JPS6410768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine friction torque measuring device, and particularly to an engine friction torque measuring device suitable for measuring changes in friction torque of an automobile engine for each crank angle. The present invention relates to a friction torque measuring device.

[Conventional technology]

In recent years, there has been a strong demand to improve the fuel consumption of automobile engines in order to save energy resources. Therefore, improvement measures such as improving fuel and reducing friction have been attempted and put into practical use. In order to reduce engine friction, it is necessary to accurately measure friction torque, and conventionally, friction torque has been measured by motoring the engine with a dynamometer and from the dynamometer reading at that time.

[Problem to be solved by the invention]

However, the friction torque when the engine is motored using a dynamometer is different from the friction torque when the engine is actually ignited and fired.
Moreover, only the average value of friction torque can be measured from the dynamometer reading, and changes in friction torque with each crank angle cannot be measured, so the dependence of friction torque on cylinder pressure and piston speed cannot be analyzed. No effective measures could be taken to reduce friction loss.

In order to eliminate these shortcomings, attempts have been made to measure the reaction force applied to the piston liner and the torque applied to the bearing, and to measure and analyze the friction between the piston rings, the piston and the liner, and the friction of the shaft. . However, this method of partially measuring the frictional force has a problem in that it is not possible to measure the frictional torque of the entire engine in its assembled state.

An object of the present invention is to provide an engine friction torque measuring device that can measure changes in friction torque for each crank angle with high precision.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a crank angle sensor that detects the crank angle of an engine;
a pressure sensor for detecting the internal cylinder pressure of the engine; a means for determining the rotational speed of the engine based on the crank angle signal detected by the crank angle sensor; In addition to calculating the indicated torque for each angle, the inertia force for each crank angle is calculated based on the crank angle and rotational speed, and the inertia force is subtracted from the indicated torque to calculate the friction for each crank angle during no-load operation. The present invention proposes an engine friction torque measuring device comprising a means for determining torque.

The present invention also provides a torque detection means for detecting torsional torque applied to a drive shaft of an engine, a crank angle sensor for detecting a crank angle of the engine, a pressure sensor for detecting internal cylinder pressure of the engine, and means for determining the rotational speed of the engine based on the crank angle signal detected by the crank angle sensor; and means for calculating the indicated torque for each crank angle based on the crank angle, cylinder internal pressure, and rotational speed; Based on this, calculate the inertia force for each crank angle, calculate the net torque applied to the drive shaft based on the torsion torque, subtract the inertia force and net torque from the indicated torque, and calculate the inertia force for each crank angle during load operation. means for determining friction torque for each crank angle;
This paper proposes an engine friction torque measuring device consisting of:

[Effect]

The principle of the present invention will be explained below. Assuming that the crankshaft is a rigid body, the following relationship holds between the inertia force and torque during no-load operation of the engine.

Idω/dt=Ti−Tf (1) where I is the engine inertia moment, ω is the rotational speed, Ti is the indicated torque, and Tf is the friction torque. By transforming this equation, the following equation is obtained.

Tf=Ti−Idω/dt…(1)′ Of these, the indicated torque Ti of the multi-cylinder engine is:
It can be calculated from the cylinder internal pressure Pz (z is the cylinder number) applied to the piston of each cylinder and the reciprocating inertia force as shown in the following equation.

Ti= _n 〓 ^z=1 (Pz−1/A ² W/g d ² Vz/dt ² ) dVz/dθ …(2) Here, m is the number of cylinders, A is the projected area of the top of the piston, and W is the reciprocating inertia. The weight, g is the gravitational acceleration, Vz is the volume of the z-th cylinder, and θ is the crank angle.

From equations (1)′ and (2), the friction torque Tf during no-load operation of the engine is finally expressed by the following equation.

Tf= _n 〓 〓 ^z=1 {Pz−1/A ² W/g(ω ² d ² Vz/dθ ² +ωdω/dθ
dVz/dθ)}dVz/dθ−Iωdω/dθ…(3) Therefore, if the cylinder pressures P ₁ to _{P n} of all cylinders and the engine rotational speed ω are symmetrical to each crank angle θ and detected simultaneously in time series, , From this equation (3), the friction torque Tf for each crank angle θ during no-load operation is calculated.

