JP2002310276A - Control device for continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of slip of a drive belt when rotation speed of a primary pulley is quickly reduced due to an ultra-low car speed state caused by quick speed reduction. SOLUTION: A continuously variable transmission comprises the primary pulley of a fixed pulley groove width, and a secondary pulley of a changeable pulley groove width, with a drive belt stretched between that and the primary pulley. By adjusting primary pressure to be supplied to the primary pulley, and secondary pressure to be supplied to the secondary pulley, a ratio of a winding diameter of the drive belt is changed. When the rotation speed of the primary pulley is less than a specified value, with the car speed less than a specified value, and as speed reduction ratio of the vehicle is larger than a specified value, the secondary pressure is set at a high pressure to set the speed changing speed where the drive belt generates slip to the primary pulley high. When quick speed reduction is conducted to make the ultra-low car speed state, with quick reduction of the rotation speed of the primary pulley, generation of gross slip at the drive belt can thus be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a belt-type continuously variable transmission, and more particularly to a control device for preventing occurrence of slip of a drive belt at the time of sudden deceleration.

[0002]

2. Description of the Related Art A belt-type continuously variable transmission (CVT) applied to a power transmission device of an automobile includes a primary pulley having a variable pulley groove width provided on a driving-side primary shaft and a primary pulley. And a secondary pulley with a variable pulley groove width provided on a driven secondary shaft on a driven belt. If the ratio of the winding diameter of the drive belt to these pulleys, that is, the pulley ratio, is changed by hydraulic pressure, the rotational speed of the secondary shaft can be changed steplessly.

[0003] The shift control of the belt type CVT is performed by adjusting the hydraulic pressure supplied to the drive oil chambers of hydraulic cylinders provided on each of the primary pulley and the secondary pulley. Is generated by an oil pump driven by an engine or an electric motor. The secondary pressure applied to the driving oil chamber on the secondary pulley side is adjusted by the secondary pressure adjusting valve, and the primary pressure applied to the driving oil chamber on the primary pulley side is adjusted by the primary pressure adjusting valve using the secondary pressure as the original pressure. .

[0004]

SUMMARY OF THE INVENTION Such a belt type C
In the case of VT, the tightening force of the primary pulley on the drive belt may be weakened during deceleration to increase the groove width of the primary pulley, and the drive belt may slip with respect to the primary pulley. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2000-97321, a target shift speed is set based on the throttle opening during deceleration, and the primary pressure and the secondary pressure are corrected from the target shift speed.

As described above, even when the primary pressure and the secondary pressure are uniformly corrected based on the throttle opening for the entire rotation range of the primary pulley, the driver may not be able to adjust the foot pressure in a low-speed running state. When the brake is depressed, the drive belt slips largely in the radial direction with respect to the primary pulley, and gross slip may occur. The reason for this is that the area in which no gross slip occurs between the drive belt and the pulley during shifting, that is, the shift speed at which shifting can be performed without gross slip is proportional to the rotation speed of the primary pulley. This is because the speed becomes slow. As a result, the foot brake is strongly depressed and becomes extremely low speed, and the rotation speed of the primary pulley drops rapidly even during the downshift. Gross slip occurs on the pulley. Thus, when the vehicle stops, the inertial force of the primary pulley propagates to the vehicle, causing a shock. This phenomenon was remarkable when the gear ratio was on the low side.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the drive belt from slipping even when the speed of the primary pulley suddenly decreases due to a sudden deceleration resulting in an extremely low vehicle speed state.

[0007]

SUMMARY OF THE INVENTION A control device for a continuously variable transmission according to the present invention comprises a primary pulley having a variable pulley groove width, and a secondary pulley having a variable pulley groove width over which a drive belt extends between the primary pulley. The primary pressure is supplied to the primary pulley, the secondary pressure is supplied to the secondary pulley, and the ratio of the winding diameter of the drive belt to the primary pulley and the secondary pulley is changed to perform continuously variable transmission. A control device for a continuously variable transmission, wherein when the rotation speed of the primary pulley is equal to or lower than a predetermined value, the vehicle speed is equal to or lower than a predetermined value, and the vehicle is rapidly decelerated, a rapid deceleration for increasing a secondary pressure is performed. Mode, the rotation speed of the primary pulley is equal to or higher than a predetermined value, the vehicle speed is equal to or higher than a predetermined value, or the vehicle is not suddenly decelerated. To come, and having a normal deceleration mode to set the secondary pressure to a pressure lower than the rapid deceleration mode.

