JP7556321B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

Conventionally, there is known a lock-up clutch control device that selects a map to be used to determine whether or not to engage a lock-up clutch depending on whether or not the motor is used as a driving force source for a torque converter attached to the transmission of a vehicle that has a driving force source that can be switched between an engine and a motor (see, for example, Patent Document 1).

JP 2000-145951 A

In general, engine assistance by an electric motor is assumed to be performed continuously with a certain amount of torque. However, if the electric motor assists continuously, the power consumption for the assist becomes excessive. In order to improve the fuel efficiency of an engine that outputs power to an automatic transmission via a fluid coupling having a lockup clutch, in a configuration in which the lockup clutch is engaged, it is desirable to use the motor more efficiently to engage the lockup clutch, taking into account the fact that the power consumed for the assist is charged by the engine.

The present invention aims to provide a vehicle control device that can engage a lock-up clutch by using an electric motor more efficiently than when the electric motor is continuously assisted.

A vehicle control device according to one aspect of the present invention is a vehicle control device having as its drive source an engine that outputs power to an automatic transmission via a fluid coupling having a lock-up clutch, and an electric motor that is capable of assisting the power, and is provided with a vehicle speed acquisition unit that acquires the vehicle speed of the vehicle, an output torque acquisition unit that acquires the output torque of the engine, a required torque acquisition unit that acquires the required torque required of the drive source, a lock-up control unit that engages the lock-up clutch when the output torque is equal to or less than a preset first torque threshold based on the vehicle speed and the output torque, and a drive source control unit that controls the engine and the electric motor to output the required torque, and when the lock-up clutch is not engaged, the drive source control unit executes assist control that controls the electric motor to output an assist torque equal to or greater than a torque value of the required torque that exceeds the first torque threshold.

In a vehicle control device according to one aspect of the present invention, when the lockup clutch is not engaged, assist control is executed, and the electric motor outputs an assist torque equal to or greater than a torque value that exceeds a first torque threshold among the required torque. Since the engine only needs to output a torque obtained by subtracting the assist torque from the required torque, the lockup clutch is engaged when the engine output torque is equal to or less than the first torque threshold. As a result, until a predetermined condition for disengaging the lockup clutch is satisfied, for example, the electric motor does not need to assist in engaging the lockup clutch. Therefore, according to the present invention, it is possible to engage the lockup clutch by using the electric motor more efficiently than when the electric motor is continuously assisted.

In one embodiment, the drive source control unit may calculate the assistable torque based at least on the maximum torque of the electric motor, and perform assist control when the assist torque is less than the assistable torque. In this case, assist control can be performed with the assist torque that the electric motor can realistically output.

In one embodiment, the lockup control unit may disengage the lockup clutch when the output torque exceeds a second torque threshold value that is greater than a preset first torque threshold value when the lockup clutch is engaged, based on the vehicle speed and the output torque, and the drive source control unit may calculate the difference between the second torque threshold value and the first torque threshold value at the corresponding vehicle speeds as the assistable torque. In this case, when the lockup clutch is engaged by the assist control, the lockup clutch remains engaged until the output torque exceeds the second torque threshold value, making it possible to eliminate the need for electric motor assistance for engaging the lockup clutch.

In one embodiment, the drive source control unit may calculate the assistable torque based on the map information and the vehicle's position information, according to the fuel economy effect of the assist control when the vehicle travels along the planned travel route on the map. In this case, for example, the assist control can be executed so as to obtain a preset fuel economy effect.

In one embodiment, the drive source control unit may calculate the fuel economy effect of the assist control based on the positive impact on fuel economy caused by the engagement of the lockup clutch when it is assumed that the assist control is performed, and the negative impact on fuel economy caused by the power consumption of the electric motor when it is assumed that the assist control is performed. In this case, the assist control can be performed taking into consideration in advance the charging of the power consumed by the assist with the engine.

According to the present invention, it is possible to use the electric motor more efficiently to engage the lock-up clutch compared to when the electric motor is continuously assisted.

1 is a diagram showing a configuration of a vehicle equipped with a vehicle control device according to an embodiment; FIG. 2 is a diagram showing a functional configuration of a control device for the vehicle shown in FIG. 1 . FIG. 4 is a diagram illustrating an example of an assist torque. FIG. 4 is a diagram showing an example of an assistable torque. 4 is a timing chart showing an example of the operation of the assist control. 13 is a flowchart illustrating an example of an assist control process. 6 is a flowchart showing an example of a process for determining whether or not to perform assist control. FIG. 11 is a diagram showing an example of fuel efficiency based on map information. 10 is a flowchart showing an example of a process for determining whether or not to execute assist control in consideration of fuel efficiency effect.

