JP3047742B2 - 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 in which a motor is driven by a generator driven by an engine or an electric power from a mounted battery and travels, and in particular, kinetic energy of the vehicle is regenerated to the battery. The present invention relates to control during regenerative braking in which braking is performed.

[0002]

2. Description of the Related Art In recent years, the development of industrial facilities and equipment in consideration of the global environment has been actively carried out. As for automobiles, electric vehicles without exhaust gas are being developed. However, there is a problem that the capacity of a battery is not yet sufficient, and the continuous running distance is limited by this capacity. Also, it takes a long time to charge the battery,
Once discharged, there is a problem that it cannot be used immediately. Due to these problems, electric vehicles are used only for very limited applications.

In order to compensate for such a problem, a so-called hybrid electric vehicle has been developed in which a generator driven by an engine is mounted on a vehicle and the vehicle is driven by electric power generated by the generator. In this hybrid electric vehicle, the operating state of the engine can be limited to a certain area, and the hybrid electric vehicle can always be operated near the maximum efficiency point of the engine. In addition, taking measures to remove harmful components of exhaust gas in a limited operating region is more reliable and more effective than taking measures that assume various operating conditions.

[0004] An electric vehicle converts the kinetic energy of a running vehicle into electric energy by using a traveling motor as a generator to decelerate, while charging a battery with this electricity. It is possible to perform regenerative braking. As a result, the continuous running distance can be extended.

However, when regenerative braking is performed, both the power generated by regeneration and the power generated by the generator are applied between the terminals of the battery, and depending on the state of storage of the battery, the voltage between the terminals rises above the allowable voltage. May be. If an excessive voltage is applied between the terminals,
There has been a problem that the electrolyte of the battery is decomposed, gas is generated, or the battery is heated, thereby shortening the life of the battery. In order to prevent an excessive voltage from being applied between the terminals of the battery, Japanese Patent Application Laid-Open No. 4-322105 discloses that when the battery voltage rises to a predetermined value or more during regeneration, the fuel supply to the engine is cut off. A technique for stopping an engine and a generator driven by the engine is disclosed.

[0006]

However, in the electric vehicle disclosed in the above publication, it is necessary to restart the engine after the end of regenerative braking. In this restart, carbon monoxide (CO) and hydrocarbons (H
There is a problem that components such as C) tend to increase. It is also conceivable to reduce the number of revolutions of the engine and the generator by reducing the throttle valve to reduce the amount of power generation, but in this case, there is a problem that the fuel consumption rate increases. Although the hybrid electric vehicle has the advantages of reducing harmful components in exhaust gas and improving the fuel consumption rate as described above, it is preferable to reduce these advantages in order to protect the battery. Not that.

Therefore, there is a need for a technique that reduces the number of revolutions of the generator while the throttle valve is fully opened, thereby reducing the generated power. FIG. 9 shows an operation example in this case. FIG. 9 shows (a) the regenerative power, (b) the field current of the generator, (c) the number of revolutions of the generator, and (d) the generated power during braking. When the brake pedal is operated, the regenerative electric power rises immediately, and thereafter gradually decreases as the vehicle speed, that is, the rotational speed of the motor decreases. Further, in order to reduce the electric power generated by the generator, control is performed to reduce the number of revolutions of the generator. This control is performed by increasing the field current of the generator and increasing the load on the engine that drives the generator. When the number of revolutions decreases to a predetermined value, the field current of the generator is controlled such that the output of the engine and the load of the generator are balanced by this rotation. When such control is performed, the total power, which is the sum of the power by the regeneration and the power by the generator, can be reduced after the rotation speed of the generator has decreased to the predetermined rotation speed. However, when the rotation speed of the generator is decreasing, especially immediately after the brake pedal is operated, that is, immediately after the start of regeneration, since the field current of the generator increases, the power generation amount of the generator increases and the total Electricity increases on the contrary. Therefore, it does not protect the battery.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a hybrid electric vehicle which can prevent an excessive voltage from being applied between battery terminals during regenerative braking. Aim.

