JPH0216991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine vibration detection device,
In particular, the present invention relates to a device that can detect engine vibrations equivalent to those when mounted on a vehicle even when the engine is directly fixed without using a mount rubber for mounting on the vehicle.

In the inspection process after engine manufacture, the manufactured engine is actually operated and various engine characteristics are examined.

By the way, among the inspection items performed in such an inspection process, for example, there is an item to previously inspect how much the engine vibrates when the engine is mounted on a vehicle and idled.

Engine vibration detection when performing this inspection is
Conventionally, this has been done as shown in FIG. 1, for example.

That is, the engine fixing post 2 of the inspection table 1,
3, the engine 5 to which the transmission 4 is connected is fixed via mount rubbers 6 and 7 for mounting on the vehicle, so that the engine 5 can vibrate during engine operation in the same way as when mounted on the vehicle, and the engine 5 A piezoelectric acceleration pickup 8 as a vibration detector is attached to the upper side surface of the vibration detector.

Then, when the engine 5 vibrates when the engine 5 is operated in idle mode (for example, at 600 rpm with no load),
Since the piezoelectric acceleration pickup 8 generates a charge corresponding to the vibration, the charge amplifier 9 converts the generated charge into a voltage corresponding to the vibration, thereby obtaining a vibration output corresponding to the acceleration of the engine vibration. .

In addition, this type of vibration inspection is performed in advance to make optimal adjustments (for example, valve clearance adjustment, air-fuel ratio adjustment, etc.) before installing the engine in the vehicle, depending on the magnitude of the vibration output of the inspected engine.
This is to prevent the engine from vibrating too much especially during idling operation after being installed in a vehicle.

In addition, the transmission 4 is connected to the engine 5 so that it vibrates in the same way as when it is installed in a vehicle, but if the factory that manufactures the engine does not have a production mode that also assembles the transmission, Prepare a transmission similar to the one provided and connect that transmission to the engine during inspection.

By the way, in recent years, in order to automate the engine characteristic test mentioned above, various peripheral devices such as the starting device and piping for cooling water and exhaust gas necessary for engine operation are automatically connected to the engine on the test stand. It is considered to do.

However, to perform this automatic connection,
It is necessary to position the engine with high precision,
When the engine 5 is attached via the mount rubbers 6 and 7 as shown in Fig. 1, the mounting position of the engine 5 is not fixed, making it difficult to realize the automatic connection as described above. If it is fixed directly onto the inspection table 1 without using the mount rubbers 6 and 7, the engine 5 will no longer be able to vibrate, making it impossible to detect vibrations using the conventional piezoelectric acceleration pickup 8.

Therefore, the present invention provides an engine vibration detection device that can detect engine vibrations equivalent to those when mounted on a vehicle even when the engine is directly fixed on an inspection table without using a mounting rubber for mounting on a vehicle. The purpose is to automate engine characteristic inspections as described above.

To achieve this object, the present invention includes: a clamp member that cooperates with a support member that directly supports the engine to fasten the engine; and a rotation speed detector that outputs a rotation signal according to the rotation speed of the engine. a differentiation circuit that differentiates the rotational signal output from the rotational speed detector and outputs an acceleration signal corresponding to the rotational acceleration of the engine; This is an engine vibration detection device that includes a resonant circuit that converts vibration into a vibration waveform equivalent to vibration.

The engine vibration detection device according to the present invention has a device configuration based on the following principle.

In other words, engine vibration occurs when the pressure in the combustion chamber fluctuates due to unstable combustion, and the rotational speed of the crankshaft fluctuates in response to fluctuations in the force pushing the piston, that is, the rotational force of the crankshaft. As a result, a moment is generated that tries to rotate the engine body in the opposite direction to the direction of rotation of the crankshaft, and this generated moment is determined by the total mass of the engine body and transmission, etc., and the elastic modulus of the mount rubber. It is generated by exciting a mechanical vibration system.

Here, the excitation moment of the mechanical vibration system is IF,
When the moment of inertia of the rotating part of the engine is I and the rotational acceleration of the engine is α, the relationship I _F =I×α holds true.

Since the moment of inertia I in the above equation is constant, the excitation moment I _F is proportional to the rotational acceleration of the engine. The excitation moment that causes the vibration can be detected by the rotational acceleration of the engine that appears in proportion to the excitation moment.

