reverse (reverse) brake B1, and an input clutch C1. The input clutch C1 is also called a forward clutch or a forward clutch, and is always used in an engaged state when the vehicle moves forward.

  The ECU 8000 and the hydraulic control unit 1100 that control these power trains will be described.

  The ECU 8000 includes an engine rotational speed NE from the engine rotational speed sensor 430, a turbine rotational speed NT from the turbine rotational speed sensor 400, a primary pulley rotational speed NIN from the primary pulley rotational speed sensor 410, and a secondary pulley rotational speed sensor 420. Secondary pulley rotational speed NOUT is input.

  Further, a drive wheel speed sensor 440, an actual vehicle speed sensor 450, an accelerator position sensor 460, a brake pedal force sensor 470, and the like are connected to the ECU 8000 via a harness or the like.

  Drive wheel speed sensor 440 detects vehicle speed (drive wheel speed) VD based on the rotational speed of the drive wheel. The actual vehicle speed sensor 450 detects the actual speed (actual vehicle speed) VT of the vehicle based on the rotational speed of the driven wheel. The accelerator position sensor 460 detects an accelerator pedal operation amount (accelerator opening) ACC. The brake pedal force sensor 470 detects a brake pedal force (force that a driver steps on a brake pedal (not shown)) FB. Each of these sensors transmits a signal representing the detection result to ECU 8000.

  The actual vehicle speed sensor 450 is not necessarily limited to detecting the actual vehicle speed VT based on the rotational speed of the driven wheel. For example, the longitudinal acceleration of the vehicle may be detected, and the actual vehicle speed VT may be detected from the detected acceleration.

  ECU 8000 executes output control of engine 100, shift control of belt-type continuously variable transmission 300, belt clamping pressure control, engagement / release control of forward / reverse switching device 290, and the like.

  The output control of the engine 100 is performed by an electronic throttle valve, a fuel injection device, an ignition device (all not shown) and the like provided in the engine 100. The ECU 8000 controls the output of the engine 100 by outputting a control signal corresponding to the accelerator opening ACC to the electronic throttle valve, the fuel injection device, and the ignition device.

  Shift control of the belt-type continuously variable transmission 300, belt clamping pressure control, and engagement / release control of the forward / reverse switching device 290 are performed by a hydraulic control unit 1100.

  The hydraulic control unit 1100 includes a transmission speed control unit 1110, a belt clamping pressure control unit 1120, a line pressure control unit 1130, a lockup engagement pressure control unit 1132, a clutch pressure control unit 1140, and a manual valve 1150. Including.

  The ECU 8000 includes a shift control duty solenoid (1) (hereinafter also referred to as “DS (1)”) 1200 of the hydraulic control unit 1100 and a shift control duty solenoid (2) (hereinafter also referred to as “DS (2)”) 1210. A linear solenoid for belt clamping pressure control (hereinafter also referred to as “SLS”) 1220, a linear solenoid for line pressure control (hereinafter also referred to as “SLT”) 1230, and a duty solenoid for control of lock-up engagement pressure (hereinafter referred to as “DSU”). The control signal is output to 1240.

  Shift speed control unit 1110 controls the gear ratio of belt-type continuously variable transmission 300 by controlling the oil pressure of primary pulley 500 in accordance with the output oil pressures of DS (1) 1200 and DS (2) 1210.

  The belt clamping pressure control unit 1120 controls the belt clamping pressure by controlling the hydraulic pressure of the secondary pulley 600 according to the output hydraulic pressure of the SLS 1220.

  The line pressure control unit 1130 controls the line pressure according to the output hydraulic pressure of the SLT 1230. The line pressure is a hydraulic pressure obtained by adjusting the hydraulic pressure supplied by the oil pump 260 by a regulator valve (not shown).

  The lockup engagement pressure control unit 1132 controls the lockup clutch 210 according to the output hydraulic pressure of the DSU 1240.

  The manual valve 1150 operates in conjunction with the driver's operation of the shift lever to switch the oil passage. The clutch pressure control unit 1140 controls the hydraulic pressure supplied from the SLT 1230 to the input clutch C1 or the reverse brake B1 via the manual valve 1150 when the input clutch C1 or the reverse brake B1 is engaged.

