Hybrid vehicles

Abstract

A hybrid vehicle comprises: an engine and a motor; and a control device that controls the engine and the motor. In the hybrid vehicle, when the vehicle decelerates and stops in an automatic driving mode that travels independently of a driver's operation and causes the engine to operate under load, the control device sets the maximum speed among a plurality of candidate speeds as a lower control speed limit of the engine, and controls the engine in a manner such that the engine operates under load within a range above the lower control speed limit.

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle. Background Art

[0002] In the past, as such a hybrid vehicle, a hybrid vehicle has been proposed, which includes an engine, a generator connected to the engine via a gear mechanism, a motor for driving, and a power storage device connected to the generator and the motor via a power line, and the hybrid vehicle sets a target power generation of the generator according to vehicle information, and sets the engine speed and the load torque of the generator according to the target power generation of the generator to control the engine and the generator (for example, refer to Japanese Patent Laid-Open No. 2019-214309). In this hybrid vehicle, when the gear mechanism's tooth noise suppression control condition is met, the engine speed is increased compared to when the condition is not met, so that the tooth noise is difficult to be distinguished through the engine sound. Summary of the invention

[0003] In such a hybrid vehicle, when the engine is operated under load when the vehicle decelerates and stops in an automatic driving mode that allows the vehicle to travel independently of the driver's operation, if the engine control lower limit speed changes multiple times, the engine speed changes multiple times, which may cause a sense of discomfort to the driver.

[0004] A main purpose of the hybrid vehicle of the present invention is to suppress the feeling of discomfort caused to the driver when the vehicle is decelerated and stopped in the automatic driving mode.

[0005] In order to achieve the above-mentioned main object, the hybrid vehicle of the present invention adopts the following means.

[0006] The present invention provides a hybrid vehicle having:

[0007] Engines and motors; and

[0008] A control device for controlling the engine and the motor;

[0009] In the hybrid vehicle,

[0010] When the engine is operated under load when the vehicle decelerates and stops in an automatic driving mode that travels independently of the driver's operation, the control device sets the maximum speed among a plurality of candidate speeds as a lower control limit speed of the engine, and controls the engine in a manner such that the engine is operated under load within a range above the lower control limit speed.

[0011] In the hybrid vehicle of the present invention, when the engine is operated under load when the vehicle is decelerated and stopped in the automatic driving mode that is driven independently of the driver's operation, the maximum speed among a plurality of candidate speeds is set as the engine's control lower limit speed, and the engine is controlled in a manner that the engine is operated under load within a range above the control lower limit speed. Thus, it is possible to suppress the engine's control lower limit speed from being switched when the engine is operated under load when the vehicle is decelerated and stopped in the automatic driving mode, and suppress the engine's speed from changing. As a result, it is possible to suppress the driver from feeling uncomfortable.

[0012] In the hybrid vehicle of the present invention, the motor may be connected to the drive wheels via a mechanical connection portion, and the plurality of candidate speeds may include a first speed for suppressing a low sound of the engine and a second speed greater than the first speed for suppressing a tooth hitting sound in the mechanical connection portion.

[0013] In the hybrid vehicle of the present invention, the control device may also set the speed selected from the plurality of candidate speeds according to the brake operation amount as the control lower limit speed when the engine is operated under load when the vehicle is decelerated and stopped in the normal driving mode driven by the driver's operation, and control the engine so that the engine is operated under load within a range above the control lower limit speed. In this way, when the engine is operated under load when the vehicle is decelerated and stopped in the normal driving mode, the control lower limit speed can be appropriately changed.

[0014] In this case, the present invention may further include: a second motor; and a planetary gear, wherein the planetary gear connects three rotating elements to the second motor, the engine, and a drive shaft connected to the drive wheel in the order in which they are arranged in the collinear diagram, the motor being connected to the drive wheel via a mechanical connection portion, the plurality of candidate rotational speeds being a first rotational speed for suppressing a low sound of the engine and a second rotational speed greater than the first rotational speed for suppressing a tooth hitting sound in the mechanical connection portion, and the control device sets the first rotational speed to the control lower limit rotational speed when it is determined based on the brake operation amount that a tooth hitting sound condition related to the tooth hitting sound in the mechanical connection portion is not satisfied when the engine is operated under load when the vehicle is decelerated and stopped in the normal driving mode, and sets the second rotational speed to the control lower limit rotational speed when it is determined that the tooth hitting sound condition is satisfied, and sets the second rotational speed to the control lower limit rotational speed when the engine is operated under load when the vehicle is decelerated and stopped in the automatic driving mode. In the case of this hardware structure, when the engine speed is the second speed, the torque for forward travel output to the drive shaft via the planetary gear due to the load operation of the engine and the driving of the second motor becomes smaller than that at the first speed, and the torque for forward travel output from the motor to the drive shaft becomes larger. Therefore, when the engine is operated under load when the vehicle is decelerated and stopped in the normal driving mode, the lower limit speed of the engine control is set according to whether the tooth rattle condition is satisfied, so that the tooth rattle in the mechanical connection part can be suppressed. It is possible to suppress the lower limit speed of the engine control from being switched according to whether the tooth rattle condition is satisfied when the engine is operated under load when the vehicle is decelerated and stopped in the automatic driving mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like symbols represent like elements, and in which:

[0016] Figure 1 This is a schematic structural diagram showing the structure of a hybrid vehicle as one embodiment of the present invention.

