Continuously variable transmission and control method for continuously variable transmission

Abstract

To perform an upshift with an engine in a state with a high rotation speed when driver's acceleration demand is large.SOLUTION: A continuously variable transmission, which performs a stepless change in a transmission gear ratio between an input shaft and an output shaft,: determines that an upshift will be performed to a second target rotation speed when a target rotation speed of the input shaft which is set on the basis of a vehicle speed to be achieved after a lapse of first predetermined time becomes a first target rotation speed; and starts the upshift when the rotation speed of the input shaft is increased by a predetermined rotation speed after the target rotation speed of the input shaft reaches the first target rotation speed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a continuously variable transmission and a control method for a continuously variable transmission. [Background technology]

[0002] Patent Document 1 discloses a vehicle control device that changes a 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. In 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-218785 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 a driver starts off with the accelerator fully open, an upshift is required when the engine speed is high.

[0005] However, in a continuously variable transmission, the target engine speed is set to a certain speed after a predetermined time to prevent the engine speed from overshooting. Therefore, when the engine speed reaches the speed required for an upshift and an upshift is initiated, the engine speed after the predetermined time may not reach the speed required for the upshift. In other words, even if the driver requests a large acceleration, an upshift may not be possible when the engine speed is high.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has as its object to perform an upshift when the engine rotation speed is high when the driver's request for acceleration is strong. [Means for solving the problem]

[0008] According to one aspect of the present invention, the gear ratio between the input shaft and the output shaft can be changed continuously. possible The continuously variable transmission is When step-by-step variable speed control is performed, the time it takes for the actual rotation speed of the input shaft to reach the target rotation speed Look-ahead time but Based on the vehicle speed reached when hand Target rotation speed of the input shaft is set, and the target rotation speed but Upshift decision When the rotation speed is reached, The actual rotation speed of the input shaft corresponds to the next higher gear. Rotational speed become It is determined that an upshift is to be performed to change the speed ratio to the High side until the target rotation speed of the input shaft reaches the Upshift decision Once rotation speed is reached Rami Upshift when will be started to Before increasing to The input shaft increase Rotational speed and 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, Initiate an upshift.

[0010] According to another aspect of the present invention, a method for controlling a continuously variable transmission in which a stepwise stepped speed change control is performed by continuously changing a speed ratio between an input shaft and an output shaft includes the steps of: When step-by-step variable speed control is performed, the look-ahead time until the actual rotation speed of the input shaft reaches the target rotation speed is Based on the vehicle speed reached when hand Target rotation speed of the input shaft and set the target rotation speed but Upshift decision When the rotation speed is reached, The actual rotation speed of the input shaft corresponds to the next higher gear. Rotational speed become and determining that an upshift is to be performed to change the speed ratio to the High side until the target rotation speed of the input shaft reaches the Upshift decision Once rotation speed is reached Rami Upshift when will be started to Before increasing to The input shaft increase Rotational speed and 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, Initiate an upshift. [Effects of the Invention]

[0011] In the above aspect, after the target rotation speed of the input shaft reaches the first target rotation speed and it is determined that an upshift should be performed to the second target rotation speed, the upshift is initiated after the rotation speed has further increased. Therefore, even when the driver's request for acceleration is strong, the upshift can be performed when the engine rotation speed is high. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a continuously variable transmission according to an embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the process of the gear shift control performed by the transmission controller during acceleration. [Figure 3] FIG. 3 is a diagram conceptually illustrating the upshift determination rotation speed. [Figure 4] FIG. 4 is a timing chart illustrating the gear change control during acceleration. [Figure 5] FIG. 5 is a diagram conceptually explaining the predicted vehicle speed. [Figure 6] FIG. 6 is a flowchart showing the delay control based on the predicted vehicle speed, which is performed by the transmission controller. [Figure 7] FIG. 7 is a diagram conceptually illustrating delay control based on predicted vehicle speed. [Figure 8] 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 in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the following, a large gear ratio (reduction ratio) is referred to as "Low" and a small gear ratio (reduction ratio) is referred to as "High." Furthermore, a change in the gear ratio to the Low side is referred to as "downshift," and a change in the gear ratio to the High side is referred to as "upshift."

