JP7418932B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

A belt-type continuously variable transmission (CVT) is known as a transmission installed in vehicles such as automobiles.

A belt-type continuously variable transmission has a configuration in which an endless belt is wound around a primary pulley and a secondary pulley. By continuously changing the groove width of each pulley (primary pulley and secondary pulley), the diameter of the belt around each pulley can be changed, and the gear ratio (pulley ratio) can be changed steplessly and continuously. be able to. Furthermore, by changing the groove width of each pulley in steps, it is also possible to change the gear ratio in steps. Therefore, in continuously variable transmissions, in addition to normal shift control that automatically and continuously changes the gear ratio, there is also a shift control that uses a different control law from normal shift control, such as a control that automatically changes the gear ratio in stages. Step change speed control (linear speed change control) can be performed.

International Publication No. 2019/074009

In stepped transmission control, a plurality of gear ratios are discretely set as gear stages, and the gear ratios between the gear stages are not used. Therefore, even if the vehicle approaches an uphill road and the accelerator is operated for acceleration, if the engine speed after downshifting the gear (gear ratio) exceeds the rev limit (overrev), the downshift will not be performed. , there is a problem that the vehicle speed decreases due to insufficient driving force.

An object of the present invention is to provide a vehicle control device that can suppress a decrease in vehicle speed when the vehicle approaches an uphill road during stepped variable speed control.

In order to achieve the above object, a vehicle control device according to the present invention is a control device for use in a vehicle equipped with a continuously variable transmission capable of changing the gear ratio steplessly. Continuously variable speed control that changes the ratio steplessly and stepped speed control that changes the gear ratio of the continuously variable transmission step by step are selectively performed. The target input rotation speed is set as the target input rotation speed, and the gear ratio is changed steplessly so that the input rotation speed matches the target input rotation speed. When performing variable speed control, the target input rotational speed that would be set if continuously variable speed control is used is set as the lower limit guard for the target input rotational speed in stepped variable speed control, and in stepped variable speed control, the target input rotational speed is set as the lower limit guard of the gear ratio. Determine whether or not the conditions for change are met, and if the conditions are met, change the gear ratio from the current gear ratio to the gear ratio according to the conditions, and if the conditions are met. If not, it is determined whether the basic target rotation speed set from the current gear ratio and vehicle speed is less than the lower limit guard, and if the basic target input rotation speed is less than the lower limit guard, the lower limit is set. If the guard is set to the target input rotation speed and the basic target input rotation speed is greater than or equal to the lower limit guard, the basic target input rotation speed is set to the target input rotation speed and the input rotation speed is set to the target input rotation speed. Change the gear ratio to match.

According to this configuration, continuously variable speed control that changes the speed ratio of the continuously variable transmission in a stepwise manner and stepwise variable speed control that changes the speed ratio of the continuously variable transmission stepwise are selectively performed.

In continuously variable transmission control, a target input rotation speed, which is the target input rotation speed input to the continuously variable transmission, is set, and the gear ratio is changed steplessly so that the input rotation speed matches the target input rotation speed. be done.

On the other hand, in stepped transmission control, it is determined whether the conditions for changing the gear ratio are met, and if the conditions are met, the gear ratio changes from the current gear ratio to the condition. The gear ratio is changed. If the conditions for changing the gear ratio are not met, a basic target rotation speed is set from the current gear ratio and vehicle speed, and it is determined whether the basic target rotation speed is less than the lower limit guard. . When the vehicle is climbing a slope, the lower limit guard is set to the target input rotation speed in the case of continuously variable transmission control. If the basic target input rotation speed is less than the lower limit guard, the lower limit guard is set to the target input rotation speed, and if the basic target input rotation speed is greater than or equal to the lower limit guard, the basic target input rotation speed is set to the target input rotation speed. The gear ratio is changed so that the input rotation speed matches the target input rotation speed.

In continuously variable transmission control, the target input rotation speed is usually set to a larger value as the accelerator opening degree (ratio of the operation amount to the maximum operation amount of the accelerator pedal) is larger, such as a parameter corresponding to the acceleration request to accelerate the vehicle. be done. Therefore, when the accelerator pedal is depressed while the vehicle is climbing a slope, the target input rotation speed is set to a large value and the gear ratio is downshifted, ensuring a large driving force and suppressing a drop in vehicle speed. can do.

According to the present invention, it is possible to suppress a decrease in vehicle speed when the vehicle approaches an uphill road during stepped variable speed control.

