JP2012116272A - Regenerative control device for hybrid electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regenerative control device for a hybrid electric vehicle, which is capable of eliminating a difference in a deceleration feeling caused by disparity between an engine deceleration mode and a motor deceleration mode during coasting drive, and of further achieving a maximal power generation amount by regenerative control of an electric motor in the motor deceleration mode.SOLUTION: During coasting drive of the vehicle in the motor deceleration mode, a clutch between an engine and the electric motor is disconnected, and regenerative torque of the electric motor is controlled on a maximum torque line to thereby use all deceleration energy of the vehicle for regenerative power generation, and a shift-down is performed in a rotation range of the electric motor where regenerative torque can be obtained, near engine braking on the maximum torque line, so that a deceleration feeling similar to the engine deceleration mode is achieved.

Description

  The present invention relates to a regeneration control device for a hybrid electric vehicle, and more specifically, a hybrid electric vehicle that efficiently performs regenerative power generation with a feeling of deceleration similar to deceleration due to engine running when the vehicle is decelerated due to accelerator off (hereinafter referred to as coasting operation). The present invention relates to a regeneration control device.

  2. Description of the Related Art Conventionally, so-called parallel hybrid electric vehicles have been developed and put into practical use in which an engine and an electric motor are mounted on a vehicle and the driving force of the engine and the driving force of the electric motor can be transmitted to the driving wheels of the vehicle. As one of this type of parallel hybrid electric vehicle, there has been proposed one in which an electric motor is connected to drive wheels via a transmission and an engine is connected to the electric motor via a clutch. In the hybrid electric vehicle, when the clutch is disengaged, the driving force of the electric motor is transmitted to the driving wheel through the transmission to drive the vehicle, and when the clutch is connected, the driving force of the engine or the driving force of the engine and the electric motor is transmitted to the driving wheel. Then, the vehicle is driven by being transmitted to the drive wheels.

By the way, as one of the characteristics of a hybrid electric vehicle, regenerative control by an electric motor can be mentioned. Regenerative control is executed during coasting operation of the vehicle, generating negative torque (regenerative torque) in the generator and applying braking force to the drive wheels, while charging the battery with the electric power generated by the motor, thereby decelerating the vehicle. It is intended to save fuel consumption by making effective use of energy.
There are various methods for regenerative control during coasting operation of the vehicle. For example, the technique described in Patent Document 1 can be cited. In the hybrid electric vehicle of Patent Document 1, a braking force (engine brake) due to engine friction is applied to the drive wheels in addition to the braking force due to regenerative control of the motor during coasting operation. At this time, the transmission is controlled so that the amount of regenerative power generation is maximized within a range in which the sum of the regenerative braking force and the engine braking force does not exceed a predetermined value or the required braking force. This prevents a situation in which the braking force acting on the vehicle exceeds the torque required by the driver due to an increase in engine brake.

Japanese Patent No. 4029592

However, in the hybrid electric vehicle described in Patent Document 1, since the engine brake is applied to the drive wheels during coasting operation, the braking force by the regenerative control of the motor is reduced by an amount corresponding to the engine brake, resulting in the regenerative control. There is a problem that the amount of power generation is reduced. Therefore, it is also conceivable to disengage the transmission of the engine brake to the drive wheel side by disengaging the clutch between the engine and the electric motor, and to use all of the deceleration energy of the vehicle for the regenerative power generation of the electric motor (hereinafter, this time Is called the motor deceleration mode).
In regenerative control in the motor deceleration mode, the regenerative torque of the motor is controlled so that the maximum amount of power generation can be obtained.
That is, as shown in the output characteristics of the electric motor in FIG. 2, in both the power running control for controlling the motor torque to the positive side and the regenerative control for controlling to the negative side, the electric motor has an upper limit on the maximum torque line that is approximately inversely proportional to the rotational speed. The power running torque and the regenerative torque are generated as follows. On the low rotation side, the power running torque and the regenerative torque are limited with the torque suppression line set as a control measure for suppressing excessive torque as the upper limit. In both the power running control and the regeneration control, the maximum torque is achieved on the maximum torque line, and the maximum power generation amount is achieved on the maximum torque line during the regeneration control. For this reason, when performing regenerative control of the electric motor by coasting operation, consideration is given to increasing the power generation amount as much as possible by controlling the regenerative torque along the maximum torque line.

By the way, this type of hybrid electric vehicle does not execute the motor deceleration mode in all coasting operations, and may use only the engine brake generated by engine friction as the braking force (hereinafter referred to as the travel mode at this time). Is called engine deceleration mode). For example, when the remaining charge rate (hereinafter referred to as SOC) of the traveling battery reaches the upper limit of the control range and charging is not necessary, the engine deceleration mode is established by connecting the clutch between the motor and the engine without regenerative control of the motor. Switch to.
However, since the engine brake due to engine friction and the regenerative torque generated by the motor are completely different requirements determined according to the specifications of the engine and the motor, the engine deceleration mode and the motor deceleration mode are applied to the vehicle. In many cases, the applied braking force is separated. More specifically, since the electric motor in the motor deceleration mode is controlled with the regenerative torque on the maximum torque line, the regenerative torque at this time is generally an absolute value compared with the engine brake caused by engine friction. In many cases, the braking force is larger in the motor deceleration mode than in the engine deceleration mode. Therefore, the feeling of deceleration that the driver receives due to the difference in braking force between the modes is different, resulting in a problem that the driver feels uncomfortable.

