JP2001221307A - Continuously variable transmission for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuously variable transmission for an automobile capable of performing required shift operations as soon as possible by preventing abnormal shift caused by clip and/or looseness of a power transmission belt beforehand. SOLUTION: A shift limiting value suitable for a acting speed (a shift speed) of a shift actuator 7 is selected among four systems of control values in correspondence to combinations of on/off conditions of an engine power and upshift/ downshift operations. Thus, a slip between a power transmission belt 6 and a primary pulley 5 caused by excessively high working speed of a shift actuator 7 is prevented and a high speed shift operation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuously variable transmission for an automobile.

[0002]

2. Description of the Related Art A continuously variable transmission for automobiles comprising a primary pulley, a secondary pulley, a power transmission belt and a speed change actuator, so-called CVT.
(Continuously Variable Transmission) is already known.

In this type of continuously variable transmission for automobiles, a primary pulley and a secondary pulley are configured by combining two discs formed in a thin conical shape so that the apex angles thereof are opposed to each other so as to be opposed to each other. The width of the primary pulley and the secondary pulley, that is, the width of the V groove around which the power transmission belt is wound was changed by moving the two disks constituting each pulley toward and away from each other. The gear ratio between the primary pulley and the secondary pulley is adjusted by regulating the winding radius of the power transmission belt.

That is, when the two disks are brought closer to each other to reduce the width of the pulley, the width of the groove around which the power transmission belt is wound is reduced, and the wedge effect of the V-groove formed on the opposing surface of each disk is used. Conversely, if the power transmission belt moves radially outward of the pulley and the two disks are separated from each other to increase the width of the pulley, the groove width around which the power transmission belt is wound increases. Thus, the power transmission belt moves radially inward of the pulley along the V-groove formed on the opposing surface of each disk.

Of course, it is possible to change the gear ratio between the primary pulley and the secondary pulley only by adjusting the width of either the primary pulley or the secondary pulley, but in that case, the width of the pulley is increased. A tension pulley or the like is required to eliminate the slack of the power transmission belt that may occur, and the pulley that can adjust the winding radius of the power transmission belt is limited to only one of them. Also becomes narrower.

Therefore, in practice, it is common to change the width of the primary pulley and the width of the secondary pulley together to adjust the speed ratio. For example, to increase the speed ratio, the width of the primary pulley is increased. In order to reduce the width of the secondary pulley and reduce the gear ratio, a cooperative operation such as reducing the width of the primary pulley and increasing the width of the secondary pulley is performed.

As means for performing such a cooperative operation, for example, as disclosed in Japanese Patent Application Laid-Open No. H8-178000, an independent hydraulic cylinder is provided for each of a primary pulley and a secondary pulley, and these hydraulic cylinders are provided. In general, a configuration is adopted in which the width of one pulley is increased and the width of the other pulley is reduced by simultaneously operating the cylinders.

Further, in order to avoid a complicated structure in which two sets of hydraulic cylinders are provided in this manner, only the winding radius of the power transmission belt in the primary pulley is controlled by the speed change actuator, and is driven by this. Japanese Patent Application Laid-Open No. H10-54429 proposes a continuously variable transmission for a vehicle in which the winding radius of a power transmission belt on the side of a secondary pulley is automatically adjusted by a torque cam.

This torque cam urges the secondary pulley in a direction of decreasing its width by a force substantially proportional to the driving torque transmitted from the power transmission belt to the secondary pulley, thereby winding the power transmission belt on the primary pulley side. A function is provided for adjusting the winding radius of the power transmission belt on the secondary pulley side in accordance with the change in the radius.

In other words, when the width of the primary pulley is increased by operating the speed change actuator and the winding radius of the power transmission belt on the primary pulley side is reduced, the secondary pulley side is reduced by an amount corresponding to the margin of the power transmission belt generated thereby. Is increased, the width of the secondary pulley is automatically reduced by the biasing force of the torque cam described above, and the power transmission on the secondary pulley side to the position of the winding radius allowed by this margin. The belt is pushed radially outward. Further, when the width of the primary pulley is reduced by operating the speed change actuator and the winding radius of the power transmission belt on the primary pulley side increases, the winding radius of the power transmission belt on the secondary pulley side is reduced accordingly. Then, the power transmission belt moves radially inward of the secondary pulley while forcibly expanding the width of the secondary pulley against the urging force of the torque cam.

The reduction ratio between the primary pulley and the secondary pulley is normally calculated automatically by a control unit of the continuously variable transmission for an automobile based on information such as a vehicle speed and a throttle opening. The above-described two sets of hydraulic cylinders or shift actuators are drive-controlled to adjust the speed reduction ratio between the primary pulley and the secondary pulley. In consideration of the necessity of downshifting at the time, the control unit is also provided with a function of a manual shift mode for a driver to select a gear ratio by himself / herself.

When changing the gear ratio by using the function of the manual gear shift mode, the point that the reduction ratio is adjusted by controlling the drive of two sets of hydraulic cylinders or gear shift actuators using the control unit described above is also considered. This is the same as the case of the automatic transmission mode described above.

