JP7800764B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

Hybrid vehicles equipped with an engine and a rotating electric machine (motor, generator, motor generator) have become increasingly popular. Hybrid vehicles have multiple driving modes. These driving modes include EV (Electric Vehicle) mode, which runs solely on the motor using battery charge power; series mode, which runs solely on the motor while the engine generates electricity for the generator; and parallel mode, which runs primarily on the engine but also uses the motor to assist when necessary.

In addition, when using two power sources, an engine and a motor, there is a demand for efficient fuel utilization through mode switching, etc. For example, Patent Document 1 discloses a configuration that efficiently uses the engine and motor to achieve both stabilization of the vehicle's acceleration performance and reduction of fuel consumption.

Japanese Patent Application Publication No. 2003-146115

When using parallel mode, which allows the engine and motor to be used simultaneously as drive sources, it is necessary to consider the balance between the driving force provided by the engine as a power source and the driving force provided as assistance by the motor in order to improve fuel consumption (fuel efficiency). Furthermore, the engine may sometimes exceed the required torque as a result of more efficient torque output, and this surplus can be used as power for generating electricity, thereby reducing wasted energy consumption. There is a demand for more fuel-efficient driving control that takes into account such factors as the timing of switching between driving based on engine driving force and power generation, and the timing of assistance using motor driving force.

On the other hand, when switching between engine output and motor output to optimize fuel economy, responsiveness to driver requests, such as acceleration, may decrease. This phenomenon can occur, for example, in areas where changes in driver requests are realized by changes in engine torque.

The present invention was devised in light of the above-mentioned issues, and aims to improve responsiveness to driver requests while performing fuel-efficient driving control during parallel mode driving. However, this objective is not limited to this. Another objective of the present invention is to achieve effects that cannot be obtained with conventional technology, which are derived from the various configurations shown in the detailed description of the invention described below.

A control device for a vehicle according to one embodiment of the present invention has the following configuration: That is, the control device for a vehicle capable of running in a parallel mode using engine drive torque from an engine and motor assist torque from a motor,
a control unit that switches the engine drive torque in stages according to the required drive torque,
the control unit switches the engine driving torque from a first torque to a second torque in response to the required driving torque exceeding a first threshold value;
the first threshold value is set between a first value corresponding to a torque at which the engine has the best fuel economy and a second value corresponding to a torque at which increasing the output of the motor results in better fuel economy than increasing the output of the engine;
The control unit assists the difference between before and after the engine driving torque switching by increasing the motor assist torque during the period required to switch the engine driving torque from the first torque to the second torque.

This invention makes it possible to perform fuel-efficient driving control while improving responsiveness to driver requests in parallel mode, in which the engine and motor can be used as driving sources.

1 is a schematic diagram showing an example of the configuration of a vehicle according to an embodiment of the present invention; FIG. 10 is a graph illustrating torque in conventional driving control in a parallel mode. FIG. 10 is a graph illustrating conventional driving control in a parallel mode. FIG. 6 is a graph illustrating torque during travel control in a parallel mode according to the first embodiment. FIG. 6 is a graph illustrating travel control in a parallel mode according to the first embodiment. FIG. 3 is a schematic diagram for explaining the flow of torque control according to the first embodiment. 4 is a flowchart of a process of driving control according to the first embodiment. 10 is a flowchart of a threshold setting process according to the first embodiment.

With reference to the drawings, a vehicle control device will be described as an embodiment. The embodiments shown below are merely examples, and are not intended to exclude various modifications or the application of technologies not explicitly stated in the following embodiments. Each configuration of this embodiment can be implemented with various modifications within the scope of their intent. Furthermore, they can be selected or combined as needed. Furthermore, in each drawing, the same components are assigned the same reference numbers to indicate correspondence.

First Embodiment
[Overall configuration]
A vehicle 100 to which the control device according to this embodiment can be applied will be described. The vehicle 100 is a hybrid vehicle equipped with an engine 101 as a drive source, a motor 107 (rotating electric machine) for driving, and a generator 102 for generating electricity. Therefore, the vehicle 100 according to this embodiment can be a vehicle such as an HEV (Hybrid Electric Vehicle) or a PHEV (Plug-in Hybrid Electric Vehicle: a plug-in hybrid capable of external charging or external power supply). In this embodiment, the vehicle 100 will be described as a front-wheel drive vehicle, but the present invention is not limited thereto, and rear-wheel drive, four-wheel drive, or the like may also be used.

The generator 102 is connected to the engine 101 and can operate independently of the operation of the motor 107. The engine 101 is connected to the drive shaft 104 via the engine clutch 103. When the engine clutch 103 is engaged, the power generated by the engine 101 is transmitted to the drive shaft 104. The motor 107 is connected to the drive shaft 104 via the motor clutch 106. When the motor clutch 106 is engaged, the power generated by the motor 107 is transmitted to the drive shaft 104. For convenience, the power transmission path via the engine clutch 103 is also referred to as the "first power transmission path," and the power transmission path via the motor clutch 106 is also referred to as the "second power transmission path."

Drive wheels 105 (front wheels) are mounted on the drive shaft 104. Driven wheels 116 (rear wheels) are mounted on the axle 115.

