Driving force control device for hybrid vehicle

Abstract

The invention provides a driving force control device for a hybrid vehicle, which can realize vehicle behaviors expected by a driver. A driving force control device for a hybrid vehicle which is provided with an engine and a motor as driving force sources and which causes the hybrid vehicle to travel by outputting system torque from the engine and the motor for satisfying driving force requested from the vehicle, the driving force control device being provided with: a first stage (P1); increasing the torque of the engine in response to the increase in the target system torque; a second stage (P2) of limiting the torque of the engine to be equal to or less than the sound pressure limiting torque (T1); and a third step of increasing the torque of the engine so as to tend to the target system torque.

Description

TECHNICAL FIELD

[0001] The present application relates to a drive force control device of a hybrid vehicle that has an engine and a motor as drive force sources. BACKGROUND

[0002] A drive force control device of a hybrid vehicle in which an engine, a motor, a torque converter, and a transmission mechanism are arranged in the above order on a torque transmission path is described in Patent Literature 1. This drive force control device is configured to control an engine torque in such a manner as to achieve all or a part of a target system shaft torque that is a target value of torque to be input to the torque converter, and control a motor torque in such a manner as to compensate for a torque amount that is insufficient in the engine torque with respect to the target system shaft torque, when in an HEV (Hybrid Electric Vehicle) running mode in which running is performed using power of the engine.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2023-84040

[0006] According to the drive force control device of the hybrid vehicle described in Patent Literature 1, in a case where the target system torque increases at the time of start of the vehicle, at the time of start of acceleration, or the like, the engine torque increases in such a manner as to achieve the target system torque. In a case where the target system torque at this time can be satisfied by the engine torque, the motor torque is not output. In other words, as the target system torque increases, the engine torque increases. As the engine torque thus increases, the engine sound increases.

[0007] On the other hand, a driver of the hybrid vehicle expects to run using power of the motor in addition to the engine. Therefore, at the time of start of the vehicle, at the time of start of acceleration, or the like, when the engine torque increases in response to an increase in the target system torque, it can be recognized that running is being performed by power of the engine alone. As a result, there is a possibility that the behavior (tone color) of the vehicle expected by the driver deviates from the actual behavior (tone color) of the vehicle, and the driver feels a sense of discomfort. SUMMARY

[0008] The present application has been achieved in view of the above-described technical problems, and aims to provide a drive force control device of a hybrid vehicle that can achieve a behavior of the vehicle expected by a driver.

[0009] To achieve the above objectives, the present invention provides a drive force control device for a hybrid vehicle, the hybrid vehicle comprising an engine and a motor as drive force sources, wherein a system torque is output from the engine and the motor to satisfy the drive force requested by the vehicle to drive the hybrid vehicle. The drive force control device for the hybrid vehicle is characterized by comprising a controller for controlling the torque of the engine and the motor, the controller comprising: an initial acceleration control unit that increases the torque of the engine in response to an increase in the system torque; a mid-acceleration control unit that limits the torque of the engine to less than or equal to a predetermined torque; and a late-acceleration control unit that increases the torque of the engine in a manner that tends towards the system torque.

[0010] Furthermore, in this invention, the controller may set the torque obtained by subtracting a torque equivalent to the maximum torque of the motor from the system torque as the lower limit torque of the engine.

[0011] Furthermore, in this invention, the specified torque may include a torque whose sound level is less than or equal to the maximum sound pressure level that the occupants cannot perceive, associated with the engine output torque.

[0012] Furthermore, in this invention, the controller may also include a determination unit that determines that the driver has requested acceleration based on the target value of the system torque being greater than or equal to a predetermined determination torque, wherein the predetermined torque includes the determination torque.

[0013] Furthermore, in this invention, the faster the vehicle speed, the greater the torque to be determined.

[0014] Invention Effects

[0015] According to the present invention, driving is achieved by outputting system torque from the engine and motor to satisfy the driving force requested by the vehicle. When the system torque increases, the engine torque is increased to a predetermined torque based on the system torque and maintained at that predetermined torque. That is, during the period of system torque increase, the engine torque does not increase, and the motor outputs a insufficient amount of torque. Then, the engine torque is increased in a manner that tends towards the system torque. By temporarily stabilizing the engine torque at the predetermined torque in this way, even when the vehicle is accelerating, the increase in sound pressure generated by the engine can be suppressed, and the driver can recognize that driving force is being generated by the motor's power. In other words, the behavior expected by the driver of a hybrid vehicle can be achieved. Furthermore, by increasing the engine torque to the predetermined torque and outputting torque from the motor in a manner that satisfies the system torque, the increase in the torque requested by the motor can be suppressed. Therefore, even hybrid vehicles equipped with motors that have a relatively small output torque can achieve the behavior expected by a hybrid vehicle. Attached Figure Description

[0016] Figure 1 This is a diagram schematically illustrating an example of a hybrid vehicle in an embodiment of the present invention.

