JPH0417294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a speed ratio control device for a continuously variable transmission for a vehicle, and in particular to a technology that provides both favorable drivability and fuel economy in a state of re-acceleration following vehicle deceleration. It is.

Technical field In a continuously variable transmission for a vehicle that continuously changes the speed of the engine and transmits it to the wheels, there is a rotation speed detection means for detecting the rotation speed of the engine, and a required load amount detection means required for the engine. , target rotational speed determining means for sequentially determining a target rotational speed of the engine based on the required load amount from a predetermined relationship; A speed ratio control device including a speed ratio adjusting means for adjusting the speed ratio of a step-change transmission has been considered. If such a speed ratio control device is used, the engine rotation can be made to match the target rotation speed with the best fuel consumption rate, so that favorable fuel economy can be obtained over the entire engine rotation range, especially in steady running conditions. However, it has the disadvantage that sufficient drivability and fuel economy cannot be obtained when the vehicle is reaccelerated following deceleration. That is, even when the vehicle is decelerating when the accelerator operation amount is almost zero, the engine rotation speed is controlled to match the target rotation speed that is determined to be an extremely low value corresponding to the accelerator operation amount, and When the vehicle is in a re-acceleration state where the accelerator operation is large again, the engine rotation speed is made to match the target rotation speed that is largely determined in accordance with the amount of accelerator operation, so the engine rotation speed increases. The width is large, and the amount of change in the speed ratio of the continuously variable transmission becomes large, which reduces the transmission efficiency of the continuously variable transmission and requires a long time to accelerate the vehicle, making it difficult to achieve sufficient re-acceleration (drivability) and fuel economy This makes it impossible to have sex.

Purpose of the Invention The present invention has been made against the background of the above circumstances, and its purpose is to provide a continuously variable transmission for a vehicle that provides high drivability and fuel economy in a re-acceleration state following vehicle deceleration. An object of the present invention is to provide a speed ratio control device.

Structure of the Invention In order to achieve the above object, the speed ratio control device for a continuously variable transmission for a vehicle of the present invention comprises: (1) deceleration state determining means for determining the deceleration state of the vehicle; (3) a timer for determining that a predetermined time has elapsed since the start of deceleration of the vehicle; (3) a period from the start of deceleration of the vehicle until the timer determines that the predetermined time has elapsed;
A rotational speed change suppressing means for suppressing a rotational speed change of the engine.

Effects of the Invention With this arrangement, as shown in the claim correspondence diagram in FIG. 1, the timer can determine that a predetermined period of time has elapsed since the deceleration state determining device determines that the vehicle has decelerated. , and the engine rotational speed change is suppressed by the rotational speed change suppressing means until the predetermined time elapses. In other words, when the vehicle decelerates, changes in the engine rotational speed are suppressed until a predetermined period of time elapses from the start of deceleration, so when the vehicle decelerates, the amount of accelerator operation is almost zero, and the target rotation is determined to be a significantly smaller value. Compared to the conventional case where the actual engine rotational speed is lowered to follow the speed, changes in engine rotational speed are suppressed and the engine rotational speed is maintained at a relatively high value even in such a deceleration state. It is. Therefore, in the reacceleration state that follows such deceleration, the target rotational speed is determined to be a large value according to the amount of accelerator operation, but the engine rotational speed is maintained at a relatively high value during deceleration. Therefore, even during re-acceleration, the range of increase in the engine rotational speed and the range of change in the speed ratio of the continuously variable transmission are relatively small, which limits the decrease in the transmission efficiency of the continuously variable transmission, resulting in high re-acceleration performance (drivability). ) and at the same time high fuel economy.
Furthermore, as a result of suppressing changes in engine rotational speed when the vehicle is decelerating, the engine rotational speed is maintained at a relatively high value, but in such a case, the amount of accelerator operation is essentially zero. Because of this condition, fuel economy will not be affected by this condition.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

