Continuously variable transmission, control method and program for continuously variable transmission

Abstract

The continuously variable transmission of the present invention suppresses the execution of speed shift control that is contrary to the driver's intention when the accelerator opening decreases. The continuously variable transmission, mounted on a vehicle, performs an upshift in accordance with the accelerator opening until the accelerator opening reaches a predetermined opening when the accelerator opening decreases while the vehicle is traveling. When the accelerator opening decreases below the predetermined opening, the transmission further upshifts from the speed ratio corresponding to the predetermined accelerator opening. The speed ratio is fixed to a higher gear than the speed ratio corresponding to the predetermined accelerator opening. Thereafter, further upshifts are performed from the fixed speed ratio in accordance with the accelerator opening.

Description

Technical Field

[0001] The present invention relates to a continuously variable transmission, a control method for the continuously variable transmission, and a program. Background Art

[0002] Patent document 1 discloses the following speed control: when the accelerator pedal is returned, when the intention is to stabilize driving, the speed ratio of the continuously variable transmission is shifted up to gradually reduce the input speed to a target speed calculated based on the accelerator pedal operation amount or vehicle speed after the accelerator pedal is returned; when the intention to decelerate is determined, the speed ratio of the continuously variable transmission is shifted up to a fixed speed ratio that is smaller than the previous speed ratio; thereafter, the speed ratio is fixed to the fixed speed ratio.

[0003] Thus, when a deceleration intention is determined, the engine speed is reduced by the amount of the upshift compared to when the gear ratio prior to the accelerator release operation is maintained, suppressing the reduction in engine braking and thus generating a deceleration G exceeding the driver's intention. Furthermore, the reduction in engine speed caused by the upshift generates inertia in the driving direction, which mitigates (offsets) the engine braking and suppresses the shock.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-225417

[0007] Problems to be solved by the invention

[0008] However, in the aforementioned speed shift control, when the accelerator is released (when the accelerator opening is reduced), there are only two speed shift patterns corresponding to steady driving and deceleration. This creates the possibility of executing speed shift control that contradicts the driver's intention. Specifically, the driver might consider releasing the accelerator with the intention of deceleration, but the engine speed may drop excessively, or releasing the accelerator with the intention of steady driving, but the engine speed may not drop at all. In such cases, subsequent driver manipulations could result in the vehicle's dynamic performance not being as expected. Summary of the Invention

[0009] The present invention has been made in view of such technical problems, and an object of the present invention is to suppress execution of a speed change control that is contrary to the driver's intention when the accelerator opening degree becomes smaller.

[0010] According to one embodiment of the present invention, a continuously variable transmission is provided, which is a continuously variable transmission installed on a vehicle, wherein, when the accelerator opening becomes smaller while the vehicle is traveling, the continuously variable transmission has the following processing: a first processing, when the speed at which the accelerator opening becomes smaller is higher than a specified speed, before reaching the specified opening, an upshift is performed corresponding to (based on) the accelerator opening, and the speed ratio is fixed at the speed ratio when the accelerator opening is the specified opening; a second processing, when the speed at which the accelerator opening becomes smaller is lower than the specified speed and the turbine speed is higher than the specified speed, before reaching the specified opening, an upshift is performed corresponding to (based on) the accelerator opening. The gear ratio is adjusted from 0.01 to 0.05, and the gear ratio is adjusted from 0.01 to 0.05. The gear ratio is adjusted from 0.01 to 0.05, and the gear ratio is adjusted from 0.01 to 0.05. The gear ratio is adjusted from 0.01 to 0.05, and the gear ratio is adjusted from 0.01 to 0.05. The gear ratio is adjusted from 0.01 to 0.05, and the gear ratio is adjusted from 0.01 to 0.05.

[0011] Effects of the Invention

[0012] In the above embodiment, a second process is added to the first and third processes. The first process involves performing an upshift according to the accelerator opening until the accelerator opening reaches a predetermined value, fixing the gear ratio at the gear ratio at the predetermined accelerator opening to maintain the engine speed high. The third process involves performing an upshift according to the accelerator opening until the predetermined value is reached, and further performing an upshift according to the accelerator opening when the accelerator opening becomes smaller than the predetermined value, thereby reducing the engine speed. The second process involves performing an upshift according to the accelerator opening until the predetermined value is reached, and further performing an upshift from the gear ratio at the predetermined accelerator opening when the accelerator opening becomes smaller than the predetermined value, fixing the gear ratio at a higher gear than the gear ratio at the predetermined accelerator opening. This prevents the engine speed from being excessively high or low relative to the driver's intention. Specifically, when the accelerator opening decreases, it prevents the execution of speed control that violates the driver's intention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of a vehicle equipped with an automatic transmission according to an embodiment of the present invention.

