JP7733451B2 - Continuously variable transmission and control method for continuously variable transmission - Google Patents

Description

The present invention relates to a continuously variable transmission and a control method for a continuously variable transmission.

Patent Document 1 discloses a vehicle control device that changes the shift line used for shifting in an automatic transmission when the throttle is fully open based on whether the engine rotation speed can be controlled by an engine rotation control means. With this control device, when the engine rotation speed is controllable, the shift is performed when the engine rotation speed is high compared to when the engine rotation speed is not controllable.

Japanese Patent Application Laid-Open No. 2004-218785

Incidentally, continuously variable transmissions are set to a stepped transmission mode in which stepped shift control is performed in stages, just like stepped transmissions. For example, when the driver starts off with the accelerator fully open, an upshift is required when the engine speed is high.

However, in continuously variable transmissions, to prevent engine speed overshoot, the target engine speed is set so that it will reach that speed after a predetermined time. Therefore, when the engine speed required for an upshift is reached and an upshift is initiated, the engine speed after the predetermined time may not reach the required speed for an upshift. In other words, even if the driver's acceleration request is strong, an upshift may not be possible when the engine speed is high.

The present invention was made in consideration of the above problems, and aims to perform an upshift when the engine speed is high when the driver's acceleration request is strong.

According to one aspect of the present invention, a continuously variable transmission capable of continuously changing the gear ratio between an input shaft and an output shaft, when performing step-by-step stepped speed change control, sets a target rotational speed of the input shaft based on the vehicle speed that will be reached when a look-ahead time has elapsed until the actual rotational speed of the input shaft reaches the target rotational speed, and when the target rotational speed reaches an upshift determination rotational speed, determines to perform an upshift to change the gear ratio to the High side until the actual rotational speed of the input shaft reaches a rotational speed corresponding to the next higher gear, calculates the increased rotational speed of the input shaft that increases from the time the target rotational speed of the input shaft reaches the upshift determination rotational speed until the upshift actually begins , and begins the upshift when it is determined that the sum of the actual rotational speed of the input shaft and the increased rotational speed is equal to or greater than the upshift determination rotational speed .

According to another aspect of the present invention, a control method for a continuously variable transmission in which stepwise stepped speed change control is performed by continuously changing the speed ratio between an input shaft and an output shaft sets a target rotational speed of the input shaft based on the vehicle speed that will be reached when a look-ahead time has elapsed until the actual rotational speed of the input shaft reaches the target rotational speed when stepwise stepped speed change control is performed, and when the target rotational speed reaches an upshift determination rotational speed, determines to perform an upshift to change the gear ratio to the High side until the actual rotational speed of the input shaft reaches a rotational speed corresponding to the next higher gear, calculates an increased rotational speed of the input shaft that increases from the time the target rotational speed of the input shaft reaches the upshift determination rotational speed until an upshift is actually started , and starts an upshift when it is determined that the sum of the actual rotational speed of the input shaft and the increased rotational speed is equal to or greater than the upshift determination rotational speed .

In the above aspect, after the target rotational speed of the input shaft reaches the first target rotational speed and it is determined that an upshift should be performed to the second target rotational speed, the upshift begins after the rotational speed has further increased. Therefore, even when the driver's acceleration request is strong, an upshift can be performed when the engine rotational speed is high.

FIG. 1 is a schematic diagram of a vehicle equipped with a continuously variable transmission according to an embodiment of the present invention. FIG. 2 is a flowchart showing the process of the gear shift control during acceleration performed by the transmission controller. FIG. 3 is a diagram conceptually illustrating the upshift determination rotation speed. FIG. 4 is a timing chart illustrating the shift control during acceleration. FIG. 5 is a diagram conceptually illustrating the predicted vehicle speed. FIG. 6 is a flowchart showing the delay control based on the predicted vehicle speed, which is performed by the transmission controller. FIG. 7 is a diagram conceptually illustrating delay control based on predicted vehicle speed. FIG. 8 is a timing chart illustrating a case where delay control based on predicted vehicle speed is further applied to the gear change control during acceleration shown in FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following, a large gear ratio (reduction ratio) will be referred to as Low, and a small gear ratio (reduction ratio) will be referred to as High. Furthermore, changing the gear ratio to the Low side is referred to as Downshifting, and changing it to the High side is referred to as Upshifting.

Figure 1 is a schematic diagram of a vehicle 100 equipped with a continuously variable transmission 20 according to an embodiment of the present invention. As shown in Figure 1, the vehicle 100 includes an engine 10 as a drive source, the continuously variable transmission 20, an engine controller 30, and a transmission controller 40.

The continuously variable transmission 20 includes a torque converter 2, a forward/reverse switching mechanism 3 as a power transmission mechanism, a variator 4 as a transmission mechanism, a hydraulic control circuit 5, and an oil pump 6.