In FIG. 2, the engine 10 includes a clutch 1.
A belt-type continuously variable transmission 14 is connected through the belt-type continuously variable transmission 14, and after the rotation of the engine 10 is continuously changed by the belt-type continuously variable transmission 14, it is transmitted to wheels (not shown). There is. The belt type continuously variable transmission 14 includes an input shaft 16 connected to the clutch 12, a variable pulley 18 with a variable effective diameter attached to the input shaft 16, an output shaft 20, and an output shaft 20.
Variable pulley 2 with variable effective diameter attached to 0
2, a transmission belt 24 stretched between variable pulleys 18 and 22, and variable pulleys 18 and 22.
hydraulic cylinders 26 and 28 that change the effective diameter by changing the width of the V-groove. The variable pulleys 18 and 22 are fixed rotating bodies 30 and 32 fixed to the input shaft 16 and the output shaft 20, respectively.
and movable rotating bodies 34 and 36 attached to the input shaft 16 and the output shaft 20 so as to be movable in the axial direction but not rotatable around the axes, and the movable rotating bodies 34 and 36 are attached to the hydraulic cylinder 26.
By being driven in the axial direction by hydraulic pressure applied to the space within the transmission belt 28, the hanging diameter (effective diameter) of the transmission belt 24 can be continuously changed. And hydraulic cylinder 2
8 is constantly supplied with line hydraulic pressure via an oil path 46 (to be described later), and the amount of hydraulic oil (hydraulic hydraulic pressure) in the hydraulic cylinder 26 is adjusted by a speed ratio control valve 38, so that the movable rotating body 34 and The speed ratio of the continuously variable transmission 14 is changed by changing the balance of forces applied to the continuously variable transmission 36. Note that the pressure receiving area of the movable rotary body 34 is set larger than that of the movable rotary body 36.

The line oil pressure is from the oil tank 40 to the pump 4.
The hydraulic oil pressure-fed by 2 is regulated by a pressure regulating valve 44, and is supplied to the speed ratio control valve 38 and the hydraulic cylinder 28 via an oil passage 46.
is supplied to. The pressure regulating valve 44 includes a linear solenoid driven by a pressure regulating signal SP, which will be described later, and a valve element driven by the linear solenoid, and allows hydraulic oil pumped from the pump 42 to escape to the oil tank 40. The line oil pressure is adjusted by changing the amount according to the pressure adjustment signal SP. The speed ratio control valve 38 includes a linear solenoid driven by a speed ratio signal SS, which will be described later, and a valve element driven by the linear solenoid. The amount of hydraulic oil supplied to the hydraulic cylinder 26 (hydraulic pressure) is changed by communicating with the hydraulic cylinder 26 and changing its circulation area.
At the same time, the hydraulic oil discharge amount (hydraulic pressure) in the hydraulic cylinder 26 is adjusted by communicating the oil passage 48 and the return oil passage 50 to the oil tank 40 and changing the flow area thereof. That is, the oil passage 48 and the oil passages 46 and 50 are controlled by the speed ratio control valve 38.
In a state where the communication with the hydraulic cylinder 26 is substantially cut off and the amount of hydraulic oil in the hydraulic cylinder 26 is kept constant, the speed ratio is fixed, while in a state where the oil passage 48 and the oil passage 46 are communicated with each other, the hydraulic pressure remains constant. The amount of hydraulic oil (hydraulic pressure) in the cylinder 26 is increased and the variable pulley 18
As the effective diameter of the variable pulley 22 is increased,
The effective diameter of is made smaller and the speed ratio is increased. On the contrary, the speed ratio is reduced by making the oil passage 48 and the oil passage 50 communicate with each other.

The gas pedal 5 is attached to the intake pipe of the engine 10.
A throttle valve 54 connected to the throttle valve 2 is attached, and a throttle signal, which is a voltage corresponding to the opening degree θ of the throttle valve 54, is generated by a throttle sensor 56 as a required load detection means attached to the throttle valve 54. TH is A/D converter 5
8 and is supplied to the I/O port 59. Also,
The input shaft 16 and the output shaft 20 are provided with a rotation sensor 6 as a rotation speed detection means for detecting their rotation.
0 and a rotation sensor 62 as a vehicle speed detection means are respectively attached.The rotation sensor 60 supplies a pulsed rotation signal SE corresponding to the rotation of the engine 10 to the I/F circuit 64, while the rotation sensor 62 detects the vehicle speed. Pulse rotation signal compatible with
SC is supplied to the I/F circuit 64. I/F circuit 6
4 converts the rotation signals SE and SC into code signals representing pulses per unit time and sends them to the I/O
Supplied to port 59. The I/O port 59 connects the CPU 66, RAM 68,
It is connected to ROM70, and CPU66 is connected to ROM70.
70 RAM according to the pre-stored program
68, the signal supplied to the I/O port 59 is processed, and the speed ratio signal SS that commands the speed ratio and its change rate is sent via the D/A converter 72 and the drive circuit 74. While being supplied to the speed ratio control valve 38, a pressure regulation signal SP that commands the pressure of the line oil pressure is supplied to the pressure regulation valve 44 via the D/A converter 72 and the drive circuit 74. The drive circuit 74 is a so-called power amplifier, which amplifies the power of the speed ratio signal SS and the pressure regulation signal SP outputted from the D/A converter 72 by a predetermined gain, and outputs the power of the speed ratio control valve 38 and the pressure regulation valve. It supplies 44 linear solenoids.

