JPH11336601A - Engine overheat warning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure an overheat warning function by releasing a warning even when a temperature of cooling water is an overheat setting temperature while an overheat avoiding operation is carried out by an overheat avoiding operation means, and prevent the warning by the warning means from unnecessarily continuing. SOLUTION: When a temperature of cooling water reaches an overheat setting temperature, an overheat switch 10 turns ON to sound a warning buzzer 15, and an indication lamp 16 is turned on. Thereafter, an engine speed inputting means 22 is manually rotated to decrease an engine speed of an engine 4, whereby the signal is taken into a control device 11, and the engine speed is decreased to an idling speed capable of avoiding an overheat or the speed near the idling speed. As a result, the warning buzzer 15 stops. The indication lamp 16 keeps turning on as long as the overheat switch 10 is in an ON state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided for a machine having an engine as a power source, such as a construction machine, and issues a warning to an operator or the like when the engine is overheated. Overheating warning device for an engine.

[0002]

2. Description of the Related Art For example, a hydraulic excavator is provided with an upper revolving structure rotatably mounted on a crawler type or wheel type lower traveling structure.
A front working mechanism for performing work such as excavation of earth and sand is mounted on the upper revolving structure. In this hydraulic excavator, the traveling of the vehicle and the turning of the upper swing body are driven by a hydraulic motor, and the front working mechanism is driven by a hydraulic cylinder. In order to drive a hydraulic actuator composed of the hydraulic motor and the hydraulic cylinder, it is necessary to supply pressure oil, which is high-pressure hydraulic oil. A hydraulic pump is provided for supplying hydraulic oil to each hydraulic actuator, and the hydraulic pump is driven by an engine.

[0003] From the above, an engine and a hydraulic pump are mounted on the upper swing body of a hydraulic excavator. Since the engine is heated during its operation, it is constantly cooled by cooling water during its operation. For this purpose, a radiator is attached to the engine, and cooling water is circulated between the radiator and the engine. Cooling air from a fan driven by an engine or the like is supplied to the radiator, and the cooling water returned from the engine to the radiator exchanges heat with the cooling air in the radiator to lower the cooling water temperature. Here, if the cooling water temperature is too low, the smoothness of the operation of the engine is impaired, and if the cooling water temperature is too high, there is a possibility that a failure such as damage to each part constituting the engine may occur. Therefore, the cooling water temperature is maintained within a predetermined temperature range, for example, in the range of about 90 ° C. to 110 ° C., and the upper limit temperature is set as the overheat set temperature so as not to exceed the overheat set temperature. .

[0004] In a hydraulic excavator, a predetermined operation such as excavation of earth and sand is performed using a front operation mechanism. In general, the engine is operated at a maximum rotational speed in order to improve the efficiency of the operation. However, the machine may be in a standby state, for example, waiting for a dump, and in this case, the engine speed is reduced to a minimum speed state, that is, an idle speed state. Further, in the case of light load work, energy is saved by operating the engine at an intermediate rotational speed between the maximum rotational speed state and the idle rotational speed state. For this purpose, as means for controlling the engine speed, for example, a dial-type engine speed control means is provided, and by appropriately operating the dial knob, the engine speed can be arbitrarily controlled. ing.

[0005] The radiator which exhibits the cooling water temperature suppressing function keeps the cooling water temperature within the above-mentioned temperature range. However, when excavation is continued for a long time under a high load operation state, the cooling water temperature gradually decreases. As a result, the engine may be overheated, and the components constituting the engine may be damaged. For this purpose, usually, a temperature detecting means for detecting the temperature of the cooling water is provided, and when the temperature of the cooling water reaches a certain level, an alarm to that effect is issued to an operator operating the machine. Therefore, the temperature set in the temperature detection means is the overheat set temperature, and even if the cooling water temperature rises to this overheat set temperature, the engine does not immediately overheat and a failure occurs, but the high load Is a temperature state where there is a risk that each part of the engine will be damaged in time. The alarm means that operates when the temperature of the cooling water rises to the set overheating temperature can be configured by a means that appeals to the operator's vision, such as a lamp, but in order to allow the operator to recognize it more directly and reliably. It is desirable to use an alarm buzzer as alarm means.