The vehicle 100 is also provided with an ECU (Electronic Control Unit) 108, which corresponds to the control device of this embodiment. The ECU 108 is an electronic control device configured as an LSI (Large-Scale Integration) device or embedded electronic device that integrates, for example, a microprocessor, ROM (Read Only Memory), RAM (Random Access Memory), etc. The ECU 108 acquires signals detected by various sensors provided in the vehicle 100 and controls the vehicle 100. The sensors provided in the vehicle 100 include an accelerator position sensor 109, a brake sensor 110, a speed sensor 111, an engine rotation sensor 112, and a battery remaining capacity sensor 113. The accelerator position sensor 109 detects the amount of depression (accelerator position) of the accelerator pedal (not shown). The brake sensor 110 detects the amount of depression of a brake pedal (not shown). The speed sensor 111 detects the vehicle speed of the vehicle 100. The engine rotation sensor 112 detects the rotation speed of the engine 101. The battery remaining amount sensor 113 detects the remaining amount (SOC: State Of Charge) of the battery 114. The vehicle 100 is provided with a drive battery 114, which supplies and charges electric power.

The engine 101 is an internal combustion engine (gasoline engine, diesel engine) that uses gasoline or diesel as fuel. The operating state of the engine 101 may be controlled by the ECU 108, or may be controlled by an electronic control device (not shown) separate from the ECU 108. The generator 102 and motor 107 in this embodiment are motor-generators that function as both an electric motor and a generator. The motor 107 is a drive source that exchanges power with the battery 114, and functions primarily as an electric motor to drive the vehicle 100 and as a generator during regeneration.

The generator 102 functions as an electric motor (starter) when starting the engine 101, and is driven by engine power to generate electricity when the engine 101 is running. Furthermore, the generator 102 transmits driving force to the drive shaft 104 of the vehicle 100 when in a powered state. An inverter (not shown) that converts direct current to alternating current is provided around (or inside) each of the motor 107 and the generator 102. The rotational speeds and operating states (powered operation, regenerative/powered operation) of the motor 107 and the generator 102 are controlled by controlling the inverter (not shown).

The vehicle 100 can run in multiple driving modes, such as EV mode, series mode, and parallel mode. These driving modes are selected by the ECU 108 in accordance with the vehicle state, driving state, the driving force required by the driver, etc. Furthermore, the operation of the engine 101, generator 102, and motor 107 is controlled and used separately depending on the driving mode.

EV mode is a driving mode in which the vehicle 100 is driven solely by the motor 107 using the charged power of the drive battery 114, while the engine 101 and generator 102 are stopped. EV mode is selected, for example, when the required driving force and vehicle speed are both low or when the charge level of the battery 114 is high. Series mode is a driving mode in which the engine 101 drives the generator 102 to generate electricity, and the generated electricity is used to drive the vehicle 100 by the motor 107. Series mode is selected, for example, when the required driving force is high or the charge level of the battery 114 is low. Parallel mode is a driving mode in which the vehicle 100 is driven primarily by the driving force of the engine 101, with the motor 107 assisting in driving the vehicle 100 as needed. Parallel mode is selected, for example, when the vehicle speed is high or the required driving force is high. In this embodiment, in parallel mode, a portion of the driving force of the engine 101 (excess torque) can also be used as power for generating electricity in the battery 114.

The engine 101 and motor 107 are connected in parallel to the drive wheels 105 (here, the front wheels) via a transaxle (not shown) that incorporates multiple gears and clutches. The engine 101 is also connected to the generator 102 via a transaxle (not shown), and the power of the engine 101 is also transmitted to the generator 102.

A transaxle is a power transmission device that integrates a final drive (final reduction gear) including a differential and a transmission (reduction gear), and contains multiple mechanisms that transmit power between the driving source and the driven device.

The engine clutch 103 is, for example, a wet multi-plate clutch or a dog clutch. Power upstream of the engine clutch 103 in the power transmission path (on the engine 101 and generator 102 side) is transmitted to the drive shaft 104 when the engine clutch 103 is engaged (connected), and is cut off when the engine clutch 103 is disengaged (released). The engagement and disengagement states of the engine clutch 103 are controlled by the ECU 108.

The motor clutch 106 is, for example, a wet multi-plate clutch or a dog clutch. Power upstream of the motor clutch 106 in the power transmission path (i.e., the driving force of the motor 107) is transmitted to the drive shaft 104 when the motor clutch 106 is engaged, and is cut off when the motor clutch 106 is disengaged. The engagement and disengagement states of the motor clutch 106 are controlled by the ECU 108.

For example, when the driving mode is EV mode or series mode, the engine clutch 103 is disengaged and the motor clutch 106 is engaged. Also, when the driving mode is parallel mode and motor assist (driving force from the motor 107) is not required, the engine clutch 103 is engaged and the motor clutch 106 is disengaged. Also, when the driving mode is parallel mode and motor assist is required, both the engine clutch 103 and the motor clutch 106 are engaged.

[Drive control]
First, the problems with conventional cruise control in parallel mode will be described with reference to the drawings. Fig. 2 is a graph illustrating torque transitions during conventional cruise control in parallel mode. Fig. 3 is a graph illustrating cruise control according to accelerator operation amount, corresponding to Fig. 2 .

Figure 2 shows the torque output state, with the vertical axis representing the torque value and the horizontal axis representing time. From top to bottom, Figure 2 shows the driving torque in the vehicle 100, the torque caused by the engine 101, the torque caused by the generator 102, and the torque caused by the motor 107. The sum of the torques shown in the three graphs below is the driving torque shown in graph 202.