FIG. 1 is a skeleton diagram showing the configuration of a drive system of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. FIG. 3 is a diagram showing the states of a clutch and a brake when the vehicle is moving forward and when the vehicle is moving backward. FIG. 2 is a collinear diagram showing the relationship between the rotational speeds (rotational speeds) of a sun gear, a carrier, and a ring gear of a planetary gear mechanism. It is a figure which shows the relationship between the belt gear ratio by a belt transmission mechanism, and the unit gear ratio of the whole transmission. FIG. 2 is a block diagram showing the configuration of a control system of a vehicle. FIG. 3 is a diagram showing the relationship between vehicle speed and target input rotation speed. It is a flowchart which shows the flow of target input rotation speed setting processing. It is a flowchart which shows the flow of a lower limit guard setting process. FIG. 3 is a diagram showing an example of a change in target input rotation speed over time.

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

<Vehicle drive system>
FIG. 1 is a skeleton diagram showing the configuration of a drive system of a vehicle 1. As shown in FIG.

The vehicle 1 is an automobile that uses an engine 2 as a driving source.

The power of the engine 2 is transmitted to a differential gear 5 via a torque converter 3 and a CVT (Continuously Variable Transmission) 4, and is transmitted from the differential gear 5 to left and right drive shafts 6L, 6R, respectively. It is transmitted to drive wheels 7L and 7R.

The engine 2 includes an E/G output shaft 11. The E/G output shaft 11 is rotated by the power generated by the engine 2.

The torque converter 3 includes a front cover 21, a pump impeller 22, a turbine runner 23, and a lock-up clutch 24. The E/G output shaft 11 is connected to the front cover 21, and the front cover 21 rotates together with the E/G output shaft 11. The pump impeller 22 is arranged on the side opposite to the engine 2 side with respect to the front cover 21. The pump impeller 22 is provided to be rotatable integrally with the front cover 21. The turbine runner 23 is disposed between the front cover 21 and the pump impeller 22 and is rotatable about a common rotational axis with the front cover 21 .

The lockup clutch 24 includes a lockup piston 25. Lockup piston 25 is provided between front cover 21 and turbine runner 23. The lockup clutch 24 is operated by the differential pressure between the oil pressure in the release oil chamber 26 between the lockup piston 25 and the front cover 21 and the oil pressure in the engagement oil chamber 27 between the lockup piston 25 and the pump impeller 22. Lockup is on (engaged)/off (released). That is, when the oil pressure in the release oil chamber 26 is higher than the oil pressure in the engagement oil chamber 27, the differential pressure causes the lockup piston 25 to separate from the front cover 21, and the lockup is turned off. When the oil pressure in the engagement oil chamber 27 is higher than the oil pressure in the release oil chamber 26, the lockup piston 25 is pressed against the front cover 21 due to the pressure difference, and the lockup piston 25 is turned on.

In the lock-up off state, when the E/G output shaft 11 is rotated, the pump impeller 22 is rotated. When the pump impeller 22 rotates, oil flows from the pump impeller 22 toward the turbine runner 23 . This oil flow is received by the turbine runner 23, and the turbine runner 23 rotates. At this time, an amplification effect of the torque converter 3 occurs, and a torque larger than the torque of the E/G output shaft 11 is generated in the turbine runner 23.

In the lockup-on state, when the E/G output shaft 11 is rotated, the E/G output shaft 11, the pump impeller 22, and the turbine runner 23 rotate together.

The CVT 4 is equipped with an input shaft 31 and an output shaft 32, and is configured to split the power input to the input shaft 31 into two paths and transmit it to the output shaft 32. ) is a transmission. In order to configure two power transmission paths, the CVT 4 includes a belt transmission mechanism 33, a front reduction gear mechanism 34, a planetary gear mechanism 35, and a split transmission mechanism 36.

The input shaft 31 is connected to the turbine runner 23 of the torque converter 3 and is provided so as to be rotatable integrally around the same rotational axis as the turbine runner 23.

The output shaft 32 is provided parallel to the input shaft 31. An output gear 37 is supported on the output shaft 32 so as not to be relatively rotatable. The output gear 37 meshes with the differential gear 5 (the ring gear of the differential gear 5).

The belt transmission mechanism 33 includes a primary shaft 41, a secondary shaft 42 provided parallel to the primary shaft 41, a primary pulley 43 supported non-rotatably on the primary shaft 41, and a pulley 43 supported non-rotatably on the secondary shaft 42. A belt 45 is provided, which is wound around the primary pulley 43 and the secondary pulley 44.

The primary pulley 43 includes a fixed sheave 51 fixed to the primary shaft 41, and a movable sheave that is disposed opposite to the fixed sheave 51 with a belt 45 interposed therebetween, and is supported by the primary shaft 41 so as to be movable in its axial direction but not relatively rotatable. 52. A cylinder 53 fixed to the primary shaft 41 is provided on the opposite side of the movable sheave 52 from the fixed sheave 51, and an oil chamber 54 is formed between the movable sheave 52 and the cylinder 53.

