JPH04140001A - Regenerative brake controller for electric automobile - Google Patents

Abstract

PURPOSE:To extend traveling distance per single charging operation of battery by modifying the limit value of regenerative brake torque according to the fluctuation of the mechanical loss in gear system and performing regenerative brake operation adaptive to the current operating state of gear system highly efficiently without causing rear lock. CONSTITUTION:Oil temperature sensors 20, 22 are mounted, respectively, on a differential 16 and a T/M 14. The oil temperature sensors 20, 22 detect the temperature of oil in oil sumps disposed, respectively, in the differential 16 and the T/M 14 and detection results are provided to an ECU 10. The ECU 10 then sets a limit value Tmax of regenerative brake torque based on outputs temp1, temp2 from the oil sensors 20, 22 and regenerative brake torque T is determined according to the limit value Tmax. According to the constitution, maximum regenerative energy can be obtained within a range causing no rear lock and traveling distance per single charging operation of battery can be extended without sacrifice of operability or brake efficiency of electric automobile.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a regenerative braking control device for an electric vehicle that performs so-called regenerative braking, which is braking that converts the drive energy of the motor of the electric vehicle into electrical energy and recovers it in the battery. Regarding.

[Prior Art] In addition to so-called mechanical braking, regenerative braking is used as a braking means for electric vehicles.

FIG. 3 shows an example configuration of a regenerative braking control device for an electric vehicle. The conventional example shown in this figure has a configuration similar to that of the device described in, for example, Japanese Patent Laid-Open No. 59-209004.

This figure shows a motor 12 that is rotated under the control of ECUlo and generates driving force for the electric vehicle. That is, the ECUIO detects that the brake pedal is depressed and also detects the braking force of the mechanical braking system. In the case of this conventional example, the mechanical braking system is a hydraulic braking system, and the ECUlo takes in information related to the hydraulic pressure of this braking system.

A battery (not shown) is connected to the motor 12 via an inverter circuit (not shown). That is, DC power from the battery is converted to AC power by the inverter circuit, and the motor 12 is driven by this AC power.

During regenerative braking, regenerative energy is recovered to the battery through the opposite route.

The motor 12 is connected to a differential gear (hereinafter referred to as differential) 16 via a transmission (hereinafter referred to as T/M) 14 . Therefore, the rear wheels 18 are driven by the drive of the motor 12.

In this conventional example, when braking an electric vehicle,
Regenerative braking torque T is controlled according to the amount of operation of the brake pedal. That is, when the driver depresses the brake pedal, mechanical braking by hydraulic pressure is applied depending on the amount of depression, and the ECUIO determines the regenerative braking torque T according to the oil pressure and the rotational speed N of the motor 12. Such a setting of the regenerative braking torque T is intended to recover more energy into the battery during braking, thereby extending the travelable distance per battery charge.

The ECUIO further controls the drive current of the motor according to this regenerative braking torque T, and executes regenerative braking using the torque T. In addition, in an electric vehicle that drives the rear wheels 18 as in this conventional example, in order to prevent the rear wheels 18 from locking in advance of the front wheels and reducing the braking efficiency during braking, as shown in FIG. The regenerative braking torque T is determined by limiting the regenerative braking torque T by a limit value T max so that it does not exceed this limit (downward in FIG. 4).

In this way, conventional braking has been performed in response to regenerative braking or brake pedal effort, and as a result, it has been possible to obtain a relatively long travel distance.

Further, by limiting the regenerative braking torque T using the limit value T max, the rear lock is prevented from occurring, thereby realizing an electric vehicle with good maneuverability and braking efficiency.

[Problems to be Solved by the Invention] However, in recent years, there has been a growing demand for further extending the travel distance of electric vehicles.

Conventionally, regenerative braking torque has been generated in accordance with the amount of brake operation as described above in order to extend the travelable distance. However, the value of the regenerative braking torque that can be extracted is initially limited by the limit value for preventing the rear lock from proceeding, and there is a limit to the further extension of the travelable distance by this means.

The present invention was made with the aim of solving these problems, and it provides efficient regenerative braking without causing the rear lock to disturb, thereby extending the distance the vehicle can travel on a single charge of the battery. The purpose is to

[Means for Solving Problem 111] In attempting to achieve such an objective, the inventors:
We are conducting an experimental investigation to find out what conditions the regenerative braking torque that causes rear lock depends on. The results of this experiment show that such torque changes in response to changes in mechanical losses in the gear system (eg, including T/M and differential).

In other words, the gear system is in a cold state (state before starting operation)
By comparing the case where the gear system is in a hot state (in operation) and the case where the gear system is in a hot state (in operation), it can be seen that the mechanical loss of the gear system changes depending on the change in state. Moreover, quantitatively, the former is larger than the latter. On the other hand, the regenerative braking torque that causes the rear lock is determined according to this mechanical loss. If the mechanical loss of the gear system is expressed as torque Tloss, and the theoretical value (constant) of regenerative braking torque that causes rear lock is expressed as Tc, then Tmax - Tc - Tloss (1) According to the formula, regenerative braking that causes rear lock The actual value of the torque is determined as T max.