As a countermeasure, in the motor deceleration mode, it may be possible to limit the regenerative torque of the electric motor more than the maximum torque line (make the absolute value smaller), but the power generation amount is reduced accordingly. For this reason, there is a trade-off between the difference in deceleration feeling according to mode switching and the amount of power generated by regenerative control of the motor, and it is difficult to satisfy both requirements. Was desired.
The present invention has been made to solve such problems, and its object is to reduce the speed caused by the difference in braking force between the engine deceleration mode and the motor deceleration mode during coasting operation of the vehicle. An object of the present invention is to provide a regenerative control device for a hybrid electric vehicle capable of realizing the maximum power generation amount by regenerative control of an electric motor in the motor deceleration mode after eliminating the difference in feeling.

  In order to achieve the above object, the invention of claim 1 is constituted by connecting an electric motor to a driving wheel of a vehicle via a transmission, and an engine connected to the electric motor via a clutch. During coasting operation where the vehicle decelerates, the clutch is connected and the engine brake by the engine is transmitted to the drive wheels via the transmission to decelerate the vehicle, or the regenerative torque by the motor is transmitted to the drive wheels via the transmission. In a hybrid electric vehicle that selectively executes any one of the motor deceleration modes for decelerating the vehicle, the coasting operation determination unit that determines coasting operation of the vehicle is determined as coasting operation by the coasting operation determination unit, and the motor deceleration When the mode is selected, the clutch between the motor and engine is disengaged and the motor's regenerative torque is maximized. Regenerative control means for controlling on the negative maximum torque line where the amount can be obtained, and the engine in the engine deceleration mode on the maximum torque line when shifting down the transmission with a decrease in vehicle speed during coasting operation in the motor deceleration mode And a shift control means for executing a shift down of the transmission in the rotation range of the electric motor in which the regenerative torque in the vicinity of the brake is obtained.

According to a second aspect of the present invention, in the first aspect, the regenerative control means controls the regenerative torque of the electric motor by controlling on the maximum torque line due to the separation between the current shift stage of the transmission and the next shift stage on the low-speed gear side. When this increases excessively compared to the engine brake, the regenerative torque is kept constant until the downshift to the next gear.
According to a third aspect of the present invention, in the first or second aspect, the vehicle weight detecting means for detecting the weight of the vehicle is provided. Correction is made to the low vehicle speed side, and downshifting is executed based on the corrected timing.
According to a fourth aspect of the present invention, in any one of the first to third aspects, the vehicle includes a road surface gradient detecting unit that detects a gradient of a road surface on which the vehicle is traveling, and the speed change control unit detects that the road surface gradient detected by the road surface gradient detecting unit is When the slope of the descending road is steep, the shift down timing is corrected to the low vehicle speed side, and the shift down is executed based on the corrected timing.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the vehicle speed detection means for detecting the vehicle speed is provided, and the shift control means sets the shift down timing as the vehicle speed detected by the vehicle speed detection means increases. The shift down is executed based on the corrected timing.
According to a sixth aspect of the present invention, in the first to fourth aspects, the vehicle includes a slip determination unit that determines the slip of the driving wheel of the vehicle. When the shift control unit determines that the slip is determined by the slip determination unit, Even if not reached, downshifting is performed.

  As described above, according to the regeneration control device for a hybrid electric vehicle according to the first aspect of the present invention, the clutch is disengaged during the coasting operation of the vehicle in the motor deceleration mode, and the motor is regeneratively controlled on the negative maximum torque line. Therefore, the maximum power generation amount can be obtained by using all of the deceleration energy of the vehicle for regenerative power generation of the electric motor. The maximum power generation amount can be achieved in any rotation range as long as it is on the maximum torque line, but in the present invention, the rotation range of the electric motor that can obtain the regenerative torque in the vicinity of the engine brake in the engine deceleration mode on the maximum torque line. To shift down. For this reason, the motor during coasting operation in the motor deceleration mode generates a regenerative torque in the vicinity of the engine brake in the engine deceleration mode at any gear to brake the vehicle and achieve the same deceleration feeling as in the engine deceleration mode. Can do.

According to the hybrid electric vehicle regenerative control device of the second aspect of the invention, in addition to the first aspect, when the regenerative torque of the motor excessively increases as the vehicle speed decreases due to the control on the maximum torque line, The regenerative torque is kept constant until shifting down to the gear position.
Therefore, when the regenerative torque increases excessively, the regenerative torque drop before and after the shift down increases and a large shift shock occurs, but such a situation can be prevented in advance.
According to the regeneration control device for a hybrid electric vehicle of the invention of claim 3, in addition to claim 1 or 2, the downshift timing is corrected to the lower vehicle speed side as the vehicle weight detected by the vehicle weight detection means is larger. I did it.
Since the regenerative torque increases to the negative side as the vehicle speed decreases due to the control on the maximum torque line, a greater braking force acts on the vehicle due to the increase of the regenerative torque as the shift down timing becomes lower. Here, the larger the vehicle weight, the more difficult the drive wheels slip, and a larger braking force is required for deceleration.However, since the braking force increases accordingly, the appropriate braking is always performed regardless of the vehicle weight. Power can be realized, and thus the vehicle can be surely decelerated while preventing slipping of the drive wheels due to excessive braking force.

