JP2008267467A - Control device for continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of driveability by correcting a speed controlled variable in an environment with an engine torque is reduced even at the same accelerator opening, for example, at an altitude. <P>SOLUTION: This control device for a continuously variable transmission includes a gear ratio control means and a gear shift start delay determining means. The gear ratio control means controls the gear ratio of the continuously variable transmission based on a vehicle operation condition shown by, for example, the accelerator opening and a vehicle speed. The gear shift start delay determining means determines gear shift start delay according to engine torque buildup. Since the engine torque is reduced, for example, at the altitude, the gear shift start delay is set large. The gear ratio control means controls the gear ratio at timing in response to the gear shift start delay. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to control of a transmission ratio of a continuously variable transmission, and more particularly to control in consideration of a decrease in engine torque caused by a decrease in atmospheric pressure at a high altitude.

  As a transmission used in a vehicle, a continuously variable transmission (CVT) capable of continuously changing a gear ratio is known. Patent Document 1 discloses a control device that controls a throttle opening so that an engine torque becomes a target torque and controls a continuously variable transmission based on a transmission torque calculated from the target torque. Based on this, it is described that the engine target torque is corrected. Further, in Patent Document 2, a ratio of a required intake air amount obtained based on a throttle opening and an actual intake air amount is used as a correction coefficient in a control device for an automatic transmission, and a shift is performed according to the correction coefficient. It is described that the judgment is corrected. In addition, Patent Documents 3 and 4 describe techniques for performing shift control in consideration of altitude (high altitude / low altitude) and atmospheric pressure in a transmission.

JP 2001-47892 A JP-A-5-231528 JP 2003-314675 A JP-A-8-135782

  In a continuously variable transmission, the rotational speed of the primary sheave increases during a shift (downshift). When trying to increase the rotational speed from a state where the sheave is rotating as a rigid body at a certain speed, a force that overcomes the inertial force is required. For this reason, a part of the engine torque is used for this. That is, a loss (inertia loss) occurs at the time of shifting. Inertia loss can be reduced by reducing the rate of change of rotation.

  In high altitudes and the like, the engine torque decreases even with the same accelerator opening, so the rate of loss during shifting as described above increases. For this reason, the driving force of the vehicle may decrease during the shift, and drivability may deteriorate.

  In addition, since inertia loss occurs during gear shifting as described above, if gear shifting is performed before a certain amount of engine torque is output, it takes time until driving force is generated in the vehicle due to the influence of inertia loss. End up.

  The present invention has been made in view of the above points. In an environment where the engine torque is reduced even at the same accelerator opening, such as at high altitudes, the shift control amount is corrected to prevent deterioration of drivability. Let it be an issue.

  In one aspect of the present invention, a control device for a continuously variable transmission includes a gear ratio control unit that controls a gear ratio of the continuously variable transmission based on a driving state of the vehicle, and a gear change according to a rise of engine torque. Shift start delay determining means for determining a start delay, and the speed ratio control means controls the speed ratio at a timing corresponding to the shift start delay.

  The control apparatus includes a gear ratio control unit and a shift start delay determining unit. The gear ratio control means controls the gear ratio of the continuously variable transmission based on the driving state of the vehicle indicated by, for example, the accelerator opening and the vehicle speed. The shift start delay is a time for delaying the timing at which the shift ratio control means controls the shift ratio, that is, a delay time. The shift start delay determining means determines the shift start delay according to the rising of the engine torque. For example, at high altitudes, the engine torque is small, so the shift start delay is set large. The gear ratio control means controls the gear ratio at a timing corresponding to the gear shift start delay.

  In one aspect of the control device for the continuously variable transmission, the shift start delay determining means determines an air amount correction coefficient that is a ratio between the required intake air amount of the engine and the actual intake air amount of the engine. An amount correction coefficient determining means; and a shift start delay determining means for determining a shift start delay based on the air amount correction coefficient. Accordingly, when the intake air amount varies due to a difference in atmospheric pressure such as high altitude and the engine torque decreases, the shift start timing can be corrected appropriately.

  In a preferred example of the control device for the continuously variable transmission, the shift start delay determining means calculates a base shift start delay based on the engine speed and the accelerator opening, and the air Means for determining a shift start delay correction coefficient based on the amount correction coefficient, means for calculating a shift start delay based on the base shift start delay correction coefficient, and the base shift start delay correction coefficient.