Conventionally, whether or not rear lock is caused is determined in a cold state, and as a result, T max is determined by the loss T106S in the cold state.

Therefore, the limit value of regenerative braking torque was also set to T1naX in this cold state.

In the present invention, in view of the fact that this loss T1oss changes depending on the state in which the gear system is placed, the mechanical loss of the gear system is detected and the limit value TIoax is changed and set to optimally recover regenerative energy. Suggest a method. That is, the present invention includes a means for detecting mechanical loss in a gear system, and a means for setting a limit value of regenerative braking torque based on the detected mechanical loss. The present invention is characterized in that the limit value of the braking torque is changed and set to perform regenerative braking that is adapted to the current operating state of the gear system.

[Operation] In the present invention, the mechanical loss of the gear system is detected during regenerative braking, and the limit value of the regenerative braking torque is set based on the detected mechanical loss. Therefore, even if the mechanical loss of the gear system changes due to the operating state of the gear system, the limit value is set to follow this change, and the maximum regenerative braking torque can be achieved in response to the situation without causing rear lock. This enables regenerative braking. Therefore, efficient regenerative braking that maximizes the power recovered to the battery is realized. This increases the distance that the battery can travel per charge.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the same components as those of the conventional example shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows the configuration of a regenerative braking control device for an electric vehicle according to an embodiment of the present invention.

This figure shows a configuration in which oil temperature sensors 20 and 22 are further added to the conventional configuration shown in FIG. 3. The oil temperature sensor 20 is attached to the differential 16, and the oil temperature sensor 22 is attached to the T/M 14, respectively. Oil temperature sensor 2
0 and 22 detect the oil temperature of the oil present in the oil reservoir inside the differential 16 and T/M 14, respectively, and
Outputs the detection results to. ECUIO is oil temperature sensor 20
A limit value T wax is set based on the outputs templ and te*p2 of 22, and the regenerative braking torque T is determined according to this limit value T wax.

FIG. 2 shows the flow of operation of the ECUIO in this embodiment.

In this embodiment, the ECUIO first determines whether the brake pedal has been operated (100). Specifically, it is determined whether a brake switch provided on the brake pedal is turned on. At this time, if the brake switch is off, the brake flag is set to 0 (102), and the motor 12 is controlled during driving.

Conversely, if the brake switch is on, it is determined whether the brake flag is 1 (104). 1
A case of 0 means that braking control has been performed continuously since the last time the routine shown in this figure was executed, and a case of 0 means that the brake switch is turned on for the first time. This is the case.

First, the operation in the latter case, that is, when the brake flag is 0, will be explained. In this case, first step 10
6, calculation of the maximum regenerative braking torque Tmaxl is executed. The maximum regenerative braking torque Tmaxl is the value of the regenerative braking torque T corresponding to the initial speed NO at the start of braking, as shown in FIG.

After this, the limit value T wax is determined (108).

This step 108 is a characteristic step of the present invention. In step 108, the oil temperature teipl is detected by the oil temperature sensors 20 and 22.

The map on the ECUIO is referred to by temp2, and the limit value TIaX is determined.

The map used in this step 108 is T/
Oil 1teIIpl representing mechanical loss Tloss of M14 and differential 16, temp2 and limit value T to be set
This is a map that associates wax. This correspondence is expressed as an equation as follows.

Tmax −f (T c−Tloss) (
2) Tloss-g (tellpl, tesp2)
(3) Of these, equation (2) is a negative version of equation (1) above, and f2g each represents a function.

That is, the loss Tloss is determined by the oil temperature temp 1 , t
It corresponds to egap 2, and the loss Tloss corresponds to T l1aX, which is the limit at which rear lock occurs. This formula is
Physically, the mechanical loss Tlo of the T/M 14 and the differential 16
ss depends on the oil stirring resistance, and the stirring resistance depends on the oil temperature te.
ipl.

This indicates that it depends on temp2.

Conversely, in this embodiment, the oil temperature templ.

The mechanical loss Tloss of the T/M 14 and the differential 16 is determined by detecting temp2, and the determined mechanical loss Tlos
The limit Ta+ax at which rear lock occurs is determined from s and set as the limit value.

In general, the higher the oil temperatures temp 1 and temp 2, the smaller the stirring resistance and the smaller the loss Tloss.

Moreover, when the loss Tloss is small, the limit value T wax
It is also common for it to be smaller. Also, the loss Tloss
can be treated as efficiency when designing a map.

