JP2018119608A - Coast stop control device and coast stop control method for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve Low return of an automatic transmission without generating excessive deceleration on a vehicle after establishing a coast stop condition.SOLUTION: In a vehicle including an oil pump 8 which generates a working hydraulic pressure of an automatic transmission TM by being driven by an output of an engine 1, in the case where a predetermined coast stop condition is established during deceleration travel of a vehicle, a coast stop is executed for stopping the engine 1. It is determined whether or not the coast stop condition is established, and in the case where the coast stop condition is determined to have been established, clutch slip control is executed in which, while maintaining formation of an engagement force of a lock-up clutch 23 of a torque converter 2, differential rotation generated between an input element and an output element of the lock-up clutch 23. Then, while executing the clutch slip control, a transmission ratio of the automatic transmission TM is increased further than at the time when the coast stop condition is determined to have been established, and after the increase of the transmission ratio, the lock-up clutch 23 is released.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle coast stop control device and a coast stop control method provided in a vehicle including an oil pump driven by the output of an engine.

  Patent Document 1 discloses a vehicle or an automatic transmission that includes an oil pump that is driven by the output of an engine, and that uses this oil pump to generate a hydraulic pressure necessary for a speed change operation.

JP2011-001913A (paragraph 0049)

  In order to improve fuel efficiency, it is already known that after fuel supply to the engine is stopped by fuel cut during deceleration traveling, the engine is stopped by shifting to a coast stop. For coast stop, for example, after the fuel cut, the lock-up clutch provided in the torque converter is released to cut off the transmission of power between the engine and the drive wheels.

  Here, in order to secure the driving force necessary for restart after stopping, it is conceivable to perform the following control at the coast stop. After releasing the lock-up clutch, the fuel supply is once resumed by the fuel cut recovery, and the oil pump is driven by the output of the engine. Then, after increasing the gear ratio of the variator to the set maximum gear ratio, the fuel supply is stopped again and the coast stop is executed.

  However, such control has a problem that fuel consumption deteriorates because fuel supply is resumed. Furthermore, there is a concern that the driver may feel uncomfortable because the engine starts even though the vehicle is decelerating.

  If the coast stop is executed after the lockup clutch is released without restarting the fuel supply, the hydraulic pressure of the automatic transmission cannot be obtained, and the gear ratio cannot reach the maximum gear ratio. As a result, the driving force at the time of restarting is insufficient, and sufficient startability cannot be ensured.

  On the other hand, it is possible to drive the oil pump and reach the maximum gear ratio by maintaining the state where the lockup clutch is engaged without shifting to the coast stop. However, in this case, excessive deceleration occurs in the vehicle as the gear ratio increases, and the drivability may affect the drivability.

  An object of the present invention is to provide a vehicle coast stop control device and a coast stop control method in consideration of the above problems.

  In one aspect, the present invention provides an engine, an automatic transmission, a torque converter interposed between the engine and the automatic transmission, and an oil pump that is driven by the output of the engine to generate an operating hydraulic pressure of the automatic transmission. A coast stop control device for a vehicle is provided that executes a coast stop that stops the engine when a predetermined coast stop condition is satisfied during deceleration of the vehicle. The coast stop control device according to the present embodiment includes a coast stop condition determination unit that determines whether or not a coast stop condition is satisfied, and engagement of a lockup clutch provided in the torque converter when it is determined that the coast stop condition is satisfied. While maintaining the force formation, the clutch engagement control unit that causes differential rotation between the input and output elements of the lockup clutch and the gear ratio of the automatic transmission are increased compared to when the coast stop condition is satisfied. And a clutch release control unit that releases the lock-up clutch after the transmission ratio is increased.

  Furthermore, in another form, an engine, an automatic transmission, a torque converter interposed between the engine and the automatic transmission, an oil pump that is driven by the output of the engine and generates an operating hydraulic pressure of the automatic transmission, A vehicle coast stop control method is provided that executes a coast stop that stops the engine when a predetermined coast stop condition is satisfied during deceleration traveling of the vehicle. The coast stop control method according to the present embodiment determines whether or not the coast stop condition is satisfied, and maintains the formation of the fastening force of the lockup clutch provided in the torque converter when it is determined that the coast stop condition is satisfied. On the other hand, clutch slip control that causes differential rotation between the input element and output element of the lockup clutch is executed, and during the clutch slip control, the gear ratio of the automatic transmission is determined when the coast stop condition is satisfied. After increasing the gear ratio, the lockup clutch is released.

