Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle in which gear rattle is suppressed and also deterioration in fuel economy is suppressed.SOLUTION: A control device of a hybrid vehicle which is equipped with an engine, an electric motor, a damper device provided between the engine and the electric motor and a catalyst for purifying exhaust gas from the engine, is provided with: a measuring part that measures a twisting angle with respect to input torque to the damper device; a calculating part that calculates hysteresis torque which is a difference in the input torque at the predetermined twisting angle between when the twisting angle increases and when the angle decreases, on the basis of the measured result of the twisting angle; and an engine control part that decreases torque required in the engine during execution of catalyst warming-up control based on ignition timing retard of the engine more, as magnitude of the hysteresis torque is larger.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] A hybrid vehicle is known that acquires the spring characteristics of a damper device based on the temperature of the damper device and controls the required torque of the engine according to the spring characteristics so as to suppress gear rattle noise caused by fluctuations in engine rotation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-051708 Summary of the Invention [Problem to be solved by the invention]

[0004] The engine rotation fluctuations described above increase during catalyst warm-up control by retarding the ignition timing. Furthermore, the above-described technology estimates the spring characteristics of the damper device based on the temperature of the damper device, which may result in inaccurate estimation of the spring characteristics. For this reason, if the required engine torque is maintained higher than necessary to suppress rattle noise during catalyst warm-up control, fuel economy may deteriorate.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for a hybrid vehicle that suppresses gear rattle noise while also suppressing deterioration in fuel economy. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a hybrid vehicle having an engine, an electric motor, a damper device provided between the engine and the electric motor, and a catalyst that purifies the exhaust gas of the engine, the control device comprising: a measurement unit that measures a torsion angle relative to an input torque to the damper device; a calculation unit that calculates a hysteresis torque, which is the difference in the input torque at a predetermined torsion angle when the torsion angle is increasing and when the torsion angle is decreasing, based on the measurement result of the torsion angle; and an engine control unit that reduces the required torque of the engine during execution of catalyst warm-up control by retarding the ignition timing of the engine the larger the magnitude of the hysteresis torque. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a control device for a hybrid vehicle that suppresses gear rattle noise while also suppressing deterioration in fuel economy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Figure 2] FIG. 2 is a flowchart showing an example of control executed by the ECU. [Figure 3] FIG. 3A is an example of a map showing the relationship between the input torque Tin and the torsion angle φ in the damper device, and FIG. 3B is an example of a map defining the relationship between the magnitude of the hysteresis torque Th and the amount of reduction in the required torque in catalyst warm-up control. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Hybrid vehicle configuration] FIG. 1 is a schematic diagram of a hybrid vehicle 10. The hybrid vehicle 10 includes a first drive unit 16, a second drive unit 18, a final drive unit 20, and a pair of left and right axles 22 in a power transmission path between an engine 12 and a pair of left and right drive wheels 14. The engine 12 is a gasoline engine, and is connected to an exhaust passage 121. A catalyst 122 that purifies the exhaust of the engine 12 is provided in the exhaust passage 121. A damper device 26 that absorbs torque fluctuations is connected to a crankshaft 24 of the engine 12. The damper device 26 includes a first rotating element 26a connected to the crankshaft 24 and a second rotating element 26b connected to a differential mechanism 30 via an input shaft 28. Multiple types of springs 32 and friction mechanisms 34 are interposed between the first rotating element 26a and the second rotating element 26b, and the stiffness value (spring constant) corresponding to a change in torsion angle φ with respect to a change in input torque Tin is changed in a stepwise manner. A torque limiter 35 is provided on the outer peripheral end of the damper device 26.

[0010] The crankshaft 24, which is integrally connected to the first rotating element 26a, is connected to a housing 38 via a mesh brake 36, preventing rotation. The mesh brake 36 has meshing teeth 24a provided on the crankshaft 24, meshing teeth 38a provided on the housing 38, and a meshing sleeve 36a whose inner circumferential surface has meshing teeth that can straddle and mesh with the meshing teeth 24a and 38a. As the meshing sleeve 36a is moved in the axial direction, the crankshaft 24 is engaged with the housing 38 so as not to rotate relative to it, or is released from the housing 38 so as to become rotatable. The meshing sleeve 36a is moved in the axial direction via a hydraulic cylinder or the like, for example, by switching an electromagnetic switching valve or the like provided in the hydraulic control circuit 58 in accordance with a hydraulic control signal Sac supplied from the ECU 90, thereby engaging or disengaging the mesh brake 36.