[0006]

The engine and the radiator are arranged in an engine room defined by an engine cover having a ventilation port, and the inside of the engine room is at a high temperature. Therefore, even if the operation of the machine is stopped, the cooling water temperature does not immediately decrease. For this reason, after the coolant temperature once rises to the overheat set temperature, the alarm buzzer may continue to sound for a long time as long as the engine is running, and when the operator is waiting in the cab, Will be bothered by the buzzer noise for a long time. Also, if the set overheating temperature is such that the machine continues to operate as it is, there is a possibility that the engine etc. may be damaged in the long term, so even if the alarm buzzer sounds, work immediately There is no need to interrupt, and if the operation is continued for a relatively short period of time, no particular trouble occurs even if the operation is continued. However, since the alarm buzzer sounds during this time, when the operator operates the machine, an adverse effect such as distraction of the operation is caused.

In consideration of the above points, the operation of the alarm buzzer can be stopped by a manual operation of the operator after the temperature detecting means detects that the cooling water is in the overheat set temperature range and the alarm buzzer starts to sound. A configuration in which a switch is provided is conventionally known. Therefore, the operator operates the switch to stop the operation after recognizing the overheating state by the sounding of the alarm buzzer, so that the operator waits in the cab or continues working for a predetermined time. To
No more buzzer noise.

However, the overheating alarm is issued only for the purpose of protecting the safety of the engine. Therefore, the alarm buzzer can be stopped by the operator despite the overheating set temperature. Is imperfect in terms of security. For example, after the alarm buzzer sounds, the switch stops the operation of this buzzer, and while continuing work, forgets that the cooling water temperature is already at the overheat set temperature. If the engine is erroneously recognized to be operating and high-load operation is continued for a long time, the cooling water temperature becomes abnormally high and the cooling efficiency of the engine decreases significantly, which may cause a problem in the engine. I can't deny it.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and when an overheated state occurs, a warning device is surely activated so that the function as a safety device can be fully exhibited, and an unnecessary degree can be obtained. It is an object of the present invention to provide an engine overheat alarm device in which the alarm generation state does not continue until the time t.

[0010]

In order to achieve the above-mentioned object, the present invention provides a temperature detecting means for detecting a cooling water temperature of an engine, and an alarm when the cooling water temperature reaches a set overheat temperature by the temperature detecting means. An engine overheating alarm device comprising: an overheating avoiding operation unit for operating the engine in a state where at least the cooling water temperature does not further rise; and Detecting means for detecting that an overheating avoiding operation is being performed, and when the detecting means detects that the overheating avoiding operation is being performed, even if the cooling water temperature has reached the overheat set temperature, the alarm is issued. The feature is that the warning by the generating means is canceled. .

The condition in which the temperature of the engine cooling water rises above the overheat set temperature is when the engine is operated at the maximum rotational speed or a rotational speed near the maximum rotational speed and the load on the engine is extremely high. Therefore, if the number of revolutions of the engine is reduced or the load on the engine is reduced, at least the cooling water temperature does not rise any more, and the temperature can be lowered. Further, by increasing the cooling efficiency of the radiator, it is possible to suppress an increase in the temperature of the cooling water. The above operation is an overheating avoiding operation for avoiding overheating. Therefore, as overheating avoiding operation means,
It can be constituted by any one of means for reducing the number of revolutions of the engine, means for reducing the load on the engine, means for improving the cooling efficiency, and the like, or a combination of these.

For example, even if the cooling water temperature falls within the overheat set temperature range, an increase in the cooling water temperature can be suppressed or reduced by lowering the engine speed to some extent. Therefore, an example of the overheat avoiding operation means can be constituted by the engine speed control means. Further, the detecting means for detecting whether or not the overheating avoiding operation is performed may be configured to directly or indirectly detect the engine speed. Generally, the engine speed can be detected by the engine speed detecting means. Therefore, when the engine speed detecting means detects that the engine speed has become equal to or lower than the engine speed at which overheating is avoided, an alarm means is provided. It is sufficient to cancel the warning by. The engine speed control means can be constituted by an engine speed input means. In this case, the alarm should be canceled by an indirect detection means such as an output signal from the engine speed input means. The number of revolutions of the engine at the time of the overheating avoiding operation can be detected.

