Drive force control system for hybrid vehicles

Abstract

To provide a driving force control device for hybrid vehicles that can achieve the vehicle behavior expected by the driver. [Solution] A drive force control device for a hybrid vehicle equipped with an engine and a motor as drive force sources, which drives by outputting a system torque from the engine and motor to satisfy the drive force required for the vehicle, comprising: a first phase P1 which increases the engine torque in accordance with the increase in the target system torque; a second phase P2 which limits the engine torque to a sound pressure limiting torque T1 or less; and a third phase which increases the engine torque toward the target system torque.

Description

Technical Field

[0001] This invention relates to a driving force control device for a hybrid vehicle equipped with an engine and a motor as driving force sources.

Background Art

[0002] Patent Document 1 describes a driving force control device for a hybrid vehicle in which an engine, a motor, a torque converter, and a transmission mechanism are arranged in this order on the torque transmission path. When the vehicle is in the HEV driving mode using the power of the engine, the engine torque is controlled so as to achieve all or part of the target system shaft torque, which is the target value of the torque input to the torque converter, and the motor torque is controlled so as to compensate for the torque that is insufficient with the engine torque with respect to the target system shaft torque.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the driving force control device for a hybrid vehicle described in Patent Document 1, when the target system torque increases, such as at the start of the vehicle or the start of acceleration, the engine torque increases so as to achieve the target system torque. When the target system torque at that 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 increases in this way, the engine noise increases.

[0005] On the other hand, drivers of hybrid vehicles expect the vehicle to run using the motor's power in addition to the engine. Therefore, when the vehicle starts moving or when acceleration begins, if the engine torque increases in accordance with the increase in the target system torque, the driver may perceive the vehicle as running solely on engine power. As a result, there may be a discrepancy between the vehicle's behavior (sound) that the driver expects and the actual behavior (sound) of the vehicle, which may cause the driver to feel uncomfortable.

[0006] This invention was made in view of the above-mentioned technical problems, and aims to provide a driving force control device for a hybrid vehicle that can realize the vehicle behavior expected by the driver. [Means for solving the problem]

[0007] To achieve the above objective, this invention provides a drive force control device for a hybrid vehicle that is equipped with an engine and a motor as a drive force source and drives by outputting a system torque from the engine and the motor to satisfy the drive force required for the vehicle, the device 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 accordance with the increase in the system torque, a mid-acceleration control unit that limits the torque of the engine to a predetermined torque or less, and a late-acceleration control unit that increases the torque of the engine toward the system torque.

[0008] Furthermore, in this invention, the controller may set the lower limit torque of the engine to a torque obtained by subtracting the torque corresponding to the maximum torque of the motor from the system torque.

[0009] Furthermore, in this invention, the predetermined torque may include a torque such that the sound produced by the engine outputting torque is below the maximum sound pressure level that cannot be perceived by the occupants.

[0010] Furthermore, in this invention, the controller further includes a determination unit that determines that the driver is requesting acceleration when the target value of the system torque is equal to or greater than a predetermined determination torque, and the predetermined torque may include the determination torque.

[0011] Furthermore, in this invention, the determination torque may be set to a larger torque as the vehicle speed increases. [Effects of the Invention]

[0012] According to this invention, the vehicle is driven by outputting system torque from both the engine and the motor to satisfy the required driving force. When the system torque increases, the engine torque is increased to a predetermined torque in accordance with the system torque, and the engine torque is maintained at that predetermined torque. In other words, while the system torque is increasing, the engine torque does not increase, and the motor outputs the torque to make up the deficit. Then, the engine torque is increased toward the system torque. By temporarily stagnating the engine torque at a predetermined torque in this way, even when the vehicle is accelerating, the increase in sound pressure generated from the engine can be suppressed, and the driver can recognize that the driving force is being generated by the motor's power. In other words, the behavior that the driver expects from a hybrid vehicle can be realized. Furthermore, by increasing the engine torque to a predetermined torque in this way and outputting torque from the motor to satisfy the system torque, it is possible to suppress the increase in the torque required from the motor. Therefore, even a hybrid vehicle equipped with a motor that can output relatively small torque can realize the behavior that the driver expects from a hybrid vehicle. [Brief explanation of the drawing]