[0017] Figure 2 is a flowchart showing an example of a control routine.

[0018] Figure 3 It is an explanatory diagram showing an example of a temporary required torque map.

[0019] Figure 4 It is an explanatory diagram showing an example of an operation line of the engine and a state of a temporary rotation speed.

[0020] Figure 5This is a collinear diagram showing an example of the relationship between the rotation speed and torque of the rotating elements of the planetary gear.

[0021] Figure 6 : is a flowchart showing an example of the control lower limit rotation speed setting process.

[0022] Figure 7 This is an explanatory diagram showing an example of the vehicle speed, brake position, required torque, required power, and lower limit speed for engine control when the vehicle is decelerated and stopped in the automatic driving mode. DETAILED DESCRIPTION

[0023] Next, specific embodiments of the present invention will be described using examples.

[0024] Figure 1 1 is a schematic structural diagram showing the structure of a hybrid vehicle 20 as one embodiment of the present invention. As shown in the figure, the hybrid vehicle 20 of the embodiment includes an engine 22, a planetary gear 30, motors MG1, MG2, inverters 41, 42, a battery 50 as a power storage device, a hydraulic brake device 60 as a braking force applying device, a steering device 68, a navigation device 69, a surrounding detection device 90, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

[0025] The engine 22 is an internal combustion engine that uses gasoline, light oil or the like as fuel to output power. A crankshaft 23 of the engine 22 is connected to a planetary gear 30 via a damper 28. The engine 22 is operated and controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 24.

[0026] The engine ECU 24 is provided with a microcomputer having a CPU, a ROM, a RAM, a flash memory, an input / output port, and a communication port, which are not shown in the figure. Signals from various sensors required for operating the engine 22 are input to the engine ECU 24 via the input port. As the signal input to the engine ECU 24, for example, the crank angle θcr from the crank position sensor 23a for detecting the rotational position of the crankshaft 23 of the engine 22 and the cooling water temperature Tw from the water temperature sensor 142 for detecting the temperature of the cooling water of the engine 22 can be cited. Various control signals for operating the engine 22 are output from the engine ECU 24 via the output port. The engine ECU 24 is connected to the HVECU 70 via the communication port. The engine ECU 24 calculates the rotation speed Ne of the engine 22 based on the crank angle θcr from the crank position sensor 23a.

[0027] The planetary gear 30 is configured as a single pinion type planetary gear mechanism, and includes a sun gear 31 of an external gear, a ring gear 32 of an internal gear, a plurality of pinion gears 33 meshing with the sun gear 31 and the ring gear 32, respectively, and a gear carrier 34 supporting the plurality of pinion gears 33 in a manner that allows for self-rotation and orbital revolving. The rotor of the motor MG1 is connected to the sun gear 31. The drive shaft 36 is connected to the ring gear 32, and the drive shaft 36 is connected to the drive wheel 39 via a differential gear 38 and a gear mechanism 37. The motor MG2 is connected to the drive shaft 36 via a reduction gear 35. The crankshaft 23 of the engine 22 is connected to the gear carrier 34 via a shock absorber 28.

[0028] The motor MG1 is configured as a synchronous generator motor, and as described above, the rotor of the motor MG1 is connected to the sun gear 31 of the planetary gear 30. The motor MG2 is configured as a synchronous generator motor in the same manner as the motor MG1, and as described above, the rotor of the motor MG2 is connected to the drive shaft 36 via the reduction gear 35. The inverters 41 and 42 are used to drive the motors MG1 and MG2, and are connected to the battery 50 via the power line 54. The capacitor 57 for smoothing is installed on the power line 54. The motor electronic control unit (hereinafter referred to as "motor ECU") 40 controls the switching of a plurality of switching elements (not shown) of the inverters 41 and 42, so that the motors MG1 and MG2 are rotationally driven.