  According to the above aspect, after the coast stop condition is established, by maintaining the formation of the fastening force of the lock-up clutch, the oil pump is operated, the hydraulic pressure of the automatic transmission can be formed, the gear ratio is increased, The driving force of the vehicle at the time of reacceleration or re-starting can be ensured. Further, by causing a differential rotation between the input element and the output element of the lockup clutch, it is possible to reduce the feeling of deceleration according to the increase in the gear ratio.

FIG. 1 is a schematic diagram showing an overall configuration of a vehicle drive system according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of coast stop control according to the embodiment. FIG. 3 is an explanatory diagram showing a low return execution area of the coast stop control. FIG. 4 is an explanatory diagram showing the operation of the vehicle drive system when not using the coast stop control. FIG. 5 is an explanatory diagram showing the operation of the vehicle drive system when the coast stop control is performed.

  Embodiments of the present invention will be described below with reference to the drawings.

(Configuration of vehicle drive system)
FIG. 1 schematically shows an overall configuration of a vehicle drive system P according to an embodiment of the present invention.

  A vehicle drive system P according to the present embodiment includes an internal combustion engine (hereinafter simply referred to as “engine”) 1 as a drive source, and a torque converter 2 and an automatic motor on a power transmission path that connects the engine 1 and left and right drive wheels 7. A transmission TM is provided. In the present embodiment, the automatic transmission TM includes a forward / reverse switching mechanism 3 and a variator 4. The automatic transmission TM converts rotational power input from the engine 1 via the torque converter 2 at a predetermined gear ratio, and outputs it to the drive wheels 7 via the differential gear 5.

  The torque converter 2 includes a pump impeller 21 connected to the input shaft of the torque converter 2 and a turbine runner 22 connected to the output shaft of the torque converter 2, and the input rotational power is converted into a mechanical action of fluid. Via the output shaft. The torque converter 2 further includes a lock-up clutch 23 connected to the output shaft. By setting the lock-up clutch 23 to the engaged state, the input shaft and the output shaft are directly connected, and transmission loss due to fluid connection is reduced. It is possible. Engagement and disengagement of the lockup clutch 23 can be switched by controlling a hydraulic pressure acting on the lockup clutch 23 (hereinafter also referred to as “lockup hydraulic pressure”).

  The forward / reverse switching mechanism 3 is disposed between the torque converter 2 and the variator 4 and switches the traveling direction of the vehicle between forward and backward by switching the rotation direction of the output shaft. The forward / reverse switching mechanism 3 includes a forward clutch 31 that is fastened when the forward range is selected and a reverse brake 32 that is fastened when the reverse range is selected. The vehicle is moved backward in a state in which 32 is fastened. Whether the forward range or the reverse range is selected is determined based on the position of the shift lever operated by the driver. When both the forward clutch 31 and the reverse brake 32 are released, the automatic transmission TM is in a neutral state, and transmission of rotational power through the automatic transmission TM is interrupted. The operation of the forward / reverse switching mechanism 3 is controlled by adjusting the hydraulic pressure acting on the forward clutch 31 and the reverse brake 32.

  The variator 4 includes a primary pulley 41 and a secondary pulley 42 as transmission elements, and includes a metal belt 43 wound between these pulleys 41 and 42, and the metal belt 43 contacts the primary pulley 41 and the secondary pulley 42. It is possible to change the transmission gear ratio Rva steplessly by changing the ratio of the part radii. The gear ratio Rva of the variator 4 adjusts the hydraulic pressure (hereinafter sometimes referred to as “working hydraulic pressure” or “transmission hydraulic pressure”) acting on the movable sheave of the primary pulley 41 and the secondary pulley 42, and It is controlled by changing the width of the V-groove formed on the substrate. In the present embodiment, a value obtained by dividing the rotational speed Npri of the primary pulley 41 by the rotational speed Nsec of the secondary pulley 42 is defined as the transmission ratio Rva of the variator 4 (Rva = Npri / Nsec).

  The rotational power output from the automatic transmission TM is transmitted to the drive shaft 6 through the gear train set to a predetermined gear ratio and the differential 5 to rotate the drive wheels 7.