Here, the rotation speed at which the operation of the alarm means is stopped can be substantially the idle rotation speed when set uniformly. As a result, the temperature of the cooling water surely decreases. However, the operation of the machine is extremely suppressed in the idle speed state. Therefore, the rotation speed can be set to be equal to or higher than the idle rotation speed in consideration of the working efficiency of the machine. In short, it is only necessary to set the rotation speed at which the cooling water temperature does not rise.The engine rotation speed in the overheating avoiding operation may be equal to or higher than the idle rotation speed. In this case, the engine rotation speed may be set based on the actually measured value or the like. Good.

It is preferable to use an alarm buzzer as the alarm means so that the operator can more directly recognize the alarm. Since the alarm buzzer stops when the overheat avoiding operation is performed, the operator cannot recognize whether the cooling water temperature has become equal to or lower than the overheat set temperature by the overheat avoiding operation. Therefore, it is more preferable to provide an overheat indicator lamp together with a buzzer that constitutes an alarm means, so that the overheat indicator lamp is turned on as long as the temperature is within the overheat set temperature range even while performing the overheat avoiding operation. preferable. Thus, when the lamp is turned off, the overheating avoiding operation can be canceled.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a case will be described in which the overheat avoiding operation is an operation of reducing the engine speed. However, besides this, it is also possible to avoid overheating by, for example, reducing the engine load.

First, FIG. 1 shows an example of a structure of an engine and a cooling mechanism thereof, which is usually installed in a hydraulic excavator. In the figure, reference numeral 1 denotes a frame of the upper revolving superstructure, and 2 denotes an engine cover. An engine room 3 defined by the engine cover 2 is formed above the frame 1 of the upper-part turning body. An engine 4 is provided in the engine room 3 and a hydraulic pump 5 driven by the engine 4 is provided. A radiator 6 is disposed so as to face the engine 4.
A cooling fan 7 that is rotatably driven by the engine 4 or a battery (not shown) as a power source is provided between the cooling fan 7 and the radiator 6.

During the operation of the engine 4, the cooling fan 7 rotates at all times, an air flow is formed in the engine room 3, cooling air is supplied to the radiator 6, and passes through the radiator 6. Cool the cooling water. In order to efficiently cool the radiator 6 and form a cavity airflow in the engine room 3, the engine cover 2 has an outside air intake 8 and an exhaust port 9.
The exhaust port 9 may also be formed in the frame 1. With this configuration, a flow of air is formed as indicated by an arrow in the figure, and as a result, the radiator 6
The engine cooling water passing through the inside exchanges heat with the cooling air to lower the temperature of the cooling water.

The cooling water that has cooled the engine 4 is cooled in the radiator 6, but excessive cooling impedes the smooth operation of the engine 4, so that the cooling water is kept within a somewhat high temperature range. . However, if the temperature of the cooling water rises too much, the engine 4 will overheat, and eventually each part of the engine 4 will be damaged. Therefore,
When the cooling water temperature is detected and exceeds a predetermined temperature, that is, an upper limit temperature, an alarm is issued to an operator. For this purpose, the radiator 6 is provided with temperature detecting means for detecting the temperature of the cooling water, specifically, a temperature switch which is turned on when the temperature of the cooling water exceeds a set temperature.
Is turned on at an overheat set temperature at which overheating may occur. This is an overheat switch, and an engine overheat alarm device including this overheat switch and an alarm generating means for generating an overheat alarm in conjunction therewith is configured.

FIG. 2 shows a schematic configuration of the engine overheat alarm device according to the first embodiment of the present invention. In the figure, reference numeral 10 denotes an overheat switch, and this overheat switch 10 is provided in the radiator 6. The overheat switch 10 is connected to the control device 11. The control device 11 includes a power supply circuit 12
And a CPU 13 and a ROM 14 in which the procedures for detecting overheating and generating an alarm are set. Therefore, when the overheat switch 10 is turned on, that is, when the cooling water temperature exceeds the set overheat temperature, the CPU 13 detects this and issues an alarm according to the procedure set in the ROM 14. An alarm buzzer 15 is used as an alarm generating means for generating this alarm, and a display lamp 16 for displaying an overheat state is also provided.

With the above configuration, when the cooling water temperature reaches the overheat set temperature, the alarm buzzer 1
5 sounds, and the display lamp 16 is turned on. As a result, the operator who operates the machine can recognize the overheating of the engine 4. Here, the level of the cooling water temperature set as the overheat set temperature does not immediately cause an abnormality in the engine 4 in this temperature state, but when the machine is continued in the same operating state, the cooling water temperature further increases. Eventually, the engine 4 will fail. Therefore, no trouble occurs unless the temperature is raised above the overheat set temperature, that is, if the temperature is maintained or the temperature is lowered.