[0017] Figure 2 This is a block diagram used to explain the functional configuration of the driving force control device in the embodiments of the present invention.

[0018] Figure 3 This is a flowchart illustrating an example of controlling the engine to determine its limiting torque.

[0019] Figure 4 It is used to execute Figure 3 The time diagram illustrates the change in engine torque under the control example shown.

[0020] Figure 5 This is a flowchart illustrating an example of controlling the engine to limit torque based on the torque at the acceleration determination.

[0021] Figure 6 This is a flowchart used to explain the change in engine torque when the determined torque is greater than the sound pressure limit torque.

[0022] Explanation of reference numerals in the attached figures

[0023] 1: Engine; 2: Motor; 13: Controller; 14: Crankshaft angle sensor; 15: Vehicle speed sensor; 16: Accelerator opening sensor; 17: Target system torque calculation unit; 18: Acceleration determination unit; 19: Lower limit protection unit; 20: Initial acceleration control unit; 21: Mid-acceleration control unit; 22: Late acceleration control unit; Ve: Vehicle. Detailed Implementation

[0024] The present invention will be described based on the embodiments shown in the accompanying drawings. It should be noted that the embodiments described below are merely examples of how to embody the present invention and are not intended to limit the present invention.

[0025] An example of a hybrid vehicle according to an embodiment of the present invention is illustrated in [the present invention]. Figure 1 . Figure 1 The hybrid vehicle shown (hereinafter simply referred to as the vehicle) Ve has an engine (ENG) 1 and a motor (MG) 2 as a power source. The engine 1 is configured in the same way as a conventional engine. Specifically, the engine 1 is configured to mix fuels such as gasoline and diesel with air in the cylinder and generate torque by igniting the mixture.

[0026] The motor 2 can be configured similarly to a motor that is provided as a driving force source of an existing electric vehicle or a hybrid vehicle. That is, the motor 2 is configured to be capable of functioning as a generator that converts at least a part of power of the rotor shaft 3 into electric power by being driven by the rotor shaft 3, in addition to functioning as a motor that outputs driving torque by being supplied with electric power. Specifically, the motor 2 is an alternating-current motor such as a synchronous motor or an induction motor.

[0027] The rotor shaft 3 described above is provided to extend to both sides in the direction of the rotational center axis of the rotor, which is not shown. Further, a clutch mechanism 5 that links the output shaft (crankshaft) 4 of the engine 1 and the rotor shaft 3 of the motor 2 is provided. The clutch mechanism 5 has a clutch plate 5a and a clutch disk 5b that are opposed to each other, the clutch plate 5a being linked to the output shaft 4 of the engine 1, and the clutch disk 5b being linked to the rotor shaft 3 of the motor 2. The clutch mechanism 5 is configured by, for example, a friction-type clutch mechanism that transmits torque corresponding to the supplied hydraulic pressure or the supplied electric power. Note that the clutch mechanism 5 can also be a mesh-type clutch mechanism, and the configuration thereof is not limited.

[0028] A torque converter 6 is linked to the end portion of the output side (the side opposite to the engine 1) of the rotor shaft 3. The torque converter 6 has a pump impeller 6a linked to the rotor shaft 3 and a turbine 6b provided opposite to the pump impeller 6a. Note that a stator that rectifies the exhaust flow from the turbine 6b can also be provided. Further, a lock-up clutch 7 that makes the rotational speed difference between the pump impeller 6a and the turbine 6b a desired rotational speed difference and integrally rotates the pump impeller 6a and the turbine 6b is provided.

