JP2894045B2 - Electric car - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle, and more particularly to a means for displaying a remaining capacity or a mileage.

[0002]

2. Description of the Related Art Along with the emergence of global environmental problems, electric vehicles have reduced energy consumption due to their high energy efficiency, and have reduced emissions, or have been able to collectively process emissions at power plants. It is noted that it is useful for acid rain control. However, electric vehicles are inferior to existing gasoline engine vehicles in price, performance, and the like, which hinders their spread. In addition to the performance problems of the electric vehicle, the usability includes a long charging time and an inaccurate remaining capacity display. For the display of the remaining capacity, a method of detecting the battery voltage, the open circuit voltage, the amount of discharged electricity, the specific gravity of the electrolyte, and the like has been mainly used. (The Japan Electric Vehicle Association, “Survey and Report on Electric Vehicle Battery Remaining Capacity Meter,” p.8, p.19 (1988).)

[0003]

In a conventional gasoline engine vehicle, the cruising distance can be easily displayed by a float type oil meter, whereas in an electric vehicle, such a problem is difficult. This is because the remaining capacity of the battery cannot be detected like measuring the liquid level in the fuel tank. Therefore, a system of a battery remaining capacity meter as described in the section of the prior art has been proposed so far. However, each of these methods has its own problems and is not practically sufficient. In the battery voltage detection method, there are problems that the battery voltage changes depending on the discharge current amount of the battery, the voltage greatly differs between the open state and the closed state, and it is difficult to apply the battery to a battery with good voltage flatness. . The open circuit voltage detection method is a method using the characteristics of a lead battery in which the open circuit voltage of the lead battery changes with the amount of discharge.However, it cannot be applied to other batteries, and the voltage change after switching from a closed circuit to an open circuit is not possible. There are problems such as the dependence on the amount of discharge electricity during closing. The method of detecting the amount of discharged electricity does not take into account the effects of self-discharge, discharge temperature, regenerative charging, and the like. Further, there are problems such as the discharge capacity of the battery to be used as a reference decreases as the charge / discharge cycle of the battery progresses. Was. The electrolyte specific gravity detection method is a method that utilizes the characteristics of lead batteries, in which the concentration of sulfuric acid in the electrolyte of a lead battery decreases with the amount of discharge. Therefore, sealed lead batteries without free electrolyte or lead batteries Not applicable to other batteries.

[0004] It is an object of the present invention to provide an electric vehicle provided with means for clearly displaying the state of charge of a battery as in a conventional gasoline engine vehicle.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the feature of the present invention is not only to strictly monitor the amount of electricity flowing into and out of the power supply of an electric vehicle, but also to determine the leaving and discharging conditions. In addition, the present state of the battery is clearly understood by further taking into account the history of the battery, and the dischargeable capacity in the future is estimated. In addition, a method is proposed in which a warning is issued in advance of the depletion of the remaining capacity so as not to make it difficult to travel in a place where charging is impossible such as on a road.

In order to strictly monitor the capacity of a battery, the amount of electricity returned to the battery by regeneration as well as the amount of charge and the amount of discharge are measured by a coulometer. At this time, the charging capacity of the battery must be calculated in consideration of the fact that the charging efficiency varies depending on the type of the battery. For simplicity of the scheme, the regenerative charging efficiency may be assumed to be 100%. The battery self-discharges by leaving it for a long time, and the discharge capacity is lost. for that reason,
It is necessary to measure the idle time using a clock. Since the self-discharge differs depending on the standing temperature, it is necessary to accurately detect and correct the temperature at this time. However, since the device becomes complicated if it reaches that point, it is sufficient to use the average temperature at which the battery is left as the self-discharge rate. Under normal use conditions in Japan, a value of 15 to 25 ° C. may be used.
Even if the current capacity of the battery is the same, the dischargeable capacity differs depending on the battery temperature, so it is necessary to detect and correct the battery temperature. Accurate evaluation is to take discharge capacity as a continuous function of temperature. For simplification of the method, for example, the temperature range is set to 5 ° C or less, 5 ° C to 30 ° C,
Divide into three regions of 30 ° C or higher,
It is practical to use a simple method in which the temperature is divided into a small number of regions and the representative temperature point of each region is used as the temperature characteristic of that region, such as adopting ° C as the temperature characteristic value of each region. In order to determine the travelable distance from the remaining capacity of the battery, the remaining capacity may be multiplied by a running coefficient (km / Ah) specific to each vehicle type. Whether the state of charge of the power supply is displayed as the remaining capacity or as the travelable distance depends on whether or not the travel coefficient is multiplied. The former is more direct,
It is accurate only for the influence of the running coefficient, which is an average value, and the apparatus is simplified. However, there is a disadvantage that it is not possible to immediately judge how many kilometers can be run.

[0007] In order not to make it difficult to travel in a place where charging is impossible such as on a road, it is preferable to display a warning to warn that charging is required when the travelable distance falls below a certain value. The setting of that value is an optional design item,
It may be necessary to display at 20-50 km. In addition, the performance of the battery is rapidly reduced due to an abnormal state such as deterioration or failure of the battery, and the vehicle may not be able to travel even if the travelable distance estimated from the above method is sufficient. When the voltage is detected and the value reaches the set lower limit voltage, it is necessary to issue a warning of "charging required" or to display a display of "travelable distance 0 km".

[0008] Battery performance decreases with repeated charge / discharge cycles. This change is continuous unless there is any abnormality. Therefore, the previous complete charge / discharge capacity can be used as the upper limit dischargeable capacity for estimating the dischargeable capacity of the battery. After the previous charging, the discharge capacity up to the warning of "charging required" or the display of "travelable distance 0 km" is used as the upper limit value. If the capacity suddenly occurs due to some abnormality, this value becomes meaningless, but an emergency warning or display can be issued by the above voltage detection.

The power source for an electric vehicle to which the present invention can be applied is not limited as long as it is a secondary battery. Lead batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, nickel-iron batteries, zinc-bromine batteries, sodium-sulfur batteries, lithium secondary batteries, and the like are examples of such batteries.

[0010]

The point of the operation of the present invention is that the characteristics are strictly grasped in consideration of the fact that the discharge capacity of the battery changes depending on the discharge conditions, and the remaining capacity is reduced because the discharge capacity decreases according to the charge / discharge cycle. Are made more accurate, and a voltage detection method is used in combination so as to cope with a sudden deterioration in the performance of a battery for which the estimation does not hold.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in more detail with reference to the drawings. This embodiment employs a method of displaying the state of charging of the power supply as a travelable distance.

In this embodiment, a 100-Ah-240V nickel-cadmium battery is mounted as a power supply on a passenger car having a body weight of 1000 kg. A rangefinder was installed. FIG. 1 is a diagram showing an electric vehicle system provided with a travelable distance meter according to the present invention. In the figure, 1 is a nickel-cadmium battery serving as a power source, 2
The battery charger controls and monitors the charging and discharging of the battery, 3 is a motor controller for controlling the motor of the electric vehicle, 4 is the motor, and 5 is the wheels. Reference numerals 1 to 5 are main components of a driving portion of a normal electric vehicle. The present invention has been implemented by providing 6 to 13 portions in the driving portion. Reference numeral 6 denotes an arithmetic processing section for detecting the operating states of the battery and the charger, and estimating and displaying the possible travel distance. Reference numeral 7 denotes a clock built in 6, reference numeral 8 denotes a temperature sensor for detecting a battery temperature, reference numeral 9 denotes a voltmeter for measuring a battery voltage, reference numeral 10 denotes a coulometer for detecting the amount of electricity flowing into and out of the battery, and reference numeral 11 denotes a detection from 7 to 10. The travelable distance meter 12 displays the travelable distance calculated based on the remaining capacity of the battery 1 estimated from the signal thus obtained. Reference numeral 12 denotes a portion for displaying a warning that the battery is in a state requiring charging.

Next, the contents of the embodiment of the present invention shown in FIG.
This will be described in more detail based on the flowchart of FIG. Following the start command, "N =
0 "is loaded to prepare for monitoring the charging of the battery 1. Charging is continued by the charger 2 under predetermined charging conditions according to the capacity, voltage, etc. of the battery until the charging end time. The number of times of charging is counted by the calculation of N = N + 1. Next, the amount of charge Q ₀ is obtained from the amount of electricity measured from the start to the end of the charge measured by the coulometer 10, and the charge obtained by correcting the charge rate from the amount of electricity is obtained. Determine the capacity Q _{N. Although} the correction factor of the charging rate varies depending on the charging control method employed in the charger, it is generally used in nickel-cadmium batteries.
The ΔV method was also employed in this embodiment. In this method, the charging rate is about 90%, so the correction coefficient was set to 0.9. The number of times of charging N is read, and Q _N-1 ≦
If it is Q _N , the possible travel distance “l ₀ km” obtained from l ₀ = Q _N-1 / a is displayed at 11. Here, Q _N-1 is the amount of electricity discharged between the previous charge and the current charge, and a
Is a mileage coefficient, which differs depending on the specifications of the electric vehicle and the power source and the running mode. In this embodiment, a = 0.40
Ah / km was used. When Q _N-1 > Q _{N and at} the time of the first charge, the possible travel distance l ₁ km is calculated from l ₁ = Q _N / a, and this is displayed at 11.

The battery voltage is detected by a voltmeter 9 and if the battery voltage is equal to or lower than the minimum lower limit voltage V _T1 , the mileage is “0 km”.
Is displayed at 11, and a charge warning “RECHARGE” is also displayed at 12. Battery voltage is greater than V _T1, and displays warning charge long less than or equal to the V _T2 to "RECHARGE" 12. The values of V _T1 and V _T2 can be changed according to the type of battery and the specifications of the power supply. In this embodiment, V _T1 = 210 V, V
_{T2 was set to} 220V. The display of mileage "0km" is displayed on 11,
Alternatively, when a charge warning “RECHARGE” is displayed in 12, whether or not to charge is an optional matter determined by the driver. Accordingly, it is a manual operation to proceed to the flowchart in FIG. 2 and start charging. If the charging is not started, the process proceeds to the step, and the process proceeds to a voltage measurement loop.

When the battery voltage is higher than V _T1 and V _T2 , the process proceeds to the next step. First, the amount of electricity flowing into and out of the battery was detected to estimate the change in remaining capacity. In this calculation, t ₁ and t ₂
Are the time of the last charge and the current time, respectively.
I (t) is a function indicating the time change of the current flowing through the battery,
I (t)> 0 indicates discharging, and I (t) <0 indicates regenerative charging. This integral is detected by the coulometer 10. This calculation gives the current remaining capacity. Next, the effect of self-discharge due to the battery being left was estimated. In this calculation, k _S is the self-discharge rate, and 0.01 / day was used. The integral term corresponds to the total idle time since the last charge. The total idle time is also determined by the clock 7. It was determined Q _N following the discharge capacity by using the temperature of the battery self-discharge correction by adding a correction considering different. The battery temperature was detected by the temperature sensor 8. The temperature correction coefficient k (T) is obtained by dividing the temperature region into three regions of 5 ° C. or less, 5 ° C. to 30 ° C., and 30 ° C. or more, and taking -10 ° C., 20 ° C., and 50 ° C. as temperature characteristic values of each region. Adopted. The temperature correction coefficients of −10 ° C., 20 ° C., and 50 ° C. were 0.85, 1.00, and 1.05, respectively. Divide Q _N by mileage coefficient a to calculate l ₂ ,
1 displays the possible travel distance “l ₂ km”. If l ₂ > 50 km, then the voltage measurement operation is again performed.
The flow loop closes. If l ₂ ≦ 50 km, “REC
HARGE ”warning is displayed in 12. Whether or not charging is performed immediately after this is an optional matter determined by the driver. Accordingly, it is a manual operation to proceed to the flowchart in FIG. 2 and start charging. If the charging is not started, the process proceeds to the step, and the process proceeds to a voltage measurement loop.

In an actual operation operation of an electric vehicle, it is considered that recharging is often performed before the display of the traveling distance "0 km" or the display of the charging warning "RECHARGE" is displayed. In this case, the processing is interrupted from FIG.
However, in this case, Q _N is the remaining capacity Q _N
The charge capacity obtained by multiplying the charge amount detected by the above by the charge rate correction coefficient by 0.9 is added. This can be expressed as follows.

[0017]

(Equation 1)

According to this method, the electric vehicle is driven on the road, and the correspondence between the traveling distance indicated at each point from the time of charging to the lower limit set voltage V _T1 and the actual traveling distance is obtained. As a result, the error was within ± 10% in the region other than the last one-third of the discharge capacity, and was within ± 15 km in the region of the last one-third of the discharge capacity. The error did not tend to increase even with the progress of the charge / discharge cycle.

By using the method of the present invention as described above, the state of the battery can be more accurately and individually detected than in the conventional method, so that the remaining capacity can be estimated accurately, and the accuracy of the mileage can be estimated. High display is possible. In addition, it is possible to cope with a sharp decrease in performance due to deterioration or abnormality of the battery.

Comparative Example As a comparative example, a capacity indicator according to the prior art was installed in an electric vehicle similar to the above-described embodiment, and a road running test was performed in the same manner. The tested capacity indicators are of three types: battery voltage, amount of discharged electricity, and open circuit voltage. As a result of the test, the electric discharge method showed the best performance, and the error was within ± 18% in a region other than the last one-third of the discharge capacity. Battery voltage method,
The open-circuit voltage method does not show a unique good correspondence with the remaining capacity except at the end of the discharge, and is difficult to apply.

[0021]

According to the present invention, a highly-accurate odometer can be obtained, and troubles that make it impossible to travel in a place where charging is difficult, such as on a road, can be reliably avoided, and the usability of an electric vehicle is improved. It can be expected to contribute to its spread.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electric vehicle provided with a travelable distance meter of a type according to the present invention.

FIG. 2 is a flowchart showing contents and functions of a travelable distance display method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nickel-cadmium battery, 2 ... Charger, 3 ... Motor controller, 4 ... Electric motor, 5 ... Wheel, 6 ... Operation processing part, 7 ... Built-in clock, 8 ... Temperature sensor, 9 ... Voltmeter, 10 ... Coulometer , 11: Travelable distance meter, 12: Charge warning display.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-30667 (JP, A) JP-A-4-368401 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60L 3/00 B60L 11/18 H02J 7/00-7/12 G01R 31/36

Claims (1)

(57) [Claims] 1. An electric vehicle having at least a power supply using a secondary battery, a motor driven by the power supply, and a control unit for controlling the motor, the electric vehicle having a discharge capacity from a charge capacity at a previous charge. It has a calculating means for calculating a travelable distance from the regenerative charge capacity, a self-discharge amount based on a discharge time, and a battery temperature, and a means for displaying the calculated travelable distance. Is displayed, or when the battery voltage is equal to or lower than the lower limit set voltage V _T2 , a warning for charging is displayed, and the calculated travel distance is 0 km or the second battery voltage is lower than V _T2. When the voltage is equal to or lower than the lower limit set voltage V _T1 , the display that the travelable distance is 0 Km is performed. When the charging is not performed after the display that warns the charging, the display or the warning that warns the charging based on the battery voltage measurement is performed. An electric vehicle, wherein a display is performed in which a travelable distance is 0 km.