JP3292130B2 - Series hybrid electric vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid electric vehicle having an engine and a motor, and more particularly to a series hybrid electric vehicle using an engine exclusively for power generation.

[0002]

2. Description of the Related Art Conventionally, engines and electric motors (motors)
Various types of so-called hybrid electric vehicles have been developed, and some of them have already been put into practical use. Examples of such hybrid electric vehicles include a series hybrid electric vehicle in which an engine is dedicated to driving a generator, and a parallel hybrid electric vehicle in which an output shaft and wheels of an engine are mechanically connected. Other than these, a hybrid electric vehicle having both characteristics of the parallel hybrid electric vehicle and the series hybrid electric vehicle has been developed.

[0003] Generally, hybrid electric vehicles are
Two traveling modes, a battery traveling mode and a hybrid traveling mode, are provided as traveling modes, and these two traveling modes are selectively used depending on conditions such as a load on a vehicle and a state of charge of a battery. Here, the battery running mode is a running mode used when the remaining capacity of the battery is relatively large, in which the engine is stopped, the electric power stored in the battery is supplied to the motor, and the running is performed only by the driving force of the motor. Running mode.

[0004] The hybrid running mode is a running mode used when the remaining capacity of the battery is relatively small, and is a mode in which the vehicle runs using the operation of the engine. Therefore, in the series hybrid electric vehicle, the hybrid driving mode is a mode in which the generator is driven by the engine to generate electric power, and the electric power is supplied to the motor to run. In the parallel hybrid electric vehicle, the hybrid driving mode is the hybrid driving mode. The traveling mode is a mode in which the driving force of the engine is used as it is as the driving force for traveling.

[0005] Fig. 3 is a schematic diagram showing a main part of a series hybrid electric vehicle among the hybrid electric vehicles as described above.
Is an inverter, 55 is a battery, 56 is a generator, and 57 is an engine. In the hybrid electric vehicle, as described above, in the battery running mode, the generator 56 is driven by the engine 57 dedicated to power generation, and the power generated by the generator 56 drives the motor 51 and charges the battery 55. Done. At this time, the engine speed is maintained at a predetermined speed at which the power generation efficiency of the generator 56 is maximized.

When the load on the motor 51 increases suddenly, for example, when the vehicle is rapidly accelerating or climbing a steep road, the voltage of the battery 55 is significantly reduced because the battery 55 discharges a large current. At this time, when the battery voltage falls below a predetermined value, the load of the generator 56 suddenly decreases due to the characteristics of the generator 56, and in the hybrid traveling mode of the series hybrid electric vehicle, the engine 57 overruns (overruns). There is a risk. It should be noted that the degree of such a decrease in the battery voltage depends on the degree of deterioration of the battery 55, and the more the deterioration of the battery 55, the greater the decrease in the voltage value.

The overrun of the engine 57 will be briefly described with reference to the drawings. FIG. 5 shows the relationship between the generator load torque and the engine torque. The horizontal axis represents the engine speed and the generator speed. Number, vertical axis is generator 56
Of the load torque. Also, in the figure, line a is a characteristic line when the battery voltage is a normal voltage value (about 350 V), line b is a characteristic line when the battery voltage is reduced (about 280 V), and line c is a line when the battery voltage is generated. It is a characteristic line of engine torque.

First, at the time of sudden start, at the time of sudden start, the battery voltage is reduced to the normal output voltage (about 350 V).
V) (about 280 V), the load torque of the generator 56 moves on the line b. Here, when the engine 57 and the generator 56 rise to the target rotational speed, the load torque characteristic of the generator 56 has a right-up characteristic like the torque characteristic of the engine 57 up to the point B. Rises slowly.

However, when the engine speed (and the generator speed) exceeds the point B, the characteristics of the generator 56 decrease to the right, while the torque characteristics of the engine 57 remain upward. The load on the generator 56 is relatively reduced, and the engine speed is rapidly increased. Next, a case where the vehicle is suddenly accelerated from the steady traveling state in the hybrid traveling mode will be described. First, during steady running, the engine speed is kept substantially constant at the target speed,
Operation is performed at a normal output voltage (about 350 V) (point A in the figure). At this time, if the vehicle is rapidly accelerated, the battery voltage drops (about 280 V) (point C in the figure), and the generator 5
Since the load torque of No. 6 sharply decreases, the engine speed also sharply increases.