The following describes an embodiment of the present invention with reference to the drawings. In the following description, the same or equivalent elements are designated by the same reference numerals, and duplicate descriptions are omitted.

Figure 1 is a diagram showing the configuration of a vehicle equipped with a vehicle control device of one embodiment. The vehicle 1 shown in Figure 1 is a hybrid vehicle equipped with an engine 2 and a motor generator (electric motor) 3 as driving power sources. The vehicle 1 can run while appropriately switching between the driving power sources to be used and appropriately changing the ratio of driving power from each driving power source. The vehicle 1 is not particularly limited, but may be a mild hybrid vehicle as an example.

The vehicle 1 includes an engine 2, a motor generator 3, an automatic transmission 4, a battery 6, and an inverter 7. The engine 2 is, for example, a diesel engine. The motor generator 3 is rotated by the power of the battery 6 to drive the vehicle 1. The motor generator 3 functions as a generator for charging the battery 6.

The location where the motor generator 3 is provided is not limited to the location shown in FIG. 1, and it may be provided so long as it is capable of assisting the output (power) of the engine 2. Assisting the engine 2 with the motor generator 3 means that the output from the motor generator 3 is transmitted to the wheels 8 while the vehicle 1 is traveling, thereby making it possible to reduce the output of the engine 2 compared to when the wheels 8 are driven by the output only from the engine 2. The motor generator 3 may be, for example, built into the automatic transmission 4, or may be provided so as to be capable of driving the downstream side of the automatic transmission 4 in the direction of the flow of driving force (for example, a propeller shaft or a drive shaft, etc.).

The operation of the engine 2 is controlled by an ECU [Electronic Control Unit] 10 that is connected to each other so that they can communicate with each other. The operation of the motor generator 3 is controlled by an ECU 10 that is connected to each other so that they can communicate with each other via an inverter 7.

The automatic transmission 4 transmits the driving force of the engine 2 and the motor generator 3 to the wheels 8 via a propeller shaft, a differential gear, a drive shaft, etc. The automatic transmission 4 is not particularly limited, but may be configured as, for example, a stepped mechanical automatic transmission. The automatic transmission 4 includes a torque converter 5 having a lock-up clutch 5a, and the engine 2 and the motor generator 3 are connected to each other via the torque converter 5. In other words, the engine 2 outputs power to the automatic transmission 4 via the torque converter 5 having the lock-up clutch 5a. The motor generator 3 is provided so as to be able to assist the power output from the engine 2 to the automatic transmission 4. The operation of the automatic transmission 4 and the direct engagement state of the lock-up clutch 5a of the torque converter 5 are controlled by an ECU 10 which is connected to each other so as to be able to communicate with each other.

The torque converter 5 is composed of an impeller 5b and a turbine 5c in addition to the lockup clutch 5a. In the torque converter 5, the engagement state of the lockup clutch 5a can be changed in response to a control signal from the ECU 10. The engagement state includes a state in which the lockup clutch 5a is engaged (so-called direct engagement) and a state in which the lockup clutch 5a is disengaged (so-called non-direct engagement). When the engagement state is non-direct engagement, the power from the engine 2 is output to the automatic transmission 4 via the impeller 5b and turbine 5c as a fluid coupling. When the engagement state is direct engagement, the power from the engine 2 is output to the automatic transmission 4 via the engaged lockup clutch 5a. The power transmission efficiency is superior when the engagement state is direct engagement than when the engagement state is non-direct engagement.

The battery 6 is formed by connecting multiple secondary batteries together inside it. Various secondary batteries such as lithium ion batteries can be used as the battery 6. The inverter 7 converts the power input from the battery 6 into AC and outputs the converted power to the motor generator 3.

Next, the configuration of the vehicle control device 100 will be described. FIG. 2 is a diagram showing the functional configuration of the vehicle control device 100 of FIG. 1. The vehicle control device 100 is a device for controlling the transmission of driving force of the vehicle 1. The vehicle control device 100 performs integrated control of the lockup of the lockup clutch 5a and the assist of the engine 2 by the motor generator 3.