[0029] The motor ECU 40 is provided with a microcomputer having a CPU, a ROM, a RAM, a flash memory, an input / output port, and a communication port, which are not shown in the figure. Signals from various sensors required for driving and controlling the motors MG1 and MG2 are input to the motor ECU 40 via the input port. As the signals input to the motor ECU 40, for example, the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position detection sensors 43 and 44 that detect the rotational positions of the rotors of the motors MG1 and MG2, and the phase currents Iu1, Iv1, Iu2, and Iv2 from the current sensors (not shown) that detect the phase currents flowing in the respective phases of the motors MG1 and MG2 can be cited. Switch control signals of a plurality of switching elements (not shown) of the inverters 41 and 42 are output from the motor ECU 40 via the output port. The motor ECU 40 is connected to the HVECU 70 via the communication port. The motor ECU 40 calculates the rotational speed Nm1 of the motor MG1 based on the rotational position θm1 of the rotor of the motor MG1 from the rotational position detection sensor 43. The motor ECU 40 calculates the rotation speed Nm2 of the motor MG2 based on the rotation position θm2 of the rotor of the motor MG2 detected by the rotation position detection sensor 44 .

[0030] The battery 50 is, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the inverters 41 and 42 via the power line 54 as described above. The battery 50 is managed by a battery electronic control unit 52 (hereinafter referred to as a "battery ECU").

[0031] The battery ECU 52 is equipped with a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and a communication port, which are not shown in the figure. Signals from various sensors required for managing the battery 50 are input to the battery ECU 52 via the input port. As the signal input to the battery ECU 52, for example, the voltage Vb of the battery 50 from the voltage sensor 51a installed between the terminals of the battery 50 and the current Ib of the battery 50 from the current sensor 51b installed at the output terminal of the battery 50 can be cited. The battery ECU 52 is connected to the HVECU 70 via the communication port. The battery ECU 52 calculates the power storage ratio SOC based on the integrated value of the current Ib of the battery 50 from the current sensor 51b. The power storage ratio SOC is the ratio of the capacity of the electric power that can be discharged from the battery 50 to the total capacity of the battery 50.

[0032] The hydraulic brake device 60 includes a plurality of brake pads 62 respectively mounted on the driving wheel 39 and the driven wheel (not shown) and a brake actuator 64. The brake actuator 64 is configured as an actuator for applying a braking force to the driving wheel 39 and the driven wheel by adjusting the oil pressure of a plurality of brake wheel cylinders (not shown) that respectively drive the plurality of brake pads 62. The brake actuator 64 is controlled by the HVECU 70.

[0033] The steering device 68 steers the front wheels among the driving wheels 39 and the driven wheels in the normal driving mode according to the steering operation performed by the driver, and steers the front wheels in the automatic driving mode according to the control signal from the HVECU 70. Here, the normal driving mode is a mode in which the vehicle is driven by the operation of the driver, and the automatic driving mode is a mode in which the vehicle is driven without depending on the operation of the driver.

[0034] The navigation device 69 has a device body, a GPS antenna, and a display, which are not shown in the figure. The device body has a CPU, ROM, RAM, a storage medium (for example, HDD, SSD, etc.), an input / output port, and a communication port, which are not shown in the figure. In the storage medium of the device body, map information and the like are stored. The map information includes service information (for example, sightseeing information, parking lots, etc.), road information of each driving section (for example, between traffic lights, between intersections, etc.), etc. The road information includes distance information, width information, number of lanes information, regional information (urban area, suburbs), category information (ordinary roads, highways), slope information, legal speed information, traffic light information, etc. The GPS antenna receives information related to the current location of the vehicle. The display is configured as a touch panel type display that displays various information and the driver can input various instructions. Among the various instructions, information related to the current location of the vehicle and information related to the planned driving route from the current location of the vehicle to the destination are included. The device body of the navigation device 69 is connected to the HVECU 70 via the communication port.

[0035] In this navigation device 69, when a destination is set by operating the display by the driver, the device body sets a planned driving route from the current location of the vehicle to the destination based on the set destination, map information stored in the storage medium of the device body, and the current location of the vehicle from the GPS antenna, and the set planned driving route is displayed on the display to provide route guidance.

[0036] The surrounding detection device 90 is configured as a device for detecting information about the surroundings of the vehicle, and includes a camera, a millimeter wave radar, a quasi-millimeter wave radar, an infrared laser radar, a sonar, etc. As information about the surroundings of the vehicle, for example, the distance to other vehicles in front of, behind, and to the side of the vehicle can be cited.

[0037] HVECU70 is equipped with a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and a communication port, which are not shown in the figure. Signals from various sensors are input to HVECU70 via the input port. As the signal input to HVECU70, for example, an ignition signal from an ignition switch 80 and a gear position SP from a gear position sensor 82 that detects the operating position of a shift lever 81 can be cited. In addition, the accelerator position AP from an accelerator pedal position sensor 84 that detects the amount of depression of an accelerator pedal 83, the brake position BP from a brake pedal position sensor 86 that detects the amount of depression of a brake pedal 85, and the vehicle speed V from a vehicle speed sensor 88 can also be cited. The surrounding information of the vehicle from the surrounding detection device 90 and the switch signal from the automatic driving switch 91 that indicates the switching between the normal driving mode and the automatic driving mode can also be cited. Various control signals are output from HVECU70 via the output port. As the signal output from the HVECU 70, for example, there can be cited a control signal to the steering device 68 in the automatic driving mode and a control signal to the brake actuator 64 of the hydraulic brake device 60. As described above, the HVECU 70 is connected to the engine ECU 24, the motor ECU 40, the battery ECU 52, the brake ECU 66, and the navigation device 69 via the communication port.

