Control device

Abstract

To provide a technique capable of switching a shift line with improved appropriateness in an automatic transmission of a vehicle.SOLUTION: In a control device 16 which controls an automatic transmission 14 of a vehicle, a shift line determination section 24 determines a shift line for controlling a shift stage of the automatic transmission 14. When receiving a request to switch from a first shift line to a second shift line while the shift line is set to the first shift line, a determination section 22 determines whether a vehicle state allows the shift line to be switched. When the determination section determines that the vehicle state does not allow the shift line to be switched, the shift line determination section 24 maintains the first shift line. Later, when the determination section determines that the vehicle state allows the shift line to be switched, the shift line determination section switches only an upshift line to the upshift line of the second shift line. When no downshift occurs even when a downshift line is switched after only the upshift line has been switched, the shift line determination section 24 switches the downshift line to the downshift line of the second shift line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for controlling an automatic transmission of a vehicle. [Background technology]

[0002] Patent Document 1 discloses a vehicle control device that selects one of multiple shift maps. During an upshift, the device selects a shift map that makes upshifting more difficult before the catalyst temperature reaches a first catalyst specified value after the internal combustion engine starts than after the catalyst temperature reaches the first catalyst specified value. Furthermore, during a downshift, the device selects a shift map that makes downshifting more difficult before the catalyst temperature reaches a second catalyst specified value than after the catalyst temperature reaches the second catalyst specified value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-32270 Summary of the Invention [Problem to be solved by the invention]

[0004] In vehicles equipped with a stepped automatic transmission, a technology is known in which the shift line is switched and a downshift occurs when the driver switches the driving mode to a sport mode or the like. However, depending on the vehicle condition, such as when the vehicle is cold, the current shift line is maintained without switching the shift line. Even when the vehicle is in a state where the shift line can be switched, such as after warming up, switching the shift line can cause a sudden downshift, which can be a discomforting experience for the driver. Therefore, once the vehicle is in a state where the shift line can be switched, the shift line is switched when the vehicle speed or accelerator opening enters a range where switching the shift line will not cause a downshift.

[0005] However, depending on the settings of the shift lines after switching, the area in which downshifts do not occur may be narrow, and the shift lines may remain unable to be switched. In this case, the vehicle's performance may not be fully utilized.

[0006] An object of the present invention is to provide a technique that can more appropriately switch shift lines in an automatic transmission of a vehicle. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one aspect of the present invention provides a control device for controlling an automatic transmission of a vehicle, the control device including: a shift line determination unit that determines a shift line for controlling a gear position of the automatic transmission; and a determination unit that, when a first shift line is determined as the shift line, receives a request to switch from the first shift line to a second shift line and determines whether the vehicle state allows switching of the shift line. If it is determined that the vehicle state does not allow switching of the shift line, the shift line determination unit maintains the first shift line; if it is subsequently determined that the vehicle state allows switching of the shift line, the shift line determination unit switches only the upshift line to the upshift line of the second shift line; and if, with only the upshift line switched, switching the downshift line does not result in a downshift, the downshift line is switched to the downshift line of the second shift line. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique that can more appropriately switch shift lines in an automatic transmission of a vehicle. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic functional configuration of a control system according to an embodiment. [Figure 2] FIG. 2(a) is a diagram showing an example of an upshift line for each of the first and second shift lines, and FIG. 2(b) is a diagram showing an example of a change in vehicle speed and gear position over time in the embodiment and the comparative example. [Figure 3]FIG. 4 is a diagram showing an example of the relationship between the engine rotation speed and the output shaft rotation speed of an automatic transmission. [Figure 4] 10 is a flowchart showing the processing of the control system. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 shows a schematic functional configuration of a control system 100 according to an embodiment. The control system 100 is mounted on a vehicle (not shown). The control system 100 includes an engine 10, a torque converter 12, an automatic transmission 14, and a control device 16.

[0011] The engine 10 is an internal combustion engine that outputs torque according to the accelerator pedal position detected by a sensor (not shown). The torque output from the engine 10 is transmitted to the drive wheels (not shown) of the vehicle via a torque converter 12 and an automatic transmission 14.

