JP2971503B2 - Electronic odometer - Google Patents

Description

The present invention relates to a vehicle-mounted electronic odometer using a nonvolatile memory.

(Prior art)

As a conventional electronic odometer, for example, there is one shown in FIG. 3 (for example, described in Japanese Patent Application Laid-Open No. 56-89009).

In FIG. 3, the signal S ₀ is a signal from the travel distance sensor (not shown), for example, the vehicle is a pulse signal outputted for each traveling about 1 m.

The counter 1 counts the signal S ₀ of the above, for example 10
And outputs the signals S ₁ each time 00 pulses the count (vehicle 1km running).

Further, presettable counter 2 adds the preset previous integrated travel distance count the signals S ₁ described above. Then, the value of the counting result, that is, the integrated traveling distance of the vehicle is displayed on the display 4 via the decoder driver circuit 3.

The nonvolatile memory (e.g., EEPROM, etc.) 6, every time said signal S ₁ is given, presettable counter 2 counts at that time, that is, stores the accumulated running distance.

Further, the voltage monitor 5 detects power-on from the value of the power supply voltage V ₀ rises above a predetermined value. When power-on is detected, the nonvolatile memory 6 refers to the address where the accumulated mileage data is stored, reads out the accumulated mileage data, and sets the accumulated mileage data in the presettable counter 2. Presettable counter 2 treats the set has been accumulated running distance as an initial value, counting by adding sequentially signals S ₁ to the value.

Therefore, even if the power is turned off when the engine is stopped, the accumulated traveling distance data does not disappear. Then, when the power supply voltage rises at the time of the next engine start, the integrated travel distance stored in the nonvolatile memory is read out and preset in the presettable counter 2.

However, with the above configuration alone, a problem occurs when an error occurs. Therefore, an error check circuit 7 is provided (for example, described in Japanese Patent Application Laid-Open No. 60-105915).

That is, the error check circuit 7 performs an error check when reading the stored data of the accumulated mileage from the non-volatile memory 6 and immediately updates the storage area of the non-volatile memory 6 when an error occurs, and integrates the data with the updated address. Write the correction data of the mileage.

As an error check method in the error check circuit 7, the same travel distance data is written in three places in consideration of the reliability of the write data after writing to the nonvolatile memory, and the like. At the time of reading, there is a method of reading traveling distance data stored in three places, comparing them with each other, and detecting an error by using a majority decision or the like (for example, described in JP-A-59-107207).

[Problems to be solved by the invention]

However, in the conventional electronic odometer as described above, when an error occurs in the read data,
A problem may occur when storing the correction value and the update address of the mileage data in the nonvolatile memory.

In operation of the such the electronic odometer, first, writing into the nonvolatile memory 6 the accumulated running distance data presettable counter 2 at the timing of the signals S ₁ generated every predetermined distance running, the error check circuit reads after completion of writing performs error checking at 7 updates the address in the event of an error in the operation of the order of writing the correction data of the integrated travel distance to the update address, a normal vehicle for signals S ₁ is generated running Occasionally, the engine is operating normally and the power supply voltage is considered to be normal, so there is no problem.

However, when the power is turned on, that is, when the engine is started, the voltage of the battery is greatly reduced due to cranking of the engine. Therefore, in the case of an error check at the time of reading data at the time of turning on the power, the error check circuit 7 is used. When an update address and correction data of the accumulated mileage are written in the nonvolatile memory 6 after the error is detected in the nonvolatile memory 6, as shown in FIG. 4, there is a possibility that the power supply voltage is greatly reduced due to cranking. In such a case, in such a case, it becomes impossible to correctly store the corrected address and the corrected data of the accumulated mileage, and a problem occurs that the function as the odometer stops thereafter.

In addition, even if a power-on-clear method that performs clearing when the power supply voltage becomes equal to or higher than a predetermined value is applied to address the above-described problem, the power-on-clear function operates even when the voltage rises for a moment and then drops immediately However, since the writing time of the nonvolatile memory 6 requires about 10 seconds, it may not be possible to cope with the problem. Therefore, it is necessary to use a backup power supply or the like, which causes a problem that the circuit configuration becomes large and the cost increases.

Further, in order to solve the above-mentioned problem, for an error that occurred during an error check at the time of power-on, correction data is set in the presettable counter 2 and displayed, but the error correction value is not stored, how to correct the next time a certain travel distance signals S ₁ occurred are also contemplated. However, when this method is used, the following problem occurs.

