JPS6357317A - Automatic changeover switch for car cooler - Google Patents

Abstract

PURPOSE:To make it possible to surely stop a car cooler, by moving a partitioning member for sectioning a plurality of pressure receiving chambers in a switch body, in accordance with the negative pressure of intake-air only during accelerating operation of an engine, so that an electric circuit for a magnet clutch is opened. CONSTITUTION:A switch body 10 is sectioned into a plurality of pressure receiving chambers 12, 13 by means of a partitioning member 11 which is provided therein with a switch opening and closing member 14. Further, in the second pressure receiving chamber 13, there are provided a plurality of terminals A, B, as switches, which are connected to an electric circuit 7 for a magnet clutch 3. Further, the pressure receiving chambers 12, 13 are communicated with negative pressure introduction passages 15 17, 18, the second negative pressure introduction passage 17 being provided therein with a construction 19 and the third negative pressure introduction passage 18 being disposed therein with a check valve 20 for allowing air to flow only from the first pressure receiving chamber 12 to an intake-air passage 5. Further, only during accelerating operation of an engine, the partitioning member 11 is moved toward the first pressure receiving chamber 12 in accordance with the negative pressure to open an electric circuit 7, thereby a compressor 2 is stopped.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a system in which components such as a compressor, a condenser, a liquid tank, an expansion valve, an evaporator, etc. are connected by hoses, and a refrigerant is circulated between these components. This relates to a car cooler that exerts a cooling effect by continuously changing liquid-gas-liquid.
In particular, the present invention relates to an automatic changeover switch for a car cooler that is connected to an electric circuit of a magnetic clutch attached to a compressor in such a car cooler.

[Conventional technology]

In a car cooler, the compressor used to circulate refrigerant receives engine rotational force through a magnetic clutch attached to the compressor. Closing the main switch for the cooler closes the electric circuit of the magnetic clutch. The rotational force of the engine is applied to the shaft of the compressor through the clutch plate of the magnetic clutch, driving the compressor, thereby creating a cooler effect.

According to such a car cooler, when the main switch for the cooler is closed, the car cooler is always in operation during driving unless the switch is released to open the electric circuit of the magnetic clutch.

According to this, a part of the engine output is used to drive the compressor, and all of the engine output cannot be used to drive the vehicle, so the acceleration operation of the engine, which requires instantaneous large output, is facilitated. There is a problem that it cannot be done. In order to solve this problem, an automatic switch is placed in the electric circuit that automatically opens the electric circuit of the magnetic clutch without operating the main switch for the cooler when the engine is accelerating. Automatic cutting technology has been proposed. Specifically, it is disclosed in Japanese Unexamined Patent Publication No. 57-130816 for an automatic switch for a car cooler.

According to this, a diaphragm divides the chamber into a pressure receiving chamber and an atmospheric chamber, and the negative pressure of the intake manifold of the engine is introduced into the pressure receiving chamber, and a spring that presses the diaphragm is installed on the atmospheric chamber side. The diaphragm is integrally provided with an opening/closing member for opening and closing the switch, thereby forming an automatic changeover switch, and this automatic changeover switch is connected to the electric circuit of the magnetic clutch. According to a car cooler having such an automatic changeover switch, when the negative pressure in the intake passage decreases when the engine is accelerating, the spring in the pressure receiving chamber expands and the diaphragm moves toward the atmospheric chamber, and this movement causes the opening/closing member to open and close. The switch is automatically released, and the clutch plate of the magnetic clutch is operated to put the engine and compressor in a non-transmitting state, allowing all of the engine's output to be used to drive the vehicle, which accelerates the vehicle. This allows for smooth driving.

[Problems to be Solved by the Invention] However, the conventional automatic changeover switch for a car cooler has the following problems.