  In this embodiment, a mechanically driven oil pump 8 is used as a source of hydraulic pressure to be applied to the lockup clutch 23 of the torque converter 2, the friction engagement elements 31, 32 of the forward / reverse switching mechanism 3, and the transmission elements 41, 42 of the variator 4. Is provided. The oil pump 8 is driven by the output of the engine 1, boosts the operating oil to a predetermined pressure, and supplies it to each of these parts via the hydraulic control circuit 9. FIG. 1 shows a hydraulic pressure supply path from the hydraulic pressure control circuit 9 to each part by dotted lines with arrows. In this embodiment, the pump impeller 21 of the torque converter 2 and the rotating shaft of the oil pump 8 are connected via a power transmission medium, and the rotational power of the engine 1 is transmitted to the oil pump 8 via the power transmission medium. Communicated.

(Control system configuration and basic operation)
The operations of the engine 1 and the automatic transmission TM are controlled by the engine controller 101 and the transmission controller 201, respectively. Each of these controllers 101 and 201 is configured as an electronic control unit, and includes a central processing unit (CPU), various storage devices such as RAM and ROM, and a microcomputer provided with an input / output interface and the like.

  The engine controller 101 receives a detection signal from an operation state sensor that detects the operation state of the engine 1, executes a predetermined calculation based on the operation state, and performs a fuel injection amount, fuel injection timing, ignition timing, and the like of the engine 1. Set. In this embodiment, the engine controller 101 determines whether or not a predetermined fuel cut condition is satisfied in addition to the normal engine control routine, and supplies fuel to the engine 1 when the fuel cut condition is satisfied. Execute fuel cut to temporarily stop. After the fuel cut is started, the engine controller 101 determines whether or not a predetermined fuel cut cancellation condition is satisfied. If the fuel cut cancellation condition is satisfied, the fuel controller is canceled and fuel is supplied to the engine 1. Let it resume.

  In the present embodiment, as a driving state sensor, an accelerator sensor 111 that detects an accelerator pedal operation amount (hereinafter referred to as “accelerator opening”) APO by a driver, a rotational speed sensor 112 that detects a rotational speed of the engine 1, an engine cooling In addition to a cooling water temperature sensor 113 for detecting the water temperature TW, an air flow meter, a throttle sensor, a fuel pressure sensor, an air-fuel ratio sensor, and the like (not shown) are provided. In the present embodiment, the rotational speed sensor 112 is configured by a crank angle sensor, and the engine controller 101 determines the rotational speed of the engine 1 based on a reference crank angle output from the crank angle sensor or a signal for each unit crank angle. The engine speed NE (hereinafter referred to as “engine speed”) NE is calculated.

  The transmission controller 201 constitutes a “vehicle coast stop control device” according to this embodiment, and includes a “coast stop condition determination unit”, a “clutch engagement control unit”, a “shift control unit”, and a “clutch release”. The functions of “control unit”, “transmission ratio detection unit”, and “deceleration detection unit” are exhibited. In the present embodiment, the “vehicle coast stop control device” is configured only by the transmission controller 201 and the “vehicle coast stop control method” is performed. However, the present invention is not limited to this, and the engine controller 101 and the transmission controller 201 It is also possible to configure a “vehicle coast stop control device” in cooperation. Further, it can be realized only by the engine controller 101.

  In the present embodiment, in relation to the control of the automatic transmission TM, a vehicle speed sensor 211 that detects a vehicle traveling speed (hereinafter referred to as “vehicle speed”) VSP, and a brake pedal force BPF that indicates a depression amount of a brake pedal by a driver are detected. The brake sensor 212 and the rotation speed of the primary pulley 41 (the rotation speed per unit time, hereinafter referred to as “primary pulley rotation speed”) Npri for detecting the input side rotation speed sensor 213 and the rotation speed of the secondary pulley 42 (unit time) Output side rotational speed sensor 214 for detecting Nsec), and primary hydraulic pressure sensor for detecting transmission hydraulic pressure (hereinafter referred to as “primary hydraulic pressure”) Ppri acting on the primary pulley 41. 215, transmission hydraulic pressure acting on the secondary pulley 42 (hereinafter referred to as “Seca Secondary oil pressure sensor 216 for detecting Psec), oil temperature sensor 217 for detecting the oil temperature of the automatic transmission TM (hereinafter simply referred to as “oil temperature”), and the position of the shift lever (hereinafter “shift”). A shift position sensor 218 or the like for detecting SFT is provided. In the present embodiment, the vehicle speed sensor 211 is provided so as to be able to measure the rotational speed of the drive wheels 7, and the transmission controller 201 calculates the vehicle speed VSP based on the detection signal of the vehicle speed sensor 211.

