JP5200860B2 - Variable speed control device for continuously variable transmission and variable speed control method for continuously variable transmission - Google Patents

Description

  The present invention relates to a technical field of a transmission control device for a continuously variable transmission and a transmission control method for a continuously variable transmission.

Patent Document 1 discloses that when coasting with the accelerator pedal fully closed (coast traveling), the coast rotational speed, which is the target input rotational speed of the belt-type continuously variable transmission, is set to a higher value so that the idle speed can be reduced by rapid deceleration. A technique is disclosed in which when the engine speed is lowered to a number, the engine speed is less than the speed at which the fuel is to be restored and the engine stall is prevented.
JP 2006-112302 A (see paragraph 0007)

  However, in the prior art, since the coast rotational speed is high, the engine brake torque is increased, and the lockup release vehicle speed for releasing the lockup clutch is increased. At this time, if the amount of braking applied to the vehicle is small, the time from when the lock-up clutch is released until the vehicle stops becomes longer, resulting in a problem of worsening fuel consumption.

  The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to provide a transmission control device for a continuously variable transmission and a continuously variable transmission capable of achieving both improvement in fuel consumption and prevention of engine stall. Another object is to provide a speed change control method for a machine.

In order to achieve the above object, in the speed change control device for a continuously variable transmission according to the present invention, the greater the braking force acting on the vehicle, the higher the target coast speed that is the target input speed when the accelerator opening is zero. The target coasting speed when the braking force is less than or equal to a predetermined threshold is set lower than the minimum value of the target input speed when the accelerator opening exceeds zero .

In the present invention, when the brake amount is small, the coast rotational speed becomes low, and the lockup release vehicle speed can be lowered, so that fuel efficiency can be improved. On the other hand, when the brake amount is large, the coast rotational speed increases, so that engine stall can be avoided.
As a result, it is possible to achieve both improvement in fuel efficiency and prevention of engine stall.

  Hereinafter, the best mode for carrying out the present invention will be described based on examples.

First, the configuration will be described.
FIG. 1 is a diagram illustrating a control system of a continuously variable transmission according to a first embodiment.
The transmission control device for a continuously variable transmission according to the first embodiment includes a torque converter 1, a lockup clutch 2, a belt type continuously variable transmission (hereinafter referred to as CVT) 3, a primary rotational speed sensor 4, and a secondary rotational speed sensor. 5, hydraulic control valve unit 6, oil pump 8 driven by engine, CVT control unit 9, accelerator opening sensor 10, engine speed sensor 11, brake pedal stroke sensor (braking force detection means) 41.

  A torque converter 1 is connected to the engine output shaft as a rotation transmission mechanism, and a lockup 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 that fixes the pinion carrier 22 to the transmission case, and a forward clutch 25 that integrally connects the transmission input shaft 13 and the pinion carrier 22.

  A primary pulley 30 a of the CVT 3 is provided at the 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 30 a has a fixed conical plate 31 that rotates integrally with the transmission input shaft 13, a V-shaped pulley groove that is disposed opposite to the fixed conical plate 31, and is shifted by hydraulic pressure that acts on the primary pulley cylinder chamber 33. The movable conical plate 32 is movable in the axial direction of the machine input shaft 13.

  The secondary pulley 30 b 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 that is disposed opposite to the fixed conical plate 35, and is driven by hydraulic pressure that acts on the secondary pulley cylinder chamber 37. The movable conical plate 36 is movable in the axial direction.

  A drive gear (not shown) is fixed to the driven shaft 38, and this drive gear drives a drive shaft that reaches a wheel (not shown) via a pinion, a final gear, and a differential gear provided on the idler shaft.

  The rotational force input from the engine output shaft 12 to the CVT 3 as described above 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 in the order of primary pulley 30a → belt 34 → secondary pulley 30b → driven shaft 38 → drive gear → idler gear → idler shaft → pinion → final gear → differential device.

  During 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, whereby the primary pulley 30a The rotation ratio between the secondary pulley 30b, that is, the gear ratio can be changed. Such control for changing the width of the V-shaped pulley groove is performed by hydraulic control to the primary pulley cylinder chamber 33 or the secondary pulley cylinder chamber 37 via the CVT control unit 9.

  The CVT control unit 9 includes an accelerator opening APO from the accelerator opening sensor 10, an engine speed Ne from the engine speed sensor 11, a primary speed Npri from the primary speed sensor 4, and a secondary speed sensor 5. Secondary rotation speed Nsec, pulley clamp pressure from pulley clamp pressure sensor 14, and brake pedal stroke BPS from brake pedal stroke sensor 41 are input. The CVT control unit 9 calculates a control signal based on each input signal and outputs the control signal to the hydraulic control valve unit 6.

