JP3829473B2 - Engine overheat warning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine overheat alarm device that is provided in a machine equipped with an engine as a power source, such as a construction machine, for generating an alarm and notifying an operator or the like when the engine is overheated. Is.
[0002]
[Prior art]
For example, a hydraulic excavator has a structure in which an upper revolving unit is installed in a crawler-type or wheel-type lower traveling unit so that the upper revolving unit can be turned, and a front working mechanism for performing work such as excavation of earth and sand is attached to the upper revolving unit. Is. In this hydraulic excavator, traveling of the vehicle and turning of the upper-part turning 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 including these hydraulic motor and hydraulic cylinder, it is necessary to supply pressure oil that is high-pressure hydraulic oil. A hydraulic pump is provided to supply pressure oil to each hydraulic actuator, and the hydraulic pump is driven by an engine.
[0003]
From the above, the engine and the hydraulic pump are mounted on the upper swing body of the hydraulic excavator. Since the engine is heated during its operation, it is always cooled by cooling water during operation. For this purpose, a radiator is attached to the engine so that 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, thereby lowering 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, a failure may occur such as damage to each part constituting the engine. Accordingly, the cooling water temperature is maintained within a predetermined temperature range, for example, a 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 order to improve the efficiency of the operation, the engine is generally operated at a maximum rotational speed. However, the machine may be put into a standby state, such as waiting for a dump, and in this case, the engine speed is reduced to the minimum speed state, that is, the idle speed state. Further, in the case of light load work, energy saving is achieved by operating the engine at an intermediate rotational speed between the maximum rotational speed state and the idle rotational speed state. For this purpose, for example, a dial-type engine speed control means is provided as means for controlling the engine speed, and the engine speed can be arbitrarily controlled by appropriately operating a dial knob. ing.
[0005]
The radiator that exhibits the cooling water temperature suppression function keeps the cooling water temperature within the above-mentioned temperature range. However, if drilling is continued for a long time in a high-load operation state, the cooling water temperature gradually increases. Eventually, the engine overheats, and there is a risk of damaging each part of the engine. For this reason, normally, temperature detecting means for detecting the cooling water temperature is provided, and when the cooling water temperature reaches a certain level by this temperature detecting means, an alarm to that effect is issued to the operator who operates 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 remains unchanged. If the operation is continued, there will be a risk that the parts of the engine will eventually be damaged. And the alarm means that operates when the cooling water temperature rises to the overheat set temperature can be configured with something that appeals to the operator's vision, such as a lamp, but in order to make the operator recognize more directly and reliably It is desirable to use an alarm buzzer as an alarm means.
[0006]
[Problems to be solved by the invention]
By the way, the engine and the radiator are arranged in an engine room defined by an engine cover having a ventilation hole, and the inside of the engine room is in a high temperature state. Therefore, even if the operation of the machine is stopped, the cooling water temperature does not immediately decrease. For this reason, once the cooling water temperature rises to the overheat set temperature, the alarm buzzer may sound for a long time as long as the engine is operated, and the operator is waiting in the cab. Will be bothered by buzzer noise for a long time. In addition, if the overheat set temperature continues as it is, the engine is likely to be damaged in the end, so even if the alarm buzzer sounds, work immediately. It does not have to be interrupted, and if it is a relatively short time, even if the work is continued, no particular trouble is caused. However, since the alarm buzzer sounds during this time, when the operator operates the machine, there is an adverse effect such as distracting attention to the operation.
[0007]
Considering the above points, a switch that can stop the alarm buzzer by manual operation of the operator after the temperature detection means detects that the cooling water is in the overheat set temperature range and the alarm buzzer starts sounding is provided. Such a configuration is conventionally known. Therefore, after the operator recognizes that the alarm buzzer is in an overheated state, the operator operates the switch to stop its operation, so that the operator waits in the cab and continues to work for a predetermined time. In addition, the buzzer noise is not bothered.
[0008]
However, since the overheat alarm is issued only to protect the safety of the engine, it is safe that the operator can stop the alarm buzzer even if the overheat set temperature is exceeded. Incomplete from the point of securing. For example, while the alarm buzzer sounds and the switch is turned off to continue the operation, forgetting that the cooling water temperature has already reached the overheat set temperature state, it is as if the machine is in a normal state. If it is mistakenly recognized that the engine is operating and the high load operation is continued for a long time, the cooling water temperature becomes abnormally high and the cooling efficiency of the engine may be significantly reduced, which may cause problems in the engine. I can't deny it.