According to the regeneration control device for a hybrid electric vehicle of the invention of claim 4, in addition to claims 1 to 3, when the road surface gradient detected by the road surface gradient detecting means is on the downboard road side, the downhill road gradient is steep. The shift down timing was corrected to the low vehicle speed side.
Since the regenerative torque increases to the negative side as the vehicle speed decreases due to the control on the maximum torque line, a greater braking force acts on the vehicle due to the increase of the regenerative torque as the shift down timing becomes lower. Here, as the slope of the descending road becomes steep, a larger braking force is required for deceleration, but since the braking force increases accordingly, an appropriate braking force can always be realized regardless of the road surface gradient, Thus, the vehicle can be surely decelerated while preventing slipping of the drive wheels due to excessive braking force.

According to the regeneration control device for a hybrid electric vehicle of the invention of claim 5, in addition to claims 1 to 4, the higher the vehicle speed detected by the vehicle speed detection means, the more the shift down timing is corrected to the lower vehicle speed side. did.
Since the regenerative torque increases to the negative side as the vehicle speed decreases due to the control on the maximum torque line, a greater braking force acts on the vehicle due to the increase of the regenerative torque as the shift down timing becomes lower. Here, the higher the vehicle speed, the greater the braking force required for deceleration. However, since the braking force increases accordingly, an appropriate braking force can always be achieved regardless of the vehicle speed. The vehicle can be surely decelerated while preventing slipping of the drive wheels.

According to the regeneration control device for a hybrid electric vehicle of the invention of claim 6, in addition to claims 1 to 5, when the slip is judged by the slip detection means, even when the downshift timing is not reached, the downshift is performed. Was made to run.
For example, as shown in FIG. 3, since the regenerative torque of the motor shifts in a stepwise manner when shifting down, the slip can be suppressed by executing the shifting down according to the slip determination, and becomes unstable due to the slip. It is possible to stabilize the running of the vehicle that has fallen.

It is a whole lineblock diagram showing the regeneration control device of the hybrid electric vehicle of an embodiment. It is a figure which shows the relationship between the output characteristic and electric power generation characteristic of an electric motor. It is explanatory drawing which compared the control condition of the regeneration torque of the motor by motor deceleration mode with the fluctuation | variation condition of the engine brake in engine deceleration mode. FIG. 3 is a control block diagram of a vehicle ECU for executing a motor deceleration mode. It is a figure which shows the map for correction value calculation.

Hereinafter, an embodiment of a regeneration control device for a hybrid electric vehicle embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a regeneration control device for a hybrid electric vehicle 1 according to the present embodiment.
The hybrid electric vehicle 1 is a so-called parallel type hybrid vehicle, and is configured as a truck in this embodiment. In the following description, the hybrid electric vehicle 1 may be referred to as a vehicle.
An input shaft of a clutch 4 is connected to an output shaft of a diesel engine (hereinafter referred to as an engine) 2, and a rotary shaft of an electric motor 6 that can generate electric power, such as a permanent magnet synchronous motor, is connected to the output shaft of the clutch 4. The input shaft of the automatic transmission 8 is connected via The automatic transmission 8 automates the connection / disconnection operation of the clutch 4 and the switching operation of the shift stage on the basis of a general manual transmission. The second speed is set as the starting stage. Of course, the gear stage of the transmission 8 is not limited to this, and can be arbitrarily changed.

The output shaft of the transmission 8 is connected to the left and right drive wheels 16 via a propeller shaft 10, a differential device 12 and a drive shaft 14. Accordingly, when the clutch 4 is disengaged, only the electric motor 6 is connected to the drive wheel 16 side via the transmission 8, and when the clutch 4 is connected, both the engine 2 and the electric motor 6 are connected to the drive wheel 16 side via the transmission 8. The
The electric motor 6 operates as a motor when the DC power stored in the traveling battery 18 is converted into AC power by the inverter 20 and supplied thereto, and after the driving force is appropriately shifted by the transmission 8, the driving wheel 16 is driven. The vehicle 1 is caused to travel by being transmitted to the vehicle. Further, during coasting operation in which the vehicle decelerates when the accelerator is off, the electric motor 6 operates as a generator to generate AC power, and the vehicle 1 is decelerated while generating regenerative torque and applying braking force to the drive wheels 16. . Then, the generated AC power is converted into DC power by the inverter 20 and then charged to the battery 18, whereby the deceleration energy of the vehicle 1 is recovered as electric energy and is then effectively used for traveling by the electric motor 6. .