On the other hand, assuming that the crankshaft is a rigid body, the following relationship holds between inertia force and torque during engine load operation.

Idω/dt=Ti−Tf′−Te (4) Here, Tf′ is the friction torque during engine load operation, and Te is the net torque applied to the drive shaft. By transforming this equation, the following equation is obtained.

Tf'=Ti-Idω/dt-Te (4)' From equations (4)' and (2), the friction torque Tf' during engine load operation is expressed by the following equation.

Tf′= _n 〓 〓 ^z=1 {Pz−1/A ² W/g(ω ² d ² Vz/dθ ² +ωdω/dθ
dVz/dθ)}dVz/dθ−Iωdω/dθ−Te…(5) Therefore, the cylinder pressures P ₁ to P _n of all cylinders and the engine rotational speed ω are simultaneously detected in time series with symmetry to each crank angle θ. Then, from this equation (5), it is possible to calculate the friction torque Tf for each crank angle θ during load operation.

Note that the net torque Te can be calculated by detecting the torsional torque of the drive shaft and correcting the effects of torsional vibration and control characteristics of the dynamometer.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

A first embodiment of the present invention is a device that measures changes in friction torque for each crank angle during no-load engine operation. As shown in FIG. 1, this device includes a pressure sensor 12, which is arranged in each cylinder of an engine 10 and is composed of a piezoelectric transducer, for example, to detect the internal pressure Pz of each cylinder, and the output of the pressure sensor 12 is processed by arithmetic processing. A signal converter 14 that converts into a suitable signal, and a crank angle sensor 16 that is attached to the tip of the crankshaft 10a of the engine 10 and detects the crank angle θ.
Based on the output of the signal converter 14 and the output of the counters 18 and 20, two counters 18 and 20 alternately count the output of the crank angle sensor 16 and output the crank angle θ and the engine rotation speed ω, It is comprised of an arithmetic processing unit 22 that calculates the change in friction torque Tf for each crank angle during no-load engine operation using the above equation (3), and a printer 24 that prints the output of the arithmetic processing unit 22.

For example, as shown in detail in FIG. 2, the signal converter 14 includes a charge amplifier 14a that converts the charge output from the pressure sensor 12 into a voltage, a DC amplifier 14b that amplifies the output of the charge amplifier 14a, and a DC amplifier 14b that amplifies the output of the charge amplifier 14a.
It consists of a sample hold circuit 14c that samples and holds the output of the amplifier 14b, and an A/D converter 14d that converts the output of the sample hold circuit 14c into a digital signal and outputs it to the arithmetic processing unit 22.

As shown in FIGS. 3 and 4, the crank angle sensor 16 has 3,600 crank angle detection slits 26a (at 0.1° intervals) and one top dead center detection slit 26b formed near the outer periphery of the engine. Disc 2 fixed to the tip of crankshaft 10a of 10
6, two sets of light emitting diodes 28a and photodiodes 30a fixedly arranged above and below so as to sandwich the disk 26 in order to detect the passage of the crank angle detection slit 26a, and the passage of the top dead center detection slit 26b. In order to do this, two sets of light emitting diodes 28b and photodiodes 30b are fixedly arranged above and below to sandwich the disk 26.
and has. Each photodiode 30a, 30b
At the tip of the light-receiving part, there are slit plates 32a, 3 having slits in the same shape as the slits in the disk 26.
2b is provided, and a disk 26 and a slit plate 3 are provided.
2a and 32b are detected by photodiodes 30a and 30b, respectively. here,
The reason why two sets of photoelectric detectors each consisting of a light emitting diode and a photodiode are provided axially symmetrically with respect to the rotation axis is to compensate for a pulse interval error caused by wobbling of the slit in the direction of the rotation axis. That is,
If the disk 26 becomes unable to rotate in a plane perpendicular to the rotating shaft due to installation error on the rotating shaft or engine vibration, the disc 26 will shift from side to side as shown in FIG. will be rotated. Therefore, the projected area of the slit onto the photodiode changes slightly, the output level of the photoelectric detector changes, and an error occurs in the phase of the obtained waveform and thus in the pulse interval.