[0009]
The present invention has been made in view of the above points, and when an overheated state is reached, the alarm means is reliably operated to fully function as a safety device and to an unnecessary level It is an object of the present invention to provide an engine overheat warning device that prevents the occurrence state from continuing.
[0010]
[Means for Solving the Problems]
  In order to achieve the above-described object, the present invention provides a temperature detecting means for detecting the cooling water temperature of the engine, and an alarm when the cooling water temperature reaches the overheat set temperature by the temperature detecting means.AlarmAn overheat alarm device for operating the engine so that the engine operates at least in a state where the cooling water temperature does not rise any further, and an overheat avoidance operation by the overheat avoidance operation unit is performed. And detecting means for detectingThe alarm generating means is composed of an alarm buzzer and an overheat indicator lamp. Among these alarm means, the alarm buzzer detects that the overheat avoiding operation is being performed by the detecting means, and the cooling water temperature is Even if the overheat set temperature is exceeded, the ringing stops, and the overheat indicator lamp continues to light up to the overheat set temperature, and turns off when the overheat set temperature is lowered.It is characterized by having a configuration.
[0011]
The condition for the temperature of the engine cooling water to rise above the overheat set temperature is when the engine is operated at the maximum rotational speed or in the vicinity of the rotational speed, and the load on the engine is extremely high. Therefore, if the engine speed is reduced or the load on the engine is reduced, at least the cooling water temperature will not rise any further, and the temperature can be lowered. Furthermore, it is possible to suppress an increase in the cooling water temperature by improving the cooling efficiency by the radiator. The above operation is an overheating avoidance operation for avoiding overheating. Therefore, the overheat avoiding operation means can be configured by any of a means for reducing the engine speed, a means for reducing the engine load, a means for improving the cooling efficiency, and the like, or a combination of these.
[0012]
For example, even if the cooling water temperature is in the overheat set temperature range, if the engine speed is reduced to some extent, an increase in the cooling water temperature can be suppressed or reduced. Accordingly, as an example of the overheat avoiding operation means, it can be constituted by an engine speed control means. Further, the detecting means for detecting whether or not an overheat avoiding operation is being performed can be configured to detect the engine speed directly or indirectly. Generally, since the engine speed can be detected by the engine speed detecting means, when the engine speed detecting means detects that the engine is below the speed at which overheating is avoided, an alarm means is provided. You can cancel the alarm by. The engine speed control means can be constituted by an engine speed input means. In this case, the alarm should be canceled also by an indirect detection means such as an output signal from the engine speed input means. The engine speed during the overheat avoidance operation can be detected.
[0013]
Here, the rotation speed at which the operation of the alarm means is stopped can be substantially set to the idle rotation speed when set uniformly. Thereby, the cooling water temperature is surely lowered. However, in the idle speed state, the operation of the machine is extremely suppressed. Therefore, the rotational speed higher than the idle rotational speed can be set in consideration of the work efficiency of the machine. In short, it is only necessary to set a rotation speed at which the cooling water temperature does not increase, and the engine rotation speed in the overheat avoidance operation may be equal to or higher than the idle rotation speed. It ’s fine.
[0014]
  As the alarm means, it is preferable to use an alarm buzzer so that the operator can recognize it more directly. Since this alarm buzzer stops when an overheat avoiding operation is performed, the operator cannot recognize whether or not the cooling water temperature has become equal to or lower than the overheat set temperature by the overheat avoiding operation. Therefore, an overheat indicator lamp is provided together with a buzzer constituting an alarm means, and this overheat indicator lamp is configured to be lit as long as it is within the overheat set temperature range even during the overheat avoidance operation.The And when the overheat condition disappears, overheat displayLamp goes offThe
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the overheat avoiding operation will be described as an operation for reducing the engine speed. However, other than this, overheating can be avoided, for example, by reducing the engine load.
[0016]
First, FIG. 1 shows a configuration example of an engine and its cooling mechanism that is usually installed in a hydraulic excavator. In the figure, 1 is a frame of the upper swing body, and 2 is an engine cover. An engine room 3 defined by the engine cover 2 is formed in the upper part of the frame 1 of the upper swing body. An engine 4 is installed 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, and a cooling fan 7 is provided between the engine 4 and the radiator 6. The cooling fan 7 is rotationally driven using the engine 4 or a battery (not shown) as a power source. .