That is, considering a method of error check by majority decision, when data is corrected by using three data of travel distance data storage locations A, B, and C, for example, A
When the storage location of the assumption that was error, because it does not the correction at this time, when the predetermined travel distance signals S ₁ of the following occurs, adding a constant distance value again error locations A and B, in the storage area of the C After accessing the traveled distance data and performing an error check, an operation for switching the error occurrence storage location A here is performed. At this time, since the storage area of A does not always become an error, several accesses are executed. During this time, it cannot be determined that no error occurs in the other storage areas B and C. If it is considered that an error has occurred in the storage area B, the error in the storage area A cannot be detected. Thereafter, it is determined that the areas of the error storage locations A and B are correct, and the correct storage area C is determined to be an error. Since the determination is made, the storage area C is always switched, and a correct error check cannot be performed. In addition, since the storage area is always switched, the storage area is reduced, which eventually causes a problem that the system is down in a short time.

The present invention has been made to solve the problems of the prior art as described above, and to provide an electronic odometer that does not have a risk of causing memory corruption of integrated mileage data and mileage data storage address when power is turned on. With the goal.

[Means for solving the problem]

In order to solve the above problem, the present invention is configured as described in the claims.

That is, in the present invention, every time the vehicle travels a certain distance (for example, about 1 m), a pulse of a traveling distance sensor that generates a pulse is counted, and each time the traveling distance reaches a first predetermined value (for example, 1 km). A counter for transmitting a first signal and transmitting a second signal each time a second predetermined value (for example, 100 m) shorter than the first predetermined value is reached, and an error check circuit detecting an error, A latch circuit for temporarily storing the contents, ie, a change address and correction data of the accumulated mileage, is provided. Normally, every time the first signal is given, the accumulated mileage data of the presettable counter is stored in the nonvolatile memory. When an error occurs, the address of the nonvolatile memory is updated in accordance with the contents of the latch circuit at the time when the second signal is given, and the integrated running is performed with the updated address. It is obtained by configured to write the corrected data of the release.

With the above-described configuration, according to the present invention, after the vehicle starts running, that is, after the engine is completely started and the power supply voltage is normal, when an error occurs, the corrected address and the corrected mileage data are corrected. Is performed, there is no danger of being affected by the power supply voltage drop due to cranking.

In addition, since the correction is performed when the vehicle travels a second predetermined distance shorter than the first predetermined distance in which the normal writing is performed, the corrected value is written in the normal writing.

(Example of the invention)

 FIG. 1 is a block diagram of one embodiment of the present invention.

In Figure 1, the signal S ₀ is a signal from the travel distance sensor (not shown), for example, the vehicle is a pulse signal outputted for each of 1m traveling.

The counter 8 counts the signal S ₀ of the travel distance is the signals S ₁ sent to each reaches a first predetermined value (for example 1km), said shorter than the first predetermined value a second predetermined sends a signal S ₂ for each reaches a value (e.g., 100 m).

Further, presettable counter 2 adds the preset previous integrated travel distance count the signals S ₁ described above. Then, the value of the counting result, that is, the integrated traveling distance of the vehicle is displayed on the display 4 via the decoder driver circuit 3.

The nonvolatile memory 6, for each of the above signals S ₁ is given, presettable counter 2 counts at that time,
That is, the accumulated traveling distance is stored.

Further, the voltage monitor 5 detects power-on from the value of the power supply voltage V ₀ rises above a predetermined value.

When power-on is detected, the nonvolatile memory 6 refers to the address where the accumulated mileage data is stored, reads out the accumulated mileage data, and stores the accumulated mileage data via the error check circuit 7 into a preset state. Set it on the double counter 2.

The error check circuit 7 performs an error check when reading stored data of the accumulated traveling distance from the nonvolatile memory 6.

Further, when the error check circuit 7 detects an error, the latch circuit 9 temporarily stores the content thereof, that is, the changed address and the correction data of the accumulated traveling distance.

 Next, the operation will be described.

First, when the power is turned on, the voltage monitor 5 detects that the power is turned on, reads out the accumulated traveling distance data from the nonvolatile memory 6, and sets the accumulated traveling distance in the presettable counter 2 via the error check circuit 7 in a normal state. .
The processing when an error occurs will be described later.

During normal driving, a certain distance (for example, 1k
m) for each travel, the counter 8 sends out a signal S _1, is added to the previous integrated travel distance is preset the presettable counter 2 sequentially counts the signal S _1. Then, the count value, that is, the accumulated traveling distance is displayed on the display 4 via the decoder driver circuit 3.

Further, the count value of the presettable counter 2 is written in the nonvolatile memory 6 every time the above-mentioned signal S ₁ is given.