[0014] Figure 2 This is a flowchart of the determination process.

[0015] Figure 3 This is a flowchart of the first process.

[0016] Figure 4 This is a flowchart of the second process.

[0017] Figure 5 This is a flowchart of the third process.

[0018] Figure 6 This is an example of a sequence diagram when the first process is executed.

[0019] Figure 7 This is an example of a sequence diagram when the second process is executed.

[0020] Figure 8 This is an example of a sequence diagram when the third process is executed. DETAILED DESCRIPTION

[0021] The following describes embodiments of the present invention with reference to the accompanying drawings. Hereinafter, a large speed ratio is referred to as a low gear (Low), and a small speed ratio is referred to as a high gear (High). Furthermore, changing the speed ratio toward a low gear is referred to as a downshift, and changing the speed ratio toward a high gear is referred to as an upshift.

[0022] Figure 1 1 is a schematic structural diagram of a vehicle 100 equipped with an automatic transmission 20 as a continuously variable transmission according to an embodiment of the present invention. Figure 1 As shown, vehicle 100 includes an engine 10 as a driving source, an automatic transmission 20 , an engine controller 30 , and a transmission controller 40 .

[0023] The automatic transmission 20 includes a torque converter 2 , a forward / reverse switching mechanism 3 , a speed change mechanism 4 , a hydraulic control circuit 5 , and an oil pump 6 .

[0024] In vehicle 100 , rotation generated by engine 10 is transmitted to drive wheels 50 via torque converter 2 , forward / reverse switching mechanism 3 , speed change mechanism 4 , gear set 7 , and differential gear device 8 .

[0025] The torque converter 2 is equipped with a lockup clutch 2a. When the lockup clutch 2a is engaged, the input shaft 2b, serving as the input element of the torque converter 2, and the output shaft 2c, serving as the output element, are directly connected, with the input shaft 2b and the output shaft 2c rotating at the same speed. Therefore, when the lockup clutch 2a is engaged, the rotation of the output shaft 10a of the engine 10 is directly transmitted to the forward / reverse switching mechanism 3 via the output shaft 2c of the torque converter 2.

[0026] The forward-reverse switching mechanism 3 is primarily composed of a double-pinion planetary gear set, whose sun gear is coupled to the engine 10 via the torque converter 2, and whose planetary carrier is coupled to the input shaft 4d (primary pulley 4a) of the speed change mechanism 4. The forward-reverse switching mechanism 3 also includes a forward clutch 3a that directly connects the sun gear and the planetary carrier of the double-pinion planetary gear set, and a reverse brake 3b that secures the ring gear. When the forward clutch 3a is engaged, the input rotation from the engine 10 via the torque converter 2 is transmitted unchanged to the primary pulley 4a. When the reverse brake 3b is engaged, the input rotation from the engine 10 via the torque converter 2 is reversed, decelerated, and then transmitted to the primary pulley 4a.

[0027] The transmission mechanism 4 is a continuously variable transmission mechanism that changes the speed of the rotation of the engine 10 transmitted to the input shaft 4d and transmits the rotation from the output shaft 4e to the drive wheel 50. The transmission mechanism 4 includes a primary pulley 4a provided on the engine 10 side of the power transmission path; a secondary pulley 4b provided on the drive wheel 50 side; and a belt 4c, which is an endless member, wound around the primary pulley 4a and the secondary pulley 4b.

[0028] In the speed change mechanism 4 , the oil pressure supplied to the primary pulley 4 a and the oil pressure supplied to the secondary pulley 4 b are controlled to change the contact radius between the pulleys 4 a and 4 b and the belt 4 c , thereby changing the speed ratio.

[0029] The oil pump 6 is a mechanical oil pump that is input with the rotation of the engine 10 and is driven by a part of the power of the engine 10. The oil discharged from the oil pump 6 is supplied to the hydraulic control circuit 5.

[0030] The oil pressure control circuit 5 includes: a regulating valve 5a that adjusts the pressure of the working oil supplied from the oil pump 6 and generates the necessary oil pressure, a primary solenoid valve 5b that adjusts the oil pressure supplied to the primary pulley 4a, a secondary solenoid valve 5c that adjusts the oil pressure supplied to the secondary pulley 4b, a locking solenoid valve 5d that adjusts the oil pressure supplied to the locking clutch 2a, a selection solenoid valve 5e that adjusts the oil pressure supplied to the forward clutch 3a and the oil pressure supplied to the reverse brake 3b, a manual valve 5f that switches the supply path of the oil pressure to the forward clutch 3a and the reverse brake 3b, etc.