  In another preferred example of the control device for the continuously variable transmission, the shift start delay correction coefficient is 1 when the air amount correction coefficient is 1, and increases as the air amount correction coefficient increases. The air amount correction coefficient decreases as the air amount correction coefficient decreases. As a result, as the engine torque rises more slowly, the shift start timing can be delayed, and the delay in driving force generation can be suppressed.

  Another aspect of the control device for the continuously variable transmission includes a transmission speed determination unit that determines a transmission speed based on the air amount correction coefficient, and the transmission ratio control unit is configured to change the speed at the transmission speed. Control the ratio. When the engine torque rises slowly, the rate of inertia loss at the time of shifting can be reduced and the driving force can be secured by slowing down the shifting speed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Vehicle configuration)
A configuration example of a power transmission system of a vehicle to which the present invention is applied is shown in FIG. In FIG. 1, a power source 1 is connected to a speed change mechanism 2, and an output shaft 3 of the speed change mechanism 2 is connected to left and right drive wheels 5 via a differential 4. The power source 1 includes various power sources that can be used for a vehicle, such as an internal combustion engine such as a gasoline engine or a diesel engine, or an electric motor such as a motor, and a device that combines these internal combustion engine and electric motor. In the following description, as the power source 1, fuel is directly injected into the cylinder, and the injection amount and timing are controlled to control the so-called direct injection gasoline engine capable of homogeneous combustion or stratified combustion, or the throttle opening degree. An example in which a gasoline engine equipped with an electronic throttle valve that can be freely controlled will be described.

  The engine 1 is configured to be electrically controllable, and an electronic control unit (E-ECU) 6 mainly including a microcomputer for the control is provided. The electronic control unit 6 is configured to control at least the output of the engine 1, and the engine speed NE and the requested driving amount such as the accelerator opening PA are input as data for the control. .

  The required drive amount is a signal for increasing / decreasing the output of the engine 1 and is obtained by electrically processing the operation amount signal of the acceleration / deceleration operation device 7 such as an accelerator pedal operated by the driver and the operation amount. Can be used.

  The transmission mechanism 2 includes a fluid transmission mechanism 8, a forward / reverse switching mechanism 9, and a continuously variable transmission (CVT) 10. The fluid transmission mechanism 8 is a device configured to transmit torque between an input-side member and an output-side member via a fluid such as oil, and is adopted as an example in a general vehicle. A torque converter can be mentioned. The fluid transmission mechanism 8 includes a direct coupling clutch (not shown). The direct coupling clutch is a clutch configured to directly connect an input side member and an output side member by mechanical means such as a friction plate, and is a damper made of an elastic body such as a coil spring for buffering. It has.

  The input member of the fluid transmission mechanism 8 is connected to the output member of the engine 1, and the output member of the fluid transmission mechanism 8 is connected to the input member of the forward / reverse switching mechanism 9. The forward / reverse switching mechanism 9 is constituted by a double pinion type planetary gear mechanism as an example, and although not particularly shown, either the sun gear or the carrier is an input element and the other is an output element, and a ring gear is selected. And a clutch means for integrating the entire planetary gear mechanism by selectively connecting any two rotating elements of the sun gear, the carrier and the link gear. That is, the forward state is set by engaging the clutch means, and the reverse state is set by engaging the brake means.

  A continuously variable transmission 10 shown in FIG. 1 is a mechanism capable of continuously (continuously) changing the ratio between the rotation speed of the input side member and the rotation speed of the output side member, that is, the gear ratio. A belt type continuously variable transmission, a toroidal type continuously variable transmission, or the like can be employed.

  An example of the belt type continuously variable transmission 10 will be briefly described with reference to FIG. The belt type continuously variable transmission 10 includes a driving pulley (primary pulley) 20, a driven pulley (secondary pulley) 21, and a belt 22 wound around the pulleys 20 and 21. Each of the pulleys 20 and 21 includes a fixed sheave 23 and 24 and a movable sheave 25 and 26 that approaches and separates from the fixed sheave 23 and 24. The movable sheave 25 and 26 are connected to the fixed sheave 23 and 24. And hydraulic actuators 27 and 28 for pressing in the approaching direction.