If the operator performs certain operations, the temperature of the cooling water does not rise to a value higher than that, so that overheating can be avoided. This operation is an overheating avoidance operation. If the rotation speed of the engine 4 is reduced, overheating can be avoided. In the first place, the temperature of the cooling water of the engine 4 rises above the set temperature of the overheat when the engine 4 is operating at the maximum rotational speed, and when the rotational speed of the engine 4 is lowered, at least the cooling water temperature becomes lower. If the degree of rise can be suppressed and the rotational speed is further reduced, the temperature will not rise any more. When the engine speed drops below a certain rotational speed, the temperature of the cooling water drops. Therefore, the rotation speed control means of the engine 4 is constituted by overheat avoidance operation means, and the detection means for detecting whether or not the overheat avoidance operation means is operated is constituted by rotation speed detection means for detecting the rotation speed of the engine. Can be.

Therefore, as the overheat avoiding operation means, the rotational speed control means of the engine 4 is used as described below. Thus, 20 is a governor, 21 is a controller, and 22 is an engine speed input means.
The governor 20 has a governor lever 20a. The governor lever 20a can rotate within a range regulated by both stoppers 20U and 20L. The rotation speed of the engine 4 changes according to the rotational position of the governor lever 20a. I do. When the governor lever 20a rotates toward the stopper 20U, the rotation speed of the engine 4 increases, and when the governor lever 20a rotates toward the stopper 20L, the rotation speed of the engine 4 decreases.

Here, the engine speed input means 22 has a potentiometer 23, and the potentiometer 23 is configured so that a movable contact 23b is slidably contacted with a resistor 23a formed in an arc shape. Further, a dial-type knob 23c is provided.
By manually rotating c, the knob 23c
An output voltage signal corresponding to the position is output. The output voltage signal is taken into the controller 21, and a drive signal is inputted from the controller 21 to a motor 24 for rotationally driving the governor lever 20 a, and the governor lever 20 a is rotated by operating the motor 24. It has been done.

The controller 21 includes a power supply circuit 25, a CP
U26 and ROM 27, and A / D converter 28
And a motor driver 29. A voltage signal is output from the engine speed input means 22 as an engine speed command signal, and the A / D converter 28 converts the command signal into a digital signal. This signal is an engine speed command signal. When the CPU 26 receives the command signal, the CPU 26 calculates a drive amount for the motor 24 and inputs a drive signal to the motor driver 29. As a result of the operation of the motor 24 and the rotation of the governor lever 20a,
The engine 4 is controlled so that the rotation speed of the engine 4 becomes a value instructed by the engine speed input means 22.

A voltage signal as an engine speed command signal output from the engine speed input means 22 is also taken into the control device 11 side. And the control device 11
Is provided with an A / D converter 30. The A / D converter 30 converts the rotation speed signal of the engine 4 into a digital signal and takes it into the CPU 13. On the other hand, the number of revolutions of the engine 4 necessary for avoiding overheating is set in the ROM 14 in advance. The rotation speed set here is, for example, an idle rotation speed or a slightly higher rotation speed. The rotation speed of the engine 4 during the overheating avoiding operation can be arbitrarily set in relation to the working efficiency and the like, provided that the cooling water temperature does not rise at least any more. As long as the engine 4 operates in this rotational speed state, the cooling water temperature does not decrease, or at least does not increase.
Then, when the rotation speed of the engine 4 becomes the rotation speed at the time of avoiding overheating, the CPU 13 controls the alarm lamp 15 to stop sounding even if the overheat switch 10 is in the ON state. However, the display lamp 16 is the overheat switch 10
Is not turned off as long as is turned on.

This embodiment is configured as described above. When the hydraulic pump 5 is driven by operating the engine 4, the hydraulic oil is applied to the hydraulic actuators provided in the respective operating parts of the hydraulic shovel. Is supplied, and work such as excavation of earth and sand by the excavator is performed. When performing work such as excavation in this manner, the engine 4 is maintained at the maximum rotation state from the viewpoint of work efficiency. As a result, the temperature of the cooling water for cooling the engine 4 gradually increases, and if the cooling water is operated continuously for an extremely long time, the temperature may eventually exceed the temperature set as the overheat set temperature.