[0031] The hydraulic control circuit 5 supplies regulated hydraulic pressure to the torque converter 2 , the forward / reverse switching mechanism 3 , and the speed change mechanism 4 based on a control signal from the transmission controller 40 .

[0032] The engine controller 30 is composed of a microcomputer including a CPU, RAM, ROM, an input / output interface, etc. The engine controller 30 performs various processes by the CPU reading and executing programs stored in the ROM. The engine controller 30 may also be composed of a plurality of microcomputers.

[0033] The engine controller 30 controls the rotation speed, torque, and the like of the engine 10 based on signals from various sensors that detect the states of various parts of the vehicle 100 .

[0034] The transmission controller 40 is comprised of a microcomputer equipped with a CPU, RAM, ROM, and input / output interfaces, and is communicatively connected to the engine controller 30. The CPU reads and executes programs stored in the ROM to perform various processes. The transmission controller 40 may also be comprised of multiple microcomputers. Alternatively, the transmission controller 40 and the engine controller 30 may be combined into a single controller.

[0035] The transmission controller 40 controls the engagement state of the lockup clutch 2 a , the speed ratio of the speed change mechanism 4 , the engagement states of the forward clutch 3 a and the reverse brake 3 b , and the like based on signals from various sensors that detect the states of various parts of the vehicle 100 .

[0036] Input to the transmission controller 40 are: a signal from an accelerator opening sensor 61 that detects the accelerator opening APO, a signal from a brake hydraulic pressure sensor 62 that detects the brake hydraulic pressure BRP corresponding to the operation amount of the brake pedal, a signal from a circuit breaker 64 that detects the position of the shift device 63, a signal from a turbine speed sensor 65 that detects the rotational speed Nt of the output shaft 2c of the torque converter 2 (hereinafter referred to as the turbine speed Nt), a signal from a primary speed sensor 66 that detects the rotational speed Np (hereinafter referred to as the primary speed Np) of the input shaft 4d (primary pulley 4a) of the speed change mechanism 4, a signal from a secondary speed sensor 67 that detects the rotational speed Ns of the output shaft 4e (secondary pulley 4b) of the speed change mechanism 4, a signal from a primary oil pressure sensor 68 that detects the primary oil pressure Pp supplied to the primary pulley 4a, a signal from a secondary oil pressure sensor 69 that detects the secondary oil pressure Ps supplied to the secondary pulley 4b, etc.

[0037] Next, the speed change control executed by the transmission controller 40 will be described.

[0038] As described above, the transmission controller 40 controls the speed ratio of the speed change mechanism 4. The speed change control executed by the transmission controller 40 is varied and is selected according to the situation of the vehicle 100.

[0039] Examples of the speed shift control include normal speed shift control executed when the vehicle 100 is assumed to be traveling normally, and linear speed shift control executed when the driver is assumed to desire sporty driving. Each speed shift control is executed using a speed shift map that is pre-set based on various factors of the vehicle 100, experiments, and the like.

[0040] In the linear speed change control, the vehicle 100 is accelerated while suppressing a change in the speed ratio, so the driver can experience a sporty driving feeling.

[0041] Here, if we examine the situation where the accelerator pedal is returned during the execution of linear speed change control, for example, the situation where the accelerator pedal is returned with the intention of decelerating the vehicle 100 before entering a curve, and the situation where the driver returns the accelerator pedal with the intention of ending sport driving.

[0042] In the case of a temporary accelerator return operation accompanying a curve entry, maintaining the speed ratio at or near the speed ratio before the accelerator return operation in preparation for subsequent re-acceleration can be said to be consistent with the driver's intention. On the other hand, in the case of an accelerator return operation intended to terminate sport driving, maintaining the speed ratio at or near the speed ratio before the accelerator return operation may not be consistent with the driver's intention.

[0043] If the accelerator is returned during the execution of the linear speed change control, the speed change control that goes against the driver's intention may cause discomfort to the driver. Figure 2 The processes (first process, second process, third process) determined by the determination process shown are used to suppress execution of the speed change control that goes against the driver's intention.

[0044] Below, refer to Figure 2 The determination process will be described. Figure 2 This is a flowchart of the judgment process.

[0045] The determination process is executed when the accelerator is returned while the vehicle 100 is traveling and the linear shift control is being executed, that is, when the accelerator opening APO becomes smaller.

[0046] In step S11 , the transmission controller 40 determines whether or not the speed dAPO [deg / sec] at which the accelerator opening APO decreases is higher than a predetermined speed dAPOs.

