JPH01295168A - Analog meter driving circuit - Google Patents

Abstract

PURPOSE:To follow smoothly up an increase in the interval of signal pulses by outputting a pulse frequency signal which is in inverse proportion to the sum of a last reference pulse interval and an expanded interval in every specific expansion period when one pulse element interval is wider than the last reference pulse interval. CONSTITUTION:A pulse signal is inputted to a controller 5 at time t1 while a vehicle speed is slowed down, and then counted pulse element intervals T1 (=t0-t1) are sent to the analog meter driving circuit ALU3 through a delay register 2 from a counter 1. The ALU3 outputs an analog signal voltage V1 which is in inverse proportion to the pulse element intervals T1 to a speedometer. Then a timer 9 starts operating at time t10 when a pulse element interval T2 being counted currently becomes equal to the reference pulse interval (=pulse element interval T1) set in the delay register 2, and an analog signal voltage V11 which is in inverse proportion to the current counted value (t11-t1) of the counter 1 is outputted at time t11 when the timer 9 turns off.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an analog meter drive circuit that displays an input pulse frequency in analog form. The analog meter drive circuit of the present invention can be applied to, for example, a tachometer or a speedometer.

[Prior Art] Conventionally, an analog meter drive circuit is known that converts a pulse signal from a pulse output type vehicle speed sensor into an analog signal and outputs the analog signal to an analog speed meter.

This analog meter drive circuit receives a pulse signal having a pulse element interval inversely proportional to the vehicle speed from the vehicle speed sensor, and includes a pulse element interval measuring means for digitally measuring each pulse element interval, and a pulse element interval measuring means that digitally measures each pulse element interval, and a pulse element interval that is inversely proportional to the immediately preceding pulse element interval. It consists of a pulse frequency calculation means that digitally outputs a pulse frequency signal, and an analog signal output means that converts the pulse frequency signal into D/-2=△ and outputs it to an analog speedometer, and is generally composed of a microcomputer device. ing.

FIG. 9 shows a signal waveform diagram of this analog meter drive circuit.

In this analog meter drive circuit, signal pulses are formed at the rising edge to, t2 and the falling edge t1 of the vehicle speed pulse received from the vehicle speed sensor, and the pulse elementary intervals T1, T2, T3 are measured. and from tl to t
At time 2, an analog signal voltage v1 proportional to the reciprocal of the pulse interval T1 is output to the speedometer. Similarly, from t2 to t3, an analog signal voltage v2 proportional to the reciprocal of the pulse element interval T2 is output to the speedometer, and thereafter analog signal voltages are similarly output to the speedometer to display the vehicle speed in analog form. In addition, in Figure 9,
When the vehicle speed increases, the pulse interval becomes shorter, and when the vehicle speed decreases, the pulse interval becomes longer.

[Problems to be Solved by the Invention] = 3 - However, the above-mentioned conventional analog meter drive circuit has problems with the analog output to the speedometer, as seen before and after time t2 in FIG. 9, when the vehicle speed suddenly decelerates. There was a problem in which the signal voltage changed significantly in a step-like manner, causing the speedometer needle to move unnaturally.

In addition, such a problem occurs not only in the analog meter drive circuit for driving the speedometer described above, but also in the analog display of the frequency of pulses output from the pulse output type sensor (i.e., the reciprocal of the previous pulse element interval). It also existed in other analog meter drive circuits.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an analog meter drive circuit that can more naturally follow a decrease in the frequency of input pulse signals (that is, a significant expansion of the pulse unit interval). The purpose is to

[Means for Solving the Problems] The analog meter drive circuit of the present invention includes a pulse element interval measuring means that receives a pulse signal input at irregular intervals and measures the pulse element interval between each pulse of the pulse signal;
A reference pulse measuring means that calculates a reference pulse interval from one or more pulse elementary intervals obtained a predetermined time ago, and a next pulse to be input next is not input within a time equal to the previous reference pulse interval. The pulse element interval extension detection means detects that the next pulse element interval is wider than the immediately preceding reference pulse interval; During the spread detection period, the pulse frequency calculation means digitally outputs a pulse frequency signal that is inversely proportional to the sum of the immediately preceding reference pulse interval and the spread interval every predetermined spread period, and the pulse frequency calculation means converts the pulse frequency signal into an analog signal. and an analog signal output means for outputting the signal to the analog meter.