Graph 201 shows the drive torque required for driving (hereinafter referred to as "required drive torque"). Here, this is explained as being synonymous with the torque required by the driver's accelerator operation. On the other hand, graph 202 shows the drive torque resulting from the response by vehicle 100 (hereinafter referred to as "response drive torque"). Graph 203 shows the torque caused by engine 101. Graph 204 shows the torque caused by generator 102. Graph 205 shows the torque caused by motor 107. For generator 102, the value below 0 corresponds to power generation operation.

Figure 3 is a graph illustrating conventional driving control in parallel mode. In Figure 3, the vertical axis represents driving torque, and the horizontal axis represents accelerator operation amount. As described above, parallel mode is a mode in which driving is performed primarily using driving force from the engine 101. The solid line 301 represents the required driving torque. The dashed line 302 represents the driving torque from the engine output. Note that, for simplicity of explanation, an example is shown in which the required driving torque changes at the same rate depending on the accelerator operation amount, but this change is not necessarily limited to this.

When the engine 101 is operated, it is controlled to a predetermined torque in order to operate it in the most fuel-efficient state possible. Here, the torque obtained by operating the engine 101 in the most fuel-efficient state is referred to as the "engine fuel efficiency torque" and is indicated by T1. Furthermore, in parallel mode, the torque that starts assist by the motor output in addition to the engine output torque is referred to as the "assist start torque" and is indicated by T2. Furthermore, the maximum torque that the engine 101 can output is referred to as the "engine maximum torque." In Figure 3, the relationship between each torque is T1 < T2 < T3.

Assist start torque T2 indicates the boundary at which fuel economy is improved by outputting torque from motor 107 rather than from engine 101. In other words, when assist start torque T2 is exceeded, in order to further improve fuel economy, it is assumed that outputting torque from motor 107 will be more fuel-efficient than increasing the torque output from engine 101.

In Figure 3, area 303 shows the torque generated by the engine output that is used for driving (hereinafter referred to as "engine driving torque"). Area 304 shows the torque generated by the engine output that is used for generating electricity by the generator 102 (hereinafter referred to as "engine generating torque"). Area 305 shows the assist torque generated by the motor output (hereinafter referred to as "motor assist torque").

First, when the accelerator operation amount is in the range from 0 to threshold A (shown as range a), by operating the engine 101 in a fuel-efficient state (i.e., constant engine fuel efficiency torque T1), the required drive torque becomes lower than the engine fuel efficiency torque. Therefore, the difference (engine fuel efficiency torque - required drive torque) is diverted to power generating electricity in the generator 102 (corresponding to region 304). In other words, when the accelerator operation amount is between 0 and threshold A, the torque from the engine output (i.e., engine fuel efficiency torque T1) is used to drive the vehicle 100 and charge the battery 114 through power generation by the generator 102. Threshold A is the accelerator operation amount corresponding to the position where the engine fuel efficiency torque T1 and the required drive torque match.

When the accelerator operation amount is in the range between threshold A and threshold B (shown as range b), the required drive torque exceeds the engine fuel consumption torque T1, so the torque from the engine output is increased in response to an increase in the accelerator operation amount. At this time, charging of the battery 114 (i.e., power generation by the generator 102 using the engine drive torque) is stopped. Threshold B is the accelerator operation amount corresponding to the position where the assist start torque T2 and the required drive torque match.

When the accelerator operation amount is in the range between thresholds B and C (shown as range c), the engine drive torque is controlled to be constant at assist start torque T2, and the motor assist torque increases as the accelerator operation amount increases. Therefore, the required drive torque is provided by the sum of the engine drive torque (i.e., constant at assist start torque T2) and the motor assist torque. The motor assist torque can be output by driving the motor 107 using the power stored in the battery 114 in range a. Threshold C is the accelerator operation amount corresponding to the position where the motor assist torque becomes maximum (hereinafter referred to as "motor assist maximum torque").

When the accelerator operation amount increases further and exceeds threshold C (shown as range d), the motor assist torque reaches motor assist maximum torque and cannot be increased any further. Therefore, while maintaining the motor assist torque at motor assist maximum torque, the engine drive torque is increased in accordance with the increase in accelerator operation amount. At this time, the engine drive torque can be increased until it reaches engine maximum torque. Therefore, the maximum torque that can be output corresponding to the required drive torque is (engine maximum torque) + (motor assist maximum torque).

When control as shown in Figure 3 is performed, as can be seen by comparing graphs 201 and 202 in Figure 2, a delay in the response drive torque of the vehicle 100 relative to the required drive torque can occur in ranges b and d. Ranges b and d correspond to the ranges in which the engine drive torque is changed according to the accelerator operation amount, as shown in Figure 3. One cause of this phenomenon is that the engine 101 responds slower to requests than the motor 107 and generator 102. For example, the engine 101 experiences throttle opening control and intake delays, and these structural factors can cause a delay in response to requests.

Therefore, in this embodiment, control is performed to take into account the delay in response driving torque caused by the engine and to improve responsiveness compared to conventional methods.