[0047] The higher the speed dAPO, the faster the driver's maneuvering, and the more likely it is that the driver intends to continue sporty driving. The predetermined speed dAPOs is the threshold at which the driver is deemed to intend to continue sporty driving when the speed dAPO exceeds the predetermined speed dAPOs. The predetermined speed dAPOs is preset based on various parameters of vehicle 100, experiments, and the like.

[0048] If the transmission controller 40 determines that the speed dAPO is higher than the predetermined speed dAPOs, the process proceeds to step S12. If the transmission controller 40 determines that the speed dAPO is not higher than the predetermined speed dAPOs, the process proceeds to step S13.

[0049] In step S12, the transmission controller 40 determines to execute the first process. Figure 3 The first process will be described in detail.

[0050] In step S13, the transmission controller 40 determines whether the turbine speed Nt is higher than the predetermined speed Nts. During forward travel of the vehicle 100, the lockup clutch 2a and the forward clutch 3a are engaged, so the turbine speed Nt, the primary speed Np, and the engine speed are equal.

[0051] The higher the turbine speed Nt (=engine speed), the more likely the driver intends to engage in sporty driving. The predetermined speed Nts is a threshold at which the driver is considered likely to intend to continue sporty driving, even when the speed dAPO is not higher than the predetermined speed dAPOs. The predetermined speed Nts is set in advance based on various factors of vehicle 100, experiments, and the like.

[0052] If the transmission controller 40 determines that the turbine rotation speed Nt is higher than the predetermined rotation speed Nts, the process proceeds to step S14. If the transmission controller 40 determines that the turbine rotation speed Nt is not higher than the predetermined rotation speed Nts, the process proceeds to step S15.

[0053] In step S14, the transmission controller 40 determines to execute the second process. Figure 4 The second process will be described in detail.

[0054] In step S15, the transmission controller 40 determines to execute the third process. Figure 5 The third process will be described in detail.

[0055] Next, refer to Figure 3 The first process will be described. Figure 3 This is a flowchart of the first process. If it is determined in the determination process that the first process is to be performed, the first process is executed.

[0056] In step S21, the transmission controller 40 executes an upshift based on the linear shift control. Specifically, the transmission controller 40 executes an upshift based on the accelerator opening APO using a shift map for the linear shift control.

[0057] In step S22 , the transmission controller 40 determines whether the accelerator opening APO is smaller than a predetermined opening APOs.

[0058] If the transmission controller 40 determines that the accelerator opening APO is smaller than the predetermined opening APOs, the process proceeds to step S23. If the transmission controller 40 determines that the accelerator opening APO is not smaller than the predetermined opening APOs, the process returns to step S21 and continues upshifting by the linear shift control.

[0059] When the accelerator return operation amount is small, the driver may make a minor adjustment to the accelerator opening APO. In other words, the driver may immediately step on the accelerator. The predetermined opening APOs is a threshold value at which the driver's intention is met by continuing the linear shift control in preparation for the driver's imminent accelerator stepping. The predetermined opening APOs is preset based on various factors of vehicle 100, experiments, and the like.

[0060] In addition, when the accelerator opening APO increases before entering step S23, the transmission controller 40 ends the first process and executes the gear shifting based on the linear gear shifting control according to the accelerator opening APO.

[0061] In step S23 , the transmission controller 40 fixes the speed ratio of the speed change mechanism 4 to the speed ratio when the accelerator opening APO reaches the predetermined opening APOs.

[0062] As a result, the engine speed is maintained in a speed range where a sporty acceleration feeling can be obtained when the driver steps on the accelerator. In other words, a speed change control that meets the driver's desire for sporty driving is achieved.

[0063] In step S24, the transmission controller 40 determines whether the accelerator opening APO is increasing.

[0064] If the transmission controller 40 determines that the accelerator opening APO has increased, the process proceeds to step S25. If the transmission controller 40 determines that the accelerator opening APO has not increased, the process proceeds to step S26.

[0065] In step S25 , the transmission controller 40 executes a gear shift based on the normal gear shift control according to the accelerator opening APO.

[0066] Thus, when the driver steps on the accelerator more heavily, a downshift is executed starting from the speed ratio fixed in step S23 to increase the engine speed. On the other hand, when the driver steps on the accelerator less heavily, an upshift is executed starting from the speed ratio fixed in step S23 to reduce the engine speed.

[0067] In step S26, the transmission controller 40 determines whether a first predetermined time has elapsed since the speed ratio was fixed in step S23. The first predetermined time is set in advance based on various factors of the vehicle 100, experiments, and the like.

[0068] If the transmission controller 40 determines that the first predetermined time has elapsed, the process proceeds to step S25. If the transmission controller 40 determines that the first predetermined time has not elapsed, the process returns to step S24.