■The operating point of the automatic changeover switch's diaphragm (including the opening/closing member that opens and closes the switch) only operates when the intake airway negative pressure is below a certain level. If we look at the intake tract negative pressure during engine operation, we find that during normal operation, the throttle valve of the carburetor is fully open and the engine speed is low, so-called fully open. During low-speed operation, specifically when continuously climbing a slope with heavy loads loaded, the negative pressure in the intake tract decreases significantly, and the automatic changeover switch must not operate under such operating conditions. For this reason, the intake tract negative pressure at the starting point of the automatic changeover switch must be below this value, and it is required to set a low intake tract negative pressure, so the setting range of the intake tract negative pressure is limited and free. There are few degrees.

■Based on the above, the operating point of the automatic changeover switch is that it cannot be operated at least until the intake air pressure drops below the negative pressure in the normal operating range, and especially from the beginning of acceleration when it is necessary to use the engine output effectively. It is difficult to disable the car cooler and it is not possible to completely solve the problem of smooth acceleration driving.

Acceleration operation of a 0 engine includes a slight acceleration operation in which the throttle valve is opened from a low throttle valve opening to an intermediate opening ratio, but at this time the negative pressure in the intake passage cannot be expected to decrease significantly, and the engine is fully opened. It may be higher than the intake tract negative pressure during low speed operation. (See FIG. 2) In such a state, the car cooler cannot be brought into an inoperative state, resulting in the same problem as described above.

■The automatic changeover switch can only start and end its operation at the intake tract negative pressure setting point, and there is little freedom in setting the operating time, especially this.

This is a problem when accelerating a relatively small displacement vehicle such as 1300cc or 1500cc, and the car cooler cannot be kept inactive until the acceleration is complete so that the full output of one engine cannot be used to drive the vehicle. There is a problem.

[Means for solving problems]

The automatic changeover switch for a car cooler according to the present invention has been developed in view of the above-mentioned problems, and is capable of reliably disabling the car cooler and providing the engine output to the vehicle operation during any acceleration operation, as well as ensuring that the car cooler is inactive during any acceleration operation. The purpose of the present invention is to provide a highly practical automatic changeover switch for a car cooler that can appropriately set the inoperation time of the car cooler depending on the output of the engine and other factors. is divided into a first pressure receiving chamber and a second pressure receiving chamber, and the first pressure receiving chamber is provided with an elastic member that presses the partition body toward the second pressure receiving chamber side, and the partition body is configured to open and close an electric circuit of a magnetic clutch. A switch opening/closing operation member that provides opening/closing operation to the switch is arranged, while the intake passage negative pressure on the engine side is introduced into the second pressure receiving chamber from the throttle valve, and the throttle valve is introduced into the first pressure receiving chamber through the passage restricting member. This introduces more negative pressure in the intake tract on the engine side.

[Effect]

According to such an automatic changeover switch for a car cooler, when the engine is accelerating, the intake passage negative pressure temporarily decreases, and the pressure in the second pressure receiving chamber decreases in synchronization with the accelerating operation.

On the other hand, the high intake airway negative pressure that occurred during normal operation of the engine still remains in the first pressure receiving chamber, and a pressure difference occurs between the first pressure receiving chamber and the second pressure receiving chamber, and this pressure difference causes the The partition moves toward the first pressure receiving chamber by overcoming the tension of the elastic member in the first pressure receiving chamber.

As a result of this movement, the switch is opened by the switch opening/closing member, and thereafter, the negative pressure in the first pressure receiving chamber leaks through the passage restricting member, until the negative pressure in the first pressure receiving chamber is defeated by the tension of the elastic member. The switch is held open, and when the negative pressure in the first pressure receiving chamber is overcome by the tension of the elastic member, the partition returns to the second pressure receiving chamber side by the elastic member, and the switch is returned to its original position by the switch opening/closing member. When the switch is opened, the magnetic clutch is disengaged and the car cooler becomes inactive, and when the switch is closed, the magnetic clutch is connected again, putting the car cooler into operation.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the automatic changeover switch for a car cooler according to the present invention will be described with reference to FIG.