  When the driver depresses the accelerator pedal, ECU 8000 sets a target gear ratio according to the vehicle speed and accelerator opening ACC, and DS (1) 1200, DS ( 2) Output control signals to 1210, SLS1220 and SLT1230.

  ECU 8000 sets the target gear ratio to a larger value (value on the lower speed side) as the vehicle speed is lower. ECU 8000 decreases the target gear ratio when performing an upshift.

  In a vehicle having the above-described configuration, the driver steps on the brake pedal and suddenly brakes the drive wheel while the drive wheel is slipping and slipping on a road surface having a very low frictional resistance (so-called low μ road) ( When locked, brake torque from the drive wheel side (torque to suppress rotation of the primary pulley 500) is input to the primary pulley 500 via the secondary pulley 600 and the belt 700.

  On the other hand, due to the brake torque from the drive wheel side, an excessive inertia torque (that is, torque for continuing the rotation of the primary pulley 500) from the engine 100 is input.

  Therefore, in the belt-type continuously variable transmission 300 that transmits power by frictional force, the belt 700 may slip.

  FIG. 2 shows the relationship between the gear ratio of the belt type continuously variable transmission 300 and the output shaft torque. As shown in FIG. 2, the output shaft torque is larger as the gear ratio is larger (that is, the gear ratio is lower). The greater the output shaft torque, the greater the inertia torque that acts during sudden braking.

  Therefore, the greater the gear ratio (that is, the lower the vehicle speed), the higher the possibility of belt slippage. Further, the smaller the gear ratio (that is, the higher the upshift), the smaller the inertia torque that acts during sudden braking.

  FIG. 3 shows the relationship among the gear ratio, allowable input torque, and belt clamping pressure of the belt type continuously variable transmission 300. Here, the allowable input torque is an upper limit value that can prevent belt slippage of torque input from engine 100 to primary pulley 500. As shown in FIG. 3, the allowable input torque increases and the belt slip hardly occurs as the gear ratio is reduced (that is, the upshift is performed) and the belt clamping pressure is increased.

  Therefore, in the present embodiment, it is determined that there is a high possibility of belt slippage due to excessive inertia torque when the brake is turned on when traveling on a low μ road at low vehicle speed, The upshift control for reducing the gear ratio is executed, and the clamping pressure increase control for increasing the belt clamping pressure is executed.

  FIG. 4 shows a functional block diagram of ECU 8000 which is a vehicle control apparatus according to the present embodiment. The ECU 8000 stores an input interface 8100 that receives information from each sensor and the like, and various information, programs, threshold values, maps, and the like, and data is read or stored from the arithmetic processing unit 8200 as necessary. Storage unit 8300, an arithmetic processing unit 8200 that performs arithmetic processing based on information from input interface 8100 and storage unit 8300, and an output interface 8400 that outputs a processing result of arithmetic processing unit 8200 to each device.

  Arithmetic processing unit 8200 includes a first condition determining unit 8210, a second condition determining unit 8220, a third condition determining unit 8230, a slip ratio calculating unit 8240, an upshift unit 8250, and a belt clamping pressure increasing unit 8260.

  First condition determination unit 8210 determines whether or not a first condition that actual vehicle speed VT is lower than a threshold value is satisfied. This threshold value is the vehicle speed upper limit value (the lower limit value of the gear ratio) at which the inertia torque is excessively applied to the primary pulley 500 so as to cause belt slip, assuming that the drive wheel is suddenly braked from the idle state. ).

  That is, as shown in FIG. 2, the lower the vehicle speed (the higher the gear ratio), the greater the inertia torque at the time of sudden braking, and belt slippage is likely to occur. In consideration of this point, the first condition determination unit 8210 compares the actual vehicle speed VT with a threshold value, so that if it is assumed that the driving wheel is suddenly braked from the idling state, belt slip occurs. It is determined whether or not the vehicle is traveling in a low vehicle speed region where an excessive inertia torque can act.