  The transmission controller 201 is communicably connected to the engine controller 101 via a CAN standard bus, and inputs an accelerator opening APO and the like as an operating state of the engine 1 from the engine controller 101, and also a fuel cut. A fuel cut signal indicating that the fuel cut is being executed and a fuel cut cancel signal indicating that the fuel cut has been canceled are input.

  The transmission controller 201 sets a target speed ratio tRva of the automatic transmission TM (in this embodiment, the variator 4) based on various signals indicating the accelerator opening APO and the vehicle speed VSP, and the actual speed ratio Rva of the variator 4 is set. The primary oil pressure Ppri and the secondary oil pressure Psec are controlled so as to approach the target speed ratio tRva. Specifically, a control signal is output to the hydraulic pressure control circuit 9 so that a predetermined shift hydraulic pressure acts on the primary pulley 41 and the secondary pulley 42 using the hydraulic pressure generated by the oil pump 8 as a base pressure.

  In the present embodiment, the transmission controller 201 determines whether or not a predetermined coast stop condition is satisfied while the vehicle is decelerating, and executes the coast stop when the coast stop condition is satisfied. “Coast stop” refers to stopping the engine 1 during traveling at a reduced speed, and is different from a fuel cut that simply stops the supply of fuel to the engine 1 in that the engine 1 is stopped. It is also distinguished from an idle stop that is performed while the vehicle is stopped in that it is performed while the vehicle is traveling. In the present embodiment, because of the coast stop, the supply of fuel to the engine 1 is stopped and the transmission of power between the engine 1 and the drive wheels 7 is interrupted to stop the engine 1. After executing the coast stop, the transmission controller 201 determines whether or not a predetermined coast stop cancel condition is satisfied, and when the coast stop cancel condition is satisfied, the fuel supply to the engine 1 is restarted. Start. The coast stop cancellation condition is satisfied, for example, when the brake pedal is returned during the coast stop. Hereinafter, the coast stop control executed by the transmission controller 201 will be described.

(Contents of coast stop control)
FIG. 2 shows an overall flow of coast stop control according to the present embodiment.

  The transmission controller 201 executes coast stop control according to the control routine shown in FIG. 2 when a predetermined fuel cut condition is satisfied.

  In S101, it is determined whether or not a fuel cut condition is satisfied. In the present embodiment, the fuel cut condition is satisfied when the accelerator pedal is at a position where the accelerator pedal is completely returned and the engine speed NE is equal to or greater than a predetermined value NEa. The predetermined value NEa is a value determined from the viewpoint of improving fuel efficiency, and is stored in the engine controller 101 in advance. The transmission controller 201 determines that the fuel cut condition is satisfied when a fuel cut signal is input from the engine controller 101. If the fuel cut condition is satisfied, the process proceeds to S102. If the fuel cut condition is not satisfied, the current control is terminated. When the fuel cut condition is satisfied, the engine controller 101 stops the fuel supply to the engine 1.

  In S102, it is determined whether or not a fuel cut cancellation condition is satisfied. In the present embodiment, the fuel cut cancellation condition is satisfied when the accelerator pedal is depressed by the driver. The transmission controller 201 determines that the fuel cut release condition is satisfied when a fuel cut release signal is input from the engine controller 101. When the fuel cut cancellation condition is satisfied, the current control is terminated. When the fuel cut cancellation condition is not satisfied, the process proceeds to S103. When the fuel cut cancellation condition is satisfied, the fuel supply to the engine 1 is resumed by the engine controller 101.

