JPS59123403A - Brake device for electric motor car - Google Patents

Abstract

PURPOSE:To obtain smooth brake force with respect to a brake command value by altering the operating conditions of electric brake means with respect to a brake command in response to the braking conditions of the brake force of the brake means. CONSTITUTION:Electric power from a battery 1 is supplied to an induction motor 3 through an inverter 2. A brake instruction unit 4 generates a command value by the operation of an operator and is used to obtain mechanical brake force. A temperature detector 5 detects the temperature of the motor 3. The maximum brake force calculator 6 calculates the maximum brake force on the basis of the output of the detector 5 and applies it to a multiplier 7. The multiplier 7 multiplies the command value as the output of the unit 4 by the maximum brake force as the output of the calculator 6 and delivers a brake force reference value T* to an inverter control circuit.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electric vehicle braking device, and particularly to an electric vehicle suitable for smoothly braking an electric vehicle by using both electrical braking and mechanical braking. Regarding a braking device.

[Technical background of the invention]

2. Description of the Related Art In recent years, electric vehicles that run by driving an electric motor using batteries as an energy source have come to be widely used for indoor driving and short distance driving because of their low pollution and low noise. This type of electric vehicle is generally constructed in such a way that the electric energy of the battery is converted into a force using a conversion device such as a chopper or an inverter, and then a DC motor or an AC motor is driven to obtain a predetermined driving force or braking force. Ru. Generally, the electric motor is driven by energy from the battery during acceleration and normal driving, while braking energy is regenerated into the battery or consumed by a resistor when decelerating or descending a slope. taken.

Here, the electrical driving force and braking force are determined by the capacity of the electric motor and power converter, but the maximum driving torque and the maximum braking torque when the electric motor is rotating at a certain rotation speed are generally almost the same. You can think that.

On the other hand, in terms of performance as an electric vehicle, acceleration torque is determined by the capacity of the electric motor and power converter, but on the other hand, a large braking force is required for safety reasons, even when driving.

For this reason, a mechanical braking mechanism is generally used in combination to obtain a mechanical braking force in addition to the electrical braking force. Incidentally, a configuration in which electrical braking energy during braking is regenerated into a battery can be said to be more advantageous than a system in which the electrical braking energy is consumed by a resistor from the viewpoint of effective energy utilization.

From the viewpoint of characteristics as described above, the relationship between the braking command value corresponding to the amount of depression of the brake pedal of an electric vehicle and the braking force/braking torque is determined by the predetermined braking command value as shown in the characteristic diagram of Fig. 1. It is preferable to use a system in which electrical braking is applied up to a command value, and both electrical braking and mechanical braking are operated for a command value higher than that.

[Problems with background technology]

Continue driving an electric car with a braking mechanism as described above,
For example, assume that the temperature of the electric motor rises above a predetermined level. In such a state, it is generally necessary to limit the maximum value of current supplied to the motor in order to protect the insulation of the windings of the motor, thereby limiting the temperature rise. As a result, the maximum value of the braking current during electrical braking is also smaller than the value at normal motor temperature. Therefore, if control is performed to simply reduce the maximum value of the braking force when the electric motor becomes high in temperature, the relationship between the braking command value and the braking force will be as shown in the characteristic diagram of FIG. In this case, a problem arises in that the braking force does not change with respect to changes in the braking command value from point A to point B. By the way, the braking command value is generally changed by the operator operating the brake pedal or steering wheel, but in the case described above, there is a dead zone with respect to the amount of operation, making it impossible to perform smooth braking operations.) It will be dangerous.

[Purpose of the invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to make it possible to obtain a smooth braking force in response to a braking command value when braking an electric vehicle using both electrical braking and mechanical braking functions. To provide a brake system for electric vehicles.

[Summary of the invention]

In order to achieve the above object, the present invention provides an electric motor that receives power supply from a power source via a power converter and drives an electric vehicle, and regenerates regenerated power from the electric motor to the power source via the power converter. An electric braking means that obtains braking force, a mechanical braking means that mechanically applies braking force to the electric vehicle, and a braking command that commands the braking force is output and the mechanical braking means directly performs a braking operation. Electric vehicle braking comprising a command means, a limit detection means for detecting a limit condition of the braking force of the electric braking means, and a calculation means for changing the operating condition of the electric braking means in response to a braking command according to the output of the limit detecting means. It provides equipment.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the front page.

FIG. 3 is a schematic configuration diagram of an electric vehicle braking device according to an embodiment of the present invention. In the figure, electric power from a battery 1 is supplied to an induction motor 3 via an inverter 2 to drive it. The brake command device ≠ is used to generate a command value and obtain a mechanical braking force when operated by an operator. Temperature detector! detects the temperature of the induction motor 3 and inputs it to the maximum braking force calculator B. The maximum braking force calculator 2 calculates the maximum braking force based on the output of the temperature sensor 2, and supplies this to the multiplier 7. The multiplier 7 multiplies the command value output from the braking command device G by the maximum braking force output from the maximum braking force calculator B to generate a braking force reference value T and sends this to the inverter control circuit. In the configuration, a main circuit is configured in which DC power from a battery is converted to DC/AC using a voltage type transistor inverter to drive the induction motor 3.

On the other hand, in the control circuit block, only the portions related to the present invention are illustrated. Moreover, the temperature of the induction motor 3 is considered here as a detected value for reducing the braking force.

Here, the maximum braking force calculator 6 calculates the resistance value from the temperature sensor j made of a thermistor as human power, and
As shown in the characteristic diagram of FIG. Also the second
At a temperature of 72 or higher, a value that makes the output zero is output. Incidentally, a well-known configuration combining operational amplifiers can be applied to a circuit having such a human output relationship. on the other hand,
The signal input from the brake command device to the multiplier 7 is shown in Fig. 7 (
As shown in the characteristic diagram b), the output increases proportionally to the braking command value until mechanical braking is applied, and remains constant for braking command values beyond that value.