[0012] An input shaft of a torque converter 12 equipped with a lock-up clutch is connected to the crankshaft of the engine 10. An output shaft of the torque converter 12 is connected to an input shaft of an automatic transmission 14.

[0013] The automatic transmission 14 is a multi-speed, stepped transmission that can change gears under the control of the control device 16. The gears can also be called gear stages. Changing the gear stage changes the gear ratio. Below, an example will be described in which the gear stage can be selected from eight stages, from "1st speed" to "8th speed," but the total number of gear stages is not particularly limited. The output shaft of the automatic transmission 14 is connected to the left and right drive wheels via a differential gear (not shown).

[0014] The automatic transmission 14 is provided with a hydraulic circuit (not shown). The gear shifting operation of the automatic transmission 14 is carried out by the control of the hydraulic circuit by the control device 16. The automatic transmission 14 is provided with a rotation speed sensor (not shown) that detects the rotation speed of an output shaft of the automatic transmission 14 (hereinafter referred to as output shaft rotation speed) and supplies information on the detected output shaft rotation speed to the control device 16. Note that the automatic transmission 14 may be a continuously variable transmission that can set the gear ratio in steps.

[0015] The engine 10, torque converter 12, and automatic transmission 14 may have known configurations, and therefore further detailed description thereof will be omitted.

[0016] A driving mode selection switch (not shown), such as a normal mode selection switch, a sport mode selection switch, or an eco mode selection switch, is provided near the driver's seat inside the vehicle. When the driver operates one of the driving mode selection switches, the vehicle switches to the driving mode corresponding to the operated switch. For example, in the sport mode, the engine output is made more responsive to accelerator operation than in the normal mode, and the engine speed is maintained at a high speed. The sport mode may be a mode for circuit driving. Various known control methods can be used to control each driving mode.

[0017] When the driving mode selection switch is operated, a predetermined control request corresponding to the operated switch is supplied to an engine ECU (Electronic Control Unit) that controls the engine 10. When the driving mode selection switch is operated, a request to switch the shift line corresponding to the operated switch is supplied to the control device 16.

[0018] When the shift lever (not shown) is in a forward drive position, the control device 16 controls the gear position of the automatic transmission 14 in accordance with the shift lines of the shift map based on the accelerator opening and the output shaft rotation speed of the automatic transmission 14.

[0019] The control device 16 has a reception unit 20, a determination unit 22, a shift line determination unit 24, and a shift control unit 26. The functional configuration of the control device 16 can be realized by the cooperation of hardware resources and software resources. The control device 16 has a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. as hardware resources. The ROM stores various control programs and maps referenced when executing these various control programs, etc. as software resources. The CPU executes calculations based on the various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores the results of calculations by the CPU, data input from each sensor, etc. The control device 16 can be configured with an ECU.

[0020] The shift line determination unit 24 stores in advance shift maps for each driving mode, such as a shift map for normal mode and a shift map for sport mode. The shift map can also be called a shift line diagram. The shift map is a map that shows the gears to be set in the automatic transmission 14 in correspondence with the output shaft rotation speed and the accelerator opening. In the shift map, multiple gears are defined in an orthogonal coordinate system with the output shaft rotation speed and the accelerator opening as the coordinate axes. In the shift map, multiple shift lines for switching gears are set according to the number of gears. The shift lines include multiple upshift lines and multiple downshift lines.

[0021] The shift line determination unit 24 determines shift lines for controlling the gear positions of the automatic transmission 14, and supplies information about the determined shift lines to the shift control unit 26. The process of determining the shift lines will be described in detail later.

[0022] The shift control unit 26 controls the gear position of the automatic transmission 14 based on the accelerator opening, the output shaft rotation speed of the automatic transmission 14, and the upshift line and downshift line of the shift line determined by the shift line determination unit 24. Vehicle speed may be used instead of the output shaft rotation speed of the automatic transmission 14.

[0023] For the same accelerator opening, the gear shift control unit 26 selects a higher gear as the output shaft rotation speed increases.For the same output shaft rotation speed, the gear shift control unit 26 selects a lower gear as the accelerator opening increases.