A control device for a continuously variable transmission according to the present invention includes a primary pulley having a variable pulley groove width, and a secondary pulley having a variable pulley groove width over which a driving belt is stretched between the primary pulleys. Control of a continuously variable transmission that supplies a primary pressure to a primary pulley, supplies a secondary pressure to the secondary pulley, and changes a ratio of a winding diameter of the drive belt to the primary pulley and the secondary pulley to perform a continuously variable transmission. A device,
A pulley rotation speed detecting unit for detecting a rotation speed of the primary pulley, a vehicle speed detection unit for detecting a speed of the vehicle, a deceleration detection unit for detecting a deceleration state of the vehicle, and a rotation speed of the primary pulley being equal to or less than a predetermined value. And control means for setting the secondary pressure to a high pressure when the vehicle speed is equal to or lower than a predetermined value and the deceleration of the vehicle is higher than a predetermined value.

According to the present invention, when the rotation speed of the primary pulley decreases due to the extremely low vehicle speed due to rapid deceleration, the secondary pressure is set high, so that the drive belt slips with respect to the primary pulley. The entering shift speed increases. As a result, there is no gross slip of the drive belt, and it is possible to prevent the vehicle from generating a shock when the vehicle stops.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a drive system of a belt type continuously variable transmission. In this continuously variable transmission, rotation of a crankshaft 2 driven by an engine 1 is transmitted via a torque converter 3 and a forward / reverse switching device 4. It has a driven primary shaft 5 to be transmitted and a driven secondary shaft 6 parallel to it.

The primary shaft 5 is provided with a primary pulley 7. The primary pulley 7 is fixed to the primary shaft 5 and is opposed to the primary pulley 7 by a ball spline or the like. And a movable pulley 7b slidably mounted on the pulley, and a gap between the cone surfaces of the pulley, that is, a pulley groove width is variable.
The secondary shaft 6 is provided with a secondary pulley 8. The secondary pulley 8 is a fixed pulley 8 a integrated with the secondary shaft 6, and is opposed to the secondary pulley 8. And a movable pulley 8b that is slidably mounted on the pulley, and the width of the pulley groove is variable.

Primary pulley 7 and secondary pulley 8
A drive belt 9 is stretched between the pulleys 7 and 8, and by changing the groove width of both pulleys 7 and 8 to change the ratio of the winding diameter of the drive belt 9 to each pulley, the primary shaft 5 is rotated. The rotation is transmitted to the secondary shaft 6 at a continuously variable speed. If the winding diameter of the drive belt 9 around the primary pulley 7 is Rp and the winding diameter around the secondary pulley 8 is Rs, the gear ratio, i.e., the pulley ratio i is i = Rs / Rp.

The rotation of the secondary shaft 6 is transmitted to the drive wheels 12a and 12b via a gear train having a reduction gear and a differential device 11. In the case of front wheel drive, the drive wheels 12a and 12b are connected to the front wheels. Becomes

To change the groove width of the primary pulley 7, a plunger 13 is fixed to the primary shaft 5,
A primary cylinder 14 slidably in contact with the outer peripheral surface of the plunger 13 is fixed to the movable pulley 7b, and a driving oil chamber 15 is formed by the plunger 13 and the primary cylinder 14. On the other hand, the secondary shaft 6
Is fixed to the movable pulley 8b, and a driving oil chamber 18 is formed by the plunger 16 and the secondary cylinder 17. I have. Therefore, when hydraulic oil is supplied to the drive oil chamber 15 in the primary cylinder 14 to increase its volume,
The movable pulley 7b and the cylinder 14 together with the fixed pulley 7a
Side, the pulley groove width is reduced, and when the volume is reduced, the pulley groove width is increased. Also, the secondary cylinder 1
When hydraulic oil is supplied to the drive oil chamber 18 in the tank 7 to increase its volume, the movable pulley 8b moves to the fixed pulley 8a side together with the secondary cylinder 17 to reduce the pulley groove width. Becomes wider. Each groove width is set by adjusting the primary pressure Pp introduced into the primary driving oil chamber 15 and the secondary pressure Ps introduced into the secondary driving oil chamber 18.

The operating oil in the oil pan 20 is supplied to each of the driving oil chambers 15 and 18 by an oil pump 21 driven by an engine or an electric motor. The line pressure passage, that is, the secondary pressure passage 22 connected to the outlet is connected to the drive oil chamber 18 and the secondary pressure adjustment valve 2.
3 is connected to the secondary pressure port. The secondary pressure Ps supplied to the drive oil chamber 18 by the secondary pressure adjustment valve 23 is adjusted to a pressure corresponding to the transmission capacity required for the drive belt 9. That is, when the engine output is large such as when climbing a hill or suddenly accelerating, the secondary pressure P
s is raised to prevent the drive belt 9 from slipping, and lowered when the engine output is low,
1 and the transmission efficiency is improved.