[0069] Thus, when the first predetermined time has elapsed without the driver stepping on the accelerator, a shift is executed under normal shift control. That is, an upshift is executed along the coasting line in the shift map of normal shift control, starting from the speed ratio fixed in step S23.

[0070] In this way, when the driver does not step on the accelerator, the vehicle is shifted to coasting travel using normal speed change control, thereby suppressing fuel consumption.

[0071] Next, refer to Figure 4 The second process will be described. Figure 4 This is a flowchart of the second process. If it is determined in the determination process that the second process is to be performed, the second process is executed.

[0072] The processes of step S31 and step S32 in the second process are the same as the processes of step S21 and step S22 in the first process.

[0073] In step S33 , the transmission controller 40 performs an upshift to a predetermined speed ratio, starting from the speed ratio when the accelerator opening APO reaches the predetermined opening APOs.

[0074] In addition, when the accelerator opening APO increases before entering step S34, the transmission controller 40 ends the second process and executes the gear shifting based on the linear gear shifting control according to the accelerator opening APO.

[0075] In step S34, the transmission controller 40 fixes the speed ratio to a predetermined speed ratio. Specifically, the transmission controller 40 fixes the speed ratio to a higher gear than the speed ratio when the accelerator opening APO is the predetermined opening APOs.

[0076] As described above, the second process is executed when it is determined that the driver intends to continue sport driving. Therefore, the predetermined speed ratio may be, for example, a speed ratio intermediate between the speed ratio when the accelerator opening APO reaches the predetermined opening APOs and the speed ratio determined by the coasting line in the shift map for normal shift control.

[0077] Thus, the engine speed is maintained in a speed region where a certain degree of acceleration can be obtained when the driver steps on the accelerator. In addition, even if the driver intends to end sports driving, by maintaining the engine speed reduced to a state of about half, it is possible to suppress the driver from feeling uncomfortable.

[0078] In order to achieve this effect, it is preferable that the difference between the engine speed when the accelerator opening APO reaches the predetermined opening APOs and the engine speed during coasting is greater than or equal to a predetermined value. The predetermined value is, for example, 1000 rpm. The predetermined value is taken into consideration when setting the predetermined speed Nts in the determination process.

[0079] However, this effect can also be achieved by fixing the speed ratio slightly higher than the speed ratio when the accelerator opening APO reaches the predetermined opening APOs. That is, the predetermined speed ratio is not limited to the above. The predetermined speed ratio can be determined using, for example, a dedicated speed map pre-set based on various factors of vehicle 100 or experimental results.

[0080] The processing of step S35 and step S36 is the same as the processing of step S24 and step S25 in the first process.

[0081] Thus, when the driver steps on the accelerator more heavily, a downshift is executed starting from the speed ratio fixed in step S34 to increase the engine speed. On the other hand, when the driver steps on the accelerator less heavily, an upshift is executed starting from the speed ratio fixed in step S34 to reduce the engine speed.

[0082] In step S37, the transmission controller 40 determines whether a second predetermined time has elapsed after the speed ratio was fixed in step S34. The second predetermined time is set in advance based on various factors of the vehicle 100, experiments, and the like.

[0083] If the transmission controller 40 determines that the second predetermined time has elapsed, the process proceeds to step S36. If the transmission controller 40 determines that the second predetermined time has not elapsed, the process returns to step S35.

[0084] Thus, if the second predetermined time has elapsed without the driver stepping on the accelerator, a gear shift is executed under normal gear shift control. Specifically, starting from the gear ratio fixed in step S34, an upshift is executed along the coasting line in the gear shift map for normal gear shift control. The second predetermined time may be the same as the first predetermined time.

[0085] In this way, when the driver does not step on the accelerator, the vehicle is shifted to coasting travel using normal speed change control, thereby suppressing fuel consumption.

[0086] Next, refer to Figure 5 The third process will be described. Figure 5 This is a flowchart of the third process. If it is determined in the determination process that the third process is to be performed, the third process is executed.

[0087] The processes of step S41 and step S42 in the third process are the same as the processes of step S21 and step S22 in the first process.

[0088] In addition, when the accelerator opening APO increases before entering step S43, the transmission controller 40 ends the third process and executes the gear shifting based on the linear gear shifting control according to the accelerator opening APO.

[0089] In step S43 , the transmission controller 40 executes a gear shift based on the normal gear shift control according to the accelerator opening APO.

[0090] As described above, the third process is executed when the speed dAPO is not higher than the predetermined speed dAPOs and the turbine rotation speed Nt is not higher than the predetermined rotation speed Nts.