FIG. 3 is a control block diagram of this embodiment.

In the target rotational speed determining means 76, the target rotational speed Ne' is determined based on the opening degree θ of the throttle valve 54 representing the required load amount from the pre-stored relationship shown in FIG. The target rotational speed Ne' is a value determined in advance so that the required horsepower corresponding to the opening degree θ of the throttle valve 54 can be obtained at the minimum fuel efficiency. In the deceleration state determining means 78, the vehicle speed detecting means 8
The deceleration state of the vehicle is determined according to the sign of the difference between the actual vehicle speed determined at 0 and the vehicle speed determined a predetermined time ago. The counting means 82 determines that a predetermined period of time has elapsed since the deceleration state of the vehicle was determined by the deceleration state determining means 78, and the time interval determining means 84 determines that the deceleration of the vehicle is started. A time interval is determined between when the counting means 82 determines that a predetermined time has elapsed. That is, the counting means 82 and the time interval determining means 8
4 constitutes the timekeeping means. In the rotational speed change suppressing means 86, the content of the target rotational speed Ne' is determined by the rotational speed detecting means 88 only within the time interval determined by the time interval determining means 84.
is changed to the actual rotational speed Ne determined in . In the shift control control means 90, the vehicle speed V detected by the vehicle speed detection means 80, in other words, the rotation speed No of the output shaft of the continuously variable transmission 14, and the actual rotation speed Ne of the engine 10, in other words, ,
The actual speed ratio e is determined based on the rotational speed Ni of the input shaft of the continuously variable transmission 14, while the target speed ratio e' is determined to match the actual rotational speed Ne with the target rotational speed Ne'. and the speed ratio adjusting means 92
A speed ratio signal SS is supplied to the speed ratio control valve 38, and the speed ratio e of the belt type continuously variable transmission 14 is changed so that the difference between e and e' becomes zero.

On the other hand, the engine torque detecting means 94 detects the actual torque of the engine 10 based on the pre-stored relationship shown in FIG. Detects the output torque T. The line pressure determination means 96 determines the actual torque T of the engine 10, the actual rotational speed Ne of the engine 10 detected by the rotational speed detection means 88, and the actual rotational speed Ne of the engine 10 detected by the vehicle speed detection means 80 from a predetermined relationship. Continuously variable transmission 1
The line oil pressure of the oil passage 46 is determined based on the output shaft rotation speed No. 4. The pressure regulating valve adjusting means 98 receives a pressure regulating signal SP which is a control voltage for maintaining the line oil pressure determined by the line pressure determining means 96.
is supplied to the pressure regulating valve 44. As a result, the line oil pressure is maintained at a minimum pressure within a range where the transmission belt 24 does not slip, thereby preventing power loss and deterioration in the durability of the transmission belt 24 due to excessive line oil pressure.

The operation of this embodiment will be explained below with reference to the flowchart shown in FIG.

First, step S1 is executed, and the opening degree θ of the throttle valve 54 and the actual rotational speed Ne of the engine 10 are read based on the signals TH and SE.
It is stored in RAM68. Then, step S2 corresponding to the target rotational speed determination means 76 is executed, and the target rotational speed is determined based on the opening degree θ of the throttle valve 54 from the predetermined relationship shown in FIG.
Ne′ is calculated, and then step S3 corresponding to the deceleration state determining means 78 is executed.
It is determined whether the content of the flag FV indicating the deceleration state of the vehicle is zero. When the vehicle is not in a deceleration state, the content of flag FV is 1, so the speed ratio control routine in step S6, which will be described later, is executed. However, when the vehicle is in a deceleration state and the content of flag FV is zero, Step S3 is executed and the contents of the time counter (register) described later are TC ₁
It is determined whether or not is smaller than a predetermined constant time _t1 .