[0038] In the hybrid vehicle 20 of the embodiment thus constructed, the engine 22, the motors MG1 and MG2, and the hydraulic brake device 60 are controlled by the coordinated control of the HVECU 70, the engine ECU 24, and the motor ECU 40 in the normal driving mode (the automatic driving switch 91 is turned off) and the automatic driving mode (the automatic driving switch 91 is turned on) so as to perform hybrid driving (HV driving) and electric driving (EV driving) according to the accelerator position AP and the brake position BP. Here, the HV driving is driving accompanied by driving of the engine 22, and the EV driving is driving not accompanied by driving of the engine 22. The accelerator position AP and the brake position BP use the values ​​detected by the accelerator pedal position sensor 84 and the brake pedal position sensor 86 in the normal driving mode, and use the values ​​set (simulated) based on the information from the navigation device 69 (for example, map information, the current location of the vehicle, the planned driving route, etc.), the vehicle speed V from the vehicle speed sensor 88, the vehicle surrounding information from the surrounding detection device 90, etc. in the automatic driving mode. In the automatic driving mode, the HVECU 70 controls the steering device 68 so as to maintain the lane, change the lane, etc. based on information from the navigation device 69, the vehicle speed V from the vehicle speed sensor 88, and the vehicle surrounding information from the surrounding detection device 90.

[0039] Next, the operation of the hybrid vehicle 20 of the embodiment thus constructed will be described. In particular, the control of the engine 22 and the motors MG1 and MG2 when the vehicle is decelerated and stopped in the normal driving mode and the automatic driving mode will be described. In addition, at this time, the hydraulic brake device 60 is controlled by the HVECU 70 so that the braking force based on the brake position BP acts on the driving wheel 39 and the driven wheel.

[0040] Figure 2 1 is a flowchart showing an example of a control routine executed by the HVECU 70. This routine is repeatedly executed when the accelerator is off in the normal driving mode and the automatic driving mode. When executing this routine, the HVECU 70 initially inputs data such as the driving mode Md, the vehicle speed V, the brake position BP, the engine 22 speed Ne, and the required power Pe* (step S100).

[0041] Here, regarding the driving mode Md, the driving mode (normal driving mode or automatic driving mode) set according to the switch signal from the automatic driving switch 91 is input. Regarding the vehicle speed V, the value detected by the vehicle speed sensor 88 is input. Regarding the brake position BP, in the normal driving mode, the value detected by the brake pedal position sensor 86 is input, and in the automatic driving mode, the value set according to the information from the navigation device 69, the vehicle speed V from the vehicle speed sensor 88, the surrounding information of the vehicle from the surrounding detection device 90, etc. is input.

[0042] Regarding the rotation speed Ne of the engine 22, the value calculated by the engine ECU 24 is input through communication. Regarding the required power Pe* of the engine 22, the value set according to the required power setting routine (not shown) executed by the HVECU 70 is input. In the required power setting routine, the HVECU 70 sets the required power Pe* to a value of 0 when the load operation of the engine 22 is not required, and sets the required power Pe* to a positive value when the load operation of the engine 22 is required. As the case where the load operation of the engine 22 is required, for example, when the power storage ratio SOC of the battery 50 is below the threshold value Sref (the battery 50 is required to be forced to charge), when the cooling water temperature Tw of the engine 22 is below the threshold value Twref (the engine 22 is required to warm up), etc. For the required power Pe* when the load operation of the engine 22 is required, either a constant value or a value based on the power storage ratio SOC of the battery 50, the cooling water temperature Tw of the engine 22, etc. can be set.

[0043] When the data is input in this way, the required torque Td* required for the drive shaft 36 is set according to the vehicle speed V and the brake position BP (step S110). This processing is performed, for example, by applying the vehicle speed V to the temporary required torque map, setting the temporary torque Tdtmp as a temporary value of the required torque Td*, setting the temporary torque Tdtmp for the required torque Td* when the vehicle speed V is greater than the threshold value Vref1, and setting the temporary torque Tdtmp for the required torque Td* when the vehicle speed V is less than the threshold value Vref1. The temporary torque map is pre-set as the relationship between the vehicle speed V and the temporary torque Tdtmp, and is stored in the ROM or flash memory of the HVECU 70. Figure 3 : is an explanatory diagram showing an example of a mapping for temporary required torque. As shown in the figure, regarding the temporary torque Tdtmp, in the area where the vehicle speed V is above the threshold value Vref1, a value below 0 is set, and in the area where the vehicle speed V is less than the threshold value Vref1, a positive value (so-called creep torque) is set. The threshold value Vref1 is set as a boundary value for whether it is necessary to output a creep torque to the drive shaft 36, for example, about 7km / h to 10km / h is used. Regarding the correction coefficient kbp, when the brake position BP is less than the threshold value BPref, a value of 1 is set, and when the brake position BP is above the threshold value BPref, a value greater than 0 and less than 1 is set, for example, a value that gradually decreases from value 1 to value 0 as the brake position BP increases. Therefore, when the vehicle speed V is less than the threshold value Vref1, when the brake position BP is above the threshold value BPref, the required torque Td* (creep torque) required for the drive shaft 36 is made smaller than when the brake position BP is less than the threshold value BPref.