The vehicle control device 100 has an ECU 10. The ECU 10 is configured by a computer including, for example, a CPU [Central Processing Unit], a ROM [Read Only Memory], and a RAM [Random Access Memory]. The ECU 10 performs comprehensive control for causing the vehicle 1 to function as a hybrid vehicle, for example. The ECU 10 may be configured by being divided into multiple ECU units.

The ECU 10 is connected to an engine speed sensor 21, an accelerator opening sensor 22, a vehicle speed sensor 23, a map database 24, and a GNSS receiver 25.

The engine speed sensor 21 and the accelerator opening sensor 22 are sensors for acquiring state quantities of the engine 2. The engine speed sensor 21 is a detector that detects, for example, the rotation speed of the crankshaft of the engine 2 as the engine speed. The engine speed sensor 21 transmits a detection signal of the detected engine speed to the ECU 10. The accelerator opening sensor 22 is a detector that detects the accelerator opening of the accelerator pedal. The accelerator opening sensor 22 transmits a detection signal of the detected accelerator opening to the ECU 10.

The vehicle speed sensor 23 is a detector that detects the speed of the vehicle 1. For example, a sensor that is provided on the axle of the wheel 8 and detects the rotational speed of the wheel 8 is used as the vehicle speed sensor. The vehicle speed sensor 23 transmits the detected vehicle speed information to the ECU 10.

The map database 24 is a database that stores map information. The map database 24 is formed, for example, in a storage medium such as a HDD [Hard Disk Drive] mounted on the vehicle. The map information includes road position information, road shape information (e.g., curves, types of straight sections, radius of curvature of curves, intersection shapes, lane widths, road gradients, etc.), intersection and branch point position information, and structure position information. The map information may also include information such as speed limits (e.g., legal maximum speeds). The map information may also include various types of traffic regulation information (such as information on sections where lane changes are possible and sections where lane changes are not possible). The map database 24 may also be formed in a computer in a facility such as a management center that can communicate with the vehicle 1.

The GNSS receiver 25 measures the position of the vehicle 1 on a map (e.g., the latitude and longitude of the vehicle 1) by receiving signals from three or more GNSS satellites. The GNSS receiver 25 transmits the measured position information of the vehicle 1 to the ECU 10.

The ECU 10 has, as its functional configuration, an engine state quantity acquisition unit (output torque acquisition unit, required torque acquisition unit) 11, a memory unit 12, a lock-up control unit 13, and a drive source control unit 14.

The engine state quantity acquisition unit 11 acquires the engine speed and the accelerator opening as engine state quantities based on the detection results of the engine speed sensor 21 and the accelerator opening sensor 22. The engine state quantity acquisition unit 11 acquires the output torque of the engine 2, for example, by a known method, based on the engine speed and the accelerator opening. The output torque of the engine 2 here is an estimated torque value that the engine 2 is likely to be outputting, which is obtained, for example, from a pre-stored map or the like.

The engine state quantity acquisition unit 11 acquires the required torque required of the drive source as an engine state quantity, for example, by a known method, based on the engine speed and the accelerator opening. The required torque required of the drive source is, for example, the output torque of the drive source necessary for the vehicle 1 to run, and is the required value of the combined torque of the output torque of the engine 2 and the motor generator 3.

The memory unit 12 stores various information that is set in advance. The memory unit 12 is, for example, the ROM of the ECU 10. The memory unit 12 stores the above-mentioned map of the output torque of the engine 2, the lock-up map described below, and the like. In this embodiment, the lock-up map is stored separately for each gear stage of the automatic transmission 4.

The lockup control unit 13 controls the engagement state of the lockup clutch 5a based on the vehicle speed of the vehicle 1 and the output torque of the engine 2. The lockup control unit 13 engages the lockup clutch 5a when the output torque of the engine 2 is equal to or less than a preset ON torque (first torque threshold) based on the vehicle speed of the vehicle 1 and the output torque of the engine 2. The ON torque is a torque threshold for determining whether or not to engage the lockup clutch 5a. As an example, the ON torque here is preset as a map with the vehicle speed of the vehicle 1 on the horizontal axis and the output torque of the engine 2 on the vertical axis (see the dashed line Lon in FIG. 3). The lockup control unit 13 functions as a vehicle speed acquisition unit that acquires the vehicle speed of the vehicle 1 based on the detection result of the vehicle speed sensor 23.

