JP2000316204A - Regenerative brake system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the regenerating rate of braking energy to a battery by providing a control circuit which increases a regenerated current when the operation level of a service brake is high. SOLUTION: The pressure by a braking pedal 22 is detected by means of a brake sensor 18 and supplied to a control circuit 5. The circuit 5 simultaneously sets an electrical braking state when the pedal 22 is stepped down and charges a battery 3 by supplying a regenerated current caused by the electrical braking to the battery 3 before mechanical braking acts. Since the regenerated energy, namely, the regenerated current generated by the electrical braking is largely controlled as the pressure applied to the pedal 22 becomes higher, the electrical braking becomes effective when a driver lightly steps on the pedal 22 and, accordingly, the energy diffused by the frictional heat generated between a brake shoe and a brake drum becomes smaller. Therefore, the regenerated guantity of the energy generated by the braking to the battery 3 can be maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is applied to an electric vehicle or a hybrid vehicle. The present invention relates to an improvement for efficiently regenerating electric energy generated by electric braking to a battery mounted on a vehicle. The present invention relates to a technique for controlling a regenerative current in accordance with an operation level of a service brake operated by a driver while traveling.

The present invention relates to an electric braking device manufactured and sold by the applicant under the name of HIMR and suitable for a hybrid vehicle for a bus or a truck disclosed in International Publication No. WO 88/06107 (International Application No. PCT / JP88 / 00157). However, the invention can be widely used not only for large vehicles but also for electric vehicles or hybrid vehicles that use electric braking together with service braking by operating a brake pedal.

[0003]

2. Description of the Related Art The hybrid vehicle disclosed in the above-mentioned international publication is briefly described as shown in FIG. 1 (the hardware configuration is the same for both the conventional device and the device of the present invention). A motor generator 2 composed of a squirrel-cage induction machine whose rotor is directly connected to a crankshaft of an internal combustion engine 1, a battery 3, and an inverter circuit 4 provided between the battery 3 and the motor generator 2 And The inverter circuit 4 transmits energy from the battery 3 to the motor generator 2 when the motor generator 2 operates as a motor for auxiliary acceleration, and the motor generator when the motor generator 2 operates as a generator for performing electric braking. 2 operates to regenerate the electric energy generated in the battery 2 to the battery 3. The operation of the inverter circuit 4 is computer-controlled by a control program set in the control circuit 5.

At the time of electric braking, the electric energy generated by the motor generator 2 is consumed by the resistor 11 through the semiconductor switch circuit 12 so that the vehicle can be effectively decelerated by electric braking. The generated electric energy is consumed by the resistor 11. In order to effectively use the energy, it is desirable to regenerate as much of the electric energy generated by the electric braking as possible into the battery 3.

For this reason, the applicant has disclosed in Japanese Patent Application Laid-Open No. 8-237805.
Discloses the control technology. This control technique will be briefly described with reference to FIG. 1. The operation of an accelerator pedal 21 and a brake pedal is supplied to a control circuit 5, and when the accelerator pedal 21 is released by a driving operation during traveling, that is, when the engine Control for automatically controlling the regenerative current supplied from the motor generator 2 to the battery 3 according to the transmission gear ratio set at the time of the brake state, in accordance with the currently set transmission gear ratio. It has a program. And, in such a control program, when the driver performs an operation such as depressing a brake pedal or an accelerator pedal in such a control state, it is assumed that the state of the engine brake is released by the driving operation, The control operation for increasing the regenerative current is released.

[0006]

The inventor of the present invention has repeatedly conducted tests on this conventional apparatus. Then, an attempt was made to improve the regenerative current even more when the accelerator pedal is released by driving operation during traveling and the vehicle enters a so-called engine / brake state so that energy can be effectively regenerated. When the driver depresses the brake pedal after the driver releases the accelerator pedal, the engine is still in the state of engine braking until the vehicle speed reaches the speed determined according to the set gear ratio. Therefore, at this time, I realized that it was possible to improve the control operation so that the regenerative current could be increased without releasing it, so I studied the regenerative current control with the brake pedal being depressed, and tested it. Was repeated.

The present invention has been made under such a background, and has as its object to regenerate as much electric energy generated by electric braking as possible into a battery. An object of the present invention is to provide an electric braking device that controls a regenerative current to be as large as possible even when a brake pedal is depressed, that is, when a service brake is being operated. I do.