  The hydraulic control valve unit 6 is input with accelerator opening, engine speed, gear ratio, input shaft speed, primary hydraulic pressure, etc., and supplies control pressure to the primary pulley cylinder chamber 33 and the secondary pulley cylinder chamber 37. Shift control is performed.

FIG. 2 is a control block diagram of the CVT control unit 9. The CVT control unit 9 includes a target input rotational speed calculation section (target input rotational speed calculation means) 9a, a transmission control section (transmission control means) 9b, A rotation speed changing section (coast rotation speed changing means) 9c.
The target input rotational speed calculation unit 9a calculates the target input rotational speed Nt ^* according to the accelerator opening APO and the vehicle speed VSP. The vehicle speed VSP is converted from the secondary rotational speed Nsec from the secondary rotational speed sensor 5.

The speed change control unit 9b controls the speed ratio of the CVT 3 so that the target input speed Nt ^* calculated by the target input speed calculation part 9a is obtained.
The coasting speed changing unit 9c changes the target coasting speed Nc ^* , which is the target input speed when the accelerator opening is zero, according to the magnitude of the braking force detected by the brake pedal stroke sensor 41.

The coast speed changing unit 9c estimates the magnitude of the braking force acting on the vehicle from the brake pedal stroke detected by the brake pedal stroke sensor 41, and the accelerator opening APO is determined according to the estimated magnitude of the braking force. The target coasting speed Nc ^* , which is the target input speed at zero, is set and output to the target input speed calculating unit 9a.
When the target coast speed Nc ^* is output from the coast speed change section 9c, the target input speed calculation section 9a sets the target coast speed Nc ^* as the target input speed Nt ^* .

[Shift control process]
FIG. 3 is a flowchart showing the flow of the shift control process executed by the CVT control unit 30, and each step will be described below. This control process is repeatedly executed at a predetermined calculation cycle.

  In step S1, the accelerator opening APO, the secondary rotation speed Nsec, and the brake pedal stroke BPS are input, and the process proceeds to step S2. The secondary rotation speed Nsec is input to the target input rotation speed calculation unit 9a, and the brake pedal stroke BPS is input to the coast rotation speed change unit 9c. The accelerator opening APO is input to the target input rotation speed calculation unit 9a and the coast rotation speed change unit 9c.

  In step S2, the coast rotational speed changing unit 9c determines whether or not the accelerator opening APO is zero. If YES, the process proceeds to step S3. If NO, the process proceeds to step S4.

In step S3, the target input rotational speed calculation unit 9a calculates the target input rotational speed Nt ^* based on the vehicle speed VSP calculated from the accelerator opening APO and the secondary rotational speed Nsec, and the process proceeds to step S6. The target input rotation speed Nt ^* is obtained with reference to the shift map shown in FIG.

The shift map in FIG. 4 is set so that the vehicle speed VSP is taken on the horizontal axis and the target input speed Nt ^* is taken on the vertical axis, and the target input speed Nt ^* is determined for each accelerator opening APO. Therefore, when the accelerator opening APO is constant and the vehicle speed VSP increases, the engine speed does not change much and the vehicle speed VSP changes. When the driver depresses the accelerator, the engine speed increases according to the amount of depression.

In step S4, the coast rotational speed changing unit 9c calculates the target coast rotational speed Nc ^* according to the brake amount estimated from the brake pedal stroke BPS, and the process proceeds to step S5. The target coast speed Nc ^* is obtained with reference to the target coast speed map shown in FIG.

Target coasting rotation speed map in FIG. 5, the braking amount is zero to a threshold value is a constant target coasting rotation speed Nc ^*, exceeds the threshold value, set as higher braking amount becomes larger target coasting rotation speed Nc ^* increases doing.

In step S5, the target input rotational speed Nc ^* input from the coast rotational speed changing section 9c is set to the target input rotational speed Nt ^* in the target input rotational speed calculating section 9a, and the process proceeds to step S6.

In step S6, the transmission control unit 9b executes the transmission ratio control so that the input rotational speed Nt matches the target input rotational speed Nt ^*, and the process proceeds to return.

Next, the operation will be described.
[Coast rotation speed changing action]
In general, in a belt-type or toroidal-type continuously variable transmission, the vehicle speed and the accelerator opening are used as variables, and the target input rotation speed (target input rotation speed) is determined using a control map that maps shift correlations from these variables. Set. Then, the speed ratio is controlled so that the target input speed is achieved at the current vehicle speed, that is, the output speed of the continuously variable transmission.

