JPS6226699B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a torque detection device for a dynamometer that improves the responsiveness of torque control. Recently, running resistance simulations are often performed using dynamometers for engine tests, acceleration/deceleration tests using bench and chassis dynamometers, and exhaust gas mode tests. When performing this running resistance simulation, mechanical inertia simulation using an inertia disk has conventionally been used to provide the acceleration resistance component of the running resistance (consisting of steady running resistance and acceleration resistance). However, since the number of inertia disks would be large to make it arbitrarily variable, there has recently been a tendency to adopt electrical inertia simulation in order to reduce costs and make it more compact. This electrical inertia simulation detects the acceleration acting on the dynamometer and attempts to cause the dynamometer to generate a torque proportional to this acceleration. In this case, the dynamometer is controlled by the torque control mode. The command signals for this include steady running resistance (resistance including rolling resistance and air resistance), acceleration resistance (resistance that acts on inertia,
This corresponds to the torque that corresponds to the amount of torque that is intended to be compensated for electrically. The steady running resistance command signal is generated by a separately installed running resistance setting device, since this resistance is a function of rotational speed. With this steady running resistance, the rotational speed does not suddenly change, so there is no need to increase the response speed of torque control that much. In comparison, the command signal for the acceleration resistance mentioned above needs to be given in proportion to the rotational speed change rate, so unless the response speed of torque control is made extremely high, control accuracy will decrease and electrical inertia simulation becomes unable to achieve its objectives. For example, the required torque control response speed is currently said to be 0.1 seconds at 63% response. However, although such response speed does not pose a particular problem in the control stage using a thyristor or the like, it poses a problem in the torque detection stage in a conventional torque detection mechanism. Here, a conventional torque detection device will be briefly explained. FIGS. 1a and 1b show an example of a torque detection mechanism, and FIG. 2 shows a block configuration. In the conventional device, as shown in FIG. 1a, an oscillator 5 is supported by a hydraulic flotation device 4.
A load cell 9 has the tip of a torque arm 6 protruding from the top of the bed 1 fixedly mounted on the bed 1 via a vibration isolating rubber 10.
It is connected to the receiving arm 8 of. Torque arm 6
As shown in FIG. 1b, the connection structure between the torque arm 6 and the receiving arm 8 is such that a knife edge 7 is provided protruding from the torque arm 6, and a receiving hole 8a is provided on the receiving arm 8 side to loosely pass through the knife edge 7. is inserted into the receiving hole 8a with a gap g.
Therefore, the torque generated in the rocker 5 is transmitted to the load cell 9 via the torque arm 6, knife edge 7, receiving hole 8a, and receiving arm 8. The output of the load cell 9 is transmitted to a torque indicator 11 through a distortion amplifier 11 and an amplifier 12, as shown in FIG.
3, while it is taken out as the torque control output A. In addition, in the figure, 2 is the rotation axis, 3
5a is a field coil, and 5b is a commutator coil. The knife edge 7 is provided so that a bending moment applied to the load cell 9 will not cause a change in zero point or a change in sensitivity, resulting in a decrease in accuracy. In addition, knife edge 7 and receiving arm 8
The gap g between the oscillator 5 and the dynamometer is provided to prevent bending moments from occurring due to axial and perpendicular displacements of the oscillator 5, the tightness of fixing bolts, etc., and uneven temperature changes in the dynamometer itself. It is something that Furthermore, the vibration isolating rubber 10 is provided to soften and absorb the impact load applied to the load cell 9. However, in the above-mentioned conventional device, it has been difficult to increase the accuracy of the response speed for torque control because detection errors and disturbances described in (1) to (5) below occur in the torque detection mechanism. (1) Detection delay due to the distortion amplifier that amplifies the output of the load cell, (2) Detection delay due to the inertia of the dynamometer oscillator, (3) Rotation angle synchronized torque pulsation generated from the dynamometer rotor, (4) Power Hysteresis phenomenon in the torque detection signal and impact torque signal caused by bumping of the connection between the meter oscillator and the load cell, (5) Generation of natural vibrations based on the inertia of the dynamometer oscillator and the elasticity of the load cell and its support device. Torque signal noise caused by. Among the above, (1) can be solved by improving the response of the distortion amplifier, and (3) can be solved by improving the machining accuracy of the rotor, but the other (2), (4), and (5) is difficult to resolve. In (4) above, these problems occur due