[0008]

Means for Solving the Problems The operation of the service brake, that is, the operation of the brake pedal is based on the driving operation based on the driver's intention, and the strong depression of the brake pedal causes the driver to apply a strong braking force. That is what we are trying to generate. At this time, the kinetic energy of the traveling vehicle is dissipated by the mechanical frictional heat. At this time, if the sharing by the mechanical frictional heat is reduced and this is shared by electric braking, this is effectively regenerated as electric energy. can do.

That is, the present invention provides an electric braking means (2,
4, reference numerals represent the reference numerals in the embodiment reference drawings, the same applies hereinafter), a battery (3), and a control circuit (5) for controlling a regenerative current to the battery generated by the electric braking means during braking.
In the regenerative braking device provided with the above, a sensor means (18) for detecting the operation level of the service brake is provided, and the control circuit (5) is adapted to detect when the operation level of the service brake is high according to the output of the sensor means And means for controlling the regenerative current to be increased.

The means for detecting the operation level of the service brake is, for example, a pressure sensor for detecting the pressure of a pressure cylinder linked to a brake pedal. This pressure can be detected directly or indirectly. That is, the pressure may be the pressure of a pressure cylinder or the output pressure of a booster driven by the pressure of the pressure cylinder. Further, a stroke sensor of a brake pedal may be used.

The fact that the brake pedal is depressed strongly means that the driver needs a large braking force. At this time, the electric braking is increased according to the braking pressure generated by the brake pedal. Control is performed to generate a large regenerative current. That is, energy consumed by mechanical brake friction is converted into electric energy and regenerated. The driver feels that the brakes work well even if the brakes are lightly depressed. Since the brake is applied well, the brake pedal is not strongly depressed, and the energy dissipation due to frictional heat is reduced by that amount, and this is regenerated to the battery as electric energy.

The degree to which the electric brake is effective when the brake pedal is depressed and the degree to which the battery is regenerated are determined by the control function f in the program control circuit (5).
, An optimum state can be realized. That is, in the control circuit, when the detected pressure of the pressure cylinder is p and the regenerative current to the battery is i, a function control circuit for controlling i = f (p) is set by software. Since this control function can be set arbitrarily so as to be optimal for the hardware, it can be set so that the regenerative current is maximized. In other words, it is possible to create a program for optimally apportioning the sharing ratio between mechanical braking that dissipates energy by frictional heat when the brake pedal is depressed and electric braking that regenerates energy in the battery.

[0013] This control function f, when an n-stage transmission is interposed between the generator included in the electric braking means and the axle,
.. fn such that f1, f2,... fn are provided in the table in advance, and one of them is selected according to the gear ratio set as hardware in the transmission at that time. Can be. The gear ratio can be detected by a sensor from the transmission or from the ratio of the vehicle speed to the engine speed.

The function f is not necessarily required to be continuous, but may be a stepwise function. That is, instead of continuously changing the regenerative current according to the change in the pressure of the brake pedal, it is possible to control the regenerative current to change stepwise in accordance with the change in the pressure of the brake pedal. The stepwise configuration simplifies the configuration of the program.

Further, the function f can be set by adding an element of the speed at the time of braking, that is, the vehicle speed at the time of braking (or the rotation speed of the engine or the motor generator) as a parameter. Since the energy generated by braking is proportional to the square of the vehicle speed, when the vehicle speed is high, the share of electric braking can be set to be greater than the share of mechanical braking caused by mechanical friction.
Thereby, more effective energy regeneration can be performed.

Further, an element of the vehicle mass can be added to the function f. Particularly, in the case of a large vehicle, the mass of the vehicle greatly changes depending on the size of the loaded cargo or the number of appearing personnel. Since the braking energy is proportional to the vehicle mass, when the vehicle mass is large, the share of the electric braking can be set to be larger than the share of the mechanical braking. Since a technique of detecting a vehicle mass by providing a sensor on a suspension of a vehicle body is known, this can be used. Further, the vehicle mass may be configured so that the driver inputs an approximate value by operation.