Now, when a part of the disk 26 approaches, for example, the photodiode side from a predetermined position, the opposite side across the rotation axis approaches the light emitting diode side, so that the disk 26 is placed at a position axially symmetrical to the rotation axis. When the outputs of the two sets of photoelectric detectors are combined, a pulse signal of a constant level is always obtained, and no error in phase or pulse interval is caused.

In order to prevent changes in engine performance due to installing the crank angle sensor 16 on the engine, its friction torque and moment of inertia should be reduced from approximately 10 ^-4 of the engine's friction torque and moment of inertia.
It is said that it should be around 10 ^-5 . Note that since the signal every 0.1° corresponding to the crank angle is as fast as approximately 60 KHz at an engine speed of 1000 rpm, it is easily affected by electrical noise. Therefore,
An amplifier is provided inside the crank angle sensor 16, and the output impedance is made sufficiently small to create a structure that is less susceptible to noise.

FIG. 5 shows the accuracy test results obtained by rotating the disk 26 with a flywheel (approximately 0.1 Kgcmsec ² ) having a sufficiently large moment of inertia compared to the friction torque of the crank angle sensor 16. The measurement error of the crank angle sensor 16 was calculated by measuring a 2° interval at a flywheel speed of 200 rpm, which corresponds to a 10° interval measurement at an engine speed of 1000 rpm, and assuming that the deceleration during one revolution is constant. The maximum measurement error was 6×10 ^-4 deg (accuracy of 0.03% for 2°), and the target accuracy was achieved.

Next, the operation of this embodiment will be explained. As the engine rotates, the pressure inside the cylinder Pz is determined by the pressure sensor 12 at every predetermined crank angle, for example, every 2 degrees of crank angle.
is detected and input to the arithmetic processing unit 22 in time series via the signal converter 14. On the other hand, as shown in FIG. 6, the two counters 18 and 20 start measuring from the intake top dead center signal, and alternately measure the signal for every 100 pulses at every 0.1° crank angle (10° crank angle). The measurement of the time interval of angle) and the output of the measured value to the arithmetic processing unit 22 are repeated, and the engine rotational speed ω within the 10° interval is continuously output to the arithmetic processing unit 22. A reference signal from a crystal oscillator with a frequency of 50 MHz is used to measure the time of the 10° interval by the counters 18 and 20, and a resolution of about 10 ⁻⁴ deg is obtained at an engine rotation speed of 1000 rpm. 10゜ section
The reason why we decided to measure with 100 pulses every 0.1° is because
When the output level of the photodiode fluctuates due to vibration of the disk 26, etc., the trigger point during waveform shaping also fluctuates, resulting in an error in time interval measurement. This is because the error will be smaller if the frequency is divided after detection. In order to match the engine rotational speed ω for every 10 degrees of crank angle detected in this way with the cylinder pressure Pz obtained every 2 degrees of crank angle as the output from the pressure sensor 12, The engine rotation speed data is converted into engine rotation speed ω at every 2 degrees of crank angle by an interpolation method using a cubic curve that passes through three points of the engine rotation speed data every 10 degrees and shares a tangent at both ends.

Note that the differential value of this cubic curve is used as the value of the engine rotational speed dω/dθ in the above equation (3).

Detecting the cylinder pressure Pz, indicated torque Ti, and engine rotational speed ω of a 4-cycle in-line 4-cylinder gasoline engine using the device of the first embodiment, (3)
FIG. 7 shows an example of a change in the friction torque Tf calculated using the formula for each crank angle θ. The average rotational speed of the engine is 600 rpm, the average air-fuel ratio is 13, and the ignition timing is 5° BTDC (Before Top Dead Center).
That is, 5 degrees before top dead center, engine ignition order is 3rd,
The order is No. 4, No. 2, and No. 1 cylinder. Thin line A in FIG. 7 shows the friction torque Tf for every 2 degrees of crank angle, which is directly calculated from equation (3). As mentioned above, although the target accuracy was obtained in the accuracy test of the crank angle sensor 16 alone, the friction torque Tf shown in Fig. 7 has many waveform fluctuations, and moreover, there are many waveform fluctuations near the top dead center of each cylinder. is a negative value. This is considered to be a vibration error of the disk 26 due to engine vibration, so the arithmetic processing unit 22 further calculates the friction torque Tf.
The waveform of was smoothed. The result is thick line B in Figure 7.
It is. In the diagrams below, this smoothed friction torque Tf is used.

First, Fig. 8 shows an example of measurement of the crank angle change in friction torque Tf when the lubricating oil temperature is changed to 30°, 60°, and 90°C. In the figure, solid line C indicates lubricating oil temperature 30
℃, if the dashed line D is the lubricating oil temperature of 60℃,
Broken line E indicates the case where the lubricating oil temperature is 90°C. Note that the operating conditions of the engine are the same as in the case of FIG.
A comparison of the average friction torque Tf is shown at the right end of FIG.
From this figure, it can be seen that as the lubricant temperature increases, the friction torque decreases, and the rate of decrease is approximately constant during the cycle. Furthermore, the friction at the top and bottom dead centers of the piston is almost zero, and reaches its maximum value in the middle. This waveform closely approximates the shape of the frictional torque between the piston and piston ring and cylinder liner. Therefore, under no-load, low-speed operating conditions,
The friction of the assembled engine body is quite close to the form of the friction torque between the piston and piston ring and cylinder liner. Therefore, under no-load, low-rpm continuous operation conditions, the friction between the piston and piston ring and cylinder accounts for a considerable proportion of the friction in the assembled engine body, and this friction is dependent on the piston speed. It is thought that the influence of

Figure 9 shows the measured changes in friction torque Tf for each crank angle when the average engine speed was changed to 600, 700, and 800 rpm. In the figure, a solid line F indicates an average engine rotation speed of 600 rpm, a dashed line G indicates an average engine rotation speed of 700 rpm, and a broken line H indicates an average engine rotation speed of 800 rpm.
Other operating conditions are the same as in the case of FIG. It can be seen that in such a low rotation range, the normal friction torque Tf hardly changes even if the engine rotation speed increases. However, the amplitude of the intra-cycle change in friction torque Tf becomes smaller as the average engine speed increases. This is considered to be because as the average engine rotational speed increases, the friction between the piston and the piston ring decreases, and conversely, the friction at parts such as bearings that slide at approximately constant speed increases.

Cylinder pressure Pz and friction torque Tf when the average ignition timing of the engine is changed from 10° BTDC, i.e., 10° before top dead center, to -10° BTDC, i.e., 10° after top dead center.
FIG. 10 shows an example of measurement of changes in each crank angle. In the diagram, solid line I is the average ignition timing
In the case of 10゜BTDC, the broken line J is the average ignition timing -
This is the case of 10°BTDC. Since the thermal efficiency is lower on the retarded side of ignition timing, a larger amount of air is required at the same rotation speed, and it can be seen that both the manifold pressure and the maximum pressure in the cylinder are higher on the retarded side. The intra-cycle change in friction torque seems to be strongly influenced by piston speed and cylinder pressure, but the increase in average friction torque Tf is small.

The above measurement results show that the friction torque during no-load operation of a multi-cylinder engine decreases as the lubricating oil temperature increases, and that the rate remains almost constant during the cycle, and that the effects of piston speed and cylinder pressure are I knew it would be received very well.

As described above, according to the first embodiment, it is possible to measure with high precision the changes in friction torque for each crank angle during no-load operation of the engine, and to determine the dependence of friction on cylinder pressure, piston speed, etc. in detail. It provides useful data for analysis.