The secondary pressure passage 22 is connected to a secondary pressure port of a primary pressure regulating valve 24 via a communication oil passage 25, and the primary pressure port of the primary pressure regulating valve 24 is connected to a primary side via a primary pressure passage 26. Is connected to the drive oil chamber 15. The primary pressure Pp is adjusted by the primary pressure adjusting valve 24 to a value corresponding to the target gear ratio, the vehicle speed, and the like, and the gear ratio is controlled by changing the groove width of the primary pulley 7. Secondary pressure regulating valve 2
3 and the primary pressure adjusting valve 24 are proportional solenoid valves, respectively, and the secondary pressure Ps and the primary pressure Pp are adjusted by controlling the current value supplied from the control device 30 to each of the solenoid coils 23a and 24a.

The control device 30 includes a pulley rotation speed sensor 31 for detecting the rotation speed of the primary pulley 7, a vehicle speed sensor 32 for detecting the traveling speed of the vehicle, and a range detection sensor 33 for detecting a traveling range selected by the driver. , And a detection signal is sent from an oil temperature sensor 34 for detecting the temperature of the hydraulic oil. The control device 30 includes a central processing unit that calculates a current value for each of the solenoid coils 23a and 24a based on a signal from each sensor, and a memory that stores an arithmetic expression and map data.

FIG. 2 is a shift characteristic diagram of the continuously variable transmission shown in FIG. 1. For example, when the throttle is fully opened and accelerated, the rotation of the primary pulley 7 is kept at the lowest speed ratio A After that, while the rotation slightly increases, the vehicle speed increases to the overtop side and reaches the highest speed point B. When the accelerator pedal is released from this state or when normal braking is performed, the gear ratio becomes a low side at point E via C and D, and the vehicle stops at a low gear ratio due to braking. In actual traveling, the speed ratio changes freely within a range indicated by hatching between the speed ratio on the low side and the speed ratio on the overdrive side.

When the foot brake is strongly depressed and suddenly decelerated before the speed ratio on the low side is reached during deceleration, the rotational speed of the primary pulley 7 changes as indicated by the symbol F in FIG. At this time, it is necessary to control the primary pulley 7 to increase the groove width at a large speed change speed.

The speed di / dt of the belt-type continuously variable transmission is represented by the following equation.

Di / dt = K (I) · Np · (Ppa−Ppb) where K (I) is a coefficient set by the speed ratio i, Np is the rotation speed of the primary pulley, and Ppa is This is the actual primary pressure, and Ppb is the primary pressure necessary to maintain the gear ratio at that time. As shown in this equation, the shift speed depends on the primary rotation speed Np, and the lower the primary rotation speed, the lower the shift speed.

FIG. 3 shows that each of the primary pulleys 7 has 50
FIG. 7 is a characteristic diagram showing a relationship between the shift speed of the pulley 7 and the primary pressure at 0 rpm and 3000 rpm, and the secondary pressure Ps is 0.6 MPa. 3A shows a pulley ratio i of 0.7, FIG. 3B shows a pulley ratio i of 1.0,
FIG. 3C shows a case where the pulley ratio is 1.3. When the shift speed is 0 in these characteristic diagrams, the vehicle is traveling with the gear ratio fixed at each speed ratio, and Ppa and Ppb are equal. In each speed ratio, the higher the primary rotational speed Np, the higher the speed. The change in the primary pressure Pp and the change in the speed have a substantially linear correspondence. Further, as shown in the figure, when the primary pressure Pp becomes a predetermined value, that is, a pressure lower than the pressure at the inflection point shown by the broken line in FIG. 3, the shift speed suddenly increases. As described above, the range in which the primary pressure is lower than the inflection point and the shift speed sharply increases indicates a state in which the drive belt 9 is gross slipping with respect to the primary pulley 7. In addition, 500rpm and 30
The primary rotation speed between 00 rpm is also indicated by the same characteristics between the two characteristic diagrams.

Therefore, when the primary rotation speed is high, even if the foot brake is depressed, the groove width of the primary pulley can be increased at a shift speed following the deceleration due to braking. That is, when the rotational speed is high, the gear can be shifted in a region where slip does not occur. On the other hand, when the primary rotation speed is low, the shift speed is low, so that when the foot brake is depressed, the shift speed cannot follow the deceleration, and the drive belt 9 On the other hand, gross slip may occur. That is, when the number of rotations is small, there may be a case where the shift must be performed in a region where the slip occurs.