  Second condition determination unit 8220 determines whether or not a second condition that the vehicle is traveling on a low μ road is satisfied. This determination is to determine whether or not the driving wheel is actually idling, or whether or not the driving wheel is likely to idle. For example, the second condition determination unit 8220 satisfies the second condition when the driving wheel speed VD is higher than the actual vehicle speed VT by a predetermined speed or more (when it is detected that the driving wheel is actually idling). Judge that

  Based on information from brake pedal force sensor 470, third condition determination unit 8230 determines whether or not a third condition that the driver has pressed the brake pedal is satisfied. This determination is to determine the possibility of sudden braking when the driver steps on the brake pedal. Therefore, it is only necessary to determine that the third condition is satisfied when the driver is stepping on the brake pedal evenly (when the brake pedal force FB> 0), and it is necessary to determine that the driving wheel is actually suddenly braked. There is no.

  The slip ratio calculation unit 8240 calculates a slip ratio that is an index of the degree of slip of the belt 700. For example, the slip ratio calculation unit 8240 calculates the rotation radius of the belt 700 in the primary pulley 500 and the rotation radius of the belt 700 in the secondary pulley 600 based on the primary pulley groove width Lin and the secondary pulley groove width Lout, and these rotations. The speed ratio determined by the ratio of the radii is calculated as a speed ratio when it is assumed that no belt slip occurs (hereinafter also referred to as “assumed speed ratio γas”). Then, the slip ratio calculation unit 8240 calculates the value obtained by the primary pulley rotation speed NIN / assumed transmission gear ratio γas as the assumed rotation speed Nas of the secondary pulley 600 when it is assumed that belt slip does not occur, and the slip ratio ( (Nas−NOUT) / Nas. Note that the slip ratio may be calculated by another calculation method as long as the value becomes an index of the degree of slip of the belt 700.

  Upshift unit 8250 performs upshift control to decrease (upshift) the gear ratio by a predetermined amount when all of the above-described first condition, second condition, and third condition are satisfied. For example, upshift unit 8250 repeatedly outputs a gear ratio command value for decreasing the gear ratio by a predetermined amount to DS (1) 1200 or the like at a predetermined cycle time until the slip ratio decreases below the predetermined value. . The above-described upshift control may be performed when at least the second condition is satisfied.

  The belt clamping pressure increasing unit 8260 performs clamping pressure increase control for increasing the belt clamping pressure by a predetermined value when all of the above-described first condition, second condition, and third condition are satisfied. For example, the belt clamping pressure increasing unit 8260 repeatedly outputs a clamping pressure command value for increasing the belt clamping pressure by a predetermined amount to the SLS 1220 until the slip ratio decreases below a predetermined value at a predetermined cycle time. Note that the above-described clamping pressure increase control may be performed when at least the second condition is satisfied.

  The functions described above may be realized by software or hardware.

  FIG. 5 is a processing flow of ECU 8000 when the above-described functions are realized by software. This process is repeated at a predetermined cycle time.

  As shown in FIG. 5, at step (hereinafter abbreviated as S) 100, ECU 8000 determines whether or not actual vehicle speed VT is lower than a threshold value (whether or not the first condition is satisfied). to decide. As described above, this threshold value is the upper limit value of the vehicle speed at which an inertia torque that is excessively large enough to cause belt slippage on the primary pulley 500 when it is assumed that the drive wheel is suddenly braked from the idle state. It is set based on the lower limit value of the gear ratio. If an affirmative determination is made in this determination (YES in S100), an inertia torque that is excessively large enough to cause belt slippage acts on the primary pulley 500, assuming that the drive wheels are idling and suddenly braked. Then, the process proceeds to S102. Otherwise (NO in S100), this process ends.

  In S102, ECU 8000 determines whether or not the drive wheel is actually idling. For example, ECU 8000 determines that the drive wheel is actually idling when drive wheel speed VD is higher than actual vehicle speed VT by a predetermined speed or more. If a positive determination is made in this determination (YES in S102), the process proceeds to S104. Otherwise (NO in S102), this process ends.

  In S104, ECU 8000 determines that the road surface on which the vehicle is traveling is a low μ road.

