JP7791644B2 - Motor assist control device for hybrid vehicles - Google Patents

Description

The present invention relates to a motor assist control device for a hybrid vehicle.

Patent Document 1 describes a method for minimizing the deceleration of the vehicle felt by vehicle occupants during the gear shift phase and, at the same time, reducing the energy consumption of the electric motor. If, immediately before the start of the gear shift phase, the value of the maximum torque that can be transmitted by the electric motor is lower than the initial torque value transmitted by the heat engine to the wheels, the friction clutch is gradually disengaged during the period until the torque transmitted by the heat engine to the wheels reaches a reduced torque value equivalent to the maximum torque that can be transmitted by the electric motor, and the friction clutch is gradually engaged during the period until the torque transmitted by the heat engine to the wheels reaches the initial torque value from the reduced torque value, so that the electric motor does not transmit torque during each period.

JP 2019-55771 A

However, when comparing the first torque control (assist control shown in Figure 2 of Patent Document 1, which does not take into account minimizing assist energy) in which the value of the maximum torque that can be transmitted by the electric motor is at least equal to the initial torque value transmitted to the wheels by the heat engine, with the second torque control (assist control shown in Figure 3 of Patent Document 1, which minimizes the assist energy of the electric motor) in which the value of the maximum torque that can be transmitted by the electric motor is lower than the initial torque value transmitted to the wheels by the heat engine, the second torque control results in a longer gear shift period. This can result in a longer time until the torque transmitted to the wheels before the gear shift began is restored, leaving room for improvement in preventing vehicle occupants from feeling a loss of torque.

The present invention therefore aims to provide a motor assist control device for a hybrid vehicle that can prevent the driver from feeling torque loss during gear changes.

In order to solve the above problems, the present invention provides a motor assist control device for a hybrid vehicle comprising an engine, a motor, an automatic transmission that changes the speed of the engine and transmits it to a drive shaft, a clutch that connects or disconnects power transmission between the engine and the drive shaft, and causes the motor to output assist torque during a period when the clutch is not fully engaged when the automatic transmission is shifting gears.The motor assist control device is equipped with a control unit that, when the sum of the clutch torque and the assist torque output from the automatic transmission becomes smaller than a driver requested torque during the clutch disengagement process when the automatic transmission is shifting gears, maintains the maximum torque of the motor output during the clutch disengagement process when the automatic transmission is shifting gears, even during the clutch engagement process, while the sum of the clutch torque and the assist torque output from the automatic transmission is smaller than the driver requested torque, and when the sum of the clutch torque and the assist torque output from the automatic transmission becomes equal to or greater than the driver requested torque, ends the maintenance of the maximum torque of the motor and increases the engagement speed of the clutch to increase the clutch torque .

In this way, the present invention can prevent the driver from feeling a loss of torque during gear changes.

FIG. 1 is a schematic diagram of a hybrid vehicle according to an embodiment of the present invention. FIG. 2 is a flowchart showing the procedure of the motor assist control process of the motor assist control device according to one embodiment of the present invention. FIG. 3 is a time chart showing changes in torque when the clutch is engaged at a constant speed during the clutch engagement process according to the motor assist control process of the motor assist control device according to one embodiment of the present invention. FIG. 4 is a time chart showing torque changes when the clutch engagement speed is increased midway through the clutch engagement process according to the motor assist control processing of the motor assist control device according to one embodiment of the present invention.

A motor assist control device for a hybrid vehicle according to one embodiment of the present invention comprises an engine, a motor, an automatic transmission that changes the speed of the engine and transmits it to the drive shaft, a clutch that connects or disconnects the power transmission between the engine and the drive shaft, and a control unit that causes the motor to output assist torque during periods when the clutch is not fully engaged when the automatic transmission is shifting gears, and that maintains the maximum torque of the motor output during the clutch disengagement process during the clutch engagement process.

As a result, the motor assist control device for a hybrid vehicle according to one embodiment of the present invention can prevent the driver from feeling a loss of torque during gear changes.

The following describes in detail a hybrid vehicle equipped with a motor assist control device according to an embodiment of the present invention, with reference to the drawings.

