JP2001193460A - Rotational speed control device for motor-driven cooling fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain improvement in comfort in an automobile, by suppressing generation of a beat due to the resonance of an engine and a motor-driven cooling fan. SOLUTION: This rotational speed control device for an electric motor-driven cooling fan cooling an engine has an electric motor which drives the cooling fan and a control unit for controlling a rotational speed of the electric motor. Here, the control unit variably controls the rotational speed of the electric motor in such a manner that a deviation amount Δf between a frequency f1 of rotational primary component of the electric motor and a frequency f2 of rotational n-th order component of the engine is prevented from decreasing smaller than a prescribed frequency width S (for example 7 Hz).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the number of revolutions of an electric cooling fan, and more particularly to suppressing a beat which is a resonance phenomenon between an engine and a cooling fan.

[0002]

2. Description of the Related Art As an engine cooling fan for an automobile, a fan using the driving force of an electric motor has become mainstream instead of the conventional fan that directly uses the driving force of the engine. In such an electric cooling fan, the number of revolutions is controlled in accordance with the temperature of the cooling water of the engine, the vehicle speed, and the like, thereby improving the cooling efficiency and the fuel efficiency. For example, Japanese Unexamined Utility Model Publication No. 55-165914 discloses a technique for controlling the rotation speed of a cooling fan according to the engine rotation speed so that the noise of the electric cooling fan does not exceed the noise level of the engine.

[0003]

By the way, there is a problem that the rotation system including the fan generates vibrations during the rotation of the cooling fan. The cooling fan is made of a bent metal plate or an integrally formed resin. However, the cooling fan itself has a considerable size, and its processing and forming accuracy is limited. Therefore, it is extremely difficult to completely balance the weight of the cooling fan. As a result, when the electric cooling fan rotates, vibrations due to weight imbalance occur in the entire fan including the electric motor. Such a vibration of the cooling fan can be extremely satisfactorily suppressed by recent advances in production technology, but it is difficult to completely prevent its occurrence.

Further, in addition to the vibration of the cooling fan, the automobile also has a vibration source called an engine. The engine is a vibration source that generates a wide range of frequencies because the number of revolutions changes according to the operating conditions. Therefore, the vibrating force of two vibration sources, the engine and the electric cooling fan,
A resonance phenomenon called "beat" may occur.
Here, “beat” refers to a beat phenomenon in which a wavy sound (or vibration) occurs when a plurality of sounds (or vibrations) having close frequencies are generated at similar levels. When a beat vibration (beat vibration) or a beat sound (beat sound) caused by such a beat is generated, the occupant of the automobile feels uncomfortable.

An object of the present invention is to suppress the occurrence of a beat, which is a resonance phenomenon between an engine and a cooling fan, and to improve the comfort of an automobile.

[0006]

According to a first aspect of the present invention, an electric motor for driving a cooling fan and a rotation of the electric motor are provided. Control means for variably controlling the number. This control means controls the deviation between the frequency of the rotation n-order component (n ≧ 1) associated with the rotation of the engine and the frequency of the rotation primary component associated with the rotation of the electric motor so as not to be smaller than a predetermined frequency width. Controls the rotation speed of the electric motor.

It is preferable that the control means controls the number of rotations of the electric motor so that the above-mentioned deviation does not become smaller than a predetermined frequency width in all engine rotation speed regions.

Further, it is desirable that the predetermined frequency width is 7 Hz.

[0009] In the above configuration, the engine is 2
Preferably, the engine is a four-stroke engine having n cylinders.

[0010]

FIG. 1 is a block diagram of a cooling fan rotation speed control device according to the present embodiment. The duty of the electric motor 1 that drives a cooling fan (not shown) is controlled by the control unit 2. That is, the control unit 2 calculates the number of revolutions of the electric motor 1 (corresponding to the number of revolutions of the cooling fan) based on the sensor information from each of the sensors 4 to 6, and calculates the duty ratio DUTY according to the number of revolutions to be set. Is output. The PWM signal output from the control unit 2 is leveled by a leveling circuit composed of a capacitor 7 and a resistor 8, and then supplied to the base of the transistor 3, which is a current supply source. As a result, a current corresponding to the duty ratio DUTY of the PWM signal is supplied to the electric motor 1, and the rotation speed becomes the set rotation speed calculated by the control unit 2.

