JP3365303B2 - Control device for continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a continuously variable transmission control device capable of continuously changing a gear ratio.
More particularly, the present invention relates to a control device for controlling a shift speed so as to suppress a longitudinal vibration of a vehicle which is expected to occur at the end of a shift. [0002] Vehicles equipped with a continuously variable transmission have recently been put to practical use. This type of continuously variable transmission is configured to continuously change the gear ratio by changing the groove width between the input side pulley and the output side pulley around which the belt is wound, that is, the belt winding radius. The power ratio is continuously changed by changing the radius of the contact position of the power roller with each disk by inclining the power roller inserted between the input side disk and the output side disk. Is configured. The gear ratio is determined based on, for example, an accelerator pedal depression angle (accelerator opening) indicating a driver's output request, an output request signal from a cruise control that maintains the vehicle speed at a constant vehicle speed, and a vehicle speed. Is controlled based on the traveling state of the vehicle. Therefore, when there is an acceleration request due to depression of an accelerator pedal or the like, the gear ratio is controlled to be increased. This is because, in a belt-type continuously variable transmission, the width of the belt on the input side pulley is increased to gradually reduce the winding radius of the belt, and at the same time, the width of the output side pulley is reduced to reduce the belt winding radius. Is performed by increasing. Further, the gear ratio finally set at that time is determined based on the target rotation speed of the prime mover, the vehicle speed, and the like which are determined based on the degree of the output increase request. In the case of such a so-called power-on downshift, inevitable torsion occurs in a power transmission system such as a propeller shaft, and the number of revolutions increases at a predetermined rate. At the end of the reached shift, the torsional torque or the inertia torque may cause a drive torque thrust (overshoot) and a longitudinal vibration (shake) of the vehicle. In order to prevent or suppress the longitudinal vibration of the vehicle at the end of the shift, it is effective to change the change in the driving torque associated with the shift immediately before the end of the shift. No. 8-177997. The device described in this publication is configured to temporarily reduce the speed ratio immediately before the end of the speed change for increasing the speed ratio. That is, in this device, the time when the speed ratio reaches the target speed ratio and the half cycle of the vehicle longitudinal vibration at the target speed ratio are predicted, and the correction start time of the speed ratio is determined based on the prediction result. At this point, the gear ratio is corrected to the higher vehicle speed side to change the tendency of the drive torque to increase. [0005] The longitudinal vibration of the vehicle, which occurs at the end of the low-speed shift by the continuously variable transmission, has a cycle corresponding to the speed ratio at that time. Therefore, even in the above-mentioned conventional apparatus, the gear ratio correction start point before the gear shift end point is predicted based on the target gear ratio. When such control is performed, the gear ratio is corrected to the high vehicle speed side before reaching the target gear ratio, so that the predicted half cycle of the longitudinal vibration does not match the half cycle of the actually generated longitudinal vibration. . As a result, the timing of starting the gear ratio correction becomes inappropriate, and there is a possibility that the longitudinal vibration cannot be effectively suppressed. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a control device capable of effectively preventing the longitudinal vibration of a vehicle by appropriately adjusting a timing of correcting a gear ratio during a gear shift. The purpose is to do so. SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a half-period of longitudinal vibration having a cycle corresponding to a target gear ratio expected to occur at the end of a gear shift. A control device for a continuously variable transmission that changes a shift speed before reaching the target speed ratio based on the target speed ratio; Means for calculating an intermediate speed ratio at a point in time before a half cycle, and means for determining a time point at which the shift speed is changed based on the target speed ratio and the intermediate speed ratio. . Therefore, in the device according to the present invention, when the longitudinal speed of the vehicle at the end of the gear shift is suppressed by changing the gear speed during the gear shift, not only the target gear ratio but also the target gear ratio is changed. The gear ratio is determined in consideration of the gear ratio at a time half a cycle before the longitudinal vibration at the target gear ratio before reaching the gear ratio. As a result, the gear ratio change start timing becomes more appropriate, and the longitudinal vibration of the vehicle at the end of the gear shift is effectively suppressed. Next, the present invention will be described with reference to specific examples. First, an example of a drive mechanism of a vehicle to which the present invention is applied will be described. In FIG. 4, an output shaft 2 of a prime mover 1 is connected to a transmission 3. Here, the prime mover 1
Includes various power sources that can be used for vehicles, such as internal combustion engines such as gasoline engines and diesel engines, electric motors such as motors, and devices that combine these internal combustion engines and electric motors. The prime mover 1 is configured to be electrically controllable, and is provided with an electronic control unit (ECU) 4 mainly composed of a microcomputer for the control. The control device 4 is configured to control at least the output of the prime mover 1, and receives an output shaft rotation speed Ne and an output request signal such as an accelerator opening Acc as data for the control. This output request signal is
The point is that it is a signal for increasing / decreasing the output of the prime mover 1. In the case of the prime mover 1 having an electronic throttle valve in addition to the operation amount signal Acc of the accelerator pedal (not shown) operated by the driver. And an output request signal from a cruise control system (not shown) for maintaining the vehicle speed at a set vehicle speed, and the like. The transmission 3 is for enabling the prime mover 1 to be kept rotating even when the vehicle is stopped. The transmission 3 transmits a torque by pressing a friction plate. Various types of clutches, such as a general clutch, a fluid coupling (fluid coupling), a fluid type torque converter, a torque converter having a built-in lock-up clutch, an electromagnetic clutch, a powder clutch, and the like, can be employed. The transmission 3 is connected to the input shaft 6 of the transmission 5. The transmission 5 is a mechanism for continuously changing the ratio of the number of revolutions of the input shaft 6 and the output shaft 7. More specifically, the transmission 5 has an appropriate type such as a belt type or a toroidal type. It is a step transmission. An electronic control unit (ECU) 8 for electrically controlling the gear ratio is provided. The electronic control unit 8 is connected to the electronic control unit 4 for the prime mover 1 so as to be able to perform data communication.