The lockup control unit 13 disengages the lockup clutch 5a when the output torque of the engine 2 exceeds a preset OFF torque (second torque threshold) based on the vehicle speed of the vehicle 1 and the output torque of the engine 2 while the lockup clutch 5a is engaged. The OFF torque is a torque threshold for determining whether or not to disengage the lockup clutch 5a. The OFF torque is greater than the ON torque. As an example, the OFF torque here is preset as a map with the vehicle speed of the vehicle 1 on the horizontal axis and the output torque of the engine 2 on the vertical axis (see the dashed line Loff in FIG. 4).

In this embodiment, the ON torque and OFF torque used by the lockup control unit 13 are those stored in advance in the storage unit 12. In other words, even if the degree of assistance of the motor generator 3 changes, the ON torque and OFF torque are used without being changed.

The drive source control unit 14 controls the engine 2 and the motor generator 3 to output the required torque. As described above, the required torque is the required value of the combined torque of the output torques of the engine 2 and the motor generator 3. The drive source control unit 14 controls the engine 2 and the motor generator 3 so that the sum of the output torque of the engine 2 and the output torque of the motor generator 3 becomes the required torque.

When the lock-up clutch 5a is not engaged, the drive source control unit 14 controls the motor generator 3 so that the output torque of the engine 2 is such that the lock-up clutch 5a can be engaged. When the lock-up clutch 5a is not engaged, the drive source control unit 14 executes assist control to control the motor generator 3 so that it outputs assist torque. The assist torque is a required torque distribution value to the motor generator 3. The assist torque has a torque value equal to or greater than the torque value of the required torque that exceeds the ON torque.

Figure 3 is a diagram showing an example of assist torque. In Figure 3, the horizontal axis is the vehicle speed of the vehicle 1, and the vertical axis is the engine torque (the output torque of the engine 2 input to the torque converter 5). In Figure 3, the engine 2 is operated at the vehicle speed of the vehicle 1 and the output torque Tout corresponding to the operating point P1. At the operating point P1 in Figure 3, the motor generator 3 has not yet assisted, so the output torque Tout is equal to the required torque Treq.

As shown in FIG. 3, as an example, the drive source control unit 14 calculates the assist torque Ta as the difference between the output torque Tout of the engine 2 and the ON torque Ton at a corresponding vehicle speed V1. The ON torque Ton is the value of the dashed line Lon representing the ON torque at the vehicle speed V1.

The drive source control unit 14 calculates, for example, the assistable torque. The assistable torque is the upper limit torque value at which the motor generator 3 can realistically output the assist torque. The drive source control unit 14 calculates the assistable torque based at least on the maximum torque of the motor generator 3. The maximum torque of the motor generator 3 is, for example, the instantaneous maximum torque or rated maximum torque in the design, or the maximum torque after being limited according to the vehicle speed, etc.

Figure 4 is a diagram showing an example of the assistable torque. In Figure 4, the horizontal and vertical axes are the same as those in Figure 3. As shown in Figure 4, the drive source control unit 14 calculates, as an example, the assistable torque Tb, the difference between the OFF torque Toff and the ON torque Ton at a corresponding vehicle speed V1. The OFF torque Toff is the value of the dashed line Loff representing the OFF torque at the vehicle speed V1. Note that in Figure 4, the area sandwiched between the OFF torque Toff and the ON torque Ton is the so-called lock-up hysteresis. In other words, the assistable torque Tb is equal to the torque value of the lock-up hysteresis width.

The drive source control unit 14 executes assist control, for example, when the assist torque is less than the assistable torque. The examples in Figures 3 and 4 correspond to the case where the assist torque Ta is less than the assistable torque Tb. Therefore, the drive source control unit 14 executes assist control so that the motor generator 3 outputs the assist torque Ta to assist the output of the engine 2.

As a result of the execution of the assist control, the output torque that the engine 2 must output to satisfy the required torque as the total torque of the drive sources is reduced by the assist torque Ta of the motor generator 3. As can be seen from the two-dot chain line arrow in FIG. 4, the engine 2 that was operating at operating point P1 is now operating at operating point P2. At operating point P2, the output torque of the engine 2 is equal to or lower than the ON torque Ton, so the lockup control unit 13 engages the lockup clutch 5a, which was in a non-directly engaged state.