  In S106, ECU 8000 determines whether or not the brake is turned on (whether or not the driver steps on the brake pedal). The ECU 8000 determines that the brake is turned on when the brake depression force FB> 0. If a positive determination is made in this determination (YES in S106), the process proceeds to S108. Otherwise (NO in S106), this process ends.

  In S108, ECU 8000 performs upshift control for reducing the gear ratio by a predetermined value.

  In S110, ECU 8000 performs clamping pressure increase control for increasing the belt clamping pressure by a predetermined value.

  In S112, ECU 8000 determines whether or not the slip ratio has decreased below a predetermined value. If a positive determination is made in this determination (YES in S112), this process ends. Otherwise (NO in S112), the process returns to S108, and upshift control (S108) and pinching pressure increase control (S110) are repeatedly executed.

  As described above, ECU 8000 serving as the control device according to the present embodiment is upshifted when the first condition, the second condition, and the third condition described above are satisfied (S108), and the belt clamping pressure increases. (S110). In other words, when it is assumed that the drive wheel is actually locked from the idle state and the vehicle is traveling in a low vehicle speed region where an inertia torque that is excessive enough to cause belt slippage (YES in S100), the drive wheel When the vehicle is idling (YES in S102) and the driver steps on the brake pedal (YES in S106), the allowable input torque is increased by upshift (S108) and increase in belt clamping pressure (S110). (See FIG. 3).

  As a result, even when the drive wheels are actually locked, it is possible to appropriately prevent belt slippage. Therefore, the durability of the belt 700 can be improved.

  In a vehicle equipped with an anti-lock brake system (ABS) that controls the braking force so that the driving wheels are not locked during braking, the driving wheels are not locked by the operation of the ABS. However, normally, the ABS does not operate in a low vehicle speed region where inertia torque is large when the drive wheels are locked. Therefore, even in a vehicle equipped with an ABS, belt slippage may occur when the drive wheels are locked, and it is desirable to apply the control according to the present embodiment.

<Second Embodiment>
Hereinafter, the control device according to the present embodiment will be described. In the first embodiment described above, when all of the first condition, the second condition, and the third condition are satisfied, both the upshift control and the pinching pressure increase control are executed. It was. On the other hand, in the present embodiment, when all of the first condition, the second condition, and the third condition are satisfied, only the upshift control is executed first, and the slip ratio is predetermined after the upshift control. If it does not decrease below the value, the belt clamping pressure is gradually increased until the slip ratio decreases below a predetermined value. The configuration according to the present embodiment other than these is the same as the configuration according to the above-described first embodiment. The same reference numerals are assigned to the same components. Their functions are the same. Therefore, detailed description thereof will not be repeated here.

  FIG. 6 is a flowchart showing a processing flow of ECU 8000 according to the present embodiment. In the flowchart shown in FIG. 6, the same steps as those in the flowchart shown in FIG. 5 are given the same step numbers. The processing is the same for them. Therefore, detailed description thereof will not be repeated here.

  In S200, ECU 8000 determines whether or not the slip ratio has decreased below a predetermined value. That is, ECU 8000 determines whether or not the slip ratio has decreased below a predetermined value without performing clamping pressure increase control after executing upshift control in the process of S108. If a positive determination is made in this determination (YES in S200), this process ends. Otherwise (NO in S200), the process proceeds to S202.

  In S202, ECU 8000 performs clamping pressure increase control for increasing the belt clamping pressure by a predetermined value.

  In S204, ECU 8000 determines whether or not the slip ratio has decreased below a predetermined value. If a positive determination is made in this determination (YES in S204), this process ends. Otherwise (NO in S204), the process returns to S202, and the clamping pressure increase control (S110) is repeatedly executed.

  As described above, ECU 8000 serving as the control device according to the present embodiment, when all of the first condition, the second condition, and the third condition are satisfied (YES in S100, YES in S102, First, only upshift control is executed (S108).

  Then, if the slip ratio decreases below a predetermined value after the upshift control (YES in S200), the clamping pressure increase control is not performed. Thus, belt slip can be suppressed without causing unnecessary tension on the belt 700 due to an increase in pinching pressure. Therefore, the durability of the belt 700 can be further improved.