[0013] [Figure 1] This figure schematically shows an example of a hybrid vehicle according to an embodiment of this invention. [Figure 2] This is a block diagram illustrating the functional configuration of a drive force control device in an embodiment of the present invention. [Figure 3] This is a flowchart illustrating an example of control that defines the engine's torque limit. [Figure 4] This is a time chart illustrating the change in engine torque when the control example shown in Figure 3 is executed. [Figure 5] This flowchart illustrates an example of control that determines the engine's torque limit based on the torque during acceleration detection. [Figure 6] This flowchart explains the change in engine torque when the judgment torque is greater than the sound pressure limiting torque. [Modes for carrying out the invention]

[0014] This invention will be described based on the embodiments shown in the figures. The embodiments described below are merely examples of how this invention can be implemented and do not limit it.

[0015] An example of a hybrid vehicle according to an embodiment of this invention is schematically shown in Figure 1. The hybrid vehicle Ve shown in Figure 1 (hereinafter simply referred to as "vehicle") is equipped with an engine (ENG) 1 and a motor (MG) 2 as a power source. Engine 1 is configured in the same way as a conventional engine. Specifically, it is configured to generate torque by mixing a fuel such as gasoline or diesel with air in a cylinder and igniting the mixed fuel mixture.

[0016] Motor 2 can be configured similarly to motors used as power sources in conventional electric vehicles and hybrid vehicles. That is, in addition to functioning as a motor that outputs driving torque when power is supplied, it is configured to function as a generator that converts at least a portion of its power into electricity as the rotor shaft 3 is rotated along with it. Specifically, it is an AC motor such as a synchronous motor or an induction motor.

[0017] The above-mentioned rotor shaft 3 is provided to extend on both sides in the direction of the rotation center axis of a rotor (not shown). And a clutch mechanism 5 for connecting the output shaft (crankshaft) 4 of the engine 1 and the rotor shaft 3 of the motor 2 is provided. This clutch mechanism 5 includes a clutch plate 5a and a clutch disk 5b facing each other, the clutch plate 5a is connected to the output shaft 4 of the engine 1, and the clutch disk 5b is connected to the rotor shaft 3 of the motor 2. This clutch mechanism 5 is constituted by, for example, a friction type clutch mechanism that transmits torque according to the supplied hydraulic pressure or the supplied electric power. Note that the clutch mechanism 5 may be a meshing type clutch mechanism, and its configuration is not limited.

[0018] A torque converter 6 is connected to the end of the rotor shaft 3 on the output side (the side opposite to the engine 1). This torque converter 6 includes a pump impeller 6a connected to the rotor shaft 3 and a turbine runner 6b provided to face the pump impeller 6a. Note that a stator for rectifying the discharge flow from the turbine runner 6b may be provided. Also, a lock-up clutch 7 is provided to make the differential rotational speed between the pump impeller 6a and the turbine runner 6b a desired differential rotational speed or to rotate the pump impeller 6a and the turbine runner 6b integrally.

[0019] The output shaft 8 of the torque converter 6 is connected to a stepped automatic transmission mechanism (hereinafter simply referred to as a transmission mechanism) 9 that changes the gear ratio step by step. This transmission mechanism 9 can be configured in the same manner as the stepped automatic transmission mechanism provided in a conventional vehicle. That is, for example, it is configured to be able to set a plurality of shift speeds including forward first speed to forward sixth speed, and reverse speeds such as reverse first speed. Note that the transmission mechanism 9 may be a belt-type continuously variable transmission mechanism or a toroidal continuously variable transmission mechanism that continuously changes the gear ratio by changing the winding radius of the belt or changing the inclination angle of the power roller, etc., or a hybrid continuously variable transmission mechanism that connects the engine 1, a transmission motor (not shown), and the output shaft 10 via a differential mechanism and can continuously change the engine speed by changing the rotational speed of the transmission motor.