[0009]

In order to achieve the above object, a hybrid electric vehicle according to the present invention includes a generator driven by an engine and a battery.
A hybrid electric vehicle of a type driven by a motor driven by electric power from these, having a brake operation detector for detecting a brake operation, and an accelerator off detector for detecting an accelerator off, wherein the brake operation is performed. When the accelerator is not detected and the accelerator-off is detected, the engine control unit performs control to decrease the rotation speed of the engine and the generator by increasing the field current of the generator.

Another hybrid-type electric vehicle according to the present invention is of a type in which a vehicle is driven by a motor driven by electric power from a generator and a battery, as in the above-described hybrid electric vehicle. An accelerator-off braking control unit that performs regenerative braking control when the accelerator is turned off, and a timer that counts the elapsed time since the accelerator was turned off,
An accelerator-off braking prohibiting unit that prohibits the regenerative braking until an accelerator-off is detected.If a brake operation is not detected and an accelerator-off is detected, the engine control unit reduces the engine speed. On the other hand, the regenerative braking does not
It is controlled not to perform. The control for inhibiting regenerative braking within a predetermined time after the accelerator is turned off can also be applied to the above-described hybrid electric vehicle.

Further, another hybrid electric vehicle according to the present invention is of a type in which a vehicle is driven by a motor driven by electric power from a generator and a battery, as in the above-described hybrid electric vehicle. A brake operation, comprising: a detector and the accelerator-off detector; further comprising: a charged amount detector for detecting a charged amount of the battery; and a minimum speed setting means for determining a minimum engine speed based on the charged amount. Is not detected and the accelerator-off is detected, the engine control unit reduces the engine speed to the minimum speed. Note that the control for reducing the engine speed to the minimum engine speed based on the charged amount when the accelerator is off can also be applied to the above-described hybrid electric vehicle.

[0012]

The present invention has the above-described configuration. When the accelerator off state is detected, the engine speed is reduced to reduce the power generated by the generator, and the brake is operated to generate regenerative power. This prevents an excessive voltage from being applied between the battery terminals when this occurs.

Furthermore, by prohibiting regenerative braking equivalent to engine braking until a predetermined time elapses after the accelerator-off is detected, there is a time allowance for the engine speed to decrease, so that the time between the battery terminals is reduced. It is possible to prevent an excessive voltage from being applied.

Further, by setting the minimum rotation speed of the engine in accordance with the charged amount of the battery, when the charged amount of the battery is small, the electric power generated by the generator is increased and the charged amount is recovered at an early stage. Can be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration according to the present invention, particularly according to the present invention. The hybrid electric vehicle of this embodiment has a generator 12 driven by an engine 10 and a battery 14 for storing electric power. Electric power generated by generator 12 and battery 1
The frequency of the electric power stored in the inverter 4 is converted by the inverter 16, and the motor 18 is driven. During braking, the motor 18 functions as a generator, and the generated power is charged into the battery 14 via the inverter 16. Furthermore, these engine 10, generator 12, inverter 1
6, a control unit 20 for controlling the battery 14 and the motor 18 in accordance with the driver's operation of the brake pedal 22 and the accelerator pedal 24 and the like.

The control unit 20 controls the operation of the electric vehicle. For example, when the accelerator pedal is depressed, the rotational speed of the engine 10 is increased or the inverter 16 is controlled to control the rotational speed and torque of the motor in accordance with the amount of depression. At the time of deceleration, the inverter 16 is controlled to make the motor 18 function as a generator,
The generated power is stored in a battery.

Among the controls of the control section 20, the control according to the present invention will be described. When it is determined by the brake operation detector 26 that the brake pedal 22 has not been operated and the accelerator off detector 28 detects that the accelerator pedal 24 has been turned off, the engine control unit 30 Control to reduce the rotation speed of the motor. This decrease in the number of revolutions is caused by a predetermined change rate of the number of revolutions of the engine 10 (for example, ± 20 per second).
0 rpm). Also,
The minimum engine speed is set by the minimum engine speed setting unit 34 based on the amount of charge of the battery 14 detected by the storage amount detection unit 32. The minimum rotation speed is set high so that charging is promoted when the charged amount of the battery 14 is small, and is set low to protect the battery 14 when the charged amount is large. As described above, when the accelerator off is detected, the engine speed is reduced and the power generated by the generator is reduced, so that when the brake pedal 24 is operated, an excessive voltage is applied between the battery terminals. It is possible to charge the battery 14 with more regenerative power without using it.