In FIG. 1, a hybrid vehicle 1 according to one embodiment of the present invention includes an engine 2 as an internal combustion engine, a transmission 3 as an automatic transmission, a motor 4, an inverter 5, a high-voltage battery 6, a low-voltage battery 7, and a control unit 8.

Engine 2 has multiple cylinders. In this embodiment, engine 2 is configured so that each cylinder undergoes a series of four strokes: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

A starting device 21 is connected to the engine 2. The starting device 21 is connected to the crankshaft of the engine 2 via a belt (not shown). When power is supplied to the starting device 21, it rotates, causing the crankshaft to rotate and providing the rotational force to the engine 2 when it is started.

The starting device 21 is composed of a starter and an ISG (Integrated Starter Generator). The starting device 21 may also be equipped with both a starter and an ISG.

The transmission 3 changes the speed of the rotation output from the engine 2 and drives the drive wheels 10 via the drive shaft 11. The transmission 3 includes a constant-mesh transmission mechanism (not shown) consisting of a parallel shaft gear mechanism, and an actuator (not shown).

A dry single-plate clutch 31 is provided between the engine 2 and the transmission 3, and the clutch 31 connects and disconnects the power transmission between the engine 2 and the transmission 3.

The transmission 3 is configured as a so-called AMT (Automated Manual Transmission), and an actuator (not shown) switches the gears in the transmission mechanism and engages and disengages the clutch 31.

A differential mechanism 32 is provided between the transmission 3 and the drive wheels 10. The differential mechanism 32 and the drive wheels 10 are connected by a drive shaft 11.

The motor 4 is connected to the differential mechanism 32 via a reduction gear (not shown), such as a chain. The motor 4 functions as an electric motor. The motor 4 also functions as a generator, generating electricity as the hybrid vehicle 1 moves.

The motor 4 is provided with a temperature sensor 41 that detects the temperature of the motor 4. The temperature sensor 41 is connected to the control unit 8.

Under the control of the control unit 8, the inverter 5 converts DC power supplied from a high-voltage battery 6 or the like into three-phase AC power and supplies it to the motor 4.

Under the control of the control unit 8, the inverter 5 converts the three-phase AC power generated by the motor 4 into DC power. This DC power is used to charge, for example, the high-voltage battery 6.

The high-voltage battery 6 is composed of, for example, a lithium-ion battery. The high-voltage battery 6 supplies power to the inverter 5.

The high-voltage battery 6 is equipped with a battery status sensor 61. The battery status sensor 61 detects the charge/discharge current, voltage, and battery temperature of the high-voltage battery 6. The battery status sensor 61 is connected to the control unit 8. The control unit 8 is able to detect the charge level of the high-voltage battery 6 based on the output of the battery status sensor 61.

The low-voltage battery 7 is composed of, for example, a lead battery. The low-voltage battery 7 supplies power to the electrical loads of the hybrid vehicle 1, such as the starting device 21.

In this way, the hybrid vehicle 1 forms a parallel hybrid system that can use the power of both the engine 2 and the motor 4 to drive the vehicle, and is designed to run using the power output by at least one of the engine 2 and the motor 4.

The control unit 8 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

The ROM of this computer unit stores various constants, maps, etc., as well as a program that causes the computer unit to function as the control unit 8.

In other words, the CPU uses RAM as a working area and executes programs stored in ROM, causing these computer units to function as the control unit 8 in this embodiment.

In addition to the temperature sensor 41 and battery status sensor 61 mentioned above, various sensors including an accelerator opening sensor 81 and a clutch stroke sensor 82 are connected to the input port of the control unit 8.

The accelerator opening sensor 81 detects the amount of operation of the accelerator pedal (not shown) as the accelerator opening. The clutch stroke sensor 82 detects the degree of engagement of the clutch 31.

On the other hand, the output port of the control unit 8 is connected to various control targets, including the above-mentioned starting device 21, the actuator of the transmission 3, the inverter 5, and an injector (not shown).

In this embodiment, the control unit 8 calculates the driver-requested torque based on the accelerator pedal position and other factors. The control unit 8 controls the engine 2, transmission 3, clutch 31, and motor 4 so that the driver-requested torque is output to the drive wheels 10.