Here, the contents of the flag FV are determined by the interrupt routine shown in FIG. 7, which is executed at regular intervals. That is, step SW1 is executed to determine whether or not the content of timer flag FT is 1. If it is not 1, the interrupt routine is terminated, but if it is 1, step SW1 is executed.
SW2 and below are executed. The contents of this timer flag FT are set to 1 at regular time intervals.
In steps SW2 and SW3, 1 is added to the contents of predetermined time counters _TC1 and _TC2, respectively, and then step SW4 is executed.
It is determined whether the count value TC ₁ is smaller than a predetermined constant time t ₂ or not. The fixed time _t2 corresponds to a predetermined fixed time interval for detecting changes in vehicle speed and determining the acceleration state of the vehicle, and is set larger than the execution cycle of the interrupt routine. It is something. step
In SW4, if the count value _TC2 is smaller than the fixed time _t2 , the interrupt routine is terminated, but if it is larger, step SW5 is executed and the actual vehicle speed V is read based on the signal SC. Step SW6 is executed to determine whether the actual vehicle speed V is smaller than the previously read vehicle speed Vo. If it is smaller, it means that the vehicle is decelerating, so step SW7 is executed and the contents of flag FV are cleared to zero. Subsequently, steps SW8 and SW9 are executed and the coefficient value TC ₂
is cleared to zero, the content of the previous vehicle speed Vo is set to a value V-α slightly smaller than the actual vehicle speed V, and the content of the timer flag FT is set to zero. The content of the previous vehicle speed Vo is V-α
This is because the actual rotational speed Ne of the engine 10 is set to the target rotational speed so that the actual rotational speed Ne of the engine 10 is not judged to be deceleration in a slight deceleration state where the vehicle speed decrease value is within α.
This is to improve fuel economy by matching Ne′. On the other hand, if the actual vehicle speed V is greater than the previous vehicle speed Vo in step SW6, step SW10 is executed and the content of flag FV is set to 1 to represent the acceleration state of the vehicle, and step SW11 is executed. , the contents of count value TC ₁ are cleared to zero. By executing this step SW11, the content of the count value _TC1 is increased at regular intervals as long as the vehicle is in a deceleration state, and the step SW2 corresponds to the counting means 82. It is something to do.

Returning to FIG. 6, if it is determined that the content of the flag FV is zero and the vehicle is in a deceleration state by executing step S3, step S4 corresponding to the time interval determining means 84 is executed, and the calculation is performed. It is determined whether the numerical value TC ₁ is smaller than a predetermined constant value t ₁ . If the size is not small, proceed to step S6 above.
is executed, but if it is still small, step S5 corresponding to the rotational speed change suppressing means 86 is executed and the contents of the target rotational speed Ne' are changed to the actual rotational speed Ne. As a result, when the speed ratio control routine of step S6 is executed as described later, the deviation between the target value and the actual value is made zero, and the rotational speed change ΔNe' of the engine 10 is controlled to be zero. be.

The speed control routine 1 is executed as shown in FIG.

That is, in the speed ratio control routine, step SR1 is executed first, and the rotation signals SE and
Based on SC, the rotational speed Ni of the input shaft 16 and the rotational speed of the output shaft 20 of the belt type continuously variable transmission 14.
No is calculated. Then, step SR2 is executed, and the continuously variable transmission 1
The actual speed ratio e (=No/Ni) of 4 is calculated, and step SR3 is executed to determine the target speed ratio.
e′ (=No/Ni′) is calculated. Next, step SR4 is executed, and the target speed ratio e' becomes the minimum speed ratio e.
It is determined whether or not it is smaller than min. If it is smaller, step SR5 is executed and the content of the target speed ratio e' is set to the minimum speed ratio e min, but if it is not smaller, step SR6 is executed. Target speed ratio
It is determined whether e' is smaller than the maximum speed ratio e max. If the target speed ratio e' is not smaller than the maximum speed ratio emax, step SR7 is executed and the content of the target speed ratio e' is set to the maximum speed ratio emax, but if it is smaller, the next step SR8 is executed. executed.