[0029] A stepped automatic transmission mechanism (hereinafter, simply referred to as a transmission mechanism.) 9 that changes the gear ratio in stages is linked to the output shaft 8 of the torque converter 6. The transmission mechanism 9 can be configured similarly to the stepped automatic transmission mechanism provided in an existing vehicle. That is, for example, the transmission mechanism 9 is configured to be capable of setting a plurality of gear stages including a forward first gear to a forward sixth gear and a reverse gear such as a reverse first gear. Note that the transmission mechanism 9 can also be a belt-type continuously variable transmission mechanism, a ring-type continuously variable transmission mechanism, or the like that continuously changes the gear ratio by changing the winding radius of a belt or changing the inclination angle of a power roller, or a hybrid-type continuously variable transmission mechanism that links the engine 1, a transmission motor that is not shown, and an output shaft 10 via a differential mechanism and is capable of continuously changing the engine rotational speed by changing the rotational speed of the transmission motor.

[0030] Further, a pair of drive wheels 12 is linked to the output shaft 10 of the transmission mechanism 9 via a differential gear unit 11.

[0031] A controller 13 is provided to control the aforementioned engine 1, motor 2, and transmission mechanism 9. The controller 13 is mainly composed of a microcomputer and outputs command signals to control the engine 1, motor 2, and transmission mechanism 9 based on the input signals and pre-stored mapping diagrams, formulas, etc.

[0032] exist Figure 1 In the example shown, signals are input to the controller 13 from a crankshaft angle sensor 14 for detecting the rotational speed of the output shaft 4 of engine 1, a vehicle speed sensor 15 for detecting vehicle speed, and an accelerator opening sensor 16 for detecting the requested driving force. The vehicle speed sensor 15 only needs to detect the rotational speed of a rotating component whose rotational speed changes according to the vehicle speed. Figure 1 In the example shown, the rotational speed of the output shaft 10 of the transmission mechanism 9 is detected. The accelerator opening sensor 16 detects the amount of operation of an acceleration device such as an accelerator pedal (not shown).

[0033] The controller 13 stores a shift map for selecting the shift gears (gear ratios) of the transmission mechanism 9. This shift map is configured similarly to the shift map of a controller used to control an existing stepped automatic transmission mechanism. That is, the shift map is configured to select the shift gear based on the accelerator opening detected by the accelerator opening sensor 16 and the vehicle speed detected by the vehicle speed sensor 15. Specifically, the shift map is configured to have multiple upshift lines and multiple downshift lines predetermined using the accelerator opening and vehicle speed as parameters. When the accelerator opening crosses an upshift line and decreases, or the vehicle speed crosses an upshift line and increases, the gear is shifted to a higher gear. When the accelerator opening crosses a downshift line and increases, or the vehicle speed crosses a downshift line and decreases, the gear is shifted to a lower gear.

[0034] Furthermore, the aforementioned vehicle Ve is configured to be able to set an EV (Electric Vehicle) driving mode, where the motor 2 is the driving power source, and an HV (Hybrid Vehicle) driving mode, where the engine 1 or both the engine 1 and the motor 2 are the driving power sources. In EV driving mode, the motor 2 generates all the driving power requested by the vehicle Ve. Specifically, the driving power requested by the vehicle Ve is calculated based on the accelerator opening and the vehicle speed, and the motor 2 is energized with electricity corresponding to that driving power. It should be noted that the rotational speed of the motor 2 is determined by the gear of the transmission mechanism 9 and the vehicle speed; therefore, the torque of the motor 2 is determined by dividing the driving power by the rotational speed of the motor 2.

[0035] In the HV travel mode, the requested travel power of the vehicle Ve is generated by only the engine 1, or by the engine 1 and the motor 2. That is, the HV travel mode is a travel mode in which at least the engine 1 is used as a driving force source. Specifically, in the case where the HV travel mode is set and steady travel in which the amount of change in the driving force and the vehicle speed is small is performed, the target system torque of the rotor shaft 3 based on the driving force requested of the vehicle Ve and the shift stage of the transmission mechanism 9 is calculated, and the engine torque is controlled so as to be the target system torque. Further, in the case where the engine torque differs from the target system torque due to various factors such as a delay in the change in the engine torque, and a variation in the engine torque, a torque corresponding to the difference between the target system torque and the engine torque is output from the motor 2.

[0036] Therefore, in the case where the engine torque is greater than the target system torque, the motor 2 functions as a generator, and the excess torque is regenerated, in the case where the engine torque is less than the target system torque, the motor 2 functions as a motor, and the deficient torque is output, and in the case where the engine torque coincides with the target system torque, no torque is output from the motor 2.

[0037] On the other hand, configured to suppress an increase in the engine sound with an increase in the requested driving force in a state where the HV travel mode is set. Specifically, configured to limit the engine torque during an increase in the requested driving force, thereby suppressing an increase in the engine sound.

