JPH11332013A - Vehicle drive system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To facilitate the design of an engine start-related configuration in a vehicle drive system using both an engine and a wheel motor and to reduce the size. SOLUTION: The electric power of an auxiliary battery 20 is DC / DC.
The voltage is boosted by converter 32 and stored in capacitor 24. With the power of the capacitor 24, the wheel motor 26
Generates assist propulsion. A starter motor 44 for starting the engine 10 is connected to the booster side capacitor 24 of the DC / DC converter 32. When starting the engine, the boost function of the DC / DC converter 32
The electric power from auxiliary battery 20 is converted into electric power of a voltage necessary for starting the engine, and stored in capacitor 24.
The supply voltage to the starter motor 44 can be freely set using the existing components such as the DC / DC converter 32 and the capacitor 24. By increasing the supply voltage, the size of the starter motor 44 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle drive system that generates a propulsion force of a vehicle using an engine and an assist motor, and more particularly to an improvement in a configuration related to engine starting. The assist motor is, for example, a wheel motor provided on a wheel.

[0002]

2. Description of the Related Art Conventionally, electric vehicles have attracted attention from the viewpoint of low pollution. One type of electric vehicle is a vehicle with a wheel motor. FIG. 1 shows an example of the configuration of a vehicle with a wheel motor. The engine 10, which is an internal combustion engine, is connected to a front wheel 16 via a transmission 12 and an axle 14. The front wheel 16 is driven by the output of the engine 10. The engine 10 is started by a starter motor 18 and the starter motor 1
8 is driven by the power of the auxiliary battery 20. The voltage of the auxiliary battery 20 is, for example, 12V. The auxiliary battery 20 is charged by the power generated by the alternator 19 driven by the output of the engine 10.

[0003] DC / D with respect to the power of auxiliary battery 20
The voltage is boosted by the C converter 22. The boosted power is stored in the capacitor 24. Electric power is supplied from the capacitor 24 to the left and right wheel motors 26 via the inverter. The stator of the wheel motor 26 is fixed to the vehicle body, and the rotor is fixed to the rear wheel 28. Therefore, the output of the wheel motor 26 causes the rear wheel 2
8 is driven.

As described above, in the system shown in FIG. 1, the power of the auxiliary battery 20 is converted into high-voltage power, and the wheel motor 26 is driven using the converted power. The capacitor 24 is for temporarily storing the boosted power. When the vehicle decelerates, the wheel motor 2
6 performs regenerative braking, and the power generated by the regenerative braking is also stored in the capacitor 24.

In the system shown in FIG. 1, the engine 10 generates the main propulsion of the vehicle, and the wheel motor 26 generates the assist propulsion. For example, in a situation where the coefficient of friction of the road surface is low, for example, on an uphill road on a snowy road, the front wheel 16 may slip. At this time, the rear propulsion force of the rear wheel 2
8 is driven, and the vehicle runs stably. Further, the wheel motor 26 can be driven by the electric power obtained by the regenerative braking of the wheel motor 26. By providing the wheel motor 26 as the assist motor in this way, the kinetic performance of the vehicle can be improved, and the fuel efficiency can be improved.

Further, since the motor is directly mounted on the wheel, (1) transmission system components such as a drive shaft and a space therefor can be omitted, and transmission loss is reduced. (2) The driving force of one motor is reduced. Since the driving force can be given independently to the left and right wheels instead of being distributed to the left and right wheels, it is possible to control the left and right driving forces independently, thereby obtaining high exercise performance. Is obtained.

[0007]

However, the system shown in FIG. 1 has the following problems in starting the engine. FIG.
In this system, the starter motor 18 is rotated by the electric power of the auxiliary battery 20, and the engine 10 is thereby started. The torque required for cranking the engine 10 is determined by the engine specifications. On the other hand, the supply voltage to the starter motor 18 is determined by the voltage of the auxiliary battery 20, and the supply voltage cannot be freely changed. Therefore, in the development of the system, the required torque on the engine side must be generated with the power of the predetermined supply voltage, so that the design of the starter motor may not be easy. Further, since the supply voltage cannot be changed, it is necessary to increase the size of the starter motor in accordance with the required cranking torque on the engine side. As the size of the starter motor increases, the efficiency decreases and the cost increases. In order to increase the current value of the starter motor, it is necessary to change related parts such as a relay and a wire harness, and the cost may be increased by changing the parts.