In step SR8, the deviation Δe between the target speed ratio e' and the actual speed ratio e is calculated, and the step
In SR9, the flow control voltage Vf, which is the control amount to make the deviation Δe zero, is determined according to the following equation (1), and the speed ratio signal SS representing the flow control voltage Vf is used for speed ratio control. It is supplied to the valve 38 to adjust the speed ratio e of the continuously variable transmission 14. That is, steps SR1 to SR8 correspond to the speed change control means 90, and step SR9 corresponds to the speed ratio adjusting means 92.

Vf=K ₁ ·e+K ₂ ·Δe (1) However, K ₁ and K ₂ are constants.

Next, step SR10 is executed, and a step corresponding to the engine torque detection means 94 is executed.
SR10 is executed and the actual torque T of the engine 10 is calculated from the predetermined relationship shown in FIG. Then, step SR11 corresponding to the line pressure determining means 94 and the pressure regulating valve adjusting means 98 is executed, and the pressure regulating valve control voltage Vp, which is a control amount for controlling the line pressure, is calculated according to the following equation (2) stored in advance. At the same time, a pressure regulation signal SP representing the voltage Vp is supplied to the pressure regulation valve 44.

Vp=f(T, Ni, No)...(2) In this way, according to this embodiment, the step
In S5, the contents of the target rotational speed Ne' are changed to Ne, so that changes in the rotational speed Ne are suppressed within a certain time _t1 from the deceleration start time A, as shown by the solid line in FIG. The speed Ne is maintained higher than in the conventional case shown by the broken line. As a result, when the accelerator pedal 52 is operated after re-acceleration start time B, the increase in the engine speed Ne is small and the change in the speed ratio e is made small, so the transmission efficiency of the continuously variable transmission 14 is maintained. This results in high fuel economy and good drivability (re-acceleration). In addition,
Even if the engine speed Ne is maintained higher than before when the vehicle is decelerating, the amount of accelerator operation is essentially zero in such a case, so fuel economy will not be impaired. be. Furthermore, in a continuously variable transmission, the more the speed ratio is changed, the more the transmission efficiency inevitably decreases in the process.

Next, another embodiment of the present invention will be described. In addition,
In the following description, parts common to the above-described embodiments are given the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 10, step S3 in FIG.
It may be configured such that steps S7 to S10 are executed between and S4. That is, steps S7 and S8 corresponding to the suppression rotational speed determination means 100 described later are executed, and the vehicle speed V is read based on the signal SC, and the suppression is performed based on the relationship shown in FIG. 11 determined in advance based on the vehicle speed. The rotational speed Ne ₁ is determined. In addition, the 11th
The one-dot chain line in the figure is the optimum value during road loading (during an experiment in which running resistance is applied using a dynamometer). and,
Step S9 corresponding to the rotation range determining means 102, which will be described later, is executed, and it is determined whether the actual rotation speed Ne of the engine 10 is smaller than the suppressed rotation speed _Ne1 . Actual rotation speed Ne is suppressed rotation speed
If it is larger than Ne ₁ , step S10 is executed and the content of the count value TC ₁ is set to zero, and then the speed ratio control routine of step S6 described above is executed, but the actual rotational speed of the engine 10 is If Ne is smaller than the suppressed rotational speed Ne ₁ , steps S4 and subsequent steps are executed in the same way as in the previous embodiment. FIG. 12 is a control block diagram of this embodiment.

According to this embodiment, when the rotational speed of the engine decreases to the suppression rotational speed Ne ₁ in the deceleration state of the vehicle as shown by the solid line in _FIG . Since the change is suppressed, when the vehicle is re-accelerated following deceleration, the increase in the engine speed Ne is smaller than in the conventional case shown by the broken line in FIG. 13, and the speed ratio e of the continuously variable transmission 14 is smaller. Since the changes are reduced, high driveability and fuel economy are obtained.

Furthermore, according to this embodiment, the actual engine rotational speed during the section _t1 during vehicle deceleration is
Since the engine rotation speed Ne is maintained at the suppressed rotation speed Ne ₁ , which is set to an appropriate value slightly smaller than Ne, the rotation speed during such deceleration is lower than when the rotation speed change of the engine 10 is zero. This has the advantage of preventing the disadvantage that the engine rotational speed Ne is maintained higher than necessary in the section where changes in Ne are suppressed.