  On the other hand, if the slip ratio has not decreased below the predetermined value (NO in S200), the belt clamping pressure is gradually increased until the slip ratio decreases below the predetermined value (S202, S204). Thereby, belt slip can be prevented reliably.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 engine, 200 torque converter, 210 lock-up clutch, 220 pump impeller, 230 turbine impeller, 240 stator, 250 one-way clutch, 260 oil pump, 290 forward / reverse switching device, 300 belt type continuously variable transmission, 400 turbine rotation Speed sensor, 410 Primary pulley rotational speed sensor, 420 Secondary pulley rotational speed sensor, 430 Engine rotational speed sensor, 440 Drive wheel speed sensor, 450 Actual vehicle speed sensor, 460 Accelerator position sensor, 470 Brake pedal force sensor, 500 Primary pulley, 600 Secondary Pulley, 700 belt, 800 differential gear, 1100 hydraulic control unit, 1110 shift speed control unit, 1120 belt clamping pressure control unit, 1130 line Pressure control unit, 1132 lock-up engagement pressure control unit, 1140 clutch pressure control unit, 1150 manual valve, 8000 ECU, 8100 input interface, 8200 arithmetic processing unit, 8210 first condition determination unit, 8220 second condition determination unit, 8230 Third condition determination unit, 8240 slip ratio calculation unit, 8250 upshift unit, 8260 belt clamping pressure increase unit, 8300 storage unit, 8400 output interface.

Claims (4)

A control device for an automatic transmission for a vehicle that shifts the rotation of a driving force source and transmits it to driving wheels,
The automatic transmission is a continuously variable transmission that transmits power by a belt wound around a first pulley connected to the driving force source and a second pulley connected to the driving wheel,
The controller is
A first detector for detecting an actual traveling speed of the vehicle;
A second detector for detecting the rotational speed of the drive wheel;
A determination unit that the rotational speed of the drive wheels when it is higher than a speed corresponding to the actual traveling speed said, it is determined that the vehicle is traveling on a low friction road surface slip of the driving wheels occurs,
A calculation unit that calculates a slip ratio indicating a degree of slipping of the belt based on a rotation speed of the first pulley and a rotation speed of the second pulley;
Fast speed ratio of the automatic transmission until when the vehicle is traveling the low friction road surface, and the actual traveling speed the is lower than the predetermined speed, the slip rate is smaller than a predetermined value And a control unit that executes upshift control to be changed to the side . The control device further includes a third detection unit that detects whether or not a braking force that suppresses rotation of the drive wheel has occurred,
The control unit performs the upshift control when the vehicle is traveling on the low friction road surface, and when the actual traveling speed is lower than a predetermined speed and when the braking force is generated. The control device for an automatic transmission according to claim 1, wherein the control device is executed. Prior Symbol controller, when the vehicle is traveling the low friction road surface, and when the actual running speed the is lower than a predetermined speed, until the slip rate is smaller than a predetermined value, the up in addition to the shift control to perform a clamping increasing control for increasing the clamping pressure of the belt, control apparatus for an automatic transmission according to claim 1. A control device for an automatic transmission for a vehicle that shifts the rotation of a driving force source and transmits it to driving wheels,
The automatic transmission is a continuously variable transmission that transmits power by a belt wound around a first pulley connected to the driving force source and a second pulley connected to the driving wheel,
The controller is
A first detector for detecting an actual traveling speed of the vehicle;
A second detector for detecting the rotational speed of the drive wheel;
A determination unit that determines that the vehicle is traveling on a low-friction road surface on which the drive wheel slips when a rotational speed of the drive wheel is higher than a speed according to the actual travel speed; ,
A calculation unit that calculates a slip ratio indicating a degree of slipping of the belt based on a rotation speed of the first pulley and a rotation speed of the second pulley;
When the vehicle is traveling on the low friction road surface and the actual traveling speed is lower than a predetermined speed , an upshift control is performed to change the gear ratio of the automatic transmission to a high speed side , slip ratio after the upshift control includes a control section for feedback controlling the clamping pressure of the belt so as to reduce than the predetermined value the slip ratio when not decreased below a predetermined value, the automatic transmission Control device.

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