Figure 4 is a graph illustrating the changes in torque during driving control in parallel mode according to this embodiment. Figure 5 is a graph corresponding to Figure 4 illustrating driving control according to the amount of operation. The configurations of Figures 4 and 5 correspond to the configurations of Figures 2 and 3, respectively, which show conventional examples. Note that the explanation here uses the amount of accelerator operation (accelerator opening) by the driver as an example, but is not limited to this, and other parameters related to torque control may also be used.

Figure 4 shows the torque output state, with the vertical axis representing the torque value and the horizontal axis representing time. From top to bottom, Figure 4 shows the driving torque of the vehicle 100, the torque caused by the engine 101, the torque caused by the generator 102, and the torque caused by the motor 107. The sum of the torques shown in the three graphs below is the driving torque shown in graph 402.

Graph 401 shows the required drive torque required for driving. Meanwhile, graph 402 shows the response drive torque. Graph 403 shows the torque caused by the engine 101. Graph 404 shows the torque caused by the generator 102. Graph 405 shows the torque caused by the motor 107. For the generator 102, this corresponds to power generation operation being performed below 0.

Figure 5 is a graph illustrating driving control in parallel mode according to this embodiment. In Figure 5, the vertical axis represents driving torque, and the horizontal axis represents accelerator operation amount. Solid line 501 represents required driving torque. Furthermore, dashed line 502 represents driving torque due to engine output. Even in the configuration according to this embodiment, the relationship between engine fuel consumption torque T1, assist start torque T2, and engine maximum torque T3 is assumed to be T1 < T2 < T3. Furthermore, threshold values A and B are defined in the same way as conventional ones.

In Figure 5, area 503 shows the engine driving torque from the torque due to the engine output. Areas 504 and 507 show the engine generating torque from the torque due to the engine output. Areas 505 and 506 show the motor assist torque from the motor output.

First, when the accelerator operation amount is in the range from 0 to threshold A (shown as range a'), by operating the engine 101 in a fuel-efficient state (i.e., constant engine fuel efficiency torque T1), the required drive torque becomes lower than the engine fuel efficiency torque. Therefore, the difference ((engine fuel efficiency torque) - (required drive torque)) is diverted to power for generating electricity in the generator 102 (corresponding to region 504). In other words, when the accelerator operation amount is between 0 and threshold A, the torque from the engine output (i.e., engine fuel efficiency torque T1) is used to drive the vehicle 100 and charge the battery 114 using electricity generated by the generator 102.

When the accelerator pedal depression amount is in the range between threshold A and threshold B' (shown as range b'), the required drive torque exceeds the engine fuel consumption torque T1. However, the engine drive torque is controlled to remain constant at engine fuel consumption torque T1, and the motor assist torque increases as the accelerator pedal depression amount increases (corresponding to region 506). Therefore, the required drive torque is provided by the sum of the engine drive torque (i.e., constant at engine fuel consumption torque T1) and the motor assist torque. At this time, as shown by dashed line 408 in Figure 4, the generator 102 does not generate electricity, and motor output is generated as shown by dashed line 409. Meanwhile, since the engine 101 cannot actually increase torque rapidly as shown in Figure 5, it gradually increases torque output as shown by dashed line 406 in Figure 4. The degree of change in torque output here is referred to as the "rate of change." In range a', motor assist torque can be output by driving the motor 107 using the power stored in the battery 114. The setting of threshold value B' will be described later, but it is set to be variable within the range between threshold value A and threshold value B.

When the accelerator pedal depression amount is in the range between threshold B' and threshold B (shown as range c'), the output from the engine 101 is increased and operated so as to remain constant at assist start torque T2. At this time, the motor assist torque from the motor output is controlled to stop. As a result, the required drive torque is lower than the torque from the engine output (i.e., assist start torque T2). Therefore, the difference ((assist start torque T2) - (required drive torque)) is diverted to power for generating electricity in the generator 102 (corresponding to region 507). In other words, when the accelerator pedal depression amount is between threshold B' and threshold B, the vehicle 100 is propelled using the torque from the engine output (i.e., equivalent to assist start torque T2) and the battery 114 is charged by electricity generated by the generator 102.

When the accelerator operation amount is in the range from threshold B to threshold C' (shown as range d'), the engine drive torque is controlled to be constant at assist start torque T2, and the motor assist torque increases as the accelerator operation amount increases. Therefore, the required drive torque is provided by the sum of the engine drive torque (i.e., constant at assist start torque T2) and the motor assist torque. The motor assist torque can be output by driving the motor 107 using the power stored in the battery 114 in range a' or range c'. Threshold C' is set to an arbitrary value. For example, threshold C' is set to a value sufficiently smaller than the operation amount corresponding to (assist start torque T2) + (motor assist maximum torque) so that motor assist can respond when the required drive torque fluctuates.

As the accelerator operation amount increases further and exceeds threshold C' (shown as range e'), the motor assist torque reaches its maximum torque and cannot be increased any further. Therefore, the engine output is increased to maintain it constant at engine maximum torque T3, and the motor assist torque is controlled to match the required drive torque. Since the engine 101 cannot actually increase torque rapidly as shown in Figure 5, the torque output is gradually increased as shown by dashed line 407 in Figure 4. In response to this, the motor output is increased as shown by dashed line 410 to compensate for the shortfall in engine output. After the engine output from dashed line 407 onwards reaches the target torque output (i.e., equivalent to engine maximum torque T3), the increase due to the motor output is returned. Therefore, the maximum torque that can be output corresponding to the required drive torque is (engine maximum torque) + (motor assist maximum torque).