As will be described in detail later, in the regenerative control during coasting operation, the clutch 4 between the engine 2 and the electric motor 6 is disconnected and switched to the motor deceleration mode in order to increase the power generation amount as much as possible. Regenerative torque is controlled along a maximum torque line that achieves maximum power generation (regeneration control means).
For example, when the SOC of the battery 18 is in the vicinity of the upper limit (for example, 70%) of the control range and charging is not required during coasting operation, the clutch 4 is connected without regenerative control of the motor 6 to switch to the engine deceleration mode. And the vehicle 1 is decelerated while acting on the drive wheels 16 using the engine brake as a braking force instead of the regenerative torque of the electric motor. Note that switching to the engine deceleration mode is not necessarily based on the SOC of the battery 18, and mode switching may be performed according to other requirements.
On the other hand, the driving force of the engine 2 is transmitted to the transmission 8 via the rotating shaft of the electric motor 6 when the clutch 4 is connected, and is transmitted to the drive wheels 16 after being appropriately shifted. Accordingly, when the driving force of the engine 2 is transmitted to the driving wheels 16 and the electric motor 6 does not operate as a motor, only the driving force of the engine 2 is transmitted to the driving wheels 16 via the transmission 8, and the electric motor When the motor 6 operates as a motor, the driving forces of the engine 2 and the electric motor 6 are both transmitted to the driving wheel 16 via the transmission 8.

In addition, when the SOC of the battery 18 decreases and the battery 18 needs to be charged, the electric motor 6 operates as a generator even when the vehicle is traveling, and the electric motor 6 is used by using a part of the driving force of the engine 2. Is generated, and the generated AC power is converted into DC power by the inverter 20 and then the battery 18 is charged.
The vehicle ECU 22 controls the connection / disconnection control of the clutch 4 and the shift of the transmission 8 by controlling driving of an actuator (not shown) in accordance with the operation state of the vehicle and the engine 2 and information from the engine ECU 24, the inverter ECU 26 and the battery ECU 28. In addition to performing stage switching control, integrated control for appropriately operating the engine 2 and the electric motor 6 is performed in accordance with various control states such as these control states and vehicle start, acceleration, and deceleration.

When performing such control, the vehicle ECU 22 detects the accelerator opening sensor 32 that detects the depression amount Acc of the accelerator pedal 30, the vehicle speed sensor 34 (vehicle speed detection means) that detects the vehicle speed V, and the electric motor 6. Required torque required for traveling of the vehicle based on the detection results of the rotational speed sensor 36 that detects the rotational speed N of the engine 2 as the input rotational speed of the transmission 8 and the brake sensor 40 that detects the depression operation of the brake pedal 39. And the torque generated by the engine 2 and the torque generated by the electric motor 6 are set from the required torque.
The engine ECU 24 performs various controls necessary for the operation of the engine 2 itself, and controls the fuel injection amount and the injection timing of the engine 2 so that the engine 2 generates the torque set by the vehicle ECU 22.
On the other hand, the inverter ECU 26 controls the operation of the motor 6 by operating the motor 6 or the generator by controlling the inverter 20 based on the torque that should be generated by the motor 6 set by the vehicle ECU 22.

The battery ECU 28 detects the temperature of the battery 18, the voltage of the battery 18, the current flowing between the inverter 20 and the battery 18, and obtains the SOC of the battery 18 from these detection results, and detects the obtained SOC. The result is sent to the vehicle ECU 22 together with the result.
By the way, as described above, when the vehicle 1 is coasting, if the SOC of the battery 18 does not reach the upper limit of the control range and there is room for charging, the motor deceleration mode is selected and the clutch 4 is disengaged. As described in [Problems to be Solved by the Invention], the regenerative torque of the electric motor 6 at this time is to be controlled on the maximum torque line in order to obtain the maximum power generation amount, but is far from the engine deceleration mode. Braking force, and in many cases, a braking force much larger than that in the engine deceleration mode is generated. Due to the difference in braking force between the modes, the feeling of deceleration experienced by the driver is different. As a countermeasure, if the regenerative torque of the electric motor 6 is limited, the amount of power generation is reduced.

Here, since the inventor always obtains the maximum power generation amount on the maximum torque line of the electric motor 6, it is desirable to control the regenerative torque of the electric motor 6 on the maximum torque line from the viewpoint of the electric power generation amount, and If the rotational speed N of the electric motor 6 is controlled in a rotational range where a regenerative torque close to that of the engine brake can be obtained on the maximum torque line, the same braking force as in the case of the engine brake can be achieved while maintaining the maximum power generation amount, and It was noted that the rotational speed N of the electric motor 6 during the coasting operation can be changed within a certain range according to the shift-down timing of the transmission 8.
Therefore, with this recognition, in the present embodiment, measures are taken to control the regenerative torque of the motor 6 to a value close to the engine brake while maintaining the maximum power generation amount during coasting operation of the vehicle 1 in the motor deceleration mode. Hereinafter, control executed by the vehicle ECU 22 in the motor deceleration mode for the countermeasure will be described.

First, before describing the control in the motor deceleration mode by the vehicle ECU 22, the characteristics of the regenerative torque of the electric motor 6 of the present embodiment will be described in comparison with the characteristics of the engine brake.
FIG. 2 is a diagram showing the relationship between the output characteristics of the electric motor 6 and the power generation characteristics. In the parallel hybrid vehicle 1, the rotation of the engine 2 and the electric motor 6 is always transmitted to the drive wheel 16 side under the same conditions through the respective gear stages of the transmission 8. Are compared on the same rotation scale.
The electric motor 6 at the time of power running control generates a power running torque with the maximum torque line on the positive side being approximately inversely proportional to the rotational speed N as an upper limit, and torque suppression set as a control measure for suppressing excessive torque on the low rotation side Power running torque is limited up to the line. In contrast to the output characteristics during the power running control, the regenerative control has an output characteristic in which the torque is reversed from the positive side to the negative side, and the maximum torque line and the torque suppression line are set on the negative side. Therefore, with the maximum torque line and the torque suppression line as upper limits, the power running torque and the regenerative torque can be arbitrarily controlled within the ranges.