  In S103, it is determined whether a coast stop condition is satisfied. Specifically, it is satisfied when the driver depresses the brake pedal on the assumption that the fuel cut condition is satisfied and the fuel cut is being executed. In this embodiment, in addition to this, it is assumed that the vehicle speed VSP is lower than the predetermined value VSPa, and that the vehicle speed VSP is established only when the vehicle speed VSP is lower than the predetermined value VSPa. The predetermined value VSPa is a value determined from the viewpoint of drivability, and is stored in the transmission controller 201 in advance. If the processing proceeds while the vehicle speed VSP is higher than the predetermined value VSPa, and the speed ratio Rva is increased by the low return described below, excessive deceleration may occur with the speed change, which may affect drivability. Is done. By performing Low return when the vehicle speed VSP drops to some extent, it is possible to suppress deceleration and mitigate the influence on drivability. “Low return” refers to the operation of the automatic transmission TM in which the gear ratio is increased in advance during deceleration traveling in preparation for reacceleration or restart after deceleration. In this embodiment, the variator 4 The gear ratio Rva is increased to the lowest gear ratio. In this embodiment, the “lowest speed ratio” refers to the maximum speed ratio that the variator 4 can take. When the coast stop condition is satisfied, the process proceeds to S104. When the coast stop condition is not satisfied, the process returns to S102, and the processes of S102 and S103 are repeated.

  In S104, it is determined whether the Low return execution condition is satisfied. In the present embodiment, whether or not the Low return execution condition is satisfied is determined based on the deceleration G of the vehicle and the transmission ratio Rva of the variator 4, and the deceleration G is lower than a predetermined value Ga. This is true when Rva is lower than a predetermined value Ra. The transmission controller 201 calculates the deceleration G of the vehicle based on the vehicle speed VSP, and calculates the speed ratio Rva of the variator 4 based on the primary pulley rotation speed Npri and the secondary pulley rotation speed Nsec. By these calculations, the functions of the “deceleration detection unit” and the “speed ratio detection unit” are realized.

  Here, the predetermined values Ga and Ra are values determined from the viewpoint of the sensitivity of the shift by low return, and are stored in the transmission controller 201 in advance. FIG. 3 shows the deceleration G on the horizontal axis and the gear ratio Rva on the vertical axis. In FIG. 3, the region defined by the deceleration G and the gear ratio Rva is divided into four areas A to D. . The region D on the reduction speed and low gear ratio side is a region where Low return is executed.

  In FIG. 3, in regions B and C where the deceleration G is equal to or greater than a predetermined value Ga, the vehicle is in a state of rapid deceleration, and it is not possible to secure a sufficient time to obtain a sufficient effect by returning low. The execution of Low return is reserved. On the other hand, in the regions A and B where the gear ratio Rva is equal to or greater than the predetermined value Ra, the gear ratio Rva is already high and is in the low-side region, so that the execution of the low gear is reserved, assuming that the need for low return is low. . If the Low return execution condition is satisfied, the process proceeds to S105. Otherwise, the process proceeds to S108.

  In S105, slip control of the lockup clutch 23 (hereinafter referred to as "clutch slip control") is executed. In this embodiment, “clutch slip control” is an input element of the lockup clutch 23 while maintaining the formation of the fastening force of the lockup clutch 23 and enabling transmission of power through the lockup clutch 23. Control that causes differential rotation between the clutch piston and the cover shell as an output element. Specifically, the differential rotation is such that the target deceleration of the vehicle can be achieved, in other words, the deceleration generated by the low return is not excessive by maintaining the engagement state of the lockup clutch 23. A target value is set in advance, and the hydraulic pressure acting on the lockup clutch 23 is reduced so that this target value is obtained. Here, the control for reducing the lockup hydraulic pressure corresponds to the control of the fastening force of the lockup clutch 23. It is also possible to detect the actual differential rotation between the clutch piston and the cover shell and increase or decrease the lockup hydraulic pressure according to the deviation of the actual differential rotation from the target value.

  In S106, Low return is executed, and the gear ratio Rva of the variator 4 is increased more than when the coast stop condition is satisfied. In this embodiment, the target gear ratio for low return is set to the lowest gear ratio that is the maximum gear ratio of the variator 4, and the gear ratio Rva of the variator 4 is returned to this lowest gear ratio by returning low.

  In S107, it is determined whether or not the low return has been completed and the speed ratio Rva of the variator 4 has increased to the lowest speed speed ratio. If it has increased to the lowest gear ratio, the process proceeds to S108, and if it has not increased, the process returns to S105 to continue the clutch slip control and continue to perform Low return.

  In S108, the lockup clutch 23 is released, and the transmission of power between the engine 1 and the drive wheels 7 is interrupted to stop the engine 1.