As described above, in this embodiment, the engine torque is controlled by switching between three states: engine fuel consumption torque T1, assist start torque T2, and engine maximum torque T3, depending on the amount of accelerator operation.

Figure 6 is a conceptual diagram illustrating the operation of the ECU 108 according to this embodiment when determining torque during parallel mode driving. As shown in Figure 1, the ECU 108 is capable of acquiring various state information during vehicle 100 driving via various sensors. In this embodiment, the ECU 108 is capable of timely acquiring vehicle speed, accelerator operation amount, engine speed, and remaining battery charge (SOC). The ECU 108 is also capable of acquiring information regarding the maximum output value of the motor 107 and the maximum battery output of the battery 114. This information may be calculated based on information obtained from the various sensors, or predetermined information may be acquired. Note that Figure 6 focuses on the torque determination during parallel mode driving, and therefore some parts of the control flow described later in Figures 7 and 8 are duplicated and/or omitted.

ECU 108 derives the required driving torque based on the vehicle speed and accelerator operation amount (step S610). The required driving torque may be derived based on a predefined table corresponding to the vehicle speed and accelerator operation amount, or may be derived using a predefined calculation formula.

ECU 108 derives engine torque based on the required drive torque, engine speed, and remaining battery charge derived in step S610 (step S620). In deriving engine torque, ECU 108 first determines thresholds B' and C' based on the engine speed and remaining battery charge (steps S621 and S622). Furthermore, ECU 108 derives engine fuel consumption torque T1, assist start torque T2, and maximum engine torque T3 based on the engine speed and remaining battery charge (steps S623 to S625). The method for deriving engine fuel consumption torque T1, assist start torque T2, and maximum engine torque T3 is not particularly limited, and may be derived by referencing a table that associates engine speed with remaining battery charge, or by using a predetermined calculation formula.

Then, the ECU 108 determines the engine torque using the determined and derived parameters and predetermined conditions (step S626). The conditions for determining the engine torque are defined as follows, based on the configurations described with reference to FIGS. 4 and 5.
Condition 1: When the required driving torque is less than the threshold value B', the first engine torque (here, the engine fuel consumption torque T1)
Condition 2: When threshold value B'≦requested driving torque<threshold value C', the second engine torque (here, assist start torque T2)
Condition 3: When threshold value C′≦requested driving torque, a third engine torque (here, maximum engine torque T3)

Furthermore, ECU 108 calculates the motor assist reserve based on the required drive torque, engine torque, and maximum motor assist value. The maximum motor assist value indicates the maximum torque that motor 107 can supply as assist torque at a given point in time. Furthermore, motor assist reserve indicates the difference between the maximum assist torque that motor 107 can supply at a given point in time and the value of assist torque already being supplied at that point in time. ECU 108 then derives the rate of change of engine torque from the motor assist reserve (step S627).

The ECU 108 applies the derived rate of change to the derived engine torque to limit the change in engine torque output (step S628). The rate of change here corresponds to the gradient of the engine torque shown by dashed lines 406 and 407 in Figure 4. Therefore, the higher the rate of change, the more rapidly the engine torque is controlled to change, and the lower the rate of change, the more slowly the engine torque is controlled to change.

The ECU 108 also derives the maximum motor assist value based on the maximum motor value and maximum battery output (step S630). The maximum motor assist value derived here is used to derive the rate of change of engine torque in step S627.

The ECU 108 derives the assist torque by the motor 107 by subtracting the engine torque derived in step S620 from the required drive torque derived in step S610 (step S640).The ECU 108 then controls the motor 107 to output the motor assist torque derived in step S640.

ECU 108 controls engine 101 to output the engine torque derived in step S610.

The ECU 108 calculates the difference between the required drive torque calculated in step S610 and the engine torque calculated in step S620 to calculate the power generation torque to be generated by the generator 102 (step S650).The ECU 108 then controls the generator 102 to generate power with the power generation torque calculated in step S650.

[Control Flow]
7 is a flowchart of the control process according to this embodiment. This process flow may be implemented by the ECU 108 reading and executing the program and various data according to this embodiment. In this process, the ECU 108 performs control in cooperation with each part of the vehicle 100 by transmitting and receiving data to and from each part. When this process is performed, it is assumed that the vehicle 100 is in a state where it can run and is running in one of the running modes described above.

In step S701, the ECU 108 determines whether the current driving mode of the vehicle 100 is parallel mode. That is, it determines whether the mode is one in which the vehicle 100 can be driven using both the engine 101 and the motor 107 as a driving source. If the mode is parallel mode (YES in step S701), the processing by the ECU 108 proceeds to step S702. On the other hand, if the mode is not parallel mode (NO in step S701), the processing flow ends. In this case, the vehicle 100 continues to drive in a mode other than parallel mode.

In step S702, the ECU 108 acquires detection values from various sensors. In this embodiment, at least the speed, accelerator operation amount, engine speed, and remaining battery charge are acquired. Furthermore, the ECU 108 acquires information regarding the maximum output value of the motor 107 and the maximum battery output of the battery 114.

In step S703, ECU 108 sets each threshold value. In this embodiment, threshold values A, B, B', and C' are set as shown in Figure 5. Predefined values are used for threshold values A, B, and C', and threshold value B' is set using the processing flow described below with reference to Figure 8.