When the regenerative torque of the electric motor 6 is controlled along the maximum torque line during the regenerative control, the electric motor 6 achieves the maximum power generation amount in the entire rotation region (for example, 800 to 2000 rpm) of the maximum torque line. When the rotation decreases and enters the region of the torque suppression line through the lower limit of the maximum torque line, the power generation amount gradually decreases as the rotation decreases. That is, as long as the regenerative torque is controlled on the maximum torque line as long as it is within the rotation range of the maximum torque line, the electric motor 6 can always achieve the maximum power generation amount regardless of the rotation change, while the electric motor 6 on the maximum torque line. By adjusting the rotation speed N, the regenerative torque can be arbitrarily adjusted within a predetermined range (within the range corresponding to the upper and lower limits of the maximum torque line).
Although the regenerative torque is controlled in the motor deceleration mode based on the output characteristics of the electric motor 6 as described above, in the present embodiment, the engine brake generated in the engine deceleration mode is much smaller than the regenerative torque. . More specifically, the magnitude of the engine brake is generated as a value approximating a small regenerative torque near the lower limit generated by the electric motor 6 in the high rotation range of the maximum torque line.

This is because the regenerative torque is generated by active control to recover the deceleration energy of the vehicle 1 as electric energy against the engine brake that naturally occurs due to engine friction. However, since various factors such as the specifications of the engine 2 and the electric motor 6 affect the magnitude relationship between the two, the relationship is not necessarily limited to the above relationship. Therefore, for example, it may be assumed that engine braking occurs so as to approximate a large regenerative torque near the upper limit that occurs in the low rotation range of the maximum torque line, and even in this case, it can be handled without problems as described below. is there.
FIG. 3 is an explanatory diagram comparing the control state of the regenerative torque of the electric motor 6 in the motor deceleration mode with the fluctuation state of the engine brake in the engine deceleration mode.
During coasting operation of the vehicle 1 in the engine deceleration mode, the vehicle ECU 22 connects the clutch 4 and transmits the engine brake to the drive wheel 16 side. In parallel with this, the transmission 8 is sequentially shifted down as the vehicle speed decreases, based on the downshift timing of each gear stage based on the vehicle speed V set in the predetermined shift map. In the shift map of the present embodiment, the shift down timing is stored as the vehicle speed V. However, instead of the vehicle speed V, the rotation speed N of the electric motor 6 for each shift stage may be used.

The engine brake increases stepwise as an absolute value every time switching to the low speed gear side due to downshift, and thereafter gradually decreases as the vehicle speed V decreases, and the above fluctuation is repeated every time the downshift is performed. The clutch 4 is disengaged to prevent the engine stall when the vehicle speed V is sufficiently lowered (when the second speed is selected in the figure), and the engine deceleration mode ends. Since the engine brake is transmitted to the drive wheel 16 side through each gear stage of the transmission 8, the engine brake gradually increases as a whole while fluctuating every shift down from the start to the end of the coasting operation. Change.
On the other hand, the downshift of the transmission 8 is sequentially performed in the same manner during coasting operation in the motor deceleration mode. The downshift is executed based on a shift map set separately from the shift map for the engine deceleration mode. . These shift maps are stored in the vehicle ECU 22 in advance.

The shift down timing of the shift map for the motor deceleration mode is set in advance based on the following knowledge. In short, the downshift timing of each shift stage on the shift map is such that the rotation speed N of the electric motor 6 is maintained in a rotation range where a regenerative torque approximate to the engine brake on the maximum torque line shown in FIG. 2 is obtained. Is set to
That is, in the motor deceleration mode, the regenerative torque of the electric motor 6 is controlled on the maximum torque line in order to achieve the maximum power generation amount, and as shown in FIG. As the vehicle speed V decreases (rotation of the electric motor 6 decreases), it gradually increases and decreases stepwise as an absolute value every time the gear shifts to the low-speed gear side due to downshifting (because the regenerative torque decreases due to increased rotation). This variation is repeated every shift down.

  For example, if the shift down timing is advanced, the regenerative torque at the current shift stage decreases stepwise by switching to the low-speed gear before the regenerative torque sufficiently increases. If the downshift timing is delayed, the regenerative torque at the current gear stage increases sufficiently and then decreases stepwise by switching to the low-speed gear side, so that the regenerative torque tends to increase as a whole. In this way, the rotational speed N of the electric motor 6 and thus the regenerative torque on the maximum torque line can be changed within a certain range in accordance with the downshift timing at each shift stage, while on the other hand, within the rotation region of the maximum torque line. As long as the motor 6 continues to achieve the maximum power generation amount.

  Therefore, the downshift timing of each gear position in the motor deceleration mode is set so that both the regenerative torque before and after the downshift approximate the engine brake corresponding to the vehicle speed V at that time. FIG. 3 shows an example of setting the downshift timing from the sixth speed to the fifth speed, but the downshift timing is the end point (in other words, the maximum value) of the regenerative torque at the current gear position indicated by a in the figure. ) Is determined, on the other hand, the starting point (in other words, the minimum value) of the regenerative torque due to the next shift stage (the shift stage on the low speed gear side) indicated by b in the figure is also determined. For this reason, for example, with reference to the engine brake obtained in the engine deceleration mode at the same vehicle speed V, the maximum value “a” of the regenerative torque is slightly higher, and the minimum value “b” of regenerative torque is slightly lower. Timing is preset. The shift down timing is set in advance for the other shift stages from the same viewpoint (shift control means).