In the vehicle 100, rotation generated by the engine 10 is transmitted to the drive wheels 50 via a power transmission path consisting of the torque converter 2, forward/reverse switching mechanism 3, variator 4, gear set 7, and differential gear device 8.

The torque converter 2 is positioned downstream of the engine 10 in the power transmission path. The torque converter 2 is equipped with a lock-up clutch 2a. When the lock-up clutch 2a is engaged, the input shaft 2b, which serves as the input element of the torque converter 2, and the output shaft 2c, which serves as the output element, are directly connected, causing the input shaft 2b and output shaft 2c to rotate at the same speed. Therefore, when the lock-up clutch 2a is engaged, the rotation of the output shaft 10a of the engine 10 is transmitted directly from the output shaft 2c of the torque converter 2 to the forward/reverse switching mechanism 3.

The forward/reverse switching mechanism 3 primarily comprises a double pinion planetary gear set, whose sun gear is connected to the engine 10 via the torque converter 2, and whose carrier is connected to the input shaft 4d (primary pulley 4a) of the variator 4. The forward/reverse switching mechanism 3 also includes a forward clutch 3a that directly connects the sun gear of the double pinion planetary gear set to the carrier, and a reverse brake 3b that locks the ring gear. When the forward clutch 3a is engaged, the input rotation from the engine 10 via the torque converter 2 is transmitted directly to the primary pulley 4a, and when the reverse brake 3b is engaged, the input rotation from the engine 10 via the torque converter 2 is reversed, reduced in speed, and transmitted to the primary pulley 4a.

The variator 4 is positioned downstream of the engine 10 and torque converter 2 in the power transmission path. The variator 4 is a transmission mechanism (continuously variable transmission mechanism) that continuously changes the speed of the engine 10 rotation transmitted to the input shaft 4d and transmits it from the output shaft 4e to the drive wheels 50. In other words, the variator 4 continuously changes the gear ratio between the input shaft 4d and the output shaft 4e. The variator 4 includes a primary pulley 4a provided on the engine 10 side in the power transmission path, a secondary pulley 4b provided on the drive wheels 50 side, and an endless belt 4c wound around the primary pulley 4a and secondary pulley 4b.

In the variator 4, the hydraulic pressure supplied to the primary pulley 4a and the hydraulic pressure supplied to the secondary pulley 4b are controlled to change the contact radius between each of the pulleys 4a, 4b and the belt 4c, thereby changing the gear ratio. The belt 4c abuts against the sheave surfaces 4f, 4g of each of the pulleys 4a, 4b, transmitting power between the primary pulley 4a and the secondary pulley 4b.

The oil pump 6 is a mechanical oil pump that receives the rotation of the engine 10 and is driven using part of the engine 10's power. The oil discharged from the oil pump 6 is supplied to the hydraulic control circuit 5.

The hydraulic control circuit 5 includes a regulator valve 5a that adjusts the pressure of the hydraulic oil supplied from the oil pump 6 to generate the required hydraulic pressure, a primary solenoid valve 5b that adjusts the hydraulic pressure supplied to the primary pulley 4a, a secondary solenoid valve 5c that adjusts the hydraulic pressure supplied to the secondary pulley 4b, a lock-up solenoid valve 5d that adjusts the hydraulic pressure supplied to the lock-up clutch 2a, a select solenoid valve 5e that adjusts the hydraulic pressure supplied to the forward clutch 3a and the reverse brake 3b, and a manual valve 5f that switches the hydraulic pressure supply path to the forward clutch 3a and the reverse brake 3b.

The hydraulic control circuit 5 supplies adjusted hydraulic pressure to the torque converter 2, forward/reverse switching mechanism 3, and variator 4 based on control signals from the transmission controller 40.

The engine controller 30 is composed of a microcomputer equipped with a CPU, RAM, ROM, input/output interface, etc. The engine controller 30 performs various processes by having the CPU read and execute programs stored in the ROM. The engine controller 30 can also be composed of multiple microcomputers.

The engine controller 30 controls the rotational speed, torque, etc. of the engine 10 based on signals from various sensors that detect the status of each part of the vehicle 100.

The transmission controller 40 is composed of a microcomputer equipped with a CPU, RAM, ROM, input/output interface, etc., and is connected to the engine controller 30 so that it can communicate with it. The transmission controller 40 performs various processes by having the CPU read and execute programs stored in the ROM. The transmission controller 40 can also be composed of multiple microcomputers. The transmission controller 40 and engine controller 30 may also be integrated into a single controller.

The transmission controller 40 controls the engagement state of the lock-up clutch 2a, the gear ratio of the variator 4, the engagement state of the forward clutch 3a and reverse brake 3b, etc. based on signals from various sensors that detect the state of each part of the vehicle 100.