to the existence of a gap, which occurs when an unnecessary shock load is applied to the load cell when the torque polarity changes, and this causes a disturbance signal, i.e. This is added to the output signal from the load cell as an impact torque signal. Furthermore, (5) is due to the fact that a vibration system is formed by the rotational inertia of the oscillator, the load cell, and the vibration-proof rubber due to the provision of the gap and the vibration-proof rubber. In other words, when the torque arm vibrates when the torque suddenly changes, unnecessary torque signal noise, that is, a vibration signal is added to the output signal. Furthermore, in (2), vibration isolating rubber is also required due to the need to install a knife edge, and this vibration isolating rubber lowers the vibration frequency of the above vibration system, which causes resonance with torque control and makes control uncontrollable. There are cases. Therefore, in order to perform stable torque control, the response speed of torque control must be delayed for detection. This is also an impediment when it is desired to measure the torque of a dynamometer up to a high frequency band. Furthermore, when a beam type load cell is used as a load cell in a conventional device, it is possible to measure torque without changing the torque sensitivity even without a knife edge, but due to the low rigidity of the load cell, resonance with the oscillator inertia is significant. Occurs at low frequencies. Furthermore, if the knife edge and anti-vibration rubber are removed and the structure is configured with an error in mind, the frequency of vibration will increase by 2 to 3 times due to the elasticity of the load cell, but as a result, the vibration amplitude will increase and the damping will be reduced. The coefficient decreases and the vibration damping time becomes very long. On the other hand, when there is a knife edge, the vibration becomes non-linear vibration, so the vibration frequency decreases, and this vibration must be determined by experiment. Examining the above-mentioned problems, it is considered that since the inertia of the oscillator is basically large, the rotational vibration frequency due to the vibration of the oscillator decreases, which becomes a practical obstacle. Therefore, the oscillator can be designed to have a small inertia, but in dynamometers that are generally used for high-speed rotation, reducing the inertia reduces the rigidity, and this reduction in rigidity also causes a new rotor to be designed. Vibrations will occur. Furthermore, since the oscillator constitutes a part of the magnetic path, a significant reduction in inertia cannot be expected. Therefore, in order to solve the above-mentioned conventional drawbacks, the present invention detects the vibration caused by the inertia of the rocker, performs coefficient processing, and then inversely adds the vibration generated to the load cell to the output signal obtained from the load cell. It is an object of the present invention to provide a torque detection device for a dynamometer that can obtain a torque control output with improved responsiveness by canceling unnecessary signals and removing detection signals and disturbance signals. Embodiments of the present invention will be described in detail below based on the drawings. Here, the principle of the present invention will be explained. Figure 3 shows a vibration model of the torque detection system. In the figure, F is the force (N) equivalent to the oscillator generated torque acting on the knife edge section, X is the force actually applied to the load cell (N), and M is the mass corresponding to the oscillator rotational inertia of the knife edge section. (Kg), K is the composite modulus of elasticity of the load cell and anti-vibration rubber (m/N), and C is the damping coefficient (N/m/s). In this case, M and F are expressed by the following relationship: M=J/L ² (Kg) F=T/L (N). Here, J is the rotational inertia of the oscillator (Kg·m ² ), L is the distance from the center of the oscillator to the point of force applied to the load cell (m), and T is the torque generated by the oscillator (N·m). Actually, in addition to the torque signal based on the reaction of the oscillator, an excitation force due to the vibration of the oscillator based on the inertia of the oscillator acts on the load cell. This vibration is expressed by the following equation (1), where F is the step input. Md ² x ² /dt ² +Cdx/dt+Kx=F...(1) Also, at the time when step input F is applied,
The load cell output Fx becomes a pulsating vibration waveform with a delayed rise as shown in FIG. Due to this phenomenon, in the past, it was not possible to measure the true waveform of the torque generated by the dynamometer oscillator, and it was also not possible to improve the responsiveness of the torque control of the dynamometer. Therefore, it is conceivable to improve the response by detecting the acceleration force due to the inertia of the oscillator and inversely applying it to eliminate the rise delay and pulsation of the output waveform of the load cell. In other words, the difference between the input F and the load cell output Fx in Fig. 3 becomes the transient torque detection delay or error signal F', which is determined by
It is equal to the solution when the initial value of Kx′ is F,
(3) becomes as follows. Md ² x'/dt ² +Cdx'/dt+Kx'=0...