FIG. 4 shows that the secondary pressure Ps is 0.6,
FIG. 4 is a characteristic diagram showing the relationship between the primary pressure Pp and the shift speed when 0.9 and 1.4 (Mpa) are set.
4A shows a case where the pulley rotation speed is 500 rpm, FIG. 4B shows a case where the pulley rotation speed is 1000 rpm, and FIG. 4C shows a case where the pulley rotation speed is 1500 rpm. FIG. 4 shows that at a pressure lower than the pressure at the inflection point indicated by the broken line, the drive belt 9 generates slip. As described above, no matter what the primary rotational speed is, increasing the secondary pressure can increase the shift speed.
The speed at which slippage occurs can be increased.

As can be seen from FIGS. 3 and 4, between the primary rotational speed and the shift speed, when the primary rotational speed is high, slippage does not occur even if the primary pulley 7 is shifted at a high shift speed. On the other hand, when the primary rotation speed is low, the primary pulley slips even at a low speed. On the other hand, when the secondary pressure is increased, the speed at which slippage occurs can be increased even when the primary rotational speed is low. This relationship is schematically shown in FIG. 5, and it can be seen that when the secondary pressure is increased, the slip region where slippage occurs decreases.

Therefore, in this continuously variable transmission, in addition to the normal deceleration mode when the vehicle is running at a high speed above a predetermined value, the vehicle is in a low speed running state below a predetermined value, and When the rotational speed of the motor 7 is equal to or lower than a predetermined value, the vehicle has a rapid deceleration mode in which the speed at which slippage occurs is increased to rapidly reduce speed in a region where slippage does not occur.

FIG. 6 is a characteristic diagram showing the relationship between the rotational speed Np of the primary pulley 7 and the secondary pressure Ps in the normal deceleration mode and the rapid deceleration mode, and the rapid deceleration mode is selected according to the driving situation. Then, the secondary pressure is set to a higher pressure than in the normal deceleration mode. The arithmetic expression and map data corresponding to each shift mode are stored in the control device 3
0, and one of the deceleration modes is set according to the driving situation.

FIG. 7 is a flowchart showing a control procedure of the continuously variable transmission having the normal deceleration mode and the rapid deceleration mode. In step S1, the rotation speed Np of the primary pulley 7 is determined.
Is determined to be equal to or less than a predetermined value, and in step S2, it is determined whether the traveling speed V of the vehicle is equal to or less than a predetermined value. The predetermined value of the primary rotation speed Np can be, for example, 300 rpm, and the predetermined value of the traveling speed V can be, for example, 20 km / h, but each value can be set to any value. it can.

In step S3, it is detected which range has been selected by the driver operating the select lever, and it is determined whether or not a forward travel range other than the parking range, the neutral range, and the reverse range has been selected. . In step S4, it is determined whether the deceleration is larger than a predetermined value. The predetermined value is set to a value corresponding to sudden deceleration when the brake is depressed more strongly than when a normal brake operation is performed. The deceleration may be determined based on the amount of depression of the brake, or may be determined from the relationship between the vehicle speed and the rotation speed of the secondary pulley, and the acceleration acting on the vehicle and the acceleration for detecting the deceleration may be determined. You may make it detect by a sensor. Further, step S
At 5, it is determined whether the hydraulic oil guided from the oil pan 20 by the oil pump 21 is within a predetermined temperature range.

If YES is determined in steps S1 to S5, the rapid deceleration mode is set in step S6, and if NO is determined in any of the steps,
The normal deceleration mode is set in S7. In other words, the foot brake is operated and the vehicle is suddenly decelerated to an extremely low vehicle speed state,
When the rotation speed of the primary pulley drops rapidly, the mode is switched to the rapid deceleration mode. As a result, even when the secondary pressure is increased and the rotational speed of the primary pulley 7 is low, the speed at which slippage occurs is increased. On the other hand, while transmitting the torque without gross slip, until the low gear ratio is reached
The groove width of the primary pulley can be increased. Therefore, the driving belt 9 does not slip until the vehicle stops due to braking, and it is possible to avoid the occurrence of a shock in the vehicle when the vehicle stops.

The present invention is not limited to the above embodiment, but can be variously modified without departing from the gist thereof. For example, the drive system of the belt-type continuously variable transmission is not limited to the case shown in FIG. 1, and the present invention can be applied to various types such as a type having no torque converter and a four-wheel drive type.