The control unit 8 also executes assist torque output control, which outputs assist torque from the motor 4 to the drive wheels 10 while the clutch 31 is disengaged during gear changes. "While the clutch 31 is disengaged" refers to the period during which the clutch 31 is fully disengaged (hereinafter, this period will be referred to as the "non-engagement period"), and this non-engagement period includes a so-called partial clutch state. The partial clutch state refers to a state in which the friction materials of the clutch 31 are engaged in a slipping state, transmitting power.

In vehicles that have a clutch in the power transmission path between the transmission and engine, torque from the engine is not transmitted to the drive wheels during periods when the clutch is not fully engaged during gear changes, resulting in a loss of acceleration/deceleration feeling, known as torque loss, and this torque loss creates a feeling of freewheeling.

Assist torque output control outputs assist torque from the motor 4 to the drive wheels 10 during periods when the clutch is not fully engaged during gear changes, thereby preventing the feeling of freewheeling due to torque loss.

The control unit 8 maintains the maximum torque of the motor 4 output during the clutch disengagement process during gear shifting, even during the clutch engagement process after the gear shift mechanism of the transmission 3 is switched.

The clutch disengagement process refers to the period from when the clutch 31 begins to be fully disengaged until the clutch 31 is completely disengaged.

The clutch engagement process refers to the period from when the clutch 31 begins to engage after the gear shift mechanism of the transmission 3 is switched to a different gear position until the clutch 31 is fully engaged.

During the clutch engagement process, the control unit 8 maintains the maximum torque of the motor 4 output during the clutch release process while the sum of the clutch torque and the motor torque is less than the first torque.

Clutch torque is the torque of the output shaft of the transmission 3 and is the torque output to the differential mechanism 32.

When the sum of the clutch torque and the motor torque becomes equal to or greater than the first torque during the clutch engagement process, the control unit 8 sets the difference between the first torque and the clutch torque as the assist torque of the motor 4.

The first torque is set to the driver's requested torque or the drive torque before the start of the gear shift. The driver's requested torque is a torque that changes in response to the driver's request. When the driver's requested torque is set as the first torque, the torque is controlled in response to the driver's request, and the torque requested by the driver can be output when the gear shift process is completed. The drive torque before the start of the gear shift is the torque that was output to the drive shaft 11 immediately before the current gear shift started. When the drive torque before the start of the gear shift is set as the first torque, the torque is controlled based on the value of the drive torque before the start of the gear shift, and can be restored to the drive torque before the start of the gear shift when the gear shift process is completed. Furthermore, when the drive torque before the start of the gear shift is set as the first torque, control is based on a constant value, which reduces the load on the control process.

During the clutch engagement process, the control unit 8 engages the clutch 31 at a constant speed. During the clutch engagement process, the control unit 8 causes the motor 4 to output assist torque until the clutch 31 is fully engaged.

The control unit 8 may increase the engagement speed of the clutch 31 midway through the clutch engagement process. For example, when the sum of the clutch torque and the motor torque becomes equal to the first torque, the control unit 8 increases the engagement speed of the clutch 31 compared to before.

During the clutch release process, when the clutch torque decreases to the second torque, the control unit 8 increases the clutch release speed and causes the motor 4 to output assist torque.

The control unit 8 may set the release speed of the clutch 31 after the clutch torque has decreased to the second torque during the clutch release process to be the same as the engagement speed of the clutch 31 during the clutch engagement process.

During the clutch release process, the control unit 8 outputs the difference between the second torque and the clutch torque as the assist torque of the motor 4.

The second torque is, for example, the motor output torque, which is the maximum torque that can be output by the motor 4 at a given point in time.

The control unit 8 may, for example, calculate the motor's available output torque at a predetermined cycle, and when the motor's available output torque and the clutch torque become equal, increase the clutch release speed and cause the motor 4 to output assist torque. In this case, the motor's available output torque when the motor's available output torque and the clutch torque become equal is defined as the second torque.

In addition, the control unit 8 may set the motor output torque at a predetermined time between a predetermined time before the clutch release process begins and when the motor output torque becomes equal to the clutch torque as the second torque.

The control unit 8 calculates the motor's output torque based on the charge level of the high-voltage battery 6 or the heat generation state of the motor 4.