[0020] And, a pair of drive wheels 12 are connected to the output shaft 10 of the transmission mechanism 9 via a differential gear unit 11.

[0021] A controller 13 for controlling the above-described engine 1, motor 2, and transmission mechanism 9 is provided. This controller 13 is mainly composed of a microcomputer, and outputs a command signal for controlling the engine 1, motor 2, and transmission mechanism 9 based on the input signal, a map stored in advance, an arithmetic expression, etc.

[0022] In the example shown in FIG. 1, signals are input to the controller 13 from a crank angle sensor 14 for detecting the rotational speed of the output shaft 4 of the engine 1, a vehicle speed sensor 15 for detecting the vehicle speed, and an accelerator opening sensor 16 for detecting the required driving force. The vehicle speed sensor 15 only needs to be able to detect the rotational speed of a rotating member whose rotational speed changes according to the vehicle speed. In the example shown in FIG. 1, it detects the rotational speed of the output shaft 10 of the transmission mechanism 9. The accelerator opening sensor 16 detects the operation amount of an accelerator device such as an accelerator pedal (not shown).

[0023] The controller 13 stores a gear map for selecting the gear step (gear ratio) of the transmission mechanism 9. This gear map is configured similarly to the gear map provided in a controller that controls a conventional stepped automatic transmission mechanism. That is, the gear map is configured to select the gear step based on the accelerator opening detected by the accelerator opening sensor 16 and the vehicle speed detected by the vehicle speed sensor 15. Specifically, a plurality of upshift lines and a plurality of downshift lines are set in advance with accelerator opening and vehicle speed as parameters, and the system is configured to upshift to a higher gear step when the accelerator opening decreases or the vehicle speed increases across an upshift line, and downshift to a lower gear step when the accelerator opening increases or the vehicle speed decreases across a downshift line.

[0024] Furthermore, the aforementioned vehicle Ve is configured to allow setting between an EV driving mode using motor 2 as the driving force source and an HV driving mode using engine 1, or engine 1 and motor 2, as the driving force sources. In EV driving mode, motor 2 generates all of the driving power required for vehicle Ve. Specifically, the driving power required for vehicle Ve is calculated from the accelerator opening and vehicle speed, and power corresponding to that driving power is supplied to motor 2. Note that the rotational speed of motor 2 is determined by the gear stage of the transmission mechanism 9 and the vehicle speed, so the torque of motor 2 is determined by dividing the driving power by the rotational speed of motor 2.

[0025] In HV driving mode, the driving power required for vehicle Ve is generated by engine 1 alone, or by engine 1 and motor 2. In other words, HV driving mode is a driving mode in which at least engine 1 is the driving force source. Specifically, when HV driving mode is set and steady driving is performed with small changes in driving force and vehicle speed, the target system torque of the rotor shaft 3 is determined based on the driving force required for vehicle Ve and the gear stage of the transmission mechanism 9, and the engine torque is controlled to achieve that target system torque. Furthermore, if the engine torque differs from the target system torque due to various factors such as a delay in the change of engine torque or fluctuations in engine torque, the motor 2 outputs a torque corresponding to the difference between the target system torque and the engine torque.

[0026] Therefore, if the engine torque is greater than the target system torque, motor 2 functions as a generator to regenerate the excess torque; if the engine torque is less than the target system torque, motor 2 functions as an electric motor to output the insufficient torque; and if the engine torque matches the target system torque, motor 2 does not output any torque.

[0027] On the other hand, when the HV driving mode is set and the required driving force increases, the system is configured to suppress the increase in engine noise that accompanies the increase in required driving force. Specifically, the system is configured to suppress the increase in engine noise by limiting the engine torque during the process of increasing the required driving force.