In this type of continuously variable transmission for automobiles, the operating speed of the hydraulic cylinder or the shifting actuator, that is, the upper limit of the pulley width adjustment speed, is fixed to perform the shifting operation smoothly and reliably. In particular, when traveling in the automatic shift mode, the limit value is set to a relatively low value so that the driver can avoid unintended shocks and can run smoothly. Is set to a value.

On the other hand, when the vehicle is driven using the manual shift mode, a shift operation related to engine braking, rapid acceleration, or the like may be required. Therefore, it is necessary to make the response of the continuously variable transmission for an automobile as fast as possible. In addition, there is a demand to set the limit value of the operating speed of the hydraulic cylinder or the speed change actuator to a relatively large value.

[0015]

SUMMARY OF THE INVENTION The above-mentioned Japanese Unexamined Patent Publication No.
In a structure in which two hydraulic cylinders are drive-controlled to simultaneously adjust the widths of a primary pulley and a secondary pulley, as in the continuously variable transmission for automobiles disclosed in Japanese Patent No. 178000, the pulley width can be adjusted at a relatively high speed. Although it is unlikely that a problem will occur even if executed,
In the structure where the width of the secondary pulley is driven and changed using a torque cam, such as the continuously variable transmission for an automobile disclosed in Japanese Patent Application Publication No. It is highly possible that a problem such as an abnormal gear shift will occur if the gearshift operation is performed while the vehicle is idling or a gearshift operation for downshifting is performed.

As described above, in the configuration using the torque cam, the friction between the slope of the V-groove of the secondary pulley and both sides of the power transmission belt is generated by the force using the driving torque transmitted from the power transmission belt to the secondary pulley. This is because the connection is configured to be maintained.

As a result, when the gearshift operation is performed with the engine idling, the driving torque transmitted from the power transmission belt to the secondary pulley decreases, and the force with which the secondary pulley sandwiches the power transmission belt also decreases. As a result, slippage is likely to occur between the secondary pulley and the power transmission belt, causing a problem that the shift operation is sluggish.

Further, when the winding radius of the power transmission belt on the primary pulley side is reduced by quickly separating the primary pulley for the shift operation of the downshift, instantaneous slack occurs in the power transmission belt, so that the primary pulley is loosened. And the power transmission belt slips, and at the same time, the driving torque transmitted from the power transmission belt to the secondary pulley is significantly reduced. As a result, the force with which the secondary pulley sandwiches the power transmission belt is further reduced, causing slippage. The time required for moving the power transmission belt to the specified position radially outward of the secondary pulley, that is, the time required for shifting, becomes extremely long.

During this time, the driving force of the engine is not transmitted to the driving wheels, so that a feeling of idle running is generated as if the vehicle is traveling by inertia. Further, there is also a possibility that a shock may occur when the friction between the secondary pulley and the power transmission belt is recovered after the shift operation is completed.

The simplest way to solve such a problem is to set a lower limit value to be used and to lower the operating speed of the shifting actuator itself. Even during an upshift gearshift operation, the required gearshift time is unnecessarily prolonged, which hinders the intended purpose of a quick gearshift.

It is also conceivable to simultaneously drive the two hydraulic cylinders to adjust the widths of the primary pulley and the secondary pulley without depending on the function of the torque cam. As a result, the structure becomes complicated and the manufacturing cost increases.

[0023]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, prevent the occurrence of a shift abnormality caused by slipping or loosening of a power transmission belt, and enable a required shift operation. It is an object of the present invention to provide a continuously variable transmission for a vehicle that can be implemented quickly and with a simple configuration.

[0024]

SUMMARY OF THE INVENTION The present invention provides a primary pulley disposed at a position close to an engine on a power transmission path between an engine and a driving wheel, and a power transmission path between the engine and the driving wheel. Changing the width of the primary pulley according to a commanded gear ratio, and a secondary pulley provided at a position closer to the driving wheel, a power transmission belt wound between the primary pulley and the secondary pulley. And a speed change actuator that adjusts the winding radius of the power transmission belt on the primary pulley, and urges the secondary pulley in a direction of decreasing the width with a force substantially proportional to the driving torque transmitted from the power transmission belt to the secondary pulley. By following the change in the winding radius of the power transmission belt at the primary pulley, the secondary A continuously variable transmission for a motor vehicle having a torque cam for changing a winding radius of the power transmission belt in the pulleys, in order to achieve the object, in particular, to restrict the upper limit of the operating speed of the shift actuator magnitude 2
Storage means for storing the shift limit value of the system, engine power determining means for determining whether a load equal to or greater than the set value is acting on the engine, and a load greater than the set value being applied to the engine by the engine power determining means. If it is determined that the load is acting, the shift limit value of the system having the larger value is selected, while if it is determined by the engine power determining means that a load smaller than the set value is acting on the engine, An engine power-responsive shift limit value selecting unit that selects a shift limit value of a system with a small value, and an operating speed limit unit that regulates an upper limit of the operating speed of the shift actuator based on the selected shift limit value. Is provided.