If the amount of stored power in the auxiliary battery 20 decreases, sufficient electric power cannot be supplied to the starter motor 18 and it becomes difficult to start the engine 10.
In a cold region, such a situation is likely to occur, and also when the battery performance is deteriorated. In particular, in the system of FIG. 1, since the wheel motor 26 is driven using the power of the auxiliary battery 20, the power storage amount of the auxiliary battery 20 may be reduced.

As a reference technique, Japanese Patent Application Laid-Open No. 5-296128
In Japanese Patent Application Laid-Open Publication No. H11-107, the startability is improved by providing a dedicated capacitor for starting the engine. The dedicated capacitor is charged by the power of the auxiliary battery, and the starter motor is driven by the power of the dedicated capacitor. When the voltage value of the auxiliary battery drops, the dedicated capacitor is charged by using the power from another energy source, and the startability is ensured. However, in the system of the publication, the charging voltage of the dedicated capacitor is equivalent to that of the auxiliary battery, and
The problems related to the starter motor described above remain unsolved. There is also the disadvantage that dedicated capacitors and related equipment must be provided. Furthermore, the system of the publication does not relate to a drive system with an assist motor such as a wheel motor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve the configuration related to engine starting in a vehicle drive system having an engine and an assist motor, to simplify the design of a starter motor and to reduce costs. It is to make it possible to reduce.

[0011]

To achieve the above object, the present invention provides an engine for generating a main propulsion force of a vehicle;
An assist motor for generating an assist propulsion force of the vehicle, a power converter for boosting the power supplied from the auxiliary power storage means to a power of a voltage required by the assist motor, and temporarily converting the power boosted by the power converter. A motor power storage means for supplying the stored power to the assist motor, a starter motor for starting the engine connected to the motor power storage means, and A charging control means for controlling the converter to boost the power supplied from the auxiliary power storage means to power having a voltage required for starting the engine and storing the converted power in the power storage means for the motor; Using the electric power for starting the engine stored in the means to drive the starter motor to start the engine. That. The auxiliary storage means is, for example, an auxiliary battery, and the motor storage means is, for example, a capacitor.

According to the present invention, the starter motor for starting the engine is connected not to the auxiliary power storage means but to the motor power storage means. Before starting the engine, the power from the auxiliary power storage means is boosted by the power converter, and the power is stored in the motor power storage means on the boost side. By using the power converter, the voltage of the power supplied to the starter motor can be set arbitrarily. Since the restriction on the supply voltage is reduced, the design of the starter motor is facilitated. Also, since the supply voltage can be increased, the starter motor can be downsized, the starting current to the starter motor can be reduced, and
Inexpensive related parts (relays, wire harnesses, etc.) can be adopted. Therefore, the starter motor can be reduced in size and efficiency,
Cost reduction can be achieved. Further, since the supply voltage to the starter motor can be increased, the engine can be easily started, and the engine can be reliably started even in a cold region.

Here, in particular, in the system of the type to which the present invention is applied, as described above, the configuration is adopted in which the power from the auxiliary power storage means is boosted by the power converter to obtain the assist motor drive power. . Therefore, power storage means for temporarily storing power for driving the motor after boosting by the power converter is required. By using the motor power storage means and the power converter, the supply voltage to the starter motor can be set freely. Therefore, the preferred effects such as the above-described simplification of the design and the miniaturization of the starter motor can be obtained with a simple configuration using the existing components without the necessity of adding components or complicating the structure. Can be

[0014] Preferably, the starting charge control means of the present invention is provided integrally with a control device for controlling at least a part of the vehicle drive system.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings. FIG. 2 shows a configuration of the vehicle drive system of the present embodiment. 2, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. As in FIG.
The output of the engine 10 mounted on the front part of the vehicle body is
Front wheel 1 via transmission 12 and axle 14
6 and the front wheel 16 is driven.

On the other hand, a DC / DC converter 32 is provided in a configuration related to power assist including the wheel motor 26. The DC / DC converter 32 may have a known configuration. The DC / DC converter 32 boosts the power of the 12 V auxiliary battery 20, and the power is stored in the capacitor 24 on the boost side. As described above, in the system of the present embodiment, since the DC / DC converter 32 is built in, the wheel motor 2
It is necessary to provide the above-mentioned capacitor 24 in order to temporarily store the electric power for driving the capacitor 6. Normally, power conversion is performed with a target voltage required to drive the wheel motor 26. As described later, at the time of starting the engine, power conversion is performed with a target of a voltage suitable for starting the engine. It is also preferable to provide an electric field capacitor instead of the capacitor 24.