The motor assist control process performed by the motor assist control device of this embodiment configured as described above will be described with reference to Figure 2. The motor assist control process described below begins when the control unit 8 begins shift control, and is executed at preset time intervals.

In step S1, the control unit 8 determines whether the clutch is currently engaged. If it is determined that the clutch is currently engaged, the control unit 8 executes the process of step S6. If it is determined that the clutch is not currently engaged, the control unit 8 executes the process of step S2.

In step S2, the control unit 8 determines whether the clutch is currently being released. If it is determined that the clutch is currently being released, the control unit 8 executes the process of step S3. If it is determined that the clutch is not currently being released, the control unit 8 executes the process of step S9.

In step S3, the control unit 8 determines whether the clutch torque is greater than the motor's available output torque. If it is determined that the clutch torque is greater than the motor's available output torque, the control unit 8 executes the process of step S4. If it is determined that the clutch torque is not greater than the motor's available output torque, the control unit 8 executes the process of step S5.

In step S4, the control unit 8 does not perform motor assist. After executing the processing of step S4, the control unit 8 ends the motor assist control processing.

In step S5, the control unit 8 sets the difference between the motor output torque and the clutch torque as the target motor torque and causes the motor 4 to output an assist torque. After executing the processing of step S5, the control unit 8 ends the motor assist control processing.

In step S6, the control unit 8 determines whether the sum of the clutch torque and the motor's available output torque is greater than the driver's required torque. If it is determined that the sum of the clutch torque and the motor's available output torque is greater than the driver's required torque, the control unit 8 executes the process of step S7. If it is determined that the sum of the clutch torque and the motor's available output torque is not greater than the driver's required torque, the control unit 8 executes the process of step S8.

In step S7, the control unit 8 sets the difference between the driver requested torque and the clutch torque as the target motor torque and causes the motor 4 to output an assist torque. After executing the processing of step S7, the control unit 8 ends the motor assist control processing.

In step S8, the control unit 8 sets the motor output torque as the target motor torque and causes the motor 4 to output an assist torque. After executing the processing of step S8, the control unit 8 ends the motor assist control processing.

In step S9, the control unit 8 sets the motor output torque as the target motor torque and causes the motor 4 to output an assist torque. After executing the processing of step S9, the control unit 8 ends the motor assist control processing.

The operation of this motor assist control process will be explained with reference to Figures 3 and 4. Note that the example in Figure 3 shows a case where the clutch torque is controlled so that it becomes the driver requested torque when the clutch 31 is fully engaged, and the clutch 31 is engaged at a constant speed during the clutch engagement process.

When the gear shift process begins and the clutch 31 begins to fully disengage, the clutch torque decreases, and the torque transmitted to the drive shaft 11 also decreases. At this time, the clutch torque is greater than the motor's outputtable torque, so no assist torque is output by the motor 4.

At time t1, when the clutch torque becomes equal to the motor's available output torque, the motor 4 begins to output assist torque, and the difference between the motor's available output torque and the clutch torque is set as the target motor torque, and the motor 4 outputs assist torque. At this time, the release speed of the clutch 31 is set faster than before time t1, when motor assistance was not being performed.

At time t2, when the clutch 31 is completely released, the gear shifting mechanism of the transmission 3 begins to change gears, during which time the motor 4 provides motor assistance at its maximum output torque.

At time t3, when the gear shifting of the transmission 3's speed change mechanism is completed, the clutch 31 begins to engage, and motor assistance is provided by the motor 4 at the motor's available output torque while the sum of the motor's available output torque and the clutch torque is less than the driver's requested torque.

At time t4, when the sum of the motor output torque and the clutch torque becomes equal to the driver requested torque, the assist torque from motor 4 is reduced so that the sum of the motor output torque and the clutch torque becomes equal to the driver requested torque, and when clutch 31 is fully engaged, motor assist ends.

The example in Figure 4 shows a case where, when the clutch 31 is fully engaged, the clutch torque is controlled to be equal to the driver's requested torque, and during the clutch engagement process, when the sum of the clutch torque and motor torque becomes equal to the driver's requested torque, the engagement speed of the clutch 31 is increased compared to before.

When the gear shift process begins and the clutch 31 begins to fully disengage, the clutch torque decreases, and the torque transmitted to the drive shaft 11 also decreases. At this time, the clutch torque is greater than the motor's outputtable torque, so no assist torque is output by the motor 4.