Therefore, the rotational acceleration of this engine is obtained by differentiating the rotational signal according to the engine rotational speed, and the resonant circuit equivalent to the mechanical vibration system in the installed state of the engine is constructed using the rotational acceleration signal. Vibration is applied to obtain a vibration output equivalent to that of a mechanical vibration system from this resonant circuit.

Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the figure, the engine 5 is used to transport pallets 1.
The conveying pallet 10 is directly fixed to the inspection table 1 at the illustrated position on the inspection table 1 by a feeding device (not shown).

The engine 5 fixed to the transport pallet 10 is mounted on a bar 1 horizontally suspended above the inspection table 1.
The entire transport pallet 10 is pressed onto the inspection table 1 by a clamper 12 attached to the inspection table 1 and fixed rigidly.

In this way, the engine 5 can be accurately positioned on the inspection table 1, so that peripheral equipment (not shown) necessary for operating the engine 5 can be automatically connected to the engine 5.

Next, when the engine 5 is fixed in the illustrated position,
A starter gear 13 attached to the crankshaft of the engine 5 is closely opposed to an electromagnetic rotation speed detector 14 attached in advance on the inspection table 1 so that the distance from the top of the teeth is 2 to 3 mm.

This electromagnetic type rotational speed detector 14 is a known detector in which a voltage generating coil 14c is wound around a probe 14b fixed to a permanent magnet 14a, as shown in FIG.
When the starter gear 13 attached to the crankshaft rotates in the direction of arrow A by operating the starter ring, the magnetic flux of the voltage generating coil 14c changes every time the top of its teeth passes the tip of the probe 14b. Therefore, a waveform rotation signal S ₁ having a frequency proportional to the rotation speed of the engine 5 is output from the voltage generating coil 14c.

Returning to FIG. 2, the F/V converter 15 frequency-voltage converts the waveform rotation signal S ₁ output from the rotation speed detector 14 to produce a rotation voltage signal with a voltage level proportional to the rotation speed of the engine 5. Output S ₂ .

The differential amplifier circuit 16 includes, for example, a capacitor C ₁ , a resistor R ₁ , and an operational amplifier OP ₁ as shown in FIG.
It differentiates and amplifies the rotation voltage signal S ₂ output from the F/V converter 15, and generates an acceleration signal S ₃ ((S ₃ ∝ Excitation moment) is output.

The impedance converter 17 is constituted by a voltage follower circuit consisting of an operational amplifier _OP2 , as shown _in FIG. Convert to ₄ .

The equivalent resonant circuit ₁₈ is constituted by a known series resonant circuit consisting of a resistor R ₂ , a capacitor C ₂ , and a coil L, as shown in FIG. ₂ and the values of coil L are set as follows.

In other words, the vibration equation of the mechanical vibration system of the engine (rotating machine) 5 when the engine 5 is mounted on a vehicle and operated is as follows: θ is the rotation angle (corresponding to displacement), and I is the moment of inertia (corresponding to mass). , the damping resistance is R _M , the compliance is λ (the reciprocal of the spring constant k), the excitation moment (corresponding to force) is I _F , and the time is t, it can be expressed as shown in equation (1). .

Id ₂ θ/dt ₂ +R _M dθ/dt+θ/λ=I _F ………(1) On the other hand, the vibration equation of the resonant circuit in Fig. 4 is expressed by equation (2), where Q is the charge and E is the voltage. It can be expressed as shown in

Ld ₂ Q/dt ² +R ₂ dQ/dt+Q/C ₂ =E......(2) Comparing equations (1) and (2), they are equivalent equations, so from equation (1), the mechanical vibration system can be calculated. Find the resonance frequency ₀ = 1/2π√ and the damping rate α = R _M /2I,
Resonant frequency ₀ of each determined resonant circuit = 1/2π√
Each circuit constant is set to match the values of LC ₂ and attenuation rate α=R ₂ /2L, respectively.

In this way, the equivalent resonant circuit 18 becomes equivalent to a mechanical vibration system when the engine 5 is mounted in a vehicle. Therefore, if this equivalent resonant circuit 18 is excited by the acceleration signal _S4 output from the impedance converter 17, it will be in a vibration state equivalent to a mechanical vibration system, and from equations (1) and (2), As is clear, for example, a vibration output S ₅ of a voltage proportional to the vibration acceleration of the engine 5 is generated at both ends of the coil L.