Therefore, conventionally, such an engine 5
In order to prevent the overrun of No. 7, in the hybrid running mode of the series hybrid electric vehicle, control has been performed to suppress the output torque of the motor 51 when the battery voltage falls below a predetermined value. And the motor 51
, The sudden decrease in the battery voltage is prevented, and the overrun of the engine 57 is prevented.

FIG. 4 is a flow chart for briefly explaining the above-mentioned conventional technique. First, in the hybrid traveling mode of the series hybrid electric vehicle, it is determined in step S101 whether the voltage value of the battery 55 has decreased to a predetermined value or less. If the voltage value is equal to or less than the predetermined value, the process proceeds to step S102, where the torque suppression control of the motor 51 is performed. Note that such torque suppression control is performed by limiting the electric power supplied to the motor 51. If the voltage value is larger than the predetermined value, the torque suppression control is not executed.

[0012]

However, such a conventional technique has a problem that the power performance of the vehicle is significantly reduced because the output of the motor is directly suppressed. In particular, the voltage drop occurs when the driver is requesting output, such as when the vehicle is rapidly accelerating or climbing a steep road, and in such a case, suppressing the output of the motor impairs drivability. There was also a problem of getting lost.

Japanese Patent Application Laid-Open No. 6-225403 discloses a technique in which the output of a generator is changed according to the vehicle load. That is, in this technique, the output of the generator is controlled to a high level when the vehicle load is equal to or more than a predetermined value, and is controlled to a predetermined low level when the vehicle load is less than the predetermined value. However, this technology
This technology is applied to a parallel hybrid electric vehicle, and is difficult to apply to a series hybrid electric vehicle. Further, in the above-described technology, when the vehicle load becomes equal to or more than a predetermined value, the engine speed is increased to increase the output of the generator. Therefore, when this technology is applied to a series hybrid electric vehicle, the engine overrun is promoted. There is a problem that such control is performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a series-type hybrid electric vehicle in which overrun of an engine is reliably prevented without impairing drivability as much as possible. I do.

[0015]

In the series hybrid electric vehicle of the present invention, the engine normally rotates at a substantially constant rotational speed at which the power generation efficiency of the generator becomes highest, and the power is generated by the generator. Power is supplied to the battery. Further, the electric motor is operated by electric power supplied to the battery or electric power directly supplied from the generator, thereby driving the drive system of the vehicle.

When the voltage detecting means detects that the voltage of the battery is equal to or lower than the predetermined value, the engine control means determines that the engine speed is lower than the normal speed and the generator Rotation at which power generation is stopped
The number is controlled to suppress engine overrun. What
The number of revolutions at which the generator stops generating power depends on the engine
It is preferably an idle speed. Also, voltage detecting means
The battery voltage drop rate exceeds the predetermined drop rate.
Is detected by the engine control means.
Control the number of revolutions to a certain number of revolutions lower than a certain number of revolutions
It may be configured as follows. In this case, lower than a certain speed
The predetermined rotation speed is the rotation speed at which power generation by the generator is stopped.
It is preferred that Furthermore, this fixed speed
The lower predetermined speed is the idle speed of the engine
Is preferred.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a series hybrid electric vehicle as an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic functional block diagram showing main functions of the series hybrid electric vehicle, and FIG. 5 is a flowchart for explaining FIG. First, the main configuration of a series hybrid electric vehicle will be described with reference to FIG. 1. In the figure, 11 is a motor (motor), 13 is wheels, 14 is an inverter, 15 is a battery, 16 is a generator, and 17 is an engine. is there.

The hybrid electric vehicle is configured as a series-type hybrid electric vehicle, and an engine 17 is provided mainly for driving a generator 16 to supply electric power to a battery 15. That is, the vehicle is configured to run by the rotational driving force of the motor (electric motor) 11. The motor 11
To the battery 15 and the generator 16 via the inverter 14
Are electrically connected, and drive wheels 13 are connected to an output shaft of the motor 11.

Further, the inverter 14, the generator 16 and the engine 17 are connected to a controller 18 as an engine control means, and the controller 18 controls the operation of the inverter 14, the generator 16 and the engine 17 respectively. It has become. Further, the battery 15 is provided with a charge capacity sensor 19 capable of detecting the remaining power of the battery 15, and this charge capacity sensor 19 is also connected to the controller 18 as shown.