[0024] When the output shaft rotation speed is increasing or the accelerator pedal stroke is decreasing, the gear shift control unit 26 determines the gear position based on the upshift line. An upshift is determined when the output shaft rotation speed changes so that the upshift line crosses from the low output shaft rotation speed side to the high output shaft rotation speed side, or when the accelerator pedal stroke changes so that the upshift line crosses from the large accelerator pedal stroke side to the small accelerator pedal stroke side. In other words, the gear shift control unit 26 upshifts the gear position as the output shaft rotation speed increases or the accelerator pedal stroke decreases.

[0025] Conversely, when the output shaft rotation speed is decreasing or the accelerator pedal stroke is increasing, gear shift control unit 26 determines the gear position based on the downshift line. A downshift decision is made when the output shaft rotation speed changes so that the downshift line crosses from the high output shaft rotation speed side to the low output shaft rotation speed side, or when the accelerator pedal stroke changes so that the downshift line crosses from the low accelerator pedal stroke side to the high accelerator pedal stroke side. In other words, gear shift control unit 26 downshifts the gear position as the output shaft rotation speed decreases or the accelerator pedal stroke increases.

[0026] The receiving unit 20 receives a request to switch the shift line in response to operation of the driving mode selection switch, and notifies the determining unit 22 and the shift line determining unit 24 of the receipt of the switch request.

[0027] The currently selected shift line is referred to as the first shift line, and the shift line after switching is referred to as the second shift line. An example will be described below in which the sport mode selection switch is operated in normal mode to switch to sport mode. That is, an example will be described in which the first shift line is a shift line for normal mode, and the second shift line is a shift line for sport mode. The reception unit 20 receives a request to switch from the first shift line to the second shift line.

[0028] As will be described later with reference to Figure 2(a), at least a portion of the upshift lines of the second shift lines is set to allow upshifts at a higher vehicle speed than the upshift lines of the first shift lines. Although not shown, at least a portion of the downshift lines of the second shift lines is set to allow downshifts at a higher vehicle speed than the downshift lines of the first shift lines. In this way, in the sport mode, in order to maintain high engine speed, the shift lines are set to select a lower gear than in the normal mode at a certain vehicle speed.

[0029] When the first shift line is determined as the shift line and a request to switch from the first shift line to the second shift line is received, the determination unit 22 determines whether the vehicle is in a state where the shift line can be switched to the requested second shift line. The determination unit 22 supplies the determination result to the shift line determination unit 24.

[0030] The determination unit 22 determines that the vehicle state allows for switching of the shift line when the vehicle state satisfies predetermined criteria for switching to the requested shift line based on a sensor signal indicating the vehicle state. Known technologies can be used as the sensor signal and the predetermined criteria.

[0031] For example, the vehicle state may be the temperature of the coolant of the engine 10. The vehicle state satisfying the predetermined standard may be the temperature of the coolant exceeding a temperature threshold. In other words, the determination unit 22 may determine that the vehicle state is not such that the shift line can be switched when the vehicle is cold, or may determine that the vehicle state is such that the shift line can be switched after the vehicle has warmed up. This makes it possible to prevent the engine speed from being maintained at a high speed when the vehicle is cold.

[0032] When the shift line is determined to be the first shift line, if a request to switch from the first shift line to the second shift line is received, the shift line determination unit 24 switches from the first shift line to the second shift line if the determination unit 22 determines that the vehicle state allows switching of the shift line.

[0033] If the gear position determined by the accelerator opening and output shaft rotation speed when the shift line is switched from the first shift line to the second shift line is smaller than the current gear position, the shift control unit 26 downshifts to the gear position determined by the accelerator opening and output shaft rotation speed. In this case, because the shift line is switched in response to the driver's operation to change the driving mode, even if a shift shock occurs due to the downshift caused by switching the shift line, the driver can easily recognize that the downshift is caused by the operation to change the driving mode, so the driver does not feel uncomfortable.

[0034] On the other hand, if the determination unit 22 determines that the vehicle state is not such that the shift line can be switched, the shift line determination unit 24 maintains the first shift line until the determination unit 22 determines that the vehicle state is such that the shift line can be switched. In this case, the driving mode has been switched, and the control of the engine 10 and the like has been switched to sport mode control.