The secondary pulley 44 includes a fixed sheave 55 fixed to the secondary shaft 42, and a movable sheave that is disposed opposite to the fixed sheave 55 with the belt 45 interposed therebetween, and is supported by the secondary shaft 42 so as to be movable in the axial direction and non-rotatably relative to the fixed sheave 55. 56. A cylinder 57 fixed to the secondary shaft 42 is provided on the opposite side of the movable sheave 56 from the fixed sheave 55, and an oil chamber 58 is formed between the movable sheave 56 and the cylinder 57. In the direction of the rotational axis, the positional relationship between the fixed sheave 55 and the movable sheave 56 is opposite to the positional relationship between the fixed sheave 51 and the movable sheave 52 of the primary pulley 43.

In the belt transmission mechanism 33, the oil pressures supplied to the oil chamber 54 of the primary pulley 43 and the oil chamber 58 of the secondary pulley 44 are controlled, and the groove widths of the primary pulley 43 and the secondary pulley 44 are changed. The belt speed ratio (pulley ratio) is continuously and steplessly changed.

The front reduction gear mechanism 34 is configured to reverse and decelerate the power input to the input shaft 31 and transmit it to the primary shaft 41. Specifically, the front reduction gear mechanism 34 includes an input shaft gear 61 that is supported by the input shaft 31 in a relatively non-rotatable manner, has a larger diameter and a larger number of teeth than the input shaft gear 61, and is spline-fitted to the primary shaft 41. The input shaft gear 62 includes a primary shaft gear 62 that is supported relatively unrotatably by and meshes with the input shaft gear 61.

The planetary gear mechanism 35 includes a sun gear 71, a carrier 72, and a ring gear 73. The sun gear 71 is supported by the secondary shaft 42 by spline fitting so that it cannot rotate relative to the secondary shaft 42 . The carrier 72 is externally fitted onto the output shaft 32 so as to be relatively rotatable. The carrier 72 rotatably supports a plurality of pinion gears 74. The plurality of pinion gears 74 are arranged on the circumference and mesh with the sun gear 71. The ring gear 73 has an annular shape that collectively surrounds the plurality of pinion gears 74, and meshes with each pinion gear 74 from the outside in the rotational radial direction of the secondary shaft 42. Further, the output shaft 32 is connected to the ring gear 73, and the ring gear 73 is provided so as to be rotatable integrally around the same rotational axis as the output shaft 32.

The split transmission mechanism 36 is a parallel shaft gear mechanism including a split drive gear 81 and a split driven gear 82 that meshes with the split drive gear 81.

The split drive gear 81 is externally fitted onto the input shaft 31 so as to be relatively rotatable.

The split driven gear 82 is provided so as to be rotatable integrally with the carrier 72 of the planetary gear mechanism 35 about the same rotation axis. The split driven gear 82 is formed to have a smaller diameter than the split drive gear 81 and has fewer teeth than the split drive gear 81.

Further, a parking gear 83 is supported on the output shaft 32 so as to be relatively unrotatable. A parking pole (not shown) is provided around the parking gear 83. When the parking pole engages with the tooth groove of the parking gear 83, the rotation of the parking gear 83 is restricted (parking lock), and when the parking pole disengages from the tooth groove of the parking gear 83, the rotation of the parking gear 83 is restricted. Allowed (parking unlocked).

Further, the CVT 4 includes clutches C1 and C2 and a brake B1.

The clutch C1 is switched by hydraulic pressure between an engaged state in which the input shaft 31 and the split drive gear 81 are directly coupled (coupled so as to be rotatable together), and a released state in which the direct coupling is released.

Clutch C2 is switched by hydraulic pressure between an engaged state in which the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are directly coupled (coupled so as to be rotatable together), and a released state in which the direct coupling is released.

The brake B1 is switched by hydraulic pressure between an engaged state in which the carrier 72 of the planetary gear mechanism 35 is braked and a released state in which the carrier 72 is allowed to rotate.

FIG. 2 is a diagram showing the states of the clutches C1, C2 and the brake B1 when the vehicle 1 moves forward and backward. FIG. 3 is a collinear chart showing the relationship among the rotational speeds (rotational speeds) of the sun gear 71, carrier 72, and ring gear 73 of the planetary gear mechanism 35. FIG. 4 is a diagram showing the relationship between the belt speed change ratio of the belt speed change mechanism 33 and the unit speed ratio of the entire CVT 4. As shown in FIG.

In FIG. 2, "○" indicates that the clutches C1, C2 and the brake B1 are in an engaged state. "X" indicates that clutches C1, C2 and brake B1 are in a released state.