[0028] Figure 2 shows a block diagram illustrating the functional configuration of the controller 13 that limits engine torque as described above. The controller 13 shown in Figure 2 includes a target system torque calculation unit 17, an acceleration determination unit 18, a lower limit guard unit 19, an initial acceleration control unit 20, a mid-acceleration control unit 21, and a late-acceleration control unit 22.

[0029] The target system torque calculation unit 17 calculates the target system torque described above. That is, it determines the target system torque based on the driving force required for the vehicle Ve and the gear ratio of the transmission mechanism 9 including the torque converter 6.

[0030] The acceleration determination unit 18 determines whether the driver operated the accelerator pedal with the intention of accelerating. Specifically, it determines whether the accelerator pedal opening detected by the accelerator pedal opening sensor 16 is greater than or equal to a predetermined opening. This predetermined opening is set to be larger as the vehicle speed increases.

[0031] The lower limit guard unit 19 sets the lower limit torque of the engine 1. Specifically, it sets the 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 motor torque with the highest priority given to satisfying the driving force required by the driver.

[0032] The acceleration initial control unit 20 sets the engine torque according to the accelerator opening. Specifically, it increases the engine torque in accordance with the increase in the target system torque so as to follow the target system torque.

[0033] The acceleration mid-stage control unit 21 sets the engine torque to a predetermined torque or less. Specifically, it limits the engine torque to a torque that results in the maximum sound pressure level among sound pressure levels that cannot be perceived by the occupants when the engine 1 is driven (hereinafter referred to as the sound pressure limiting torque), or it limits the engine torque to a torque corresponding to the accelerator opening angle used to determine that the amount of operation of the accelerator device has been increased in order to accelerate (hereinafter referred to as the determination torque). These sound pressure limiting torques and determination torques correspond to the "predetermined torque" in the embodiment of this invention.

[0034] Furthermore, the sound pressure level increases as engine torque increases, and the sound frequency increases as engine speed increases. Also, the sound pressure level decreases as engine speed increases. Therefore, by conducting experiments beforehand, the maximum sound pressure level that is imperceptible to the occupants is determined, and the engine torque at which this maximum sound pressure level occurs is set as the sound pressure limiting torque.

[0035] The acceleration late-stage control unit 22 reduces the difference between the target system torque and the engine torque. Specifically, it increases the engine torque by a predetermined amount. This predetermined amount is determined based on the amount of change in sound pressure level determined in advance through experiments, etc., so that the engine noise level does not increase sharply with the increase in engine torque and cause discomfort to the occupants. This amount may be a fixed value or a variable value that fluctuates according to the driving noise such as vehicle speed.

[0036] Figure 3 shows a flowchart illustrating an example of the control performed by the controller 13. In the example shown in Figure 3, first, it is determined whether the accelerator opening is greater than or equal to a predetermined opening determined according to the vehicle speed (step S1). This step S1 is a step to determine whether the driver operated the accelerator with the intention of accelerating.

[0037] If the accelerator opening is less than a predetermined opening and a negative result is determined in step S1, the counter after the start of the restriction (described later) is cleared (step S2), and the limiting torque of engine 1 is set to an invalid value (step S3). This limiting torque of engine 1 is set to achieve the vehicle Ve behavior expected by the driver, and the upper limit torque determined by the configuration of engine 1 is continuously set. Then, the engine torque Te is set to the target system torque (step S4), and this routine is terminated.

[0038] On the other hand, if the accelerator opening is judged positively in step S1 because it is above a predetermined opening, it is determined whether the counter after the start of the limit is above a predetermined value (step S5). This counter after the start of the limit is used to measure the elapsed time since the engine torque Te reached the limit torque, which will be described later. The predetermined value is a period determined in advance through experiments, etc., so that the driver can feel that the vehicle Ve is accelerating by the output of torque from the motor 2, so that the vehicle behaves as the driver expects. Therefore, if the accelerator opening is judged positively in step S1 because it is above a predetermined opening, it will be judged negatively in step S5.