Data necessary for controlling the gear ratio has been input. Further, the output shaft 7 is provided with a forward / reverse switching mechanism 9.
It is connected to. As the forward / reverse switching mechanism 9, a mechanism configured to switch between forward and reverse by changing the meshing state of the gears, a mechanism mainly configured with a planetary gear mechanism, and the like can be used. In the case of a so-called power-on downshift in which the speed ratio set by the continuously variable transmission 5 is increased by an acceleration request (that is, a request to increase the output of the prime mover 1),
The longitudinal vibration (shear) of the vehicle may occur at the end of the shift due to the accumulated torsional torque and inertia torque. In order to suppress the longitudinal vibration, it is effective to change the shift speed immediately before the end of the shift, and the control device of the present invention executes the shift speed change control as described below. FIG. 1 is a flowchart for explaining an example of the control. First, a target speed ratio R based on an acceleration request is set.
1 is calculated (step 1). Specifically, it can be calculated from the following equation based on the target engine speed Ne1, the vehicle speed V, and the constant α: R1 = α · Ne1 / V (1) Here, the target engine speed Ne1
May be prepared in advance as a map value using, for example, the accelerator opening and the vehicle speed as parameters, and may be obtained from the map. Next, a period T1 of the vehicle longitudinal vibration at the target gear ratio R1 is obtained (step 2). As an example,
In the belt-type continuously variable transmission, the gear ratio and the period of the longitudinal vibration are substantially proportional as shown in FIG. 2. Therefore, in the case of a vehicle equipped with this type of transmission 5, the calculated target The longitudinal vibration period T1 can be obtained from the gear ratio R1 and FIG. It can also be obtained by calculation. As an example, first, the moment of inertia I1 of the power transmission system is shown.
And an inertia moment I2 based on the vehicle weight. I1 = ((R · Rd) ² ) · I + Rd ² · Iout (2) I2 = M · r ² (3) where R is a gear ratio set by the continuously variable transmission 5, R
d is the gear ratio of the final reduction gear (differential gear),
I is the moment of inertia on the input side of the transmission 5, Iout is the moment of inertia on the output side of the transmission 5, M is the vehicle weight, and r is the tire radius. Based on these, the angular velocity ω is calculated as follows: ω = ((I1 + I2) / (I1 · I2) × k) ^1/2 (4) Here, k is a torsional spring coefficient of the power transmission system. Then, based on the angular velocity, the period T0 of the longitudinal vibration is calculated by T0 = 2 · pi / ω (5). Where pi is the pi (π).
Therefore, by substituting the value of the target gear ratio R1 into R in the above equation, the period T1 of the longitudinal vibration at the target gear ratio R1 is obtained.
Is found. Next, a first tentative period (tentative execution period of the anti-shear control immediately before the end of the shift) ts1 for suppressing the vehicle longitudinal vibration at the end of the shift is obtained (step 3). this is,
Generally, half of the cycle T1 of the vehicle longitudinal vibration (half cycle: T
1/2). When the viscosity is considered, the viscosity damping coefficient η is determined by the viscosity damping c of the power transmission system.