  Thus, in the present embodiment, when the gear ratio Rva of the variator 4 increases to the lowest gear ratio, assuming that the low return is completed, the clutch slip control is terminated and the lockup clutch 23 is released. (S107, S108). However, the present invention is not limited to this, and even when the transmission gear ratio Rva of the variator 4 does not reach the lowest transmission gear ratio, when the driving force at the time of re-acceleration or re-starting is increased to a level that can secure a low return, It may be determined that the lockup clutch 23 has been substantially completed and the lockup clutch 23 is released in the same manner.

  In the present embodiment, the function of “coast stop condition determination unit” is realized by the process shown in S103 of the flowchart shown in FIG. 2, the function of “clutch engagement control unit” is realized by the process shown in S105, and S104, S106 and The function of “shift control unit” is realized by the process shown in S107, and the function of “clutch release control unit” is realized by the process shown in S108.

  4 and 5 schematically show the operation of the vehicle drive system from the start of deceleration (time t1) to the stop (time t5). FIG. 5 shows an operation when the coast stop control according to this embodiment is used, and FIG. 4 shows an operation when the coast stop control according to this embodiment is not used as a comparative example.

  When the accelerator pedal is returned (time t1) and the vehicle shifts to decelerating travel, fuel cut is executed and the vehicle speed VSP1 gradually decreases. The transmission controller 201 increases the target speed ratio tRva of the variator 4 according to the decrease in the vehicle speed VSP1, and finally increases it to the lowest speed speed ratio. Then, the actual speed ratio Rva1 is changed so as to follow the target speed ratio tRva (time t2 to t4).

  In the comparative example, as shown in FIG. 4, when the brake pedal is depressed during deceleration traveling (time t2), the hydraulic pressure Pl1 acting on the lockup clutch 23 is decreased (time t3) to lock up the coast stop. The clutch 23 is released. As a result, the transmission of power between the engine 1 and the drive wheels 7 is interrupted, and the engine speed NE1 rapidly decreases. FIG. 4 shows a delay from time D1 until the engine speed NE1 actually starts dropping after the lockup hydraulic pressure Pl1 starts to decrease.

  Here, in order to secure the driving force necessary for restart after the vehicle stops, after the lockup clutch 23 is released, the fuel supply is once resumed by the fuel cut recover and the oil pump 8 is driven by the output of the engine 1. FIG. 4 shows the rotational speed of the engine 1 when performing fuel cut recovery by the engine rotational speed NE1. When the transmission gear ratio Rva1 of the variator 4 reaches the final target transmission gear ratio tRva (lowest transmission gear ratio) (time t4), the turbine rotational speed NT1 of the torque converter 2 decreases with the vehicle speed VSP1, while fuel is supplied. Is stopped again to stop the engine 1. The time D2 indicates a delay from when the fuel supply is stopped until the engine speed NE1 starts dropping again.

  However, such control has a problem that fuel consumption deteriorates because fuel supply is resumed. Furthermore, since the engine 1 starts even though the vehicle is decelerating, there is a concern that the driver may feel uncomfortable.

  If the coast stop is executed without resuming the fuel supply after the lockup clutch 23 is released, the oil pump 8 cannot be operated, so that the hydraulic pressures Ppri and Psec necessary for shifting cannot be obtained. The gear ratio Rva2 cannot reach the lowest gear ratio. Therefore, the driving force at the time of restarting is insufficient, and sufficient startability cannot be ensured. The engine speed NE2 and the turbine speed NT2 gradually decrease after the lockup clutch 23 is released (time t3).

  On the other hand, the oil pump 8 is operated by keeping the lock-up clutch 23 engaged even after the brake pedal is depressed without shifting to the coast stop, and the gear ratio Rva reaches the lowest gear ratio. It is possible to make it. However, in this case, an excessive deceleration G3 occurs in the vehicle as the speed ratio Rva increases, and the drivability may affect the drivability.