The engine speed sensor 4 is a sensor for detecting the speed of the crankshaft of the engine, that is, the engine speed Ne. Further, a water temperature sensor 5
The vehicle speed sensor 6 is a sensor for detecting the temperature T of the engine cooling water and the vehicle speed υ.

Prior to the description of the control of the number of revolutions of the cooling fan according to the present embodiment, first, an outline of beats caused by two vibration sources of the engine and the cooling fan will be described. FIG. 2 is a beat sound frequency characteristic diagram resulting from a secondary rotation sound of the engine (secondary rotation component) and a primary rotation sound of the electric cooling fan (first rotation component). Here, the “n-th rotation sound” means a sound generated n times in one rotation (the same applies to beat vibration). In a four-cycle four-cylinder engine, there are four explosion strokes in two revolutions (one cycle) of the engine, so two sounds are generated in one revolution ("secondary rotation sound"). As described above, the “beat sound” refers to a beat sound generated when frequencies of a plurality of sounds having similar levels approach each other. If the peak frequency of the secondary rotation sound of the engine is f2 (Hz) and the peak frequency of the primary rotation sound of the cooling fan is f1 (Hz), these frequencies f1 and f2
If the deviation amount Δf (Δf = | f2−f1 |) is large, no beat sound is generated.

Conversely, when the frequencies f1 and f2 are close to each other and the shift amount Δf becomes smaller than a predetermined frequency width S, a beat occurs. As a result, beat sounds and beat vibrations cause discomfort to the occupants of the automobile. As a result of a detailed study of the beat generation mechanism through experiments, simulations, and the like, the inventors have confirmed that when the shift amount Δf is smaller than 7 Hz, a beat that can be felt by the occupant is generated. Therefore, in the state shown in FIG. 2, that is, in the state where the frequency f2 of the secondary rotation sound of the engine is 33 Hz and the frequency f1 of the primary rotation sound of the cooling fan is 38 Hz,
A beat sound or beat vibration that causes discomfort to the occupant is generated.

FIG. 3 is a diagram for explaining a beat sound generation region in the vicinity of an idle rotation speed region. The rotational speed of the engine in the idle state is set in a relatively wide range from, for example, 700 rpm (no load state) to 1150 rpm (air conditioner operating state). In this state, the frequency f2 of the secondary rotation sound of the engine is 23.3 Hz. ~ 38.3Hz.
Further, assuming that the cooling fan is rotating at, for example, 2280 rpm, the frequency f1 of the rotating primary sound is 38 Hz.
Therefore, in a state where the cooling fan is operating, FIG.
, The engine speed region indicated by hatching, that is,
A beat sound is generated in the engine speed range from Ne1 to Ne2 where the shift amount Δf is smaller than a predetermined frequency width S (S = 7 Hz). Thus, even in the idle state, a beat occurs due to resonance with the cooling fan depending on conditions.

Therefore, in this embodiment, the rotation speed of the cooling fan is variably controlled so that the rotation speed characteristic shown in FIG. 4 is obtained. Specifically, the engine speed Ne is monitored by the engine speed sensor 4, and the duty ratio DUTY (%) of the PWM signal is controlled according to the state as follows (example).

(Setting example of duty ratio) Engine rotation speed Ne (rpm) Duty ratio DUTY (%) Ne ≦ Ne1 DUTY = α (constant value) Ne1 <Ne <Ne3 DUTY = A · Ne + B Ne3 ≦ Ne <Ne2 DUTY = A · Ne + C Ne2 ≦ Ne DUTY = α (constant value)

Here, the constant value α is a duty ratio that sets the frequency f1 of the cooling fan to, for example, 38 Hz. The slope A has the same value as the slope indicating the rate of change of the engine frequency f2. The constant B is the engine speed N
The value is set to a value that becomes a constant value α at e1 (that is, a value that is continuous with the duty ratio α set at a lower rotational speed). Further, the constant C is set to a value that becomes a constant value α at the engine speed Ne2 (that is, a value that is continuous with the duty ratio α set at a higher engine speed Ne2).

Through such control, the deviation Δf of the frequencies f1 and f2 between the engine and the cooling fan is equal to the predetermined frequency width S in all engine speed regions.
It is set so as not to be smaller than. This allows
Since generation of a beat, which is a resonance phenomenon between the engine and the cooling fan, can be prevented, it is possible to effectively prevent the occupant of the automobile from feeling uncomfortable.