[0014] 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 FIG. 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.

[0015] 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 speed change mechanism, a hydraulic control circuit 5, and an oil pump 6.

[0016] In the vehicle 100, rotation generated by the engine 10 is transmitted to the drive wheels 50 via a power transmission path formed by the torque converter 2, the forward / reverse switching mechanism 3, the variator 4, the gear set 7, and the differential gear device 8.

[0017] The torque converter 2 is disposed downstream of the engine 10 in the power transmission path. The torque converter 2 is provided with a lock-up clutch 2a. When the lock-up clutch 2a is engaged, an input shaft 2b serving as an input element of the torque converter 2 and an output shaft 2c serving as an output element are directly connected, and the input shaft 2b and the output shaft 2c rotate at the same speed. Therefore, with the lock-up clutch 2a engaged, the rotation of the output shaft 10a of the engine 10 is transmitted as is from the output shaft 2c of the torque converter 2 to the forward / reverse switching mechanism 3.

[0018] The forward / reverse switching mechanism 3 has a double pinion planetary gear set as its main component, with its sun gear connected to the engine 10 via the torque converter 2 and its carrier connected to the input shaft 4d (primary pulley 4a) of the variator 4. The forward / reverse switching mechanism 3 also has 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, and when the forward clutch 3a is engaged, the input rotation from the engine 10 via the torque converter 2 is transmitted as is 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.

[0019] The variator 4 is disposed downstream of the engine 10 and the 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 rotation of the engine 10 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 a belt 4c as an endless member wound around the primary pulley 4a and secondary pulley 4b.

[0020] 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 sheave surfaces 4f, 4g of each of the pulleys 4a, 4b, and transmits power between the primary pulley 4a and the secondary pulley 4b.

[0021] The oil pump 6 is a mechanical oil pump that receives rotation of the engine 10 and is driven by using part of the power of the engine 10. The oil discharged from the oil pump 6 is supplied to the hydraulic control circuit 5.

[0022] 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 hydraulic pressure supplied to the reverse brake 3b, and a manual valve 5f that switches the hydraulic pressure supply paths to the forward clutch 3a and the reverse brake 3b.

[0023] The hydraulic control circuit 5 supplies adjusted hydraulic pressure to the torque converter 2, the forward / reverse switching mechanism 3, and the variator 4 based on a control signal from the transmission controller 40.

[0024] The engine controller 30 is configured with 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 configured with multiple microcomputers.

[0025] The engine controller 30 controls the rotation speed, torque, etc. of the engine 10 based on signals from various sensors that detect the state of each part of the vehicle 100.

[0026] The transmission controller 40 is configured as a microcomputer equipped with a CPU, RAM, ROM, input / output interface, etc., and is connected to the engine controller 30 so as to be able to 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 configured as a plurality of microcomputers. The transmission controller 40 and the engine controller 30 may also be integrated into a single controller.

[0027] 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 the reverse brake 3b, etc. based on signals from various sensors that detect the state of each part of the vehicle 100.

[0028] The transmission controller 40 receives inputs such as a signal from an accelerator pedal opening sensor 61 that detects an accelerator pedal opening APO, a signal from a brake fluid pressure sensor 62 that detects a 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 oil pressure sensor 68 that detects the primary oil pressure Pp supplied to the primary pulley 4a, and a signal from a secondary oil pressure sensor 69 that detects the secondary oil pressure Ps supplied to the secondary pulley 4b.

[0029] Next, the processing of the gear shift control during acceleration performed by the transmission controller 40 will be described with reference to Figures 2 to 4. The processing of the gear shift control is executed by the transmission controller 40 at regular time intervals.

[0030] First, the processing of the gear shift control during acceleration performed by the transmission controller 40 will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing the processing of the gear shift control during acceleration performed by the transmission controller 40. Figure 3 is a diagram conceptually showing the upshift determination rotation speed.

[0031] The speed change control during acceleration is executed when the driver's request for acceleration is large, for example, when the driver depresses the accelerator pedal to fully accelerate the vehicle 100. Here, the continuously variable transmission 20 is a continuously variable transmission that performs stepped speed change control like a stepped transmission.