Figure 5 is a timing chart showing an example of the operation of the assist control. The horizontal axis of Figure 5 is time, and the vertical axis (amounts that change over time shown by solid lines) are, from the top to the bottom, engine torque, assist torque, and lock-up state, respectively.

As shown in FIG. 5, at time t0, the output torque Tout of the engine 2 exceeds the OFF torque, so the engagement state of the lockup clutch 5a is not directly connected. At time t1, the output torque Tout of the engine 2 falls below the OFF torque but exceeds the ON torque (corresponding to operating point P1 in FIG. 3). Therefore, the engagement state of the lockup clutch 5a remains not directly connected. If the output torque Tout of the engine 2 at time t1 were to be maintained without performing assist control, the engine 2 would continue to operate with the engagement state of the lockup clutch 5a remaining not directly connected.

In this regard, the assist control as described above is started at time t1, and the motor generator 3 outputs the assist torque Ta to assist the output of the engine 2. At this time, the output torque Tmg of the motor generator 3 may be smoothed by a predetermined amount so that the engine 2 can follow the torque change. As a result of the execution of the assist control, the output torque Tout of the engine 2 becomes equal to or less than the ON torque Ton, and the engagement state of the lock-up clutch 5a changes to direct engagement at time t2.

Since the engagement state of the lock-up clutch 5a has changed to direct engagement, the assistance of the engine 2 output by the motor generator 3 is reduced. At this time, the output torque Tmg of the motor generator 3 may be softened by a predetermined amount so that the engine 2 can follow the torque change.

Until the output torque Tout of the engine 2 exceeds the OFF torque Toff (time t2 to time t3), the output torque Tout of the engine 2 is within the lockup hysteresis (above the ON torque and below the OFF torque). Therefore, even if the motor generator 3 stops outputting the assist torque Ta, the engagement state of the lockup clutch 5a remains directly connected. After that, at time t3, when the output torque Tout of the engine 2 exceeds the OFF torque Toff, the engagement state of the lockup clutch 5a changes from directly connected to non-directly connected.

Next, the assist control by the ECU 10 will be described. FIG. 6 is a flowchart showing an example of the assist control process. The process shown in FIG. 6 is executed repeatedly at a predetermined calculation period while the vehicle 1 is traveling, for example.

As shown in FIG. 6, in S01, the ECU 10 determines whether or not to execute assist control by the drive source control unit 14. As a specific process of S01, the ECU 10 performs, for example, the process of determining whether or not to execute assist control shown in FIG. 7.

Figure 7 is a flowchart showing an example of the process for determining whether to execute assist control. As shown in Figure 7, in S11, the ECU 10 calculates the assist torque using the drive source control unit 14. The drive source control unit 14 calculates the assist torque by subtracting the ON torque from the output torque of the engine 2, for example, as shown in Figure 3.

In step S12, the ECU 10 calculates the assistable torque using the drive source control unit 14. The drive source control unit 14 calculates the assistable torque by subtracting the ON torque from the OFF torque, for example, as shown in FIG. 4.

In S13, the ECU 10 determines whether the assist torque is smaller than the assistable torque by the drive source control unit 14. If the drive source control unit 14 determines that the assist torque is smaller than the assistable torque (S13: YES), the ECU 10 determines in S14 to execute assist control. If the drive source control unit 14 determines that the assist torque is equal to or greater than the assistable torque (S13: NO), the ECU 10 determines in S14 not to execute assist control. After that, the ECU 10 ends the process in FIG. 7 and proceeds to S02 in FIG. 6.

In S02 of FIG. 6, the ECU 10 uses the drive source control unit 14 to make a judgment about the judgment result of S01. If the judgment result of S01 is that assist control is to be executed (S02: YES), the ECU 10 proceeds to S03. If the judgment result of S01 is that assist control is not to be executed (S02: NO), the ECU 10 ends the process of FIG. 6 and repeats the process of FIG. 6 after a predetermined calculation period.

In S03, the ECU 10 reduces the required engine torque and increases the required MG torque through the drive source control unit 14. The drive source control unit 14 reduces the required engine torque and increases the required MG torque by the amount of the assist torque calculated in S11 of FIG. 7.

In S04, the ECU 10 determines whether or not to end the assist control using the drive source control unit 14. For example, the ECU 10 determines to end the assist control when the lock-up clutch is engaged by the drive source control unit 14. If the ECU 10 determines to end the assist control (S04: YES), the process proceeds to S05. If the ECU 10 determines not to end the assist control (S04: NO), the process proceeds to S03, and the processes of S03 and S04 are repeated.