In step S704, ECU 108 determines whether the accelerator operation amount is less than threshold value A. If the accelerator operation amount is less than threshold value A (YES in step S704), ECU 108 proceeds to step S705. On the other hand, if the accelerator operation amount is greater than or equal to threshold value A (NO in step S704), ECU 108 proceeds to step S706.

In step S705, the ECU 108 controls the engine 101 to output a first engine torque, i.e., the engine fuel consumption torque T1. At this time, since the range corresponds to range a' in Figure 5, the required drive torque is smaller than the engine fuel consumption torque T1, and therefore the generator 102 is also controlled to generate electricity. The processing of the ECU 108 then proceeds to step S713.

In step S706, ECU 108 determines whether the accelerator operation amount is less than threshold value B'. If the accelerator operation amount is less than threshold value B' (YES in step S706), ECU 108 proceeds to step S707. On the other hand, if the accelerator operation amount is greater than or equal to threshold value B' (NO in step S706), ECU 108 proceeds to step S708.

In step S707, the ECU 108 controls the engine 101 to output the first engine torque, i.e., the engine fuel consumption torque T1. At this time, since the range corresponds to range b' in Figure 5, the required drive torque is greater than the engine fuel consumption torque T1, and therefore the ECU 108 also controls the engine 101 to provide motor assistance by the motor 107. The processing of the ECU 108 then proceeds to step S713.

In step S708, the ECU 108 determines whether the accelerator operation amount is less than threshold B. If the accelerator operation amount is less than threshold B (YES in step S708), the processing by the ECU 108 proceeds to step S709. On the other hand, if the accelerator operation amount is greater than or equal to threshold B (NO in step S708), the processing by the ECU 108 proceeds to step S710.

In step S709, the ECU 108 controls the engine 101 to output a second engine torque, i.e., the assist start torque T2. At this time, since the range corresponds to range c' in Figure 5, the required drive torque is smaller than the assist start torque T2, and therefore the generator 102 is also controlled to generate electricity. The processing of the ECU 108 then proceeds to step S713.

In step S710, the ECU 108 determines whether the accelerator operation amount is less than the threshold value C'. If the accelerator operation amount is less than the threshold value C' (YES in step S710), the ECU 108 proceeds to step S711. On the other hand, if the accelerator operation amount is greater than or equal to the threshold value C' (NO in step S710), the ECU 108 proceeds to step S712.

In step S711, the ECU 108 controls the engine 101 to output a second engine torque, i.e., the assist start torque T2. At this time, since the range corresponds to range d' in Figure 5, the required drive torque is greater than the assist start torque T2, and therefore control is performed so that motor assist by the motor 107 is also performed. The processing of the ECU 108 then proceeds to step S713.

In step S712, the ECU 108 controls the engine 101 to output a third engine torque, i.e., the maximum engine torque T3. At this time, since the range corresponds to range e' in Figure 5, the required drive torque is greater than the maximum engine torque T3, and therefore control is also performed to provide motor assistance by the motor 107. The processing of the ECU 108 then proceeds to step S713.

In step S713, the ECU 108 derives the motor assist reserve. As shown in Figure 6, the maximum value at which the motor 107 can currently assist is first calculated from the maximum value of the motor 107 and the remaining battery charge. Then, the motor torque reserve that can currently assist is calculated based on the required drive torque, the maximum motor assist, and the derived engine torque. Note that the remaining charge of the battery 114 may also be used as the motor assist reserve.

In step S714, the ECU 108 determines whether the motor assist reserve is greater than a predetermined threshold value X. Here, the threshold value X is assumed to be predetermined. In this embodiment, the greater the motor assist reserve, the lower the change rate of the engine 101 is set. In other words, the greater the motor assist reserve, the longer the time it takes to reach the target engine torque, thereby increasing the load on the motor assist side (consumption of the battery 114). On the other hand, when the motor assist reserve is small, the change rate of the engine 101 is set high and the target engine torque is reached in a shorter time, thereby reducing the load on the motor assist side (consumption of the battery 114). If the motor assist reserve is greater than the threshold value X (YES in step S714), the processing by the ECU 108 proceeds to step S715. On the other hand, if the motor assist reserve is equal to or less than the threshold value X (NO in step S714), the processing by the ECU 108 proceeds to step S716.

In step S715, the ECU 108 sets the rate of change of the engine torque to decrease and executes torque control of the engine 101. In this embodiment, the rate of change of the engine torque is used when switching the engine torque at the timings shown by the dashed lines 406 and 407 in Figure 4. Then, the processing of the ECU 108 returns to step S701 and the processing is repeated.

In step S716, the ECU 108 sets the rate of change of the engine torque to increase and executes torque control of the engine 101. In this embodiment, the rate of change of the engine torque is used when switching the engine torque at the timings shown by the dashed lines 406 and 407 in Figure 4. Then, the processing of the ECU 108 returns to step S701 and the processing is repeated.

(Threshold setting process)
8 is a flowchart of a process for setting the threshold value B' according to this embodiment. This process flow is performed, for example, in step S621 in FIG. 6 or step S703 in FIG. 7. This process flow may be realized by the ECU 108 reading and executing the program and various data according to this embodiment.