Η = c / 2 · ((I1 + I2) / (I1 · I2 · k)) ^1/2 (6) Further, the vehicle longitudinal vibration suppression period ts
Is determined by: ts = pi / ((1−η ² ) ^1/2 · ω) (7) Since the vehicle longitudinal vibration suppression control is executed immediately before the end of the shift, the engine speed at the time before the suppression period ts from the end of the shift when the shift is performed at the shift speed at the beginning of the shift. Ne and speed ratio R2 are determined (steps 4 and 5). That is, the engine speed Ne2 at the start of the longitudinal vibration suppression control can be obtained from the following equation: Ne2 = Ne1-1 / 2 ・ ΔNe0 ・ ts1 (8) Here, ΔNe0 is the speed change speed (change ratio of the speed ratio) before the start of the longitudinal vibration suppression control. FIG. 3 shows the relationship between the engine speeds Ne1 and Ne2. The engine speed N
Based on e2 and the vehicle speed V, the gear ratio R2 is obtained by the following equation: R2 = α · Ne2 / V (9) This is substantially the same as the above-described equation (1). In this way, the target gear ratio R1 and the gear ratio R2 at the start of the longitudinal vibration suppression control are obtained, and based on these gear ratios R1 and R2, the actual longitudinal vibration suppression control period is obtained. Specifically, the period T2 of the longitudinal vibration based on the speed ratio R2 is determined in the same manner as the period T1 of the longitudinal vibration based on the target speed ratio R1 and the first provisional period ts1.
And a second provisional period ts2 (steps 7 and 8). Then, an average value ts (= (ts1 + ts2) / 2) of the above-mentioned first provisional period ts1 and second provisional period ts2 is obtained, and this is set as the execution period ts of the longitudinal vibration suppression control (step 8). It should be noted that the gear ratios R1 and R2 are converted to an average value R
3 is obtained, and the period of the longitudinal vibration and its half value are obtained based on the average value R3, the execution period ts can be obtained in the same manner. In the control device according to the present invention described above, when there is an acceleration request such as depression of an accelerator pedal,
As described above, the target gear ratio R1 and the longitudinal vibration suppression control period ts are calculated. At the beginning of the shift, the gear ratio is increased at a predetermined gear speed .DELTA.Ne0, and the gear speed is changed from a point in time when the target gear ratio R1 is reached to a point in time before the longitudinal vibration suppression control period ts. For example, the shift speed is reduced, or the speed is temporarily shifted to a higher vehicle speed side. The control for changing the shift speed in this manner is the longitudinal vibration suppression control, and the execution period and the execution timing thereof are determined in consideration of not only the target gear ratio R1 but also the gear ratio R2 at the start of the longitudinal vibration suppression control. Therefore, it is optimized for longitudinal vibration suppression control. As a result, by performing the control as described above, it is possible to effectively prevent or suppress the torque thrust (overshoot) at the end of the shift and the shock or longitudinal vibration resulting therefrom. Here, the relationship between each means in the present invention and the above specific example will be described. Step 3 corresponds to means for obtaining a half cycle of the longitudinal vibration corresponding to the target gear ratio, and step 5 corresponds to this. Step 8 corresponds to a means for obtaining the intermediate speed ratio in the present invention, and step 8 corresponds to means for obtaining a point in time at which the shift speed is changed. In the specific example described above, the calculation is performed based on the engine speed. However, the present invention can be applied to a vehicle that uses another prime mover such as a motor as a power source in addition to the engine. Therefore, the engine speed means the output speed of the power source.
Further, in the case of a belt-type continuously variable transmission, the speed of change of the groove width in the input-side and output-side pulleys is controlled by hydraulic pressure or the like. Alternatively, the tilting speed of the power roller may be controlled by hydraulic pressure or the like. As described above, according to the apparatus of the present invention, when the shift speed is changed in the middle of a shift as the longitudinal vibration suppression control, the shift speed change start time is set to the target shift speed. Not only the gear ratio but also the gear ratio at the time half a cycle before the longitudinal vibration at the target gear ratio from the time when the gear ratio reaches the target gear ratio is determined, so that the change start timing of the gear ratio is
It becomes more appropriate, and the longitudinal vibration of the vehicle at the end of shifting can be effectively suppressed or prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart for calculating a longitudinal vibration suppression control period by the apparatus of the present invention. FIG. 2 is a diagram showing a relationship between a speed ratio in a continuously variable transmission and a period of front-rear vibration that may be generated according to the speed ratio. FIG. 3 is a diagram showing a change in engine speed when longitudinal vibration suppression control is performed by the apparatus of the present invention. FIG. 4 is a block diagram schematically illustrating an example of a drive mechanism to which the present invention can be applied. [Description of Signs] 1 ... Motor, 5 ... Transmission.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48 B60K 41 / 00-41/28 F02D 29/00-29/06 F02D 41/00-41/40

Claims (1)

(57) [Claim 1] A shift speed is changed before reaching the target gear ratio based on a half cycle of longitudinal vibration of a cycle corresponding to a target gear ratio expected to be generated at the end of gear shifting. A control device for a continuously variable transmission, wherein: a means for obtaining a half cycle of the longitudinal vibration according to the target gear ratio; and a means for obtaining an intermediate gear ratio at a half cycle before the target gear ratio is reached, Means for determining a point in time at which the shift speed is changed based on the target speed ratio and the intermediate speed ratio.