JP7704091B2 - Hybrid vehicle control device - Google Patents

Description

The present invention relates to a control device for a hybrid vehicle that has a damper installed in the power transmission path between the engine and the electric motor.

There is a well-known control device for a hybrid vehicle that includes an engine, an electric motor that is connected to a power transmission path between the engine and the drive wheels so that power can be transmitted, and a damper that is provided between the engine and the electric motor in the power transmission path. For example, there is a vehicle control device described in Patent Document 1. Patent Document 1 discloses that, with the rotation of the engine crankshaft locked, torque is applied to the damper by powering control of the electric motor to measure the torsion angle of the damper, thereby obtaining hysteresis torque, which is the difference in torque input to the damper when the torsion angle increases and decreases.

JP 2018-79849 A

In engine control, a technique is also well known in which the ignition timing of the engine is retarded when the catalyst installed in the exhaust pipe of the engine is warmed up, compared to when the catalyst is in normal operation and has been warmed up. The greater the retard amount during catalyst warm-up, the more the catalyst warm-up is promoted. However, the greater the retard amount, the more unstable the engine combustion becomes, and, for example, the more likely it is that the NV forcing force of the engine will be increased. For this reason, the retard amount during catalyst warm-up is determined in advance, taking into account, for example, the NV forcing force of the engine that allows NV. "NV" is a general term for noise and vibration generated by a vehicle, and represents at least one of the noise and vibration in the vehicle. Here, the damper has the function of attenuating the forcing force transmitted to the power transmission system. There is room for improvement in terms of achieving both the promotion of catalyst warm-up and the suppression of NV.

The present invention was made against the background of the above circumstances, and its purpose is to provide a control device for a hybrid vehicle that can simultaneously promote catalyst warm-up and suppress NV.

The gist of the first invention is that (a) a control device for a hybrid vehicle including an engine, an electric motor connected to a power transmission path between the engine and drive wheels so as to be capable of transmitting power, and a damper provided between the engine and the electric motor in the power transmission path, (b) a torque is applied to the damper by the electric motor while the engine is stopped, and a torsion angle of the damper is measured, thereby obtaining a hysteresis torque, which is the difference in torque input to the damper when the torsion angle increases and decreases, and (c) when the hysteresis torque is large, the amount of retardation of the ignition timing of the engine during warm-up of a catalyst provided in an exhaust pipe of the engine is set to be large compared to when the hysteresis torque is small.

According to the first invention, when the hysteresis torque obtained while the engine is stopped is large, the amount of retardation of the engine ignition timing during catalyst warm-up is set to be larger than when the hysteresis torque is small, so the catalyst is more easily warmed up the larger the hysteresis torque. When the amount of retardation of the ignition timing is set to be large and the engine's NV forcing force is increased, the large hysteresis torque makes it easier to attenuate the forcing force transmitted to the power transmission system, making it easier to suppress NV. Therefore, it is possible to achieve both promotion of catalyst warm-up and suppression of NV.

1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and a control system for various controls in the vehicle. 1A is a diagram illustrating an example of a maximum ignition retard amount for each hysteresis torque, and FIG. 1B is a diagram illustrating an example of a relationship between the hysteresis torque and a relaxation amount of the retard amount limit value. 4 is a flowchart illustrating a main part of the control operation of the electronic control device.

The following describes in detail an embodiment of the present invention with reference to the drawings.

Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrates the main parts of the control functions for various controls in the vehicle 10. The vehicle 10 is a hybrid vehicle equipped with an engine 12, a first electric motor MG1, and a second electric motor MG2, which function as power sources. In the vehicle 10, a damper 16, a differential mechanism 18, an output gear 20, a large diameter gear 22, a mesh clutch 24, a small diameter gear 26, a differential gear 28, and a pair of left and right drive shafts 30 are connected in this order from the engine 12 side in the power transmission path PT between the engine 12 and the drive wheels 14. The vehicle 10 is equipped with an engine control device 50 including an ignition device, an inverter 52, a catalyst 54 provided in the exhaust pipe 12b of the engine 12, an electronic control device 70, and the like.

The engine 12 is a known internal combustion engine. The engine control device 50 is controlled by the electronic control device 70, thereby controlling the engine torque Te of the engine 12.

The first motor MG1 and the second motor MG2 are rotating electric machines that have a function as a motor and a function as a generator, and are so-called motor generators. The first motor MG1 and the second motor MG2 are each connected to a battery (not shown) via an inverter 52. The inverter 52 is controlled by the electronic control device 70, and the MG1 torque Tmg1, which is the torque [Nm] of the first motor MG1, and the MG2 torque Tmg2, which is the torque of the second motor MG2, are controlled, respectively.