When the accelerator-off is detected, the accelerator-off braking control unit 36 controls the inverter 1
6 is controlled to obtain regenerative braking corresponding to the engine brake of an automobile running directly by a conventional engine.
In the case of a conventional automobile, a certain degree of speed adjustment including deceleration can be performed only by operating an accelerator pedal by using an engine brake. However, in the case of an electric vehicle, simply stopping the power supply to the motor 18 does not generate a braking force, so that the above-described speed adjustment by the accelerator pedal, particularly the adjustment to reduce the vehicle speed, cannot be performed.
This makes it necessary to frequently perform the brake operation, which is a complicated operation for the driver. In the present embodiment, in order to avoid this, control is performed so that regenerative braking is performed by the accelerator off to perform braking corresponding to the engine braking of a conventional automobile. However, if regenerative braking is performed immediately after the accelerator is turned off, the engine 10
Regenerative power is generated before the rotation speed of the
May exceed the allowable voltage between the battery terminals depending on the state of charge (SOC) of the battery. To prevent this,
The elapsed time from the detection of the accelerator-off by the timer means 38 is measured, and the accelerator-off braking prohibiting unit 40 prohibits the accelerator-off braking until this time reaches a predetermined time. As a result, regenerative electric power is generated after the rotation speed of the engine 10 has decreased to some extent. In the case of the present embodiment, the field current of the generator is increased in order to decrease the engine speed, and in the very early stage when the engine speed is controlled to decrease, the generated power temporarily increases. there's a possibility that. As described above, in the present embodiment, regenerative braking is prohibited immediately after the accelerator is turned off, thereby preventing generation of regenerative power when the generated power temporarily increases.

FIG. 2 shows a more specific configuration of the hybrid electric vehicle of the present embodiment. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The power generation / regeneration electronic control unit 42 (hereinafter, referred to as
The electronic control unit is referred to as ECU), the engine ECU 44,
An accelerator sensor 5 for detecting the operation amounts of the motor ECU 46, the respective ECUs of the battery ECU 48, and the accelerator pedal
0, a master cylinder oil pressure sensor 52 for detecting the operation amount of the brake pedal is an element constituting the control unit 20 of FIG. 1, and an accelerator sensor 50 includes a function of the accelerator off detector 28 of FIG. Cylinder oil pressure sensor 5
2 includes a function as the brake operation detector 26 of FIG. FIG. 2 shows a configuration of a braking mechanism using mechanical friction in addition to an electrical braking mechanism using electromagnetic regeneration.

The friction braking mechanism is basically a well-known hydraulic brake. However, in order to adjust the ratio between the braking torque due to regeneration and the braking torque due to friction, differential pressure valves 54 and 5 are used.
6. The master cylinder 58 generates a hydraulic pressure according to the operation of the brake pedal 22, and this hydraulic pressure is transmitted through the front differential pressure valve 54 to the front wheel cylinder 6.
Informed to 0. A brake pad (not shown) is operated by the hydraulic pressure transmitted to the front wheel cylinder 60.
However, the front brake disc 62 is pinched, thereby generating a friction braking torque. The pressure of the front wheel cylinder 60 is detected by a front wheel cylinder oil pressure sensor 64, and the detected value is sent to the power generation / regeneration ECU 42. The hydraulic brake of the rear wheel also has a rear wheel cylinder 66,
A rear brake disk 68 and a rear wheel cylinder oil pressure sensor 70 are included. In the rear mechanism, a proportioning valve 72 is provided upstream of the differential pressure valve 56. This is a valve that adjusts the distribution of braking torque between the front and rear, and when an operation that requires strong braking torque is performed, reduces the distribution of braking torque on the rear, preventing the rear wheel from locking. Having. As described above, the front and rear brake mechanisms have almost the same mechanism. Therefore, in the following description, unless particularly necessary, the description will be made without distinguishing between the two.