[0044] Next, it is checked whether the required power Pe* of the engine 22 is a value of 0 or a positive value (step S120). When the required power Pe* of the engine 22 is a value of 0, it is determined that the load operation of the engine 22 is not required, and the torque command Tm1* of the motor MG1 is set to a value of 0 (step S140), and the torque command Tm2* of the motor MG2 is calculated by equation (1) using the required torque Td* and the gear ratio Gr of the reduction gear 35 (step S150). Here, equation (1) is an equation for setting the torque command Tm2* of the motor MG2 so that the required torque Td* is output to the drive shaft 36.

[0045] Tm2*=Td* / Gr (1)

[0046] Then, the no-load operation command of the engine 22 is sent to the engine ECU 24, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2 are sent to the motor ECU 40 (step S160), and this routine ends. When the engine ECU 24 receives the no-load operation command of the engine 22, it controls the operation of the engine 22 (intake air amount control, fuel injection control, ignition control, etc.) in such a way that the engine 22 performs no-load operation (idling operation) at a prescribed speed Ne0. As the prescribed speed Ne0, for example, about 1000 rpm to 1100 rpm is used. When the motor ECU 40 receives the torque commands Tm1* and Tm2* of the motors MG1 and MG2, it controls the drive of the motors MG1 and MG2 (switching control of the plurality of switching elements of the inverters 41 and 42) in such a way that the motors MG1 and MG2 are driven respectively according to the torque commands Tm1* and Tm2*.

[0047] When the required power Pe* of the engine 22 is a positive value in step S120, it is determined that the load operation of the engine 22 is required, and the vehicle speed V is compared with the threshold value Vref2 which is lower than the above-mentioned threshold value Vref1 (step S130). Here, the threshold value Vref2 is a threshold value for determining whether the load operation of the engine 22 is permitted, and, for example, about 2 km / h to 4 km / h is used. When the vehicle speed V is higher than the threshold value Vref2, it is determined that the load operation of the engine 22 is prohibited, and the processing after step S140 is executed. The details will be described later. When the engine 22 is operated under load and the motor MG1 is regeneratively driven, the torque for forward travel caused by these acts on the drive shaft 36 via the planetary gear 30. Therefore, in order to stabilize the behavior of the vehicle when decelerating, the load operation of the engine 22 is prohibited when the vehicle speed V is higher than the threshold value Vref2.

[0048] When the vehicle speed V is less than the threshold value Vref2 in step S140, it is determined that the load operation of the engine 22 is permitted, and the control lower limit speed Nemin of the engine 22 is set by the control lower limit speed setting process described later (step S170). Next, based on the required power Pe* of the engine 22 and the operation line for efficiently operating the engine 22, a temporary speed Netmp is set as a temporary value of the target speed Ne* of the engine 22 (step S180). Figure 4 1 is an explanatory diagram showing an example of an operation line of the engine 22 and the setting of the temporary rotation speed Netmp. The process of step S170 is performed by setting the rotation speed at the intersection of the curve where the required power Pe* of the engine 22 is constant and the operation line of the engine 22 as the temporary rotation speed Netmp.

[0049] Then, the temporary speed Netmp of the engine 22 is protected at the lower limit by the control lower speed limit Nemin, the target speed Ne* of the engine 22 is set (step S190), and the target torque Te* of the engine 22 is set to a value obtained by dividing the required power Pe* of the engine 22 by the target speed Ne* (step S200).

[0050] When the target speed Ne* and the target torque Te* of the engine 22 are set in this way, the torque command Tm1* of the motor MG1 is calculated by equation (2) using the speed Ne of the engine 22, the target speed Ne*, the target torque Te*, and the gear ratio ρ of the planetary gear 30 (step S210). Next, the torque command Tm2* of the motor MG2 is calculated by equation (3) using the required torque Td*, the torque command Tm1* of the motor MG1, the gear ratio ρ of the planetary gear 30, and the gear ratio Gr of the reduction gear 35 (step S220).

[0051] Tm1*=-Te* / (1+ρ)+kp·(Ne*-Ne)+ki·∫(Ne*-Ne)dt (2)

[0052] Tm2*=(Td*+Tm1* / ρ) / Gr (3)

[0053] Figure 5 : is a collinear diagram showing an example of the relationship between the rotation speed and torque of the rotating elements of the planetary gear 30. In the figure, the S axis represents the rotation speed of the sun gear 31 (the rotation speed Nm1 of the motor MG1), the C axis represents the rotation speed of the gear carrier 34 (the rotation speed Ne of the engine 22), and the R axis represents the rotation speed of the ring gear 32 (the rotation speed Nd of the drive shaft 36, and the rotation speed Nm2 of the motor MG2 divided by the gear ratio Gr of the reduction gear 35). In addition, in the figure, the two thick arrows of the R axis represent the torque (-Tm1* / ρ) output to the drive shaft 36 via the planetary gear 30 due to the load operation of the engine 22 and the regenerative drive of the motor MG1, and the torque (Tm2*·Gr) output from the motor MG2 to the drive shaft 36 via the reduction gear 35 when the motor MG2 is driven according to the torque command Tm2*.

[0054] Formula (2) is a relational expression in feedback control for rotating the engine 22 at the target speed Ne*. The first term on the right is a feedforward term, and the second and third terms on the right are a proportional term and an integral term in the feedback term. In Formula (2), the first term on the right can be obtained from Figure 5 The collinear diagram of is easily derived. In equation (2), the second term "kp" on the right is the gain of the proportional term, and the third term "ki" on the right is the gain of the integral term. Equation (3) is a formula for setting the torque command Tm2* of the motor MG2 in the same manner as equation (1) so that the required torque Td* is output to the drive shaft 36, which can be Figure 5 The nomograms can be easily exported.

[0055] Then, the target speed Ne* and target torque Te* of the engine 22 are sent to the engine ECU 24, and the torque instructions Tm1* and Tm2* of the motors MG1 and MG2 are sent to the motor ECU 40 (step S230), and this routine is terminated. When the engine ECU 24 receives the target speed Ne* and target torque Te* of the engine 22, it controls the operation of the engine 22 so that the engine 22 performs load operation according to the target speed Ne* and target torque Te*. The drive control of the motors MG1 and MG2 by the motor ECU 40 has been described above.

[0056] Next, use Figure 6 The control is processed by setting the lower speed limit. Figure 2 The process of step S170 of the control routine is a process of setting the control lower limit rotation speed Nemin of the engine 22. In the control lower limit rotation speed setting process, the HVECU 70 first checks whether the driving mode Md is the normal driving mode or the automatic driving mode (step S300).

[0057] If the driving mode Md is the normal driving mode in step S300, it is determined whether the rattle noise condition is satisfied (step S310). If it is determined that the rattle noise condition is not satisfied, the predetermined speed Ne1 is set as the control lower limit speed Nemin of the engine 22 (step S320), and the control lower limit speed setting process is terminated.

[0058] Here, the predetermined rotation speed Ne1 is set to the lower limit value of the rotation speed range that can suppress the muffled sound of the engine 22, for example, about 1200 rpm to 1300 rpm. Hereinafter, the following control is referred to as "first control": the predetermined rotation speed Ne1 is set to the control lower limit rotation speed Nemin of the engine 22, and Figure 2 The target speed Ne* of the engine 22, the target torque Te*, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2 are set by the processing of steps S190 to S220 to control the engine 22 and the motors MG1 and MG2.

[0059] The tooth noise condition is the following condition: when the first control is executed, the actual torque of the motor MG2 continues to be near the value 0, and the tooth noise may be generated with a certain degree of frequency in the reduction gear 35 connected to the motor MG2. For example, the required torque Td* and the required power Pe* are applied to the tooth noise relationship to perform the processing of step S310. The tooth noise relationship is predetermined as a relationship between the required torque Td*, the required power Pe*, and whether the tooth noise condition is met, and is stored in the ROM or flash memory of the HVECU 70. The tooth noise relationship is set as follows: the torque command Tm2* of the motor MG2 is set according to the required torque Td*, the required power Pe*, and the lower limit speed Nemin for control (refer to Figure 2 Steps S180 to S220).

[0060] When the HVECU 70 determines in step S310 that the teeth hitting noise condition is satisfied, the specified speed Ne2 which is greater than the specified speed Ne1 is set as the lower limit speed Nemin for control of the engine 22 (step S330), and the lower limit speed setting process for control is terminated. Here, the specified speed Ne2 is set to the lower limit value of the speed range that can suppress the occurrence of teeth hitting noise with a certain degree of frequency in the reduction gear 35, etc., for example, about 1400rpm to 1500rpm is used. Hereinafter, the following control is referred to as the "second control": the specified speed Ne2 is set to the lower limit speed Nemin for control of the engine 22, and the lower limit speed Ne2 is set to the lower limit speed Nemin for control of the engine 22 by Figure 2 The target speed Ne*, target torque Te*, and torque commands Tm1* and Tm2* of the motors MG1 and MG2 are set by processing in steps S190 to S220 to control the engine 22, the motors MG1 and MG2. In the second control, compared with the first control, the target speed Ne* of the engine 22 becomes larger, and the target torque Te* becomes smaller, so the torque command Tm1* of the motor MG1 becomes larger, that is, close to the value 0 (refer to formula (2)). When the required torque Td* is a positive value (creep torque), the torque command Tm2* of the motor MG2 becomes larger (refer to formula (3)). As a result, the actual torque of the motor MG2 can be prevented from continuing to be near the value 0, and the tooth hitting sound can be prevented from being generated at a certain frequency in the reduction gear 35, etc.

