JP3408318B2 - Tachometer drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tachometer driving circuit used as a highly responsive engine tachometer, such as a tachometer for a motorcycle engine. 2. Description of the Related Art A conventional tachometer drive circuit of this type is, for example, shown in a block diagram of FIG. In this tachometer drive circuit, after a rotation signal from an engine is shaped into a predetermined waveform by a waveform shaping circuit 1, the rotation signal is converted into an electric signal by an FV conversion circuit 3 through a monostable multivibrator 2. The electric signal is used to drive the cross coil driving circuit 4, that is, the engine tachometer, to display the number of revolutions of the engine. [0004] However, in the case of a tachometer for a motorcycle, for example, in which the rotational speed of the engine is drastically fluctuated, the response of the engine is fast, so that the tachometer has a rapidly displaced (fluctuated) pointer. It was difficult to read the indicated value by using. More specifically, the operation of a tachometer having a fast response will be described in detail with reference to the characteristic diagram of FIG. 2. As shown in FIG. 2, the horizontal axis indicates time, the vertical axis indicates engine speed, and the solid line indicates Assuming that the engine speed rapidly increases from 0 to the maximum speed, the indicated value displayed on the tachometer that operates (drives) in accordance with the engine speed at this time is also indicated by a two-dot chain line. In a short time (T), the tachometer suddenly rises in a short time (T), and if the engine speed is rapidly reduced, the tachometer indicated value also rapidly falls in a short time (T1). The rise time (T), that is, the response time (T) of the tachometer is generally required to be, for example, 0.2 to 0.8 seconds (S). As the time (T) is increased, the fall time (T1) is also increased as described above, so that the pointer of the tachometer operates sensitively (fast vibration), which makes it difficult to read the indicated value by the pointer. However, there is a drawback that needle run-out occurs at low rotation. In order to solve this drawback, the tachometer drive circuit is provided with, for example, a delay circuit and the like, as shown by a dashed line in FIG. It is conceivable that the reading of the tachometer by the tachometer can be made easier, but in this case, the tachometer's reading becomes lower, especially when the tachometer's responsiveness is poor (low) and the engine speed drops. Since the maximum value is not shown, an instruction error (R) is generated, and a disadvantage occurs in that an accurate rotational speed instruction cannot be performed. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks in the conventional tachometer driving circuit. The tachometer has a fast rise time and good responsiveness. It is an object of the present invention to provide a tachometer drive circuit which makes it easier to read an indicated value by a tachometer pointer by reducing a response time by decreasing a fall time, and which can indicate a highly accurate indicated value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments shown in the drawings. FIG. 3 shows a block diagram of the circuit of this embodiment.
FIG. 4 shows a detailed diagram of the circuit configuration. Reference numeral 1 denotes a waveform shaping circuit, 2 denotes a monostable multivibrator, and 4 denotes a cross coil driving circuit, which are the same as those shown in the conventional example. Reference numeral 5 denotes an FV conversion circuit according to the present embodiment,
The FV conversion circuit 5 includes a monostable multivibrator 2
And a rising signal processing circuit 6 and a falling signal processing circuit 7 to which an output from the monostable multivibrator 2 is input. A time constant setting circuit 8 is connected to the rising signal processing circuit 7. An arithmetic circuit 9 composed of an IC includes the FV conversion circuit 5 and the cross coil driving circuit. Reference numeral 10 denotes an indicator (tachometer). The configuration of the present embodiment has been described above. Next, the operation will be described. In the arithmetic circuit 9, a frequency signal corresponding to the engine speed is input from the waveform shaping circuit 1 and the operation circuit 9 is controlled according to the engine speed. The drive signal of the indicator 10 is output to the indicator 10. The rise time and the fall time of the indicator 10 according to the rotation speed of the engine are set in the arithmetic circuit 9. Since the time constant setting circuit 8 is connected, the response speed of the indicator is set by the time constant setting circuit 8, the rising signal processing circuit 6, and the falling signal processing circuit 7. The response speed is set so that when a rising signal is input from the engine, the hands are operated at a high response speed (T) in FIG. 2 and a falling signal is input from the engine. Sometimes, the slow response speed (T
Set so that the pointer is operated in 2). Accordingly, when the rotation of the engine changes from a low speed to a high speed as shown by a broken line in FIG. 2, the response speed of the indicator is high, and a high-precision instruction can be obtained in a high speed rotation range. When the rotation of the engine changes from a high speed to a low speed, the change of the pointer in the indicator becomes gradual, so that the tachometer is read easily with the indicated value. As described above, the present invention has an arithmetic circuit for inputting a frequency signal corresponding to the engine speed and outputting an analog indicator drive signal having a level corresponding to the frequency. Start up from the engine in the tachometer drive circuit
When a beam signal is input, the pointer is
Slow response speed when a falling signal is input
The time constant setting circuit is connected so that the pointer operates with
According to the tachometer drive circuit , the response of the tachometer when the engine shifts from low-speed rotation to high-speed rotation can be made faster (rapid), and the engine can be driven from high-speed rotation to low-speed. Since the response of the tachometer at the time of transition to rotation can be made slow (gradual), the response at the time of increase in the engine rotation speed is good, and the tachometer indicated value can be easily read.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a conventional tachometer drive circuit. FIG. 2 is a characteristic diagram showing a relationship between an engine speed and an instruction value. FIG. 3 is a block diagram showing a tachometer driving circuit according to the embodiment of the present invention. FIG. 4 is a connection diagram showing details of a tachometer driving circuit according to the embodiment of the present invention. [Description of Signs] 1 ... waveform shaping circuit 2 ... monostable multivibrator 4 ... cross coil driving circuit 5 ... FV conversion circuit 6 ... rising signal processing circuit 7 ... falling signal processing circuit 8 ... time constant setting circuit 9 ... Arithmetic circuit 10 Indicator

Claims (1)

(57) [Claim 1] A tachometer drive circuit including an arithmetic circuit for inputting a frequency signal corresponding to an engine speed and outputting an analog indicator drive signal at a level corresponding to the frequency. , When a rising signal is input from the engine,
The pointer operates at a fast response speed and a falling signal is input.
The time constant so that the pointer operates at a slow response speed.
A tachometer to which a setting circuit is connected
Drive circuit.