(2) Kx′=Kx−F′……(3) Also, the damping coefficient C mainly occurs in the rocking mechanism of the rocker, but the Cdx′/dt term is extremely small compared to other terms, so it can be ignored. can do. As a result, the following equation
(4) and (5) hold true. Md ² x'/dt ² +Kx'≒0 ...(4) Md ² x'/dt ² ≒-Kx'=F' ...(5) Therefore, x' cannot be directly observed as a quantity, but d It can be seen that ^{the two} terms ^2x '/dt can be directly observed as the error signal F' by the acceleration detector. still,
In this case, since the acceleration detector can be drawn out from above the float to the fixed part using a thin electric wire, the swinging resistance of the swinging part does not increase due to this. In this embodiment, the error signal is directly observed, subjected to optimum coefficient processing, and added to the load cell output signal in order to eliminate the rise delay and pulsation of the load cell output. Therefore, since a torque detecting device as shown in FIGS. 5 and 6 can be considered, this will be explained first prior to the embodiments of the present invention. Note that the same parts as those in the conventional example are given the same numbers, and redundant explanations will be omitted. FIG. 5 shows an example in which the acceleration detector 20 is attached to the torque arm 6, and FIG. 6 shows the block configuration of a torque detection device using this acceleration detector 20. As shown in these figures, the acceleration of the load cell 9 in the load direction is caused by the torque arm 6
The acceleration detector 20 mounted above extracts the acceleration signal as an acceleration signal. In other words, load cell 9
The error signal added to the acceleration signal is extracted as an acceleration signal. This acceleration signal is sent to the acceleration signal amplifier 21
The acceleration force is amplified in the coefficient circuit 22, and a coefficient is set by calculating the acceleration force in accordance with the speed change rate of the oscillator inertia. The acceleration force signal output from the coefficient circuit 22 is transmitted from the load cell 9 to the strain amplifier 11.
Addition circuit 2 is added to the torque output signal obtained through
3 will be added at an appropriate rate. Therefore, in this adder circuit 23, the delay in the rise and pulsation of the torque output signal are canceled in accordance with the vibrations caused by the inertia of the oscillator, so that a torque control output A etc. with improved responsiveness can be obtained. . 13 in the figure is a torque indicator. The polarity of the addition circuit 23 is such that when the force pushing the load cell 9 downward in FIG. 5 is positive, the acceleration signal when acceleration occurs downward is positive. Furthermore, the strain amplifier 11 is not limited to this, and may use a resistance wire strain meter method, a magnetostrictive method, a piezoelectric method, or the like depending on the load detection method. This also applies to the acceleration detector 20 and the acceleration signal amplifier 21. Furthermore, the coefficients of the coefficient circuit 22 are determined by the oscillator inertia, the acceleration detector 20, and the acceleration signal amplifier 21, but the oscillator inertia in particular must be determined through experiments. It was established for this purpose. However, in the torque detection device shown in FIG. 6, the zero point of the acceleration detector 20 generally changes depending on temperature and the like, so there is a risk that the steady stability of the torque detection signal may be impaired. Therefore, in the present invention, the low level portion of the acceleration force signal is removed to avoid the influence of zero point fluctuation. Embodiments of the present invention will be described below with reference to FIGS. 7 and 8. The torque detection device in this embodiment is such that a filter 24 and a low level removal circuit 25 are successively interposed between the acceleration signal amplifier 21 and the coefficient circuit 22 in FIG. 6 as shown in FIG. Above filter 2
4 is provided to prevent acceleration signals outside the required frequency band from being input. In addition, since the zero point fluctuation of the acceleration detector 20 due to temperature etc. generally increases, the low level removal circuit 25 has the characteristics shown in FIG. 8 to prevent the steady stability of the torque detection signal from being impaired. As shown in the figure, it is provided to cut inputs below a certain level. In FIG. 8, a indicates the characteristic of the low level removal circuit, and b indicates an example of the characteristic of the acceleration signal. Therefore, in this embodiment, the acceleration detector 2
Since the output error associated with zero point fluctuation is improved, a stable torque control output A can be obtained. Next, the effects of the device of the present invention will be explained in comparison with the conventional device. (1) The response performance of this device was as shown in Table 1.