The structure of a car cooler is already known and consists of main components such as a compressor, a condenser, a liquid tank, an expander valve, an evaporator, etc. Engine 1 and compressor 2 are shown in the figure. The compressor 2 has a mechanism for circulating refrigerant in a refrigeration cycle, and is connected to the output shaft of the engine 1 via a magnetic clutch 3. The magnetic clutch 3 transfers the rotational force of the output shaft of the engine 1 to the rotation shaft of the compressor 2.
It is a device that switches between transmission and non-transmission states, and when the magnetic coil of the magnetic clutch 3 is energized, the clutch plate is attracted and the rotational force of the engine is transmitted to the rotating shaft of the compressor 2, thereby operating the compressor 2. When the magnet coil is no longer energized, the clutch plate separates and the rotational force of the engine is not transmitted to the rotating shaft of the compressor 2, making the compressor 2 inoperative.

Further, 4 is a carburetor for controlling the supply of air-fuel mixture to the engine 1, and an intake passage 5 connected to the intake hole of the engine 1 has a rotatable throttle valve 6 for controlling the amount of air. The opening and closing of this throttle valve 6 is controlled by the driver. Further, 7 is an electric circuit of the magnetic clutch 3, and a main switch 8 for the cooler is disposed within the electric circuit. Note that the above-mentioned components are generally known.

The automatic changeover switch S for a car cooler according to the present invention is connected to the electric circuit of the magnetic clutch 3.

An embodiment of the automatic switching switch 7S for a car cooler will be described below. Reference numeral 10 denotes a switch body, and a switch opening/closing member 14 made of a conductive material is integrated into the zero compartment body 11 which is divided into a first pressure receiving chamber 12 and a second pressure receiving chamber 13 by a compartment body 11 such as a diaphragm. placed in
A second pressure receiving chamber 1 facing the switch opening/closing member 14
Terminals A and B as switches are provided protrudingly inside 3, and these terminals A and B are connected to the electric circuit 7 of the magnetic clutch 3.

Further, the intake passage negative pressure in the intake passage 5 on the engine side from the throttle valve 6 is introduced into the second pressure receiving chamber 13 via the first negative pressure introduction passage 15. An elastic member 16 such as a spring is compressed in the first pressure receiving chamber 12, and the elastic member 16 allows the partition body 11 to
is pressed toward the second pressure receiving chamber 13 (to the right in the figure).

Further, the first pressure receiving chamber 12 is connected to the intake passage 5 on the engine side from the throttle valve 6 via the second negative pressure introduction path 17, and the third
It is connected to the engine-side intake passage 5 via a negative pressure introduction passage 18 . A passage restricting member 19 such as an orifice, for example, for restricting the passage of the second negative pressure introduction passage is disposed in the second negative pressure introduction passage 17, and a passage restricting member 19, such as an orifice, is disposed in the second negative pressure introduction passage 17.
A one-way check valve 20 that only allows flow from the first pressure receiving chamber 12 to the intake passage 5 is disposed within the intake air passage 8 .

The adjustment screw 21 is screwed onto the switch body 10, and its end is brought into contact with the end of the elastic member 16 via a collar 22.

Next, with reference to FIG. 2, the negative pressure in the intake passage 5 on the engine side from the throttle valve 6 with respect to the driving pattern of the vehicle will be explained. First, point A is when the engine is stopped, and when one engine is driven and idling, the score is 8 points - 0 points.
Next, when the engine is accelerated, the intake passage negative pressure temporarily drops to point D. After that, when the throttle valve 6 enters low opening operation, the intake passage negative pressure rises to point E, and the intake passage negative pressure between points E and F decreases. Maintain pressure.

Next, when the throttle valve 6 is partially opened and acceleration is performed, the intake tract negative pressure at the G point decreases from the F point. During accelerated driving,
The reason why the intake tract negative pressure decreases at points D and G is different is that the opening ratio of the throttle valve 6 differs during acceleration, and the larger the opening, the greater the decrease in the intake tract negative pressure. and G
When the throttle valve 6 enters intermediate opening operation after the negative pressure in the intake duct has decreased, the H point - 3 point is maintained, and then when the engine decelerates to idling operation, the engine rotation continues even though the throttle valve 6 is closed. Since the engine is rotating at a high speed due to inertial force, the intake passage negative pressure rises to point , and then becomes the intake passage negative pressure at point L-M during idling operation.