The damper 16 is a device that absorbs torque fluctuations of the engine 12. The damper 16 includes a first rotating element 16a connected to the crankshaft 12a of the engine 12 and a second rotating element 16b connected to the differential mechanism 18 via the input shaft 32. That is, the damper 16 is provided between the engine 12 and the first electric motor MG1 in the power transmission path PT. For example, multiple types of springs 16c and friction mechanisms 16d are interposed between the first rotating element 16a and the second rotating element 16b. The stiffness value (spring constant) corresponding to the change in the input torque Tin, which is the torque input to the damper 16 with respect to the change in the torsion angle φ [rad] of the damper 16, is changed in stages, and a predetermined hysteresis (also called a history phenomenon) is given to the input torque Tin when the torsion angle φ increases and decreases.

The differential mechanism 18 is, for example, a single-pinion type planetary gear device, and the first electric motor MG1, the input shaft 32, and the output gear 20 are connected to the sun gear S, the carrier CA, and the ring gear R, respectively. The first electric motor MG1 is connected to the differential mechanism 18 so as to be capable of transmitting power, and is an electric motor connected to the power transmission path PT so as to be capable of transmitting power.

The large diameter gear 22 is meshed with the output gear 20, which is the output rotating member of the differential mechanism 18, and the second output gear 34, which is the output rotating member of the second electric motor MG2. A meshing clutch 24 capable of connecting and disconnecting the power transmission between the large diameter gear 22 and the small diameter gear 26 is provided between them. The small diameter gear 26 is meshed with the diff ring gear 28a of the differential gear 28.

The vehicle 10 is equipped with a parking gear 36. The parking gear 36 is connected to the drive wheels 14 via the small diameter gears 26 and the like, and rotates together with the drive wheels 14. The parking gear 36 is fixed (locked) so that it cannot rotate by a known parking lock mechanism (not shown).

The vehicle 10 is equipped with a mesh brake 38. The crankshaft 12a is connected to a housing 40, which is a non-rotating member, via the mesh brake 38. The crankshaft 12a is locked so that it cannot rotate when the mesh brake 38 is engaged.

The vehicle 10 can selectively switch between the "P range (= parking range)," "R range (= reverse driving range)," "N range (= neutral range)," and "D range (= forward driving range)" by operating a shift operating device (not shown), for example.

The electronic control unit 70 is a controller that includes a control device that controls each part in the vehicle 10, and is configured to include, for example, a so-called microcomputer in which the CPU uses the temporary storage function of the RAM and performs signal processing according to a program previously stored in the ROM.

The electronic control device 70 receives various signals (e.g., vehicle speed V [km/h], torsion angle φ representing the rotational position of the input shaft 32, engine speed Ne [rpm] which is the rotational speed of the engine 12, catalyst temperature THc which is the temperature of the catalyst 54, etc.) based on detection values by various sensors (e.g., vehicle speed sensor 60, input shaft rotation sensor 62, engine speed sensor 64, catalyst temperature sensor 66, etc.) provided in the vehicle 10. The electronic control device 70 outputs various command signals (e.g., engine control signal Se for controlling the engine 12, motor control signal Smg for controlling each of the first electric motor MG1 and the second electric motor MG2, etc.) to each device (e.g., engine control device 50, inverter 52, etc.) provided in the vehicle 10.

The electronic control unit 70 functionally comprises a characteristics measurement unit 72 and a warm-up control unit 74.

The characteristic measurement unit 72 determines whether the vehicle is in a state in which the damper characteristics, which are the characteristics of the damper 16, can be measured. A vehicle state in which the damper characteristics can be measured is, for example, a state in which the vehicle speed V is zero, the shift range is in P range, the engine 12 is stopped, and operation of the engine 12 is not required. The measurement timing can be in various modes, such as during vehicle inspection, after a specified driving distance, or after each driving time.

When the characteristic measurement unit 72 determines that the vehicle is in a state in which the damper characteristics can be measured, it measures the damper characteristics. For example, the characteristic measurement unit 72 engages the mesh brake 38 to lock the crankshaft 12a so that it cannot rotate, engages the mesh clutch 24, and controls the first electric motor MG1 to apply torque to the damper 16 and measure the torsion angle φ using an input shaft rotation sensor 62 such as a resolver. The MG1 torque Tmg1 applied to the damper 16 when measuring the torsion angle φ corresponds to the input torque Tin. Since the differential mechanism 18 is provided between the first electric motor MG1 and the damper 16, the MG1 torque Tmg1 and the input torque Tin, which is the torque on the input shaft 32, differ in magnitude by the gear ratio of the differential mechanism 18, but for convenience, they are treated as being the same.