[0038] Figure 2 A block diagram showing the functional configuration of the controller 13 for limiting the engine torque as described above is shown in FIG. 6. Figure 2 The controller 13 shown has a target system torque calculation section 17, an acceleration determination section 18, a lower limit protection section 19, an acceleration initial control section 20, an acceleration intermediate control section 21, and an acceleration final control section 22.

[0039] The target system torque calculation section 17 calculates the target system torque described above. That is, the target system torque calculation section 17 calculates the target system torque based on the driving force requested of the vehicle Ve and the transmission ratio of the transmission mechanism 9 including the torque converter 6.

[0040] The acceleration determination section 18 determines whether or not the driver intends to accelerate with an accelerator operation. Specifically, the acceleration determination section 18 determines whether or not the accelerator opening detected by the accelerator opening sensor 16 is greater than or equal to a predetermined prescribed opening. Note that the higher the vehicle speed, the greater the prescribed opening is set to be.

[0041] The lower limit protection portion 19 sets a lower limit torque of the engine 1. Specifically, the lower limit protection portion 19 sets a torque obtained by subtracting the maximum torque of the motor 2 from the target system torque as the lower limit torque of the engine 1. This is to control the engine torque and the motor torque in such a manner that the driver's requested driving force is prioritized.

[0042] The acceleration initial stage control portion 20 sets an engine torque corresponding to the accelerator opening degree. Specifically, the acceleration initial stage control portion 20 increases the engine torque in such a manner that the target system torque is followed as the target system torque increases.

[0043] The acceleration intermediate stage control portion 21 sets the engine torque to be equal to or smaller than a prescribed torque. Specifically, the acceleration intermediate stage control portion 21 limits the engine torque to be equal to or smaller than a torque at which a sound pressure level generated by driving the engine 1 becomes a maximum sound pressure level in a sound pressure level in which the occupant cannot perceive the sound pressure level (hereinafter, referred to as a sound pressure limit torque), or limits the engine torque to be equal to or smaller than an engine torque corresponding to an accelerator opening degree at which it is determined that the operation amount of the accelerator has increased in order to perform acceleration (hereinafter, referred to as a determination torque). The sound pressure limit torque and the determination torque correspond to the "prescribed torque" in the embodiment of the present application.

[0044] Note that the more the engine torque increases, the more the sound pressure level increases, and the more the engine speed increases, the more the frequency of the sound increases. In addition, the more the engine speed increases, the more the sound pressure level decreases. Therefore, the maximum sound pressure level in the sound pressure level in which the occupant cannot perceive the sound pressure level is experimentally obtained in advance, and the engine torque at which the maximum sound pressure level is obtained is determined as the sound pressure limit torque.

[0045] The acceleration late stage control portion 22 reduces the difference between the target system torque and the engine torque. Specifically, the acceleration late stage control portion 22 increases the engine torque by a predetermined prescribed amount each time. Note that the prescribed amount is determined based on a change amount of the sound pressure level of the engine sound that suddenly increases as the engine torque increases, and the prescribed amount can be a fixed value or a variable value that varies depending on the running sound such as the vehicle speed, the change amount of the sound pressure level being determined in advance through experiments and the like in which the occupant does not feel discomfort.

[0046] Figure 3 An example of the control performed by the controller 13 will be described with reference to the flowchart shown in FIG. 6. In the example shown in FIG. 6, it is first determined whether the accelerator opening degree is equal to or greater than a prescribed opening degree determined based on the vehicle speed (step S1). This step S1 is a step for determining whether the driver has performed an accelerator operation with the intention of accelerating. Figure 3

[0047] ​In the case where the accelerator opening degree is smaller than the prescribed opening degree, and the negative determination is made in step S1, the restriction start-after counter is cleared (step S2) as described later, and the restriction torque of the engine 1 is set to an invalid value (step S3). The restriction torque of the engine 1 is a restriction torque set in order to realize the behavior of the vehicle Ve expected by the driver, and is continuously set with respect to the upper limit torque determined on the configuration of the engine 1. Further, the engine torque Te is set to the target system torque (step S4), and the routine is temporarily ended.

[0048] On the other hand, in the case where the accelerator opening degree is greater than or equal to the prescribed opening degree, and the affirmative determination is made in step S1, it is determined whether the restriction start-after counter is greater than or equal to a prescribed value determined in advance (step S5). The restriction start-after counter is used to measure the elapsed time from when the engine torque Te reaches the restriction torque described later, and the prescribed value is a period determined in advance by experiments or the like in such a manner that the behavior of the vehicle becomes as expected by the driver, and more specifically, in such a manner that the driver feels that the vehicle Ve is being accelerated by the torque output from the motor 2. Therefore, in the case where the accelerator opening degree is greater than or equal to the prescribed opening degree, and the affirmative determination is first made in step S1, the negative determination is made in step S5.

[0049] In the case where the restriction start-after counter is smaller than the prescribed value, and the negative determination is made in step S5, the restriction torque of the engine 1 is set to the sound pressure restriction torque Tl (step S6). That is, the upper limit value of the engine torque that becomes the sound pressure level that the driver cannot perceive is set as the restriction torque of the engine 1.

[0050] Next, it is determined whether the engine torque Te is smaller than the sound pressure restriction torque Tl (step S7). That is, it is determined whether the engine torque Te has increased to the restriction torque. Note that, with respect to the engine torque Te, it can be measured by providing a torque sensor at the output shaft 4, it can be an estimated value based on the fuel injection amount, the intake air amount, or the like to the engine 1, or it can be a command signal to the engine 1.

[0051] In the case where the engine torque Te is smaller than the sound pressure restriction torque Tl, and the affirmative determination is made in step S7, the routine is shifted to step S4. That is, the engine torque Te is set to the target system torque. In the case where the engine torque Te is greater than or equal to the sound pressure restriction torque Tl, and the negative determination is made in step S7, the restriction start-after counter is incremented (step S8), the engine torque Te is set to the sound pressure restriction torque Tl (step S9), and then the routine is temporarily ended. That is, the engine torque Te is maintained constant.

[0052] On the other hand, if a positive judgment is made in step S5 because the count value is greater than or equal to the specified value after the limitation begins, a judgment is made on whether the previous value of the limitation torque is greater than or equal to the target system torque (step S10). This is because the limitation torque of engine 1 is configured to gradually increase by executing step S11 described later, and the engine torque Te increases accordingly, so it is not necessary to judge whether the engine torque Te has reached the target system torque.

[0053] Therefore, if a positive judgment was made in step S10 because the previous value of the limiting torque was greater than or equal to the target system torque, the process proceeds to step S2. That is, the counter after the limiting started is cleared (step S2), and the limiting torque of engine 1 is set to an invalid value (step S3). Conversely, if a negative judgment was made in step S10 because the previous value of the limiting torque was less than the target system torque, the limiting torque of engine 1 is increased by a predetermined amount each time. That is, the previous value of the limiting torque of engine 1 is added by a predetermined amount (step S11), and the engine torque Te is set to the limiting torque after the addition operation (step S12). After that, the routine is temporarily terminated. That is, the limiting torque of engine 1 is increased by a predetermined amount, and the engine torque Te is set to the increased limiting torque.

[0054] It should be noted that if the limiting torque of engine 1 set in steps S6 and S11 is less than the lower limit torque of engine 1 set by the lower limit protection unit 19, the engine torque Te is set as the lower limit torque set by the lower limit protection unit 19. That is, the lower limit torque (lower limit value) is prioritized over the limiting torque (upper limit value) of engine 1. This is to prioritize satisfying the requested driving force compared to suppressing the increase of engine noise.

[0055] Figure 4 The diagram shows the method used to execute... Figure 3 The time diagram illustrates the change in engine torque Te under the control example shown. Figure 4 In the example shown, at time t0, the HV driving mode is selected and steady-state driving is performed. That is, the accelerator opening is less than the specified opening, and a negative judgment is made in step S1 of the control example above. Therefore, the engine torque Te (solid line) is not limited and is approximately consistent with the target system torque (dashed line). It should be noted that the target system torque at time t0 can be satisfied solely by the torque of motor 2; therefore, at time t0, the engine torque Te is not subject to lower limit protection.

[0056] At time t1, as the accelerator opening increases, the target system torque begins to increase, and correspondingly, the engine torque Te also begins to increase. As a result, a positive judgment is made in step S1 of the control example above, and therefore the limiting torque of engine 1 is set to the sound pressure limiting torque T1. On the other hand, in the first stage P1 when the engine torque Te is less than the sound pressure limiting torque, a positive judgment is made in step S7 of the control example above, and therefore the engine torque Te is controlled to follow the target system torque.