Here, the pulse element interval can be the pulse period between adjacent pulses (ie, pulse width+pulse interval). Further, the pulse element interval can be configured by both the pulse width and the pulse interval depending on the form of the input pulse signal.

The next pulse is a pulse that is input next to the input pulse signal.

The next pulse unit interval refers to the pulse unit interval between the immediately previous pulse and the next pulse.

The reference pulse interval refers to a pulse interval for spread detection that is selected or synthesized from previous pulse element intervals.

The most recent reference pulse interval refers to the latest selected or combined reference pulse interval.

[Operation] In the analog meter drive circuit of the present invention, the pulse element interval measuring means measures the pulse element interval of the input pulse signal. The reference pulse measuring means forms a reference pulse interval for detecting expansion of the pulse element interval from a previously input predetermined one or more pulse element intervals. The pulse element interval extension detection means detects that the next pulse has not been input within a time equal to the immediately preceding reference pulse interval (i.e., the currently set pulse element interval), and extends the next pulse element interval (i.e., the current pulse element interval). It is detected that the pulse element interval (currently being measured) is wider than the immediately preceding reference pulse interval. The pulse frequency calculation means is inversely proportional to the immediately preceding reference pulse interval during the non-detection period of extension, and inversely proportional to the sum of the immediately preceding reference pulse interval and the extended interval for each predetermined extension period during the extension detection period. Digitally outputs the pulse frequency signal. The analog signal output means converts the pulse frequency signal into an analog signal and outputs it to the analog meter.

That is, in the analog meter drive circuit of the present invention, if the next pulse element interval (i.e., the pulse element interval currently being measured) is wider than the immediately preceding reference pulse interval (i.e., the currently set reference pulse interval), the predetermined pulse interval is A pulse frequency signal that is inversely proportional to the sum of the immediately preceding reference pulse interval and the expanded interval is digitally output for each expansion period of It becomes possible to follow the increase clearly.

[Embodiment] First, FIG. 2 shows a vehicle speed display device for an automobile using an analog meter drive circuit according to an embodiment of the present invention.

This device includes a vehicle speed sensor 100 connected to an axle (not shown) of an automobile to detect its rotation;
Analog meter drive circuit 1 that receives vehicle speed pulses from 0
It is comprised of a pulse edge detection circuit 103 for pulse shaping that outputs a pulse signal at 0, an analog meter drive circuit 10 that outputs an analog signal voltage, and a speed meter 200 that constitutes an analog meter.

The vehicle speed sensor 100 is connected to the axle and has two pairs of magnetic poles (
It consists of a rotating magnet section 101 having a magnetic pole (N, S, N, .

When the magnetic poles (N, S) leave the reed switch 102, a vehicle speed pulse is output during a period (for example, T1, T3), and each magnetic pole (N
, S, N, S) is configured not to output a vehicle speed pulse during a period (for example, T2) when the reed switch 102 is close to the reed switch 102.

The pulse edge detection circuit 103 is a circuit that detects the rising and falling edges of an input pulse signal, that is, the pulse edges, and outputs sharp signal pulses.

The speedometer 200 is a cross-coil type or moving coil type speedometer, and is configured to display a vehicle speed proportional to an input analog signal voltage.

The functional configuration of this analog meter drive circuit 10 is shown in FIG.

