JP2621196B2 - Vehicle speed calculation device - Google Patents

Description

The present invention relates to an apparatus for detecting a vehicle speed of a vehicle.

[Prior Art] Conventionally, as a vehicle speed sensor for detecting a vehicle speed (vehicle speed) of a vehicle, a vehicle speed sensor for detecting a vehicle speed in accordance with a rotation speed of a speedometer cable 20, as shown in FIG. ing. This vehicle speed sensor transmits the rotational speed of the shaft of the vehicle to a speedometer cable 20 by a drive driven gear, and a magnetic sensing element 22 is turned by a magnet 21 which is rotated by the rotation of the speedometer cable 20.
Is driven to detect the vehicle speed.

On the other hand, in a vehicle equipped with an electronically controlled automatic transmission, etc., as shown in FIG.
A magnet 32 is attached to an output shaft 31 in 30 and a reed switch 33 as a vehicle speed sensor is turned on / off by the magnet 32 to detect a vehicle speed.

As an invention and a proposal relating to the above-mentioned vehicle speed sensor, a "speed sensor" disclosed in Japanese Patent Application Laid-Open No. 57-169678 is known.

[Problems to be Solved by the Invention] However, the following problems were considered in the conventional vehicle speed sensor described above.

(A) That is, in the vehicle speed sensor using the speedometer cable 20, a problem that the output signal as the vehicle speed is easily disturbed due to uneven rotation of the speedometer cable 20, accuracy of the drive driven gear, and the like, (b) transmission In the vehicle speed sensor 30, the problem such as the above (a) is unlikely to occur, but the absolute vehicle speed (body speed) is determined in consideration of the difference in the gear ratio (so-called differential ratio) of the final reduction gear that differs depending on the vehicle type. The problem is that the operation takes time and effort. On the other hand, in order to obtain the absolute vehicle speed, an invention or a device for calculating the vehicle speed by detecting the rotation speed of the left and right driven wheels after passing through the final reduction gear has been made, but the rotation speed of the left and right driven wheels has been reduced. There was a problem that the configuration became complicated due to different operating conditions.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem and to effectively utilize a conventionally used vehicle speed sensor to detect an accurate vehicle speed with a simple configuration.

Configuration of the Invention [Means for Solving the Problems] As shown in FIG. 1, a vehicle speed calculation device according to the present invention has a speedometer cable that rotates in accordance with rotation of an output shaft in a transmission. A cable rotation speed detecting means (M1) for detecting a rotation speed, a shaft rotation speed detecting means (M2) for detecting a rotation speed of the output shaft, and a cable rotation speed detected based on the detected cable rotation speed and the shaft rotation speed. Correction coefficient calculation means (M
3) and vehicle speed calculating means (M4) for calculating a vehicle speed from the calculated correction coefficient and the detected shaft rotation speed.

[Operation] The vehicle speed calculation device of the present invention having the above-described configuration is configured to control the rotation speed of the speedometer cable detected by the cable rotation speed detection means (M1) and the rotation speed of the shaft detected by the shaft rotation speed detection means (M2). Based on the above, the correction coefficient calculating means (M3) calculates a correction coefficient for calculating the vehicle speed, and the vehicle speed calculating means (M4) calculates the vehicle speed from the calculated correction coefficient and the detected shaft rotation speed.

Embodiment Next, a preferred embodiment for further clarifying the configuration of the vehicle speed calculation device of the present invention will be described with reference to the drawings. FIG. 2 is a schematic diagram of a vehicle equipped with a vehicle speed calculation device according to one embodiment of the present invention.

The vehicle speed calculating device according to the present embodiment includes a vehicle speed meter 1, a meter vehicle speed sensor 2, a TM vehicle speed sensor 4 for detecting a rotation speed of an output shaft (not shown) in a transmission (hereinafter sometimes referred to as TM) 3, And a control circuit 5 (auto-drive device) that drives the vehicle at a predetermined speed at a specified speed. Note that the control circuit 5 also functions as an automatic transmission control device.

The meter vehicle sensor 2 rotates the speedometer cable 6 according to the rotation speed of the output shaft in the transmission 3 by a drive driven gear (not shown).

The vehicle speed meter 1 displays a vehicle speed based on the rotation speed of a speedometer cable 6 driven to rotate by a meter vehicle speed sensor 2. The vehicle speed meter 1 is a reed switch that functions as a cable rotation speed detecting means of the present invention.
Built-in 1a.

As shown in FIG. 3, the control circuit 5 includes a microprocessor unit (hereinafter referred to as M
It is configured as an electronic control circuit centered on 10).