In the above embodiment, the present invention is applied to the measurement of the crank angle change in friction torque during no-load operation of a multi-cylinder engine. It is also possible to determine the change in friction torque for each crank angle during operation. A second embodiment of the present invention for this purpose is shown in FIG. In this embodiment, in addition to the first embodiment, a dynamometer 40 is connected to the drive shaft of the engine 10, a torque meter 42 is arranged between the dynamometer 40 and the engine 10, and the torque is detected by the torque meter 42. Calculate the instantaneous net torque Te by correcting the effects of torsional vibration and control characteristics of the dynamometer 40 on the drive shaft torsional torque, and (5)
The friction torque Tf' during load operation is determined using the formula. In the figure, 44 is a DC amplifier that amplifies the output of the torque meter 42, and 46 is a DC amplifier that amplifies the output of the torque meter 42.
A sample and hold circuit samples and holds the output of the DC amplifier 44, 48 is an A/D converter that converts the output of the sample and hold circuit 46 into a digital signal, and 50 measures drive shaft torsion torque of the output of the A/D converter 48. Based on the value and the output of the pressure sensor 12 obtained via the signal converter 14 and the output of the crank angle sensor 16 obtained via the counters 18 and 20 in the same manner as in the first embodiment, the equation (5) is used to calculate the value during load operation. This is an arithmetic processing device that calculates friction torque Tf'. Regarding other points and effects, please refer to the above 1.
Since it is almost the same as the embodiment, the explanation will be omitted.

According to the second embodiment, changes in friction torque for each crank angle during engine load operation can be measured with high precision.

〔Effect of the invention〕

According to the present invention, changes in friction torque for each crank angle can be measured with high precision during engine no-load operation or engine load operation, and it is possible to analyze in detail the dependence of friction on cylinder pressure, piston speed, etc. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of an engine friction torque measuring device according to the present invention installed in an engine, and FIG. 2 is a block diagram showing the configuration of a signal converter of a pressure sensor of the embodiment. FIG. 3 is a vertical cross-sectional view showing the configuration of the crank angle sensor of the above embodiment, FIG. 4 is a front view showing a part of the disk of the crank angle sensor, and FIG. 5 is the accuracy test result of the crank angle sensor. Figure 6 is a diagram showing the waveforms of each part of the crank angle sensor.
FIG. 7 shows the cylinder pressure of a 4-cycle in-line 4-cylinder gasoline engine measured using the first embodiment;
Figure 8 is a diagram showing changes in indicated torque, engine speed, and friction torque at each crank angle. Figure 8 is a diagram showing changes in friction torque at each crank angle and the average value when the lubricating oil temperature is changed. Figure 9 10 is a diagram showing the change in friction torque for each crank angle and the average value when the average engine speed is changed, and Figure 10 is a diagram showing the change in cylinder pressure and friction torque for each crank angle when the ignition timing is changed. FIG. 11 is a block diagram showing a state in which a second embodiment of the engine friction torque measuring device according to the present invention is attached to an engine. 10...Engine, 12...Pressure sensor, 14
... Signal converter, 16 ... Crank angle sensor, 1
8, 20... Counter, 22, 50... Arithmetic processing unit, 40... Dynamometer, 42... Torque meter.

Claims (1)

[Claims] 1. A crank angle sensor that detects the crank angle of the engine; a pressure sensor that detects the internal cylinder pressure of the engine; and a system that detects the rotational speed of the engine based on the crank angle signal detected by the crank angle sensor. calculating the indicated torque for each crank angle based on the crank angle, cylinder internal pressure, and rotational speed, and calculating the inertia force for each crank angle based on the crank angle and rotational speed to obtain the indicated torque; and means for subtracting the inertial force from the inertial force to obtain the friction torque for each crank angle during no-load operation. 2. Torque detection means for detecting torsional torque applied to the drive shaft of the engine; a crank angle sensor for detecting the crank angle of the engine; a pressure sensor for detecting the internal cylinder pressure of the engine; and the crank angle sensor. means for determining the rotational speed of the engine based on the detected crank angle signal; and means for calculating the indicated torque for each crank angle based on the crank angle, cylinder internal pressure, and rotational speed, and calculating the indicated torque based on the crank angle and rotational speed. In addition to calculating the inertia force for each crank angle, the net torque applied to the drive shaft is calculated based on the torsion torque, and the inertia force and net torque are subtracted from the indicated torque to calculate the inertia force for each crank angle during load operation. An engine friction torque measuring device comprising means for determining friction torque.