According to this configuration, the power transmission belt positively transmits the driving torque to the secondary pulley, and the frictional contact between the secondary pulley and the power transmission belt is secured, that is, the power transmission belt and The shift actuator is driven by applying the shift limit value of the larger system only when the engine is running, in which slippage between the secondary pulley and the secondary pulley does not easily occur. As a result, even if the speed change actuator is quickly driven, no slippage occurs between the power transmission belt and the secondary pulley, and upshifting or downshifting is achieved in a short time. On the other hand, the power transmission belt does not actively transmit the driving torque to the secondary pulley and the frictional contact between the secondary pulley and the power transmission belt is weakened, that is, between the power transmission belt and the secondary pulley. In the idling state where slippage is likely to occur, the shift actuator is driven by applying the shift limit value of the system with a small value. As a result, the speed change actuator is driven more slowly than when the engine is running, and even if the frictional contact between the secondary pulley and the power transmission belt is weak, the power of the primary pulley is low. The change in the winding radius of the power transmission belt in the secondary pulley can reliably follow the change in the winding radius of the transmission belt. Therefore, no slippage occurs between the power transmission belt and the secondary pulley, and a smooth upshift or downshift is achieved. As a result, the delay in the shifting operation due to the slip between the power transmission belt and the secondary pulley is eliminated, and as a result, the driving speed of the shifting actuator is unnecessarily increased to generate unnecessary slipping. Gear shifting operation becomes possible.

Further, in order to eliminate a shift abnormality occurring at the time of a downshift, it is necessary to determine whether an upshift is being performed or not by performing the downshift instead of the engine power determining means and the engine power corresponding shift limit value selecting means. Shift operation determining means for determining whether the shift operation has been performed, and when the shift operation determining means determines that an upshift is being performed, a shift limiting value of a system having a large value is selected. If it is determined by the means that downshifting is being performed, a shift operation corresponding shift limit value selecting means for selecting a shift limit value of the system having the smaller value is provided.

According to this configuration, the winding radius of the power transmission belt on the primary pulley is increased and the power transmission belt is pressed against the secondary pulley, that is,
Only in the case of an upshift in which slippage between the power transmission belt and the secondary pulley is unlikely to occur, the shift actuator is driven by applying the shift limit value of the system having a large value. As a result, even if the speed change actuator is quickly driven, no slippage occurs between the power transmission belt and the secondary pulley, and the upshift is achieved in a short time. On the other hand, in a state where the winding radius of the power transmission belt in the primary pulley is reduced and the power transmission belt is likely to be slackened, that is, in the case of a downshift in which slippage easily occurs between the power transmission belt and the secondary pulley, The shift actuator is driven by applying the shift limit value of the system with a small value. As a result, the speed change actuator is driven more slowly than in the case of the upshift, and the change in the winding radius of the power transmission belt in the secondary pulley reliably follows the change in the winding radius of the power transmission belt in the primary pulley. As a result, careless loosening and slippage of the power transmission belt are prevented, and a smooth downshift is achieved. When the shift operation delay caused by the slack or slip between the power transmission belt and the secondary pulley is eliminated, the drive speed of the shift actuator is unnecessarily increased to cause useless slack or slip. As compared with the above, a high-speed downshift can be performed.

Further, storage means for storing the shift limit values of the four large and small systems, and the above-described engine power determination means and shift operation determination means are provided side by side, and the determination result of the engine power determination means and the shift operation determination means are provided. It is also possible to adopt a configuration in which a shift limit value of a system having a predetermined correspondence relationship is selected from among the shift limit values of the four large and small systems in accordance with the combination of the determination results.

In this case, when a load equal to or more than the set value acts on the engine and the upshift is being performed, the shift limit value of the system having the largest value is selected, and a load less than the set value is applied to the engine. In the state where the operation is being performed and the upshift is being performed, the shift limiting value of the system having the second largest value is selected, and the load greater than the set value is being applied to the engine and the downshift is being performed. In, the third largest gear change limit value is selected,
Further, in a state where a load less than the set value is applied to the engine and a downshift is being performed, the combination of the determination result and the speed change target to be selected are selected so as to select the speed limit value of the system having the smallest value. It is desirable to set the correspondence with the limit value. In the idling state where the tension of the power transmission belt is low, the winding radius of the power transmission belt on the primary pulley side is increased to cause the power transmission belt to bite into the secondary pulley, and in the engine operating state where the tension of the power transmission belt is high, In comparison with the case where the winding radius of the power transmission belt on the secondary pulley is increased by reducing the winding radius of the power transmission belt on the pulley side, the former case is generally the same as the case of increasing the winding radius of the power transmission belt on the secondary pulley. This is because slippage between the pulley and the pulley hardly occurs, and a higher-speed shift operation is allowed than in the latter case.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram schematically showing a main part of a continuously variable transmission 1 for an automobile according to an embodiment to which the present invention is applied.

The mechanical components of the continuously variable transmission 1 for an automobile are, as shown in FIG.
A primary pulley 4 provided at a position closer to the engine 2 on the power transmission path between the motor and the drive wheel 3, a secondary pulley 5 provided at a position closer to the drive wheel 3 on the power transmission path, and a primary A power transmission belt 6 wound between the pulley 4 and the secondary pulley 5, and a winding of the power transmission belt 6 on the primary pulley 4 by changing the width of the primary pulley 4 according to a commanded gear ratio. It is constituted by a speed change actuator 7 for adjusting the radius and a torque cam 8 built in the secondary pulley 5.