[0057] When the engine torque Te reaches the sound pressure limit torque T1, a negative judgment is made in step S7 of the control example above. Therefore, the counter starts to increment after the limit begins, and the engine torque Te is set to the sound pressure limit torque T1. That is, as the target system torque increases, the engine torque Te is maintained at the sound pressure limit torque T1. In other words, the engine torque Te stagnates. Therefore, a difference is generated between the target system torque and the engine torque Te, and thus the motor 2 outputs a torque corresponding to this torque difference. It should be noted that during the first stage P1 from time point t1 to time point t2, the target system torque is greater than the maximum torque of the motor 2. Therefore, from time point ta, the engine torque Te is protected by the lower limit torque represented by the dashed line.

[0058] The second phase, P2, from time t2 to time t3, is the region where the counter is below the specified value after the limit begins; therefore, the engine torque Te is continuously limited to the sound pressure limit torque T1. On the other hand, at time tb, the lower limit protection value exceeds the sound pressure limit torque T1, so the engine torque Te increases slightly according to the lower limit protection value. That is, as a whole vehicle, the target system torque is prioritized. It should be noted that... Figure 4 In this context, the maximum torque of motor 2 is expressed as ΔT.

[0059] Then, at time t3, the counter becomes greater than or equal to the specified value after the limitation begins, so a positive judgment is made in step S5 of the control example above. At this time, the limiting torque is the sound pressure limiting torque T1, which is less than the target system torque, so a negative judgment is made in step S10 of the control example above. Therefore, in the third stage P3 from time t3 to time t4, the limiting torque begins to increase by a specified amount each time from the sound pressure limiting torque T1, and the engine torque Te increases in a manner that follows this limiting torque. It should be noted that... Figure 4 In the example shown, the rate of increase of the limiting torque is higher than the rate of increase of the target system torque, so the difference between the target system torque and the engine torque Te gradually decreases.

[0060] As a result, at the t4 point in time at which the engine torque Te reaches the target system torque, affirmative determination is made in step S10 in the above-described control example, so the counter after the start of the restriction is cleared, and the restricted torque is set to the invalid value. Also, the engine torque Te is controlled to follow the target system torque.

[0061] In the case where the driver increases the accelerator operation amount in order to increase the driving force of the vehicle Ve as described above, the engine torque Te is caused to follow the target system torque in the first stage P1 that is smaller than the sound pressure restricted torque Tl, so a large torque does not need to be output from the motor 2, and the power consumption can be reduced.

[0062] Further, in the second stage that is a prescribed period after the engine torque Te reaches the sound pressure restricted torque Tl, the engine torque Te is maintained, so the occupant feels that the engine 1 is not operating or that no driving torque is output from the engine 1. In contrast, an insufficient torque is being output from the motor 2, so the driving force of the vehicle Ve follows the requested driving force (target system torque). As a result, the driver recognizes that the driving torque is being output from the motor 2 to drive the vehicle Ve, so the behavior of the vehicle Ve that follows the intention of the driver of the hybrid vehicle who expects to use the motor 2 for running can be realized.

[0063] Also, the engine torque Te is increased to the sound pressure restricted torque Tl and the torque is output from the motor 2 in a manner that satisfies the target system torque, so the torque requested to the motor 2 can be suppressed from becoming large. Therefore, even in the hybrid vehicle that is equipped with a motor having a small maximum torque, the behavior expected of the hybrid vehicle can be realized.

[0064] Also, a torque obtained by subtracting the maximum torque of the motor 2 from the target system torque is set as a lower limit protection value of the engine torque Te, and the engine torque Te is controlled in accordance with the lower limit protection value in the case where the lower limit protection value exceeds the sound pressure restricted torque Tl that is the restricted torque of the engine 1. Therefore, the output of the driving force requested by the driver can be prioritized over the suppression of the engine sound, and as a whole of the vehicle, the target system torque can be satisfied.

[0065] On the other hand, as described above, the higher the vehicle speed, the greater the opening degree that is set with respect to the prescribed opening degree of the accelerator operation with respect to which it is determined that the driver intends to accelerate. Therefore, for example, in a state in which steady traveling is performed at a high vehicle speed, in a case in which the amount of operation of the accelerator device is increased in order to accelerate, the engine torque corresponding to this accelerator opening degree (determination torque T2) can sometimes be higher than the sound pressure limiting torque Tl described above. In such a case, if the limiting torque of the engine 1 is set to the sound pressure limiting torque Tl, the engine torque Te can drop at the time point at which the acceleration determination is made, and the engine sound can suddenly change. Therefore, the driving force control device in the embodiment of the present application is configured to set the determination torque T2 as the limiting torque of the engine 1 in a case in which the determination torque T2 is greater than the sound pressure limiting torque Tl.