[0011] The first drive unit 16 includes the engine 12, the differential mechanism 30, and the mesh brake 36, as well as a first motor MG1 and an output gear 40. The differential mechanism 30 is a single-pinion planetary gear device and includes three rotating elements, a sun gear S, a ring gear R, and a carrier CA, that are capable of differential rotation. The first motor MG1 is connected to the sun gear S, the input shaft 28 is connected to the carrier CA, and the output gear 40 is connected to the ring gear R. Therefore, torque transmitted from the engine 12 to the carrier CA of the differential mechanism 30 via the damper device 26 is distributed by the differential mechanism 30 to the first motor MG1 and the output gear 40. When the MG1 rotation speed Nmg1 is controlled by regenerative control or the like, the engine rotation speed Ne is continuously changed and output from the output gear 40. In other words, the differential mechanism 30 and the first motor MG1 function as an electric continuously variable transmission. The first motor MG1 functions alternatively as an electric motor or a generator, and is connected to an electricity storage device 62 via an inverter 60.

[0012] On the other hand, when the rotation of the crankshaft 24 is blocked by the mesh brake 36, i.e., when the rotation of the carrier CA is blocked via the damper device 26, if the first motor MG1 is rotationally driven in the negative rotation direction opposite to the rotation direction of the engine 12, a torque in the same forward rotation direction (vehicle forward direction) as the rotation direction of the engine 12 is applied to the output gear 40 due to a reaction force generated by the mesh brake 36, and the output gear 40 is rotationally driven in the forward rotation direction. If the first motor MG1 is rotationally driven in the same forward rotation direction as the rotation direction of the engine 12, a torque in the reverse rotation direction (vehicle backward direction) opposite to the rotation direction of the engine 12 is applied to the output gear 40 due to a reaction force generated by the mesh brake 36, and the output gear 40 is rotationally driven in the reverse rotation direction. In this case, the torque of the first motor MG1 is amplified in accordance with the gear ratio ρ of the differential mechanism 30 and applied to the damper device 26 connected to the carrier CA. The first motor MG1 is an electric motor that can apply torque to the damper device 26 via the differential mechanism 30.

[0013] The output gear 40 meshes with a large-diameter gear 44 that is disposed on an intermediate shaft 42 that is parallel to the input shaft 28. A mesh clutch 43 is provided between the large-diameter gear 44 and the intermediate shaft 42, and connects and disconnects power transmission therebetween. This mesh clutch 43 has a configuration similar to that of the mesh brake 36, and is switched between an engaged state and a released state via a hydraulic cylinder or the like by switching another electromagnetic switching valve or the like provided in the hydraulic control circuit 58 in accordance with a hydraulic control signal Sac supplied from the ECU 90, thereby connecting and disconnecting power transmission between the large-diameter gear 44 and the intermediate shaft 42. A small-diameter gear 46, which has a smaller diameter than the large-diameter gear 44, is provided on the intermediate shaft 42, and this small-diameter gear 46 meshes with a differential ring gear 48 of the final reduction gear 20. Therefore, the rotation of the output gear 40 is reduced in speed according to the gear ratio between the output gear 40 and the large-diameter gear 44 and the gear ratio between the small-diameter gear 46 and the differential ring gear 48, and is transmitted to the final reduction gear 20, and is further transmitted to the pair of axles 22 via the differential gear mechanism of the final reduction gear 20 to the drive wheels 14. A parking gear 45 is also provided on the intermediate shaft 42 so as to be unable to rotate relative to the axles, and when the parking range is selected, for example by operating the shift lever to the P position for parking, a parking lock pole (not shown) is pressed against and engaged with the parking gear 45 by the biasing force of a spring or the like, and rotation of the various members on the drive wheels 14 side of the intermediate shaft 42 is prevented.

[0014] The second drive unit 18 includes a second motor MG2 and a motor output gear 52 provided on a motor shaft 50 of the second motor MG2. The motor output gear 52 is meshed with the large-diameter gear 44. Therefore, the MG2 rotation speed Nmg2 is reduced in accordance with the gear ratio between the motor output gear 52 and the large-diameter gear 44 and the gear ratio between the small-diameter gear 46 and the differential ring gear 48, and is transmitted to the final reduction gear 20, thereby rotating and driving the drive wheels 14 via the pair of axles 22. The second motor MG2 functions alternatively as an electric motor or a generator, and is connected to an electricity storage device 62 via an inverter 60.

[0015] The hybrid vehicle 10 is equipped with an automatic braking system 66. The automatic braking system 66 electrically controls the brake hydraulic pressure of each wheel brake 67 provided on the driving wheels 14 and non-driving wheels (not shown) in accordance with a brake control signal Sb supplied from the ECU 90.