Further, a battery element that receives regenerative energy can be added to this function f. As a control factor, it is possible to take into account how much the battery charging rate has at each time. If the battery is in a sufficiently charged state, it can be controlled to increase the share of mechanical braking, and if the battery has room to accept further charging, it can be controlled to increase the share of electric braking. There is known a method of detecting the state of charge of a battery by directly or indirectly measuring its internal resistance at the timing of discharging current from the battery. Besides that,
Since methods for easily observing the charged capacity from the measured value of the battery terminal voltage are known, the function f is calculated using these methods.
This can be reflected in

[0018]

FIG. 1 is a hardware configuration diagram of an apparatus according to an embodiment of the present invention. In this device, a rotating shaft of a motor generator 2 is directly connected to a crankshaft of an internal combustion engine 1. The motor generator 2 is constituted by a squirrel-cage induction machine. When the motor generator 2 is driven by supplying a three-phase alternating current that gives a rotating magnetic field having a rotation speed greater than the rotation speed of the rotating shaft to the field winding, the motor generator operates as a motor, When a three-phase alternating current that supplies a rotating magnetic field having a rotation speed smaller than the rotation speed of the rotating shaft to the magnetic winding is supplied, mechanical energy applied to the rotating shaft is converted into electric energy, which is converted into a three-phase alternating current to generate a magnetic field. Can be taken out of the winding. The alternating current supplied to the motor generator 2 is
The direct current supplied from the battery 3 is obtained by conversion by the inverter circuit 4. The three-phase alternating current generated when the motor generator 2 operates as a generator is also converted into a direct current by the inverter circuit 4 and is regenerated so as to charge the battery 3. Frequency on the AC side of the inverter circuit 4,
That is, the rotation speed of the rotating magnetic field of the motor generator 2 is controlled by a control circuit 5 that takes in the output of a rotation sensor 6 that detects the rotation speed of the rotating shaft of the internal combustion engine 1, that is, the motor generator 2, and controls the inverter circuit 4. You.

That is, when the motor generator 2 is operated as an electric motor to perform the auxiliary acceleration, the control circuit 5 takes in the output of the accelerator sensor 17 linked to the accelerator pedal 21 and is slightly lower than the rotation speed detected by the rotation sensor 6. The inverter circuit 4 generates a rotating magnetic field (positive slip ratio 0 to several percent) that is large in the field winding of the motor generator 2.
Control. At this time, energy is supplied from the battery 3 to the motor generator 2. When the motor generator 2 is operated as a generator to perform electric braking, the control circuit 5
The inverter circuit 4 is controlled so that a rotating magnetic field slightly smaller than the detected rotational speed (negative, that is, a rate of 0 to several percent) is generated in the field winding of the motor generator 2. At this time, energy is supplied from the motor generator 2 to the battery 3, or is consumed by the resistor 11 via the semiconductor switch circuit 12. At this time, the terminal voltage of the battery 3 is observed by the detection circuit 13, and if the battery 3 has a margin for charging, the switch control circuit 14 sets the semiconductor switch circuit 12 to the non-conductive state, and the current charges the battery 3. Flows. If the battery 3 has already been sufficiently charged and there is no room for charging, the switch control circuit 14 makes the semiconductor switch circuit 12 conductive, and the electric energy generated by braking in the motor generator 2 is dissipated by the resistor 11.

The vehicle speed sensor 16 is a sensor for detecting wheel rotation or rotation on the transmission output side, and is used by the control circuit 5 to know which gear the transmission is currently set to. The standard terminal voltage of the battery 3 is, for example, 300 V
Since this is inconvenient for use in the electric equipment in the vehicle, it is converted to 24 V by the DC / DC converter 19 and supplied to the vehicle. The configuration and operation of the device, the control circuit 5 and the inverter circuit 4 disclosed in FIG. 1 are already well-known, and are described in the above-mentioned international publication, so that detailed description is omitted here.

The feature of the present invention is that the brake pedal 2
2, that is, the pressure generated by the brake pedal 22 is detected by the brake sensor 18, is taken into the control circuit 5, and is used for controlling the regenerative current supplied from the motor generator 2 to the battery 3. is there. FIG. 2 shows a more specific configuration example of the brake sensor 18. That is, the air pressure from the brake pressure source is
The pressure is regulated by a brake valve 24 controlled by the brake control 2 and is supplied from two boosters 25 and 26 to a front wheel brake and a rear wheel brake, respectively. The pressure on the booster input side of the front wheel brake is detected by a brake sensor 18 and supplied to the control circuit 5.