[0039] If a negative determination is made in step S5 because the counter is below a predetermined value after the start of the restriction, the limiting torque of engine 1 is set to the sound pressure limiting torque T1 (step S6). In other words, the upper limit of the engine torque at which the sound pressure level is imperceptible to the driver is set as the limiting torque of engine 1.

[0040] Next, it is determined whether the engine torque Te is less than the sound pressure limiting torque T1 (step S7). That is, it is determined whether the engine torque Te has increased to the limiting torque. Note that the engine torque Te may be measured by a torque sensor provided on the output shaft 4, or it may be an estimated value based on the amount of fuel injected into the engine 1, the amount of intake air, etc., or it may be a command signal to the engine 1.

[0041] If step S7 is positively determined because the engine torque Te is less than the sound pressure limiting torque T1, the process proceeds to step S4. That is, the engine torque Te is set to the target system torque. Conversely, if step S7 is negatively determined because the engine torque Te is greater than or equal to the sound pressure limiting torque T1, the post-limiting counter is incremented (step S8), the engine torque Te is set to the sound pressure limiting torque T1 (step S9), and then this routine is terminated. That is, the engine torque Te is kept constant.

[0042] On the other hand, if a positive determination is made in step S5 because the counter after the start of the limit is above a predetermined value, it is determined whether the previous value of the limit torque is above the target system torque (step S10). This is because, by executing step S11 described later, the limit torque of engine 1 gradually increases, and the engine torque Te increases accordingly, so it is necessary to determine whether the engine torque Te has reached the target system torque and it is no longer necessary to limit the engine torque Te.

[0043] Therefore, if the previous value of the limiting torque is greater than or equal to the target system torque, and the result is positive in step S11, the process proceeds to step S2. That is, the counter after the start of limiting is cleared (step S2), and the limiting torque of engine 1 is set to a null value (step S3). Conversely, if the previous value of the limiting torque is less than the target system torque, and the result is negative in step S10, the limiting torque of engine 1 is increased by a predetermined amount. That is, a predetermined amount is added to the previous value of the limiting torque of engine 1 (step S11), and the engine torque Te is set to the added limiting torque (step S12). After that, this routine is 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.

[0044] Furthermore, if the limit torque of engine 1 set in step S7 or step S12 is less than the lower limit torque of engine 1 set by the lower limit guard section 19, the engine torque Te will be set to the lower limit torque set by the lower limit guard section 19. In other words, the lower limit torque (lower limit value) of engine 1 takes precedence over the limit torque (upper limit value). This is because the priority is to satisfy the required driving force rather than suppressing the increase in engine noise.

[0045] Figure 4 shows a time chart illustrating the change in engine torque Te when the control example shown in Figure 3 is executed. In the example shown in Figure 4, at time t0, the HV driving mode is selected and steady-state driving is in progress. That is, the accelerator opening is less than the predetermined opening, and is negatively judged in step S1 in the control example above. Therefore, the engine torque Te (solid line) is not limited and is almost equal to the target system torque (dotted line). Note that the target system torque at time t0 can be satisfied by the torque of motor 2 alone, and therefore, at time t0, the engine torque Te is not lowered.

[0046] As the accelerator opening increases at time t1, the target system torque begins to increase, and consequently, the engine torque Te also begins to increase. As a result, a positive judgment is made in step S1 in the control example above, and the limiting torque of engine 1 is set to the sound pressure limiting torque T1. On the other hand, in the first phase P1, where the engine torque Te is less than the sound pressure limiting torque, a negative judgment is made in step S7 in the control example above, and the engine torque Te is controlled to follow the target system torque.

[0047] When the engine torque Te reaches the sound pressure limiting torque T1, a positive judgment is made in step S7 of the control example above, causing the counter to start incrementing after the limiting begins, and the engine torque Te is set to the sound pressure limiting torque T1. In other words, while the target system torque is increasing, the engine torque Te is maintained at the sound pressure limiting torque T1. To put it another way, the engine torque Te stagnates. As a result, a difference arises between the target system torque and the engine torque Te, and the motor 2 outputs a torque corresponding to this torque difference. Note that during the first phase P1 from time t1 to time t2, the target system torque is greater than the maximum torque of the motor 2, so the engine torque Te is lowered to the torque shown by the dashed line from time ta.