  The driving pulley 20 is attached to the input shaft 29, and the driven pulley 21 is attached to the output shaft 30 disposed in parallel with the input shaft 29. The hydraulic actuator 28 in the driven pulley 21 is supplied with a hydraulic pressure corresponding to a required drive amount typified by the accelerator opening PA, and applies a tension necessary for transmitting torque to the belt 22. . Hydraulic pressure is supplied to and discharged from the hydraulic actuator 27 of the driving pulley 20 so as to obtain a gear ratio for making the rotational speed of the input shaft 29 coincide with the target input rotational speed. That is, by changing the groove width (interval between the fixed sheaves 23 and 24 and the movable sheaves 25 and 26) in the pulleys 20 and 21, the wrapping radius of the belt 22 around the pulleys 20 and 21 is changed to be large or small. Shifting is executed.

  Therefore, in the continuously variable transmission 10 shown in FIG. 2, the minimum speed side shift is performed with the belt 22 having a minimum radius of wrapping around the driving pulley 20 and the belt 22 having a maximum radius of wrapping around the driven pulley 21. Ratio (maximum transmission ratio) γmax is set, and on the contrary, the maximum speed is obtained when the winding radius of the belt 22 with respect to the driving pulley 20 is maximum and the winding radius of the belt 22 with respect to the driven pulley 21 is minimum. The transmission gear ratio (minimum transmission ratio) γmin is set.

  Control of each state of engagement / release of the direct coupling clutch in the transmission mechanism 2 and half-engagement with slip, switching of forward / reverse in the forward / reverse switching mechanism 9, and control of the gear ratio in the continuously variable transmission 10 are as follows: Basically, the control is performed based on the traveling state of the vehicle represented by the vehicle speed, the accelerator opening, and the like. For this control, an electronic control unit (T-ECU) 13 composed mainly of a microcomputer is provided.

  The electronic control unit 13 is connected to the above-described electronic control unit 6 for the engine so as to be able to perform data communication. On the other hand, as data for control, data such as the vehicle speed SPD, the output rotational speed NO of the transmission mechanism 2 and the input rotational speed NIN Is entered. In addition, the transmission mechanism 2 is normally set in accordance with the stopped state (parking position: P), the reverse state (reverse position: R), the neutral state (neutral position: N), and the traveling state of the vehicle. A range switching device 14 for selecting each state (position) such as an automatic forward state (drive position: D) is provided. The range switching device 14 is electrically connected to the electronic control device 13. Yes.

  With the above configuration, the gear ratio of the continuously variable transmission 10 is controlled according to the driving state of the vehicle. Specifically, a required driving force is calculated based on a required driving amount such as an accelerator opening degree and a traveling condition such as a vehicle speed, and a required output is obtained based on the required driving force. The rotation speed for generating the required output in the driving state with the optimum fuel consumption is obtained as the target output rotation speed (target input rotation speed for the continuously variable transmission 10), and the actual input rotation speed is the target input rotation speed. The transmission ratio of the continuously variable transmission 10 is controlled so as to be a number. Further, the target output torque is calculated based on the required output and the engine speed, and the throttle opening and the fuel amount of the engine 1 are controlled so as to output the target output torque.

(Correction coefficient Kshift)
As described above, the accelerator opening is used for the shift control of the continuously variable transmission 10 as an indication of the load state of the engine. For the purpose of optimization and the like, various intake air amount variable mechanisms such as a variable valve timing mechanism and an idle speed control mechanism are provided in the engine. For this reason, the accelerator opening does not necessarily represent the load state of the engine faithfully. Further, since the air pressure is different between the flat land and the highland, the actual intake air amount is different even if the accelerator opening is the same, and the load state of the engine changes accordingly. For this reason, the correction coefficient Kshift for correcting the shift control based on the intake air amount is used. The correction coefficient Kshift is expressed by the following equation.

Kshift = (required intake air amount QNTA) / (actual intake air amount Qm)
Specifically, the required intake air amount, that is, the calculated intake air amount QNTA is obtained based on the engine speed and the accelerator opening, and the actual intake air amount Qm is obtained by the intake air amount detection means. Then, the correction coefficient Kshift is obtained by the above formula. In this specification, the correction coefficient Kshift is also referred to as an “air amount correction coefficient” in order to distinguish it from a shift speed correction coefficient and a shift start delay correction coefficient which will be described later. In high altitudes and the like, the actual intake air amount Qm is smaller than the required intake air amount QNTA because of the atmospheric pressure, and the correction coefficient Kshift increases.

  As a specific example, the correction coefficient Kshift is calculated as described above, and this is multiplied by the accelerator opening to correct the accelerator opening. Then, the gear ratio is determined based on the corrected accelerator opening, the vehicle speed, etc., and the shift control is executed.