A shift lever (select lever) is provided in the cabin of the vehicle 1 at a position that can be operated by a driver. The movable range of the shift lever includes, for example, a P (parking) position, an R (reverse) position, an N (neutral) position, and a D (drive) position arranged in a line in this order.

When the shift lever is in the P position, all of the clutches C1, C2 and brake B1 are released, and the parking gear 83 is fixed, so that the P range (parking range), which is one of the shift ranges of the CVT 4, is set. configured. In addition, when the shift lever is in the N position, all clutches C1, C2 and brake B1 are released and the parking lock gear is not fixed. ) is configured. When all clutches C1, C2 and brake B1 are released, the power of the engine 2 is transmitted to the secondary shaft 42, and the secondary shaft 42 rotates, but the sun gear 71 and pinion gear 74 of the planetary gear mechanism 35 idle. , the power of the engine 2 is not transmitted to the drive wheels 7L, 7R.

When the shift lever is located at the D position, a D range (forward range), which is one of the shift ranges of the CVT 4, is configured. Power transmission modes in this D range include belt mode and split mode. The belt mode and the split mode are switched by switching between a state where the clutch C1 is engaged and a state where the clutch C2 is engaged (switching the clutches C1 and C2).

In belt mode, as shown in FIG. 2, clutch C1 and brake B1 are released and clutch C2 is engaged. As a result, the split drive gear 81 is separated from the input shaft 31, the carrier 72 of the planetary gear mechanism 35 becomes free (free rotation state), and the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are directly connected.

The power from the engine 2 input to the input shaft 31 is reversed and decelerated by the front reduction gear mechanism 34, and is transmitted to the primary shaft 41 of the belt transmission mechanism 33, causing the primary shaft 41 and the primary pulley 43 to rotate. The rotation of the primary pulley 43 is transmitted to the secondary pulley 44 via the belt 45, causing the secondary pulley 44 and the secondary shaft 42 to rotate. Since the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are directly connected, the sun gear 71, the ring gear 73, and the output shaft 32 rotate together with the secondary shaft 42. Therefore, in the belt mode, as shown in FIG. 3 and FIG. The rotation speed of the primary shaft 41) is the same as the value multiplied by the rotation speed of the primary shaft 41.

In the split mode, as shown in FIG. 2, clutch C1 is engaged and clutch C2 and brake B1 are released. As a result, the input shaft 31 and the split drive gear 81 are coupled, and the rotation of the input shaft 31 can be transmitted to the carrier 72 of the planetary gear mechanism 35 via the split drive gear 81 and the split driven gear 82. 35 sun gear 71 and ring gear 73 are separated.

The power from the engine 2 input to the input shaft 31 is increased in speed and transmitted from the split drive gear 81 to the carrier 72 of the planetary gear mechanism 35 via the split driven gear 82. The power transmitted to carrier 72 is divided and transmitted from carrier 72 to sun gear 71 and ring gear 73. The power of sun gear 71 is transmitted to primary shaft gear 62 via secondary shaft 42 , secondary pulley 44 , belt 45 , primary pulley 43 and primary shaft 41 , and from primary shaft gear 62 to input shaft gear 61 . Therefore, in the belt mode, the input shaft gear 61 becomes the driving gear and the primary shaft gear 62 becomes the driven gear, whereas in the split mode, the primary shaft gear 62 becomes the driving gear and the input shaft gear 61 becomes the driven gear. .

Since the gear ratio between the split drive gear 81 and the split driven gear 82 is constant and unchangeable (fixed), in the split mode, if the power input to the input shaft 31 is constant, the rotation of the carrier 72 of the planetary gear mechanism 35 is constant. is held at a constant speed. Therefore, when the belt gear ratio is increased, the rotation speed of the sun gear 71 of the planetary gear mechanism 35 decreases, so as shown by the broken line in FIG. goes up. As a result, in the split mode, as shown in FIG. 4, the greater the belt gear ratio of the belt transmission mechanism 33, the smaller the unit gear ratio of the CVT 4 becomes. The ratio of the amount of change in the unit gear ratio to the amount of change) is lower than that in the belt mode.

The engine driving force that rotates the output shaft 32 is transmitted to the differential gear 5 via the output gear 37, and from the differential gear 5 to the drive wheels 7L, 7R via the left and right drive shafts 6L, 6R. This causes the drive wheels 7L, 7R to rotate in the forward direction.

When the shift lever is in the R position, an R range (reverse range), which is one of the shift ranges of the CVT 4, is configured. In the R range, as shown in FIG. 2, clutches C1 and C2 are released and brake B1 is engaged. As a result, the split drive gear 81 is disconnected from the input shaft 31, the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are disconnected, and the carrier 72 of the planetary gear mechanism 35 is braked.