[0091] In this case, it's highly likely that the driver didn't intend to engage in sport driving. Furthermore, even if the gear ratio is upshifted from the one at which the accelerator opening APO reaches the predetermined opening APOs and the gear ratio is fixed, as in the second process, the engine speed will decrease and become unstable. Therefore, in the third process, when the accelerator opening APO becomes smaller than the predetermined opening APOs, the system quickly transitions to normal gear shift control.

[0092] Next, refer to Figures 6 to 8 Next, a description will be given of the state of vehicle 100 when the accelerator return operation is performed during execution of the linear shift control. Figure 6 This is an example of a sequence diagram when the first process is executed. Figure 7 This is an example of a sequence diagram when the second process is executed. Figure 8 This is an example of a sequence diagram when the third process is executed.

[0093] First, refer to Figure 6 The following describes the case where the first process is executed. Figure 6 The target turbine speed TNt indicated by a dashed line shows the change in the target turbine speed TNt when the normal speed change control is executed after time t12 as a comparative example.

[0094] At time t11, the accelerator return operation is started, the accelerator opening APO decreases, and the speed dAPO at which the accelerator opening APO decreases becomes higher than a predetermined speed dAPOs.

[0095] Furthermore, the target turbine speed TNt is lowered in accordance with the accelerator opening APO, and the turbine speed Nt is lowered. That is, an upshift based on the linear speed change control is started.

[0096] At time t12, when the accelerator opening APO becomes smaller than the predetermined opening APOs, the linear speed change control ends and the speed ratio is fixed.

[0097] At time t13, the accelerator return operation is completed, and the accelerator opening APO reaches zero. In the first process, the speed ratio of the variator 4 is fixed at time t12, so the target turbine speed TNt decreases as the vehicle speed decreases. In contrast, in the comparative example, the target turbine speed TNt decreases in accordance with the accelerator opening APO from time t12 to time t13.

[0098] exist Figure 6 In the period from time t13 to time t15, the accelerator opening APO remains at zero. Therefore, after the turbine speed Nt matches the target turbine speed TNt at time t14, it decreases in accordance with the vehicle speed while matching the target turbine speed TNt until time t15 when the accelerator opening APO increases.

[0099] When the accelerator opening APO increases at time t15, the target turbine speed TNt decreases in accordance with the accelerator opening APO. That is, an upshift is executed based on the normal speed change control. Ultimately, the target turbine speed TNt matches the target turbine speed TNt of the comparative example.

[0100] Next, refer to Figure 7 The following describes the case where the second process is performed. Figure 7 The target turbine speed TNt indicated by a dashed line shows the change in the target turbine speed TNt when the normal speed change control is executed after time t22 as a comparative example.

[0101] At time t21, the accelerator return operation is started, and the accelerator opening APO decreases. Figure 7 In the example of FIG. 2 , at time t21 , the speed dAPO at which the accelerator opening APO decreases is lower than the predetermined speed dAPOs, and the turbine speed Nt is higher than the predetermined speed Nts.

[0102] Furthermore, the target turbine speed TNt is lowered in accordance with the accelerator opening APO, and the turbine speed Nt is lowered. That is, an upshift based on the linear speed change control is started.

[0103] At time t22, when the accelerator opening APO becomes smaller than the predetermined opening APOs, the linear shift control ends. Then, at time t23, the target turbine speed TNt further decreases. In other words, the speed ratio is further shifted up.

[0104] At time t23, the speed ratio is fixed to a predetermined speed ratio.

[0105] At time t24, the accelerator return operation is completed, and the accelerator opening APO reaches zero. In the second process, at time t23, the speed ratio of the variator 4 is fixed, so the target turbine speed TNt decreases as the vehicle speed decreases. In contrast, in the comparative example, from time t22 to time t24, the target turbine speed TNt decreases as the accelerator opening APO decreases.

[0106] exist Figure 7 After time t24, the accelerator opening APO remains at zero. Therefore, after the turbine speed Nt matches the target turbine speed TNt at time t25, it decreases according to the vehicle speed while matching the target turbine speed TNt until time t26 after the second predetermined time has passed.

[0107] At time t26, when the second predetermined time has elapsed, the target turbine speed TNt is reduced in accordance with the accelerator opening APO. That is, an upshift is executed by the normal speed change control.

[0108] exist Figure 7 In the example of , upshifts are performed along the coasting line in the shift map of the normal shift control. Ultimately, the target turbine speed TNt matches the target turbine speed TNt of the comparative example. As a result, the vehicle 100 enters the coasting state based on the normal shift control.