The electric power stored in the capacitor 24 is supplied to the left and right wheel motors 26 via the inverter 34. Inverter 34 has a plurality of switching elements, and converts DC power sent from capacitor 24 to AC power. The wheel motor 26 is, for example, a three-phase AC PM synchronous motor. The stator of the wheel motor 26 is fixed to the vehicle, and the rotor is fixed to the rear wheel 28. Therefore, the output of the wheel motor 26 drives the rear wheel 28.

The system ECU 36 includes the wheel motor 2
8 controls the power assist system of FIG. The system ECU 36 operates based on various components including the wheel motor 26, the capacitor 24, the auxiliary battery 20, and the engine 10, and signals input from sensors provided on the components. System E
The CU 36 outputs a control signal to the DC / DC converter 32 to perform a boosting operation. Also, the system ECU 3
6 generates and outputs a signal for controlling the switching operation of the inverter 34. A switching signal for generating an alternating current for generating a desired torque in the wheel motor 26 is generated. When the vehicle decelerates, a switching signal for causing the wheel motor 26 to perform regenerative braking is generated. The electric power generated by the regenerative braking charges the capacitor 24. Further, the system ECU 36
Functions also as the starting charge control means of the present invention. The engine 10 is controlled by an engine ECU (not shown).
It is integrated with U36.

Further, the system shown in FIG. 2 is provided with a voltage sensor 40 for detecting a voltage across the auxiliary battery 20 and a voltage sensor 42 for detecting a voltage across the capacitor 24. The detection signals of the voltage sensors 40 and 42 are sent to the system ECU 36. Next, a configuration related to engine start will be described. The engine 10 includes a starter motor 44
Is started by Although the engine 10 and the starter motor 44 are shown separately in FIG. 2, the starter motor 44 is actually connected to the engine 10 or the transmission 12. As a feature of this embodiment, the starter motor 44
Receives power supply from the capacitor 24. That is,
A power supply system for applying power to the starter motor has been changed from a conventional auxiliary battery to a capacitor on the high voltage side of a DC / DC converter. When the starter switch 46 is closed, power is supplied to the starter motor 44, the starter motor 44 is driven, and the engine 10 is cranked. The opening and closing of the starter switch 46 is also performed by the system ECU 3.
6 is controlled.

In the system shown in FIG. 2, as described with reference to FIG. 1, the engine 10 generates the main propulsion of the vehicle, and the wheel motor 26 generates the assist propulsion. In a situation such as uphill on a snowy road, the vehicle's kinetic performance can be improved by utilizing the assist propulsive force of the wheel motor 26, that is, the driving force of the rear wheel 28. Capacitor 24
Is used to generate assist propulsion, the capacitor 24 is charged again. The stored power is used again the next time propulsion is needed. Further, electric power obtained by regenerative braking of the wheel motor 26 is stored in the capacitor 24, and the wheel motor 26 is driven using this electric power. As a result, the fuel efficiency can be improved.

FIG. 3 shows the overall control of the vehicle drive system according to the present embodiment. When an ignition switch (not shown) is turned on (S100), the system E
The CU 36 is started (S101), and engine start control is performed (S102). Details of the engine start control will be described later. When the engine starts, the assist system,
That is, a system related to the wheel motor 26 is started (S103). Then, travel control is performed (S104), and it is determined whether or not the ignition switch has been turned off (S105). If the ignition is not turned off, the traveling control is continued, and if the ignition is turned off, the entire process ends.