Of these, the primary pulley 4 is constituted by combining two discs 4a and 4b formed in a thin conical shape such that the apical angles of the discs 4a and 4b are opposed to each other so that the discs 4a and 4b can be separated from each other. The distance, that is, the width of the primary pulley 4 is adjusted by the speed change actuator 7.

The secondary pulley 5 is constituted by combining two discs 5a and 5b formed in a thin conical shape so that the apex angles of the discs 5a and 5b are opposed to each other, and each of the discs 5a and 5b has a power. By the force substantially proportional to the driving torque (rotational torque) transmitted from the transmission belt 6 to the secondary pulley 5, they are urged in a direction approaching each other, that is, a direction in which the width of the secondary pulley 5 is reduced. The source of this urging force is the torque cam 8 built in the secondary pulley 5. The function of the torque cam 8 itself has already been disclosed in Japanese Patent Laid-Open No. 10-54429.
The description is omitted because it is publicly known by reference numbers.

The speed change actuator 7 for adjusting the width of the primary pulley 4 is, for example, a shaft 7a which is fixed to the disk 4a so as not to rotate and cannot move in the axial direction and spline-fits the disk 4b so as to rotate and cannot move in the axial direction. And a sleeve 7b which secures the rotational degree of freedom of the disk 4b and slides on the outer surface thereof, and a feed screw 7 screwed to the sleeve 7b and fixed to the transmission body.
c and a motor 7d (pulse motor) for rotating the sleeve 7b relative to the feed screw 7c. In short, the rotation of the motor 7d applies an axial feed to the sleeve 7b to
By moving b along the shaft 7a, the distance between the disks 4a and 4b, that is, the width of the primary pulley 4, is adjusted.

As shown in FIG. 1, an output shaft 2a of the engine 2 and the primary pulley 4 are connected via a gear train 9 so as to be capable of transmitting power.
The drive wheel 3 is connected to the drive wheel 3 via a gear train 10, a clutch 11 and a drive chain 12 so that power can be transmitted.

In the above configuration, the motor 7d constituting the main part of the speed change actuator 7 is driven to feed the sleeve 7b in the direction of increasing the engagement with the feed screw 7c, and the width of the primary pulley 4 is increased. In this case, the groove width of the primary pulley 4 increases, and the power transmission belt 6 on the primary pulley 4 side moves radially inward of the primary pulley 4 along the conical slopes of the disks 4a and 4b. The winding radius of the power transmission belt 6 on the fourth side is reduced.

The winding radius of the power transmission belt 6 on the side of the secondary pulley 5 can be increased by an amount corresponding to the margin of the power transmission belt 6 caused by the reduction of the winding radius. The width of the pulley 5 is automatically reduced, and the power transmission belt 6 on the secondary pulley 5 side moves along the conical slopes of the disks 5a and 5b to the position of the winding radius allowed by this allowance. Extruded radially outward. By this operation, the gear ratio between the primary pulley 4 and the secondary pulley 5 increases,
That is, the downshift speed change operation is achieved.

On the other hand, when the motor 7d constituting the main part of the speed change actuator 7 is driven to feed the sleeve 7b in the direction of decreasing the engagement with the feed screw 7c to reduce the width of the primary pulley 4. In the meantime, the groove width of the primary pulley 4 decreases, and the power transmission belt 6 on the primary pulley 4 side moves radially outward of the primary pulley 4 along the conical slopes of the disks 4a and 4b. The winding radius of the power transmission belt 6 increases.

Then, the winding radius of the power transmission belt 6 on the secondary pulley 5 side decreases by an amount corresponding to the shortage of the power transmission belt 6 caused by the increase in the winding radius,
The power transmission belt 6 on the side of the secondary pulley 5 moves radially inward of the secondary pulley 5 while increasing the distance between the disks 5a and 5b against the urging force of the torque cam 8. With this operation, a direction in which the speed ratio between the primary pulley 4 and the secondary pulley 5 decreases, that is, an upshift speed change operation is achieved.

As shown in FIG. 1, the engine 2 includes:
A throttle opening sensor 13 for detecting a load acting on the engine 2 is provided, and an engine rotation sensor 14 for detecting an engine speed is provided at a position facing the output shaft 2a of the engine 2. ing.

Further, a vehicle speed sensor 16 for detecting the running speed of the vehicle is provided at a position facing the final output shaft 15 in the power transmission path. Further, an end face of a disk 4b constituting a part of the primary pulley 4 is provided. A pulley position sensor 17 is provided so as to slide the probe.

As is apparent from the above description of the operation of the mechanical components, the speed ratio between the primary pulley 4 and the secondary pulley 5 is determined by the width of the primary pulley 4, that is, the ratio between the disk 4a and the disk 4b. The value corresponding to the speed ratio can be detected by the pulley position sensor 17 as the distance between the disk 4a and the disk 4b.

Reference numeral 18 shown in FIG. 1 is a manual mode switch (mode selection means) for selecting one of the automatic transmission mode and the manual transmission mode, and this manual mode switch is ON. Sometimes, the manual shift mode is selected, and when the manual mode switch is OFF, the automatic shift mode is selected.