The controller 18 changes the running mode of the vehicle to one of the battery running mode and the hybrid running mode based on the detection signal from the charge capacity sensor 19 and the detection signals from other sensors (not shown). It is designed to switch. That is, when the remaining capacity of the electric power stored in the battery 15 is detected by the charging capacity sensor 19 to be equal to or more than a predetermined value,
The controller 18 stops the operation of the engine 17 and the generator 16, and drives the motor 11 by the electric power stored in the battery 15 (battery running mode).

When the remaining capacity of the electric power stored in the battery 15 decreases and it is detected that the remaining capacity is equal to or less than a predetermined value, the controller 18 operates the engine 17. Then, the generator 17 is operated by the engine 17, and the electric power obtained by the generator 16 is stored in the battery 15, and the electric power is supplied to the motor 11 via the inverter 14. (Hybrid driving mode).

In this hybrid running mode, the engine speed is controlled by the controller 18 to a substantially constant speed. Here, the constant rotation speed is a rotation speed at which the efficiency of the generator 16 is highest. In the hybrid running mode, for example, the throttle opening is controlled to the target throttle opening by the controller 18, and the throttle opening is fed back so that the rotation speed of the engine 17 maintains the target rotation speed (the constant rotation speed described above). It is controlled.

The charge capacity sensor 19 attached to the battery 15 detects the voltage value of the battery 15 in addition to the remaining power. That is,
The charge capacity sensor 19 also has a function as a battery voltage sensor (voltage detection means). In the series hybrid electric vehicle of the present invention, when the voltage value of the battery 15 is detected to be equal to or less than the predetermined value by the battery voltage sensor 19 in the hybrid driving mode, the rotation speed of the engine 17 is normally set by the controller 18. Is controlled to a predetermined rotation speed lower than the rotation speed (the constant rotation speed described above).

Note that such control is mainly performed for the following reasons. In other words, when the load on the motor 11 increases suddenly, such as during rapid acceleration or when traveling on a steep uphill, the battery 15 discharges a large current.
The voltage of No. 5 drops significantly. At this time, when the battery voltage falls below a predetermined value, the load on the generator 16 suddenly decreases in the hybrid running mode, and the engine 17 may overrun.

Therefore, in the series hybrid electric vehicle of the present invention, as described above, when the voltage value of the battery 15 is detected to be equal to or lower than the predetermined value in the hybrid driving mode, the rotation speed of the engine 17 is reduced. Thus, overrun of the engine 17 is prevented. In this case, specifically, the generator 16
Is kept on, and the engine 17 is forcibly reduced to the idle speed.

In such a case, the power generation by the generator 16 is stopped because the engine 17 is in the idling operation state. At this time, however, the motor 11 is driven by the electric power stored in the battery 15 and thus the motor 11 is driven. Also, there is no loss of drivability. Further, when the load on the motor 11 is reduced after the rapid acceleration or the like is completed, the voltage value of the battery 15 returns to a value close to the original value even if it rises again. The number is raised again to resume power generation.

The operating state in which the load on the motor 11 suddenly increases as described above is often temporary.
Therefore, even if the engine 17 is idle and the power generation is stopped, the electric power stored in the battery 15 can sufficiently drive the motor 11. Since the series hybrid electric vehicle as one embodiment of the present invention is configured as described above, an example of the operation will be described below with reference to the flowchart shown in FIG.

First, in the hybrid running mode, it is determined in step S1 whether or not the voltage of the battery 15 has dropped to a predetermined value or less. At this time, if the battery voltage is higher than the predetermined value, the process proceeds to step S2, and the operation state of the engine 17 is controlled to the normal power generation operation state. If it is determined in step S1 that the battery voltage is equal to or lower than the predetermined value, the process proceeds to step S3, in which the engine 17 is forcibly controlled to the idle operation state and the process returns. Then, until it is determined again in step S1 that the battery voltage has become larger than the predetermined value,
This idle operation is continued.