Next, when the throttle valve 6 is opened to a high opening and accelerated, the temperature drops to the N point, and after that, when the engine enters full-open low-speed operation, it becomes the 0 point - the P point. The reason why the intake passage negative pressure at point 0-P is lower than in other operating ranges except for acceleration operation is because the throttle valve 6 is fully opened.
Moreover, this is due to the low rotation of the engine.

Note that the intake tract negative pressure value at each point is based on a diagram, and this value changes depending on engine performance, gear, vehicle weight, etc. In the case where the intake passage has a negative pressure characteristic for engine operation, the elastic characteristic of the elastic member 18 is such that the pressure difference between the first pressure receiving chamber 12 and the second pressure receiving chamber 13 is 1150 H.
g, the partition body 11 is moved to the first pressure receiving chamber 12 side (first
It is set so that it can move to the left side in the figure.

Next, the operation will be explained along the operating modes shown in FIG.

Main switch for cooler 8 when starting the engine
When the engine 1 is started with the engine 1 closed and the engine is brought into a fitting operation state, the negative pressure in the intake passage which was at point A in the atmospheric pressure state is maintained at 1500 Hg (point 3-0).

The first pressure receiving chamber 12 and the second pressure receiving chamber of the automatic changeover switch S for the cooler before starting! 3 is maintained at atmospheric pressure, but due to the generation of the intake passage negative pressure, intake passage negative pressure is introduced into the second pressure receiving chamber 13 and the first pressure receiving chamber 12 from each negative pressure introduction path 15, 17, and 18. Both pressure receiving chambers 12 and 13
Since an equal inspiratory tract negative pressure of −500 μHg was introduced into the interior of the compartment 11, the tension of the elastic member 1B causes the compartment 11 to
is pressed toward the second pressure receiving chamber (right side in the figure), and the switch opening/closing member 14 is pressed and held against the terminals A and B. In this state, the electric circuit 7 of the magnetic clutch 3 forms a closed circuit. As a result, the rotational force of the engine 1 drives the compressor via the magnetic clutch 3, thereby producing a cooling effect.

Next, when accelerating operation is performed by opening the throttle valve 6 to a high opening degree from the 0 point of idling operation, the intake passage negative pressure in the intake passage 5 decreases to an atmospheric pressure of about < -10 mmHg as shown at point D, and then The throttle valve 6 enters a low-opening operation (for example, running at 40 km/h) and the intake passage negative pressure is raised and returned to 400 mm Hg between points E and F.

During this acceleration operation, the intake passage negative pressure in the intake passage 5 is -500 m
The change in the negative pressure in the intake passage is immediately introduced into the second pressure receiving chamber 13 via the first negative pressure introduction path 15, and the pressure in the second pressure receiving chamber 13 decreases from mHg to 110 lHg. It lowers the temperature to -10mmHg.

On the other hand, in the first pressure receiving chamber 12, a passage restricting member 13 is disposed in the second negative pressure introduction path 17, and a third negative pressure is introduced from the first pressure receiving chamber 12 into the third negative pressure introduction path 18. Road 1
Since the one-way check valve 20 is disposed to allow flow only to the first pressure receiving chamber 12, the intake tract negative pressure of −500 mm Hg during the fitting operation is still maintained within the first pressure receiving chamber 12. According to this, the first pressure receiving chamber 12 and the second pressure receiving chamber 13
Theoretically, the differential pressure between the
00mmHg) -(-10mmHg) ) (7)
This is caused by negative pressure in the intake tract.

According to this, the pressure difference between both pressure receiving chambers 12 and 13 is 1150.
■■Hg or higher, the partition 11 moves toward the first pressure receiving chamber 12 (to the left in the figure) against the tension of the elastic member 1B, and the switch opening/closing member 14 is connected to the terminal A,
B, and the electric circuit 7 of the magnetic clutch 3 is opened, so that the drive of the compressor 2 can be automatically stopped.