[0066] Figure 5 A flowchart for explaining this control example is shown in FIG. 12. Note that, for the same steps as in the control example shown in FIG. 11, the same step numbers are annotated and the explanations thereof are omitted. In the example shown in FIG. 12, in a case in which the negative determination is made in step S5 because the counter after the start of the limitation is less than the prescribed value, it is determined whether the limiting torque is switched from the invalid value to the valid value (step S13). Specifically, it is determined whether the limiting torque was set in the last routine. Figure 3 Figure 5 In the example shown in FIG. 12, in a case in which the affirmative determination is made in step S13 because the limiting torque is switched from the invalid value to the valid value, it is determined whether the determination torque T2 is greater than the sound pressure limiting torque Tl (step S14), and in a case in which the affirmative determination is made in step S14 because the determination torque T2 is greater than the sound pressure limiting torque Tl, the determination torque T2 is set as the limiting torque (step S15). Also, the counter after the start of the limitation is incremented (step S8).

[0067] In contrast thereto, in a case in which the negative determination is made in step S14 because the determination torque T2 is less than or equal to the sound pressure limiting torque Tl, the routine is shifted to step S6.

[0068] In the example shown in FIG. 12, in a case in which the affirmative determination is made in step S13 because the limiting torque is switched from the invalid value to the valid value, it is determined whether the determination torque T2 is greater than the sound pressure limiting torque Tl (step S14), and in a case in which the affirmative determination is made in step S14 because the determination torque T2 is greater than the sound pressure limiting torque Tl, the determination torque T2 is set as the limiting torque (step S15). Also, the counter after the start of the limitation is incremented (step S8).

[0069] On the other hand, in a case in which the limiting torque is not switched from the invalid value to the valid value, in other words, in a case in which the limiting torque of the engine 1 has already been set in the last routine, the last value of the limiting torque is maintained (step S16), and the routine is shifted to step S8.

[0070] Note that, in the present control example, the limiting torque that is set when the negative determination is made in step S5 is either one of the determination torque T2 and the sound pressure limiting torque Tl, and therefore the step S9 in which the engine torque Te is set to the sound pressure limiting torque Tl is not provided.

[0071] Note that, in the present control example, the limiting torque that is set when the negative determination is made in step S5 is either one of the determination torque T2 and the sound pressure limiting torque Tl, and therefore the step S9 in which the engine torque Te is set to the sound pressure limiting torque Tl is not provided.Figure 6 The diagram shows a timeline illustrating the change in engine torque Te when the determined torque T2 is greater than the sound pressure limit torque T1. Figure 6 In the example shown, at time t10, the HV driving mode is selected and steady-state driving is performed. That is, the accelerator opening is less than the specified opening, and a negative judgment is made in step S1 of the control example above. Therefore, the engine torque Te (solid line) is not limited and is approximately consistent with the target system torque (dashed line). It should be noted that the target system torque at time t10 can be satisfied solely by the torque of motor 2; therefore, at time t10, the engine torque Te is not subject to lower limit protection.

[0072] At time t11, as the accelerator opening increases, the target system torque begins to increase, and correspondingly, the engine torque Te also begins to increase. On the other hand, at... Figure 5 In the example shown, the accelerator opening at time t12 becomes the specified opening for determining acceleration. Therefore, in stage P11 from time t11 to time t12, negative judgments are continuously made in step S1. As a result, the engine torque Te is not limited and is roughly consistent with the target system torque.

[0073] At time t12, it is determined that the accelerator opening is greater than or equal to the specified opening, therefore a positive judgment is made in step S1 of the control example above. Furthermore, it is determined that torque T2 is higher than the sound pressure limiting torque T1, therefore a positive judgment is made in step S14 of the control example above. The result is as follows: Figure 6 As shown, in stage P12, from time t12 to time t13, the engine torque Te is limited to the determination torque T2. In other words, the engine torque Te stagnates. Therefore, a difference arises between the target system torque and the engine torque Te, and thus the motor 2 outputs a torque corresponding to this torque difference. It should be noted that during the first stage P11, from time t11 to time t12, the target system torque is greater than the maximum torque of the motor 2, therefore the lower limit of the engine torque Te is set as the torque represented by the dashed line.