FIG. 4 shows the engine start control process in S102 of FIG. The system ECU 36 has a D
The C / DC converter 32 is controlled to perform a boosting operation (S200). As a result, the power from the auxiliary battery 20 is boosted, and the boosted power is stored in the capacitor 24. Unlike the auxiliary battery 20, the capacitor 2
As for No. 4, charging to a high voltage can be performed by controlling the voltage. Therefore, the target value of the charging voltage of the capacitor 24 is set to, for example, 50V. The system ECU 36
The timer is monitored to determine whether a predetermined timer time has elapsed (S201). If the predetermined timer time has elapsed, the process proceeds to S203. If the timer time has not elapsed, the system ECU 36 determines whether the voltage of the capacitor 24 has become higher than 50 V based on the detection signal of the voltage sensor 42 (S202). If the capacitor voltage is equal to or lower than 50 V, the driving of the converter is continued.
If the capacitor voltage exceeds 50V, the system ECU
36 stops the DC / DC converter 32 (S20).
3). Then, the starter switch 46 is closed, and current flows from the capacitor 24 to the starter motor 44. The capacitor 24 has a small internal resistance and can supply a large current to the starter motor 44 in a short time. As a result, the starter motor 44 is driven, and the engine 10 is cranked (S204). As is well known, at this time, an appropriate amount of fuel is supplied to the engine 10, and the spark plug is ignited using the electric power of the auxiliary battery 20. The system ECU 36 determines whether or not the engine has been started by comparing the engine speed with a predetermined threshold speed (S205). The engine speed is
A rotation sensor (not shown) provided in the engine 10 is input to the system ECU 36 directly or via the engine ECU. If the engine has been started, the processing in FIG. 4 ends, and the process proceeds to S103 in FIG. If the engine has not started, the process returns to S200, and the above-described series of processing is performed again.

The preferred embodiment of the present invention has been described above. In the present embodiment, the starter motor 44 is connected not to the auxiliary battery 20 but to the capacitor 24 on the boost side of the DC / DC converter 32. Then, before driving the starter motor 44, the capacitor 24 is charged using the boosting function of the DC / DC converter 32. In the example of FIG. 4, charging is performed until the voltage value of the capacitor 24 exceeds 50V. As described above, since the voltage of the power supplied to the starter motor 44 can be arbitrarily set by using the power converter, the design of the starter motor 44 during system development is easy. Also, the starter motor 4
4, the supply voltage to the starter motor 44 can be increased.
Can be reduced in size, and the starting current to the starter motor 44 can be reduced. Further, inexpensive components (relays, wire harnesses, etc.) for the starter motor 44 can be employed.

In the present embodiment, the starter motor 4
Since the supply voltage to 4 is increased, the engine can be easily started. Even in a situation where the voltage of the auxiliary battery 20 is low, the energy remaining in the auxiliary battery 20 can be used to generate a voltage higher than the battery voltage for starting the engine by the boosting function of the DC / DC converter 32. Therefore, the engine can be reliably started even in a cold region.

Further, the present invention is not limited to the system of the present embodiment shown in FIG. 2, and the present invention is similarly applied to other systems.

Further, DC which can be suitably applied to this embodiment
The / DC converter is, for example, as follows. However, the present invention is not limited to a system to which a DC / DC converter exemplified below is applied.

A well-known flyback converter, forward converter, or other suitable converter may be applied to the DC / DC converter of the present embodiment.
With such a converter, according to the method of period,
Boost drive from the auxiliary battery side to the capacitor side is performed.

In the system of the type to which the present invention is applied, a configuration is employed in which the power from the auxiliary power storage means is boosted by the power converter to obtain the power for driving the assist motor. Therefore, power storage means for temporarily storing the motor drive power after boosting by the power converter is required. By using the motor power storage means and the power converter, the supply voltage to the starter motor can be set freely. Therefore, preferred effects such as simplification of the design of the starter motor, downsizing of the starter motor, and the like can be obtained with a simple configuration using existing components without the need for adding components or complicating the structure. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a conventional vehicle drive system with a wheel motor.

FIG. 2 is a diagram illustrating a vehicle drive system with a wheel motor according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an entire process of the system of FIG. 2;

FIG. 4 is a flowchart illustrating an engine start process of FIG. 3;

[Explanation of symbols]

10 engines, 16 front wheels, 18, 44
Starter motor, 19 alternator, 20 auxiliary battery, 22, 32 DC / DC converter, 24 capacitor, 26 wheel motor, 28 rear wheel, 34 inverter, 36 system ECU, 40,
42 voltage sensor, 46 starter switch.

Claims (1)

[Claims] 1. An engine that generates a main propulsion force of a vehicle, an assist motor that generates an assist propulsion force of a vehicle, and a step-up conversion of electric power supplied from an auxiliary power storage unit into electric power of a voltage required by the assist motor. A power converter that temporarily stores power boosted by the power converter and supplies the stored power to the assist motor. A starter motor for starting the engine, and controlling the power converter before starting the engine to convert the power supplied from the auxiliary power storage means into a voltage of a voltage required for starting the engine to convert the power supply to a voltage required for starting the engine. Starting charge control means stored in the motor storage means, and using the electric power for starting the engine stored in the motor power storage means. Vehicle drive system, characterized by starting the engine by driving the Tamota.