Note that a vibration output with a voltage proportional to the vibration speed of the engine 5 is connected to both ends of the resistor _R2 , and a capacitor
Since vibration outputs with voltages proportional to the vibration displacement of the engine 5 are generated at both ends of C ₂ , it is possible to select the output necessary for evaluating vibrations.

Therefore, as shown in Fig. 2, even if the engine 5 is fixed directly on the inspection table 1 without using the mount rubber 6 so that it cannot vibrate, it is possible to detect the same engine vibration as when it is installed in a vehicle. If engine vibration is evaluated based on the results, the engine can be optimally adjusted in advance based on the evaluation results.

Moreover, by fixing the engine in this way, the fixed position of the engine is fixed, which not only makes it possible to automatically connect the peripheral equipment necessary for operating the engine, but also enables automatic connection of peripheral devices necessary for engine operation, as shown in Figures 2 and 3. If an electromagnetic type rotational speed detector 14 is used, there is no need to attach and detach the detector every time the engine to be inspected is replaced.

When the engine 5 is operated at 600 rpm with no load, the vibration velocity waveform obtained by the device of the above embodiment is shown in FIG. 5A, and the vibration acceleration signal obtained by the conventional device shown in FIG. 1 is integrated. The vibration velocity waveforms obtained are shown in FIG. 5B.

As is clear from both waveforms, the manner in which the vibration speed changes is substantially the same, so it can be seen that the vibration tendency of the engine 5 mounted on the vehicle can be determined even from the vibration output obtained by the apparatus of the above embodiment.

Further, in the above embodiment, an example was described in which an electromagnetic type rotation speed detector that detects the rotation of the engine's starter gear is used, but the invention is not limited to this. The ignition signal may be input to the F/V converter 15 shown in FIG. 2 using a circuit that extracts the ignition signal, or a tachogenerator as a rotational speed detector may be attached to the crankshaft of the engine 5 to detect the ignition signal. Voltage to F/V converter 15
It is also possible to directly input the signal to the differential amplifier 16 without going through it.

Further, in the above embodiment, the case where no transmission is attached to the engine has been described, but detection is possible in the same way even when the transmission is attached.

However, since the starter gear is hidden when the transmission is installed, it is necessary to use another detector as described above instead of the rotational speed detector.

As explained above, according to the present invention, even when the engine is fixed directly on the inspection table without using the mount rubber for mounting on the vehicle, it is possible to detect the same engine vibration as when it is mounted on the vehicle. It is now possible to automatically connect peripheral equipment such as starters and cooling water piping to a fixed engine.
Thereby, it is possible to automate the engine characteristic inspection.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional engine vibration detection device, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is an electromagnetic type rotation speed detection device in Fig. 2. FIG. 4 is a circuit diagram showing a specific example of the differential amplifier circuit 16, impedance converter 17, and equivalent resonant circuit 18, and FIG. 5 A and B are the same as those in FIG. A waveform diagram showing the vibration velocity waveform obtained by the device of the embodiment and the vibration velocity waveform obtained by the conventional device, FIG.
1 is a waveform diagram showing output signal waveforms indicated by S1 to S5, which appear identically to waveform S4 and waveform S3. 1...Inspection table, 5...Engine, 6, 7...Mount rubber, 10...Transportation pallet (supporting member), 12...Clamper, 13...Starting gear, 14...Electromagnetic type rotation speed detector, 16
... Differential amplifier circuit, 18 ... Equivalent resonant circuit.

Claims (1)

[Claims] 1 A clamp member that cooperates with a support member that directly supports the engine to fasten the engine; a rotation speed detector that outputs a rotation signal according to the rotation speed of the engine; and a rotation speed detector that outputs a rotation signal according to the rotation speed of the engine. a differentiation circuit that differentiates a rotational signal and outputs an acceleration signal corresponding to the rotational acceleration of the engine; and a resonance that converts the acceleration signal from the differentiation circuit into a vibration waveform equivalent to mechanical vibration in the mounted state of the engine. An engine vibration detection device having a circuit.