The transmission controller 40 receives inputs such as a signal from an accelerator pedal position sensor 61 that detects the accelerator pedal position APO, a signal from a brake fluid pressure sensor 62 that detects the brake fluid pressure BRP corresponding to the amount of brake pedal operation, a signal from an inhibitor switch 64 that detects the position of the shifter 63, a signal from a turbine rotation speed sensor 65 that detects the rotation speed Nt of the output shaft 2c of the torque converter 2, a signal from a primary rotation speed sensor 66 that detects the rotation speed Np of the input shaft 4d (primary pulley 4a) of the variator 4, a signal from a secondary rotation speed sensor 67 that detects the rotation speed Ns of the output shaft 4e (secondary pulley 4b) of the variator 4, a signal from a primary hydraulic pressure sensor 68 that detects the primary hydraulic pressure Pp supplied to the primary pulley 4a, and a signal from a secondary hydraulic pressure sensor 69 that detects the secondary hydraulic pressure Ps supplied to the secondary pulley 4b.

Next, the gear shift control processing performed by the transmission controller 40 during acceleration will be described with reference to Figures 2 to 4. The gear shift control processing is executed by the transmission controller 40 at regular intervals.

First, the gear shift control process performed by the transmission controller 40 during acceleration will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing the gear shift control process performed by the transmission controller 40 during acceleration. Figure 3 is a conceptual diagram showing the upshift determination rotation speed.

Shift control during acceleration is performed when the driver's request for acceleration is strong, such as when the driver depresses the accelerator pedal and the vehicle 100 fully accelerates. Here, the continuously variable transmission 20 is a continuously variable transmission that performs stepped shift control like a stepped transmission.

When the lock-up clutch 2a is engaged in the torque converter 2, the rotational speed of the input shaft 2b (the rotational speed of the engine 10) is the same as the rotational speed of the output shaft 2c (the rotational speed of the input shaft 4d of the variator 4). On the other hand, when the lock-up clutch 2a is not engaged in the torque converter 2, the rotational speed of the input shaft 2b is higher than the rotational speed of the output shaft 2c. The continuously variable transmission 20 makes an upshift decision based on the rotational speed of the input shaft 4d, but when the lock-up clutch 2a is not engaged, the upshift decision is made with a margin equal to the difference in rotational speed between the input shaft 2b and the output shaft 2c to prevent an excessive increase in the rotational speed of the engine 10.

However, for example, when the lockup clutch 2a is about to be fully engaged (slipping), the difference in rotational speed between the input shaft 2b and the output shaft 2c is smaller than when the lockup clutch 2a is disengaged. In other words, the difference in rotational speed between the input shaft 2b and the output shaft 2c changes depending on the degree of engagement of the lockup clutch 2a. Therefore, if an upshift is performed with a margin equal to the difference in rotational speed between the input shaft 2b and the output shaft 2c when the lockup clutch 2a is about to be fully engaged, as is the case when the lockup clutch 2a is disengaged, there is a risk that the upshift will occur while the engine 10 rotational speed is still low, even though the engine 10 rotational speed could be increased. Therefore, the continuously variable transmission 20 takes the degree of engagement of the lockup clutch 2a into consideration and performs gear shift control during acceleration as follows.

In step S11 of FIG. 2, the transmission controller 40 detects the current actual slip rotation speed of the torque converter 2. Specifically, the transmission controller 40 detects the rotation speed of the input shaft 2b based on a signal from the engine controller 30, detects the rotation speed of the output shaft 2c based on a signal from the turbine rotation speed sensor 65, and determines the difference in rotation speed between the input shaft 2b and the output shaft 2c as the actual slip rotation speed.

In step S12, the transmission controller 40 detects the output torque of the engine 10 based on a signal from the engine controller 30.

In step S13, the excess slip rotational speed of the torque converter 2 that may occur in the future is calculated. The excess slip rotational speed is calculated based on the difference between the current output torque and maximum torque of the engine 10 (remaining output torque) and the fluid characteristics of the torque converter 2.

Specifically, the greater the difference between the current output torque of the engine 10 and the maximum torque, the greater the potential slip rotation speed of the torque converter 2 that may occur when the accelerator pedal is further depressed. In other words, the greater the current output torque of the engine 10, the smaller the difference from the maximum torque, and therefore the smaller the potential slip rotation speed of the torque converter 2 that may occur when the accelerator pedal is further depressed. Therefore, the excess slip rotation speed is set to decrease as the current output torque of the engine 10 increases.

In step S14, the transmission controller 40 calculates the upshift determination rotation speed by subtracting the actual slip rotation speed detected in step S11 and the excess slip rotation speed calculated in step S13 from the upper limit rotation speed of the primary pulley 4a when the lock-up clutch 2a is engaged (LU upper limit PRI rotation speed).