When operating such a switch, special attention must be paid to the first point. The pressure difference between the second pressure receiving chamber 12 and 13 is -
When the temperature exceeds 150 mmHg, the partition body 11. This means that the switch opening/closing member 14 operates. This means that during the acceleration operation, the negative airway pressure decreases by 1,350 mm Hg during the process where the negative airway pressure decreases from point 0 to point D (the differential pressure between the first and second pressure receiving chambers 12 and 13 150 meals mH
g), the driving of the compressor 2 can be stopped, and the output of the engine 1 can be used to drive the vehicle from the initial stage of acceleration.

On the other hand, in such a state, the high intake passage negative pressure remaining in the first pressure receiving chamber 12 gradually leaks into the second negative pressure introducing passage 17 via the passage restricting member 19, and the throttle valve 6 is opened at a low level. In the process of returning to point E during operation, the first pressure receiving chamber 1
2 and the second pressure receiving chamber 13 is -150 mm Hg or less, the tension of the elastic member 16 causes the partition 11 to move the switch opening/closing member 14 toward the second pressure receiving chamber (to the right in the figure). A throttle valve that maintains 0 to 400 mm Hg is brought into contact with terminals A and B to close the electric circuit 7 of the magnetic clutch 3 again, thereby driving the compressor 2 and reproducing the cooling effect. To explain the acceleration operation state (slight acceleration) from the low opening operation of the throttle valve 6 to the intermediate opening operation of the throttle valve 6 (for example, running at 80 km/H), the intake path negative pressure is -4.
It changes from the F point of 00 Hg to the G point of 1200 Hg, and then holds the H point - 1 point in the intermediate opening operating state.

In this short acceleration operation, the intake tract negative pressure acts on each pressure receiving chamber as in the above state, and when the differential pressure between both pressure receiving chambers becomes -150++vHg or more during the acceleration process, the magnetic clutch 3 The electric circuit 7 of the magnetic clutch 3 is opened to keep the cooler in a non-operating state, and then when the differential pressure between the two pressure receiving chambers becomes less than 1150 mm, the electric circuit of the magnetic clutch 3 is closed again to put the cooler in an operational state.

Then, when decelerating from the intermediate opening operating state to idling, the engine still maintains high rotation due to inertia even though the throttle valve 6 is closed at the idling opening 2, so the negative pressure in the intake passage rises sharply. Then, as the rotation of the engine decreases, a negative pressure in the intake tract occurs during idling operation, such as at point L-point M.

In this state, the negative pressure inside the intake passage 5 is
00 mHg to -800 msHg at the point, and the difference in the negative pressure in the intake passage -500 mHg flows from the first negative pressure introduction path 15 to the second pressure receiving chamber 13, and the second negative pressure Introduction route! ? and from the third negative pressure introduction path 18 to the first pressure receiving chamber 1
In particular, the one-way check valve 20 acts on this -5.
The third negative pressure introduction path 1 receives the intake path negative pressure of 00++nHg.
8 and the first pressure receiving chamber 12 are connected through a large opening. Therefore, since the same intake tract negative pressure acts in both pressure receiving chambers 12 and 13, the partition body 11 is pressed toward the second pressure receiving chamber 13, and the switch opening/closing member 14 keeps the electric circuit 7 of the magnetic clutch 3 closed. This is Shiuruchino.

Next, when the engine is accelerated from idling,
The intake passage negative pressure decreases to the N point, and when the engine enters full-open low-speed operation thereafter, the intake passage negative pressure becomes between the 0 point and the 2 point.

This acceleration operation is the same as the acceleration state from point C to point D, so the explanation will be omitted.

In addition, during such full-open low-speed operation, the throttle valve 6 is fully opened and the engine rotation is low, so the negative pressure in the intake passage 5 is -100 ts Hg. Since it is operated with differential pressure, there is no possibility of malfunction.