[0017]
  While the engine 4 is operating, the cooling fan 7 is always rotated, an air flow is formed in the engine room 3, cooling air is supplied to the radiator 6, and cooling water passing through the radiator 6 is supplied. Cooling. In order to cool the radiator 6 efficiently,Air flowIn order to form the engine cover 2, an outside air intake 8 and an exhaust 9 are formed in the engine cover 2. The exhaust port 9 may also be formed in the frame 1. With this configuration, as a result of the formation of an air flow as indicated by arrows in the figure, the engine cooling water passing through the radiator 6 exchanges heat with the cooling air, and the temperature of the cooling water We try to reduce it.
[0018]
The cooling water that has cooled the engine 4 is cooled in the radiator 6. However, excessive cooling prevents the engine 4 from operating smoothly, so that the cooling water is kept within a certain 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 coolant temperature is detected and a predetermined set temperature, that is, an upper limit temperature is exceeded, an alarm is issued to the operator. For this purpose, the radiator 6 is provided with temperature detecting means for detecting the cooling water temperature, specifically, a temperature switch that is turned on when the cooling water temperature exceeds the set temperature, and the engine 4 may be overheated. Turn on at a certain overheat set temperature. This is an overheat switch, and an engine overheat alarm device including the overheat switch and an alarm generation means for generating an overheat alarm in conjunction with the overheat switch is configured.
[0019]
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 includes a ROM 14 in which procedures for overheat detection and alarm generation are set. Therefore, when the overheat switch 10 is turned on, that is, when the cooling water temperature exceeds the overheat set temperature, the CPU 13 detects it and issues an alarm according to the procedure set in the ROM 14. As an alarm generating means for generating this alarm, an alarm buzzer 15 is used, and a display lamp 16 for displaying an overheat state is additionally provided.
[0020]
With the above configuration, when the cooling water temperature reaches the overheat set temperature, the alarm buzzer 15 sounds and the display lamp 16 lights up. 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 when it reaches this temperature state, but if 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 if the temperature is not raised above the overheat set temperature, that is, if the temperature is maintained or the temperature is lowered.
[0021]
If the operator performs some kind of operation, the cooling water temperature will not rise any further, and therefore overheating can be avoided. This operation is an overheat avoidance operation, and if the number of revolutions of the engine 4 is reduced, overheat can be avoided. In the first place, the cooling water temperature of the engine 4 rises to exceed the overheat set temperature when the engine 4 is operating at the maximum rotational speed state. When the rotational speed of the engine 4 is reduced, at least the cooling water temperature is increased. If the degree of increase can be suppressed and the rotational speed is further reduced, the temperature will not increase any further. And if the engine falls below a certain number of revolutions, the temperature of the cooling water will fall. Therefore, the engine speed control means of the engine 4 is constituted by an overheat avoidance operation means, and the detection means for detecting whether or not the overheat avoidance operation means has been operated is constituted by an engine speed detection means for detecting the engine speed. Can do.
[0022]
Therefore, as the overheat avoiding operation means, as described below, the rotation speed control means of the engine 4 is used. Thus, 20 indicates a governor, 21 indicates a controller, and 22 indicates an engine speed input means. The governor 20 has a governor lever 20a. The governor lever 20a can be rotated within a range regulated by both stoppers 20U and 20L, and the rotational speed of the engine 4 changes according to the rotational position of the governor lever 20a. To do. When the governor lever 20a rotates toward the stopper 20U, the rotational speed of the engine 4 increases. When the governor lever 20a rotates toward the stopper 20L, the rotational speed of the engine 4 decreases.
[0023]
Here, the engine speed input means 22 has a potentiometer 23, and the potentiometer 23 is configured such that the movable contact 23b is brought into sliding contact with a resistor 23a formed in an arc shape. Furthermore, it has a dial type knob 23c, and an output voltage signal corresponding to the position of the knob 23c is output by rotating the knob 23c by manual operation. The output voltage signal is taken into the controller 21, and a drive signal is inputted from the controller 21 to the motor 24 for rotationally driving the governor lever 20a. By operating the motor 24, the governor lever 20a is rotated. Has been made.
[0024]
The controller 21 includes a power supply circuit 25, a CPU 26, and a ROM 27, and further includes an A / D converter 28 and a motor driver 29. The engine speed input means 22 outputs a voltage signal as a command signal for the engine speed, and the A / D converter 28 converts this command signal into a digital signal. This signal is a command signal for the engine speed, and when this command signal is taken in by the CPU 26, a drive signal is input from the CPU 26 to the motor driver 29 by calculating a drive amount for the motor 24, etc. As a result of the motor 24 operating and the governor lever 20a being rotationally displaced, the rotational speed of the engine 4 is controlled to be a value commanded by the engine rotational speed input means 22.