At time t11, when the clutch torque becomes equal to the motor's available output torque, the motor 4 begins to output assist torque, and the difference between the motor's available output torque and the clutch torque is set as the target motor torque, and the motor 4 outputs assist torque. At this time, the release speed of the clutch 31 is set faster than before time t11, when motor assistance was not being performed.

At time t12, when the clutch 31 is completely released, the gear shifting mechanism of the transmission 3 begins to change gears, during which time motor assistance is provided by the motor 4 at the available motor output torque.

At time t13, when the gear shifting of the transmission 3's speed change mechanism is completed, the clutch 31 begins to engage, and motor assistance is provided by the motor 4 at the motor's available output torque while the sum of the motor's available output torque and the clutch torque is less than the driver's requested torque.

At time t14, when the sum of the motor's available output torque and the clutch torque becomes equal to the driver's required torque, the engagement speed of the clutch 31 is increased, and the assist torque provided by the motor 4 is reduced so that the sum of the motor's available output torque and the clutch torque becomes equal to the driver's required torque. When the clutch 31 is fully engaged, motor assist ends.

In this way, in this embodiment, the control unit 8 maintains the maximum torque of the motor 4 output during the clutch disengagement process while the transmission 3 is shifting gears, even during the clutch engagement process.

As a result, during the clutch engagement process, the maximum torque of the motor 4 that was output during the clutch release process is output. Therefore, during the clutch engagement process, when engine torque gradually increases, the torque transmitted to the drive shaft 11 can be quickly increased, shortening the torque loss period.

In addition, during the clutch engagement process, the control unit 8 maintains the maximum torque of the motor 4 output during the clutch release process while the sum of the clutch torque and the motor torque is less than the driver requested torque.

As a result, during the clutch engagement process, the maximum torque of the motor 4 output during the clutch release process is output while the sum of the clutch torque and motor torque is smaller than the driver's requested torque. Therefore, during the clutch engagement process, the torque transmitted to the drive shaft 11 can be quickly increased to the driver's requested torque, shortening the torque loss period.

In addition, if the sum of the clutch torque and motor torque becomes equal to or greater than the driver requested torque during the clutch engagement process, the control unit 8 sets the difference between the driver requested torque and the clutch torque as the assist torque of the motor 4.

As a result, during the clutch engagement process, if the sum of the clutch torque and motor torque exceeds the driver requested torque, the difference between the driver requested torque and the clutch torque is used as the assist torque of the motor 4. Therefore, during the clutch engagement process, the torque transmitted to the drive shaft 11, which has increased to the driver requested torque, can be maintained while the clutch 31 is fully engaged.

Furthermore, during the clutch engagement process, the control unit 8 may maintain the maximum torque of the motor 4 output during the clutch release process while the sum of the clutch torque and the motor torque is smaller than the drive torque before the start of the gear shift.

As a result, during the clutch engagement process, the maximum torque of the motor 4 output during the clutch release process is output while the sum of the clutch torque and motor torque is smaller than the drive torque before the shift started.As a result, during the clutch engagement process, the torque transmitted to the drive shaft 11 can be quickly increased to the drive torque before the shift started, shortening the torque drop period.

Furthermore, if, during the clutch engagement process, the sum of the clutch torque and the motor torque becomes equal to or greater than the drive torque before the start of the gear shift, the control unit 8 may set the difference between the drive torque before the start of the gear shift and the clutch torque as the assist torque of the motor 4.

As a result, during the clutch engagement process, if the sum of the clutch torque and motor torque becomes equal to or greater than the drive torque before the shift started, the difference between the drive torque before the shift started and the clutch torque is used as the assist torque of the motor 4. Therefore, during the clutch engagement process, the torque transmitted to the drive shaft 11, which has increased to the drive torque before the shift started, can be maintained while the clutch 31 is fully engaged.

In addition, the control unit 8 engages the clutch 31 at a constant clutch engagement speed during the clutch engagement process.

As a result, the clutch 31 is engaged at a constant clutch engagement speed during the clutch engagement process. This allows the clutch 31 to be engaged quickly during the clutch engagement process, shortening the motor assist time and reducing the power used during gear changes.