  However, since each gear stage of the original transmission 8 is determined by giving priority to requirements that directly affect the running performance such as the output characteristics of the engine 2 and the electric motor 6 and the vehicle weight, an appropriate shift down is performed. In some cases, the timing cannot be set. FIG. 3 exemplifies the time when the fourth speed is selected, and the gear ratio between the fourth speed and the third speed is separated (a so-called wide ratio), so as shown by the one-dot chain line, If the downshift timing is set so that the regenerative torque of the engine is positioned above and below the engine brake, the regenerative torque at the 4th speed will increase excessively according to the maximum torque line, and the end point will be excessive, and at the 3rd speed The regenerative torque also decreases excessively according to the maximum torque line, and the starting point becomes too small. Therefore, at this time, another problem arises that a large shift shock occurs due to a drop in the regenerative torque before and after the downshift.

Therefore, assuming such a case, for example, the downshift timing is set at a position where the regenerative torque does not become excessive after the downshift to the third speed, and an excessive increase in the regenerative torque at the fourth speed is limited. Thus, the torque limit value for maintaining a constant torque is set slightly higher than the engine brake (regeneration control means).
As described above, the downshift timing of each gear position according to the vehicle speed V and the torque limit value are set as necessary, and these set values are stored in the vehicle ECU 22 in advance.

Next, control actually executed by the vehicle ECU 22 in the motor deceleration mode will be described.
FIG. 4 is a control block diagram of the vehicle ECU 22 for executing the motor deceleration mode.
For example, when the accelerator depression amount Acc detected by the accelerator opening sensor 32 is 0, the depression operation of the brake pedal 39 is not detected by the brake sensor 40, and the vehicle speed V detected by the vehicle speed sensor 34 is equal to or higher than a predetermined value, the vehicle 1 is estimated to be coasting (coasting determination means). When it is determined that the SOC of the battery 18 has not reached the vicinity of the upper limit of the control range during the coasting operation of the vehicle and it is determined that there is room for charging, the vehicle ECU 22 starts the motor deceleration mode.
Simultaneously with the start of the motor deceleration mode, the vehicle ECU 22 disconnects the clutch 4 and maintains the disconnected state of the clutch 4 until the motor deceleration mode ends. Therefore, during the motor deceleration mode, the engine 2 is disconnected from the drive wheel 16 side and the transmission of the engine brake is cut off, and only the regenerative torque of the electric motor 6 is transmitted to the drive wheel 16.
The determination of whether or not the vehicle is coasting and the start determination of the motor deceleration mode are not limited to the above requirements. For example, the accelerator depression amount Acc that is a requirement for coasting operation includes not only complete zero but also the vicinity of zero. May be. In addition, as a requirement for coasting operation, a requirement that the current shift speed is higher than the predetermined shift speed may be added, or a requirement regarding the SOC of the battery 18 may be omitted.

When the motor deceleration mode is started, the vehicle weight calculation unit 42 in FIG. 4 calculates the weight W of the vehicle 1 that fluctuates in accordance with the cargo load (vehicle weight detection means), and the road surface gradient calculation unit 44 calculates the current vehicle. 1 is calculated (road surface gradient detection means), and the slip determination unit 46 determines whether or not the drive wheel 16 slips (slip determination means).
The calculation process of the vehicle weight W and the road surface gradient θ and the determination process of the presence or absence of slip of the drive wheels 16 are well-known techniques and will not be described in detail. For example, the vehicle weight W is described in Japanese Patent Laid-Open No. 2001-304948. As described above, after the driving force of the vehicle 1 generated by the engine torque is corrected by air resistance or the like, the actual acceleration of the vehicle 1 obtained from the vehicle speed V is divided by the value corrected by the road surface gradient θ.

The road surface gradient θ is reduced to the road surface gradient θ by subtracting the actual longitudinal acceleration detected by the wheel speed sensor from the longitudinal acceleration detected by the acceleration sensor, as described in, for example, Japanese Patent Application Laid-Open No. 2003-097945. The resulting acceleration can be obtained, and the acceleration caused by the road surface gradient θ can be obtained by converting the angle. The presence or absence of slip of the drive wheel 16 can be determined by comparing the rotation speed of the drive wheel 16 with the average rotation speed of the left and right driven wheels, for example, and the rotation speed of the drive wheel 16 is higher than the average rotation speed of the driven wheels. A slip determination may be made when the value is greater than a predetermined value.
The shift timing correction unit 48 receives the vehicle weight W from the vehicle weight calculation unit 42, the road surface gradient θ from the road surface gradient calculation unit 44, and the vehicle speed V detected by the vehicle speed sensor 34. In the shift timing correction unit 48, the shift down timing to the next gear position corresponding to the vehicle speed V is read from the shift map set based on the above knowledge, and the shift down timing is corrected based on each input information. For this correction process, the vehicle ECU 22 stores a map for calculating the correction value k for each input information in advance.