Although the above-described embodiment relates to a four-cylinder engine, it goes without saying that the present invention can be applied to an engine having more cylinders. Assuming that the number of cylinders is 2n (n ≧ 1), the problem in relation to the beat is basically the frequency of the n-th rotation component (basic order n) of the engine. For example, in a six-cylinder engine, the frequency of the tertiary rotational component becomes a problem. However,
As the number of cylinders increases, it is necessary to consider frequency components other than the fundamental order.

The variable control of the cooling fan as described above may be appropriately performed according to the operating state. For example, the cooling state of the engine is monitored by the water temperature sensor 5, and when the water temperature T is equal to or higher than a predetermined value, or when the water temperature increase rate is equal to or higher than a predetermined value, the above-described variable control is not performed. Is also good. As shown in FIG. 4, when the engine rotation speed is in the range of Ne3 to Ne2, the rotation speed of the cooling fan is lower than in the normal state (duty ratio DUTY = α), so that the cooling efficiency of the engine is reduced. Therefore, when it is highly necessary to cool the engine, the above-described variable control is stopped, and the cooling efficiency can be increased by setting the duty ratio DUTY to α (%) as in the normal control.

Further, the vehicle speed υ may be monitored by the vehicle speed sensor 6, and when the vehicle speed の is equal to or higher than a predetermined value, the above-described variable control of the cooling fan may not be performed.
The beat sound and the beat vibration are easily perceived at an idling time when the surrounding noise is relatively small, but are hardly perceived at the time of traveling where background noise, road surface vibration and the like are masked by the noise.
Therefore, at a relatively high vehicle speed, the control of the cooling fan for preventing the beat may be stopped.

Further, a sensor for detecting the rotation speed of the electric motor 1 may be further provided, and the feedback control of the electric motor 1 may be performed based on the detected rotation speed. The rotation speed of the cooling fan is determined by the driving force of the electric motor 1 and the air resistance of the fan. When the vehicle is stopped or at a very low speed, the air resistance is small, so the rotation speed of the cooling fan is almost proportional to the driving force of the electric motor 1. However, as the vehicle speed increases, the air resistance also increases, so that the proportional relationship between the rotation speed of the cooling fan and the driving force of the electric motor 1 breaks down. Increase). Therefore, if feedback control is performed so that the actual rotation speed of the electric motor 1 detected by the sensor matches the target rotation speed, the rotation speed of the cooling fan (electric motor 1) can be controlled with high accuracy, and the occurrence of beats can be reduced. It is possible to prevent it more effectively.

[0023]

As described above, according to the present invention, a beat which is a resonance phenomenon between the engine and the cooling fan is prevented from being generated.
The rotation speed of the cooling fan is variably controlled. This allows
Since it is possible to prevent the generation of a beat sound or a beat vibration that can be felt by the occupant of the vehicle, the comfort of the vehicle can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a cooling fan rotation speed control device according to an embodiment;

FIG. 2 is a beat sound frequency characteristic diagram caused by a secondary rotation sound of an engine and a primary rotation sound of an electric cooling fan.

FIG. 3 is a diagram illustrating a region where a beat sound is generated in the vicinity of an idle rotation speed region;

FIG. 4 is a characteristic diagram of a rotation speed control of the cooling fan according to the embodiment.

[Explanation of symbols]

1 electric motor, 2 control unit, 3 transistor, 4 engine speed sensor, 5 water temperature sensor, 6
Vehicle speed sensor, 7 capacitor, 8
resistance

Claims (4)

[Claims] 1. An electric cooling fan rotation speed control device for cooling an engine, comprising: an electric motor for driving a cooling fan; and control means for variably controlling the rotation speed of the electric motor. The electric motor is controlled so that the difference between the frequency of the n-th rotational component (n ≧ 1) accompanying the rotation of the engine and the frequency of the primary rotational component associated with the rotation of the electric motor does not become smaller than a predetermined frequency width. A rotation speed control device for an electric cooling fan, wherein the rotation speed is controlled. 2. The electric motor according to claim 1, wherein the control means controls the number of revolutions of the electric motor so that the deviation does not become smaller than the predetermined frequency width in all engine revolution ranges. A control device for the number of revolutions of the electric cooling fan described in the above item. 3. The control device according to claim 1, wherein the predetermined frequency width is 7 Hz. 4. The apparatus according to claim 1, wherein said engine is a four-stroke engine having 2n cylinders.