[Table] (2) In conventional equipment, electrical inertia simulation is sometimes performed by removing the vibration isolating rubber and rigidly supporting the load cell. In this case, the resonant frequency of the oscillator must be set higher than 10Hz. was difficult. Therefore, if the step response rise time of torque control is set to within 0.1 seconds, stability will be impaired, and it has been necessary to set it to 0.15 to 0.2 seconds. On the other hand, according to the device of the present invention,
It becomes possible to easily increase the frequency of torque detection. (3) Even if the load cell is rigidly supported in the conventional device, the damping coefficient is relatively lowered, resulting in a longer damping time for the oscillator vibration when the torque changes. On the other hand, according to the device of the present invention, it is possible to cope with the optimum state while considering the decay time. (4) When a load cell is rigidly supported in a conventional device, if the gap at the knife edge is not always kept at an extremely small value, there is a risk of overloading the load cell and damaging it, so regular inspections are required. Correction is required. On the other hand, according to the device of the present invention, the rigidity of the vibration isolating rubber can be optimized so as not to overload the load cell by using the vibration isolating rubber, and even if the gap is large to some extent, it can be tolerated. Therefore, the frequency of periodic inspection and correction can be significantly reduced, and adjustment work during manufacturing can also be shortened. (5) In the conventional device, the output of the load cell is zero as long as the knife edge portion does not come into contact with either the top or bottom of the receiving hole of the receiving arm. but,
In reality, some force is generated on the oscillator while the knife edge is moving within the gap, so a nonlinear detection delay occurs during the movement, which often causes nonlinear resonance. For example, during coasting in an electrical inertia simulation system, the output of the dynamometer is almost zero, and the knife edge is idle. In contrast, according to the device of the present invention, the moving acceleration of the rocker is detected and added to the load cell output, so that an output proportional to the moving acceleration can be obtained even when the knife edge section is moving within the gap. Therefore, nonlinear vibration can be prevented. (6) In the conventional device, when the knife edge portion completes its movement within the gap and collides with either side of the receiving hole, a large impact force is applied to the load cell and output as a disturbance signal. In contrast, according to the device of the present invention, the oscillator speed decreases in proportion to the force applied to the load cell when the knife edge collides, and at that time, an output proportional to the deceleration of the oscillator speed is output to the acceleration detector. and cancel each other out, so that almost no disturbance signal due to impact is output. This results in
It is possible to prevent nonlinear vibrations and measure accurate torque waveforms. It goes without saying that the device of the present invention is applicable not only to dynamometers for measuring power in general rotating machines, but also to dynamometers used in chassis dynamometers for measuring tire output of automobiles.

[Brief explanation of the drawing]

Figures 1a to 4 relate to the conventional example, with Figure 1a being a partially cross-sectional front view of the dynamometer, and Figure 1b being the front view of the dynamometer.
Figure 2 is a block configuration diagram of the torque detection device, Figure 3 is a vibration model diagram of the torque detection mechanism, and Figure 4 is a load cell when a step input is applied to the torque detection mechanism. Output waveform diagrams, FIGS. 5 to 8 relate to the device of the present invention, FIG. 5 is a partially sectional front view of the dynamometer, and FIG. 6 is a block configuration diagram of a torque detection device as a reference example. FIG. 7 is a block diagram of the torque detection device according to the present invention, and FIG. 8 is a graph showing the characteristics of the low level removal circuit. In the drawing, 5 is an oscillator, 6 is a torque arm, 7 is a knife edge, 9 is a load cell, 10 is a vibration isolator, 11 is a strain amplifier, 12 is an amplifier, 13 is a torque indicator, 20 is an acceleration detector, 21 2 is an acceleration signal amplifier, 22 is a coefficient circuit, 23 is an addition circuit, 2
4 is a filter, 25 is a low level removal circuit, A is a torque control output, etc.

Claims (1)

[Claims] 1. A torque detection device for an oscillating dynamometer that detects torque using a load cell includes an acceleration detector that is attached to the oscillator of the dynamometer and detects acceleration in the load cell loading direction, and a a coefficient circuit that amplifies the output and calculates an acceleration force corresponding to the speed change rate of the inertia of the oscillator; a low level removal circuit that removes a low level portion of the acceleration force output from the coefficient circuit; A torque detection device for a dynamometer, comprising an addition circuit that adds an oscillator inertial acceleration force sent from a low-level removal circuit to a torque output from the load cell.