FIG. 3 is a time chart for explaining the operation of the embodiment of the present invention. The horizontal axis indicates time, and the vertical axis indicates the change with time of the displacement of the accelerator pedal, the pressure generated by the brake pedal, and the braking energy. That is, an example of an operation in which the accelerator pedal is released from the on state to the off state during the driving, and then the brake pedal is depressed, and the accelerator pedal is gradually depressed from the off state. The brake pressure generated by the brake pedal is the output of the brake sensor 18.
At this time, the control circuit 5 of the embodiment of the present invention sets the electric braking state while the brake pedal is depressed, and supplies the regenerative current by the electric braking to the battery 3 before the mechanical braking is applied. When the brake pressure generated by the brake pedal gradually increases, the electric braking is gradually increased, and the electric braking shares most of the braking energy, and the battery 3 is operated to regenerate the generated energy.

The present invention is characterized in that the regenerative energy by electric braking, that is, the regenerative current is controlled so as to increase as the brake pedal pressure increases in accordance with the brake pedal pressure. By this operation, the electric braking is effective only by lightly depressing the brake pedal by the driver, and the energy dissipated by the frictional heat generated between the brake shoe and the brake drum is reduced.

FIG. 4 is a flowchart showing a main part of a control program set in the control circuit 5 of the apparatus according to the embodiment of the present invention.
When the accelerator pedal is released, the characteristic control of the present invention is started. If the vehicle speed is equal to or higher than the predetermined value (v0), the transmission gear ratio is taken in, the function f is selected and set according to the gear ratio, and the brake pressure p is monitored. When the brake pressure p exceeds a predetermined value, i = f (p) is calculated, and the regenerative current is controlled so as to be equal to the current value i. That is, by controlling the rotating magnetic field of the field winding of the motor generator 2, a current generated from the motor generator 2 and regenerated into the battery 3 via the inverter circuit 4 is added to the calculated current value i. Control to be equal. At this time, the terminal voltage of the battery 3 is observed, and if charging is possible, this control step is repeated.

[0025]

According to the above operation, the ratio of the braking energy that is effectively regenerated to the battery is significantly improved.
The function f can be selected and designed so as to best suit the performance of the hardware, and the energy generated by braking can be regenerated to the maximum extent in the battery.

[Brief description of the drawings]

FIG. 1 is a hardware configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a brake sensor of the device according to the embodiment of the present invention.

FIG. 3 is a time chart for explaining a control state of the apparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a main part control procedure of the apparatus according to the embodiment of the present invention.

[Description of Signs] 1 Internal combustion engine 2 Motor generator 3 Battery 4 Inverter circuit 5 Control circuit 6 Rotation sensor 7 Capacitor 11 Resistor 12 Semiconductor switch circuit 13 Detection circuit 14 Switch control circuit 16 Vehicle speed sensor 15 Current detector 17 Accelerator sensor 18 Brake sensor 19 DC / DC converter 21 Accelerator pedal 22 Brake pedal 24 Brake valve 25, 26 Booster

Claims (5)

[Claims] 1. A regenerative braking device comprising an electric braking means, a battery, and a control circuit for controlling a regenerative current to the battery generated when the electric braking means brakes, wherein an operation level of a service brake is detected. A regenerative braking device comprising: a sensor unit; and a control circuit for controlling the control circuit to increase the regenerative current when the operation level of the service brake is high according to an output of the sensor unit. . 2. The regenerative braking device according to claim 1, wherein said sensor means is a pressure sensor for detecting (directly or indirectly) the pressure of a pressure cylinder linked to a brake pedal. 3. A regenerative braking device according to claim 2, wherein said sensor means is a stroke sensor of a brake pedal. 4. The control means includes a function control circuit for controlling so that i = f (p) when the detected pressure of the pressure cylinder is p and the regenerative current is i. Regenerative braking device. 5. When an n-stage transmission is interposed between a generator included in the electric braking means and an axle, a plurality of n functions f1, f2,... Fn are preset as the function f. 5. The regenerative braking device according to claim 4, wherein said controlling means includes means for selecting one of the n functions in accordance with a speed ratio set at said transmission.