In S05, the ECU 10 increases the required engine torque and reduces the required MG torque through the drive source control unit 14. The drive source control unit 14 increases the required engine torque and reduces the required MG torque so as to return the torque that was reduced and increased in S03, respectively. After that, the ECU 10 ends the current process of FIG. 6 and repeats the process of FIG. 6 after a predetermined calculation cycle.

[Action and Effect]
As described above, according to the vehicle control device 100, when the lock-up clutch 5a is not engaged, the assist control is executed, and the motor generator 3 outputs an assist torque equal to or greater than the torque value exceeding the ON torque among the required torque. Since the engine 2 only needs to output a torque obtained by subtracting the assist torque from the required torque, the lock-up clutch 5a is engaged when the output torque of the engine 2 becomes equal to or less than the ON torque. As a result, until a predetermined condition for releasing the engagement of the lock-up clutch 5a is satisfied (i.e., until the output torque of the engine 2 exceeds the OFF torque), the assist of the motor generator 3 for engaging the lock-up clutch 5a is not required. Therefore, according to the vehicle control device 100, it is possible to engage the lock-up clutch 5a by using the motor generator 3 more efficiently than when the motor generator 3 is continuously assisted.

In the vehicle control device 100, the drive source control unit 14 calculates the assistable torque based at least on the maximum torque of the motor generator 3, and executes assist control when the assist torque is less than the assistable torque. This allows the assist control to be executed with the assist torque that the motor generator 3 can realistically output.

In the vehicle control device 100, the lockup control unit 13 disengages the lockup clutch 5a when the output torque of the engine 2 exceeds a preset OFF torque while the lockup clutch 5a is engaged, based on the vehicle speed of the vehicle 1 and the output torque of the engine 2. The drive source control unit 14 calculates the difference between the OFF torque and the ON torque at the corresponding vehicle speeds as the assistable torque. As a result, when the lockup clutch 5a is engaged by the assist control, the lockup clutch 5a remains engaged until the output torque of the engine 2 exceeds the OFF torque, making it possible to eliminate the need for the assist of the motor generator 3 to engage the lockup clutch 5a.

[Modification]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

In the above embodiment, the drive source control unit 14 calculates the assistable torque as a fixed value based on the difference between the OFF torque and the ON torque at corresponding vehicle speeds, but it may be a variable value. The drive source control unit 14 may calculate the assistable torque as a substantially variable value based on the estimated fuel economy effect so that a preset fuel economy effect is obtained. The fuel economy impact and fuel economy effect will be described with reference to FIG. 8.

Figure 8 is a diagram showing an example of fuel efficiency based on map information. In Figure 8, the horizontal axis represents assist torque, and the vertical axis represents fuel efficiency. The assist torque increases as you move to the right from the origin, and the fuel efficiency increases as you move upward and decreases as you move downward.

As shown in FIG. 8, the driving source control unit 14 may calculate the assistable torque according to the fuel economy effect Fc due to the assist control when the vehicle 1 travels along the planned travel route on the map, based on map information and position information of the vehicle 1. The driving source control unit 14 may calculate the fuel economy effect Fc due to the assist control, based on the positive effect on fuel economy due to engagement of the lockup clutch 5a when it is assumed that the assist control is performed, and the negative effect on fuel economy due to the power consumption of the motor generator 3 when it is assumed that the assist control is performed. The driving source control unit 14 can acquire the position information of the vehicle 1, for example, based on the reception results of the GNSS receiver 25.

In Figure 8, the dashed line corresponds to the fuel economy impact Fa due to direct engagement. The fuel economy impact due to direct engagement refers to the positive impact on fuel economy due to engagement of the lock-up clutch 5a when it is assumed that assist control is executed when the vehicle 1 travels along the planned travel route on the map. In other words, the dashed line represents the improvement in fuel economy when it is assumed that assist control can be executed and the opportunity to engage the lock-up clutch 5a is maximized, taking into account the road shape, gradient, speed limit, road regulations, etc., on the planned travel route along which the vehicle 1 will travel.