When the cooling water temperature exceeds the set overheat temperature, the overheat switch 10 is turned on. As a result, the alarm buzzer 15 sounds and the display lamp 16 is turned on to let the operator recognize that the overheating condition has occurred. Then, the operator rotates the knob 23c constituting the engine speed input means 22 functioning as the overheat avoiding operation means, and
When the rotation speed of the engine 4 is reduced, this signal is taken into the control device 11 and is reduced to a rotation speed at which overheating can be avoided, that is, an idle rotation speed or a rotation speed close to the idle rotation speed. As a result, the sounding of the alarm buzzer 15 is stopped. I do. However, the display lamp 16 is kept on as long as the overheat switch 10 is on.

As described above, the sounding of the alarm buzzer 15 is stopped by performing the overheating avoiding operation. Therefore, for example, when the operator stands by while the operation of the hydraulic excavator is stopped, the operator is troubled by unpleasant buzzer noise. No more. In addition, since the operation continues even when the engine 4 is in the idle speed state, the hydraulic pump 5 is pressurized with the hydraulic oil. Accordingly, running, turning, and the like are enabled, and operations such as moving a hydraulic shovel can be performed. However, since the supply amount of the pressure oil to each hydraulic actuator is limited, the operation speed becomes slow.
Since the alarm buzzer 15 does not sound, the operator can concentrate on the operation, and the safety and reliability of the operation are ensured. When the rotation speed of the engine 4 is reduced to almost the idling rotation speed, the temperature of the cooling water that has been in the overheat set temperature state decreases, or at least the temperature does not increase any more. Even if such a restricted operation is performed, there is no danger of the engine 4 being overheated and the engine 4 is not damaged.

By the way, as long as the cooling water temperature is within the overheat set temperature range, the overheat switch 1
In the case of 0, the ON state is continued, and the display lamp 16 is kept in the lighting state accordingly. Needless to say, although the cooling water temperature is lowered by lowering the rotation speed of the engine 4, some time is required until the temperature becomes lower than the set overheating temperature. If the operator increases the number of revolutions of the engine 4 during this time, the overheating avoiding operation is interrupted, and the alarm buzzer 15 sounds again, so that there is no risk of erroneous operation and the function as a safety device is reduced. Will be fulfilled.

If the overheat avoiding operation is continuously performed for a predetermined time, the cooling water temperature falls below the overheat set temperature. At this time, the display lamp 16 is turned off, so that the operator can confirm that the overheat state has been resolved without delay by checking the display lamp 16. Therefore, when it is confirmed that the display lamp 16 has turned off, the engine 4 can be quickly returned to the efficient working state by immediately operating the engine speed input means 22 to return the engine 4 to the maximum speed state. .

The overheat avoidance operation is detected based on a signal from the engine speed input means 22.
When the number of revolutions of the engine 4 is changed by the
Although the output signal of the potentiometer 23 constituting the engine speed input means 22 may be directly taken in as the signal taken in by the first embodiment as described in the first embodiment, the CPU 26 constituting the controller 21 substantially does so. The target rotation speed of the engine 4 is calculated according to the command from the engine rotation speed input means 22. When the target rotation speed is a rotation speed suitable for the overheating avoidance operation, an H-level signal is output. An L level signal may be input to the control device 11 when the rotation speed is the above. To this end, as shown in FIG. 3, the CPU 26 of the controller 21 and the control device 11
It is sufficient to connect the CPU 13 on the side with the wiring 31 so as to flow this signal. Therefore, H through the wiring 31
When a level signal is input to the CPU 13,
As long as the level signal is being input to the CPU 13, the alarm buzzer 15 is stopped.

As shown in FIG. 4, when the engine 4 is provided with the rotation speed detector 32, the rotation speed signal from the rotation speed detector 32 is directly transmitted to the CP of the controller 11.
U13. In this case, the ROM
In 14, the number of revolutions of the engine 4 when overheating is avoided is set in advance. Further, as shown in FIG. 5, when a sensor 33 for detecting the rotation position of the governor lever 20a is provided, a signal from the sensor 33 is taken into the control device 11, and the output from the sensor 33 is output. Based on the signal, that is, according to the position of the governor lever 20a, it is determined whether or not the number of rotations at the time of avoiding overheating is C.
The operation of the alarm buzzer 15 may be controlled by judging by the PU 13.