  In Patent Document 1 described above, when coasting with the accelerator pedal fully closed (coast traveling), the coast rotational speed, which is the target input rotational speed of the continuously variable transmission, is set to a higher value so that the idle rotational speed can be reduced by rapid deceleration. A technique for preventing the engine stall from occurring when the engine rotational speed is lowered to a level lower than the rotational speed at which the fuel is to be restored is disclosed.

  That is, during coasting, fuel cut is performed to stop fuel supply to the engine for the purpose of improving fuel efficiency.If the coasting speed is low, when the brake is depressed and deceleration is started, The descent time is short (for example, about 50 ms).

  When the engine speed drops to the idle speed in such a short time, the engine speed is actually detected, and when the fuel return speed is corrected based on the detected engine speed, the engine speed is corrected during the correction calculation. There is a possibility that the engine stalls when the number is lower than the speed at which the fuel should be returned.

  Therefore, in Patent Document 1, the coast rotational speed is set higher in order to prevent the engine stall. However, since the coast rotational speed is high, the engine brake torque increases, and the lockup release that releases the lockup clutch is performed. The vehicle speed increases. At this time, if the amount of braking applied to the vehicle is small, the time from when the lock-up clutch is released until the vehicle stops becomes longer, resulting in deterioration of fuel consumption.

On the other hand, in the transmission control apparatus of the first embodiment, the target coast speed Nc ^* is increased as the brake amount is increased. For this reason, as shown in FIG. 6, the target coast speed Nc ^* is low when the brake amount is small, and is large when the brake amount is large.

  Therefore, as shown in FIG. 7, when the vehicle is stopped with a small brake amount from the coast state, the coast speed can be lowered and the lockup release vehicle speed is lowered, so that the travel time after releasing the lockup clutch can be shortened. The fuel consumption can be improved.

  On the other hand, when the brake amount is large, as shown in FIG. 8, since the coast rotational speed can be set high, it takes longer for the engine speed to drop to the idle rotational speed after the brake is depressed and deceleration is started. , Engine stall can be avoided. When the brake amount is large, the time from the start of deceleration until the vehicle stops is short, so even if the lockup release vehicle speed increases, the running time in the lockup clutch release state is short, There is no negative impact on fuel consumption.

Further, in the first embodiment, when the brake amount is equal to or less than a certain threshold value, the target coast speed Nc ^* is made constant. That is, when the brake amount is equal to or less than the threshold value, the transmission ratio of the CVT 3 is maintained constant, so that the energy consumption consumed by the shift can be reduced and the maximum fuel efficiency improvement effect can be obtained.

Further, in the first embodiment, the target coast speed Nc ^* when the braking force is equal to or less than the threshold value is set lower than the minimum value of the target input speed Nt ^* when the accelerator opening APO exceeds zero. Here, when the coast rotational speed is set higher, the target input rotational speed when the accelerator opening exceeds zero is smaller than the target input rotational speed (coast rotational speed) when the accelerator opening is zero. That is, when the accelerator is depressed from the coast state, the engine speed decreases, which gives the driver a feeling of strangeness.

On the other hand, in the first embodiment, when the accelerator is depressed from the coast state, the target input rotational speed Nt ^* increases, so that it is possible to prevent the engine rotational speed from decreasing and to prevent the driver from feeling uncomfortable.

Next, the effect will be described.
In the continuously variable transmission control device of the first embodiment, the following effects can be obtained.

(1) A target input speed calculation unit 9a that calculates a target input speed Nt ^* of the CVT 3 according to the accelerator opening APO and the vehicle speed VSP, and a target input speed Nt calculated by the target input speed calculation unit 9a ^{* The} shift control unit 9b that controls the transmission ratio of the CVT 3, the brake pedal stroke sensor 41 that detects the braking force that acts on the vehicle, and the braking force that is detected by the brake pedal stroke sensor 41 increases as the ^* is obtained. A coast speed changing unit 9c that increases the target coast speed Nc ^* , which is the target input speed Nt ^* when the accelerator opening APO is zero. Thereby, both improvement in fuel consumption and prevention of engine stall can be achieved.

(2) When the braking force is equal to or less than the predetermined threshold value, the coast speed changing unit 9c maintains the target coast speed Nc ^* at a constant value, so that the maximum fuel efficiency improvement effect can be obtained.