[0061] When the driving mode Md is the automatic driving mode in step S300, the HVECU 70 sets the specified speed Ne2 to the control lower limit speed Nemin of the engine 22 without determining whether the tooth noise condition is met (step S340), and ends the control lower limit speed setting process. In this case, regardless of whether the tooth noise condition is met, the HVECU 70 will perform the second control. As a result, when the vehicle decelerates and stops in the automatic driving mode, the control lower limit speed Nemin of the engine 22 is suppressed from being switched while the engine 22 is being operated under load, and the speed Ne of the engine 22 can be suppressed from changing sharply. As a result, it is possible to suppress the sense of disharmony caused to the driver.

[0062] Figure 7 This is an explanatory diagram showing an example of the vehicle speed V, brake position BP, required torque Td*, required power Pe*, and lower control limit speed Nemin of the engine 22 when the vehicle decelerates and stops in the automatic driving mode. In the figure, regarding the target speed Ne* of the engine 22, the solid line represents the situation of the embodiment, and the dashed line represents the situation of the comparative example. In the comparative example, in the automatic driving mode, as in the normal driving mode, the prescribed speed Ne1 or the prescribed speed Ne2 is set as the lower control limit speed Nemin of the engine 22 according to whether the tooth hitting noise condition is satisfied. In addition, as described above, the required torque Td* is set according to the vehicle speed V and the brake position BP, and whether the tooth hitting noise condition is satisfied is set according to the required torque Td* and the required power Pe*.

[0063] As shown in the figure, in the embodiment and the comparative example, when the vehicle speed V decreases and becomes less than the threshold value Vref1 (time t11), the required torque Td* becomes a positive value and the output of the creep torque starts, and when the vehicle speed V becomes less than the threshold value Vref2 (time t12), the load operation of the engine 22 starts. In the comparative example, when the engine 22 is operated under load (time t12~), when the ratcheting condition is not satisfied (time t12~t13), the prescribed speed Ne1 is set to the control lower limit speed Nemin of the engine 22, and when the ratcheting condition is satisfied (time t13~), the prescribed speed Ne2 is set to the control lower limit speed Nemin of the engine 22. Therefore, when the vehicle is decelerated and stopped in the automatic driving mode, the control lower limit speed Nemin of the engine 22 is switched and the speed Ne of the engine 22 changes sharply, which may cause a sense of discomfort to the driver. In contrast, in the embodiment, when the engine 22 is operated under load (from time t12), the predetermined speed Ne2 is set to the control lower speed limit Nemin of the engine 22 regardless of whether the tooth hitting noise condition is satisfied. This can prevent the control lower speed limit Nemin of the engine 22 from being switched while the engine 22 is operated under load when the vehicle is decelerated and stopped in the automatic driving mode, and can prevent the speed Ne of the engine 22 from changing suddenly. As a result, it can prevent the driver from feeling uncomfortable.

[0064] In the hybrid vehicle 20 of the embodiment described above, when the vehicle is decelerated and stopped in the automatic driving mode, when the engine 22 is operated under load, the target speed Ne* of the engine 22 is set to the predetermined speed Ne2 (the larger of the predetermined speeds Ne1 and Ne2), regardless of whether the tooth noise condition is satisfied or not, and the engine 22 is controlled so that the engine 22 is operated under load within a range of not less than the control lower limit speed Nemin. As a result, it is possible to suppress the control lower limit speed Nemin of the engine 22 from being switched while the engine 22 is operated under load when the vehicle is decelerated and stopped in the automatic driving mode, and suppress the speed Ne of the engine 22 from changing suddenly. As a result, it is possible to suppress the driver from feeling uncomfortable.

[0065] In the hybrid vehicle 20 of the embodiment, as the predetermined rotation speed Ne1, the lower limit value of the rotation speed range that can suppress the low-pitched sound of the engine 22 is used, and as the predetermined rotation speed Ne2, the lower limit value of the rotation speed range that can suppress the occurrence of the tooth hitting sound with a certain degree of frequency in the reduction gear 35, etc. is used. However, the predetermined rotation speeds Ne1 and Ne2 are not limited to these. For example, as any of the predetermined rotation speeds Ne1 and Ne2, the lower limit value of the rotation speed range that can suppress the abnormal exhaust sound of the engine 22 may be used.