[0035] After maintaining the first shift line, if the determination unit 22 determines that the vehicle state allows for switching the shift lines, the shift line determination unit 24 switches only the upshift line to the upshift line of the second shift line. When only the upshift line is switched to the upshift line of the second shift line, the shift control unit 26 does not downshift, regardless of the relationship between the accelerator opening and output shaft rotation speed at that time and the upshift line.

[0036] Here, a shift control of a comparative example will be described. In the comparative example, when the shift line is determined to be the first shift line, if a request to switch from the first shift line to the second shift line is received and the vehicle state is not such that the shift line can be switched, the first shift line is maintained until the vehicle state becomes such that the shift line can be switched, which is the same as in the embodiment. In the comparative example, if the vehicle state becomes such that the shift line can be switched while the first shift line is maintained, the first shift line is switched to the second shift line only if switching the shift line would not result in a downshift. In other words, in the comparative example, if the vehicle state becomes such that the shift line can be switched while the first shift line is maintained, and switching the shift line would result in a downshift, the first shift line is maintained without switching the shift line.

[0037] 2(a) shows an example of upshift lines for the first and second shift lines. The horizontal axis represents the output shaft rotation speed of the automatic transmission 14, and the vertical axis represents the accelerator pedal position. Upshift lines 1a, 2a, 3a, 4a, 5a, 6a, and 7a for the first shift line are shown with solid lines. Upshift lines 1b, 2b, 3b, 4b, 5b, 6b, and 7b for the second shift line are shown with dashed lines.

[0038] Upshift lines 1a and 1b are shift lines for shifting from "1st gear" to "2nd gear." Upshift lines 2a and 2b are shift lines for shifting from "2nd gear" to "3rd gear." Upshift lines 3a and 3b are shift lines for shifting from "3rd gear" to "4th gear." Upshift lines 4a and 4b are shift lines for shifting from "4th gear" to "5th gear." Upshift lines 5a and 5b are shift lines for shifting from "5th gear" to "6th gear." Upshift lines 6a and 6b are shift lines for shifting from "6th gear" to "7th gear." Upshift lines 7a and 7b are shift lines for shifting from "7th gear" to "8th gear."

[0039] In the illustrated example, when the accelerator pedal depression is relatively small, the upshift line of the second shift line is set at a higher vehicle speed than the upshift line of the corresponding first shift line. When the accelerator pedal depression is relatively large, the upshift line of the second shift line overlaps with the upshift line of the corresponding first shift line. For example, when the accelerator pedal depression is approximately 55% or less, the upshift line 4b of the second shift line is set at a higher vehicle speed than the upshift line 4a of the first shift line. Therefore, by switching from the upshift line of the first shift line to the upshift line of the second shift line, the upshift point during acceleration becomes a higher vehicle speed. Note that all of the upshift lines of the second shift lines may be set at a higher vehicle speed than the upshift line of the corresponding first shift line, regardless of the accelerator pedal depression.

[0040] Figure 2(b) shows an example of the vehicle speed and gear change over time in the embodiment and the comparative example. Figure 2(b) shows the operation after a request to switch from the first shift line to the second shift line is received, and the vehicle state changes from one in which the shift line cannot be switched to one in which the shift line can be switched. The vehicle speed is the same in both the embodiment and the comparative example, and gradually increases from time t0 to time t6.

[0041] In the comparative example, since the first shift line is maintained in this situation, the gear 70 in the comparative example upshifts from "4th gear" to "5th gear" at time t1, upshifts from "5th gear" to "6th gear" at time t3, and upshifts from "6th gear" to "7th gear" at time t5 as the vehicle speed increases.

[0042] Here, assuming that the second shift line is switched to the downshift line, the selected gear 74 is "3rd gear" until time t2, "4th gear" from time t2 to time t4, and "5th gear" after time t4.

[0043] Therefore, in the comparative example, during the illustrated period, a downshift occurs regardless of when the shift line is switched, so the shift line cannot be switched. In this way, in the comparative example, the timing of the upshift during vehicle acceleration is relatively early on the first shift line before the switch, narrowing the area in which a downshift does not occur after the shift line is switched. Therefore, the state in which the shift line cannot be switched continues.