This analog meter drive circuit 10 includes a pulse element interval measuring means for receiving a pulse signal inputted at irregular intervals from a pulse edge detection circuit 103 (see FIG. 2) and measuring the pulse element interval between each pulse of the pulse signal; pieces or 2
A reference pulse measuring means that calculates a reference pulse interval from more than one pulse element interval; pulse element interval extension detection means for detecting that the next pulse element interval currently being measured is wider than the immediately preceding reference pulse interval;
During the spread detection period, the pulse frequency calculation means digitally outputs a pulse frequency signal that is inversely proportional to the sum of the immediately preceding reference pulse interval and the spread interval every predetermined spread period, and the pulse frequency calculation means converts the pulse frequency signal into an analog signal. The microcomputer device functions as an analog signal output means for outputting signals to an analog meter.

A block diagram of this analog meter drive circuit 10 and pulse edge detection circuit 103 is shown in FIG.

This analog meter drive circuit 10 includes a counter 1 and a delay register 2, which are connected so as to be able to exchange data via a data bus.
, an arithmetic logic circuit (ALU>3, an output interface 4 , a controller 5 for internal control that receives pulse signals output from the pulse edge detection circuit 103 , and a clock generator 6 that sends clock pulses to the counter 1
and a timer 9 which is controlled by the controller 5 and generates a time delay signal -10- of 2m5ec.

Output interface 4 connects ALtJ via the data bus.
A D/A converter (not shown) that converts the digital signal sent from 3 into an analog signal voltage, a sample hold circuit (not shown) that samples and holds the obtained analog signal voltage, and an output from the sample hold circuit. It has a built-in driver amplifier (not shown) that power amplifies the analog signal voltage and outputs it to the speedometer 100.

Note that each component other than the output interface 4 is well known, so a description thereof will be omitted.

The operation of this analog mail drive circuit 10 will be explained with reference to the flowchart of FIG. 4 and the signal waveform diagram of FIG. 5.

First, initialization is performed (5101), and it is checked whether a signal pulse is input from the pulse edge detection circuit 103 (S1
02), if input, reset counter 1 after writing the count value of counter 1 (reference pulse interval Cm) to delay register 2 3103), if not input, 5102
Return to

At 8104, the reference pulse interval Cm is output to a register (not shown) built into A1-U 3. This reference pulse interval Cm is data used to detect the expansion of the pulse element interval in a later step, and in this embodiment, the count value written in the delay register 2 (i.e., the immediately preceding pulse element interval ) is adopted.

5105r, calculates a digital vehicle speed value Va=1/Cm and sends it to the output interface 4, which converts the digital vehicle speed value ■a into an analog signal voltage using the built-in D/A converter (not shown). The built-in sample and hold circuit (not shown) samples and holds the analog signal voltage until the next digital vehicle speed value va is input, and the built-in driver amplifier (not shown) converts the analog signal voltage to Amplify the electric saw and speedometer 10
Output to 0.

In the next step 5106, it is determined whether the next pulse element interval Cn being counted by the counter 1 is greater than the previous reference pulse interval Cm. If On≦Cm, the vehicle speed has not slowed down, so the edge pulse is input. 5107) and 510 if Edge Pulse is not input.
Return to 6. Also, if Edge Pulse is input, 810
Return to step 3 and start a new pulse element interval.

If On>Cm in 5106, the vehicle speed has decreased, so after starting timer 9, which has been set with a 2m5ec delay (expansion period) in advance (8108), check if the edge pulse has been input (5109). If the edge pulse is being input, the process returns to 5103; if the edge pulse is not being input, it is checked whether the timer 9 has turned off (
S110), if timer 9 is not off, 510
Return to 9. If timer 9 is off at 5110,
A digital vehicle speed value Vb=1/Cn is calculated and sent to the output interface 4. Output interface 4 is 5105
As in the case of , the digital vehicle speed value is converted into an analog signal voltage, sampled and held, and the power is amplified and outputted to the speedometer 100. After that, the process returns to 5106 again, and thereafter every 2m5ec until the next edge pulse is input. Execute the above operation.

Signal waveforms when the vehicle speed is decreasing will be explained with reference to the signal waveform diagram in FIG.