[0032] In the torque converter 2, when the lockup clutch 2a is engaged, 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, in the torque converter 2, when the lockup clutch 2a is not engaged, the rotational speed of the input shaft 2b is higher than the rotational speed of the output shaft 2c. In the continuously variable transmission 20, an upshift decision is made based on the rotational speed of the input shaft 4d, but when the lockup clutch 2a is not engaged, an upshift decision is made with a margin corresponding to the difference in rotational speed between the input shaft 2b and the output shaft 2c in order to prevent an excessive increase in the rotational speed of the engine 10.

[0033] 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. That is, the difference in rotational speed between the input shaft 2b and the output shaft 2c changes depending on the engagement level of the lockup clutch 2a. Therefore, if an upshift is performed with a margin corresponding 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 in the case when the lockup clutch 2a is disengaged, there is a risk that the upshift will occur while the rotational speed of the engine 10 is still low, even though the rotational speed of the engine 10 could be increased. Therefore, the continuously variable transmission 20 performs gear shift control during acceleration as follows, taking into account the engagement level of the lockup clutch 2a.

[0034] 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.

[0035] In step S12 , the transmission controller 40 detects the output torque of the engine 10 based on a signal from the engine controller 30 .

[0036] In step S13, the controller 10 calculates the excess slip rotation speed of the torque converter 2 that may occur in the future. The excess slip rotation speed is calculated based on the difference between the current output torque and the maximum torque of the engine 10 (reserved output torque) and the fluid characteristics of the torque converter 2.

[0037] Specifically, the greater the difference between the current output torque and the maximum torque of the engine 10, the greater the possibility that the slip rotation speed of the torque converter 2 will be when the accelerator pedal is further depressed. That is, the greater the current output torque of the engine 10, the smaller the difference from the maximum torque, and therefore the smaller the slip rotation speed of the torque converter 2 that may be generated when the accelerator pedal is further depressed. Therefore, the excess slip rotation speed is set to be smaller as the current output torque of the engine 10 is greater.

[0038] 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).

[0039] Specifically, as shown in Fig. 3, the rotation speed of the engine 10 is higher than the rotation speed of the primary pulley 4a (PRI rotation speed) by the amount of the current actual slip rotation speed. Therefore, the upshift determination rotation speed is determined 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. Note that the LU upper limit PRI rotation speed is set lower than the maximum rotation speed of the engine 10 to prevent an excessive increase in the rotation speed of the engine 10.

[0040] With the lockup clutch 2a engaged, both the actual slip rotation speed and the excess slip rotation speed are 0. Therefore, the upshift determination rotation speed is the same as the LU upper limit PRI rotation speed.

[0041] Returning to Fig. 2, in step S15, 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, that is, 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.

[0042] 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 the upshift until the PRI rotation speed reaches a rotation speed corresponding to the next higher gear.

[0043] Next, the gear shift control performed by the transmission controller 40 during acceleration will be specifically described with reference to Fig. 4. Fig. 4 is a timing chart illustrating the gear shift control during acceleration.

[0044] In FIG. 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).

[0045] The target PRI rotation speed in the comparative example represents a case where upshift determination is performed using two threshold values, one for when the lockup clutch 2a is engaged and one for when it is not engaged, without applying this embodiment. Specifically, when the lockup clutch 2a is engaged, the lockup upper limit primary pulley rotation speed (LU upper limit PRI rotation speed) is used as the threshold, and when the lockup clutch 2a is not engaged, the unlockup upper limit primary pulley rotation speed (UnLU upper limit PRI rotation speed) is used as the threshold.

[0046] 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.

[0047] In this way, in the automatic transmission according to the comparative example, an upshift is determined and an upshift is performed before the rotation speed of the engine 10 becomes sufficiently high, and therefore the engine 10 cannot be used at high rotation speeds.

[0048] 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 lockup clutch 2a is engaged.

[0049] 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 lockup 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 excess slip rotation speed of the torque converter 2 that may occur in the future. 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 become sufficiently high at time T22. This allows the engine 10 to be used at higher rotation speeds.

[0050] At time T23, the rotation speed of the engine 10 has decreased to the rotation speed when the gear ratio is changed to the next higher gear in the stepped transmission control, and from this point the rotation speed of the engine 10 begins to increase again.

[0051] 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 about to be fully engaged. Therefore, the actual slip rotation speed and the excess slip rotation speed of the torque converter 2 that may occur from this point onward 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.

[0052] At time T26, the rotation speed of the engine 10 has decreased to the rotation speed when the gear ratio is changed to the next higher gear in the stepped transmission control, and from this point the rotation speed of the engine 10 begins to increase again.

[0053] 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 performs an upshift determination. At this time, the lockup clutch 2a is fully engaged. Therefore, the upshift determination rotation speed coincides with the LU upper limit PRI rotation speed.

[0054] As described above, in continuously variable transmission 20, when lockup clutch 2a is engaged, an upshift begins when the rotational speed of input shaft 2b reaches a first rotational speed, and when lockup clutch 2a is disengaged or slipping, an upshift begins when the rotational speed of input shaft 2b reaches a second rotational speed, which is the first rotational speed minus a first predetermined rotational speed. At this time, the first predetermined rotational speed is set smaller the greater the output torque of engine 10. Specifically, the first predetermined rotational speed is the sum of the actual slip rotational speed of lockup clutch 2a and the excess slip rotational speed of lockup clutch 2a that may occur before an upshift begins.

[0055] When the output torque of the engine 10 is large, the sum (first predetermined rotation speed) of the current actual slip rotation speed and the excess slip rotation speed of the torque converter 2 that may occur in the future is set to a small value. Therefore, an upshift is performed when the rotation speed of the engine 10 is higher, so that a gear change can be performed after the rotation speed of the engine 10 has been increased to a level that meets the driver's acceleration request. Therefore, when the driver's acceleration request is large, an upshift can be performed when the rotation speed of the engine 10 is high. Therefore, a gear change can be performed in line with the driver's intention. Furthermore, in this case, because the difference from the maximum torque of the engine 10 is small, an excessive increase in the rotation speed of the engine 10 can be suppressed even if the output torque of the engine 10 increases before the upshift.

[0056] On the other hand, when the output torque of the engine 10 is small, compared to when the output torque is large, there may be a deviation from the maximum torque of the engine 10. In such a state, the output torque of the engine 10 may become large before an upshift is performed, and the rotational speed of the engine 10 may exceed the rotational speed at which the upshift should be performed.

[0057] In contrast, in the continuously variable transmission 20, when the output torque of the engine 10 is small, the upshift is performed at a correspondingly lower rotational speed of the engine 10, so that the timing of the upshift is delayed, thereby preventing the rotational speed of the engine 10 from increasing excessively.

[0058] Furthermore, even if the lock-up clutch 2a is slipping, an upshift is initiated when the second rotation speed is reached, which is calculated by subtracting the actual slip rotation speed and the excess slip rotation speed that may occur before the upshift is initiated, from the first rotation speed. Thus, an excessive increase in the rotation speed of the engine 10 is prevented, and an upshift can be performed at a high rotation speed when the engine 10 is running with close to maximum torque. Therefore, gear changes can be performed in line with the driver's intentions.

[0059] The variator 4 is also a continuously variable transmission mechanism that continuously changes the gear ratio between the input shaft 2b and the output shaft 4e, and when the lock-up clutch 2a is engaged, it upshifts to a third rotational speed when the rotational speed of the input shaft 2b reaches a first rotational speed, and when the lock-up clutch 2a is released or slipping, it upshifts to a third rotational speed when the rotational speed of the input shaft 2b reaches a second rotational speed, until it reaches the third rotational speed.

[0060] As a result, even when the gear shift control during acceleration according to this embodiment is applied to a continuously variable transmission in which stepwise gear shift control is performed like a stepped transmission, if the driver requests a large amount of acceleration, upshifting can be performed while the rotation speed of the engine 10 is high. Therefore, gear shifting can be performed in line with the driver's intentions.

[0061] 5 to 8, a description will be given of 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 time intervals.

[0062] First, the delay control based on the predicted vehicle speed performed by the transmission controller 40 will be described with reference to Fig. 5 to Fig. 7. Fig. 5 is a diagram conceptually explaining the predicted vehicle speed. Fig. 6 is a diagram showing, in the form of a flowchart, the delay control based on the predicted vehicle speed performed by the transmission controller 40. Fig. 7 is a diagram conceptually explaining the delay control based on the predicted vehicle speed.

[0063] As shown in Fig. 5, in continuously variable transmission 20, when an upshift determination is made and an upshift actually starts, the PRI rotation speed gradually increases and then decreases toward the target PRI rotation speed after the upshift. Therefore, in continuously variable transmission 20, to prevent the rotation speed of engine 10 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 [sec].

[0064] In this case, if an upshift is initiated when the target PRI rotation speed reaches the upshift determination rotation speed, the upshift is initiated while the PRI rotation speed is still low, and there is a risk that the PRI rotation speed after the look-ahead time will not reach the upshift determination rotation speed. In other words, even if the driver's acceleration request is strong, an upshift may not be possible when the rotation speed of the engine 10 is high. Therefore, the continuously variable transmission 20 takes the look-ahead vehicle speed into consideration and performs gear change control during acceleration as follows.

[0065] In step S21 of Fig. 6, the transmission controller 40 determines whether or not an upshift determination has been made. If it is determined in step S21 that an upshift determination has been made, the process proceeds to step S22. The process of step S21 returns "Yes" if an upshift determination has been made in step S16 of Fig. 2. On the other hand, if it is determined in step S21 that an upshift determination has not been made, the process of step S21 is repeated.

[0066] In step S22, the transmission controller 40 detects the PRI rotation speed based on the signal from the primary rotation speed sensor 66.

[0067] 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.

[0068] 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, that is, is lower than the upshift determination rotation speed at the time of upshift determination, the processing from step S22 to step 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.

[0069] Here, the delay control will be specifically described with reference to FIG.

[0070] At time T1, an upshift is determined, and the target gear ratio of continuously variable transmission 20 is changed from R1 to R2. Here, when an upshift is performed at time T1, transmission controller 40 calculates an increased rotation speed ΔS1 that increases during the upshift.

[0071] 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 starts 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-related increased rotation speed Sa, which has increased from time T1 when it was determined that the upshift would be performed to time T2 when the upshift is started, corresponds to the predetermined rotation speed. The delay-related increased rotation speed ΔSa is set based on the PRI rotation speed that increases from the time when 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 large, an upshift can be performed when the rotation speed of the engine 10 is even higher.

[0072] 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, when an upshift is performed at time T3, the transmission controller 40 calculates an increased rotation speed ΔS3 that increases during the upshift.

[0073] 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 starts 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-related increased rotation speed Sb, which has increased from time T3 when it was determined that the upshift would be performed to time T4 when the upshift is initiated, corresponds to the predetermined rotation speed. The delay-related increased rotation speed ΔSb is also set based on the PRI rotation speed that increases from the time when 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 large, an upshift can be performed when the rotation speed of the engine 10 is even higher.

[0074] 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 a rotation speed corresponding to the next higher gear (second target rotation speed).

[0075] Next, the gear shift control during acceleration performed by the transmission controller 40 will be specifically described with reference to Fig. 8. Fig. 8 is a timing chart illustrating a case where delay control based on predicted vehicle speed is further applied to the gear shift control during acceleration shown in Fig. 4.

[0076] 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) [rpm] of the comparative example, target gear ratio (dashed line), and actual gear ratio (solid line).

[0077] The PRI rotation speed of the comparative example is the rotation speed of the engine 10 shown in FIG. 4 to which delay control based on the predicted vehicle speed is not applied.

[0078] At time T31, the target PRI rotation speed reaches the upshift determination rotation speed, so transmission controller 40 performs an upshift determination. The upshift determination is similar to that at time T21 in Figure 4, so a detailed description will be omitted here.