[0048] In the second phase P2, from time t2 to t3, the counter is below a predetermined value after the start of the restriction, and therefore the engine torque Te continues to be limited by the sound pressure limiting torque T1. On the other hand, at time tb, the lower limit guard value exceeds the sound pressure limiting torque T1, and the engine torque Te increases slightly in accordance with the lower limit guard value. In other words, the priority is to satisfy the target system torque for the vehicle as a whole. Note that the maximum torque of motor 2 is shown as ΔT in Figure 4.

[0049] Then, at time t3, the counter after the start of the limiting process exceeds a predetermined value, resulting in a positive judgment in step S5 of the control example above. The limiting torque at that time is the sound pressure limiting torque T1, which is smaller than the target system torque, resulting in a negative judgment in step S10 of the control example above. Therefore, in the third phase P3 from time t3 to time t4, the limiting torque begins to increase by a predetermined amount from the sound pressure limiting torque T1, and the engine torque Te increases in accordance with that limiting torque. In the example shown in Figure 4, the rate of increase of the limiting torque is higher than that of the target system torque, so the difference between the target system torque and the engine torque Te gradually decreases.

[0050] As a result, at t4, when the engine torque Te reaches the target system torque, a positive judgment is made in step S10 in the control example above, so the counter after the start of the limit is cleared and the limit torque is set to an invalid value. Then, the engine torque Te is controlled to follow the target system torque.

[0051] As described above, when the driver increases the accelerator input to increase the driving force of the vehicle Ve, in the first phase P1, which is below the sound pressure limiting torque T1, the engine torque Te is made to follow the target system torque, eliminating the need to output a large torque from the motor 2 and thus reducing power consumption.

[0052] Furthermore, in the second phase, which is a predetermined period after the engine torque Te reaches the sound pressure limiting torque T1, the engine torque Te is maintained, causing the occupants to perceive that engine 1 is not operating or outputting driving torque. In contrast, motor 2 outputs the insufficient torque, causing the vehicle Ve's driving force to follow the required driving force (target system torque). As a result, the driver perceives that driving torque is output from motor 2 and that vehicle Ve is being driven, thus realizing vehicle Ve behavior that aligns with the intentions of the hybrid vehicle driver who expects driving using motor 2.

[0053] Furthermore, by increasing the engine torque Te up to the sound pressure limiting torque T1 and outputting torque from motor 2 to satisfy the target system torque, it is possible to suppress the torque required of motor 2 from becoming too large. Therefore, even a hybrid vehicle equipped with a motor with a small maximum torque can achieve the behavior expected of a hybrid vehicle.

[0054] Furthermore, the torque obtained by subtracting the maximum torque of motor 2 from the target system torque is set as the lower limit guard value for engine torque Te. When this lower limit guard value exceeds the sound pressure limiting torque T1, which is the limiting torque of engine 1, the engine torque Te is controlled according to the lower limit guard value. As a result, outputting the driving force requested by the driver can be prioritized over suppressing engine noise, and the target system torque can be satisfied for the vehicle as a whole.

[0055] On the other hand, as described above, the predetermined opening angle at which the driver determines that the accelerator has been operated with the intention of accelerating is set to a larger opening angle at higher vehicle speeds. Therefore, for example, if the amount of accelerator operation is increased to accelerate while driving steadily at a high vehicle speed, the engine torque (determined torque T2) corresponding to that accelerator opening angle may be higher than the sound pressure limiting torque T1. In such a case, if the limiting torque of engine 1 is set to the sound pressure limiting torque T1, the engine torque Te may be reduced at the time acceleration is determined, and the engine sound may change abruptly. For this reason, the drive force control device in this embodiment of the invention is configured to set the determined torque T2 to the limiting torque of engine 1 when the determined torque T2 is greater than the sound pressure limiting torque T1.