Next, regenerative braking torque T is determined according to the maximum regenerative torque T (110). This determination method is similar to the method disclosed in Japanese Patent Laid-Open No. 1-58302, which was previously filed by the applicant of the present application.

That is, the regenerative torque command variable 68 is generated according to the amount of depression of the brake pedal, and the regenerative braking torque T is determined according to the formula TI-δB-Tmaxl (4).

The regenerative braking torque T determined in this manner can provide stable braking characteristics at the start of braking, regardless of the characteristics of the mechanical braking system, for example. Therefore,
This setting is particularly effective when the amount of brake depression at the start of braking is small. A characteristic feature of the present invention is the torque setting when the regenerative braking torque T obtained in this way is large, that is, when it would be subject to limitation by the limit value T wax in the conventional case.

In this example, after step 110, decision 1
12 is executed. In determination 112, it is determined whether regenerative braking torque T is greater than limit value T wax. If it is determined that the regenerative braking torque T is large, a limit value T wax is set for the regenerative braking torque T (114). That is, the regenerative braking torque T is limited by the limit value Tll1ax. After this, the process moves to step 116.

On the other hand, if it is determined that the size is not large, there is no need for such a restriction, and the process immediately moves to step 116. In step 116, the brake flag is set to 1.

By executing step 116, this routine ends. Thereafter, a torque command is issued by a routine not shown, and the regenerative braking torque T set in step 110 or 114 is generated in the motor 12, and regenerative braking is performed.

Furthermore, if the brake switch is in the on state when this routine is executed again, the previous step 116
Since the brake flag is set to 1 in step 1, step 118 is executed instead of step 106 after determination 104. In step 118, step 110
Similarly, set the regenerative braking torque T. Note that the maximum regenerative torque Taxl used at this time is the value determined in step 106 last time.

After step 118, a determination 120 similar to the aforementioned determination 112 is executed, and depending on the determination result, step 122, which is similar to step 114, is executed or the routine ends without being executed. In this case, since the previous brake flag has already been set to 1, step 11
The step corresponding to 6 is not executed.

The above operation is repeated at a predetermined period in the ECUIO.

Therefore, in this embodiment, the T/M 14 and the differential 16
The oil temperatures templ and temp2 are detected and the mechanical loss Tloss is determined to determine the limit value Tmax, so the T/M can be adjusted without causing rear lock.
The maximum regenerative energy can be obtained depending on the states of the differential gear 14 and the differential gear 16. Therefore, it is possible to extend the travelable distance per charge of the battery by, for example, about 10%.

In addition, in this embodiment, T/M 14 and differential 1
Since the absorption that decreases as a result of the mechanical loss of 6 is compensated for by the regenerative braking force, the braking force at the limit value Tll1ax remains constant for the rear wheels 18. This improves brake feel.

In this embodiment, the oil temperatures templ and temp2 are used as information on which to calculate the mechanical loss Tloss, but any other information may be used as long as it corresponds to the mechanical loss Tloss. For example, measure the oil viscosity of the T/M 14 and differential 16, and calculate the mechanical loss Tloss.
A similar operation can be achieved by treating as a function of oil viscosity.

Further, in this embodiment, the method disclosed in Japanese Patent Application Laid-open No. 1-58203 is used in combination, but such combination is not essential to the present invention.

[Effects of the Invention] As explained above, according to the present invention, the regenerative braking torque is determined by setting a limit value according to the mechanical loss of the gear system. It is possible to obtain regenerative energy, and it is possible to extend the distance that an electric vehicle can travel per battery charge without deteriorating its maneuverability, braking efficiency, etc.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a regenerative braking control device for an electric vehicle according to an embodiment of the present invention, FIG. 2 is a flow chart diagram showing the operation of the ECU in this embodiment, and FIG. FIG. 4 is a diagram showing the configuration of a regenerative braking control device for an electric vehicle according to an example. FIG. 4 is an explanatory diagram of a limit value of regenerative braking torque and a maximum regenerative braking torque. 10... ECU 12... Motor 14... Transmission (T/M) 16 ・
・・Differential gear (diff) 18 ・・
Rear wheels 20, 22... Oil temperature sensor teaIp1, temp2 -... Oil temperature T
... Regenerative braking torque

Claims (1)

[Claims] Regenerative braking torque is generated in response to the operation of the brake pedal by the driver within a range that does not exceed a limit value set to prevent rear wheel lock from occurring in advance, and this regenerative braking torque is used to A regenerative braking control device for an electric vehicle that regeneratively brakes a wheel-drive electric vehicle, comprising means for detecting mechanical loss in a gear system, and means for setting a limit value of regenerative braking torque based on the detected mechanical loss. A regenerative braking control device for an electric vehicle, characterized in that the limit value of regenerative braking torque is changed and set in accordance with fluctuations in mechanical loss of the gear system, and regenerative braking is performed in accordance with the current operating state of the gear system.