On the other hand, when the above-described writing is performed, the error check circuit 7 reads the traveling distance storage data from the nonvolatile memory 6 and checks whether the data is stored correctly. As a result, when the data is correctly stored, the above-described normal operation is continued. When an error is detected, the storage area of the nonvolatile memory 6 is updated, and the update address and the integrated mileage are corrected. Data is set in the latch circuit 9. Then, a signal S ₂ is output from the counter 8 (for example, output every 100 m).
Is given, the correction data of the accumulated mileage is stored in the update address of the nonvolatile memory 6.

If an error is detected by the error check circuit 7 when the integrated traveling distance data is read from the nonvolatile memory 6 when the power is turned on, the correction value and the updated address of the integrated traveling distance data are latched by the latch circuit. Latch to 9. And it said and the signal S ₂ is supplied similarly, stores correction data of the integrated mileage of the above update address.

As described above, in the circuit of FIG. 1, when the power is turned on, the integrated traveling distance stored in the nonvolatile memory 6 is immediately set in the presettable counter 2 and displayed. time updates, the vehicle is configured to perform when the signal S ₂ output after run the predetermined distance is given. When the vehicle is running, it is expected that the engine is completely started and the power supply voltage is normal. Therefore, updating the memory contents at this time does not cause any inconvenience.

FIG. 2 is a diagram showing a power supply voltage waveform and a write timing in the above operation. As shown in FIG. 2, the signal S ₂ is applied is after the vehicle has started running, the power supply voltage at this time is stable at normal.

Further, in the embodiment of FIG. 1, when an error occurs, the update address and the correction value of the accumulated traveling distance are temporarily stored in the latch circuit 9, so that the correction at the time of occurrence of the error is performed. There is no risk of mistake.

The voltage monitor 5, since the power supply voltage V ₀ is determined that the power is turned on for each rise above a predetermined value, as shown in FIG. 2, when the supply voltage drops by cranking after rises once, following When the power is turned on again, it is determined that the power is turned on, and reading from the nonvolatile memory 6 and error detection by the error check circuit 7 are performed again. Therefore, after the first error is detected, the power supply voltage sharply drops due to cranking.
However, even if the correction contents cannot be stored in some cases, the error check and the correction contents are surely performed when the power supply voltage rises next time.

In addition, since the correction is performed when the vehicle travels a second predetermined distance shorter than the first predetermined distance in which the normal writing is performed, the corrected value is written in the normal writing.

〔The invention's effect〕

As described above, according to the present invention, the correction writing of the integrated mileage data in the case where an error occurs is performed when the vehicle has traveled a predetermined distance shorter than the mileage for performing the normal writing. With this configuration, it is possible to prevent the storage of the integrated mileage data and the mileage data storage address from being destroyed due to a voltage drop at the time of power supply caused by cranking or the like at the time of engine start, thereby improving the reliability of the odometer. I can do it. Further, as compared with the case where a backup power supply or the like is provided, the effect is obtained that the configuration is simpler and more reliable control can be executed.

[Brief description of the drawings]

1 is a block diagram of one embodiment of the present invention, FIG. 2 is a diagram showing a write timing in the present invention, FIG. 3 is a block diagram of an example of a conventional device, and FIG. 4 is a write timing in a conventional device. FIG. <Explanation of reference numerals> 1 ... Counter 2 ... Presettable counter 3 ... Decoder driver circuit 4 ... Display 5 ... Voltage monitor 6 ... Non-volatile memory 7 ... Error check circuit 8 ... Counter 9 ... Latch circuit

(56) References JP-A-56-89009 (JP, A) JP-A-60-105915 (JP, A) JP-A-63-81206 (JP, U) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G01C 22/00

Claims (1)

(57) [Claims] A traveling distance sensor for generating a pulse each time the vehicle travels a predetermined distance; counting the pulses; and transmitting a first signal each time the traveling distance reaches a first predetermined value. A counter for sending a second signal each time a second predetermined value shorter than the first predetermined value is reached, and a preset integrated travel distance read from the following non-volatile memory when the power is turned on, preset to the value. A presettable counter for adding and counting the first signal of the counter; a display for displaying the mileage according to the count result of the presettable counter; and an address for a data storage area. A nonvolatile memory that refers to an address and stores the count result of the presettable counter at the address, and a storage data when reading the storage data of the nonvolatile memory. And a latch circuit for temporarily storing an update address and correction data of the accumulated traveling distance when the error check circuit detects an error, and the nonvolatile memory comprises: Each time the first signal of the counter is supplied, the count value of the presettable counter is stored. If an error occurs, the stored contents of the latch circuit are provided when the second signal of the counter is supplied. An electronic odometer for storing correction data at an update address based on the odometer.