The power from the engine 2 that is input to the input shaft 31 is reversed and decelerated by the front reduction gear mechanism 34, and is transmitted to the primary shaft 41 of the belt transmission mechanism 33, and from the primary shaft 41 to the primary pulley 43, belt 45, and secondary It is transmitted to the secondary shaft 42 via the pulley 44, and rotates the sun gear 71 of the planetary gear mechanism 35 together with the secondary shaft 42. Since the carrier 72 of the planetary gear mechanism 35 is braked, when the sun gear 71 rotates, the ring gear 73 of the planetary gear mechanism 35 rotates in the opposite direction to the sun gear 71. The rotational direction of the ring gear 73 is opposite to the rotational direction of the ring gear 73 during forward movement (belt mode and split mode). Then, the output shaft 32 rotates together with the ring gear 73. The rotation of the output shaft 32 is transmitted to the differential gear 5 via the output gear 37, and from the differential gear 5 to the drive wheels 7L, 7R via the left and right drive shafts 6L, 6R. This causes the drive wheels 7L, 7R to rotate in the backward direction.

When the vehicle 1 is moving forward, the rotation speed of the sun gear 71 and the ring gear 73 match due to the direct connection between the sun gear 71 and the ring gear 73 of the planetary gear mechanism 35, whereas when the vehicle 1 is moving backward, the rotation speed of the sun gear 71 and the ring gear 73 are the same. Due to the configuration, the rotational speed of ring gear 73 is always lower than the rotational speed of sun gear 71. Therefore, in the R range, the gear ratio is larger than the maximum pulley ratio, and if the maximum pulley ratio is configured in the D and R ranges, the gear ratio will be larger when the vehicle 1 is traveling backwards than when moving forward. Therefore, the power output from the output shaft 32 increases.

<Vehicle control system>
FIG. 5 is a block diagram showing the configuration of the control system of the vehicle 1. As shown in FIG.

The vehicle 1 is equipped with a plurality of ECUs (Electronic Control Units). Each ECU includes a microcomputer (microcontroller unit), and the microcomputer includes, for example, a CPU, a nonvolatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory). The plurality of ECUs are connected to enable bidirectional communication using a CAN (Controller Area Network) communication protocol. FIG. 5 shows one ECU 91 among the plurality of ECUs.

The unit including the torque converter 3 and CVT 4 is equipped with a hydraulic circuit 92 for supplying hydraulic pressure to each part. The ECU 91 controls various valves included in the hydraulic circuit 92 to control the speed change of the CVT 4 and the like.

Various sensors necessary for control are connected to the ECU 91, and detection signals from the various connected sensors are input. The sensors connected to the ECU 91 include, for example, an accelerator sensor 93 that outputs a detection signal according to the amount of operation of the accelerator pedal, and a pulse signal that detects a pulse signal synchronized with the rotation of a rotating body that rotates as the vehicle 1 travels. A vehicle speed sensor 94 that outputs a signal is included. The ECU 91 determines the accelerator opening degree, which is the ratio of the current operation amount to the maximum operation amount of the accelerator pedal, from the detection signal of the accelerator sensor 93. Further, the ECU 91 determines the frequency of the detection signal (pulse signal) from the detection signal of the vehicle speed sensor 94, and converts the frequency into the vehicle speed.

<Shift control>
FIG. 6 is a diagram showing the relationship between vehicle speed and target input rotation speed.

When the shift lever is located at the D position and the shift range of the CVT 4 is set to the D range, the ECU 91 executes shift control to automatically change the gear ratio of the CVT 4. In the speed change control, continuously variable speed control (normal control) and stepped speed change control (linear speed change control) are selectively executed. Switching between the continuously variable speed control and the stepped variable speed control may be set manually by the driver operating a switch, but it may be set automatically according to the manner in which the driver operates the accelerator. For example, normally continuously variable speed control is performed, and if the driver's acceleration request is determined from the manner of accelerator operation, and the acceleration request is determined, the continuously variable speed control is automatically switched to stepped variable speed control, If a state in which an acceleration request is not determined continues for a predetermined period of time, the stepped variable speed control is automatically switched to the continuously variable speed control.

In the continuously variable transmission control, the gear ratio of the CVT 4 is changed continuously. The nonvolatile memory of the ECU 91 stores a shift diagram for continuously variable shift control. This shift diagram shows the accelerator opening, vehicle speed, and normal control target input rotational speed, which is the target input rotational speed for continuously variable transmission control, as shown in FIG. It defines the relationship between The target input rotation speed is a target value of the rotation speed input to the input shaft 31 of the CVT 4. In continuously variable transmission control, the normal control target input rotation speed is set according to the accelerator opening degree and vehicle speed from the shift diagram, and the target input rotation speed is set based on the normal control target input rotation speed by the target input rotation speed setting process described later. The rotation speed is set. Furthermore, a target gear ratio, which is a target of the unit gear ratio that makes the rotational speed input to the input shaft 31 match the target input rotational speed, is determined, and a target gear ratio of the belt according to the target gear ratio is set. The belt transmission ratio is then changed toward the target.