  FIG. 5 is a diagram showing a map for calculating a correction value. Here, with respect to the road surface gradient θ, only the case of a descending road is considered, and the correction is not performed without considering the case of an uphill road. As shown in the figure, the correction value k is calculated as a smaller value from the map as the vehicle weight W increases, the descending road gradient θ becomes steeper, and the vehicle speed V increases. Each read-out correction value k is multiplied by the shift down timing (= vehicle speed V), and as a result, the greater the vehicle weight W, the steep slope θ of the descending road, and the higher the vehicle speed V, the lower the shift down timing. It is corrected to the low vehicle speed side. In this example, each correction value k is calculated from a common map, but a map with different characteristics may be set for each input information.

Thus, the shift down timing is corrected, and the target regenerative torque of the electric motor 6 at that time is calculated based on the shift down timing.
Specifically, as described above, the target regenerative torque during coasting operation of the vehicle 1 is basically set on the maximum torque line that can achieve the maximum power generation amount, so that the rotation of the electric motor 6 is performed at times other than the downshift timing. A target regenerative torque is set as a value corresponding to the speed N. In addition, the target regenerative torque is instantaneously reversed to a positive value for gear synchronization when the gears are downshifted. On the other hand, torque limitation that limits excessive regenerative torque due to a wide ratio as described above At the shift stage where the value is set, the target regenerative torque is limited based on this torque limit value.
A target regenerative torque is output from the downshift timing correction unit 48 to the regenerative control unit 50, and a downshift timing is output to the shift control unit 52. In the regenerative control unit 50, the input target regenerative torque is output to the inverter ECU 26 as a command value for driving and controlling the electric motor 6, and the electric motor 6 is operated to achieve the target regenerative torque by the drive control of the inverter ECU 26.

In addition, the shift determination unit 46 receives the slip determination information from the slip determination unit 46 together with the shift down timing from the shift down timing correction unit 48. The shift control unit 52 determines the actual shift down timing in consideration of the slip determination information, and the actuator of the transmission 8 is driven and controlled according to the shift down timing, so that the current shift stage is shifted to the next shift stage on the low speed gear side. And can be switched.
Specifically, when it is determined that there is no slip on the drive wheels 16 based on the slip determination information, the shift to the hour gear stage is executed according to the shift down timing input from the shift down timing correction unit 48. On the other hand, when it is determined from the slip determination information that there is a slip, the shift is immediately executed even if the downshift timing has not yet been reached.
The regenerative control unit 50 also outputs the target regenerative torque to the shift control unit 52, and when the value exceeds the upper limit value of the normal range, the shift control unit 52 immediately executes a downshift to limit the regenerative torque. It is done.
The regenerative control of the electric motor 6 and the shift control of the transmission 8 are executed in cooperation, so that the regenerative torque of the electric motor 6 is maximized during coasting operation of the vehicle 1 in the motor deceleration mode as shown in FIG. While being controlled along the torque line, as the vehicle speed V decreases, the transmission 8 is sequentially shifted down to the gear position on the low-speed gear side. As indicated by a broken line in the figure, the engine deceleration mode ends when the vehicle speed V is sufficiently reduced.

Thus, during coasting operation, the electric motor 6 is regeneratively controlled on the maximum torque line, and at this time, the clutch 4 is disengaged, so that all of the deceleration energy of the vehicle 1 is utilized for the regenerative power generation of the electric motor 6. The amount of power generation can be realized. Therefore, the regenerative current is charged in the battery 18 and can be effectively used for the subsequent running by the electric motor 6, thereby greatly contributing to the reduction in fuel consumption.
As described above, the downshift timing of each shift stage on the shift map is such that the regenerative torque before and after the downshift is a value that approximates the engine brake generated according to the vehicle speed V in the engine deceleration mode. Is set to For this reason, the electric motor 6 during coasting operation in the motor deceleration mode is held in a rotation range where torque near the engine brake can be obtained, and as a result, the electric motor 6 generates torque near the engine brake at any gear position to It is possible to realize a deceleration feeling similar to the engine deceleration mode by braking. For this reason, the difference in the feeling of deceleration caused by the difference in braking force between the engine deceleration mode and the motor deceleration mode can be eliminated, thereby preventing the driver from feeling uncomfortable.

Further, as in the case of selecting the fourth speed shown in FIG. 3, the excessive increase of the regenerative torque at the fourth speed is limited based on the torque limit value at the wide ratio shift stage. Therefore, an increase in the regenerative torque drop before and after the downshift can be suppressed, and the occurrence of a shift shock can be prevented in advance. Although the regenerative torque of the electric motor 6 deviates from the maximum torque line and the power generation amount is reduced due to the limit of the torque limit value, the reduction in the power generation amount is only temporary, and therefore, the shift shock that is more important is prevented. Is prioritized.
Further, the shift down timing of each gear stage read from the shift map is corrected to the lower vehicle speed side as the vehicle weight W is larger, the descending road gradient θ is steeper, and the vehicle speed V is higher. The transmission 8 is controlled to be shifted based on the down timing. As shown in FIG. 3, at each shift stage, the regenerative torque gradually increases as the vehicle speed V decreases along the maximum torque line, and a large braking force acts on the vehicle 1.
As the vehicle weight W increases, the driving wheel 16 is less likely to slip, and a large braking force is required for deceleration. The steep slope θ of the descending road requires a larger braking force for deceleration. As the vehicle speed V is higher, a larger braking force is required for deceleration. However, the shift down timing is corrected to the lower vehicle speed side according to these requests, and the braking force increases. Therefore, an appropriate braking force can always be realized regardless of the vehicle weight W, the descending road gradient θ, or the vehicle speed V, and the vehicle 1 can be surely decelerated while preventing slipping of the drive wheels 16 due to excessive braking force. be able to.