Reference numerals 19 and 20 denote an upshift switch and a downshift switch used in the manual shift mode, and the manual mode switch 18 is turned on.
The operation is permitted only under the conditions described. These switches 18, 19, 20 are provided near the steering wheel in the case of a motorcycle such as a scooter, and are replaced by a shift lever in the case of a four-wheeled vehicle.

Further, in the continuously variable transmission 1 for a vehicle according to the present embodiment, further, as a configuration unique to the embodiment,
A secondary pulley sensor 21 for detecting the rotation speed of the secondary pulley 5 is provided.

FIG. 2A is a functional block diagram schematically showing the configuration of the control unit 22 provided in the continuously variable transmission 1 for a vehicle according to the present embodiment. The main part of the control unit 22 includes a CPU 23 as an arithmetic unit and a RAM 24 used for temporary storage of arithmetic data, a storage unit for various data such as a shift limit value for a plurality of systems, and an operation program. ROM 25 and the like.

The CPU 23 functions as engine power determining means, shift operation determining means, shift limit value selecting means, and operating speed limiting means, as shown in FIG. 2B.

As shown in FIG. 2A, the various sensors 13, 14, 16, 17, 21 and the various switches 18,
The signals from 19 and 20 are input to the CPU 23 of the control unit 22 via the input circuit 26. Further, the motor 7d and the clutch 1
Drives 1 and the like are controlled by the drive circuits 28 and 29 in response to a command from the CPU 23 output via the output circuit 27. The clutch 11 is turned off when the vehicle stops, and the vehicle travels. Sometimes it is turned ON.

Next, the outline of the processing operation of the CPU 23 constituting the main part of the control unit 22 will be described with reference to the flowchart of the limit value selection processing shown in FIG. 3 and the actuator drive amount calculation processing shown in FIG.

In the limit value selection process, the limit value of the operating speed of the shift actuator 7 is selected based on the magnitude of the load acting on the engine 2 and the direction of the shift at the time of shifting, ie, whether the shift is upshift or downshift. The process for calculating the actuator drive amount is a process for controlling the drive of the shift actuator 7 at an operation speed that does not exceed the limit value selected in the limit value selection process and performing the shift. The so-called multitask processing is repeatedly executed by the CPU 23 every predetermined processing cycle.

Therefore, the CPU 23 as the shift operation judging means which has started the limit value selecting process shown in FIG.
(Step a1), it is determined whether the downshift operation is being performed by the downshift switch 20 (step a1).
2).

When it is determined that an upshift operation or a downshift operation is being performed, the CPU 23 as engine power determining means further outputs signals from the throttle opening sensor 13 and the engine rotation sensor 14. Whether the load acting on the engine 2 is equal to or greater than the set value corresponding to the current engine speed range, that is, the driving torque of the engine 2 is positively transmitted through the gear train 9 and the primary pulley 4. Is the engine power ON transmitted from the power transmission belt 6 to the secondary pulley 5 or the engine power OFF state where almost no driving torque is transmitted between the power transmission belt 6 and the secondary pulley 5 Is determined (step a3, step a4).

FIG. 5 shows steps a3 and a4.
FIG. 7 is a conceptual diagram showing a relationship between a set value of a throttle opening used as a criterion in the determination process and an engine rotation speed. As shown in FIG. 5, when the engine speed is low, the engine power is determined to be ON even if the throttle opening is relatively small, and when the engine speed is high, Is determined to be the engine power OFF even if the opening of the rottle is relatively large. This is because there is a difference in the basic throttle opening depending on the rotation speed of the engine.

Then, step a3 or step a
After the determination process of No. 4, CP as the shift limit value selecting means
U23 is determined in advance from a data table of four shift limit values stored in advance in the ROM 25 constituting the storage means in accordance with a combination of the ON / OFF state of the engine power and the directionality of the shift operation. The data table of the system having the corresponding relationship is read (steps a5 to a8).

That is, when it is determined that an upshift is being performed with the engine power ON, the upshift engine power ON data table is read (step a5), while the upshift is performed with the engine power OFF. If it is determined that
The upshift engine power OFF data table is read (step a6). Conversely, if it is determined that the downshift is being performed while the engine power is ON, the data table of the downshift engine power ON is read (step a7), while the engine power is OFF. If it is determined that the downshift is being performed, the data table of the downshift engine power OFF is read (step a8). This is the predetermined correspondence here.

FIG. 6 shows an example of a data table of the shift limit values of the four systems stored in the ROM 25. In FIG. 6, all four data tables are described in the same quadrant on the graph in order to clarify the magnitude relationship, but in reality,
Data in the downshift engine power ON data table and the data in the downshift engine power OFF data table are denoted by minus signs. As shown in FIG. 6, the data table of the upshift engine power ON has the largest absolute value of the shift limit value, and the data table of the upshift engine power OFF has the second largest absolute value of the shift limit value. The data table for the downshift engine power ON and the data table for the downshift engine power OFF follow.

The value of the shift limit value in each data table is set in accordance with the rotation speed of the secondary pulley 5. In each data table, the absolute value is higher when the rotation speed of the secondary pulley 5 is higher. A shift limit value having a large value is stored. This is because, even if the ON / OFF state of the engine power and the direction of the shift operation are the same, the radial movement of the power transmission belt 6 on the secondary pulley 5 is easier when the rotation speed of the secondary pulley 5 is higher. This is because a faster shift operation is possible.

In FIG. 6, for simplicity of description, each of the four data tables is shown in a graph, but in reality, these data tables show the rotational speed of the secondary pulley 5 and the shift limit value. Is stored in the ROM 25 as a collection of discontinuous points constituted by some two-dimensional array data in which the relationship between the two points is stored in a spot manner.

As shown in FIG. 6, each of the graphs representing the contents of the data table is constituted by a polygonal line composed of straight lines including several refraction points. It is sufficient to store several points of two-dimensional array data for each data table. The value of the shift limit value corresponding to an arbitrary rotation speed of the secondary pulley 5 can be easily calculated by performing linear interpolation processing using these two-dimensional array data.

Then, the CPU 23 which has read the data table of the system having a predetermined correspondence relationship by the processing of steps a5 to a8, furthermore, via the secondary pulley sensor 21, reads the current value of the rotation speed of the secondary pulley 5 It reads and executes a linear interpolation process based on the two-dimensional array data constituting the data table and the current value of the rotational speed of the secondary pulley 5 to determine the ON / OFF state of the engine power, the direction of the gear shift and the secondary A shift limit value corresponding to the rotation speed of the pulley 5 is determined, and this value is stored and held as the current shift limit value until the next upshift operation or the next downshift operation is performed. (Step a9).

Next, with reference to the actuator drive amount calculation process of FIG. 4, an outline of a process for controlling the drive of the shift actuator 7 at an operation speed not exceeding the shift limit value will be described.

The CPU 23 that has started the actuator drive amount calculation process first determines the engine load detected by the throttle opening sensor 13 and the engine rotation speed detected by the engine rotation sensor 14 and the above-described upshift switch 19 or downshift. Based on the operation of the shift switch 20, a basic target gear ratio, that is, a value of a gear ratio to be set between the primary pulley 4 and the secondary pulley 5 is obtained (step b1).

As described above, the gear ratio between the primary pulley 4 and the secondary pulley 5 is uniquely determined by the width of the primary pulley 4, that is, the separation distance between the disks 4a and 4b. In the process of b1, finally, the target value of the axial movement position of the sleeve 7b on the shaft 7a is obtained as the gear ratio.

Next, the CPU 23 subtracts the previous value of the target gear ratio stored in the process of step b5 in the actuator drive amount calculation process of the previous cycle from the value of the basic target gear ratio calculated in the process of step b1, The absolute value of the deviation of the gear ratio between the target gear ratio and the previous value of the gear ratio is determined, and it is determined whether or not the magnitude of the deviation is within the range of the current gear limit value (step b2). .

As described above, the speed ratio between the primary pulley 4 and the secondary pulley 5 is indicated by the axial movement position of the sleeve 7b with respect to the shaft 7a. The deviation of the gear ratio is calculated as the axial movement amount of the sleeve 7b on the shaft 7a by the process of step b2.

Here, when the result of the determination in step b2 is true, and it is clear that the deviation of the gear ratio between the basic target gear ratio and the previous target gear ratio is within the range of the gear shift limit value. It is not necessary to limit the operating speed of the speed change actuator 7 in the first embodiment. Therefore, in this case, the CPU 23
Is to apply the value of the basic target gear ratio calculated in the process of step b1 as the current target gear ratio value, that is, the value of the gear ratio to be set in the processing cycle (step b3).

On the other hand, when the determination result of step b2 is false, and it is clear that the deviation of the gear ratio between the basic target gear ratio and the previous target gear ratio exceeds the range of the gear limit value. If the value of the basic target gear ratio calculated in the process of step b1 is applied as it is as the value of the current target gear ratio, the operation speed of the gear shift actuator 7 becomes too fast, and the following operation of the torque cam 8 and the secondary pulley 5 becomes impossible. There is a possibility that slack or slippage may occur between the power transmission belt 6 and the secondary pulley 5 with a delay.

Therefore, in this case, the CPU 23 as the operating speed limiting means adds the value of the current gear shift limiting value obtained in step a9 in the determination value selecting process to the previous value of the target gear ratio, This value is set as the target gear ratio current value, that is, the gear ratio value to be set in the processing cycle (step b4). As described above, the shift limit values for the upshift engine power ON and the upshift engine power OFF have a plus sign, and the shift limit values for the downshift engine power ON and the downshift engine power OFF are themselves. Has a minus sign.

As described above, the current value of the target gear ratio, that is, the magnitude of the deviation between the value of the gear ratio to be set in the processing cycle and the previous value of the target gear ratio falls within the range of the gear limit value. Limited. This deviation is the axial movement amount of the sleeve 7b per processing cycle, that is, the movement speed of the sleeve 7b moving on the shaft 7a, and this is the operation speed of the speed change actuator 7, that is, the speed change speed.