Continuously variable transmission control allows the gear ratio to be continuously changed according to changes in accelerator opening and vehicle speed so that the engine 2 rotation speed is within a highly efficient rotation range, resulting in low fuel consumption. It can be realized.

In the stepped transmission control, a plurality of gear ratios are set discretely, and the gear ratio of the CVT 4 is changed between the plurality of gear ratios. As the plurality of gear ratios, for example, gear ratios corresponding to the first to seventh gears in an AT (Automatic Transmission) are set. The nonvolatile memory of the ECU 91 stores a shift diagram for stepped variable speed control. This shift diagram defines the accelerator opening degree and vehicle speed, which are the conditions for changing the gear ratio. The shift diagram for stepped transmission control includes an upshift diagram that defines the conditions for upshifting from N gear (N: 1 to 6) to N+1 gear, and an upshift diagram that defines the conditions for upshifting from N gear (N: 1 to 6) to N+1 gear. A downshift diagram defining conditions for downshifting is included. In stepped transmission control, a target gear ratio is set according to the accelerator opening degree and vehicle speed from a transmission diagram.

If the current gear ratio and the target gear ratio are different, a predicted value of the target input rotation speed after changing to the target gear ratio is determined. If the predicted value does not exceed the maximum engine rotation speed (rev limit) which is the maximum value of the rotation speed of the engine 2, the target input rotation speed after changing to the target gear ratio is set as the linear control target input rotation speed. Then, a target input rotation speed is set based on the linear control target input rotation speed by a target input rotation speed setting process that will be described later. In this case, normally, the linear control target input rotation speed is directly set as the target input rotation speed, and by changing the belt speed ratio, the current speed ratio is changed to the target speed ratio. By changing the current gear ratio to the target gear ratio, the number of rotations input to the input shaft 31 matches the target input number of rotations.

On the other hand, if the predicted value of the target input rotation speed after changing to the target gear ratio exceeds the maximum engine rotation speed, the current target input rotation speed is set as the linear control target input rotation speed. Then, by the target input rotation speed setting process, the target input rotation speed is set based on the linear control target input rotation speed. Changing the gear ratio in this case will be described later together with the target input rotation speed setting process.

In stepped transmission control, the gear ratio is fixed until the upshift or downshift conditions are met, so it is possible to obtain linear acceleration response or acceleration feeling in response to accelerator operation.

In the belt mode, the belt speed ratio takes a value within a range whose lower limit is a switching value equal to the split gear ratio, which is the gear ratio of the split drive gear 81 and the split driven gear 82. In the split mode, the belt speed ratio takes a value within the switching value Takes a value within a range with an upper limit of . If the target gear ratio is set to a value that straddles the switching value, that is, if the target gear ratio is set to be less than the switching value in belt mode, or if the target gear ratio is greater than the switching value in split mode. In this case, changing the gear ratio involves switching between belt mode and split mode. When switching between the belt mode and the split mode is involved, the ECU 91 performs control to change the belt speed ratio and engage/disengage the clutches C1 and C2.

<Target input rotation speed setting process>
FIG. 7 is a flowchart showing the flow of target input rotation speed setting processing.

In the target input rotation speed setting process, first, it is determined whether stepped variable speed control is being performed (step S1). If the stepped variable speed control is in progress (YES in step S1), a linear control target input rotation speed is set, and the linear control target input rotation speed is set as a basic target input rotation speed (step S2). If stepless speed control is not in progress but stepless speed control is in progress (NO in step S1), the normal control target input rotation speed is set, and the normal control target input rotation speed is set as the basic target input rotation speed. (Step S3).

Once the basic target input rotation speed is set, it is then determined whether the basic target input rotation speed is less than the lower limit guard (step S4). The lower limit guard is set by lower limit guard setting processing. The lower limit guard setting process will be described later.

If the basic target input rotation speed is less than the lower limit guard (YES in step S4), the value of the lower limit guard is set to the target input rotation speed (step S5), and the target input rotation speed setting process is ended.

If the basic target input rotation speed is not less than the lower limit guard, that is, if the basic target input rotation speed is greater than or equal to the lower limit guard (NO in step S4), whether the basic target input rotation speed exceeds (is larger than) the upper limit guard? is determined (step S6). The upper limit guard is normally set to the maximum engine speed. For example, if the oil temperature of CVT 4 exceeds a predetermined temperature, if ABS (Antilock Brake System) control is in place to prevent the wheels from locking, if engine 2 misfires (engine stall), or some other abnormality occurs. If this occurs, the upper limit guard is set to a value lower than the maximum engine speed in order to protect each part of the vehicle 1.