Furthermore, the one-way control valve 20 disposed within the third negative pressure introduction passage 18 can be effective in speeding up the response when the pressure within the intake passage 5 increases; however, the passage restricting member 19
It is also possible to eliminate this by appropriately setting the diameter of the aperture.

Further, the switch opening/closing member 14 and the switch portions of the terminals A and B are not limited to those in this embodiment, and may be changed to switches such as a magnet switch or a reed switch.

Further, the automatic changeover switch for the cooler shown in FIG. 3 will be explained.

Components with the same structure as those in FIG. 1 are designated by the same reference numerals and their explanations are omitted. 20 is a first air chamber isolated from the first pressure receiving chamber 12, and 21 is isolated from the second pressure receiving chamber 13. The second air chamber 21 is connected to the second pressure receiving chamber 13 through a communication hole 22, and is also connected to the intake passage 5 on the engine side via the throttle valve 6 through a negative pressure introduction path 23. Ru.

Further, the first air chamber 20 and the first pressure receiving chamber 12 are connected through a communication path 24, and the first air chamber 20
0 and the second air chamber 21 have a communication passage 28 in which a passage restricting member 25 is disposed, and a one-way check valve 27 that only allows flow from the first air chamber 20 to the second air chamber 21. The communication path 28 is arranged.

Incidentally, reference numeral 28 denotes a switch opening/closing member made of a permanent magnet disposed in the partition body 11, and is disposed corresponding to the reed switch 30. According to such an automatic changeover switch, the changeover operation is the same as that shown in FIG. The chattering phenomenon in which the switch operation repeatedly opens and closes can be completely suppressed without directly acting on the partition body 11.

Further, the operation time for the partition body 11 to move to the first pressure receiving chamber 12 side and return to the second pressure receiving chamber 13 side depends on the throttling effect of the passage restricting member 25, but the return operation time is By appropriately selecting the diameter of the passage restricting member 25 and the volume of the air chambers 20 and 21 at the time of setting, the degree of freedom in setting the return operation time can be greatly increased. Furthermore, the piping between the intake passage 5 and the cooler automatic changeover switch S can be made into a single piece, and the other passages can be housed inside the main body, allowing for greater freedom in installation in the engine room. This not only improves performance but also reduces installation work time.

〔Effect of the invention〕

As described above, the automatic changeover switch for a car cooler according to the present invention can produce the following special effects.

■The automatic changeover switch starts operating in the first step. Since the partition body is moved by the differential pressure in the second pressure receiving chamber, it can respond to acceleration from any driving condition, and in particular, the throttle valve, which is often used in city driving, can be operated at a low opening. The switch was able to operate reliably even during accelerated operation, from opening to an intermediate opening.

■Also, as mentioned above, by operating the partition body using differential pressure, it can be used even in situations where the intake tract negative pressure drops significantly and approaches the intake tract negative pressure during acceleration operation, especially when the engine is running at full throttle and at low speed. This eliminates erroneous operation of the switch, and this makes it possible to extremely easily set the operation of the automatic changeover switch over a wide range.

■Furthermore, by making the partition respond according to this differential pressure, the pressure difference is based on the steady operating state before acceleration, and the engine operates with the differential pressure relative to that, so the cooler is deactivated from the beginning of acceleration operation. 1 to drive the vehicle
It is 00% usable and allows smooth acceleration operation.

■During acceleration operation, the time for which the cooler is kept inactive can be freely set by selecting the diameter of the passage restrictor or the capacity of the air chamber, especially for small displacement ratios. This is effective when 100% of the engine output is expected to be used for vehicle operation until the end of acceleration.

■ By arranging a one-way check valve that only allows flow from the first pressure receiving chamber to the negative pressure introduction path side in the passage between the first pressure receiving chamber and the negative pressure introduction path, the This makes it possible to maintain the pressure in the first pressure receiving chamber at the same pressure as the pressure in the second pressure receiving chamber without any time delay, thereby improving operational responsiveness.

- By communicating with each pressure receiving chamber via an air chamber, it is possible to rectify the pulsating pressure in the intake passage and increase the degree of freedom in selecting the return time of the switch.

