Control system for hybrid vehicles

Abstract

To provide a control device for a hybrid vehicle capable of reducing suppression of acceleration / deceleration responsiveness during a period when acceleration / deceleration is required.SOLUTION: An electronic control device 90 of a vehicle 10 is configured to: (a) estimate an engine torque estimated value Te_est on the basis of a target value Ttgt of a system torque and taking into account a response delay of the engine 12; (b) calculate a differential torque ΔT, which is a shortfall of the engine torque estimated value Te_est with respect to a target system torque Tsys_tgt; (c) set a target motor torque Tmg_tgt on the basis of the differential torque ΔT under a condition where an assist torque upper limit value Tamax is applied to suppress sudden acceleration; and (d) relax the assist torque upper limit value Tamax during a target period, which is a tip-in acceleration period based on a driver's intention to accelerate, compared to a non-target period, which is not such a tip-in acceleration period.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle that sets a target value of system torque based on a required drive torque required for the hybrid vehicle.

Background Art

[0002] There is known a control device for a hybrid vehicle that sets a target value of system torque, which is the total value of the output torque of an engine (hereinafter referred to as "engine torque") and the output torque of an electric motor (hereinafter referred to as "motor torque"), based on the required drive torque required for the hybrid vehicle. For example, the one described in Patent Document 1 is such a device. In the control device for a hybrid vehicle described in Patent Document 1, the engine torque is estimated in consideration of the response delay of the engine, and the differential torque, which is the amount by which the estimated engine torque is insufficient with respect to the target value of the system torque, is set as the target value of the motor torque as assist torque. The target value of the motor torque as this assist torque is constantly uniformly limited so that the degree of sudden acceleration does not exceed a predetermined allowable range even when an abnormality occurs in the sensor related to the engine and the engine torque is estimated to be lower than the actual value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the control device for a hybrid vehicle described in Patent Document 1, the target value of the motor torque as assist torque is uniformly limited even during an acceleration period based on the driver's intention to accelerate. As a result, there is a possibility that the acceleration responsiveness of the vehicle is suppressed due to insufficient assistance of the motor during a period when such acceleration is required.

[0005] The present invention was made against the above circumstances, and its objective is to provide a control device for a hybrid vehicle that can reduce the suppression of acceleration and deceleration response during periods when acceleration and deceleration are necessary. [Means for solving the problem]

[0006] The gist of the present invention is a control device for a hybrid vehicle that sets a target value for system torque, which is the sum of engine torque, which is the output torque of the engine, and electric motor torque, which is the output torque of the electric motor, based on the required driving torque required for the hybrid vehicle, wherein (a) the engine torque is estimated based on the target value of system torque and taking into account the response delay of the engine, (b) the differential torque is calculated as the excess or deficiency of the estimated engine torque relative to the target value of system torque, (c) the target value of electric motor torque is set based on the differential torque under conditions that are limited to a predetermined limit value to suppress sudden acceleration and deceleration, and (d) the predetermined limit value is relaxed during the target period, which is an acceleration and deceleration period based on the driver's intention to accelerate or decelerate, compared to the non-target period. [Effects of the Invention]

[0007] According to the control device for a hybrid vehicle of the present invention, (a) the engine torque is estimated based on a target value of the system torque and taking into account the response delay of the engine, (b) a differential torque is calculated, which is the excess or deficiency of the estimated engine torque relative to the target value of the system torque, (c) a target value of the electric motor torque is set based on the differential torque under conditions limited by a predetermined limit value to suppress sudden acceleration and deceleration, and (d) the predetermined limit value is relaxed during the target period, which is an acceleration and deceleration period based on the driver's intention to accelerate or decelerate, compared to the non-target period. Since the predetermined limit value is relaxed during the target period, which is an acceleration and deceleration period based on the driver's intention to accelerate or decelerate, compared to the non-target period, the suppression of acceleration and deceleration responsiveness is reduced during the period when acceleration and deceleration are necessary. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows a schematic configuration of a vehicle equipped with an electronic control device according to an embodiment of the present invention, as well as a functional block diagram representing the main parts of the control functions for various controls in the vehicle. [Figure 2] Figure 1 shows an example of a flowchart illustrating the control operation of the electronic control unit. [Figure 3] This is an example of a time chart when the flowchart in Figure 2 is executed. [Figure 4] This diagram illustrates the relationship between the target system torque and the sum of the actual engine torque and the target electric motor torque, with (a) showing the state when no rapid acceleration limit is set, (b) showing the normal limit period when a rapid acceleration limit is set, and (c) showing the limit relaxation period when a rapid acceleration limit is set. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0010] Figure 1 is a schematic diagram of a vehicle 10 equipped with an electronic control device 90 according to an embodiment of the present invention, as well as a functional block diagram showing the main parts of the control functions for various controls in the vehicle 10.