(3) The coast speed change unit 9c sets the target coast speed Nc ^* when the braking force is equal to or less than the threshold value to be lower than the minimum value of the target input speed Nt ^* when the accelerator opening APO exceeds zero. . Thereby, the uncomfortable feeling accompanying the fall of the engine speed when stepping on the accelerator from the coast state can be prevented.

(4) A continuously variable transmission that calculates the target input speed Nt ^* of CVT3 according to the accelerator opening APO and the vehicle speed VSP, and controls the gear ratio of CVT3 so that the calculated target input speed Nt ^* is obtained. In this shift control method, the larger the braking force acting on the vehicle, the higher the target coast speed Nc ^* , which is the target input speed Nt ^* when the accelerator opening APO is zero. Thereby, both improvement in fuel consumption and prevention of engine stall can be achieved.

(Other examples)
The best mode for carrying out the present invention has been described with reference to the embodiments based on the drawings. However, the specific configuration of the present invention is not limited to that shown in the embodiments, and the gist of the present invention. Even if there is a design change that does not change the value, it is included in the present invention.

In the embodiment, an example in which a belt type continuously variable transmission is used as a continuously variable transmission has been shown. However, even when applied to a vehicle equipped with a toroidal continuously variable transmission, for example, similar effects can be obtained. it can.
Moreover, although the example which used the brake pedal stroke sensor was shown as a braking force detection means which detects the braking force which acts on a vehicle in the Example, you may use a master cylinder pressure sensor and a wheel cylinder pressure sensor.

It is a figure which shows the control system of the continuously variable transmission of Example 1. FIG. FIG. 3 is a control block diagram of the CVT control unit 9 according to the first embodiment. 4 is a flowchart showing a flow of a shift control process executed by the CVT control unit 30 of the first embodiment. 3 is a shift map according to the vehicle speed VSP and the accelerator opening APO according to the first embodiment. 3 is a target coast speed map according to the brake amount of the first embodiment. 3 is a shift map showing a target coasting speed corresponding to a brake amount according to the first embodiment. It is a time chart which shows the fuel consumption improvement effect | action in case a brake amount is small. It is a time chart which shows the engine stall prevention effect in case the amount of brakes is large.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Torque converter 2 Lockup clutch 4 Primary rotational speed sensor 5 Secondary rotational speed sensor 6 Hydraulic control valve unit 8 Oil pump 9 Control unit 9a Target input rotational speed calculation part (target input rotational speed calculation means)
9b Shift control unit (shift control means)
9c Coast speed changing part (coast speed changing means)
DESCRIPTION OF SYMBOLS 10 Accelerator opening sensor 11 Engine rotation speed sensor 12 Engine output shaft 13 Transmission input shaft 14 Pulley clamp pressure sensor 20 Forward / reverse switching mechanism 21 Ring gear 22 Pinion carrier 23 Sun gear 24 Reverse brake 25 Forward clutch 30 Control unit 30a Primary pulley 30b Secondary pulley 31 Fixed conical plate 32 Movable conical plate 33 Primary pulley cylinder chamber 34 Belt 35 Fixed conical plate 36 Movable conical plate 37 Secondary pulley cylinder chamber 38 Drive shaft 41 Brake pedal stroke sensor (braking force detecting means)

Claims (3)

Target input speed calculating means for calculating the target input speed of the continuously variable transmission according to the accelerator opening and the vehicle speed;
Shift control means for controlling the gear ratio of the continuously variable transmission so that the target input rotation speed calculated by the target input rotation speed calculation means is obtained;
Braking force detection means for detecting braking force acting on the vehicle;
Coasting speed changing means for increasing the target coasting speed, which is the target input speed when the accelerator opening is zero, as the braking force detected by the braking force detecting means is larger;
Equipped with a,
The coast rotational speed changing means sets the target coast rotational speed when the braking force is equal to or less than a predetermined threshold to be lower than the minimum value of the target input rotational speed when the accelerator opening exceeds zero. A variable speed control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to claim 1,
The coasting rotation speed changing means, if the braking force is less than or equal to the threshold value, the shift control device for a continuously variable transmission, characterized by maintaining said target coasting rotation speed constant. Shift control of the continuously variable transmission that calculates the target input rotational speed of the continuously variable transmission according to the accelerator opening and the vehicle speed, and controls the transmission ratio of the continuously variable transmission so that the calculated target input rotational speed is obtained. In the method
The higher the braking force acting on the vehicle, the higher the target coast speed, which is the target input speed when the accelerator opening is zero,
A continuously variable transmission, wherein the target coast speed when the braking force is equal to or less than a predetermined threshold is set lower than a minimum value of the target input speed when the accelerator opening exceeds zero. Shift control method.

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