Note that if the suppressed rotational speed Ne ₁ is too large, drivability and fuel economy during re-acceleration are improved, but Ne becomes too large during deceleration, causing problems such as excessive engine braking and noise. Further, if Ne ₁ is too small, the drivability and fuel economy during re-acceleration will be impaired, so Ne ₁ is set at a point in equilibrium between the two, and may be a constant value. In this case, if the suppressed rotational speed Ne ₁ is kept constant, steps S7 and S8 become unnecessary.

Since the suppressed rotational speed Ne ₁ is determined to be large as the vehicle speed V increases according to the relationship shown in FIG. 11, optimum re-acceleration performance and fuel economy can be obtained regardless of the vehicle speed V. It goes without saying that even if the suppressed rotational speed Ne ₁ is set to a constant value regardless of the vehicle speed V, a certain effect of the present invention can be obtained.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be applied to other aspects.

For example, although the belt-type continuously variable transmission 14 is described in the above embodiment, other types of continuously variable transmissions may be used.

Further, in the above embodiment, the opening degree θ of the throttle valve 54 is used to detect the required load of the engine 10, but the operating amount of the accelerator pedal 52, the intake pipe negative pressure of the engine 10, etc. It is okay to do so. In short, any amount that represents the required load amount of the engine 10 may be used.

Further, the deceleration state determination means 78 described above determines the deceleration state of the vehicle based on the fact that the actual vehicle speed V is smaller than the vehicle speed Vo determined a certain time ago, but it is also possible to detect the deceleration state of another vehicle. The output signal of the accelerometer may also be used.

Furthermore, the predetermined constant time _t1 used in step S4 described above may be determined based on a predetermined relationship that is changed according to changes in the vehicle speed V. In this way, since the rotational speed change suppression time of the continuously variable transmission 14 is changed in accordance with changes in vehicle speed, there is an advantage that optimum acceleration performance and fuel economy can be obtained regardless of the vehicle speed.

Furthermore, in step S5 described above, the content of the target rotational speed Ne′ is the actual rotational speed of the engine 10.
Ne is changed to a value slightly smaller than the actual rotational speed Ne, for example, Ne − α (however, α is an extremely small value), or Ne′ + β (however, β is
It may be changed to a value slightly smaller than the difference between Ne' and Ne. In such a case, the speed ratio e of the continuously variable transmission 14 during the rotational speed change suppression control period can be slightly changed.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to claims of the present invention. Second
The figure is a configuration diagram of a continuously variable transmission for a vehicle to which an embodiment of the present invention is applied. FIG. 3 is a control block diagram in the embodiment of FIG. 2. FIG. 4 is a diagram showing the relationship between the throttle valve opening and the target rotational speed. FIG. 5 is a diagram showing output torque characteristics with respect to engine rotational speed using the throttle valve opening as a parameter. 6, 7, and 8 are flowcharts each illustrating the operation of the embodiment shown in FIG. 2. FIG. 9 is a time chart showing the operation of the embodiment shown in FIG. FIGS. 10, 12, and 13 show the sixth embodiment of the present invention.
FIG. 9 is a diagram corresponding to FIGS.
FIG. 11 is a diagram showing the relationship between vehicle speed and suppressed rotational speed. 10: Engine, 14: (Belt type) continuously variable transmission, 56: Throttle sensor (required load amount detection means), 60: Rotation sensor (rotation speed detection means), 7
6: Target rotational speed determining means, 78: Deceleration state determining means, 82: Counting means (timekeeping means), 84:
Time interval determining means (time measuring means), 86: Rotational speed change suppressing means, 90: Shift control controlling means.

Claims (1)

[Scope of Claims] 1. In a continuously variable transmission for a vehicle that continuously changes the speed of the engine and transmits it to the wheels, a rotation speed detection means for detecting the rotation speed of the engine, and requirements required of the engine. load amount detection means; target rotation speed determination means for sequentially determining a target rotation speed of the engine based on the required load amount from a predetermined relationship; and a speed ratio adjusting means for adjusting the speed ratio of the continuously variable transmission, the speed ratio control device comprising: a deceleration state determining means for determining a deceleration state of the vehicle; and a deceleration state determining means for determining a deceleration state of the vehicle; a timer for determining that time has elapsed; and a rotational speed change suppressor for suppressing a change in the rotational speed of the engine from when the vehicle starts decelerating until the timer determines that the predetermined time has elapsed. A speed ratio control device for a continuously variable transmission for a vehicle, comprising: means.