The differential pressure valves 54 and 56 are specific to an electric vehicle that performs regenerative braking.
The variable valves 54a and 56a are opened and closed based on the control of 42 and guide the master cylinder oil pressure to the wheel cylinders, and the return valves 54b and 56b return the wheel cylinder oil pressure to the master cylinder. The master cylinder oil pressure changes according to the operation amount of the brake pedal 22,
By detecting this oil pressure, the power generation / regeneration ECU 4
2 detects the braking torque desired by the driver. In order to obtain the desired braking torque, the power generation / regeneration ECU 42 determines a distribution ratio between the regenerative braking torque and the friction braking torque.
Basically, the distribution ratio is determined so that the regenerative braking torque is increased as much as possible and the remainder is obtained by the friction braking torque. The power regeneration ECU 42 has variable valves 54a, 56a.
To guide the master cylinder oil pressure to the wheel cylinder until the wheel cylinder oil pressure attains the required friction braking torque. Therefore, at this time, the master cylinder oil pressure is higher than the wheel cylinder oil pressure. Thereafter, when the driver returns the brake pedal 22 and the master cylinder oil pressure starts to decrease, the wheel cylinder oil pressure cannot be decreased.
2 generates the desired braking torque by controlling the inverter 16b to reduce the regenerative braking torque. Further, when the master cylinder oil pressure decreases and becomes lower than the differential pressure set by the return valves 54b and 56b with respect to the wheel cylinder oil pressure, the wheel cylinder oil pressure decreases,
Friction braking torque is also reduced.

Further, in this embodiment, an accelerator-off braking switch 78 is provided. The accelerator-off braking switch 78 is a switch for performing control to generate braking corresponding to engine braking of a conventional automobile running by the driving force of the engine by regenerative braking. The driver can select whether or not a braking torque is applied in the accelerator-off state by operating the switch.

The operation of the apparatus of the above embodiment will be described with reference to FIG. When the power is turned on by the key switch, an initialization process is performed (S10). When the key switch is further turned to the start position, the engine 10 is started by the starter (S12). The battery ECU 48 monitors the charged amount of the battery 14 (S14), and when the charged amount is equal to or more than the upper limit, no further charging is necessary.
The number of revolutions of the engine is adjusted and reduced by the throttle (S16). If the charged amount of the battery 14 is less than the upper limit value, it is determined whether the vehicle is in a stopped state (S18). When it is determined that the vehicle is stopped, the process proceeds to step S16, and the engine speed is reduced to a predetermined speed by the throttle.

If it is determined that the vehicle is not stopped, that is, it is running, it is determined whether the brake pedal 22 is operated (S20). When the brake pedal is operated, braking is applied by regenerative braking alone or by both regenerative braking and frictional braking. Each braking torque due to this regeneration and friction is applied to the brake pedal 22.
, Ie, the hydraulic pressure of the master cylinder 58. Therefore, the regenerative electric power fluctuates every moment according to the operation amount of the brake pedal 22, and it is desirable that the electric power generated by the generator be controlled in a stable state without a large fluctuation. As described above, in order to reduce the engine speed without causing throttle loss, this can be performed by increasing the field current of the generator. Increase. For this reason, there is a possibility that an excessive voltage may be applied between the battery terminals. In order to avoid this, it is not preferable to control such that the power of the generator is greatly increased. Therefore, the engine speed at the time of braking is controlled to maintain the speed at the time when the operation of the brake pedal 22 is started or to gradually decrease the power generated by the generator within a range not exceeding a predetermined value. (S2
2).

The power generation / regeneration ECU 42 calculates the regenerative braking torque to be generated based on the value detected by the master cylinder oil pressure sensor 52 and conditions such as motor rating, battery voltage, inverter temperature and the like (S24). Next, in order to generate a braking torque corresponding to the difference between the calculated regenerative braking torque and the required braking torque, control command values for the differential pressure valves 54 and 56 are calculated (S26). The differential pressure valve is driven based on this command value (S28).

As described above, since the wheel cylinder oil pressure cannot be reduced by the differential pressure valves 54 and 56, if the wheel cylinder oil pressure is already higher than the control value, the regenerative braking torque must be adjusted. As a result, a desired braking torque is obtained. For this purpose, the regenerative braking torque is adjusted so that the regenerative braking torque corresponds to the difference between the current friction braking torque and the required braking torque (S3).
0). As described above, the inverter 16b is controlled based on the calculated regenerative braking torque control value (S32). And
The generator / engine is controlled based on the calculated engine speed (S33).