[0044] On the other hand, in the embodiment, because the second shift line is switched to the upshift line, gear 72 upshifts from "fourth gear" to "fifth gear" at time t4, after time t3 and before time t5, in response to an increase in vehicle speed. In other words, by switching only the upshift line, the timing of the upshift during vehicle acceleration becomes higher than in the comparative example. This can also be seen from FIG. 2(a).

[0045] Therefore, in this embodiment, after time t2, switching the second shift line to the downshift line does not result in a downshift. In other words, by switching only the upshift line, the upshift point during vehicle acceleration increases the vehicle speed, expanding the area where the downshift line matches the gear position after switching. This allows the area in which the shift line can be switched to be expanded without a downshift.

[0046] Therefore, if a downshift does not occur even when the downshift lines are switched with only the upshift lines switched, the shift line determination unit 24 switches the downshift line to the downshift line of the second shift line.

[0047] In this way, when it is determined that the vehicle state allows for switching of the shift lines, switching only the upshift line to the upshift line of the second shift line allows upshifts to occur at a higher vehicle speed than when the upshift line of the first shift line is used. Therefore, downshifts can be made less likely when the downshift line is switched to the downshift line of the second shift line. This makes it easier to switch the shift line to the second shift line while suppressing the occurrence of unexpected shift shock due to downshifts. It makes it easier to switch the shift line to the second shift line at an earlier timing than in the comparative example. In other words, the shift line can be switched more appropriately. This allows the vehicle to demonstrate its performance and improves its convenience.

[0048] On the other hand, if the vehicle speed does not increase or the accelerator pedal stroke does not decrease after switching only the upshift line, an upshift will not occur based on the switched upshift line. In this case, switching the downshift line may result in a downshift.

[0049] When switching the downshift line while only the upshift line has been switched results in a downshift, the shift line determination unit 24 switches the downshift line to the downshift line of the second shift line if the change in engine speed due to the downshift is equal to or less than a threshold value. The threshold value can be determined as appropriate through experiments or simulations.

[0050] When switching the downshift line while only the upshift line has been switched causes a downshift, if the change in engine speed due to the downshift is greater than a threshold value, the shift line determination unit 24 maintains the first shift line without switching the shift line.

[0051] Figure 3 shows an example of the relationship between engine speed and output shaft speed of automatic transmission 14. The solid line shows the relationship in the case of the downshift line of the current first shift line. The dashed line shows the relationship in the case of the downshift line of the second shift line after switching. Figure 3 shows the relationship at a certain accelerator opening.

[0052] As the output shaft rotation speed decreases, the gear position decreases stepwise from "8th gear" to "2nd gear." The output shaft rotation speed at the boundary between "nth gear" and "(n-1)th gear" in the case of the first shift line, where n is an integer between 3 and 8, is lower than the output shaft rotation speed at the boundary between "nth gear" and "(n-1)th gear" in the case of the second shift line. Therefore, as described above, the engine rotation speed is maintained higher in the case of the second shift line than in the case of the first shift line.

[0053] Region R1 is the region of output shaft rotation speeds below which "second gear" is selected for the first shift line. Region R2 is the region of output shaft rotation speeds below which "eighth gear" is selected for the second shift line. When the output shaft rotation speed is in region R1 or region R2, even if the downshift line of the current first shift line is switched to a downshift line of the second shift line, the gear remains the same and no downshift occurs. Therefore, when the output shaft rotation speed is in region R1 or region R2, the shift line determination unit 24 switches the downshift line to the downshift line of the second shift line.

[0054] Furthermore, region R11 is a region of output shaft rotation speed where "third gear" to "fifth gear" is selected in the case of the first shift line, for example. In region R11, even if a downshift occurs, the change amount V1 in engine rotation speed is equal to or less than a threshold value. When the output shaft rotation speed is in region R11 and the downshift line of the current first shift line is switched to the downshift line of the second shift line, if the current gear is "third gear" and the output shaft rotation speed is in a relatively low region, the gear remains unchanged in the case where the current gear is "third gear" and the output shaft rotation speed is in a relatively high region, and if the current gear is "fourth gear" or "fifth gear," a downshift occurs to "third gear."