[0074] Then, at time t13, the counter becomes greater than or equal to the specified value after the limit begins, so a positive judgment is made in step S5 of the control example above. The limiting torque at this time is the judgment torque T2, which is less than the target system torque, so a negative judgment is made in step S10 of the control example above. Therefore, in the third stage P13 from time t13 to time t14, the limiting torque begins to increase by a specified amount each time from the judgment torque T2, and the engine torque Te increases in a manner that follows this limiting torque. It should be noted that in... Figure 6In the example shown, the increase rate of the restriction torque is higher than the increase rate of the target system torque, and thus the difference between the target system torque and the engine torque Te gradually decreases.

[0075] As a result, at the time point t14 at which the engine torque Te reaches the target system torque, affirmative determination is made in step S10 in the above-described control example, and thus the counter is cleared after the start of the restriction, and the restriction torque is set to the invalid value. Also, the engine torque Te is controlled to follow the target system torque.

[0076] In the case where the determination torque T2 is higher than the sound pressure restriction torque Tl as described above, the engine torque Te is maintained at the determination torque T2, and thus it is possible to suppress the increase of the engine torque Te after the acceleration determination is made. That is, it is possible to suppress the increase of the engine sound. As a result, the driver recognizes that the vehicle Ve is being driven by the driving torque output from the motor 2, and thus it is possible to realize the behavior of the vehicle Ve that follows the intention of the driver of the hybrid vehicle who desires to use the motor 2 for traveling. In addition, it is possible to suppress the decrease of the engine torque Te, and thus it is possible to suppress the feeling of strangeness of the driver due to the change of the engine sound and the change of the driving force.

[0077] Note that the hybrid vehicle in the embodiment of the present application is not limited to the configuration in which the torques of the engine and the motor are input to the prescribed transmission mechanism, and for example, it can be a hybrid vehicle in which the motor is coupled to a rotating shaft to which the torque from the engine is transmitted via the transmission mechanism. In this case, for example, the target value of the torque of the output shaft of the transmission mechanism can be set as the target system torque, the engine torque can be converted into the torque transmitted to the output side of the transmission mechanism by multiplying the transmission ratio of the transmission mechanism or the like, and each of the above-described control examples can be executed.

[0078] Similarly, for example, it can be a hybrid vehicle in which the torque is transmitted from the engine to a pair of front wheels and the torque is transmitted from the motor to a pair of rear wheels, or the like, in which the torque is transmitted from the engine and the motor to different drive wheels. In such a case, the transmission ratio between the engine and the pair of front wheels and the transmission ratio between the motor and the pair of rear wheels are sometimes different, and thus the target value of the torque of either output shaft can be set as the target system torque, the torque of the other output shaft can be converted into the torque equivalent to the one output shaft by multiplying the transmission ratio or the like of the driving force source coupled to the other output shaft, and each of the above-described control examples can be executed.

Claims

1. A drive force control device for a hybrid vehicle, the hybrid vehicle comprising an engine and a motor as a drive force source, wherein a system torque is output from the engine and the motor to satisfy a drive force requested by the vehicle to drive the hybrid vehicle, the drive force control device for the hybrid vehicle being characterized in that... It has a controller for controlling the torque of the engine and the motor. The controller has: The initial acceleration control unit increases the engine torque in response to an increase in the system torque. The acceleration mid-cycle control unit limits the engine torque to less than or equal to a predetermined specified torque; and The acceleration control unit increases the engine torque in a manner that tends towards the system torque.

2. The drive force control device for a hybrid vehicle according to claim 1, characterized in that, The controller sets the torque obtained by subtracting a torque equivalent to the maximum torque of the motor from the system torque as the lower limit torque of the engine.

3. The drive force control device for a hybrid vehicle according to claim 1, characterized in that, The specified torque includes torques with a sound level less than or equal to the maximum sound pressure level that cannot be perceived by the occupants, which are associated with the engine's output torque.

4. The drive force control device for a hybrid vehicle according to claim 1, characterized in that, The controller further includes a determination unit that determines, based on the target value of the system torque being greater than or equal to a predetermined determination torque, that the driver has requested acceleration. The specified torque includes the determined torque.

5. The drive force control device for a hybrid vehicle according to claim 4, characterized in that, The faster the vehicle speed, the greater the torque is set.

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