  On the other hand, in this embodiment, as shown in FIG. 5, the clutch slipping is performed on the condition that the low return execution condition is satisfied after the brake pedal is depressed (time t2) and the coast stop condition is satisfied. Control is executed to cause a differential rotation ΔN between the input element and the output element of the lockup clutch 23 (time t3). FIG. 5 shows the hydraulic pressure acting on the lockup clutch 23 when the clutch slip control is executed as a lockup hydraulic pressure Pl. As a result, it is possible to operate the oil pump 8 and ensure the hydraulic pressures Ppri and Psec necessary for gear shifting. In clutch slip control, by controlling the lock-up hydraulic pressure Pl so as to obtain a differential rotation ΔN that can achieve the target deceleration of the vehicle, the deceleration G caused by the low return is suppressed, and drivability is improved. Can be mitigated. The clutch slip control is continued until the gear ratio Rva of the variator 4 reaches the lowest gear ratio, and after reaching the lowest gear ratio (time t4), the lockup hydraulic pressure Plu is further reduced, and the lockup clutch 23 is turned on. Let go. As a result, the input of power from the drive wheels 7 to the engine 1 is cut off, the engine speed NE is reduced, and the engine 1 is stopped.

(Explanation of effects)
The control apparatus for an automatic transmission according to the present embodiment is configured as described above. Hereinafter, effects obtained by the present embodiment will be described.

  First, after the coast stop condition is satisfied, the lockup clutch 23 is not completely released, and the formation of the engagement force of the lockup clutch 23 is maintained by clutch slip control, so that the oil pump 8 is operated and the automatic It becomes possible to form the operating hydraulic pressure or the transmission hydraulic pressures Ppri and Psec of the transmission TM. Thereby, at the time of coast stop, the gear ratio Rva of the variator 4 can be increased, and the driving force of the vehicle at the time of reacceleration or restart can be ensured. Then, by causing the differential rotation ΔN between the input element and the output element of the lockup clutch 23, it is possible to reduce the feeling of deceleration according to the increase in the speed ratio Rva. Therefore, according to the present embodiment, after the coast stop condition is satisfied, it is possible to achieve Low return without causing excessive deceleration in the vehicle. Furthermore, since it is not necessary to restart the engine 1 with a fuel cut recover for returning to low level, or to separately provide an electric oil pump, it is possible to reduce fuel consumption and suppress an increase in manufacturing cost. The space required for installing the electric pump can be reduced (effect corresponding to claims 1 and 6).

  Furthermore, according to the present embodiment, since the differential rotation ΔN between the input and output is generated by the lockup clutch 23, the other clutches (for example, the forward / reverse switching mechanism 3) of the other clutches can be reduced to reduce the feeling of deceleration. It is not necessary to loosen the fastening, and the driving force can be transmitted through the torque converter 2 at the time of re-acceleration, etc., and the acceleration can be maintained. Since the driving force is transmitted mainly through the fluid connection of the torque converter 2, it is possible to realize smooth acceleration with reduced shock (effect corresponding to claims 1 and 6).

  Secondly, the maximum drive force can be ensured at the time of re-acceleration or re-starting by increasing the transmission gear ratio Rva of the variator 4 to the lowest transmission gear ratio when returning Low. Corresponding effect).

  Thirdly, whether or not low return can be executed is determined from the viewpoint of speed change sensitivity, and when low return is not necessary, the process shifts to a coast stop without causing a differential rotation ΔN between the input and output of the lockup clutch 23. By releasing the lock-up clutch 23, the lock-up clutch 23 can be protected from deterioration due to wear (effect corresponding to claims 3 and 4).

  Fourth, in the clutch slip control, a target value of the differential rotation ΔN is set, and the fastening force of the lockup clutch 23, specifically, the lockup hydraulic pressure is reduced so that the actual differential rotation approaches the target value. By doing so, it becomes possible to moderate the deceleration moderately with respect to the increase in the transmission gear ratio Rva (effect corresponding to claim 5).

  The concepts that can be derived from the above description other than those described in the claims are listed below.

  The first is an automatic transmission control device that includes an oil pump that is driven by the output of an engine to generate the hydraulic pressure of the automatic transmission, and when a predetermined coast stop condition is satisfied during deceleration traveling of the vehicle. A coast stop condition determining unit that is mounted on a vehicle that executes a coast stop that stops the engine and determines whether the coast stop condition is satisfied, and a torque converter that is provided when it is determined that the coast stop condition is satisfied. While maintaining the formation of the locking force of the lockup clutch, the clutch engagement control unit that creates differential rotation between the input and output elements of the lockup clutch and the gear ratio of the automatic transmission satisfy the coast stop condition. Shift control unit that increases more than at the time of determination, and clutch that releases the lock-up clutch after the gear ratio increases Configured to include a release control unit.