The pulse edge detection circuit 103 that receives the vehicle speed pulse from the vehicle speed sensor 100 outputs pulse signals at time to, t1, and t2. When the pulse signal is input to the controller 5 at time t1, the counted pulse element interval T
1 (=tO~t1) from counter 1 to delay register 2
is sent to ALU3 via pulse element interval T.
An analog signal voltage V1 (vehicle speed Va) inversely proportional to 1 is output to the speedometer 200.

Thereafter, at time t10 when the pulse element interval T2 currently being counted becomes equal to the reference pulse interval Cm - pulse element interval T1) set in the delay register 2, the timer 9 starts operating, and the timer 9 turns off. t11 (-t1
0+2m5ec), the current count value of counter 1 Cn=
An analog signal voltage V11 that is inversely proportional to t11-t1=Cm+2m5ec is output. Also, at time t12 (-tlO+4m5eC) when timer 9 turns off, the current count value of counter 1 Cn=t12-t1=Cm→-4m
An analog signal voltage v12 that is inversely proportional to 5ec is output. Thereafter, analog signal voltages V13 to V14 are output in the same manner at one time point t13 to t14.

After that, when a pulse signal is input at time t2, the pulse element interval T2 (= t2 - t1) is sent from the counter 1 to the ALU 3 via the delay register 2, and the pulse element interval T2 is stored in the delay register 2 as the reference pulse interval. set,
Then, a digital signal voltage v2 that is inversely proportional to the pulse element interval T2 is outputted from the output interface 4.

As described above, according to the analog meter drive circuit of this embodiment, when the next pulse elementary interval currently being measured exceeds the immediately preceding pulse interval, the analog signal voltage is inversely proportional to the current count value of the counter 1 every 2 m5ec. , the needle of the speedometer 200 can move more naturally than before.

Embodiment 2-15 = An analog meter drive circuit according to another embodiment of the present invention will be explained with reference to a block circuit diagram in FIG. 6 and a pulse waveform diagram in FIG. 7.

Similar to the device of the first embodiment, this analog meter drive circuit includes a counter 1, a delay register 2, an arithmetic logic circuit (AL
U) 3, it is composed of an output interface 4, a controller 5, a clock generator 6, and a timer 9, and a buffer register 7 for delaying the counted value is added between the counter 1 and the delay register 2. This device differs from the device of Example 1 in that

This buffer register 7 includes a register R1 that receives the counted value from the counter 1, a register R2 that receives the counted value from the register R1, a register R3 that receives the counted value from the register R2, and a register R4 that receives the counted value from the register R3. It consists of a register R5 that receives the counted value from the register R4, a register R6 that receives the counted value from the register R5, and a register R7 that receives the counted value from the register R6 and outputs the counted value to the delay register 2.

Each of the registers R1 to R7 is controlled by the controller 5 to operate as a shift register, and the pulse signal is transmitted from the pulse edge detection circuit 103 to the controller 5.
Each time the register is input, the count value of each register is shifted by nine stages of Rouges.

The vehicle speed sensor 100 shown in FIG. 2 outputs four vehicle speed pulses during one rotation as shown in FIG. Eight pulse signals are output at pulse unit intervals corresponding to the pulse width Ta and the pulse interval 1'-b. Each pulse element interval T1 to T8 divided by these eight pulse signals constitutes one rotation period of the vehicle speed sensor 100.

Therefore, the reference pulse interval Cm set in the delay register 2 in FIG. The numerical value Cn is this 1
It is compared with the pulse element interval before the rotation period. Therefore, it is possible to prevent the needle of the analog meter from erroneously moving due to variations in the width and spacing of the magnetic poles (N, S, N, S) of the vehicle speed sensor 100.

In addition, as the reference pulse interval Cm, in addition to the immediately preceding pulse element interval and the pulse element interval one rotation period before, as described above,
It is also possible to employ the average value of a plurality of adjacent pulse unit intervals that have already been input.

Example 3 The analog meter drive circuit of this example has a coefficient K, which will be described later.
This circuit has the same configuration as the analog meter drive circuit of the first embodiment (see FIG. 3), except that it has a register (not shown) for storing .