[0016] The hybrid vehicle 10 configured as described above includes an ECU (Electric Control Unit) 90 as a controller that performs various controls, such as output control of the engine 12 and torque control of the first motor MG1 and the second motor MG2. The ECU 90 is configured with a so-called microcomputer having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, etc., and performs various controls by utilizing the temporary storage function of the RAM and performing signal processing according to programs previously stored in the ROM. In addition, as will be described in detail later, the ECU 90 performs catalyst warm-up control by retarding the ignition timing, and the CPU, RAM, and ROM of the ECU 90 functionally realize a measurement unit, a calculation unit, and an engine control unit.

[0017] Signals representing various information required for control, such as engine rotation speed Ne, vehicle speed V, MG1 rotation speed Nmg1, MG2 rotation speed Nmg2, accelerator operation amount Acc, remaining charge SOC of the power storage device 62, and shift lever operation position Psh, are transmitted to the ECU 90 from, for example, engine rotation speed sensor 70, vehicle speed sensor 72, MG1 rotation speed sensor 74, MG2 rotation speed sensor 76, accelerator operation amount sensor 78, shift position sensor 80, SOC sensor 64, etc. The ECU 90 outputs, for example, an engine control signal Se for controlling engine output via a throttle valve, port injectors, and spark plugs (described later) of the engine 12, a motor control signal Sm for controlling the torque (powering torque, regenerative torque) of the first motor MG1 and the second motor MG2, a hydraulic control signal Sac for switching between engagement and release of the dog brake 36 and the dog clutch 43 via an electromagnetic switching valve or the like of the hydraulic control circuit 58, and a brake control signal Sb for controlling the braking force of the wheel brake 67 via the automatic brake system 66.

[0018] Here, for example, when the temperature of the catalyst 122 drops below the activation temperature, catalyst warm-up control may be executed to warm up the catalyst 122 by retarding the ignition timing of the engine 12. Retarding the ignition timing of the engine 12 reduces the efficiency of the engine 12 and increases heat loss. This increases the exhaust heat energy flowing into the catalyst 122, allowing the catalyst 122 to be warmed up.

[0019] Such retardation of the ignition timing makes the combustion state of the engine 12 unstable, causing the torque of the engine 12 to fluctuate around the torque required for the engine 12. When the torque of the engine 12 crosses zero, from positive to negative or from negative to positive, gear backlash may cause rattle noise. Therefore, by maintaining the torque required for the engine 12 high during execution of catalyst warm-up control so that the torque of the engine 12 does not cross zero, rattle noise can be suppressed. However, if the torque required during execution of catalyst warm-up control is maintained higher than necessary, fuel economy will deteriorate. Therefore, the ECU 90 suppresses the gear rattle noise while also suppressing deterioration in fuel economy by executing the following control.

[0020] [Control performed by ECU90] FIG. 2 is a flowchart showing an example of control executed by the ECU 90. This control is executed repeatedly while the system is running. The ECU 90 determines whether or not a measurement start condition is met (step S1). The measurement start condition is, for example, that the vehicle speed V=0, the shift range=P, the engine rotation speed Ne=0, and there is no engine start request. If any one of these measurement start conditions is not met, the determination in step S1 is No, and this control is terminated.

[0021] If all of the measurement start conditions are met, a Yes determination is made in step S1, and the ECU 90 starts measuring the torsion angle φ relative to the input torque Tin to the damper device 26 (step S2). Specifically, the ECU 90 engages the mesh brake 36 to lock the crankshaft 24 so that it cannot rotate, and applies power control to the first motor MG1 to apply torque (input torque Tin) to the damper device 26 to measure the torsion angle φ. Step S2 is an example of processing executed by the measurement unit.

[0022] Specifically, the MG1 rotational speed Nmg1 is measured by the MG1 rotational speed sensor 74, such as a resolver, while the torque of the first motor MG1 is continuously increased or decreased. This allows the relationship between the input torque Tin and the torsional angle φ to be determined, as shown in FIG. 3A. FIG. 3A is an example of a map showing the relationship between the input torque Tin and the torsional angle φ in the damper device 26. Based on the gear ratio ρ of the differential mechanism 30, the input torque Tin can be calculated from the motor torque of the first motor MG1, and the torsional angle φ can be calculated from the MG1 rotational speed Nmg1. Generally, the relationship between the input torque Tin and the torsional angle φ of the damper device 26 changes symmetrically with respect to the origin 0, as shown in FIG. 3A. Therefore, only one of the positive and negative sides of the torsional angle φ may be measured. If a one-way clutch is provided instead of the dog brake 36 to prevent only reverse rotation of the engine 12, the torsional angle φ may be measured by applying a torque in the reverse rotation direction as the input torque Tin. The relationship between the input torque Tin and the torsion angle φ is established by the action of the spring 32, the friction mechanism 34, and the like.