[Brief explanation of the drawing]

FIG. 1 is a system diagram including a sectional view of essential parts showing an embodiment of an automatic changeover switch for a car cooler according to the present invention. FIG. 2 is a diagram showing the intake passage negative pressure in each operating state, and FIG. 3 is a longitudinal sectional view showing another embodiment of the automatic changeover switch. 1019 institutions, 209. compressor. 310. Magnetic clutch, S90. Automatic changeover switch for cooler, 11. ,, compartment body. 12., first pressure receiving chamber, 13. ,, second pressure receiving chamber, 14
,,, switch opening/closing operation member, 113. ,',elastic member, 19. ,, passage restricting member, 20. ,,One-way check valve.

Claims (3)

[Claims] 1. In a car cooler that has a compressor that circulates refrigerant and a magnetic clutch that turns engine torque on and off to the compressor, a partition body divides the switch body into a first pressure receiving chamber and a second pressure receiving chamber, and the switch body is divided into a first pressure receiving chamber and a second pressure receiving chamber. An elastic member for pressing the partition toward the second pressure receiving chamber is arranged in the first pressure receiving chamber, and a switch opening/closing member is arranged in the partition for imparting an opening/closing operation to a switch for opening/closing the electric circuit of the magnetic clutch. The engine-side intake passage negative pressure is introduced into the second pressure receiving chamber through the throttle valve, and the engine-side intake passage negative pressure is introduced into the first pressure receiving chamber via the passage restriction member through the throttle valve, thereby accelerating the engine. An automatic changeover switch for a car cooler that opens and closes the electric circuit of a magnetic clutch by moving the partition only during driving. 2. In a car cooler that has a compressor that circulates refrigerant and a magnetic clutch that turns engine torque on and off to the compressor, a partition body divides the switch body into a first pressure receiving chamber and a second pressure receiving chamber, and the switch body is divided into a first pressure receiving chamber and a second pressure receiving chamber. An elastic member for pressing the partition toward the second pressure receiving chamber is arranged in the first pressure receiving chamber, and a switch opening/closing member is arranged in the partition for imparting an opening/closing operation to a switch for opening/closing the electric circuit of the magnetic clutch. The intake passage negative pressure from the engine side is introduced into the second pressure receiving chamber through the throttle valve, and the intake passage negative pressure from the engine side is introduced from the throttle valve into the first pressure receiving chamber through the passage restricting member. A one-way check valve that only allows flow from the first pressure receiving chamber to the intake duct is placed in the negative pressure introduction path that connects the intake duct on the engine side from the throttle valve, and only during engine acceleration operation. An automatic changeover switch for a car cooler that opens and closes the switch opening/closing member by moving the compartment and opens the electric circuit of the magnetic clutch. 3. In a car cooler that has a compressor that circulates refrigerant and a magnetic clutch that turns engine torque on and off to the compressor, a partition body divides the switch body into a first pressure receiving chamber and a second pressure receiving chamber, and the switch body is divided into a first pressure receiving chamber and a second pressure receiving chamber. An elastic member for pressing the partition toward the second pressure receiving chamber is arranged in the first pressure receiving chamber, and a switch opening/closing member is arranged in the partition for imparting an opening/closing operation to a switch for opening/closing the electric circuit of the magnetic clutch. A first air chamber and a second air chamber are provided isolated from the first and second pressure receiving chambers, the second air chamber is connected to the intake passage on the engine side from the throttle valve, and the second air chamber and the second air chamber are connected to the intake passage on the engine side from the throttle valve. communicating with the pressure receiving chamber, communicating the second air chamber with the first air chamber via a passage restricting member,
The first air chamber communicates with the second air chamber through a one-way check valve that only allows flow from the first air chamber to the second air chamber, and further communicates the first air chamber with the first pressure receiving chamber, so that the first air chamber is separated only during acceleration operation of the engine. An automatic changeover switch for car coolers that opens and closes the switch by moving the body and opens the electric circuit of the magnetic clutch.