Next, when it is determined in step S20 that the brake pedal 22 has not been operated,
Subsequently, it is determined whether or not the accelerator pedal 24 has been operated (S34). When the accelerator pedal 24 is operated, it means that the driver wants acceleration or almost steady running, in other words, it does not want to actively control the braking. In this case, the drive of the motor 18 is controlled by electric power generated by the generator 12 or electric power from the battery 14. The rotation speeds of the generator and the engine are calculated based on the state of charge (SOC) of the battery 14 detected by the battery ECU 48 and the power output to the motor (S3).
6). Then, the process proceeds to step S33, where the drive control of the engine and the generator is performed based on the calculated engine speed.

On the other hand, in step S34, when it is determined that the accelerator pedal 22 is not operated, the engine minimum rotation speed N _min in accordance with the SOC of the battery 14 detected by the battery ECU48 is calculated (S3
8). The minimum engine speed is calculated based on, for example, a graph shown in FIG. FIG. 4 shows that when the SOC is high (70% or more), the charged amount is relatively large and the allowable voltage between the battery terminals is low, so the engine minimum rotation speed _Nmin is set low (1200 rpm) and the SOC is low (50 rpm). %) case, it is necessary to recover the power storage amount in the allowable voltage higher early across the battery terminals, indicating that N _min is higher (2000 rpm) set.
By performing such control, the battery is protected when the allowable voltage between the battery terminals is low, and when the battery needs to be charged, the battery is sufficiently charged.

[0030] When the engine minimum rotation speed N _min is calculated, whether the current engine rotational speed N _i is a _{N mi n (N i = N} min) is determined (S40). When the current engine speed is equal to the minimum engine speed, the engine speed command value is maintained at the engine minimum engine speed N _min (S
42). Further, if the current engine speed and the lowest rotational speed unequal, predetermined rotational speed than the previous rotational speed N _i-1 ΔN
A low command value _Ni is newly calculated (S44). The predetermined rotation speed ΔN defines the speed at which the rotation speeds of the engine and the generator decrease. This decreasing speed is set in advance to a speed that satisfies the allowable values of the component change of the exhaust gas and the fuel consumption.

Next, it is determined whether the accelerator-off braking switch 78 is on (S46). If the accelerator-off braking switch 78 is in the off state, the process proceeds to step S33, and the driving control of the generator and the engine is performed based on the engine speed. Accelerator off brake switch 7
8 If on state, compared with the current generator power and the power generation allowable power G _OD is made (S48). The power generation allowable power G _OD is a value obtained by subtracting the regenerative power generated by the braking equivalent to the engine brake from the allowable power applied to the battery, and decreases as the rotation speed of the motor increases, as shown in FIG. . This is because the power generated by regenerative braking equivalent to engine braking is approximately proportional to the motor speed, and indicates that when the motor speed is high, the power generated by the generator must be reduced. The allowable power of the battery 14 is SOC
, And are sequentially calculated by the battery ECU 48.

When the current generated power is equal to or more than the allowable generation power G _OD , an excessive voltage is applied between the battery terminals. When the generated power is less than _{GOD, since} the power equal to or _larger than the allowable value is not supplied to the battery, the regenerative braking torque for accelerator-off braking is calculated (S50). On the other hand, if the generated power is equal to or more than _GOD , it is determined whether a predetermined time has elapsed since the accelerator is turned off and the accelerator-off braking switch is turned on (S52). If the predetermined time has elapsed, the process proceeds to step S50, and the regenerative braking torque due to the accelerator-off braking is calculated. If the predetermined time has not elapsed in step S52, the process proceeds to step S33 without performing the accelerator-off braking, and the generator / engine drive control is performed based on the above command values. As described above, when there is a possibility that an excessive voltage may be applied to the battery 14 due to the generated power and the regenerative power of the generator, the accelerator-off braking is prohibited and prevented during a predetermined time period. Since the rotation speed of the generator gradually decreases due to the operation of step S44 and the like during the elapse of the predetermined time, the power generated by the generator decreases after the elapse of the predetermined time. Therefore, even if both the electric power from the generator and the regenerative electric power are supplied to the battery, it is possible to prevent the electric power from greatly exceeding the battery allowable electric power. In other words, such a predetermined time is set in advance.