[0055] Region R12 is the region of output shaft rotation speed where, for example, "7th gear" is selected in the case of the second shift line. In region R12, even if a downshift occurs, the change amount V2 in engine rotation speed is assumed to be equal to or less than a threshold value. When the output shaft rotation speed is in region R12, switching from the current first shift line to the second shift line results in a downshift from the current gear position of "8th gear" to "7th gear."

[0056] Therefore, if the output shaft rotational speed is in region R11 or region R12, the shift line determination unit 24 switches the downshift line to the downshift line of the second shift line. Even if a downshift occurs due to the switching of the shift line, the fluctuation in engine rotational speed is relatively small, so the shift shock due to the downshift is relatively small. This reduces the sense of discomfort felt by the driver. Also, it is easier to switch the shift line to the second shift line at an earlier timing than in the comparative example. In other words, the shift line can be switched more appropriately. This allows the vehicle's performance to be fully utilized, and also improves the convenience of the vehicle.

[0057] Furthermore, when the output shaft rotation speed is in region R13, which is greater than the maximum value in region R11 and less than the minimum value in region R12, switching from the downshift line of the current first shift line to the downshift line of the second shift line results in a downshift. The change in engine rotation speed at this time is greater than the threshold value. Therefore, if the output shaft rotation speed is in region R13, the shift line determination unit 24 maintains the first shift line. This makes it possible to prevent a relatively large shift shock caused by an unexpected downshift due to switching of the shift line, thereby reducing discomfort felt by the driver.

[0058] Next, a description will be given of the overall operation of the control system 100 configured as described above. Figure 4 is a flowchart showing the processing of the control system 100. The processing of Figure 4 is repeated periodically.

[0059] If there is no request to switch the shift line (N in S10), the process ends. If there is a request to switch the shift line (Y in S10), and the vehicle state allows switching to the requested shift line (Y in S12), the shift line determination unit 24 switches the shift line (S28), and the process ends.

[0060] If the vehicle state is not such that switching to the requested shift line is possible (N in S12), the shift line determination unit 24 maintains the current shift line (S14), and if the vehicle state is not such that switching to the requested shift line is possible (N in S16), the process returns to the determination in S16. If the vehicle state is such that switching to the requested shift line is possible in S16 (Y in S16), the shift line determination unit 24 switches only the upshift line (S20). If switching the downshift line does not result in a downshift (N in S22), the shift line determination unit 24 switches the downshift line (S26), and the process ends.

[0061] If a downshift occurs due to switching of the downshift lines in S22 (Y in S22), and if the change in engine speed due to switching of the downshift lines is equal to or less than the threshold value (Y in S24), the process proceeds to S26. If the change in engine speed due to switching of the downshift lines is not equal to or less than the threshold value in S24 (N in S24), the process returns to S22.

[0062] The present invention has been described above based on the embodiments. However, the embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention.

[0063] For example, the vehicle may be a hybrid vehicle (HEV: Hybrid Electric Vehicle) or a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle), and may be capable of supplying the driving force of a motor to the torque converter 12 in addition to the driving force of the engine 10. [Explanation of symbols]

[0064] 10... engine, 12... torque converter, 14... automatic transmission, 16... control device, 20... reception unit, 22... determination unit, 24... shift line determination unit, 26... shift control unit, 100... control system

Claims

[Claim 1] A control device for controlling an automatic transmission of a vehicle, a shift line determination unit that determines a shift line for controlling a gear position of the automatic transmission; a determination unit that, when a request for switching from the first shift line to the second shift line is received while the shift line is determined to be the first shift line, determines whether the vehicle is in a state in which the shift line can be switched, The shift line determination unit When it is determined that the vehicle state is not such that the shift line can be switched, the first shift line is maintained, and thereafter, when it is determined that the vehicle state is such that the shift line can be switched, only the upshift line is switched to the upshift line of the second shift line; When only the upshift line has been switched and the downshift line has been switched but no downshift occurs, the downshift line is switched to the downshift line of the second shift line. A control device characterized by:

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