[0109] Next, refer to Figure 8 The following describes the case where the third process is executed. Figure 8 In the process, perform the accelerator return operation, and then continue to disconnect the accelerator.

[0110] At time t31, the accelerator return operation is started, and the accelerator opening APO decreases. Figure 8 In the example of FIG. 3 , at time t31 , the speed dAPO at which the accelerator opening APO decreases is lower than the predetermined speed dAPOs, and the turbine speed Nt is lower than the predetermined speed Nts.

[0111] Furthermore, the target turbine speed TNt is lowered in accordance with the accelerator opening APO, and the turbine speed Nt is lowered. That is, an upshift based on the linear speed change control is started.

[0112] At time t32, when the accelerator opening APO becomes smaller than the predetermined opening APOs, the linear speed change control ends.

[0113] Then, from time t32 to time t33, the target turbine speed TNt decreases in accordance with the accelerator opening APO. That is, an upshift is executed under the normal speed change control. As a result, the vehicle 100 enters the coasting state under the normal speed change control.

[0114] The main functions and effects of the automatic transmission 20 configured as described above will be summarized.

[0115] (1) The continuously variable transmission 20 mounted on the vehicle 100 has the following processing when the accelerator opening APO becomes smaller while the vehicle 100 is traveling: the first processing is when the speed dAPO at which the accelerator opening APO becomes smaller is higher than the prescribed speed dAPOs, before reaching the prescribed opening APOs, the gear is shifted up corresponding to the accelerator opening APO, and the gear ratio is fixed at the gear ratio when the accelerator opening APO is the prescribed opening APOs; the second processing is when the speed dAPO at which the accelerator opening APO becomes smaller is lower than the prescribed speed dAPOs, and the turbine speed Nt is higher than the prescribed speed Nts, before reaching the prescribed opening APOs, the gear is shifted up corresponding to the accelerator opening APO. APO is used to upshift, and when the accelerator opening APO becomes smaller than the specified opening APOs, a further upshift is performed from the speed ratio when the accelerator opening APO is the specified opening APOs, and the speed ratio is fixed to a higher gear side than the speed ratio when the accelerator opening APO is the specified opening APOs; the third processing, when the speed dAPO at which the accelerator opening APO decreases is below the specified speed dAPOs and the turbine speed Nt is below the specified speed Nts, before reaching the specified opening APOs, an upshift is performed corresponding to the accelerator opening APO, and when the accelerator opening APO becomes smaller than the specified opening APOs, a further upshift is performed corresponding to the accelerator opening APO.

[0116] Therefore, when the accelerator opening APO becomes smaller, the second process is added to the first process and the third process, wherein the first process performs an upshift according to the accelerator opening APO before reaching the specified opening APOs, and fixes the speed ratio at the speed ratio when the accelerator opening APO is the specified opening APOs, thereby maintaining the engine speed at a high state; the third process performs an upshift according to the accelerator opening APO before reaching the specified opening APOs, and when the accelerator opening APO becomes smaller than the specified opening APOs, A further upshift should be performed at the accelerator opening APO to reduce the engine speed. The second process involves performing an upshift in accordance with the accelerator opening APO until the predetermined opening APOs is reached. When the accelerator opening APO becomes smaller than the predetermined opening APOs, a further upshift is performed from the speed ratio corresponding to the predetermined opening APOs, fixing the speed ratio to a higher gear than the speed ratio corresponding to the predetermined opening APOs. This prevents the engine speed from being excessively high or low relative to the driver's intention. Specifically, when the accelerator opening APO decreases, execution of a speed change control that is contrary to the driver's intention can be suppressed.

[0117] (2)(4)(5) The automatic transmission 20 mounted on the vehicle 100, when the accelerator opening APO becomes smaller while the vehicle 100 is traveling, performs an upshift corresponding to the accelerator opening APO before reaching the prescribed opening APOs, and when the accelerator opening APO becomes smaller than the prescribed opening APOs, further performs an upshift from the speed ratio when the accelerator opening APO is the prescribed opening APOs, fixes the speed ratio to a higher gear side than the speed ratio when the accelerator opening APO is the prescribed opening APOs, and then further performs an upshift from the fixed speed ratio.

[0118] As a result, when the accelerator opening APO decreases, an upshift is performed according to the accelerator opening APO until the predetermined opening APOs is reached. When the accelerator opening APO decreases below the predetermined opening APOs, an upshift is performed from the speed ratio at the predetermined opening APOs, the speed ratio is fixed, and then an upshift is performed from the fixed speed ratio. This prevents situations where the engine speed is too low, the speed ratio is not fixed, or the speed ratio is fixed under undesirable conditions. In other words, when the accelerator opening APO decreases, execution of speed control that is contrary to the driver's intention can be suppressed.