[0011] Vehicle 10 comprises an engine 12 and an electric motor MG, which are power sources for driving, and a power transmission device 16 provided in the power transmission path PT between the engine 12 and a pair of drive wheels 14. Vehicle 10 also comprises a hydraulic control circuit 60, an inverter 62, a battery 64, and an electronic control device 90. Vehicle 10 corresponds to the "hybrid vehicle" in the present invention.

[0012] Engine 12 is a well-known internal combustion engine, for example, an engine with a supercharger. The electric motor MG is a so-called motor generator that has the functions of both an electric motor and a generator.

[0013] The power transmission device 16 comprises, in order from the engine 12 side, a crankshaft 30, a clutch K0, an electric motor connecting shaft 32 which is the rotating shaft of the electric motor MG, a clutch WSC, an input shaft 34, an automatic transmission 22, an output shaft 36, a differential 24, and a pair of axles 38, etc., and these are well known components. The clutch K0 and the clutch WSC are engagement devices that can disconnect and reconnect power transmission, respectively.

[0014] The electric motor MG is rotationally driven by the power stored in the battery 64 and outputs power for the vehicle 10 to move. In this specification, unless otherwise specified, torque, driving force, power, and force are synonymous. The electric motor MG also generates power from the power input from the engine 12 via the clutch K0, or from the driven force input from the pair of drive wheels 14. The power generated by the electric motor MG is used to charge the battery 64 via the inverter 62.

[0015] The K0 clutch and WSC clutch each have three operating states: fully engaged (connected), slipped (partially engaged), and disengaged (disengaged). Hereafter, the "fully engaged state" will simply be referred to as the "engaged state."

[0016] The hydraulic control circuit 60 uses the hydraulic pressure of the hydraulic oil discharged from, for example, an oil pump (not shown) as the base pressure to supply the necessary hydraulic oil to each part.

[0017] Vehicle 10 can be selected to run on engine power, with both clutch K0 and clutch WSC engaged (=connected), using engine 12 as the power source for driving. The required drive torque Tdem [Nm], which is the drive torque required for the input shaft 34, is calculated based, for example, on the accelerator opening θacc [%] corresponding to the amount the driver depresses the accelerator pedal, the actual vehicle speed V [km / h], and the gear ratio γat of the automatic transmission 22.

[0018] The electronic control device 90 is configured to include, for example, a so-called microcomputer, and executes various controls of the vehicle 10. Note that the electronic control device 90 corresponds to the "control device" in the present invention.

[0019] Various signals (for example, engine rotational speed Ne [rpm], input shaft rotational speed Nin, output shaft rotational speed Nout corresponding to the vehicle speed V, motor rotational speed Nmg [rpm], accelerator opening θacc which is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation, state of charge value SOC [%] of the battery 64, etc.) based on the detection values by various sensors (for example, engine rotational speed sensor 70, input shaft rotational speed sensor 72, output shaft rotational speed sensor 74, motor rotational speed sensor 76, accelerator opening sensor 78, battery sensor 80, etc.) are respectively input to the electronic control device 90. Note that the engine rotational speed Ne is the rotational speed of the engine 12, and the motor rotational speed Nmg is the rotational speed of the motor MG. The input shaft rotational speed Nin is the rotational speed of the input shaft 34, and the output shaft rotational speed Nout is the rotational speed of the output shaft 36. The state of charge value SOC is the ratio of the actually stored charge amount to the predetermined full charge capacity.

[0020] Various command signals (for example, engine control signal Se for controlling the engine 12, hydraulic control signal Sp for performing shift control of the automatic transmission 22, connection / disconnection control of the clutch K0, connection / disconnection control of the clutch WSC, motor control signal Smg for rotationally controlling the motor MG via the inverter 62, etc.) are respectively output from the electronic control device 90 to each device (for example, engine 12, hydraulic control circuit 60, inverter 62, etc.) provided in the vehicle 10. The "connection / disconnection control" is the control of the operating state (engagement state, slip state, release state) of the clutch K0 and the clutch WSC.

[0021] The electronic control device 90 functionally includes a drive control unit 92 and an assist torque setting unit 94. The drive control unit 92 includes an engine control unit 92a, a motor control unit 92b, a transmission control unit 92c, and a clutch control unit 92d. The assist torque setting unit 94 includes a required drive torque calculation unit 94a, a target system torque calculation unit 94b, an engine torque estimation unit 94c, a rapid acceleration limit value setting unit 94d, and a target motor torque setting unit 94e.

[0022] To realize the required drive torque Tdem, the engine control unit 92a controls the engine torque Te [Nm] which is the output torque of the engine 12, the motor control unit 92b controls the motor torque Tmg [Nm] which is the output torque of the motor MG, and the transmission control unit 92c controls the gear ratio γat of the automatic transmission 22. The clutch control unit 92d controls the connection and disconnection of the clutch K0 and the clutch WSC.

[0023] The required drive torque calculation unit 94a calculates the required drive torque Tdem based on, for example, the vehicle speed V and the accelerator opening θacc. Here, for example, when the accelerator pedal (not shown) is not depressed and the accelerator opening θacc is a zero value, it is referred to as "accelerator off", and when the accelerator pedal is depressed and the accelerator opening θacc is a positive value, it is referred to as "accelerator on".

[0024] The target system torque calculation unit 94b calculates the target system torque Tsys_tgt obtained by smoothing the change in the required drive torque Tdem. The details of the smoothing process will be described later. The target system torque Tsys_tgt corresponds to the "target value of the system torque" in the present invention.

[0025] The engine torque estimation unit 94c calculates, that is, estimates, the engine torque estimation value Te_est. The engine torque estimation value Te_est is the engine torque Te estimated in consideration of the response delay of the engine 12.

[0026] The rapid acceleration limit setting unit 94d calculates the difference torque ΔT (=Tsys_tgt-Te_est) between the target system torque Tsys_tgt and the estimated engine torque Te_est, and also determines whether or not it is a chip-in acceleration period. Hereinafter, the chip-in acceleration period will be referred to as the "chip-in acceleration period". The chip-in acceleration period is the acceleration period resulting from the switch from accelerator off to accelerator on, that is, the acceleration period when the vehicle switches from a non-driving state to a driving state in accordance with the driver's acceleration request.

[0027] If the rapid acceleration limit setting unit 94d determines that it is not the tip-in acceleration period, it maintains the rapid acceleration limit value Tsys_max at the normal setting for periods other than the tip-in acceleration period. In the normal setting, the rapid acceleration limit value Tsys_max is, for example, the target system torque Tsys_tgt plus a predetermined torque value Tp. The rapid acceleration limit value Tsys_max is the upper limit of the system torque Tsys, which is predetermined experimentally or by design to prevent the degree of rapid acceleration from falling outside a predetermined allowable range. The predetermined torque value Tp is a predetermined torque value, which is predetermined experimentally or by design to set such a rapid acceleration limit value Tsys_max.

[0028] When the rapid acceleration limit setting unit 94d determines that it is the chip-in acceleration period, it relaxes the rapid acceleration limit Tsys_max to the setting for the chip-in acceleration period. In the setting for the chip-in acceleration period, the rapid acceleration limit Tsys_max is, for example, the required drive torque Tdem plus a predetermined torque value Tp. During the chip-in acceleration period, the required drive torque Tdem is higher than the target system torque Tsys_tgt, so the rapid acceleration limit Tsys_max during the chip-in acceleration period is relaxed compared to the rapid acceleration limit Tsys_max during periods other than the chip-in acceleration period.

[0029] The target motor torque setting unit 94e determines whether the differential torque ΔT (=Tsys_tgt-Te_est) is less than or equal to the assist torque upper limit Tamax (=Tsys_max-Tsys_tgt). The assist torque upper limit Tamax is the difference between the rapid acceleration limit Tsys_max and the target system torque Tsys_tgt. During periods other than the tip-in acceleration period, the assist torque upper limit Tamax is the upper limit of the motor torque Tmg that is defined as an assist torque that prevents the degree of rapid acceleration from falling outside a predetermined allowable range, even if the engine 12 outputs only the target system torque Tsys_tgt, in the event that an abnormality occurs in the sensor related to the engine 12 and the estimated engine torque Te_est is estimated to be lower than the actual engine torque Te_real. During the tip-in acceleration period, the assist torque upper limit Tamax is a more relaxed upper limit than the upper limit of the motor torque Tmg during periods other than the tip-in acceleration period. The assist torque upper limit Tamax corresponds to the "predetermined limit" in this invention.

[0030] The target motor torque setting unit 94e sets the target motor torque Tmg_tgt to the differential torque ΔT if it determines that the differential torque ΔT is less than or equal to the assist torque upper limit Tamax. The target motor torque setting unit 94e sets the target motor torque Tmg_tgt to the assist torque upper limit Tamax if it determines that the differential torque ΔT exceeds the assist torque upper limit Tamax. The target motor torque Tmg_tgt is the target value of the motor torque Tmg. In this way, the target motor torque Tmg_tgt is set based on the differential torque ΔT under conditions limited by the assist torque upper limit Tamax.

[0031] The motor control unit 92b controls the motor MG so that the motor torque Tmg becomes the target motor torque Tmg_tgt.

[0032] Figure 2 is an example of a flowchart illustrating the control operation of the electronic control device 90 shown in Figure 1. The flowchart in Figure 2 is executed repeatedly.

[0033] First, in S10, which corresponds to the function of the requested drive torque calculation unit 94a, the requested drive torque Tdem is calculated based on the vehicle speed V and the accelerator opening θacc. After the execution of S10, in S20, which corresponds to the function of the target system torque calculation unit 94b, the change in the requested drive torque Tdem is smoothed out (=slow change processing) to calculate the target system torque Tsys_tgt. The smoothing process is a process in which, when calculating the target system torque Tsys_tgt based on the requested drive torque Tdem, the change in the target system torque Tsys_tgt is made slower than the change in the requested drive torque Tdem. After the execution of S20, in S30, which corresponds to the function of the engine torque estimation unit 94c, the engine torque estimate value Te_est is calculated. After the execution of S30, in S40, which corresponds to the function of the rapid acceleration limit value setting unit 94d, the differential torque ΔT is calculated.

[0034] After the execution of S40, in S50, which corresponds to the function of the rapid acceleration limit setting unit 94d, it is determined whether or not it is a tip-in acceleration period. If the determination in S50 is YES, in S60, which corresponds to the function of the rapid acceleration limit setting unit 94d, the rapid acceleration limit value Tsys_max is set to the requested drive torque Tdem plus a predetermined torque value Tp. If the determination in S50 is NO, in S70, which corresponds to the function of the rapid acceleration limit setting unit 94d, the rapid acceleration limit value Tsys_max is set to the target system torque Tsys_tgt plus a predetermined torque value Tp. After the execution of both S60 and S70, in S80, which corresponds to the function of the target motor torque setting unit 94e, it is determined whether or not the differential torque ΔT is less than or equal to the assist torque upper limit value Tamax. If the determination in S80 is YES, in S90, which corresponds to the function of the target motor torque setting unit 94e, the target motor torque Tmg_tgt is set to the differential torque ΔT. If the determination in S80 is NO, the target motor torque Tmg_tgt is set to the assist torque upper limit value Tamax in S100, which corresponds to the function of the target motor torque setting unit 94e. After the execution of S90 and S100, output control of the engine 12 and motor MG is performed in S110, which corresponds to the functions of the engine control unit 92a and motor control unit 92b, respectively. At this time, the motor torque Tmg is controlled to become the target motor torque Tmg_tgt.

[0035] Figure 3 is an example of a time chart when the flowchart in Figure 2 is executed. In Figure 3, the horizontal axis represents time t [sec]. For the sum of the rapid acceleration limit value Tsys_max, the engine torque estimate value Te_est, and the target motor torque Tmg_tgt, this embodiment is shown with a solid line, while the comparative example is shown with a dashed line. The comparative example is an example in which no limit relaxation period is set, and only the normal limit period is observed for the entire period.

[0036] First, let's describe this embodiment (with relaxation). In this embodiment, a restriction relaxation period is set during the chip-in acceleration period.

[0037] Prior to time t1, the accelerator opening θacc is zero, so the target system torque Tsys_tgt is considered zero. At time t1, for example, the accelerator opening θacc begins to increase due to the driver pressing the accelerator pedal. The increase in accelerator opening θacc initiates the tip-in acceleration period. From time t1 to time t2 (>t1), the required drive torque Tdem increases based on the accelerator opening θacc and vehicle speed V. From time t1 to time t5 (>t2), the target system torque Tsys_tgt increases, which is the result of smoothing out the change in the required drive torque Tdem. At time t5, the target system torque Tsys_tgt matches the required drive torque Tdem. The assist torque upper limit Tamax at time t5, the end of the restriction relaxation period, and the assist torque upper limit Tamax at time t5, the start of the normal restriction period, are considered to be the same. Furthermore, the rate of change ΔTamax of the assist torque upper limit Tamax at the end of the restriction relaxation period t5 is assumed to be the same as the rate of change ΔTamax of the assist torque upper limit Tamax at the start of the normal restriction period t5. From time t5 onward, the target system torque Tsys_tgt and the requested drive torque Tdem are maintained at the same value. From time t1 onward, the engine torque Te is increased in accordance with the increase in the target system torque Tsys_tgt. At this time, a response delay occurs in the increase of the engine torque Te, and the engine torque Te increases as shown by the estimated engine torque Te_est, for example, shown by the dashed line. At time t6 (>t5), the estimated engine torque Te_est reaches the target system torque Tsys_tgt. The motor MG is controlled so that the motor torque Tmg compensates for the differential torque ΔT (the shaded area in Figure 5).

[0038] In this embodiment, during the normal limiting period from time t5 onward, the rapid acceleration limit value Tsys_max is set to the target system torque Tsys_tgt plus a predetermined torque value Tp. During the limit relaxation period from time t1 to time t5, the rapid acceleration limit value Tsys_max is set to the required drive torque Tdem plus a predetermined torque value Tp. The "limit relaxation period" is a period during which the assist torque upper limit value Tamax (=Tsys_max-Tsys_tgt) is relaxed compared to other periods (=normal limiting period) during the tip-in acceleration period. The "limit relaxation period" corresponds to the "target period" in this invention, and the "normal limiting period" corresponds to the "non-target period" in this invention. The limit relaxation period is an assist expansion period (=a period in which the allowable assist torque is expanded), while the normal limiting period is a normal assist period (=a normal period in which the allowable assist torque is not expanded). During the restriction relaxation period, the assist torque upper limit Tamax is increased compared to the normal restriction period by, for example, the difference between the required drive torque Tdem and the target system torque Tsys_tgt. In this embodiment, this increase in the assist torque upper limit Tamax ensures that the differential torque ΔT does not exceed the assist torque upper limit Tamax during the restriction relaxation period. As a result, the target motor torque Tmg_tgt is set to compensate for the entire differential torque ΔT throughout the entire restriction relaxation period.

[0039] Figure 4 illustrates the relationship between the target system torque Tsys_tgt and the sum of the actual engine torque Te_real and the target electric motor torque Tmg_tgt, where (a) shows the state when no rapid acceleration limit is set, (b) shows the normal limit period when a rapid acceleration limit is set, and (c) shows the limit relaxation period when a rapid acceleration limit is set.

[0040] As shown in Figure 4(a), if no rapid acceleration limit is set, the assist torque upper limit Tamax is set to the upper limit Tamax1. In this case, the difference torque ΔT (=Tsys_tgt-Te_est) between the target system torque Tsys_tgt and the estimated engine torque Te_est is set to the target motor torque Tmg_tgt. In this case, if a sensor malfunction occurs in the engine 12 and the estimated engine torque Te_est is lower than the actual engine torque Te_real (for example, if the actual engine torque Te_real is the same as the target system torque Tsys_tgt), the system torque Tsys (=Te_real+Tmg_tgt) may exceed the rapid acceleration limit Tsys_max (=Tsys_max+Tamax1 in Figure 4(b)).

[0041] As shown in Figure 4(b), when a rapid acceleration limit is set (during the normal limit period), the assist torque upper limit Tamax is set to the upper limit Tamax1. In this case, the target motor torque Tmg_tgt is set by applying a limit to the difference torque ΔT between the target system torque Tsys_tgt and the estimated engine torque Te_est. Even if a sensor malfunction occurs related to the engine 12 and the estimated engine torque Te_est is lower than the actual engine torque Te_real (for example, if the actual engine torque Te_real is the same as the target system torque Tsys_tgt), the system torque Tsys (=Te_real + Tmg_tgt) will not exceed the rapid acceleration limit Tsys_max. In other words, the target motor torque Tmg_tgt is set so that even if a sensor malfunction occurs related to the engine 12 and the estimated engine torque Te_est is lower than the actual engine torque Te_real, the system torque Tsys (=Te_real + Tmg_tgt) will not exceed the rapid acceleration limit Tsys_max.

[0042] As shown in Figure 4(c), when a rapid acceleration limit is set (during the limit relaxation period), the assist torque upper limit Tamax is set to upper limit Tamax2 (> Tamax1). Upper limit Tamax2 is a larger value than upper limit Tamax1. In other words, compared to the normal limit period, the upper limit of the target motor torque Tmg_tgt set during the limit relaxation period is relaxed. In this case, the target motor torque Tmg_tgt is set by applying a limit to the difference torque ΔT between the target system torque Tsys_tgt and the engine torque estimate Te_est. The target motor torque Tmg_tgt set during the limit relaxation period may be set higher than the target motor torque Tmg_tgt set during the normal limit period. This is because the assist torque upper limit Tamax set during the limit relaxation period is higher compared to the normal limit period, which increases the rapid acceleration limit Tsys_max during the limit relaxation period. As a result, even if a sensor malfunction occurs in the engine 12 and the estimated engine torque Te_est is lower than the actual engine torque Te_real, the system torque Tsys (=Te_real + Tmg_tgt) will not exceed the rapid acceleration limit Tsys_max, even if the target electric motor torque Tmg_tgt is set higher than the upper limit Tamax1, which is the assist torque upper limit Tamax set during the normal limit period.

[0043] Returning to Figure 3, we will now discuss the comparative example (without relaxation).

[0044] During the period from time point t1 to time point t5, the rapid acceleration limit value Tsys_max is set to be the target system torque Tsys_tgt plus the assist torque upper limit value Tamax. During the period from time point t1 to time point t5, for example, the assist torque upper limit value Tamax is the same as that during the normal limit period. Since the assist torque upper limit value Tamax is the same, during the period from time point t3 (t2 < t3 < t4) to time point t4 (t3 < t4 < t5), the differential torque ΔT (= Tsys_tgt - Te_est) exceeds the assist torque upper limit value Tamax. As a result, during the period from time point t3 to time point t4, the target motor torque Tmg_tgt is limited to the assist torque upper limit value Tamax, that is, the motor torque Tmg is controlled to compensate for a part of the differential torque ΔT.

[0045] According to this embodiment, (a) an engine torque estimated value Te_est is calculated based on the target system torque Tsys_tgt and taking into account the response delay of the engine 12, (b) a differential torque ΔT, which is the amount by which the engine torque estimated value Te_est is insufficient with respect to the target system torque Tsys_tgt, is calculated, (c) the target motor torque Tmg_tgt is set based on the differential torque ΔT under the condition of being limited by the assist torque upper limit value Tamax for suppressing rapid acceleration, and (d) the assist torque upper limit value Tamax is relaxed during a period based on the driver's acceleration intention, that is, during the tip-in acceleration period based on the accelerator opening θacc, as compared with a period where it is not so. During the tip-in acceleration period based on the driver's acceleration intention, since the assist torque upper limit value Tamax is relaxed as compared with a period where it is not so, the suppression of acceleration responsiveness is reduced during a period where acceleration is required.

[0046] In this embodiment, when switching from a restriction relaxation period to a normal restriction period, the assist torque upper limit Tamax and the rate of change ΔTamax at the end of the restriction relaxation period t5 are the same as the assist torque upper limit Tamax and the rate of change ΔTamax at the start of the normal restriction period t5. In this way, if neither the assist torque upper limit Tamax nor the rate of change ΔTamax changes at the boundary between the restriction relaxation period and the normal restriction period, the assist torque upper limit Tamax changes gradually, i.e., smoothly, at the boundary. Therefore, the motor torque Tmg as the assist torque does not change abruptly due to the change in the assist torque upper limit Tamax, and the degree of rapid acceleration does not fall outside the predetermined allowable range.

[0047] In this embodiment, (a) the target system torque Tsys_tgt is set by annealing the requested drive torque Tdem, (b) the assist torque upper limit Tamax during the tip-in acceleration period is determined based on the requested drive torque Tdem, and (c) the assist torque upper limit Tamax during the normal limit period is determined based on the target system torque Tsys_tgt. Due to (a), the requested drive torque Tdem is higher than the target system torque Tsys_tgt during the tip-in acceleration period. Due to this and the configurations in (b) and (c) above, the assist torque upper limit Tamax is relaxed during the tip-in acceleration period compared to other periods.

[0048] In this embodiment, the driver's intention to accelerate is determined by the switch from releasing the accelerator to pressing it. This method allows for a simple determination of the driver's intention to accelerate.

[0049] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit.

[0050] In the above-described embodiment, the engine 12 was a turbocharged engine, but the present invention is not limited to this embodiment. For example, even an engine without a turbocharger will have a response delay, so the present invention is also applicable to vehicle configurations equipped with an engine without a turbocharger.

[0051] In the above-described embodiment, the assist torque upper limit Tamax and the rate of change ΔTamax at the end of the restriction relaxation period t5 were the same as the assist torque upper limit Tamax and the rate of change ΔTamax at the start of the normal restriction period t5. However, the present invention is not limited to this embodiment. For example, the present invention is also applicable to embodiments in which either the assist torque upper limit Tamax or the rate of change ΔTamax changes abruptly at time t5. Even in such embodiments, the assist torque upper limit Tamax is relaxed during the tip-in acceleration period compared to other periods, thus reducing the suppression of acceleration responsiveness during periods in which acceleration is required.

[0052] In the embodiments described above, (a) the assist torque upper limit Tamax during the tip-in acceleration period was determined based on the required drive torque Tdem, and (b) the assist torque upper limit Tamax during the normal limit period was determined based on the target system torque Tsys_tgt. However, the present invention is not limited to these embodiments. The present invention allows the assist torque upper limit Tamax to be determined in any way during the tip-in acceleration period, as long as the assist torque upper limit Tamax is relaxed compared to other periods.

[0053] In the above-described embodiment, the driver's intention to accelerate was determined by the switch from accelerator off to accelerator on, but the present invention is not limited to this embodiment. For example, the driver's intention to accelerate may be determined by the change in throttle valve opening.

[0054] In the above-described embodiment, the upper limit of the assist torque Tamax was relaxed during the tip-in acceleration period based on the driver's intention to accelerate, compared to periods without such intention. However, the present invention is not limited to this embodiment. For example, the present invention can also be applied to an embodiment in which the lower limit of the assist torque is relaxed during the deceleration period based on the driver's intention to decelerate, compared to periods without such intention. In this embodiment, the lower limit of the assist torque is the lower limit (<0) of the motor torque Tmg, which is defined as an assist torque such that the degree of rapid deceleration does not fall outside a predetermined allowable range, even if the engine 12 outputs only the target system torque Tsys_tgt when an abnormality occurs in the sensor related to the engine 12 and the estimated engine torque Te_est is estimated to be higher than the actual engine torque Te_real. The driver's intention to decelerate is determined, for example, by switching from accelerator on to accelerator off. In this embodiment, a differential torque ΔT (=Tsys_tgt-Te_est<0), which is the excess amount in the estimated engine torque Te_est relative to the target system torque Tsys_tgt, is calculated, and the target motor torque Tmg_tgt is set based on the differential torque ΔT (negative torque) under conditions limited by the assist torque lower limit. The assist torque lower limit corresponds to the "predetermined limit value" in this invention. Thus, the driver's intention to accelerate or decelerate is determined by switching from either accelerator off or accelerator on to the other, and the differential torque ΔT, which is the excess or deficiency in the estimated engine torque Te_est relative to the target system torque Tsys_tgt, is calculated. The predetermined limit value, the assist torque upper limit Tamax or the assist torque lower limit, is relaxed during the target period, which is an acceleration / deceleration period based on the driver's intention to accelerate or decelerate, compared to the non-target period. During periods based on the driver's intention to accelerate or decelerate, the upper limit of the assist torque (Tamax) or the lower limit of the assist torque are relaxed compared to non-target periods. As a result, the suppression of acceleration and deceleration responsiveness is reduced during periods when acceleration or deceleration is necessary. [Explanation of symbols]

[0055] 10: Vehicle (hybrid vehicle), 12: Engine, 90: Electronic control unit (control unit), MG: Electric motor, Tamax: Assist torque upper limit (predetermined limit value), Tdem: Required drive torque, Te: Engine torque (engine output torque), Tmg: Electric motor torque (electric motor output torque), Tmg_tgt: Target electric motor torque (target value of electric motor torque), Tsys: System torque, Tsys_tgt: Target system torque (target value of system torque), ΔT: Differential torque, ΔTamax: Rate of change over time

Claims

1. A control device for a hybrid vehicle that sets a target value for the system torque, which is the sum of the engine torque (the output torque of the engine) and the electric motor torque (the output torque of the electric motor), based on the required driving torque for the hybrid vehicle. Based on the target value of the system torque and taking into account the response delay of the engine, the engine torque is estimated. The differential torque, which is the difference between the estimated engine torque and the target value of the system torque, is calculated. Under conditions where the torque is limited to a predetermined limit value to suppress sudden acceleration and deceleration, the target value of the motor torque is set based on the differential torque. The aforementioned predetermined limit values ​​are relaxed during the target period, which is a period of acceleration or deceleration based on the driver's intention to accelerate or decelerate, compared to the non-target period. A control device for a hybrid vehicle characterized by the following features.

2. When switching from the aforementioned target period to the aforementioned non-target period, the predetermined limit value and the rate of change of the predetermined limit value at the end of the target period and the predetermined limit value and the rate of change of the predetermined limit value at the start of the aforementioned non-target period shall be the same. The control device for a hybrid vehicle according to feature 1.

3. The target value of the system torque is set by performing an annealing process on the requested drive torque. The predetermined limit value during the aforementioned period is determined based on the required drive torque. The predetermined limit value during the non-applicable period is determined based on the target value of the system torque. A control device for a hybrid vehicle according to claim 1 or 2.

4. The driver's intention to accelerate or decelerate is determined by switching between releasing the accelerator and pressing the accelerator. A control device for a hybrid vehicle according to claim 1 or 2.

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