(Shift speed control)
As described above, at the time of shifting (downshifting), inertia loss occurs due to the structure of the continuously variable transmission. When the correction coefficient Kshift increases at high altitudes or the like, the engine torque decreases, so that the ratio of the inertia loss to the engine torque increases at the time of shifting. As a result, the driving force during shifting is reduced and drivability is deteriorated. In view of this, the speed change speed is reduced in accordance with the correction coefficient Kshift to reduce the ratio of inertia loss, thereby preventing a reduction in driving force during the speed change. Note that the shift speed refers to the speed at which the shift operation is performed, and the slow shift speed refers to the slow shift operation.

  Specifically, a shift speed correction coefficient A for correcting the shift speed is introduced. The smaller the value of the shift speed correction coefficient A, the slower the shift speed, and the greater the value, the faster the shift speed. FIG. 3A shows the relationship between the shift speed correction coefficient A and the correction coefficient Kshift. When the correction coefficient Kshift is 1, the shift speed correction coefficient A is 1. The shift speed correction coefficient A decreases as the correction coefficient Kshift increases, and the shift speed correction coefficient A increases as the correction coefficient Kshift decreases. For example, since the correction coefficient Kshift is large at high altitudes, the shift speed correction coefficient A is a small value, and the shift operation is performed slowly.

  FIG. 3B shows an example of a shift operation when the correction coefficient Kshift = 1 (low altitude) and when the correction coefficient Kshift> 1 (high altitude). It is assumed that the accelerator opening changes at the same timing as shown. The engine torque in the highland area indicated by the broken line graph 61 increases more slowly than the engine torque in the lowland area indicated by the solid line graph 51. That is, the engine torque rises more slowly in the highland area than in the flatland area. Therefore, at high altitude, the shift speed, that is, the change speed of the input rotation speed is slowed down by the shift speed correction coefficient A. When the shift speed correction coefficient A is 1, the graph 52 is a solid line. When the shift speed correction coefficient A is less than 1, the rate of increase of the input rotational speed (the slope of the graph 62) decreases as shown by the broken line graph 62. , Shifting will be performed slowly. By doing so, the ratio of inertia loss to engine torque can be reduced, driving force can be secured, and drivability can be prevented from deteriorating.

  FIG. 4 is a flowchart of the shift control accompanied with the shift speed control. This process is mainly executed by the electronic control unit 13. When there is a shift request, for example, when the shift device 16 is operated, the electronic control device 13 reads the vehicle speed as the required drive amount (step S101) and also reads the accelerator opening as the travel condition (step S102). Then, the electronic control unit 13 calculates the required driving force based on the vehicle speed and the accelerator opening, calculates the required output based on the required driving force, and sets the target input rotational speed that is the rotational speed at which the required output is obtained. Calculate (step S103). At this time, the accelerator opening is corrected by the correction coefficient Kshift as necessary.

  On the other hand, the electronic control unit 13 reads the actual input rotation speed of the engine 1 and determines the gear ratio so that the actual input rotation speed becomes the target input rotation speed (step S104).

  Further, the electronic control unit 13 determines the base shift speed X based on the accelerator opening, the vehicle speed, and the like (step S105). The base shift speed X is a base value of the shift speed before correction. Next, the electronic control unit 13 reads the correction coefficient Kshift (step S106), calculates the shift speed correction coefficient A with reference to the map illustrated in FIG. 3A (step S107), and the base shift speed X Is multiplied by a shift speed correction coefficient A to determine a corrected shift speed (step S108). Then, the electronic control unit 13 executes shift control at the corrected shift speed so as to achieve the calculated gear ratio (step S109). As a result, as illustrated in FIG. 3B, when the correction coefficient Kshift is greater than 1 at high altitudes or the like, the shift speed becomes slow, so that the ratio of the inertia loss to the engine torque during the shift is relatively The driving force can be ensured.

(Control of shift start delay)
In the above embodiment, the shift speed is corrected according to the correction coefficient Kshift in order to reduce the ratio of the inertia loss during the shift. Instead, the shift start delay can be corrected according to the correction coefficient Kshift. The shift start delay is a delay time at which the shift mechanism 2 is operated to start shifting.

  As described above, inertia loss occurs at the time of shifting, and therefore, if the shifting operation is started before the engine torque reaches a certain level, it takes time until the driving force is generated. The higher the correction coefficient Kshift at high altitudes, the more slowly the engine torque rises, and this phenomenon becomes more prominent. Therefore, the shift start delay is corrected so as to delay the start time of the shift operation as the correction coefficient Kshift is larger. Thereby, since the shift is started after the engine torque rises to a certain level, the influence of the inertia loss can be reduced, and the driving force can be obtained quickly.