[0119] (3) When the accelerator opening APO decreases while the vehicle 100 is traveling, and when the speed dAPO at which the accelerator opening APO decreases is higher than a prescribed speed dAPOs, the automatic transmission 20 shifts up according to the accelerator opening APO before reaching the prescribed opening APOs, and when the accelerator opening APO becomes smaller than the prescribed opening APOs, the gear ratio is fixed.

[0120] Thus, when the accelerator opening APO decreases, and if the speed dAPO at which the accelerator opening APO decreases is higher than a predetermined speed dAPOs, an upshift is performed according to the accelerator opening APO until the predetermined opening APOs is reached, and the speed ratio is fixed when the accelerator opening APO becomes smaller than the predetermined opening APOs. This allows for speed control that matches the driver's intention.

[0121] While the embodiments of the present invention have been described above, the above embodiments merely illustrate a part of application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above embodiments.

[0122] For example, in the above embodiment, the continuously variable transmission mechanism is described as the transmission mechanism 4. However, the continuously variable transmission mechanism may be another continuously variable transmission mechanism.

[0123] As various programs executed by the transmission controller 40 , programs stored in a non-transitory recording medium such as a CD-ROM can be used.

[0124] Explanation of symbols

[0125] 100: Vehicle

[0126] 20: Automatic transmission (continuously variable transmission)

[0127] 40: Transmission controller (computer)

Claims

1. A continuously variable transmission mounted on a vehicle, wherein: When the accelerator opening becomes smaller while the vehicle is running, the following processing is performed: In the first processing, when the speed at which the accelerator opening decreases is higher than a predetermined speed, an upshift is performed according to the accelerator opening before the predetermined opening is reached, and the speed ratio is fixed at the speed ratio when the accelerator opening is the predetermined opening. In the second process, when the speed at which the accelerator opening decreases is lower than the specified speed and the turbine speed is higher than the specified speed, an upshift is performed according to the accelerator opening before the specified opening is reached. When the accelerator opening becomes smaller than the specified opening, an upshift is further performed from the speed ratio when the accelerator opening is at the specified opening, and the speed ratio is fixed at a higher gear side than the speed ratio when the accelerator opening is at the specified opening. The third processing is to perform an upshift according to the accelerator opening before reaching the specified opening when the speed at which the accelerator opening decreases is lower than the specified speed and the turbine speed is lower than the specified speed. When the accelerator opening becomes smaller than the specified opening, a further upshift is performed according to the accelerator opening.

2. A continuously variable transmission, mounted on a vehicle, wherein: When the accelerator opening becomes smaller while the vehicle is running, Before reaching the specified opening, upshift is performed according to the accelerator opening. When the accelerator opening becomes smaller than the predetermined opening, an upshift is performed from the speed ratio when the accelerator opening is at the predetermined opening, and the speed ratio is fixed to a higher gear side than the speed ratio when the accelerator opening is at the predetermined opening. Thereafter, an upshift is further performed from the fixed speed ratio in accordance with the accelerator opening degree.

3. The continuously variable transmission according to claim 2, wherein: When the accelerator opening decreases while the vehicle is traveling, and when the speed at which the accelerator opening decreases is higher than a predetermined speed, Before reaching the specified opening, upshifting is performed according to the accelerator opening. When the accelerator opening becomes smaller than the predetermined opening, the speed ratio is fixed.

4. A method for controlling a continuously variable transmission, wherein the continuously variable transmission is mounted on a vehicle, When the accelerator opening becomes smaller while the vehicle is running, Before reaching the specified opening, upshift is performed according to the accelerator opening. When the accelerator opening becomes smaller than the predetermined opening, an upshift is performed from the speed ratio when the accelerator opening is at the predetermined opening, and the speed ratio is fixed to a higher gear side than the speed ratio when the accelerator opening is at the predetermined opening. Thereafter, an upshift is further performed from the fixed speed ratio in accordance with the accelerator opening degree.

5. A storage medium storing a program executable by a computer of a continuously variable transmission mounted on a vehicle, wherein: The program causes the computer to execute the following steps: When the accelerator opening becomes smaller while the vehicle is running, Before reaching a predetermined opening, performing an upshift corresponding to the accelerator opening; When the accelerator opening becomes smaller than the predetermined opening, further upshifting from the speed ratio when the accelerator opening is the predetermined opening, and fixing the speed ratio to a higher gear side than the speed ratio when the accelerator opening is the predetermined opening; Thereafter, a step of further performing an upshift from the fixed speed ratio according to the accelerator opening degree.

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