  The second method is a control method for an automatic transmission. In a vehicle including an oil pump that is driven by an engine output to generate an operating hydraulic pressure of the automatic transmission, a predetermined coast stop condition is satisfied during the vehicle decelerating travel. If so, perform a coast stop to stop the engine. It is determined whether the coast stop condition is satisfied. When it is determined that the coast stop condition is satisfied, the lockup clutch input elements and outputs are maintained while maintaining the formation of the lockup clutch engagement force provided in the torque converter. Clutch slip control that causes differential rotation with the element is executed, and during the clutch slip control, the gear ratio of the automatic transmission is increased more than when the coast stop condition is satisfied, and after the gear ratio is increased The lock-up clutch is released.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various changes and modifications can be made within the scope of the matters described in the claims. Not too long.

P ... vehicle drive system TM ... automatic transmission 1 ... engine 2 ... torque converter 21 ... pump impeller 22 ... turbine runner 23 ... lock-up clutch 3 ... forward / reverse switching mechanism 31 ... forward clutch 32 ... reverse brake 4 ... variator 41 ... primary Pulley 42 ... Secondary pulley 43 ... Metal belt 5 ... Differential 6 ... Drive shaft 7 ... Drive wheel 8 ... Oil pump 9 ... Hydraulic control circuit 101 ... Engine controller 201 ... Transmission controller

Claims (6)

Engine,
An automatic transmission,
A torque converter interposed between the engine and the automatic transmission;
An oil pump that is driven by the output of the engine to generate the hydraulic pressure of the automatic transmission;
Provided in a vehicle equipped with
A coast stop control device for a vehicle that executes a coast stop for stopping the engine when a predetermined coast stop condition is satisfied during deceleration traveling of the vehicle,
A coast stop condition determining unit that determines whether or not the coast stop condition is satisfied;
When it is determined that the coast stop condition is satisfied, differential rotation is generated between the input element and the output element of the lockup clutch while maintaining the formation of the fastening force of the lockup clutch provided in the torque converter. A clutch engagement control unit;
A shift control unit that increases the gear ratio of the automatic transmission more than when the coast stop condition is satisfied;
A clutch release controller for releasing the lock-up clutch after the transmission ratio is increased;
A coast stop control device for a vehicle, comprising: The shift control unit increases the gear ratio of the automatic transmission to the lowest gear ratio,
2. The coast stop control device for a vehicle according to claim 1, wherein the clutch release control unit releases the lockup clutch after the gear ratio reaches the lowest gear ratio. 3. A gear ratio detector for detecting a gear ratio of the automatic transmission;
The shift control unit determines whether or not the gear ratio of the automatic transmission at the time of determining whether the coast stop condition is satisfied is lower than a predetermined value. If the gear ratio is lower than the predetermined value, the gear ratio is set. The vehicle coast stop control device according to claim 1, wherein the coast stop control device is increased. A deceleration detection unit for detecting deceleration of the vehicle;
The shift control unit determines whether or not the deceleration of the vehicle at the time when the coast stop condition is satisfied is lower than a predetermined value, and when the vehicle deceleration is lower than the predetermined value, the shift of the automatic transmission is determined. The coast stop control device for a vehicle according to any one of claims 1 to 3, wherein the ratio is increased.   The clutch engagement control unit sets a target value for the differential rotation, and controls an engagement force of the lockup clutch so that an actual differential rotation approaches the target value. The vehicle coast stop control device according to claim 1. Engine,
An automatic transmission,
A torque converter interposed between the engine and the automatic transmission;
An oil pump that is driven by the output of the engine to generate the hydraulic pressure of the automatic transmission;
In a vehicle comprising:
A coast stop control method for a vehicle, which executes a coast stop for stopping the engine when a predetermined coast stop condition is satisfied during deceleration traveling of the vehicle,
Determine whether the coast stop condition is satisfied,
When it is determined that the coast stop condition is satisfied, differential rotation is generated between the input element and the output element of the lockup clutch while maintaining the formation of the fastening force of the lockup clutch provided in the torque converter. Run clutch slip control,
During the execution of the clutch slip control, the gear ratio of the automatic transmission is increased more than when the coast stop condition is satisfied,
A coast stop control method for a vehicle, wherein the lockup clutch is released after the transmission ratio is increased.

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