[0025]
  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. The control device 11 is provided with an A / D converter 30. The A / D converter 30 converts the rotational speed signal of the engine 4 into a digital signal and takes it into the CPU 13. . On the other hand, the rotational speed of the engine 4 necessary for avoiding overheating is preset in the ROM 14. The rotation speed set here is, for example, an idle rotation speed or a slightly higher rotation speed. Note that the rotational speed of the engine 4 at the time of the overheat avoiding operation can be arbitrarily set in relation to the work efficiency or the like on the condition that the cooling water temperature does not increase 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 the temperature does not increase. If the engine 4 reaches the speed at which overheating is avoided, the CPU 13 issues an alarm even if the overheat switch 10 is ON.buzzer15 is controlled to stop ringing. However, the display lamp 16 is not turned off as long as the overheat switch 10 is in the ON state.
[0026]
This embodiment is configured as described above. When the hydraulic pump 5 is driven by operating the engine 4, the pressure oil is supplied to the hydraulic actuators provided in the respective operating parts constituting the hydraulic excavator. Thus, excavation work such as earth and sand is performed by this hydraulic excavator. Thus, when working such as excavation, the engine 4 is held 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 rises, and if it is continuously operated for a very long time, it may eventually exceed the temperature set as the overheat set temperature.
[0027]
When the cooling water temperature exceeds the overheat set temperature, the overheat switch 10 is turned on. As a result, the alarm buzzer 15 is sounded and the display lamp 16 is lit to allow the operator to recognize that an overheating state has occurred. Therefore, when the operator rotates the knob 23c constituting the engine speed input means 22 that functions as an overheat avoiding operation means to reduce the speed of the engine 4, this signal is taken into the control device 11, The alarm buzzer 15 stops ringing as a result of a decrease to the number of rotations at which overheating can be avoided, that is, the number of idle rotations or a number close thereto. However, as long as the overheat switch 10 is in an ON state, the display lamp 16 is kept in a lighting state.
[0028]
As described above, the alarm buzzer 15 stops sounding when the overheat avoiding operation is performed. For example, when the operator waits in a state where the operation of the hydraulic excavator is stopped, the operator may be bothered by an unpleasant buzzer noise. Disappear. Further, since the operation is continued even when the engine 4 is in the idling speed state, the hydraulic oil is pressurized in the hydraulic pump 5. Accordingly, since traveling, turning, and the like are possible, an operation such as moving a hydraulic excavator 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. Then, if the engine speed is reduced to almost the idle speed, the temperature of the cooling water that has been in the overheat set temperature state will decrease, or at least the temperature will not increase any more. Even if such a limited operation is performed, there is no risk of the engine 4 overheating and no damage is caused.
[0029]
By the way, as long as the cooling water temperature is in the overheat set temperature range, the overheat switch 10 is kept in the ON state, and the display lamp 16 is kept in the lighting state accordingly. Of course, the cooling water temperature is lowered by lowering the number of revolutions of the engine 4, but it takes some time to become lower than the overheat set temperature. If the operator increases the rotational speed of the engine 4 during this period, the overheat avoiding operation is interrupted, and the alarm buzzer 15 sounds again. Therefore, there is no possibility of erroneous operation and the function as a safety device is achieved. Will be completed.
[0030]
When the overheat avoidance operation is continuously performed for a predetermined time, the cooling water temperature is lowered from the overheat set temperature. Since the display lamp 16 is turned off at this time, the operator can recognize that the overheating state has been eliminated without delay by checking the display lamp 16. Therefore, when it is confirmed that the display lamp 16 is extinguished, the engine speed input means 22 is immediately operated to return the engine 4 to the maximum speed state. .
[0031]
By the way, the fact that the overheat avoiding operation has been performed is detected based on the signal from the engine speed input means 22. When the engine speed is changed by the engine speed input means 22, the control device 11. As in the first embodiment described above, the output signal of the potentiometer 23 constituting the engine speed input means 22 may be directly taken in, but the CPU 26 constituting the controller 21 substantially does the signal. Since the target rotational speed of the engine 4 is calculated according to a command from the engine rotational speed input means 22, when this target rotational speed is a rotational speed suitable for the overheat avoiding operation, an H level signal or more than that rotational speed is used. When the number of rotations is, an L level signal may be input to the control device 11. For this purpose, as shown in FIG. 3, the CPU 26 on the controller 21 side and the CPU 13 on the control device 11 side may be connected by a wiring 31 so that this signal flows. Therefore, the alarm buzzer 15 is stopped when an H level signal is input to the CPU 13 via the wiring 31 and as long as an H level signal is input to the CPU 13.