Furthermore, when the sum of the clutch torque and the motor torque becomes equal to the first torque during the clutch engagement process, the control unit 8 increases the engagement speed of the clutch 31 compared to the speed from the start of engagement of the clutch 31 until the sum of the clutch torque and the motor torque becomes equal to the first torque.

As a result, during the clutch engagement process, when the sum of the clutch torque and motor torque becomes equal to the first torque, the clutch engagement speed is increased. Therefore, compared to when the clutch 31 is engaged at a constant speed, the period during which the motor torque and clutch torque are interchanged by reducing the motor torque and increasing the clutch torque can be shortened, thereby shortening the time required to complete the gear shift. Furthermore, because the timing for increasing the engagement speed of the clutch 31 occurs after the torque output to the drive shaft 11 has returned to the first torque, there is no fluctuation in the torque output to the drive shaft 11 during the gear shift process, and vibration to the vehicle due to the gear shift can be suppressed.

In addition, when the clutch torque decreases to a predetermined amount during the clutch release process, the control unit 8 increases the clutch release speed and causes the motor 4 to output assist torque.

As a result, when the clutch torque decreases to a predetermined amount during the clutch release process, the clutch release speed is increased and assist torque is output from the motor 4. This shortens the motor assist time and reduces the power used during gear changes.

In addition, the control unit 8 makes the release speed of the clutch 31 after the clutch torque has decreased to a predetermined amount during the clutch release process the same as the engagement speed of the clutch 31 during the clutch engagement process.

This ensures that the release speed of the clutch 31 after the clutch torque has decreased to a predetermined amount during the clutch release process is the same as the engagement speed of the clutch 31 during the clutch engagement process. This shortens the motor assist time and reduces the power used during gear changes.

While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications may be made without departing from the scope of the present invention. All such modifications and equivalents are intended to be encompassed by the following claims.

1 Hybrid vehicle 2 Engine 3 Transmission (automatic transmission)
4 Motor 6 High voltage battery (battery)
8 Control unit 11 Drive shaft 31 Clutch 41 Temperature sensor 61 Battery state sensor 81 Accelerator opening sensor 82 Clutch stroke sensor

Claims (6)

A motor assist control device for a hybrid vehicle includes an engine, a motor, an automatic transmission that changes the speed of rotation of the engine and transmits it to a drive shaft, a clutch that connects or disconnects power transmission between the engine and the drive shaft, and causes the motor to output assist torque during a period when the clutch is not fully engaged when the automatic transmission is shifting gears,
A motor assist control device for a hybrid vehicle comprising a control unit that, when the sum of the clutch torque output from the automatic transmission and the assist torque becomes smaller than the driver requested torque during the clutch disengagement process of the automatic transmission, maintains the maximum torque of the motor output during the clutch engagement process as long as the sum of the clutch torque output from the automatic transmission and the assist torque is smaller than the driver requested torque during the clutch engagement process, and when the sum of the clutch torque output from the automatic transmission and the assist torque becomes equal to or greater than the driver requested torque, ends the maintenance of the maximum torque of the motor and increases the engagement speed of the clutch to increase the clutch torque. 2. The motor assist control device for a hybrid vehicle according to claim 1, wherein, when the sum of the clutch torque and the assist torque becomes equal to or greater than the driver request torque during the clutch engagement process, the control unit sets the difference between the driver request torque and the clutch torque as the assist torque. 3. The motor assist control device for a hybrid vehicle according to claim 1, wherein, during the clutch release process, when the clutch torque output from the automatic transmission decreases to a first torque, the control unit increases the clutch release speed to cause the motor to output the assist torque. 4. The motor assist control device for a hybrid vehicle according to claim 3 , wherein the control unit outputs a difference between the first torque and the clutch torque as the assist torque during the clutch disengagement process. 5. The motor assist control device for a hybrid vehicle according to claim 3 , wherein the control unit sets the first torque to a maximum torque that can be output by the motor at a predetermined time. 6. The motor assist control device for a hybrid vehicle according to claim 5 , wherein the control unit calculates the motor outputtable torque based on the charge amount of a battery that supplies power to the motor or the heat generation state of the motor when the automatic transmission starts shifting.