As the engine speed input means, in addition to the above-mentioned dial type, as shown in FIG. 6, an operation lever 40 is used to connect a control cable between the operation lever 40 and the governor lever 41a of the governor 41. 42
Some are configured to be connected by a. In this case,
The operation lever 40 is a rotation speed control means. The operation lever 40 is provided with an angle detector 43 for detecting the operation angle of the operation lever 40, and the angle detector 43 functions as a detection means for detecting whether or not an overheating avoidance operation has been performed. Let it. Here, since the rotation position of the governor lever 41a is determined according to the operation angle position of the operation lever 40, the detection signal by the angle detector 43 is a signal corresponding to the rotation speed of the engine 4.

Therefore, the output signal from the angle detector 43 is compared with the rotation speed at the time of the overheating avoiding operation by the comparator 44, and when the rotation speed is higher than that, an H level signal is output. Then, this signal and the signal from the overheat switch 10 are connected to an AND circuit 45.
And the alarm buzzer 15 operates when the output signal from the AND circuit 45 is at the H level, that is, when the overheat switch 10 is ON and the angle detector 4
When the number of revolutions of the engine 4 output from the engine 3 is higher than the number of revolutions during the overheating avoiding operation, the alarm buzzer 15 sounds. On the other hand, the indicator lamp 16 is not directly connected to the overheat switch 10, and accordingly, the indicator lamp 16 is not connected.
Irrespective of the rotation speed of the engine 4, as long as the overheat switch 10 is in the ON state, that is, as long as the cooling water temperature is higher than the overheat set temperature, the lighting is continued.

[0035]

As described above, according to the present invention, in a state where the cooling water temperature has reached the set overheating temperature and an alarm has been issued by the alarm means, at least the cooling water temperature does not rise further by the overheating avoiding operation means. While the overheat avoiding operation is being performed so as to operate, even if the cooling water temperature is at the overheat set temperature, the alarm by the alarm generating means is released, so that the overheat alarm function is surely exhibited. ,
There is an effect that the warning by the warning means can be continued unnecessarily and an operator or the like can be prevented from being bothered.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing an arrangement configuration of an engine and peripheral devices thereof.

FIG. 2 is a schematic configuration diagram of an engine overheat alarm device having an alarm release function according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an engine overheat alarm device having an alarm release function according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an engine overheat alarm device having an alarm release function according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an engine overheat alarm device having an alarm release function according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an engine overheat alarm device having an alarm release function according to a fifth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 4 engine 6 radiator 10 overheat switch 11 control device 15 alarm buzzer 16 display lamp 20, 41 governor 20a, 41
a Governor Lever 21 Controller 22 Engine Speed Input Means 23 Potentiometer 24 Motor 31 Wiring 32 Speed Detector 33 Sensor 40 Operating Lever 42 Control Cable 43 Angle Detector 44 Comparator 45 AND Circuit

Claims (6)

[Claims] 1. An engine overheat alarm device comprising: a temperature detecting means for detecting a temperature of a cooling water of an engine; and an alarm generating means for generating an alarm when the temperature of the cooling water reaches a set overheat temperature by the temperature detecting means.
Overheat avoiding operation means for operating the engine in a state where at least the cooling water temperature does not further rise, and detecting means for detecting that an overheat avoiding operation by the overheat avoiding operation means is performed, An engine overheat alarm, wherein when the detection means detects that an overheat avoidance operation is being performed, the alarm by the alarm generation means is canceled even if the cooling water temperature has reached the overheat set temperature. apparatus. 2. The overheat avoiding operation means comprises a rotational speed control means of the engine, and the detecting means detects that the rotational speed control means has reached a rotational speed at which overheating is avoided. 2. The engine overheat alarm according to claim 1, wherein: 3. The engine speed control means includes an engine speed input means, and is configured to detect an engine speed based on an output signal from the engine speed input means. The engine overheat alarm device according to claim 2, wherein 4. The engine overheat warning device according to claim 2, wherein the engine speed at which the warning of the warning means is released is set substantially at an idle speed. 5. The engine overheat alarm device according to claim 1, wherein said alarm generation means comprises an alarm buzzer that sounds when an overheat condition occurs. 6. An overheat indicator lamp is provided together with the alarm means, and the overheat indicator lamp is turned on as long as the cooling water is within the overheat temperature range, even during the operation of avoiding overheating. The engine overheat alarm device according to claim 5, wherein