In step S801, the ECU 108 obtains the remaining charge (SOC) of the battery 114 via the battery remaining charge sensor 113.

In step S802, ECU 108 determines whether the SOC obtained in step S801 is within a predetermined reference range. The reference range is assumed to be pre-defined corresponding to the maximum capacity of battery 114. Note that although the determination is made using the reference range here, the determination may also be made using a threshold value. If the SOC is within the reference range (YES in step S802), the processing by ECU 108 proceeds to step S803. On the other hand, if the SOC is outside the reference range (NO in step S802), the processing by ECU 108 proceeds to step S804.

In step S803, ECU 108 sets threshold B' as the reference value. The reference value here may be, for example, the median value between pre-defined thresholds A and B. The median value is a value that matches the engine torque surplus (corresponding to area 506 in Figure 5) and the engine torque deficiency (corresponding to area 507 in Figure 5). This achieves a balance between engine fuel efficiency and responsiveness to requests. This processing flow then ends.

In step S804, ECU 108 determines whether the SOC is higher than the reference range, i.e., whether the SOC is rising. If the SOC is rising (YES in step S804), ECU 108 proceeds to step S805. On the other hand, if the SOC is falling (NO in step S804), ECU 108 proceeds to step S806.

In step S805, ECU 108 sets threshold B' to a value closer to threshold B than the reference value, i.e., a value higher than the reference value. The set value here may be a fixed value. Alternatively, it may be determined based on the relationship between the SOC value and the range from threshold A to threshold B, for example, a ratio. By setting threshold B' to a high value, the frequency of assistance by the motor increases, and responsiveness can be improved by using a battery 114 that is sufficiently charged. This processing flow then ends.

In step S806, ECU 108 sets threshold B' to a value closer to threshold A than the reference value, i.e., a value lower than the reference value. A fixed value may be used as the set value here. Alternatively, it may be determined based on the relationship between the SOC value and the range from threshold A to threshold B, for example, a ratio. Setting threshold B' to a low value increases the frequency of power generation by generator 102, thereby encouraging charging of battery 114 with a low SOC. This processing flow then ends.

As described above, this embodiment makes it possible to perform fuel-efficient driving control while improving responsiveness to driver requests in parallel mode, in which the engine and motor can be used as driving sources.

<Other embodiments>
In the above embodiment, an example has been described in which the speed is increased by operating the accelerator, but similar control may also be applied when the speed is decreased.

In addition, in the above embodiment, a rate of change is used to suppress sudden changes in engine torque. In this case, hysteresis may be provided for increases and decreases in the accelerator operation amount, and the rate of change may be set to any desired range for each. Therefore, different values may be set for thresholds B' and C' when increasing and decreasing. By providing hysteresis, for example, when the accelerator operation amount matches or approximately matches thresholds B' and C', the engine torque request can be controlled to prevent hunting.

In the above embodiment, the accelerator operation has been described assuming operation by the driver. However, this is not limited to this, and the configuration of the present invention may also be applied when an ECU or the like performs accelerator operation in driving assistance functions or autonomous driving functions such as ADAS (Advanced Driver-Assistance Systems) or ADS (Autonomous Driving System).

In addition, the present invention can also be realized by supplying a program or application for realizing the functions of one or more of the above-mentioned embodiments to a system or device via a network or storage medium, etc., and having one or more processors in the computer of that system or device read and execute the program.

As such, the present invention is not limited to the above-described embodiments, and it is also intended that the various components of the embodiments be combined with one another, and that modifications and applications be made by those skilled in the art based on the descriptions in the specification and well-known technology, and these are included in the scope of protection sought.

As described above, the present specification discloses the following:
(1) A control device (e.g., 108) for a vehicle (e.g., 100) capable of running in a parallel mode using an engine drive torque from an engine (e.g., 101) and a motor assist torque from a motor (e.g., 107),
a control unit (e.g., 108) that switches the engine drive torque in stages according to the required drive torque to allow the vehicle to travel;
the control unit switches the engine driving torque from a first torque (e.g., T1) to a second torque (e.g., T2) in response to the required driving torque exceeding a first threshold (e.g., threshold B′);
the first threshold is set between a first value (e.g., threshold A) corresponding to a torque at which the engine has the best fuel economy and a second value (e.g., threshold B) corresponding to a torque at which increasing the output of the motor results in better fuel economy than increasing the output of the engine;
The control unit assists the difference between before and after the engine driving torque switching by increasing the motor assist torque during a period (e.g., b') required to switch the engine driving torque from the first torque to the second torque.
According to this configuration, in the parallel mode in which the engine and the motor can be used as drive sources, it is possible to perform fuel-efficient driving control while improving responsiveness to driver requests.

(2) The vehicle control device according to (1), wherein the control unit switches the first threshold value depending on a remaining charge of a battery (for example, 114) for a motor provided in the vehicle.
This configuration makes it possible to switch the timing of assistance by the motor depending on the remaining charge of the battery.

(3) The control unit
When the remaining charge of the battery is lower than a predetermined value, the first threshold is changed so as to approach the first value;
The vehicle control device according to (2), wherein, when the remaining charge of the battery is higher than the predetermined value, the first threshold value is changed to approach the second value.
With this configuration, when the remaining battery charge is low, it is possible to adjust the engine drive torque to increase the opportunities for charging, and when the remaining battery charge is high, it is possible to adjust the engine drive torque to increase the opportunities for assist by the motor torque.