[0032]

According to the present invention, when the foot brake is strongly depressed and suddenly decelerates to a very low vehicle speed state, and the rotational speed of the primary pulley suddenly decreases, the secondary pressure is reduced by the rapid deceleration mode. When the vehicle is raised, the speed at which the drive belt slips with respect to the primary pulley is increased, so that gross slip of the drive belt can be prevented, and a shock when the vehicle stops can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a drive system of a belt-type continuously variable transmission.

FIG. 2 is a shift characteristic diagram of the continuously variable transmission shown in FIG.

FIGS. 3A to 3C are characteristic diagrams illustrating a relationship between a shift speed of a primary pulley and a primary pressure.

FIGS. 4A to 4C are characteristic diagrams illustrating the relationship between a primary pressure and a shift speed.

FIG. 5 is a characteristic diagram showing a primary rotation speed at which slippage between a drive belt and a primary pulley occurs by changing a secondary pressure.

FIG. 6 is a characteristic diagram showing a relationship between a rotation speed of a primary pulley and a secondary pressure in a normal deceleration mode and a rapid deceleration mode.

FIG. 7 is a flowchart showing a control procedure of a continuously variable transmission having a normal deceleration mode and a rapid deceleration mode.

[Explanation of symbols]

 5 Primary Shaft 6 Secondary Shaft 7 Primary Pulley 8 Secondary Pulley 9 Drive Belt 15 Primary Drive Oil Chamber 18 Secondary Drive Oil Chamber 30 Control Device 31 Pulley Rotation Speed Sensor 32 Vehicle Speed Sensor 34 Oil Temperature Sensor

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[Procedure amendment]

[Submission date] April 24, 2001 (2001.4.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

FIG. 6 is a characteristic diagram showing the relationship between the pulley ratio i (primary rotation speed / secondary rotation speed) and the secondary pressure Ps in the normal deceleration mode and the rapid deceleration mode. Is selected,
The secondary pressure is set to a higher pressure than in the normal deceleration mode. Arithmetic expressions and map data corresponding to the respective shift modes are stored in a memory provided in the control device 30, and any one of the deceleration modes is set in accordance with a traveling situation.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6 is a characteristic diagram showing a relationship between a pulley ratio and a secondary pressure in a normal deceleration mode and a rapid deceleration mode.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F16H 63:06 F16H 63:06 (72) Inventor Jun Nakayama 1-7-2 Nishishinjuku, Shinjuku-ku, Tokyo In-house (72) Inventor Hironaga Ito 1-7-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Fuji Heavy Industries Ltd.F-term (reference) 3J552 MA07 MA12 MA26 NA01 NB01 PA02 PA12 RA27 RB19 RB20 SA36 TA06 TB03 VA32W VA37Z VA47Z VA62Z VA66Z VA74W VA74Y VB01W VB04W VC03Z VD11Z VD13Z

Claims (2)

[Claims] A primary pulley having a variable pulley groove width;
A secondary pulley having a variable pulley groove width over which a drive belt is stretched between the primary pulley and the primary pulley; supplying a primary pressure to the primary pulley; supplying a secondary pressure to the secondary pulley; A control device for a continuously variable transmission that performs a continuously variable transmission by changing a ratio of a winding diameter of the drive belt to a secondary pulley, wherein a rotation speed of the primary pulley is equal to or less than a predetermined value, and the vehicle speed is equal to or less than a predetermined value. And, when the vehicle is rapidly decelerated, a rapid deceleration mode to increase the secondary pressure, and whether the rotation speed of the primary pulley is a predetermined value or more,
And a normal deceleration mode for setting a secondary pressure to a pressure lower than the rapid deceleration mode when the vehicle speed is equal to or higher than a predetermined value or when the vehicle is not rapidly decelerated. apparatus. 2. A primary pulley having a variable pulley groove width,
A secondary pulley having a variable pulley groove width over which a drive belt is stretched between the primary pulley and the primary pulley; supplying a primary pressure to the primary pulley; supplying a secondary pressure to the secondary pulley; A control device for a continuously variable transmission that performs a continuously variable transmission by changing a ratio of a winding diameter of the drive belt to a secondary pulley, comprising: a pulley rotation speed detection unit configured to detect a rotation speed of the primary pulley; Vehicle speed detecting means for detecting the deceleration state of the vehicle, the rotation speed of the primary pulley is less than a predetermined value, the vehicle speed is less than a predetermined value, and the deceleration of the vehicle is a predetermined value Control means for setting the secondary pressure to a high pressure when the pressure is larger than the control pressure. Place.