[0056] Figure 5 shows a flowchart illustrating an example of the control. Note that steps identical to those in the control example shown in Figure 3 are given the same step numbers, and their explanations are omitted. In the example shown in Figure 5, if a negative determination is made in step S5 because the counter is below a predetermined value after the start of the limit, it is determined whether the limit torque switches from an invalid value to an effective value (step S13). Specifically, it is determined whether the limit torque was set in the previous routine.

[0057] If the limiting torque is switched from an invalid value to an effective value, resulting in a positive determination in step S13, then it is determined whether the judgment torque T2 is greater than the sound pressure limiting torque T1 (step S14). If the judgment torque T2 is greater than the sound pressure limiting torque T1, resulting in a positive determination in step S14, then the judgment torque T2 is set as the limiting torque (step S15). Then, the counter after the limiting starts is incremented (step S8).

[0058] Conversely, if the judgment torque T2 is less than or equal to the sound pressure limiting torque T1, and therefore a negative judgment is made in step S14, the process proceeds to step S6.

[0059] On the other hand, if the limiting torque does not switch from an invalid value to an active value, in other words, if the limiting torque for engine 1 was already set in the previous routine, the previous value of the limiting torque is maintained (step S16), and the process proceeds to step S8.

[0060] In this control example, the limiting torque set when a negative result is determined in step S5 is either the judgment torque T2 or the sound pressure limiting torque T1; therefore, step S9, in which the engine torque Te is set as the sound pressure limiting torque T1, is not provided.

[0061] Figure 6 shows a time chart illustrating the change in engine torque Te when the judgment torque T2 is greater than the sound pressure limiting torque T1. In the example shown in Figure 6, at time t10, the HV driving mode is selected and steady-state driving is in progress. That is, the accelerator opening is less than the predetermined opening, and is negatively judged in step S1 in the control example above. Therefore, the engine torque Te (solid line) is not limited and is almost equal to the target system torque (dotted line). Note that the target system torque at time t10 can be satisfied by the torque of motor 2 alone, and therefore, at time t10, the engine torque Te is not lowered.

[0062] As the accelerator opening increases at t11, the target system torque begins to increase, and consequently, the engine torque Te also begins to increase. On the other hand, in the example shown in Figure 5, the accelerator opening at t12 is a predetermined opening for determining acceleration, so in phase P11 from t11 to t12, the judgment in step S1 remains negative, and as a result, the engine torque Te is not limited and nearly matches the target system torque.

[0063] At time t12, the accelerator opening is determined to be greater than or equal to a predetermined opening, resulting in a positive judgment in step S1 of the control example above. Furthermore, since the judgment torque T2 is higher than the sound pressure limiting torque T1, a positive judgment is also made in step S14 of the control example above. As a result, as shown in Figure 6, in phase P12 from time t12 to time t13, the engine torque Te is limited to the judgment 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 the motor 2 outputs a torque corresponding to this torque difference. Note that in the first phase P1 from time t11 to time t12, the target system torque is greater than the maximum torque of the motor 2, so the lower limit of the engine torque Te is set to the torque shown by the dashed line.

[0064] Then, at t13, the counter after the start of the limiting process exceeds a predetermined value, resulting in a positive judgment in step S5 of the control example above. The limiting torque at that time is the judgment torque T2, which is smaller than the target system torque, resulting in a negative judgment in step S10 of the control example above. Therefore, in the third phase P13 from t13 to t14, the limiting torque begins to increase by a predetermined amount from the judgment torque T2, and the engine torque Te increases in accordance with that limiting torque. In the example shown in Figure 6, the rate of increase of the limiting torque is higher than that of the target system torque, so the difference between the target system torque and the engine torque Te gradually decreases.