(4) The control unit further
deriving a margin of motor assist torque by the motor;
The control device for a vehicle according to (1), wherein a rate of change of the torque when the engine drive torque is switched from the first torque to the second torque is switched according to a surplus of the motor assist torque.
With this configuration, it is possible to adjust the rate of torque fluctuation of the engine according to the remaining power of the motor assist.

(5) The control unit
When the motor assist torque reserve is greater than a predetermined threshold, the rate of change is decreased;
The vehicle control device according to (4), wherein, when the motor assist torque reserve is smaller than the predetermined threshold, the rate of change is increased.
With this configuration, when the motor's remaining assist capacity is large, the engine is controlled to change slowly to achieve the target torque, and when the motor's remaining assist capacity is small, the engine is controlled to change quickly to achieve the target torque. As a result, it is possible to improve responsiveness while balancing the load between engine torque switching and motor assist.

(6) The control unit switches the engine driving torque from the second torque to a third torque in response to the required driving torque exceeding a second threshold value (for example, threshold value C′).
The vehicle control device according to (1), wherein the third torque is a maximum torque (e.g., T3) that can be output by the engine.
According to this configuration, it is possible to gradually switch to the maximum engine torque in response to the required drive torque exceeding a predetermined threshold value.

(7) The vehicle control device according to (6), wherein the second threshold value is set to correspond to a torque that is smaller than the sum of the maximum torque that can be output by the motor and the second torque.
According to this configuration, it is possible to set a threshold value for gradually switching the engine torque to the engine maximum torque, taking into consideration the values of the motor assist maximum torque and the engine maximum torque.

(8) The control unit
When the engine drive torque is lower than the required drive torque, the required drive torque is provided by assisting with the motor assist torque;
2. The vehicle control device according to claim 1, wherein, when the engine drive torque is higher than the required drive torque, the drive torque is adjusted to the required drive torque by charging a battery.
With this configuration, if the engine drive torque is lower than the required drive torque as a result of the step-by-step switching of the engine drive torque, the motor is used to assist, and if the engine drive torque is higher than the required drive torque, the generator is used to charge the battery. This makes it possible to compensate for any excess or deficiency in engine drive torque, suppress unnecessary torque consumption, and provide appropriate torque.

While various embodiments have been described above, it goes without saying that the present invention is not limited to these examples. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

This invention can be used in the manufacturing industry of electric vehicles (e.g., electric vehicles, hybrid vehicles, plug-in hybrid vehicles), as well as in the manufacturing industry of control devices installed in electric vehicles.

100... Vehicle 101... Engine 102... Generator 103... Engine clutch 104... Drive shaft 105... Drive wheels (front wheels)
106...motor clutch 107...motor 108...ECU
109: Accelerator opening sensor 110: Brake sensor 111: Speed sensor 112: Engine rotation sensor 113: Battery remaining capacity sensor 114: Battery 115: Axle 116: Driven wheels (rear wheels)

Claims (8)

A control device for a vehicle capable of running in a parallel mode using engine drive torque from an engine and motor assist torque from a motor,
a control unit that switches the engine drive torque in stages according to the required drive torque,
the control unit switches the engine driving torque from a first torque to a second torque in response to the required driving torque exceeding a first threshold value;
the first threshold is set between a first value corresponding to the first torque at which the engine has the best fuel economy and a second value corresponding to the second torque;
the control unit assists a difference between the engine driving torque and the required driving torque by increasing the motor assist torque during a period required to switch the engine driving torque from the first torque to the second torque at a predetermined rate of change,
The control unit provides hysteresis to the increase and decrease in the accelerator operation amount corresponding to the required drive torque, and sets the predetermined rate of change when switching the engine drive torque within an arbitrary range for each of the increase and decrease. The vehicle control device according to claim 1 , wherein the control unit switches the first threshold value depending on a remaining charge of a battery for a motor provided in the vehicle. The control unit
When the remaining charge of the battery is lower than a predetermined value, the first threshold is changed so as to approach the first value;
The vehicle control device according to claim 2 , wherein when the remaining charge of the battery is higher than the predetermined value, the first threshold value is changed to approach the second value. The control unit further
deriving a margin of motor assist torque by the motor;
The vehicle control device according to claim 1 , wherein a rate of change of the engine drive torque when switching from the first torque to the second torque is switched in accordance with a surplus of the motor assist torque. The control unit
When the motor assist torque reserve is greater than a predetermined threshold, the rate of change is decreased;
The vehicle control device according to claim 4 , wherein when the motor assist torque reserve is smaller than the predetermined threshold, the rate of change is increased. the control unit switches the engine driving torque from the second torque to a third torque in response to the required driving torque exceeding a second threshold value;
The vehicle control device according to claim 1 , wherein the third torque is a maximum torque that can be output by the engine. The vehicle control device according to claim 6 , wherein the second threshold value is set to correspond to a torque that is smaller than the sum of the second torque and a maximum torque that can be output by the motor. The control unit
When the engine drive torque is lower than the required drive torque, the required drive torque is provided by assisting with the motor assist torque;
2. The vehicle control device according to claim 1, wherein, when the engine drive torque is higher than the required drive torque, the drive torque is adjusted to the required drive torque by charging a battery.