  FIG. 5A is a graph showing the relationship between the shift start delay correction coefficient B and the correction coefficient Kshift. When the correction coefficient Kshift is 1, the shift start delay correction coefficient B is 1. Further, as the correction coefficient Kshift increases, the shift start delay correction coefficient increases and the shift start timing is delayed.

  FIG. 5B shows an example of shift control when the shift start delay is controlled. When the accelerator opening increases, the engine torque increases accordingly. However, the engine torque rises more slowly in the case of the high ground shown by the broken line graph 61 than in the case of the flat ground shown by the solid line graph 51. In the case of flat ground, the speed change operation starts at time t1, and thereafter, the input rotational speed increases as shown by the graph 52. On the other hand, since the correction coefficient Kshift> 1 in the highland area, the shift start delay correction coefficient B> 1 as shown in FIG. 5A, the shift start timing is delayed by the delay D until time t2, and then As indicated by the graph 64, the input rotational speed increases. Thus, the shift can be started in a state where the engine torque is increased by an amount corresponding to the delay of the shift start by the delay D, and a delay in the generation of the driving force can be suppressed.

  FIG. 6 shows a flowchart of the shift start time delay calculation process. Note that the method for calculating the gear ratio associated with the speed change operation is the same as the processing shown in FIG.

  The electronic control unit 13 reads the engine speed and the accelerator opening (steps S201 and S202), and calculates the base shift start delay Y based on the accelerator opening and the engine speed (step S203). The base shift start delay Y is the base value of the shift start delay before correction. Next, the electronic control unit 13 reads the correction coefficient Kshift (step S204), and calculates the shift start delay correction coefficient B with reference to the map illustrated in FIG. 5A (step S205). Then, the electronic control unit 13 calculates the corrected shift start delay D by multiplying the base shift start delay Y by the shift start delay correction coefficient B (step S206). Based on the corrected shift start delay D thus obtained, the electronic control unit 13 delays the shift start timing, for example, as shown in FIG.

  In the above example, the shift start delay is controlled instead of the shift speed control. However, both the shift speed control and the shift start delay control may be executed.

It is a block diagram which shows the structural example of the power transmission system of the vehicle to which this invention is applied. The structural example of a continuously variable transmission is shown. The map of a shift speed correction coefficient and the correction example of a shift speed are shown. It is a flowchart of the shift process accompanied by correction of the shift speed. A map of a shift start delay correction coefficient and a shift start delay correction example are shown. 6 is a flowchart of a shift start delay correction coefficient calculation process.

Explanation of symbols

1 Power source (engine)
2 Transmission mechanism 6 Electronic control unit (E-ECU)
7 Acceleration / deceleration operating device 10 Continuously variable transmission 13 Electronic control unit (T-ECU)
14 Range switching device

Claims (5)

A control device for a continuously variable transmission,
Gear ratio control means for controlling the gear ratio of the continuously variable transmission based on the driving state of the vehicle;
Shift start delay determining means for determining a shift start delay in response to a rise in engine torque,
The control device for a continuously variable transmission, wherein the speed ratio control means controls the speed ratio at a timing according to the shift start delay. The shift start delay determining means includes
An air amount correction coefficient determining means for obtaining an air amount correction coefficient that is a ratio of a required intake air amount of the engine and an actual intake air amount of the engine;
The control device for a continuously variable transmission according to claim 1, further comprising a shift start delay determining unit that determines a shift start delay based on the air amount correction coefficient. The shift start delay determining means includes
Means for calculating a base shift start delay based on the engine speed and the accelerator opening;
Means for determining a shift start delay correction coefficient based on the air amount correction coefficient;
3. The continuously variable transmission control device according to claim 2, further comprising means for calculating a shift start delay based on the base shift start delay and the base shift start delay correction coefficient.   The shift start delay correction coefficient is 1 when the air amount correction coefficient is 1, increases as the air amount correction coefficient increases, and decreases as the air amount correction coefficient decreases. The control device for a continuously variable transmission according to claim 3. Shift speed determining means for determining a shift speed based on the air amount correction coefficient;
The continuously variable transmission control device according to any one of claims 1 to 4, wherein the transmission ratio control means controls the transmission ratio at the transmission speed.

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