If the basic target input rotation speed exceeds the upper limit guard (YES in step S6), the value of the upper limit guard is set to the target input rotation speed (step S7), and the target input rotation speed setting process is ended.

If the basic target input rotation speed does not exceed the upper limit guard, that is, if the basic target input rotation speed is below the upper limit guard (NO in step S6), the basic target input rotation speed is set to the target input rotation speed (step S8), the target input rotation speed setting process is ended.

<Lower limit guard setting process>
FIG. 8 is a flowchart showing the flow of the lower limit guard setting process.

The lower limit guard setting process is performed by the ECU 91.

In the lower limit guard setting process, it is determined whether the vehicle 1 is climbing a slope (step S11). Further, it is determined whether or not stepped variable speed control is being performed (step S11). Various methods can be used for determining whether the vehicle is uphill. For example, the lower limit value of the acceleration of the vehicle 1 is predicted from the accelerator opening degree and the vehicle speed, and if the time differential value of the vehicle speed is less than the lower limit value, it is determined that the vehicle 1 is climbing a slope, and the time differential value of the vehicle speed is is greater than or equal to the predicted lower limit value, it can be determined that the vehicle 1 is not climbing a slope. In addition, the difference between the acceleration obtained from the detection signal of the acceleration sensor mounted on the vehicle 1 and the time differential value of the vehicle speed is calculated, and the road surface slope is estimated from the difference. , it is determined that the vehicle 1 is climbing a slope, and if the road surface slope is less than the certain value, it can be determined that the vehicle 1 is not climbing a slope.

When the vehicle 1 is climbing a slope and is under stepped variable speed control (YES in step S11), normal control is set when continuously variable speed control is being performed based on the accelerator opening and vehicle speed at that time. The target input rotation speed is determined. Then, it is determined whether the normal target input rotation speed is larger than the maximum value of another lower limit guard (step S12). Other lower limit guards are lower limit guards other than the lower limit guard set in this lower limit guard setting process. Other lower limit guards are set to the lowest rotation speed at which misfire of the engine 2 does not occur, and are set under various conditions such as when the water temperature of the engine 2 is low, when the vehicle 1 is climbing a slope, when the accelerator opening is 0, etc. will be changed accordingly. The maximum value of other lower limit guards refers to the maximum value of other lower limit guards that are currently set. Therefore, the normal target input rotational speed usually exceeds the maximum value of the other lower limit guards.

If the normal target input rotation speed is larger than the maximum value of the other lower limit guards (YES in step S12), the normal control target input rotation speed is set to the lower limit guard (step S13), and the lower limit guard setting process is ended. .

If the normal control target input rotation speed is less than or equal to the maximum value of the other lower limit guards (NO in step S12), the maximum value of the other lower limit guards is set as the lower limit guard (step S14), and the lower limit guard setting process ends. be done.

When the vehicle 1 approaches an uphill road and the driver depresses the accelerator pedal in order to accelerate the vehicle 1, an acceleration request is determined and the speed change control is switched from continuously variable speed control to stepped speed control. Since the vehicle 1 is climbing a slope and is under stepped variable speed control, the normal control target input rotation speed is set to the lower limit guard unless the normal control target input rotation speed is equal to or less than the maximum value of the other lower limit guard. .

For example, as shown in FIG. 6, while vehicle 1 is traveling at a gear ratio and vehicle speed V corresponding to second gear, vehicle 1 approaches an uphill road, the driver depresses the accelerator pedal, and the vehicle changes from second gear to When the conditions for downshifting to 1st gear are met, the gear ratio corresponding to 1st gear is set as the target gear ratio, and the current target input rotation speed (=actual target input rotation speed) R1 and the target gear ratio are used. , a predicted value R2 of the target input rotation speed after changing to the target gear ratio is determined. In this case, the predicted value R2 exceeds the maximum engine rotation speed, so the current target input rotation speed R1 is set as the linear control target input rotation speed. In the target input rotation speed setting process, the linear control target input rotation speed R1 is set to the basic target input rotation speed, and it is determined whether the basic target input rotation speed R1 is less than a lower limit guard. At this time, the normal control target input rotation speed R3 is set to the lower limit guard, and the basic target input rotation speed R1 is less than the normal control target input rotation speed R3, so the target input rotation speed is limited by the lower limit guard. The normal control target input rotation speed R3 is set as the target input rotation speed.

In this case, a target gear ratio, which is the target of the unit gear ratio that makes the rotational speed input to the input shaft 31 match the target input rotational speed R3, is determined, and a target gear ratio of the belt according to the target gear ratio is set. Ru. Then, the belt speed ratio is changed (downshifted) toward the target, and control is performed to engage/disengage the clutches C1 and C2 as necessary.