In FIG. 8, the dashed-dotted line corresponds to the fuel economy impact Fb due to assist. The fuel economy impact due to assist means the negative impact on fuel economy caused by the power consumption of the motor generator 3 when it is assumed that assist control is executed when the vehicle 1 travels along the planned travel route on the map. In other words, the dashed-dotted line represents the deterioration in fuel economy caused by compensating for the power consumption of the motor generator 3 by charging the engine 2 when it is assumed that assist control can be executed and the opportunity for engagement of the lock-up clutch 5a is maximized, taking into account the road shape, gradient, speed limit, road regulations, etc., along the planned travel route along which the vehicle 1 will travel.

The fuel economy impact Fb due to the assist can be calculated, for example, by using the average fuel economy rate (BSFC [g/kWh]) of the engine 2 previously stored in the memory unit 12, and subtracting the product of "the amount of work during the course of the vehicle 1 traveling along the planned route on the map x the BSFC when it is assumed that no assist control is performed at all during that course" from the product of "the amount of work during the course of the vehicle 1 traveling along the planned route on the map x the BSFC when the assist control opportunity is maximized during that course."

In FIG. 8, the solid line corresponds to the fuel economy effect Fc due to assist control. The fuel economy effect Fc due to assist control is calculated as the sum of the fuel economy effect Fa due to direct coupling (positive fuel economy effect) and the fuel economy effect Fb due to assist (negative fuel economy effect).

As shown by the fuel economy effect Fc due to assist control, the fuel economy effect is positive in the region where the assist torque is small, and as the assist torque increases, the positive fuel economy effect becomes smaller, and eventually the fuel economy effect becomes negative. This is thought to be because as the assist torque increases, the power consumption for assist control increases, and the subsequent deterioration of fuel economy due to charging increases (the negative fuel economy effect of the fuel economy effect Fb due to assist becomes larger).

Therefore, the drive source control unit 14 may execute assist control when the fuel efficiency effect Fc due to the assist control is greater than a predetermined threshold value Fth. This is essentially equivalent to the assistable torque Tb in FIG. 9 being variable according to the threshold value Fth (according to the map information and the position information of the vehicle 1).

The processing of the ECU 10 in the example of FIG. 8 may, for example, be the processing shown in FIG. 9 as a specific example of processing S01 in FIG. 6.

Figure 9 is a flowchart showing an example of the process for determining whether to execute assist control that takes fuel economy effect into consideration. As shown in Figure 9, in S21, the ECU 10 causes the lockup control unit 13 to calculate the fuel economy effect Fa due to direct coupling. In S22, the lockup control unit 13 causes the lockup control unit 13 to calculate the fuel economy effect Fb due to assist. In S23, the lockup control unit 13 calculates the fuel economy effect Fc due to assist.

In S24, the ECU 10 determines whether the fuel economy effect Fc is greater than the threshold value Fth using the lockup control unit 13. If the lockup control unit 13 determines that the fuel economy effect Fc is greater than the threshold value Fth (S24: YES), the ECU 10 determines in S25 to execute assist control. If the lockup control unit 13 determines that the fuel economy effect Fc is equal to or less than the threshold value Fth (S24: NO), the ECU 10 determines in S26 not to execute assist control. After that, the ECU 10 ends the process in FIG. 9 and transitions to S02 in FIG. 6.

According to the vehicle control device 100 of the above-mentioned modified example, the drive source control unit 14 essentially calculates the assistable torque Tb according to the fuel efficiency effect Fc due to the assist control when the vehicle 1 travels along the planned travel route on the map, based on the map information and the position information of the vehicle 1. This makes it possible to execute the assist control so as to obtain, for example, a fuel efficiency effect Fc greater than a preset threshold value Fth.

According to the vehicle control device 100 of the above-mentioned modified example, the drive source control unit 14 calculates the fuel efficiency effect Fc due to the assist control based on the positive effect on fuel efficiency caused by the engagement of the lockup clutch 5a when it is assumed that the assist control is performed (fuel efficiency effect Fa due to direct connection) and the negative effect on fuel efficiency caused by the power consumption of the motor generator 3 when it is assumed that the assist control is performed (fuel efficiency effect Fb due to assist). This makes it possible to perform the assist control by taking into consideration in advance the charging of the power consumed by the assist with the engine 2.

The assist control shown in Figures 8 and 9 in the vehicle control device 100 according to the above-mentioned modified example may be omitted. In this case, the map database 24 and the GNSS receiver 25 may be omitted.