As described above, drive control is performed based on the number of revolutions of the engine / generator calculated according to the operation of the accelerator pedal, the operation of the brake pedal, and the like. If the key switch is ON (S54), the process proceeds to step S14 and the above-described control flow is repeated. If the key switch is off (S54), the termination process (S56) is executed and the process ends.

Each output value when the above control is performed is shown in FIG.
Is shown in At the time when the accelerator is turned off, the field current of the generator increases and the number of revolutions of the engine / generator decreases. When a predetermined time has elapsed since the accelerator was turned off, regenerative braking equivalent to engine braking is started, and regenerative electric power rises. The power generated by the generator temporarily increases, but gradually decreases, as in the case of FIG. Since the rotation speed of the generator is fixed at the time when the brake operation is performed, the field current of the generator decreases, and the generated power also decreases. In addition, the regenerative braking torque is required more by the brake operation, and the regenerative electric power is further increased. In the above control, after a lapse of a predetermined time during which the accelerator-off braking is prohibited and when the brake operation is performed, the generated power of the generator is clearly smaller than the generated power at the time of the accelerator-off. A situation where an excessive voltage is applied can be prevented or reduced.

FIG. 7 shows the configuration of another embodiment according to the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. The characteristic feature of the present embodiment is that a so-called antilock brake system is used for the hydraulic system of the friction brake. The master cylinder hydraulic pressure generated by operating the brake pedal 22 is applied to the front and rear pressure-intensifying solenoid valves 1
By means of 00 and 102, the required amount is guided to the wheel cylinders 60 and 66. The wheel cylinder 60,
If it is necessary to reduce the oil pressure at 66, open the front and rear pressure reducing solenoid valves 104 and 106,
It leads to the reserve tank 108. The hydraulic oil guided to the reserve tank 108 is returned to the hydraulic oil tank 116 by the hydraulic pump 110 via the check valve 112 and the switching valve 114. The switching valve 114 switches between returning hydraulic oil from the hydraulic pump 110 to the master cylinder 58 and returning to the hydraulic oil tank 116. At the time of the antilock brake differential, the hydraulic oil is returned to the master cylinder 58 in order to secure the oil pressure in the master cylinder. In other cases, each solenoid valve does not operate to the extent that the amount of hydraulic oil in the master cylinder 58 runs short, so the hydraulic oil is returned to the hydraulic oil tank 116 and is supplied to the master cylinder 58 when the brake pedal 22 is operated. .

In the case of the present embodiment, unlike the above-described embodiment, it is possible to reduce the once raised wheel cylinder oil pressure to adjust it to a desired pressure. In the case of the above embodiment,
Once the oil pressure of the wheel cylinder has increased, the pressure is not reduced unless the difference between the oil pressure and the master cylinder oil pressure becomes lower than a predetermined oil pressure determined by the setting of the return valve 54b. Therefore, the adjustment of the total braking torque after the wheel cylinder oil pressure is increased is performed by adjusting the regenerative braking torque. Therefore, the regenerative braking torque is reduced to reduce the total braking torque. on the other hand,
In this embodiment, while the regenerative braking torque maintains the maximum value, the wheel cylinder oil pressure is reduced by the pressure reducing solenoid valve 1.
By controlling the pressure reduction in steps 04 and 106, the friction braking torque is reduced to control the total braking torque. Therefore, kinetic energy can be regenerated as electric power. The control of the pressure increasing and pressure reducing solenoid valves 100, 102, 104, 106 is performed by the power generation / regeneration ECU 42 based on the detection value of the master cylinder oil pressure sensor 52 and information of each control ECU.