[0023] The ECU 90 determines whether or not a measurement continuation condition is met during measurement (step S3). The measurement continuation condition is, for example, that the vehicle speed V=0, the shift range=P, and there is no request to start the engine. If any one of these measurement continuation conditions is not met, the determination in step S3 is No, and the ECU 90 interrupts measurement (step S4) and ends this control.

[0024] If all of the measurement continuation conditions are met, the determination in step S3 is Yes, and the ECU 90 determines whether or not the measurement is complete (step S5). Whether or not the measurement is complete can be determined, for example, based on whether or not the first motor MG1 has completed reciprocating rotation within a predetermined angle range for measurement. If the determination in step S5 is No, step S3 is executed again.

[0025] If the answer is Yes in step S5, the ECU 90 calculates hysteresis torque Th based on the measurement result (step S6). The hysteresis torque Th is the difference between the input torque Tin at a predetermined torsion angle φ when the torsion angle φ is increasing and when it is decreasing. The hysteresis torque Th may be the difference between the input torque Tin at a predetermined torsion angle φ. The hysteresis torque Th may also be the difference between the average value of the input torque Tin when the torsion angle φ is increasing and the average value of the input torque Tin when the torsion angle φ is decreasing, within a predetermined range of the torsion angle φ. Step S6 is an example of processing executed by the calculation unit.

[0026] In this way, by locking the crankshaft 24 so that it cannot rotate with the mesh brake 36 and applying the input torque Tin to the damper device 26, the relationship between the input torque Tin and the torsion angle φ can be measured with high accuracy. This also makes it possible to calculate the hysteresis torque Th with high accuracy. Note that the greater the magnitude of the hysteresis torque Th, the greater the vibration damping capacity of the damper device 26 due to friction in the friction mechanism 34. In other words, the greater the magnitude of the hysteresis torque Th, the greater the ability of the damper device 26 to suppress rotation fluctuations in the engine 12.

[0027] Next, the ECU 90 calculates the amount of reduction in the torque required for the engine 12 during catalyst warm-up control based on the magnitude of the hysteresis torque Th (step S7). Fig. 3B is an example of a map that defines the relationship between the magnitude of the hysteresis torque Th and the amount of reduction in the torque required for the catalyst warm-up control. As shown in Fig. 3B, the greater the hysteresis torque Th, the greater the amount of reduction in the torque required.

[0028] 3B, the line segment showing the relationship between the hysteresis torque Th and the reduction amount of the required torque is linear, but is not limited to this and may be curved. Furthermore, the calculation of the reduction amount of the required torque is not limited to such a map, and may be calculated using an arithmetic expression that uses the hysteresis torque Th as an argument.

[0029] Next, the ECU 90 determines whether catalyst warm-up control is being executed (step S8). If the answer is No in step S8, the control is terminated. If the answer is Yes in step S8, the ECU 90 reduces the torque required of the engine 12 while catalyst warm-up control is being executed by the amount of reduction in the required torque described above (step S9). As described above, the greater the magnitude of the hysteresis torque Th, the higher the vibration damping capability of the damper device 26. Therefore, the higher the vibration damping capability of the damper device 26, the more the torque required while catalyst warm-up control is being executed can be reduced, thereby suppressing gear rattle while also suppressing deterioration in fuel economy. The processing of step S9 is an example of processing executed by the engine control unit.

[0030] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0031] 10 Hybrid vehicle 12 Engine 26 Damper device 90 ECU (control unit, measurement unit, calculation unit, and engine control unit) 122 Catalyst MG1 First motor (electric motor)

Claims

[Claim 1] A control device for a hybrid vehicle having an engine, an electric motor, a damper device provided between the engine and the electric motor, and a catalyst for purifying exhaust gas from the engine, a measurement unit that measures a torsion angle relative to an input torque to the damper device; a calculation unit that calculates a hysteresis torque, which is a difference between the input torque at a predetermined torsion angle when the torsion angle is increasing and when the torsion angle is decreasing, based on the measurement result of the torsion angle; a control device for a hybrid vehicle, the control unit configured to reduce the required torque of the engine during execution of catalyst warm-up control by retarding the ignition timing of the engine as the magnitude of the hysteresis torque increases;

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