[0066] In the hybrid vehicle 20 of the embodiment, when the engine 22 is operated under load when the vehicle is decelerated and stopped in the normal driving mode, the specified speed Ne1 or the specified speed Ne2 is set as the lower limit speed Nemin for control of the engine 22, and when the engine 22 is operated under load when the vehicle is decelerated and stopped in the automatic driving mode, the specified speed Ne2 (the larger of the specified speeds Ne1 and Ne2) is set as the target speed Ne* of the engine 22. However, when the engine 22 is operated under load when the vehicle is decelerated and stopped in the normal driving mode, the speed selected from three or more candidate speeds may be set as the lower limit speed Nemin for control of the engine 22, and when the engine 22 is operated under load when the vehicle is decelerated and stopped in the automatic driving mode, the maximum speed among the three or more candidate speeds may be set as the lower limit speed Nemin for control of the engine 22.

[0067] In the hybrid vehicle 20 of the embodiment, the motor MG2 is connected to the drive shaft 36, and the drive shaft 36 is connected to the drive wheel 39 via the reduction gear 35. However, the motor MG2 may be connected to the drive shaft 36 via a transmission. In addition, the motor MG2 may be connected to the drive shaft 36 via the reduction gear 35 or a mechanical connection other than the transmission, such as two gears meshing with each other.

[0068] In the hybrid vehicle 20 of the embodiment, the battery 50 is used as the power storage device. However, a capacitor may be used as the power storage device instead of the battery 50 or in addition to the battery 50.

[0069] The hybrid vehicle 20 of the embodiment includes the engine ECU 24, the motor ECU 40, the battery ECU 52, and the HVECU 70. However, at least two of these may be configured as a single electronic control unit.

[0070] The correspondence between the main elements of the embodiment and the main elements of the invention described in the Summary of the Invention section is described. In the embodiment, the engine 22 corresponds to the "engine", the motor MG2 corresponds to the "motor", the battery 50 corresponds to the "power storage device", and the HVECU 70, the engine ECU 24, and the motor ECU 40 correspond to the "control device".

[0071] In addition, regarding the correspondence between the main elements of the embodiment and the main elements of the invention described in the Summary of the Invention section, the embodiment is an example for specifically describing the method for implementing the invention described in the Summary of the Invention section, and therefore does not limit the elements of the invention described in the Summary of the Invention section. That is, the interpretation of the invention described in the Summary of the Invention section should be based on the description of that section, and the embodiment is merely a specific example of the invention described in the Summary of the Invention section.

[0072] Although specific embodiments of the present invention have been described above using the examples, the present invention is not limited to such examples at all and can of course be implemented in various forms within the scope not departing from the gist of the present invention.

[0073] The present invention can be used in the manufacturing industry of hybrid vehicles, etc.

Claims

1. A hybrid vehicle comprising: Engine, first motor and second motor; A planetary gear including a sun gear, a gear carrier and a ring gear, wherein the second motor is connected to the sun gear, the engine is connected to the gear carrier, and a drive shaft connected to a drive wheel is connected to the ring gear; and A control device that controls the engine and the first motor and the second motor; in, The control device sets the maximum speed among a plurality of candidate speeds as the lower control speed limit of the engine, and controls the engine so that the engine is operated under load within a range above the lower control speed limit when the vehicle is decelerated and the vehicle speed is less than a predetermined vehicle speed and the engine is operated under load while the second motor is regeneratively driven, in an automatic driving mode in which the vehicle is driven independently of the driver's operation, The first motor is connected to the drive shaft via a mechanical connection portion. The plurality of candidate rotation speeds include a first rotation speed for suppressing a low-pitched sound of the engine and a second rotation speed greater than the first rotation speed for suppressing a teeth rattling sound in the mechanical connection portion.

2. The hybrid vehicle according to claim 1, wherein: The control device sets a speed selected from the plurality of candidate speeds according to the brake operation amount as the control lower limit speed, when the vehicle decelerates and the vehicle speed is less than the predetermined vehicle speed in a normal driving mode driven by the driver and the engine is operated under load at the same time as the second motor is regeneratively driven, and controls the engine in a manner such that the engine operates under load within a range above the control lower limit speed.

3. The hybrid vehicle according to claim 2, wherein: The control device sets the first speed to the control lower limit speed when it is determined based on the brake operation amount that a tooth noise condition related to the tooth noise in the mechanical connection portion is not satisfied, and sets the second speed to the control lower limit speed when it is determined that the tooth noise condition is satisfied, when the vehicle is decelerated in the normal driving mode and the vehicle speed is less than the predetermined vehicle speed and the engine is operated under load while the second motor is regeneratively driven. The control device sets the second rotation speed as the control lower limit rotation speed when the vehicle is decelerated in the automatic driving mode and the vehicle speed is less than the predetermined vehicle speed and the engine is operated under load while the second motor is regeneratively driven.

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