FIG. 8 shows a control flow of the apparatus shown in FIG. In this control flow, the same steps as those in the control flow shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. If it is determined in step S20 that the brake operation has been performed, the engine speed during braking is calculated in the same manner as in the above-described embodiment (S22). And
Regardless of the wheel cylinder oil pressure, a command value of the maximum regenerative braking torque that can be generated according to the motor rotation speed at that time is calculated (S124). Then, the pressure-increasing / reducing solenoid valves 100, 10 are provided so that a braking torque of a difference between a desired braking torque indicated by the master cylinder oil pressure and the regenerative braking torque is obtained by the friction braking torque.
The control command values are calculated for 2, 104 and 106 (S12).
6). Based on this control value, the pressure increasing / decreasing solenoid valve is controlled.

In the present embodiment, the control different from that of the above-described embodiment is performed in the case where the accelerator-off braking is performed.
The regenerative power is calculated so that the sum of the generator power and the regenerative power generated when the accelerator is off does not exceed the allowable power of the battery (S150), and the pressure increasing / reducing solenoid valve is operated so that the insufficient braking torque is compensated by friction braking. Is calculated (S226). Based on the above command value, the pressure increasing / decreasing solenoid valve is controlled (S128),
The hydraulic pressure in the wheel cylinder is adjusted.

In this embodiment, the regenerative power is controlled so as not to exceed the battery allowable power at the time of accelerator-off braking, so that an excessive voltage is prevented from being applied between the battery terminals at this time. Further, immediately after the accelerator-off is detected, a braking torque equivalent to the engine brake (accelerator-off braking) can be generated immediately, so that an operational feeling similar to that of a conventional automobile driven by an engine can be obtained. As described above, in each of the above-described embodiments, even when the control for decreasing the rotation speed of the generator during braking is performed not by the throttle valve of the engine but by the field current of the generator, an excessive voltage is applied between the battery terminals. Voltage can be prevented from being applied. In other words, when the accelerator is turned off, by starting to reduce the rotation speed of the generator in advance, when the brake operation is performed and the power due to the regenerative braking is generated, the power generated by the generator should be reduced. Thereby, the above-described operation is achieved.

(Supplementary note) The hybrid electric vehicle according to claim 1, wherein when an accelerator off is detected by the accelerator off detector, an accelerator off braking control unit that performs regenerative braking equivalent to engine braking, and an engine brake. Regenerative power calculating means for calculating regenerative power when a considerable amount of braking is performed; allowable power calculating means for calculating allowable power that is an allowable value of power supplied to the battery; and the allowable power and the regenerative power. A permissible generated power calculating unit that calculates permissible generated power that is a permissible value of the power generated by the generator; a time measuring unit that measures an elapsed time since the accelerator-off is detected; and If the generated power is equal to or more than the permissible generated power and the predetermined time has not elapsed by the timing means, the regenerative braking equivalent to the engine brake is prohibited. Hybrid electric vehicle comprising: the Seruofu braking prohibition unit.

[0041]

As described above, according to the present invention, when the accelerator off state is detected, the engine speed is reduced to reduce the power generated by the generator, and the brake is operated to generate regenerative power. In this case, it is possible to prevent an excessive voltage from being applied between the battery terminals.

Further, by prohibiting regenerative braking equivalent to engine braking until a predetermined time elapses after the accelerator-off is detected, it is possible to provide a time margin in which the rotation speeds of the engine and the generator are reduced. It is possible to prevent an excessive voltage from being applied between the terminals.

Further, by setting the minimum engine speed in accordance with the charged amount of the battery, when the charged amount of the battery is small, the electric power generated by the generator is increased and the charged amount is recovered at an early stage. Can be.

As described above, by preventing an excessive voltage from being applied between the battery terminals, it is possible to extend the life of the battery. Further, since the amount of power generation can be controlled without stopping the engine, it is not necessary to restart the engine, and the amount of carbon monoxide and hydrocarbons contained in the exhaust gas can be reduced. Also, since the engine speed control can be performed with the throttle fully open,
Operation at a better fuel consumption rate becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a configuration of the present invention.

FIG. 2 is a configuration diagram of an embodiment according to the present invention, particularly showing a configuration relating to a braking mechanism.

FIG. 3 is a control flowchart of the apparatus of the embodiment of FIG. 2;

FIG. 4 is a diagram showing the relationship between the state of charge of a battery and the minimum engine speed when an accelerator is turned off.