A reed switch 1a built in the vehicle meter 1 is connected to an input port IN1 of the MPU 10 of the control circuit 5, and a reed switch 4a built in the TM vehicle speed sensor 4 is connected to the input port IN2.

The reed switch 1a is turned on / off in accordance with the rotation of the speedometer cable 6. In this embodiment, the reed switch 1a outputs a signal of four pulses every time the speedometer cable 6 makes one rotation. Similarly, the reed switch 4a
The output shaft is turned on and off in accordance with the rotation of the output shaft in the transmission 3. In this embodiment, a signal of one pulse is output every time the output shaft makes one rotation.

The operation of the present embodiment having the above configuration will be described together with a "vehicle speed calculation routine" shown in FIG. The “vehicle speed calculation routine” shown in FIG. 4 shows only a process of calculating a vehicle speed (vehicle speed) to be controlled in order to perform constant speed traveling among various processes performed by the control circuit 5 as an auto-drive device. Things. This processing is periodically executed by means such as a hardware interrupt.

When the processing shifts to this processing, the MPU 10 firstly outputs the pulse signal SM output from the reed switch 1a and the reed switch 4a.
Is input (steps 100 to 110). As described above, the pulse signal SM
Is a signal according to the rotation speed of the speedometer cable 6, and the pulse signal TM is a signal according to the rotation speed of the output shaft. In the subsequent processing, as shown in the timing chart of FIG. 5, the time ratio Rt (= TS1 / TS2) of the time TS1 required for four cycles of the pulse of the pulse signal SM and the time TS2 required for four cycles of the pulse of the pulse signal ST is determined. A calculation is performed (step 120).

When the time ratio Rt is calculated, a new correction ratio Rn smoothed according to the following equation (1) is calculated based on the calculated time ratio Rt and the correction ratio Rn-1 previously calculated in the present process. Is performed (step 130).

Correction ratio Rn = (Rt + 3 × Rn−1) / 4 (1) The smoothing process in step 130 is performed to suppress the fluctuation of the pulse signal SM.

Subsequently, after setting the value of the correction ratio Rn-1 to the calculated value of the correction ratio Rn (step 140), it is determined whether the auto drive control is started (step 150) or the auto drive control is being performed (step 160). ) Are determined one after another. here,
If both are negatively determined, the process proceeds to step 170. If an affirmative determination is made at the start of control, the process proceeds to step 190 after executing the process of step 180. Proceed to step 190.

In step 170, the calculated correction ratio Rn (step 13
0) and the detected time TS2 (step 110), a correction coefficient KV (= Rn × TS2) is calculated.

In step 180, the value of the correction ratio R is calculated as the calculated correction ratio R
A process for n and a value is performed.

In step 190, a correction coefficient KV (= R × TS2) is calculated from the correction ratio R and the detected time TS2.

After the correction coefficient KV is calculated by the above processing (step 170 or 190), the vehicle speed V (= K1 / KV) is calculated using the calculated correction coefficient KV (step 200). still,
The constant K1 used in the calculation of the vehicle speed V is a predetermined value, and is a time TS1, during which the pulse signals SM and ST are detected.
If TS2 is the time required for 8 pulse cycles,
The value is switched to a different value for use.

If the automatic drive control is not performed by the processing of steps 150 to 200 described above, step 130
The vehicle speed V is calculated based on the calculated correction ratio Rn and the detected time TS2. During the auto drive control, the correction ratio R stored at the start of the control and the detected time are calculated.
The vehicle speed V is calculated based on TS2. This is to improve the stability of the constant speed running by the auto drive control.

According to the vehicle speed calculation device of the present embodiment, with a simple configuration, the vehicle speed meter 1 and the TM vehicle speed sensor 4 which are conventionally mounted on the vehicle are used, and a stable and accurate measurement which is not affected by uneven rotation of the speedometer cable 6 or the like. It has an excellent effect that the vehicle speed V can be obtained. This makes it possible to make the constant-speed running operation of the auto-drive control more stable.

Next, a vehicle speed calculating device according to a second embodiment of the present invention will be described.

The vehicle speed calculation device according to the second embodiment includes a “vehicle speed calculation routine”
The processing shown in FIG. 6 is executed.