The characteristic measurement unit 72 obtains the relationship between the torsion angle φ and the input torque Tin as the damper characteristic, and obtains the hysteresis torque Thys [Nm] based on that relationship. The hysteresis torque Thys is the difference between the input torque Tin when the torsion angle φ increases and when it decreases (see "Measurement Results" in FIG. 3 described later). In this way, the characteristic measurement unit 72 obtains the hysteresis torque Thys by applying torque to the damper 16 by the first electric motor MG1 and measuring the torsion angle φ of the damper 16 while the engine 12 is stopped.

The warm-up control unit 74 controls the engine 12 to warm up the catalyst 54. For example, when the catalyst temperature THc is less than a predetermined temperature THcf, the warm-up control unit 74 controls the engine 12 to retard the ignition timing by a predetermined retard amount θf. The predetermined temperature THcf is a predetermined threshold value at which the catalyst 54 needs to be warmed up.

The ignition retard amount θ, which is the amount of retardation of the ignition timing when the catalyst 54 is warmed up, is the amount [deg] by which the ignition timing is retarded from the ignition timing during normal operation when the catalyst 54 is not warmed up, that is, during normal operation when the catalyst 54 has been warmed up. The greater the ignition retard amount θ, the more the warming up of the catalyst 54 is promoted, but the more unstable the combustion in the engine 12 becomes, and the more likely it is that the NV forcing force by the engine 12 will be increased.

In the power transmission path PT between the engine 12 and the drive wheels 14 and the power transmission path between the second electric motor MG2 and the drive wheels 14, there is backlash, or rattle, at the meshing portion between the gears that mesh with each other. The NV is a rattle sound (= rattle sound) that occurs when the explosive fluctuations of the engine torque Te are transmitted to the meshing portion where the force of the tooth surfaces pressing against each other is weakened, for example, when the MG2 torque Tmg2 is zero or close to zero, and the tooth surfaces repeatedly collide and separate from each other and strike each other. Alternatively, the NV is a rattle sound that occurs when the explosive fluctuations of the engine 12, which are stronger than the force of the tooth surfaces pressing against each other, are transmitted to the meshing portion between the gears in the power transmission path PT, and the fluctuations are amplified by the drive torsional system resonance, which uses the explosive fluctuations as a forcing force. Alternatively, the NV is, for example, a muffled sound generated inside the vehicle when the explosion fluctuations of the engine 12 act as a forcing force and the vibrations are amplified by the resonance of the power transmission path PT that occurs at a specific engine rotation speed Ne. The amplified explosion fluctuations are then transmitted to the suspension via the drive shaft 30, etc., causing the vehicle body to vibrate.

The predetermined retardation amount θf when the catalyst 54 is warmed up is determined in advance, for example, taking into consideration the NV forcing force of the engine 12, which allows NV. In other words, the magnitude of the predetermined retardation amount θf is limited so that NV is tolerable. On the other hand, the damper 16 has the function of attenuating the forcing force of the engine 12 transmitted to the power transmission path PT. Therefore, the predetermined retardation amount θf, which is set uniformly to the retardation amount limit value θlim, which limits the ignition retardation amount θ, taking into consideration only the NV forcing force of the engine 12, is not necessarily an optimal value.

The absolute value of the NV forcing force (torque equivalent) by the engine 12 is much greater than the hysteresis torque Thys generated by frictional force. The greater the hysteresis torque Thys, the easier it is for the NV forcing force to be attenuated, so the NV forcing force transmitted to the power transmission path PT is reduced, making it easier to suppress NV.

For example, as shown in FIG. 2A, the larger the ignition retard amount θ, the greater the forcing force of the rattle noise transmitted to the power transmission path PT, while the larger the hysteresis torque Thys, the smaller the forcing force of the rattle noise transmitted to the power transmission path PT, and the rattle noise is reduced. Therefore, the ignition retard amount θ at which the rattle noise is equal to or smaller than the permissible forcing force is increased as the hysteresis torque Thys is increased. In other words, the maximum ignition retard amount θmax that can be set for each hysteresis torque Thys is increased as the hysteresis torque Thys is increased (see θ1, θ2, θ3 in the figure). Increasing the maximum ignition retard amount θmax corresponds to increasing the relaxation of the retard amount limit value θlim. Therefore, as shown in FIG. 2B, the relationship between the hysteresis torque Thys and the relaxation of the retard amount limit value θlim is determined in advance. In FIG. 2B, the amount of relaxation of the retard amount limit value θlim is set to a larger value as the hysteresis torque Thys is larger. The amount of relaxation of the retard amount limit value θlim corresponds to, for example, the looseness of the retard amount limit, and also corresponds to the magnitude of the ignition retard amount θ. The amount of relaxation of the retard amount limit value θlim also corresponds to the engine control correction amount Δθ for correcting the predetermined retard amount θf to be larger than the retard amount limit value θlim. In other words, the engine control correction amount Δθ is set to a larger value as the hysteresis torque Thys is larger (see the "control correction amount map" in FIG. 3 described later).

As a result, if the hysteresis torque Thys is large, the retardation amount limit value θlim is relaxed, making it possible to relax NV countermeasures and promote warming up of the catalyst 54. In this way, when the hysteresis torque Thys is large, the warm-up control unit 74 sets the ignition retardation amount θ of the engine 12 during warm-up of the catalyst 54 to a larger value compared to when the hysteresis torque Thys is small.

Figure 3 is a flowchart that explains the main control operations of the electronic control unit 70, and is a flowchart that explains the control operations for achieving both the promotion of warm-up of the catalyst 54 and the suppression of NV, and is executed, for example, repeatedly.

3, first, in step S10 (hereinafter, steps are omitted) corresponding to the function of the characteristic measurement unit 72, it is determined whether the vehicle speed V is zero. If the determination in S10 is positive, in S20 corresponding to the function of the characteristic measurement unit 72, it is determined whether the shift range is P range. The P range is a shift range in which the parking gear 36 is locked by a parking lock mechanism (not shown). If the determination in S20 is positive, in S30 corresponding to the function of the characteristic measurement unit 72, it is determined whether the engine 12 is stopped, that is, whether the engine rotation speed Ne is zero. If the determination in S30 is positive, in S40 corresponding to the function of the characteristic measurement unit 72, it is determined whether the engine 12 needs to be operated. The state in which the engine 12 needs to be operated is, for example, a state in which the catalyst 54 needs to be warmed up, a state in which a battery (not shown) needs to be charged, etc. If the determination in S40 is negative, in S50 corresponding to the function of the characteristic measurement unit 72, measurement of the damper characteristics is performed (started). On the other hand, if the determination in any of S10, S20, and S30 is negative, or if the determination in S40 is positive, the process returns to S10. Following S50, in S60 corresponding to the function of the characteristic measurement unit 72, it is determined whether the shift range is other than the P range, the vehicle speed V is other than zero, or the engine 12 needs to be operated. If the determination in S60 is positive, the measurement of the damper characteristics is interrupted in S70 corresponding to the function of the characteristic measurement unit 72. If the determination in S60 is negative, it is determined in S80 corresponding to the function of the characteristic measurement unit 72 whether the measurement of the damper characteristics has been completed. Following S70, or if the determination in S80 is negative, the process returns to S10. If the determination in S80 above is positive, in S90, which corresponds to the functions of the characteristic measurement unit 72 and the warm-up control unit 74, the hysteresis torque Thys is obtained based on the measurement results of the damper characteristics (see "Measurement Results" in the figure). In addition, using a predetermined relationship between the hysteresis torque Thys and the engine control correction amount Δθ (see "Control Correction Amount Map" in the figure), the engine control correction amount Δθ corresponding to the hysteresis torque Thys is calculated (selected), and the program in the control of the engine 12 regarding the warm-up of the catalyst 54 is rewritten. For example, the predetermined retardation amount θf is rewritten.

As described above, according to this embodiment, when the hysteresis torque Thys is large, the ignition retard amount θ is set larger when the catalyst 54 is warmed up than when the hysteresis torque Thys is small, so the catalyst 54 is more likely to be warmed up the larger the hysteresis torque Thys is. When the ignition retard amount θ is set large and the NV forcing force by the engine 12 is increased, the forcing force transmitted to the power transmission path PT is more likely to be attenuated by the large hysteresis torque Thys, so NV is more likely to be suppressed. Therefore, it is possible to achieve both promotion of warming up the catalyst 54 and suppression of NV. It is also possible to accommodate individual differences and aging of the damper 16.

Although an embodiment of the present invention has been described above, the present invention can also be applied in other aspects. For example, the present invention can be applied to a hybrid vehicle equipped with a damper provided between the engine and the electric motor. Note that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10: Vehicle (hybrid vehicle) 12: Engine 12b: Exhaust pipe 14: Drive wheels 16: Damper 54: Catalyst 70: Electronic control device (control device) MG1: First electric motor (electric motor) PT: Power transmission path

Claims (1)

A control device for a hybrid vehicle including an engine, an electric motor connected to a power transmission path between the engine and a drive wheel so as to be capable of transmitting power, and a damper provided between the engine and the electric motor in the power transmission path,
a hysteresis torque that is a difference between a torque input to the damper when the torsion angle is increasing and a torque input to the damper when the torsion angle is decreasing, by applying a torque to the damper by the electric motor while the engine is stopped;
A control device for a hybrid vehicle, characterized in that when the hysteresis torque is large, the amount of retard of the ignition timing of the engine during warm-up of a catalyst provided in an exhaust pipe of the engine is set to be larger than when the hysteresis torque is small.

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