The operation of this analog meter drive circuit is as shown in the flowchart of FIG. 8, as shown in step 51 of FIG.
The difference from the flowchart in FIG. 4 is that steps 5112 and 5113 are added after step 11. However, the coefficient is set to 1 in 3101.

That is, at 5112, the reference pulse element interval Cm is set to 2m5eCx.
K is added to set the reference pulse element interval Cm, and 1 is added to the coefficient K at -18=5113 to set a new K.

Furthermore, in this embodiment, in 5106, the difference (Cn-Cm) between the next pulse element interval Cn currently being counted and the immediately preceding reference pulse interval Cm set in the delay register 2 is calculated, and the difference (Cn-Cm) is calculated. ) is larger than a predetermined value ΔK, the process proceeds to 8108, and otherwise the process proceeds to 8107.

However, .DELTA. is set to be somewhat wider than the slight variation (at normal running speed) in the pulse element interval due to variation in each magnetic pole (N, S, N, S).

Therefore, in this embodiment, each magnetic pole (N
, 5SNSS), the needle of the speedometer 200 can be prevented from changing as long as they are smaller than the difference (Cn-Cm).

[Effects of the Invention] As explained above, the analog meter drive circuit of the present invention includes a pulse element interval expansion detection means for detecting that the next pulse element interval currently being measured is wider than the immediately preceding reference pulse interval. , a pulse frequency calculating means for digitally outputting a pulse frequency signal that is inversely proportional to the immediately preceding pulse element interval during the period in which the expansion is not detected, and inversely proportional to the sum of the reference pulse interval and the expansion time during the expansion detection period; Therefore, when the next pulse element interval expands more than the previous reference pulse interval, a pulse frequency signal corresponding to the expansion can be output to the analog meter, and when the frequency of signal pulses decreases. A smooth analog signal can be output.

[Brief explanation of the drawing]

FIG. 1 shows an analog meter drive circuit 1 according to an embodiment of the present invention.
FIG. 2 is a block diagram of an automobile speed display device using this analog meter drive circuit, FIG. 3 is a block circuit diagram of the analog meter drive circuit of FIG. 1, and FIG. 3 is a flowchart showing the operation of the analog meter drive circuit of FIG. 3, FIG. 5 is a signal waveform diagram of the device of FIG. 1, and FIG. 6 is a block circuit diagram of the analog meter drive circuit of another embodiment of the present invention. , FIG. 7 is a signal waveform diagram of the analog meter drive circuit of FIG. 6. FIG. 8 is a flowchart showing the operation of the analog meter drive circuit according to the third embodiment of the present invention, and FIG. 9 is a signal waveform diagram of the conventional analog meter drive circuit. 1... Counter 1 (analog meter drive circuit) 2...
・Delay register (analog meter drive circuit) 3...A
LU (analog meter drive circuit) 4... Output interface (analog meter drive circuit) 5... Controller (analog meter drive circuit) 9.
...Timer (analog meter drive circuit) 10...Microcomputer (analog meter drive circuit) 100...Vehicle speed sensor 200...Speedmeter (analog meter) Patent applicant Nippondenso Co., Ltd.

Claims (1)

[Claims] (1) A pulse element interval measuring means that receives a pulse signal input at irregular intervals and measures the pulse element interval between each pulse of the pulse signal, and one or more pulse elements determined in advance. A reference pulse measuring means that calculates a reference pulse interval from the interval; and the next pulse to be inputted next time is not input within a time equal to the immediately preceding reference pulse interval, so that the next pulse elementary interval is less than the immediately preceding reference pulse interval. pulse element interval expansion detection means for detecting that the pulse interval has expanded; The pulse frequency calculation means digitally outputs a pulse frequency signal that is inversely proportional to the sum of the reference pulse interval and the extended interval, and the analog signal output means converts the pulse frequency signal into an analog signal and outputs it to the analog meter. Features an analog meter drive circuit.