Specifically, as shown in FIG. 3, the rotational speed of the engine 10 is higher than the rotational speed of the primary pulley 4a (PRI rotational speed) by the amount of the current actual slip rotational speed. Therefore, the upshift determination rotational speed is determined by subtracting the current actual slip rotational speed and the potential excess slip rotational speed of the torque converter 2 that may occur in the future from the LU upper limit PRI rotational speed. The LU upper limit PRI rotational speed is set lower than the maximum rotational speed of the engine 10 to prevent excessive increases in the rotational speed of the engine 10.

When the lock-up clutch 2a is engaged, the actual slip rotational speed and excess slip rotational speed are both 0. Therefore, the upshift determination rotational speed is the same as the LU upper limit PRI rotational speed.

Returning to FIG. 2, in step S15, the transmission controller 40 determines whether the target primary pulley rotation speed (target PRI rotation speed) is equal to or greater than the upshift determination rotation speed. If it is determined in step S15 that the target PRI rotation speed is equal to or greater than the upshift determination rotation speed, the process proceeds to step S16. On the other hand, if it is determined in step S15 that the target PRI rotation speed is not equal to or greater than the upshift determination rotation speed, i.e., if it is determined that the target PRI rotation speed is lower than the upshift determination rotation speed, the processes of steps S11 to S15 are repeated.

In step S16, the transmission controller 40 determines to perform an upshift. Then, in step S17, the transmission controller 40 performs an upshift of the continuously variable transmission 20. Specifically, the transmission controller 40 performs an upshift until the PRI rotation speed reaches the rotation speed corresponding to the next higher gear.

Next, the gear shift control performed by the transmission controller 40 during acceleration will be described in detail with reference to Figure 4. Figure 4 is a timing chart illustrating gear shift control during acceleration.

In Figure 4, the horizontal axis represents time [sec], and the vertical axis represents accelerator pedal opening APO, vehicle speed [km/h], target primary pulley rotation speed (target PRI rotation speed: dashed line) [rpm], engine rotation speed (solid line) [rpm], primary pulley rotation speed (PRI rotation speed: thin solid line) [rpm], target primary pulley rotation speed (target PRI rotation speed: thin dashed line) [rpm] of the comparative example, target gear ratio (dashed line), and actual gear ratio (solid line).

The target PRI rotation speed in the comparative example represents a case where an upshift determination is made without applying this embodiment, using two threshold values: one for when the lockup clutch 2a is engaged and one for when it is not engaged. Specifically, when the lockup clutch 2a is engaged, the threshold value is the lockup upper limit primary pulley rotation speed (LU upper limit PRI rotation speed), and when the lockup clutch 2a is not engaged, the threshold value is the unlocking upper limit primary pulley rotation speed (UnLU upper limit PRI rotation speed).

At time T11, in the automatic transmission according to the comparative example, the target PRI rotation speed has reached the UnLU upper limit PRI rotation speed, so the transmission controller 40 makes an upshift determination. Similarly, at time T12, in the automatic transmission according to the comparative example, the target PRI rotation speed has reached the UnLU upper limit PRI rotation speed, so the transmission controller 40 makes an upshift determination.

As such, in the automatic transmission of the comparative example, an upshift decision is made and an upshift is executed before the rotational speed of the engine 10 becomes sufficiently high. As a result, the engine 10 cannot be used at high rotational speeds.

In contrast, in the continuously variable transmission 20 according to this embodiment, the threshold value is the upshift determination rotation speed obtained by subtracting the current actual slip rotation speed and the excess slip rotation speed of the torque converter 2 that may occur in the future from the LU upper limit PRI rotation speed of the primary pulley 4a when the lock-up clutch 2a is engaged.

At time T21, the transmission controller 40 makes an upshift decision because the target PRI rotation speed has reached the upshift decision rotation speed. That is, when the lock-up clutch 2a is disengaged or slipping, an upshift is initiated when the rotation speed of the input shaft 2b reaches the upshift decision rotation speed, which is the LU upper limit PRI rotation speed minus the current actual slip rotation speed and the potential excess slip rotation speed of the torque converter 2. As a result, the upshift decision is made when the rotation speed of the engine 10 is higher than at time T11, and the upshift is not performed until the rotation speed of the engine 10 has reached a sufficiently high level at time T22. This allows the engine 10 to be used at even higher rotation speeds.

At time T23, the rotational speed of the engine 10 has decreased to the speed at which the gear ratio is shifted to the next higher gear in stepped transmission control, and from this point the rotational speed of the engine 10 begins to increase again.

Similarly, at time T24, the target PRI rotation speed of the continuously variable transmission 20 according to this embodiment has reached the upshift determination rotation speed, so the transmission controller 40 makes an upshift determination. At this time, the lockup clutch 2a is on the verge of being fully engaged. Therefore, the actual slip rotation speed and the potential excess slip rotation speed of the torque converter 2 that may occur from this point on are smaller than those at time T21. Therefore, the upshift determination rotation speed is set higher than those at time T21. In this way, the upshift determination is made when the rotation speed of the engine 10 is higher than at time T12, so the upshift is not performed until the rotation speed of the engine 10 has sufficiently increased at time T25. This allows the engine 10 to be used at higher rotation speeds.

At time T26, the rotational speed of the engine 10 has decreased to the speed at which the gear ratio is shifted to the next higher gear in stepped transmission control, and from this point the rotational speed of the engine 10 begins to increase again.

At time T27, the target PRI rotation speed of the continuously variable transmission 20 according to this embodiment reaches the upshift determination rotation speed, so the transmission controller 40 makes an upshift determination. At this time, the lockup clutch 2a is fully engaged. Therefore, the upshift determination rotation speed matches the LU upper limit PRI rotation speed.

As described above, in the continuously variable transmission 20, when the lock-up clutch 2a is engaged, an upshift begins when the rotational speed of the input shaft 2b reaches a first rotational speed. When the lock-up clutch 2a is disengaged or slipping, an upshift begins when the rotational speed of the input shaft 2b reaches a second rotational speed, which is the first rotational speed minus a first predetermined rotational speed. The first predetermined rotational speed is set smaller the greater the output torque of the engine 10. Specifically, the first predetermined rotational speed is the sum of the actual slip rotational speed of the lock-up clutch 2a and the excess slip rotational speed of the lock-up clutch 2a that may occur before an upshift begins.

When the output torque of the engine 10 is high, the sum of the current actual slip rotation speed and the potential excess slip rotation speed of the torque converter 2 (first predetermined rotation speed) is set to a small value. As a result, the upshift is performed when the engine 10 rotation speed is higher, so the engine 10 rotation speed can be increased to match the driver's acceleration request before shifting gears. Therefore, when the driver's acceleration request is high, the upshift can be performed when the engine 10 rotation speed is high. Therefore, gear changes can be performed in line with the driver's intentions. Furthermore, in this case, because the difference from the maximum torque of the engine 10 is small, an excessive increase in the engine 10 rotation speed can be suppressed even if the engine 10 output torque increases before the upshift.

On the other hand, when the output torque of the engine 10 is small, it may deviate from the maximum torque of the engine 10 compared to when the output torque is large. In such a state, the output torque of the engine 10 may become large before an upshift is performed, and may exceed the rotational speed of the engine 10 at which the upshift should occur.

In contrast, with the continuously variable transmission 20, when the output torque of the engine 10 is small, the upshift is performed at a correspondingly lower engine 10 rotational speed, so the timing of the upshift is delayed, preventing the engine 10 rotational speed from increasing excessively.

In addition, even if the lock-up clutch 2a is slipping, an upshift will begin when the second rotational speed, calculated by subtracting the actual slip rotational speed and any excess slip rotational speed that may occur before the upshift is initiated, is reached from the first rotational speed. This prevents the engine 10 rotational speed from increasing excessively, and allows upshifts to be performed at a high rotational speed when the engine 10 is running at close to maximum torque. This allows gear changes to be performed in line with the driver's intentions.

The variator 4 is a continuously variable transmission mechanism that continuously changes the gear ratio between the input shaft 2b and the output shaft 4e. When the lock-up clutch 2a is engaged, the variator 4 upshifts to a third rotational speed once the rotational speed of the input shaft 2b reaches a first rotational speed. When the lock-up clutch 2a is disengaged or slipping, the variator 4 upshifts to a third rotational speed once the rotational speed of the input shaft 2b reaches a second rotational speed until the third rotational speed is reached.

As a result, even when the gear shift control during acceleration according to this embodiment is applied to a continuously variable transmission that performs step-by-step gear shift control like a stepped transmission, upshifts can be performed when the engine 10 rotation speed is high if the driver requests a large amount of acceleration. Therefore, gear shifts can be performed in line with the driver's wishes.

Next, with reference to Figures 5 to 8, we will explain the delay control based on the predicted vehicle speed in the gear change control during acceleration performed by the transmission controller 40. The delay control based on the predicted vehicle speed is executed by the transmission controller 40 at regular intervals.

First, with reference to Figures 5 to 7, the delay control based on the predicted vehicle speed performed by the transmission controller 40 will be described. Figure 5 is a diagram conceptually explaining the predicted vehicle speed. Figure 6 is a flowchart showing the delay control based on the predicted vehicle speed performed by the transmission controller 40. Figure 7 is a diagram conceptually explaining the delay control based on the predicted vehicle speed.

As shown in FIG. 5, in the continuously variable transmission 20, when an upshift is determined and an upshift is actually initiated, the PRI rotation speed gradually increases and then decreases toward the target PRI rotation speed after the upshift. Therefore, in the continuously variable transmission 20, to prevent the engine 10 rotation speed from overshooting and increasing excessively, the target PRI rotation speed is set from the PRI rotation speed after the look-ahead time (first predetermined time), i.e., the vehicle speed after the look-ahead time (look-ahead vehicle speed). This look-ahead time is set to, for example, 0.25 seconds.

In this case, if an upshift is initiated when the target PRI rotation speed reaches the upshift determination rotation speed, the upshift will be initiated while the PRI rotation speed is still low, which could mean that the PRI rotation speed after the look-ahead time does not reach the upshift determination rotation speed. In other words, even if the driver's acceleration request is strong, it may not be possible to perform an upshift when the engine 10 rotation speed is high. Therefore, the continuously variable transmission 20 takes the look-ahead vehicle speed into consideration and performs gear shift control during acceleration as follows.

In step S21 of FIG. 6, the transmission controller 40 determines whether an upshift decision has been made. If it is determined in step S21 that an upshift decision has been made, the process proceeds to step S22. The process of step S21 returns "Yes" if an upshift decision has been made in step S16 of FIG. 2. On the other hand, if it is determined in step S21 that an upshift decision has not been made, the process of step S21 is repeated.

In step S22, the transmission controller 40 detects the PRI rotational speed based on the signal from the primary rotational speed sensor 66.

In step S23, the transmission controller 40 calculates the increased rotational speed of the primary pulley 4a that increases during the upshift after the upshift has started.

In step S24, the transmission controller 40 determines whether the sum of the PRI rotation speed and the increased rotation speed is equal to or greater than the upshift determination rotation speed (first target rotation speed) at the time of upshift determination. If it is determined in step S24 that the sum of the PRI rotation speed and the increased rotation speed is not equal to or greater than the upshift determination rotation speed at the time of upshift determination, i.e., is lower than the upshift determination rotation speed at the time of upshift determination, the processing of steps S22 to S24 is repeated. On the other hand, if it is determined in step S24 that the sum of the PRI rotation speed and the increased rotation speed is equal to or greater than the upshift determination rotation speed at the time of upshift determination, the processing proceeds to step S17. In other words, the transmission controller 40 performs delay control by repeating the processing of step S24 until the sum of the PRI rotation speed and the increased rotation speed reaches the upshift determination rotation speed at the time of upshift determination.

Here, we will explain delay control in detail with reference to Figure 7.

At time T1, an upshift is determined, and the target gear ratio of the continuously variable transmission 20 is changed from R1 to R2. Here, if an upshift is performed at time T1, the transmission controller 40 calculates the increased rotational speed ΔS1 that increases during the upshift.

At time T2, the transmission controller 40 determines that the sum of the PRI rotation speed and the increased rotation speed ΔS2 has reached the upshift determination rotation speed. The transmission controller 40 initiates an upshift of the continuously variable transmission 20 at time T2, which is delayed from time T1 when the upshift determination was made. At this time, the delay-adjusted increased rotation speed Sa, which increases from time T1 when it is determined that an upshift will be performed to time T2 when the upshift is initiated, corresponds to the predetermined rotation speed. The delay-adjusted increased rotation speed ΔSa is set based on the PRI rotation speed that increases from the time the target PRI rotation speed reaches the upshift determination rotation speed until the upshift is actually performed. This allows the PRI rotation speed to be used up to the upshift determination rotation speed. Therefore, when the driver's acceleration request is strong, an upshift can be performed at an even higher engine 10 rotation speed.

Similarly, at time T3, an upshift is determined, and the target gear ratio of the continuously variable transmission 20 is changed from R2 to R3. Here, if an upshift is performed at time T3, the transmission controller 40 calculates the increased rotational speed ΔS3 that increases during the upshift.

At time T4, the transmission controller 40 determines that the sum of the PRI rotation speed and the increased rotation speed ΔS4 has reached the upshift determination rotation speed. The transmission controller 40 initiates an upshift of the continuously variable transmission 20 at time T4, which is delayed from time T3 when the upshift determination was made. At this time, the delay-adjusted increased rotation speed Sb, which is the increase from time T3 when it was determined that an upshift would be performed to time T4 when the upshift is initiated, corresponds to the predetermined rotation speed. The delay-adjusted increased rotation speed ΔSb is also set based on the PRI rotation speed that increases from the time the target PRI rotation speed reaches the upshift determination rotation speed until the upshift is actually performed. This allows the PRI rotation speed to be used up to the upshift determination rotation speed. Therefore, when the driver's acceleration request is strong, an upshift can be performed at an even higher engine 10 rotation speed.

Returning to FIG. 6 , in step S17, the transmission controller 40 executes an upshift of the continuously variable transmission 20. Specifically, when the PRI rotation speed reaches the second rotation speed, the transmission controller 40 executes an upshift until the PRI rotation speed reaches the rotation speed corresponding to the next higher gear (second target rotation speed).

Next, the gear shift control during acceleration performed by the transmission controller 40 will be described in detail with reference to Figure 8. Figure 8 is a timing chart that explains the case where delay control based on predicted vehicle speed is further applied to the gear shift control during acceleration shown in Figure 4.

In Figure 8, the horizontal axis represents time [sec], and the vertical axis represents accelerator pedal opening APO, predicted vehicle speed (dashed line) [km/h], actual vehicle speed (solid line) [km/h], target primary pulley rotation speed (target PRI rotation speed: dashed line) [rpm], engine rotation speed (solid line) [rpm], primary rotation speed (PRI rotation speed: thin solid line) [rpm], engine rotation speed (thin dashed line) of the comparative example [rpm], target gear ratio (dashed line), and actual gear ratio (solid line).

The PRI rotation speed of the comparative example is the rotation speed of the engine 10 shown in Figure 4 when delay control based on the predicted vehicle speed is not applied.

At time T31, the transmission controller 40 performs an upshift determination because the target PRI rotation speed has reached the upshift determination rotation speed. The upshift determination is similar to that performed at time T21 in Figure 4, so a detailed description will be omitted here.

In the continuously variable transmission of the comparative example, an upshift begins at time T31, and the rotational speed of the engine 10 reaches its maximum value during the gear change at time T32. From there, the PRI rotational speed and the rotational speed of the engine 10 decrease until the gear change to the next higher gear is achieved.

In contrast, when delay control based on predicted vehicle speed is applied, the execution of the upshift is delayed, and the engine 10 rotational speed reaches its maximum value during the shift at time T33, which is later than time T32. At this time, the PRI rotational speed has reached the upshift determination rotational speed when the upshift determination was made, and the engine 10 rotational speed has reached the LU upper limit PRI rotational speed.

Similarly, at time T34, the target PRI rotation speed of the continuously variable transmission 20 according to this embodiment reaches the upshift determination rotation speed, so the transmission controller 40 makes an upshift determination. Then, the execution of the upshift is delayed, and at time T35, the rotation speed of the engine 10 reaches the maximum value during the shift. At this time as well, the PRI rotation speed has reached the upshift determination rotation speed when the upshift determination was made, and the rotation speed of the engine 10 has reached the LU upper limit PRI rotation speed.

At time T36, the target PRI rotation speed reaches the upshift determination rotation speed, so the transmission controller 40 makes an upshift determination. The execution of the upshift is then delayed, and at time T37 the engine 10 rotation speed reaches its maximum value during the shift. At this time, too, the PRI rotation speed has reached the upshift determination rotation speed when the upshift determination was made, and the engine 10 rotation speed has reached the LU upper limit PRI rotation speed.

As described above, when the target PRI rotation speed, which is set based on the vehicle speed to be reached when the look-ahead time (first predetermined time) has elapsed, reaches the upshift determination rotation speed (first target rotation speed), the continuously variable transmission 20 determines that an upshift will be performed until the PRI rotation speed reaches the rotation speed corresponding to the next higher gear (second target rotation speed), and then initiates an upshift after the PRI rotation speed has increased by the delay-amount increased rotation speed (predetermined rotation speed) after the target PRI rotation speed reaches the upshift determination rotation speed (first target rotation speed).

As a result, once the target PRI rotation speed reaches the upshift determination rotation speed and it is determined that an upshift should be performed to the second target rotation speed, the upshift is initiated after the PRI rotation speed has further increased. Therefore, when the driver's acceleration request is strong, an upshift can be performed when the engine 10 rotation speed is high. This allows gear changes to be performed in line with the driver's intentions.

In addition, the delay increase in rotation speed is set based on the PRI rotation speed of the primary pulley 4a (input shaft 4d) that increases from the time the target PRI rotation speed reaches the upshift determination rotation speed until the actual upshift is performed.

This prevents the engine 10 rotation speed from becoming too high, even if the engine 10 rotation speed is set high when an upshift is initiated.

In the above embodiment, when the target PRI rotation speed, which is set based on the vehicle speed reached after the first predetermined time has elapsed, reaches the first target rotation speed, it is determined that an upshift should be performed to the second target rotation speed, and the upshift is initiated after the PRI rotation speed has increased by the delay-amount increase rotation speed after reaching the upshift determination rotation speed.

Alternatively, an upshift may be initiated after a second predetermined time has elapsed since the PRI rotation speed reaches the upshift determination rotation speed. This second predetermined time is set based on the PRI rotation speed of the primary pulley 4a (input shaft 4d) that increases from the time the target PRI rotation speed reaches the upshift determination rotation speed until the actual upshift is performed.

In this case, too, once the PRI rotation speed reaches the upshift determination rotation speed and it is determined that an upshift should be performed to the second target rotation speed, the upshift is initiated after the PRI rotation speed has further increased. Therefore, when the driver's request for acceleration is strong, an upshift can be performed while the engine 10 rotation speed is high. This allows gear changes to be performed in line with the driver's intentions.

The configuration and effects of this embodiment will now be explained.

(1) (5) The continuously variable transmission 20, which continuously changes the gear ratio between the input shaft 4d and the output shaft 4e, determines to perform an upshift to the second target rotation speed when the target PRI rotation speed, which is set based on the vehicle speed reached when the look-ahead time (first predetermined time) has elapsed, reaches the upshift determination rotation speed (first target rotation speed). After the target PRI rotation speed reaches the upshift determination rotation speed (first target rotation speed), the PRI rotation speed increases by a delay-amount increased rotation speed (predetermined rotation speed), and then the upshift is initiated.

With this configuration, once the target PRI rotation speed reaches the upshift determination rotation speed and it is determined that an upshift should be performed to the second target rotation speed, the upshift is initiated after the PRI rotation speed has further increased. Therefore, even if the driver's acceleration request is strong, an upshift can be performed while the engine 10 rotation speed is high. Therefore, gear changes can be performed in line with the driver's intentions.

(2) The delay increase in rotational speed is set based on the PRI rotational speed of the primary pulley 4a (input shaft 4d) that increases from the time the target PRI rotational speed reaches the upshift determination rotational speed until the actual upshift is performed.

This configuration prevents the engine 10 rotation speed from becoming too high, even if the engine 10 rotation speed is set high when an upshift is initiated.

(3) (6) The continuously variable transmission 20, which continuously changes the gear ratio between the input shaft 4d and the output shaft 4e, determines to perform an upshift to the second target rotation speed when the target PRI rotation speed, which is set based on the vehicle speed reached when the look-ahead time (first predetermined time) has elapsed, reaches the upshift determination rotation speed (first target rotation speed), and starts an upshift after the second predetermined time has elapsed since the PRI rotation speed reached the upshift determination rotation speed.

With this configuration, once the PRI rotation speed reaches the upshift determination rotation speed and it is determined that an upshift should be performed to the second target rotation speed, the upshift is initiated after the PRI rotation speed has further increased. Therefore, even if the driver's request for acceleration is strong, an upshift can be performed while the engine 10 rotation speed is high. Therefore, gear changes can be performed in line with the driver's intentions.

(4) The second predetermined time is set based on the PRI rotation speed of the primary pulley 4a (input shaft 4d) that increases from the time the target PRI rotation speed reaches the upshift determination rotation speed until an upshift is actually performed.

This configuration prevents the engine 10 rotation speed from becoming too high, even if the engine 10 rotation speed is set high when an upshift is initiated.

The above describes an embodiment of the present invention, but the above embodiment merely illustrates one application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment.

For example, in the above embodiment, the continuously variable transmission 20 is described as a continuously variable transmission in which stepped, stepped shift control is performed, like a stepped transmission. However, the present invention can also be applied to a continuously variable transmission in which the driver can manually operate stepped shifts, in which the rotation speed of the engine 10 increases without the driver performing an upshift operation, and the transmission controller 40 automatically performs an upshift.

20 Continuously variable transmission 4d Input shaft 4e Output shaft

Claims (2)

A continuously variable transmission capable of continuously changing the gear ratio between the input shaft and the output shaft, when stepwise variable speed control is performed,
a target rotation speed of the input shaft is set based on a vehicle speed that will be reached when a look-ahead time has elapsed until the actual rotation speed of the input shaft reaches the target rotation speed, and when the target rotation speed reaches an upshift determination rotation speed, it is determined that an upshift will be performed to change the gear ratio to the High side until the actual rotation speed of the input shaft reaches a rotation speed corresponding to the next higher gear;
an increased rotation speed of the input shaft that increases from when the target rotation speed of the input shaft reaches the upshift determination rotation speed until an upshift is actually started , and an upshift is started when it is determined that the sum of the actual rotation speed of the input shaft and the increased rotation speed is equal to or greater than the upshift determination rotation speed;
Continuously variable transmission. A control method for a continuously variable transmission capable of continuously changing the gear ratio between an input shaft and an output shaft, wherein when stepwise variable speed control is performed,
a target rotation speed of the input shaft is set based on a vehicle speed that will be reached when a look-ahead time has elapsed until the actual rotation speed of the input shaft reaches the target rotation speed, and when the target rotation speed reaches an upshift determination rotation speed, it is determined that an upshift will be performed to change the gear ratio to the High side until the actual rotation speed of the input shaft reaches a rotation speed corresponding to the next higher gear ;
an increased rotation speed of the input shaft that increases from when the target rotation speed of the input shaft reaches the upshift determination rotation speed until an upshift is actually started , and an upshift is started when it is determined that the sum of the actual rotation speed of the input shaft and the increased rotation speed is equal to or greater than the upshift determination rotation speed;
A method for controlling a continuously variable transmission.