FIG. 5 is a diagram showing a relationship between the number of rotations of a motor and an allowable upper limit of electric power generated by a generator.

FIG. 6 is an example of a time chart showing control values and generated power when the device of the present embodiment is operated.

FIG. 7 is a configuration diagram of another embodiment according to the present invention, particularly showing a configuration relating to a braking mechanism.

FIG. 8 is a control flowchart of the apparatus of the embodiment of FIG. 7;

FIG. 9 is an example of a time chart showing control values and generated power when the generator rotation speed is reduced at the same time as the start of the brake operation.

[Description of Signs] 10 Engine 12 Generator 14 Battery 16 Inverter 18 Motor 20 Control Unit 22 Brake Pedal 24 Accelerator 42 Power Generation / Regeneration ECU 44 Engine ECU 46 Motor ECU 48 Battery ECU 50 Accelerator Sensor 52 Master Cylinder Oil Pressure Sensor 52 54 Front Differential pressure valve 56 Rear differential pressure valve 58 Master cylinder 60 Front wheel cylinder 62 Front brake disc 66 Rear wheel cylinder 68 Rear wheel cylinder 74 Accelerator off brake switch 100 Front booster valve 102 Rear booster valve 104 Front booster valve 106 Rear booster Pressure valve

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60L 11/00-11/14 B60L 7/14 H02P 9/04 H02P 15/00

Claims (5)

(57) [Claims] 1. A generator mounted with an engine and a battery, and a field current of the generator is adjusted.
Control the engine and generator speeds
The driving of the electric power from the generator or the battery
In a hybrid electric vehicle that is driven by a motor and that is capable of regenerative braking during braking, a brake operation detector that detects a brake operation, an accelerator off detector that detects an accelerator off, and a brake operation detected by the brake operation detector If the accelerator off is detected by the accelerator off detector, the field current of the generator is increased.
A hybrid-type electric vehicle comprising: an engine control unit that performs control to reduce the number of revolutions of the engine and the generator by controlling the rotation speed of the engine and the generator . 2. A generator, which is driven by an engine, and a battery, and power from the generator or the battery is provided.
A hybrid electric vehicle that travels with a motor driven by the motor and that is capable of regenerative braking during braking, a brake operation detector that detects a brake operation, an accelerator off detector that detects an accelerator off, and a brake by the brake operation detector When no operation is detected and the accelerator off is detected by the accelerator off detector, an engine control unit that performs control to reduce the engine speed, and an accelerator off is detected by the accelerator off detector An accelerator-off braking control unit that performs regenerative braking equivalent to an engine brake; a timer that counts an elapsed time since the accelerator-off is detected; and the engine brake until the predetermined time is detected by the timer. An accelerator-off braking prohibition section that prohibits considerable regenerative braking; A hybrid electric vehicle. 3. An electric generator driven by an engine and a battery, and electric power from the electric generator or the battery.
A hybrid electric vehicle that travels with a motor driven by the motor and that is capable of regenerative braking during braking, a brake operation detector that detects a brake operation, an accelerator off detector that detects an accelerator off, and a brake by the brake operation detector When no operation is detected and the accelerator-off detector detects accelerator-off, an engine control unit that performs control to reduce the engine speed, and a charged-amount detector that detects the charged amount of the battery And minimum rotation speed setting means for determining a minimum rotation speed of the engine based on the detected amount of stored power, wherein the engine control unit reduces the engine rotation to the minimum rotation speed. Hybrid electric vehicle. 4. The hybrid electric vehicle according to claim 1, wherein when the accelerator-off detector detects the accelerator-off, an accelerator-off braking control unit that performs regenerative braking equivalent to engine braking; A timer means for measuring an elapsed time since the detection, and an accelerator-off braking prohibiting unit for prohibiting regenerative braking equivalent to the engine brake until a predetermined time period is detected by the clocking means. Hybrid electric vehicle. 5. The hybrid electric vehicle according to claim 1, wherein the charged amount detector detects a charged amount of the battery, and a minimum rotation speed of an engine based on the detected charged amount. A hybrid electric vehicle, comprising: a minimum rotation speed setting means for determining the rotation speed of the vehicle, wherein the engine control unit reduces the engine rotation speed to the minimum rotation speed.