[0032]
Further, 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 can be directly taken into the CPU 13 of the control device 11. In this case, the rotational speed of the engine 4 when overheating is avoided is set in the ROM 14 in advance. Further, as shown in FIG. 5, when the sensor 33 for detecting the rotational position of the governor lever 20 a is provided, a signal from the sensor 33 is taken into the control device 11 and output from the sensor 33. Based on the signal, that is, depending on the position of the governor lever 20a, the CPU 13 can determine whether or not the number of revolutions when overheating is avoided, and the operation of the alarm buzzer 15 can be controlled.
[0033]
As the engine speed input means, in addition to the dial type described above, the control lever 42 is used to connect the control lever 40 and the governor lever 41a of the governor 41 by using the control lever 40 as shown in FIG. Some are configured to do so. In this case, the operating lever 40 is the rotation speed control means, and the operating lever 40 is provided with an angle detector 43 for detecting the operating angle, and whether or not the angle detector 43 has been operated to avoid overheating. Function as a detection means. Here, since the rotation position of the governor lever 41 a 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.
[0034]
Therefore, the output signal from the angle detector 43 is compared with the rotational speed at the time of overheating avoidance operation by the comparator 44, and an H level signal is output when the rotational speed is higher than that. This signal and the signal from the overheat switch 10 are ANDed by the AND circuit 45, and the alarm buzzer 15 is in the state that the output signal from the AND circuit 45 is at H level, that is, the overheat switch 10 is ON. When the rotation speed of the engine 4 output from the angle detector 43 is higher than the rotation speed during the overheat avoiding operation, the alarm buzzer 15 is sounded. On the other hand, the indicator lamp 16 is not directly connected to the overheat switch 10, and therefore the indicator lamp 16 is set to the overheat setting as long as the overheat switch 10 is in an ON state regardless of the rotational speed of the engine 4. As long as it is higher than the temperature, it will continue to light up.
[0035]
【The invention's effect】
  As described above, the present inventionThe alarm buzzer and the overheat indicator lamp are used together as an overheat alarm means.While the cooling water temperature reaches the overheat set temperature and an alarm is generated by the alarm means, the overheat avoidance operation is performed so that the cooling water temperature is not increased any more by the overheat avoidance operation means. Even if the cooling water temperature is overheat set temperature,Alarm buzzerCan cancel the alarmThe overheat indicator lamp will remain on until the overheat condition is releasedSince it is configured, it can reliably demonstrate the overheat warning function and prevent the operator from being bothered by unnecessary warning by the warning means.In addition, when overheating is eliminated, the operator can be surely recognized by turning off the display lamp.There are effects such as.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory diagram showing an arrangement configuration of an engine and its peripheral devices.
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]
4 Engine 6 Radiator
10 Overheat switch 11 Control device
15 Alarm buzzer 16 Indicator lamp
20, 41 Governor 20a, 41a Governor lever
21 controller 22 engine speed input means
23 Potentiometer 24 Motor
31 Wiring 32 Speed detector
33 Sensor 40 Operation lever
42 Control cable 43 Angle detector
44 Comparator 45 AND circuit

Claims (4)

In an engine overheat alarm device comprising temperature detection means for detecting the cooling water temperature of the engine, and alarm means for warning when the cooling water temperature reaches the overheat set temperature by this temperature detection means,
An overheat avoidance operation means for operating the engine in a state where at least the cooling water temperature does not rise any more, and a detection means for detecting that an overheat avoidance operation by the overheat avoidance operation means is performed,
The alarm means includes an alarm buzzer and an overheat indicator lamp,
Among these alarming means, when the alarm buzzer detects that the overheating avoidance operation is being performed by the detecting means, the alarm buzzer stops its sounding even when the cooling water temperature exceeds the overheat set temperature, and the overheating The engine overheat warning device characterized in that the display lamp continues to be lit until the overheat set temperature and is turned off when the display lamp becomes lower than the overheat set temperature .   The overheat avoiding operation means is composed of an engine speed control means, and the detecting means is configured to detect that the engine speed is such that overheating is avoided by the speed control means. The engine overheat warning device according to claim 1, wherein   The engine speed control means includes engine speed input means, and is configured to detect the engine speed based on an output signal from the engine speed input means. The engine overheat alarm device described. 3. The engine overheat warning device according to claim 2, wherein the engine speed at which the alarm buzzer stops ringing is set to an almost idle speed.

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