[0065] As a result, at t14, when the engine torque Te reaches the target system torque, a positive judgment is made in step S10 of the control example above, so the counter after the start of the limit is cleared and the limit torque is set to an invalid value. Then, the engine torque Te is controlled to follow the target system torque.

[0066] As described above, when the judgment torque T2 is higher than the sound pressure limiting torque T1, maintaining the engine torque Te at the judgment torque T2 suppresses the increase in engine torque Te after acceleration is detected. In other words, it suppresses the increase in engine noise. As a result, the driver perceives that the vehicle Ve is being driven by the output of drive torque from motor 2, thus realizing vehicle Ve behavior that aligns with the intentions of the hybrid vehicle driver who expects driving using motor 2. Furthermore, since a decrease in engine torque Te is suppressed, it is possible to suppress the driver from feeling uncomfortable due to changes in engine noise or driving force.

[0067] Furthermore, the hybrid vehicle in this embodiment of the invention is not limited to a configuration in which the torque of the engine and motor are input to a predetermined transmission mechanism. For example, it may be a hybrid vehicle in which the motor is connected to a rotating shaft to which torque is transmitted from the engine via the transmission mechanism. In this case, for example, the target value of the torque of the output shaft of the transmission mechanism may be set as the target system torque, and the engine torque may be converted to the torque transmitted to the output side of the transmission mechanism by multiplying it by the gear ratio of the transmission mechanism, and the above control examples may be executed.

[0068] Similarly, a hybrid vehicle may transmit torque from an engine and a motor to different drive wheels, for example, by transmitting torque from the engine to a pair of front wheels and from the motor to a pair of rear wheels. In such cases, the gear ratio between the engine and the pair of front wheels may be different from the gear ratio between the motor and the pair of rear wheels. Therefore, the above control examples may be executed by setting the target torque value of one of the output shafts as the target system torque and converting it to a torque equivalent to one of the output shafts by multiplying the torque of the drive source connected to the other output shaft by the gear ratio. [Explanation of Symbols]

[0069] 1 Engine 2 motors 13 Controllers 14. Crank angle sensor 15. Vehicle speed sensor 16. Accelerator position sensor 17 Target System Torque Calculation Unit 18 Acceleration judgment section 19 Lower limit guard section 20 Acceleration Initial Control Unit 21 Acceleration Mid-Term Control Unit 22 Acceleration Late-Stage Control Unit Vehicle

Claims

1. A drive force control device for a hybrid vehicle that is equipped with an engine and a motor as drive force sources and outputs a system torque from the engine and the motor to satisfy the driving force required for the vehicle, The system includes a controller that controls the torque of the engine and the motor, The aforementioned controller, An acceleration initial control unit that increases the torque of the engine in response to an increase in the system torque, An acceleration mid-term control unit that limits the torque of the engine to a predetermined torque or less, The acceleration late control unit increases the torque of the engine toward the system torque. It is equipped with A driving force control device for a hybrid vehicle, characterized by the following features.

2. A drive force control device for a hybrid vehicle according to claim 1, The aforementioned controller, The torque obtained by subtracting the torque equivalent to the maximum torque of the motor from the system torque is set as the lower limit torque of the engine. A driving force control device for a hybrid vehicle, characterized by the following features.

3. A drive force control device for a hybrid vehicle according to claim 1, The predetermined torque includes a torque at which the sound produced by the engine outputting torque is below the maximum sound pressure level that cannot be perceived by the occupants. A driving force control device for a hybrid vehicle, characterized by the following features.

4. A drive force control device for a hybrid vehicle according to claim 1, The aforementioned controller, The system further includes a determination unit that determines that the driver is requesting acceleration when the target value of the system torque becomes equal to or greater than a predetermined determination torque. The predetermined torque includes the determination torque. A driving force control device for a hybrid vehicle, characterized by the following features.

5. A drive force control device for a hybrid vehicle according to claim 4, The aforementioned determination torque is set to a larger torque as the vehicle speed increases. A driving force control device for a hybrid vehicle, characterized by the following features.

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