[0079] In the continuously variable transmission according to the comparative example, an upshift is initiated at time T31, and the rotation speed of the engine 10 reaches a maximum value during the gear shift at time T32. The PRI rotation speed and the rotation speed of the engine 10 then decrease until the gear shift is performed to the next higher gear.

[0080] In contrast, when delay control based on the predicted vehicle speed is applied, the execution of the upshift is delayed, and the rotation speed of the engine 10 reaches the maximum value during the shift at time T33, which is later than time T32. At this time, 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.

[0081] 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.

[0082] At time T36, the target PRI rotation speed 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 T37 the rotation speed of the engine 10 reaches the 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 rotation speed of the engine 10 has reached the LU upper limit PRI rotation speed.

[0083] 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 starts an upshift after the PRI rotation speed has increased by the increased rotation speed (predetermined rotation speed) by the delay amount after the target PRI rotation speed reaches the upshift determination rotation speed (first target rotation speed).

[0084] As a result, after 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 request for acceleration is strong, an upshift can be performed while the rotation speed of the engine 10 is high. Therefore, gear changes can be performed in line with the driver's intentions.

[0085] The delay increase rotation speed is set based on the PRI rotation speed of the primary pulley 4a (input shaft 4d) that increases from when the target PRI rotation speed reaches the upshift determination rotation speed until an upshift is actually performed.

[0086] This makes it possible to prevent the rotation speed of the engine 10 from becoming too high even if the rotation speed of the engine 10 is set high when an upshift is initiated.

[0087] In the above embodiment, when the target PRI rotation speed, which is set based on the vehicle speed to be reached when 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 started after the PRI rotation speed has increased by the increased rotation speed corresponding to the delay after reaching the upshift determination rotation speed.

[0088] 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.

[0089] Similarly, in this case, after 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 rotation speed of the engine 10 is high. Therefore, gear changes can be performed in line with the driver's intentions.

[0090] The configuration and effects of the present embodiment will now be described.

[0091] (1)(5) The continuously variable transmission 20, which changes the speed ratio of the input shaft 4d and the output shaft 4e steplessly, 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 to be 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 target PRI rotation speed reaches the upshift determination rotation speed (first target rotation speed) and the PRI rotation speed has increased by the delay-amount increased rotation speed (predetermined rotation speed).

[0092] According to this configuration, after 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 request for acceleration is strong, an upshift can be performed while the rotation speed of the engine 10 is high. Therefore, gear changes can be performed in line with the driver's intentions.

[0093] (2) The delay-amount increased 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 upshift is actually performed.

[0094] According to this configuration, even if the rotation speed of the engine 10 at the start of an upshift is set high, it is possible to prevent the rotation speed of the engine 10 from becoming too high.

[0095] (3)(6) The continuously variable transmission 20, which changes the gear ratio of the input shaft 4d and the output shaft 4e steplessly, 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 to be reached when the look-ahead time (first predetermined time) has elapsed, reaches the upshift determination rotation speed (first target rotation speed), and starts upshifting after the second predetermined time has elapsed since the PRI rotation speed reached the upshift determination rotation speed.

[0096] According to this configuration, after 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 requests a large amount of acceleration, an upshift can be performed while the rotation speed of the engine 10 is high. Therefore, a gear change can be performed in accordance with the driver's intention.

[0097] (4) The second predetermined time is set based on the PRI rotation speed of the primary pulley 4a (input shaft 4d) that increases from when the target PRI rotation speed reaches the upshift determination rotation speed until an upshift is actually performed.

[0098] According to this configuration, even if the rotation speed of the engine 10 at the start of an upshift is set high, it is possible to prevent the rotation speed of the engine 10 from becoming too high.

[0099] Although an embodiment of the present invention has been described above, the above embodiment merely shows 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.

[0100] For example, in the above embodiment, the continuously variable transmission 20 is described as a continuously variable transmission that performs stepwise step-variable speed change control like a stepped transmission. However, the present invention can also be applied to a continuously variable transmission in which the driver can manually operate step-variable speed change, 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. [Explanation of symbols]

[0101] 20 Continuously variable transmission 4d input shaft 4e Output shaft

Claims

1. 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.

2. 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.

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