In the above embodiment, the drive source control unit 14 calculated an example of the assist torque Ta as the difference between the output torque Tout of the engine 2 and the ON torque Ton at the corresponding vehicle speed V1 (i.e., the operating point P2 shifted to by executing the assist control is on the dashed line Lon), but this is not limited to this. The drive source control unit 14 may calculate the assist torque Ta by adding a predetermined torque value to the difference. In other words, the operating point shifted to by executing the assist control may be lower than the dashed line Lon in FIG. 4. In short, the assist torque Ta only needs to have a torque value equal to or greater than the torque value of the required torque Treq that exceeds the ON torque Ton.

In the above embodiment, the drive source control unit 14 calculates the difference between the OFF torque and the ON torque at the corresponding vehicle speeds as the assistable torque as a fixed value, but the assistable torque as a fixed value is not limited to this. For example, the assistable torque may be smaller or larger than the difference between the OFF torque and the ON torque at the corresponding vehicle speeds. From the viewpoint of maintaining the state in which the lock-up clutch 5a is engaged as a result of the assist control even when the assist torque is eliminated, it is preferable that the assistable torque be equal to or smaller than the difference between the OFF torque and the ON torque at the corresponding vehicle speeds.

In the above embodiment, the drive source control unit 14 calculates the assistable torque based at least on the maximum torque of the motor generator 3, and executes assist control when the assist torque is less than the assistable torque, but this is not limited to the above. Calculating the assistable torque is not essential, and the decision to execute assist control using the assistable torque may be omitted.

In the above embodiment, a diesel engine is used as an example of an internal combustion engine, but other internal combustion engines, such as a gasoline engine, may also be used.

In the above embodiment, the automatic transmission 4 is configured as a stepped mechanical automatic transmission, but it may also be a continuously variable transmission (CVT).

In the above embodiment, the vehicle 1 has been described as a mild hybrid vehicle as an example, but there is no particular limitation as long as the vehicle has as its drive source an engine that outputs power to an automatic transmission via a fluid coupling having a lock-up clutch, and an electric motor that is capable of assisting the power. For example, the vehicle may be a hybrid vehicle that has a battery 6 and an electric motor that are larger than those of a mild hybrid vehicle, or a plug-in hybrid vehicle in which the battery 6 can be charged from an external power source.

1...vehicle, 2...engine, 3...motor generator (electric motor), 4...automatic transmission, 5a...lockup clutch, 13...lockup control unit, 14...drive source control unit, 100...vehicle control device, Fc...fuel economy effect, Ta...assist torque, Tb...assistable torque, Tout...output torque, Treq...requested torque, V1...vehicle speed.

Claims (3)

A control device for a vehicle including, as a drive source, an engine that outputs power to an automatic transmission via a fluid coupling having a lock-up clutch, and an electric motor that is provided so as to be able to assist the power,
an output torque acquisition unit that acquires an output torque of the engine;
a required torque acquisition unit that acquires a required torque of the drive source;
a lock-up control unit that engages the lock-up clutch when the output torque is equal to or smaller than a first torque threshold value based on the output torque;
a drive source control unit that controls the engine and the electric motor so as to output the required torque,
The drive source control unit includes:
When the lock-up clutch is not engaged, an assist control is executed to control the electric motor so as to output an assist torque equal to or greater than a torque value of the required torque that exceeds the first torque threshold value, thereby causing the lock-up control unit to engage the lock-up clutch ;
Calculating an assistable torque based at least on a maximum torque of the electric motor;
When the assist torque is less than the assistable torque, the assist control is executed.
A vehicle speed acquisition unit that acquires a vehicle speed of the vehicle,
the lock-up control unit disengages the lock-up clutch when the output torque exceeds a second torque threshold that is greater than the first torque threshold when the lock-up clutch is engaged, based on the output torque;
The drive source control unit calculates, as the assistable torque, a difference between the second torque threshold value and the first torque threshold value at the corresponding vehicle speeds . 2. The vehicle control device according to claim 1, wherein the drive source control unit calculates the assistable torque in accordance with a fuel consumption effect due to the assist control when the vehicle travels along a planned travel route on a map, based on map information and position information of the vehicle. 3. The vehicle control device according to claim 2, wherein the drive source control unit calculates the fuel efficiency effect of the assist control based on the positive effect on fuel efficiency caused by engagement of the lockup clutch when the assist control is assumed to be executed and the negative effect on fuel efficiency caused by the power consumption of the electric motor when the assist control is assumed to be executed .

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