Next, the CPU 23 stores the value of the current value of the target gear ratio finally determined by the processing of step b3 or step b4 as the previous value of the target speed ratio for the actuator drive processing of the next cycle (step b).
5) a deviation between the current value of the gear ratio and the current value of the target gear ratio, that is, the shaft 7a corresponding to the current value of the target gear ratio from the current position of the sleeve 7b on the shaft 7a.
The drive amount of the motor 7d required to move the sleeve 7b to the upper position is obtained, a movement command pulse is output within this one processing cycle, and the position on the shaft 7a at which the target gear ratio current value is achieved. The sleeve 7b is moved to the next position (step b6), and the actuator drive amount calculation process in this cycle is completed.

If the result of the determination in step b2 is false in the actuator drive amount calculation process in this cycle, the current value of the target gear ratio is set to a value smaller than the value of the basic target gear ratio. The deviation between the basic target gear ratio and the current value of the target gear ratio cannot be eliminated by only one processing cycle. In this case, the processing of step b1 to step b2 and the processing of step b4 to step b6 are repeatedly executed in the processing after the next cycle in the same manner as described above, and during this time, the operating speed of the shifting actuator 7 is determined by the operating speed determined by the shifting limit value. Will be clamped.

Then, while the moving speed is clamped and the sleeve 7b is moved while repeatedly executing such processing, the value of the deviation between the basic target gear ratio and the current target gear ratio becomes smaller and the step is performed. If the determination result of b2 becomes true, the process of step b3 is executed, the value of the target gear ratio current value matches the value of the basic target gear ratio, the deviation is eliminated, and the upshift operation or downshift operation is performed. The operation of the speed change actuator 7 for achieving the above is completed.

FIG. 7 shows an example of the relationship between the elapsed time and the actual gear ratio when the basic target gear ratio is changed by performing a downshift operation in the engine power ON state and the engine power OFF state. The slope of the straight line indicates the amount of movement of the shift actuator 7 per unit time, that is, the magnitude of the shift speed. The downshift is performed when the engine power is on when the engine power is off. The shifting speed is faster than when shifting,
It can be seen that the time required for shifting is short.

Since the value of the basic target gear ratio does not change until the upshift operation or the downshift operation is performed again, during this period, in the actuator drive amount calculation processing for each predetermined cycle, steps b1 to b3 and The processing of step b5 to step b6 is repeatedly executed. At this time, since the value of the basic target gear ratio and the value of the previous target gear ratio match each other, there is no deviation, and the gear shift actuator 7 remains stopped.

The processing when the upshift operation or the downshift operation is performed again is as described with reference to FIGS. 3 and 4.

[0076]

According to the continuously variable transmission for automobiles of the present invention, the power transmission belt positively transmits the driving torque to the secondary pulley to ensure the frictional contact between the secondary pulley and the power transmission belt. In the ON state, the operation speed of the speed change actuator is controlled by applying the speed change limit value of the large value system, while the power transmission belt does not actively transmit the driving torque to the secondary pulley and the power transmission belt transmits power to the secondary pulley. In the state of engine power OFF where the frictional contact with the belt is weakened, the operation speed of the speed change actuator is limited by applying a speed change limit value of a small system. As a result, a high-speed shift operation can be achieved unconditionally when the engine power is ON. Further, even when the engine power is off, the operation speed of the transmission actuator is effectively prevented from being loosened or slipping by limiting the operation speed of the transmission actuator, so that the operation speed of the transmission actuator is unnecessarily increased. A much faster shift operation can be achieved as compared to the case.

Further, in the case of an upshift in which the winding radius of the power transmission belt on the primary pulley is increased and the power transmission belt is pressed against the secondary pulley, a shift limiting value of a system having a large value is applied. While controlling the operation speed of the actuator, in the case of a downshift where the winding radius of the power transmission belt on the primary pulley is reduced and the power transmission belt is likely to be loosened, the shift limit value of the system having a small value is set. This is applied so as to limit the operation speed of the shift actuator. As a result, a high-speed upshift operation can be performed, and
Even in the case of a downshift operation, by limiting the operating speed of the shift actuator, the slack and slippage of the power transmission belt can be effectively prevented, so that the operating speed of the shift actuator is unnecessarily increased. A much faster downshift operation can be achieved.

Further, the optimum shift limit value is selected from the shift limit values of the four large and small systems according to the combination of the ON / OFF state of the engine power and the shift direction. The speed change process can be performed within a short time by performing the speed change process at the optimum operation speed.

Further, since slippage between the power transmission belt and the secondary pulley is prevented, the width adjustment operation of the secondary pulley using the biasing force of the torque cam can be reliably followed by the width adjustment operation of the primary pulley. It became so. Therefore, it is not necessary to provide separate hydraulic cylinders for each of the primary pulley and the secondary pulley to coordinate the operations of the primary pulley and the secondary pulley, and to perform a reliable shift operation with a simple configuration using one gear shift actuator and a torque cam. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing a main part of a continuously variable transmission for an automobile according to an embodiment to which the present invention is applied.

FIG. 2A is a functional block diagram schematically showing a configuration of a control unit provided in the vehicle continuously variable transmission according to the embodiment, and FIG. 2B is a schematic diagram showing functions of a CPU; It is a functional block diagram.