The output of the maximum braking force calculator B and the output of the braking command unit L are input to the multiplier 7, where they are multiplied to obtain the braking force reference value T.
is output as The inverter control circuit to which this braking force reference value T is input sends a conduction control signal to the transistor of the inverter I in order to produce a predetermined braking torque.

Incidentally, as the configuration of the inverter control circuit, a well-known configuration as an induction motor drive device using an inverter can be applied.

Now, assuming that the temperature of the induction motor 3 is between temperature T1 and temperature T2, the braking force reference value T is as shown in Fig. 1 (b).
will be half of that. The reason for this is that at an intermediate temperature between T1 and T2, the output of the maximum braking force calculator t becomes % of the value at low temperature, as shown in Figure 8 (8), and therefore the output signal of the brake command unit t becomes %. This is because the signal is multiplied and input to the inverter control circuit r. Figure 1 is a diagram of braking force characteristics with respect to the braking command value when such control is performed, and as shown in the figure, the braking command value at the point where mechanical ttill movement starts and the Although the magnitude of the braking force differs between the braking command values, a continuous change is obtained, and therefore the braking force can be changed without producing a dead zone as shown in the characteristic diagram of FIG.

FIG. 2 is a schematic configuration diagram of an electric vehicle braking device according to another embodiment of the present invention. In the same figure, the adder is provided to add the output of the maximum braking force calculator O and the output of the brake commander ≠, and the IJ mitter 10 has the function of cutting the output of the adder below the zero level. This output becomes the braking force reference value T.

In such a configuration, the maximum braking force calculator 6 is configured as shown in FIG.
As shown in the characteristic diagram a), the output is zero up to the first temperature T1, and from the first temperature T1 to the second temperature T2-! It has a characteristic of sending out an output in a negative direction proportional to the temperature, and sending out an output of a constant negative value at a second temperature 72 or higher. The output signal of this maximum braking force calculator B and the signal from the brake command device ≠ are added by an adder, and the limiter 10 gives a zero value for human force less than zero, and a zero value for input of a positive value. It is output as is and set as the braking force reference value T. The braking force characteristics with respect to the braking command value at this time are shown in the characteristic diagram of FIG. 7(b). By the way.

Such braking characteristics are obtained when the temperature of the induction motor 3 is T1 and T1.
It goes without saying that this is an example of a case between the two.

As the temperature of the induction motor 3 rises, even if the braking command value is increased from zero, no braking force is applied (so-called play occurs), but once the braking force starts working, from then on a braking force proportional to the braking command value can be obtained. Therefore, it has less influence than the dead zone that occurs during braking, and is effective for smooth braking.

In each of the above embodiments, the temperature of the induction motor 3 is used as the human power to change the maximum value of the braking force, but other factors include the temperature of the inverter 2, the temperature of the battery 1, By limiting the maximum value of the braking force in consideration of these factors, more accurate braking becomes possible. Also,
Although induction motor drive using an inverter has been exemplified here as a driving method for an electric vehicle, the present invention is also applicable to systems such as an inverter and a synchronous machine, a chopper and a DC machine, etc.

〔Effect of the invention〕

As described above, according to the present invention, even if the maximum value of the braking force of the electric motor has to be reduced due to a rise in temperature, etc., a dead zone occurs in the middle of braking the braking force relative to the braking command value. By making it possible to interlock without any friction, it is possible to obtain an electric vehicle braking device that achieves smooth braking performance.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between braking force and braking command value, Figure 2 is a characteristic diagram showing the relationship between braking force and braking command value when the motor starts to get hot, and Figure 3 is a characteristic diagram showing the relationship between braking force and braking command value. 1 is a schematic configuration diagram of an electric vehicle braking device according to an embodiment. Figure 3 is a characteristic diagram explaining the operation of the configuration shown in Figure 3. 3 is a characteristic diagram showing the relationship between braking force and braking command value in the configuration shown in FIG. 3; and FIG. 3 is a schematic configuration diagram of an electric vehicle braking device according to another embodiment of the present invention. FIG. 7 is a characteristic diagram illustrating the operation of the second floor configuration. l...Battery, 1...Impark, 3...Induction motor, ≠...Brake command device,! ...Temperature detector, t
...Maximum braking force calculator, 7... Multiplier Applicant's agent Boar Crotch Ulcer Figure 1 House 2 Figure 11 J Runo J Tears fI' IM Figure 6 Braking Figure 7 (α) " ( b) ↑

Claims (4)

[Claims] (1) An electric motor that receives power from a power source via a power converter to drive an electric car, and an electric motor that obtains braking force by regenerating regenerative power from the motor to the power source via a power converter. A braking means, a mechanical braking means ζ that mechanically applies braking force to the electric vehicle, a command means that outputs a braking command that commands the braking force and causes the mechanical braking means to directly perform a braking operation, and an electrical An electric vehicle characterized by comprising: a limit detection means for detecting a braking force Ω limit condition of the braking means, and a calculation means for changing the operating condition of the electric braking means in response to a braking command according to the output of the limit detection means. Braking device. (2) The electric vehicle braking device according to claim 1, wherein the limit detection means comprises temperature detection means for detecting the temperature of at least one of the electric motor and the power converter. (3) The electric vehicle braking device according to claim 1, wherein the calculation means comprises means for reducing the braking force of the electric braking means in proportion to the braking command. (4) The electric vehicle braking device according to claim 2, wherein the calculating means comprises means for reducing the braking force of the electric braking means arithmetic with respect to the braking command.