In addition, when a slip occurs on the drive wheel 16 during the coasting operation of the vehicle 1, the shift is immediately executed even if the downshift timing has not yet been reached. As shown in FIG. 3, the regenerative torque of the electric motor 6 shifts in a stepwise manner when shifting down, so that the slip can be suppressed by executing the shifting down according to the slip determination, and becomes unstable due to the slip. The traveling of the vehicle 1 that has fallen can be stabilized.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the hybrid electric vehicle 1 is configured as a truck. However, the present invention is not limited to this, and may be embodied as, for example, a passenger car.

In the above-described embodiment, the transmission 8 that automates the connection / disconnection operation of the clutch 4 and the switching operation of the shift stage based on a general manual transmission is used. However, a so-called dual clutch transmission may be used. . The dual clutch type transmission is configured by connecting gear mechanisms divided into odd-numbered stages and even-numbered stages to the electric motor 6 side through respective clutches, and transmits power by connecting the clutch of one gear mechanism. At this time, the clutch of the other gear mechanism is disconnected and switched to the next predicted gear stage in advance, and when the shift timing is reached, the connected state of both clutches is reversed and power transmission by the other gear mechanism is started. It is. Also in such a dual clutch transmission, the same effect can be obtained by taking the measures described in the above embodiment.
In the above embodiment, the shift down timing read from the shift map is corrected based on the vehicle weight W, the road surface gradient θ, and the vehicle speed V, and when a slip occurs, the downshift is performed immediately regardless of the downshift timing. It is not limited to. For example, any requirement may be omitted, or all the requirements may be omitted, and the downshift timing read from the shift map may be applied to the shift control as it is.

2 Engine 4 Clutch 6 Electric motor 8 Transmission 16 Drive wheel 22 Vehicle ECU
(Coasting operation determination means, regeneration control means, shift control means,
Vehicle weight detection means, road surface gradient detection means, slip determination means)
34 Vehicle speed sensor (vehicle speed detection means)

Claims (6)

The motor is connected to the drive wheels of the vehicle via a transmission, and the engine is connected to the motor via a clutch, and the clutch is connected during coasting operation where the vehicle decelerates when the accelerator is off. The engine deceleration mode in which the engine brake by the engine is transmitted to the drive wheels through the transmission to decelerate the vehicle, or the motor deceleration mode in which the regenerative torque by the motor is transmitted to the drive wheels through the transmission to decelerate the vehicle. In a hybrid electric vehicle that selectively executes one of the following:
Coasting operation determining means for determining coasting operation of the vehicle;
When it is determined that the coasting operation is being performed by the coasting operation determination means and the motor deceleration mode is selected, the clutch between the motor and the engine is disengaged, and the regenerative torque of the motor is obtained with the maximum power generation amount. Regenerative control means for controlling on the negative side maximum torque line,
In the coasting operation in the motor deceleration mode, when the transmission is shifted down as the vehicle speed decreases, the regenerative torque in the vicinity of the engine brake in the engine deceleration mode on the maximum torque line is obtained in the rotation range of the motor. A regenerative control device for a hybrid electric vehicle, comprising: a shift control means for executing a shift down of the transmission.   The regenerative control means controls the regenerative torque of the motor as compared with the engine brake by control on the maximum torque line due to the separation between the current shift stage of the transmission and the next shift stage on the low-speed gear side. 2. The regenerative control device for a hybrid electric vehicle according to claim 1, wherein when it increases excessively, the regenerative torque is kept constant until the downshift to the next shift stage. Vehicle weight detecting means for detecting the weight of the vehicle,
The shift control means corrects the downshift timing to a lower vehicle speed side as the vehicle weight detected by the vehicle weight detection means increases, and executes the downshift based on the corrected timing. A regeneration control device for a hybrid electric vehicle according to claim 1 or 2. Road surface gradient detecting means for detecting the gradient of the road surface on which the vehicle is running,
When the road surface gradient detected by the road surface gradient detection unit is on the downhill road side, the shift control unit corrects the shift down timing to the low vehicle speed side as the downhill road slope is steep, and after the correction The regenerative control device for a hybrid electric vehicle according to any one of claims 1 to 3, wherein downshifting is executed based on the timing. Vehicle speed detecting means for detecting the speed of the vehicle,
The shift control means corrects the downshift timing to a lower vehicle speed side as the vehicle speed detected by the vehicle speed detection means is higher, and executes the downshift based on the corrected timing. 5. A regeneration control device for a hybrid electric vehicle according to any one of 1 to 4. Slip determination means for determining the slip of the drive wheel of the vehicle,
The hybrid according to any one of claims 1 to 5, wherein the shift control means executes a shift down even when the slip determination means determines that the slip has not yet reached the downshift timing. Electric vehicle regeneration control device.

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