<Effect>
As described above, unlike conventional transmission control, even during stepped transmission control, when climbing a slope where driving force is required, the target input rotation speed is raised from R1 to R3, and the CVT4 unit transmission The ratio is downshifted. Thereby, a large driving force can be ensured, and a decrease in the vehicle speed of the vehicle 1 when climbing a slope can be suppressed.

FIG. 9 is a diagram showing an example of a change in the target input rotation speed over time.

When the target input rotation speed is set to the normal control target input rotation speed, which is the lower limit guard, while the vehicle 1 is climbing a slope and during the stepped variable speed control, the normal control target input rotation speed is set as the final target input rotation speed. As shown by the dotted chain line, the target input rotation speed may be increased to the final target input rotation speed over time. Further, the amount of time change in the target input rotation speed may be changed in stages until the target input rotation speed is raised to the final target input rotation speed.

By performing such transient control of the target input rotation speed, sudden changes in the target input rotation speed can be avoided and drivability can be ensured.

<Modified example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other forms.

For example, in the above-described embodiment, a configuration was taken up in which power is transmitted by branching into the first power transmission path passing through the split transmission mechanism 36 and the second power transmission path passing through the belt transmission mechanism 33, but the split transmission The mechanism 36 is not limited to a parallel shaft gear mechanism including the split drive gear 81 and the split driven gear 82, but may be a mechanism other than a gear mechanism such as a belt mechanism. When a belt mechanism is employed, the belt mechanism may have a fixed speed ratio or may have a variable speed ratio.

Further, the automatic transmission may be a normal CVT that does not include the split transmission mechanism 36, that is, it is not a power split type.

In addition, various design changes can be made to the above-described configuration within the scope of the claims.

1: Vehicle 4: CVT
91: ECU (control unit)

Claims (1)

A control device for use in a vehicle equipped with a continuously variable transmission that can change the gear ratio steplessly, and in which engine power is transmitted to drive wheels via the continuously variable transmission,
selectively performing continuously variable speed control that changes the speed ratio of the continuously variable transmission in a stepwise manner, and stepped variable speed control that changes the speed ratio of the continuously variable transmission stepwise;
In the continuously variable transmission control, a target input rotation speed that is a target of the input rotation speed input to the continuously variable transmission is set, and the gear ratio is adjusted so that the input rotation speed matches the target input rotation speed. Change steplessly,
In the stepped transmission control, the gear ratio is fixed until a condition for upshifting or downshifting the gear ratio is met, and when the condition is met, the target input rotation speed is set and the input speed is changed. changing the gear ratio so that the rotation speed matches the target input rotation speed,
In the continuously variable transmission control, a normal control target input rotation speed is set according to an accelerator opening degree and a vehicle speed, the normal control target input rotation speed is set as a basic target input rotation speed, and the basic target input rotation speed is set. If it is less than the lower limit guard, the lower limit guard is set to the target input rotation speed, and if the basic target input rotation speed is equal to or higher than the lower limit guard, the basic target input rotation speed is set to the target input rotation speed. Set to rotation speed,
In the stepped transmission control, a target gear ratio is set according to the accelerator opening degree and the vehicle speed, a predicted value of the target input rotation speed after changing to the target gear ratio is determined, and the predicted value is set as the rev limit of the engine. If the predicted value does not exceed the rev limit, the target input rotation speed after changing to the target gear ratio is set as the linear control target input rotation speed, and if the predicted value exceeds the rev limit, the current target input rotation speed is set to the linear control target input rotation speed. If the basic target input rotation speed is less than the lower limit guard, the lower limit guard is set to the target input rotation speed. setting the basic target input rotation speed to the input rotation speed, and if the basic target input rotation speed is equal to or higher than the lower limit guard, setting the basic target input rotation speed to the target input rotation speed;
Execute a lower limit guard setting process to set the lower limit guard,
In the lower limit guard setting process, when the vehicle is climbing a slope and the stepped variable speed control is being performed, the normal control target input rotation speed is determined according to the accelerator opening and vehicle speed at that time, and the If the normal control target input rotation speed is larger than the maximum value of other lower limit guards other than the lower limit guard set in the lower limit guard setting process, the normal control target input rotation speed is set to the lower limit guard, and the is not climbing a slope or is not performing the stepped transmission control, or is the vehicle climbing a slope and performing the stepped transmission control, but the accelerator opening and The vehicle control device sets the maximum value of the other lower limit guard to the lower limit guard when the normal control target input rotation speed determined according to the vehicle speed is less than or equal to the maximum value of the other lower limit guard.

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