FIG. 3 is a flowchart illustrating an outline of a limit value selection process performed by a CPU of a control unit.

FIG. 4 is a flowchart illustrating an outline of an actuator drive amount calculation process performed by a CPU of a control unit.

FIG. 5 is a conceptual diagram showing a relationship between a set value of a throttle opening used for ON / OFF determination of engine power and an engine speed.

FIG. 6 is a conceptual diagram showing an example of a data table of shift limit values for four systems.

FIG. 7 shows the state of engine power ON and engine power O.
FIG. 7 is a conceptual diagram showing an example of a relationship between an elapsed time and a movement amount of a shift actuator when a basic target gear ratio is changed by performing a downshift operation in a state of FF.

[Explanation of symbols]

Reference Signs List 1 continuously variable transmission for automobile 2 engine 2a output shaft 3 drive wheel 4 primary pulley 4a, 4b disk 5 secondary pulley 5a, 5b disk 6 power transmission belt 7 speed change actuator 7a shaft 7b sleeve 7c feed screw 7d motor 8 torque cam 9 gear Row 10 Gear train 11 Clutch 12 Drive chain 13 Throttle opening sensor 14 Engine rotation sensor 15 Final output shaft 16 Vehicle speed sensor 17 Pulley position sensor 18 Manual mode switch (mode selection means) 19 Upshift switch 20 Downshift switch 21 Secondary pulley sensor 22 control unit 23 CPU (engine power determining means, shift operation determining means, shift limit value selecting means, operating speed limiting means) 24 RAM 25 ROM (noted) Means) 26 Input circuit 27 output circuits 28 and 29 drive circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J552 MA07 MA15 MA17 NA01 NB01 PA12 PA51 RA02 SA32 TB11 VA17Z VA37Z VA70Z VA74Z VB01Z VC01Z VC02W VC03Z VD17Z

Claims (3)

[Claims] 1. A primary pulley disposed at a position closer to the engine on a power transmission path between the engine and the drive wheel, and a primary pulley disposed at a position closer to the drive wheel on a power transmission path between the engine and the drive wheel. And a power transmission belt wound between the primary pulley and the secondary pulley, and a power transmission in the primary pulley by changing a width of the primary pulley according to a commanded gear ratio. A speed change actuator that adjusts a winding radius of the belt; and a primary actuator that urges the secondary pulley in a direction in which the width is reduced by a force substantially proportional to a driving torque transmitted from the power transmission belt to the secondary pulley. The secondary loop is driven by a change in the winding radius of the power transmission belt at the pulley. A torque cam for changing a winding radius of a power transmission belt in a gear train, a storage means for storing a shift limit value of two systems, large and small, for limiting an upper limit of an operation speed of the shift actuator, and setting in the engine. An engine power determining means for determining whether or not a load greater than a value is acting; and a system having a larger value when the engine power determining means determines that a load greater than a set value is acting on the engine. An engine for selecting a shift limiting value of a system with a smaller value when the engine power determining means determines that a load smaller than a set value is acting on the engine. Power-dependent shift limit value selecting means, and an operating speed limiter for limiting an upper limit of the operating speed of the shift actuator based on the selected shift limit value. A continuously variable transmission for an automobile, comprising a step and a step. 2. A shift operation determining means for determining whether an upshift is being performed or a downshift is being performed, instead of the engine power determining means and the engine power corresponding shift limit value selecting means, When it is determined by the shift operation determining means that an upshift is being performed, the shift operation limiting value of the system having the larger value is selected, while it is determined that the downshift is being performed by the shift operation determining means. 2. The continuously variable transmission according to claim 1, further comprising: a shift operation corresponding shift limit value selecting means for selecting a shift limit value of a system having a smaller value in the case of a shift. 3. A primary pulley disposed at a position closer to the engine on a power transmission path between the engine and the drive wheels, and a primary pulley disposed at a position closer to the drive wheels on a power transmission path between the engine and the drive wheels. And a power transmission belt wound between the primary pulley and the secondary pulley, and a power transmission in the primary pulley by changing a width of the primary pulley according to a commanded gear ratio. A speed change actuator that adjusts a winding radius of the belt; and a primary actuator that urges the secondary pulley in a direction in which the width is reduced by a force substantially proportional to a driving torque transmitted from the power transmission belt to the secondary pulley. The secondary loop is driven by a change in the winding radius of the power transmission belt at the pulley. A torque cam for changing a winding radius of a power transmission belt in a gear train, a storage means for storing shift limiting values of four large and small systems for limiting an upper limit of an operating speed of the shifting actuator, and setting in the engine. Engine power determining means for determining whether a load equal to or greater than a value is acting; shift operation determining means for determining whether an upshift is being performed or a downshift is being performed; and the engine power determining means. And a shift limiting value for selecting a shift limiting value of a system having a predetermined correspondence relationship from among the shift limiting values of the four large and small systems in accordance with a combination of the determination result of (i) and the determination result of the shift operation determining means. Value selecting means, and operating speed limiting means for restricting an upper limit of the operating speed of the shift actuator based on the selected shift limiting value. A continuously variable transmission for automobiles.