As described above, according to the series hybrid electric vehicle of the present invention, with the simple configuration as described above,
The engine 17 can be used without affecting the power performance of the vehicle.
Overrun can be reliably prevented. As a result, drivability does not deteriorate and the driver does not feel uncomfortable. Further, according to the present invention, only by changing the control software of the controller 18 without adding new parts and the like,
Since overrun of the engine 17 can be prevented, there is an advantage that cost and weight do not increase.

It should be noted that the series hybrid electric vehicle of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, when it is detected that the voltage of the battery 15 is equal to or lower than a predetermined value, the engine 17
Is controlled to the idle speed, but the engine speed at this time is not limited to the idle speed, and the engine speed is such that the power generation of the generator 16 is stopped. I just need.

In this embodiment, it is determined whether or not the voltage value of the battery 15 is equal to or less than a predetermined value. However, not the battery voltage value itself, but the voltage drop rate (per unit time) Voltage drop amount), and when the voltage drop rate exceeds a predetermined drop rate,
Engine speed control may be performed.

[0032]

As described above in detail, according to the series hybrid electric vehicle of the present invention, when the voltage detection means detects that the voltage of the battery is equal to or lower than the predetermined value, the engine control means controls the engine. The rotation speed of the generator is lower than the normal rotation speed , and the power generation of the generator
Is controlled to the number of revolutions at which the engine is stopped, so that there is an advantage that overrun of the engine can be reliably prevented without deteriorating drivability. Further, according to the present invention, it is not necessary to add a new part or the like, and only the control software needs to be changed. Therefore, there is an advantage that the cost and weight do not increase. Also, voltage detection
Output voltage causes the battery voltage drop rate to exceed the predetermined drop rate.
Is detected by the engine control means.
Gin rotation speed is controlled to a certain rotation speed lower than a certain rotation speed.
The same advantages as described above can be achieved when
You.

[Brief description of the drawings]

FIG. 1 is a schematic functional block diagram illustrating main functions of a series hybrid electric vehicle as one embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of the series hybrid electric vehicle as one embodiment of the present invention.

FIG. 3 is a schematic functional block diagram showing a main part configuration of a general series-type hybrid electric vehicle.

FIG. 4 is a flowchart for briefly explaining a conventional technique for preventing engine overrun in a series hybrid electric vehicle.

FIG. 5 is a diagram showing a relationship between a generator load torque and an engine torque in a general series hybrid electric vehicle.

[Explanation of symbols]

 Reference Signs List 11 motor (motor) 15 battery 16 generator 17 engine 18 engine control means (controller) 19 voltage sensor (voltage detection means)

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-10-70801 (JP, A) JP-A-3-169203 (JP, A) JP-A-7-336809 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B60L 11/10 B60K 6/02 F02D 29/06

Claims (5)

(57) [Claims] 1. An engine that rotates at a substantially constant speed during normal operation, a generator driven by the engine, a battery for storing power generated by the generator, and a battery supplied from the battery or the generator. An electric motor that drives the drive system of the vehicle with the electric power, voltage detection means for detecting the voltage of the battery, and when the voltage detection means detects that the voltage of the battery is equal to or less than a predetermined value, the engine of the engine the rotational speed rather lower than the predetermined rotational speed, and wherein the power generation of the generator is equipped with an engine control unit for controlling the rotational <br/> number rotation being stopped, series hybrid electric Car. 2. The number of revolutions at which power generation of the generator is stopped is:
Characterized in that it is the idle speed of the engine,
The series hybrid electric vehicle according to claim 1. 3. An engine which rotates at a substantially constant speed during normal operation.
An engine, a generator driven by the engine , a battery for storing power generated by the generator, and a vehicle powered by the battery or power supplied from the generator.
An electric motor for driving the drive system of the above, voltage detecting means for detecting the voltage of the battery , and a rate of decrease of the battery voltage determined by the voltage detecting means.
If it is detected that the rate of decrease has been exceeded, the rotation of the engine
Control the number of rotations to a predetermined rotation number lower than the predetermined rotation number.
Engine control means.
Leeds-type hybrid electric vehicle. A predetermined rotation speed lower than the predetermined rotation speed;
Is the number of revolutions at which power generation by the generator is stopped.
The series-type hybrid electric according to claim 3, which is a feature.
Car. A predetermined rotation speed lower than the predetermined rotation speed;
Is the idle speed of the engine .
The series-type hybrid electric automatic machine according to claim 3,
car.