In the vehicle speed calculation device of the second embodiment, when the auto drive control is not performed (step 250), the vehicle speed VM calculated by the vehicle speed meter 1 and the pulse signal by the processing conventionally performed in the control circuit 5 are performed. A speed ratio Rm (VM / VT) with respect to the vehicle speed VT calculated according to ST is obtained (step 260), and the following formula (2) is obtained from the calculated speed ratio Rm and the correction coefficient Rm-1 previously calculated by the present process. )), A new correction coefficient Ro that has been smoothed according to the equation is obtained (step 270), and the value of the correction coefficient Rm-1 is calculated as the correction coefficient R
After setting the value of o (step 280), the vehicle speed V (= Ro × VT)
Is calculated (step 290). As a result, during the auto-drive control, the vehicle speed V is calculated based on the correction coefficient Ro calculated when the auto-drive control is not performed and the calculated vehicle speed VT (step).
250,290).

Correction coefficient Ro = (Rm + 3 × Rm−1) / 4 (2) The vehicle speed calculating device according to the second embodiment has the same effects as those of the first embodiment, and the structure can be further simplified. To play.

The vehicle speed calculation device of the present invention is not limited to the above-described embodiment at all, and can be implemented in various modes without departing from the gist of the present invention. For example, the case where no pulse is input while the pulse signal ST from the reed switch 4a of the TM vehicle speed sensor 4 in the present embodiment is input during four pulses of the pulse signal SM from the reed switch 1a of the vehicle speed meter 1 is set to the TM vehicle speed. The control circuit 5 determines that the sensor 4 is abnormal.
May be set to a value according to the rotation speed detected by the meter vehicle speed sensor 2. In this case, when an abnormality occurs, it is conceivable that the automatic drive control is temporarily canceled in the control circuit 5 once, and the rotational speed detected by the meter vehicle speed sensor 2 when the driver is set again is set as a control target. Similarly, even when the pulse signal SM from the reed switch 1a is not normally input, the rotation speed detected by the TM vehicle speed sensor 4 may be controlled. This allows
The usability and stability of the auto drive control can be further improved. Note that the above-described processing may be applied as follows.

Normally, a vehicle equipped with an electronically controlled automatic transmission is provided with a pulse signal proportional to the vehicle speed from a vehicle sensor in a transmission, and a vehicle without an electronically controlled automatic transmission is provided with a pulse signal proportional to the vehicle speed from a vehicle speed sensor in a vehicle speed meter. The vehicle equipped with the electronically controlled automatic transmission is configured to perform the above-mentioned processing, that is, the processing using the vehicle speed sensor in the vehicle speed meter after the automatic cancellation when the vehicle speed sensor in the transmission falls into an abnormal state. You may.

Further, in the above processing, when the pulse signal SM from the reed switch 1a is not normally input, the following configuration can be considered as a configuration for calculating the vehicle speed V by the TM vehicle speed sensor 4.

That is, a differential ratio different for each vehicle type is written in advance in a ROM built in the MPU 10 of the control circuit 5, and the differential ratio of the relevant vehicle type is selected by turning on / off a rotary switch (also called a dip switch) and the vehicle speed is changed. A configuration for calculating V is conceivable. As a result, the inconvenience of having to reset the differential ratio of the vehicle for each vehicle type can be eliminated.

There is no problem if this differential ratio selection configuration is adopted in a vehicle equipped with a conventional electronically controlled automatic transmission.

According to the vehicle speed calculation device of the present embodiment, with a simple configuration, it is possible to obtain a stable and accurate vehicle speed which is not affected by uneven rotation of a speedometer cable or the like by using a vehicle speed sensor conventionally mounted on a vehicle. It has an excellent effect of being able to.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of a vehicle speed calculation device according to the present invention, FIG. 2 is a schematic diagram of a vehicle equipped with a vehicle speed calculation device according to one embodiment of the present invention, and FIG. FIG. 4 is a flowchart showing processing of a "vehicle speed calculation routine". FIG. 5 is a timing chart showing an example of pulse signals ST and SM. FIG. 6 is a "vehicle speed calculation routine" of a second embodiment of the present invention. 7A is an explanatory diagram showing a vehicle speed sensor used in a speedometer, and FIG. 7B is an explanatory diagram showing a vehicle speed sensor in a transmission. 1: vehicle speed meter, 2: vehicle speed sensor, 4: TM vehicle speed sensor, 5: control circuit, 6: speed meter cable

Claims (1)

(57) [Claims] 1. A cable rotation speed detecting means for detecting a rotation speed of a speedometer cable which rotates in accordance with a rotation of an output side shaft in a transmission, and a shaft rotation speed detecting means for detecting a rotation speed of the output side shaft. Correction coefficient calculating means for calculating a correction coefficient based on the detected cable rotation speed and shaft rotation speed; and vehicle speed calculation means for calculating a vehicle speed from the calculated correction coefficient and the detected shaft rotation speed. And a vehicle speed calculation device comprising: