JPH0788815B2 - Diaphragm type vacuum pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diaphragm-type vacuum pump that obtains a necessary negative pressure by displacing a diaphragm, and more particularly to a diaphragm-type vacuum pump that suppresses a diaphragm driving torque to a small value. This type of diaphragm type vacuum pump is, for example, as a negative pressure source for securing negative pressure when the engine negative pressure is insufficient.
It is used for a vacuum type automatic drive system or a brake booster.

[Prior Art] An example of the use of this type of diaphragm type vacuum pump is an auto drive system.

When the driver sets the desired vehicle speed, the auto drive system that automatically controls the vehicle speed to maintain a constant speed without stepping on the accelerator pedal has a control method that uses the rotation of the motor to adjust the throttle opening. There are a motor type for controlling and a vacuum type for controlling the throttle opening by utilizing engine vacuum, and the diaphragm type vacuum pump of the present invention is used for the latter and the like.

Examples of this type of diaphragm type vacuum pump include Japanese Utility Model Publication No. 50-155610 and Japanese Utility Model Publication No. 58-36867. The diaphragm-type vacuum pumps described in these documents reciprocate the diaphragm to obtain a required negative pressure when the vacuum pressure reaches a predetermined value.

The case where this type of diaphragm type vacuum pump is used in a vacuum type automatic drive system will be further described in detail with reference to the system diagram of the vacuum type automatic drive system in FIG.

Normally, the negative pressure of the intake manifold 1 is set to a negative pressure in the manifold chamber 10a of the vacuum pump 10 by the pipe 2, the valve 11 is opened, the negative pressure is set in the actuator chamber 10b, and the negative pressure is introduced to the actuator 5 by the pipe 4. . In order for the actuator 5 to pull the accelerator link by this negative pressure, a pressure equal to or lower than a predetermined arbitrary pressure (this is ammHg) is necessary. The actuator 5 controls the opening degree of the throttle valve 7 by the controller 6. When the required negative pressure of the actuator 5 cannot be obtained only by the negative pressure of the intake manifold 1, the vacuum switch 8 detects it and
The detection signal is sent to the controller 6. The negative pressure insufficient signal is sent to the motor 12 of the drive source of the vacuum pump 10, the motor 12 rotates the crankshaft of the vacuum pump 10, the diaphragm 13 moves up and down,
Along with this, the valves 14 and 15 open and close to further reduce the negative pressure in the actuator chamber 10b, and the actuator 5
Supply negative pressure to.

The required capacity of the vacuum pump 10 at this time is sufficient if a negative pressure equal to or higher than the set pressure a can be generated at the maximum consumption flow rate of the actuator 5. Therefore, a vacuum pump having pump characteristics as shown in Fig. 10 is used.

[Problems to be Solved by the Invention] However, this type of diaphragm type vacuum pump 10
As can be seen from the characteristic diagram, when the flow rate consumed by the actuator 5 decreases, the generated negative pressure increases,
In particular, when the vacuum pump 10 is activated, the motor 12
Since a large load is applied to the motor 12, it becomes necessary to increase the torque of the motor 12. As a matter of course, there was a problem that the motor became large and had to be durable.

On the other hand, in the case of a vacuum pump, the technology to prevent the lubricating oil in the vacuum pump from moving to the depressurized side by introducing air into the vacuum line by stopping the vacuum pump is a practical application. It is disclosed in Japanese Patent No. 59-58781. However, this kind of technology is operated in a state where the vacuum pump is stopped, and cannot be dealt with when the vacuum pump is overloaded. Therefore, as in the former case, when the load on the vacuum pump increases, a large load is applied to the drive source, and it becomes necessary to increase the torque of the drive source. As a matter of course, there is a problem that the drive source motor becomes large in size and must be durable.

Therefore, an object of the present invention is to provide a diaphragm-type vacuum pump in which the output fluctuation of the drive source is reduced and the drive source is miniaturized regardless of the load fluctuation.

[Means for Solving the Problems] The present invention is directed to a suction check valve for introducing gas into the pump chamber from the outside in a volume increasing process of the pump chamber whose volume increases and decreases due to the reciprocating movement of the diaphragm, and the volume of the pump chamber. A discharge check valve that discharges the gas in the pump chamber to the outside in the reduction stroke, and a drive source that is constantly connected to the diaphragm to reciprocally displace the diaphragm are provided, and the difference between the negative pressure and the atmospheric pressure in the pump chamber. The pressure always urges the valve to open, and the spring normally urges the valve to close.When the differential pressure is about to exceed a predetermined value, atmospheric pressure is introduced into the pump chamber to cause the differential pressure. In order to maintain the pressure at a predetermined value, a relief valve that connects the two is installed at a position that simultaneously receives the pressure inside the pump chamber and the atmospheric pressure. It is a thing.

[Operation] According to the above configuration, when the diaphragm moves and the pump chamber is depressurized to a predetermined pressure, the relief valve guides the atmosphere to the pump chamber, and the pump chamber is depressurized more than necessary. And the load on the drive source is reduced to a predetermined value or less.

[Embodiment] FIG. 1 is a sectional view of the essential parts of a diaphragm type vacuum pump according to a first embodiment of the present invention.

In the figure, a pump chamber A is formed between a diaphragm 23 made of a flexible material such as rubber and a second housing 26. The peripheral portion of the diaphragm 23 is sandwiched between the third housing 27 and the second housing 26. The holding pressure of the peripheral portion is determined by the first housing 28 and the third housing.
Although it is obtained by screwing 27, the first housing 28 and the second
It may be obtained by screwing the housing 26 and the third housing 27 together. Also, other fixing means may be used. The end of the connecting rod 29 is fixed to the center of the diaphragm 23, and the other end of the connecting rod 29 is connected to the crankshaft 37. The crankshaft 37 is rotatably supported by the shaft of the motor 22, acts as a crankshaft of the vacuum pump 20, and vertically moves the connecting rod 29 as the motor 22 rotates. The fixed portion between the connecting rod 29 and the diaphragm 23 is
Not only is the connecting rod 29 simply moved up and down, but also it swings to the left and right, so that the fixing does not simply unite the end of the connecting rod 29 and the diaphragm 23, but the swinging does not damage the diaphragm 23. The structure. The motor 22 of the drive source may be electromagnetic drive means that reciprocates with a solenoid.

The second housing 26 also includes a check valve 24 for suction.
And a check valve 25 for discharge, a relief valve 40 is arranged on the side of the check valve 25 for discharge, and an orifice 31 for communicating the pump chamber A with the atmosphere.
Has been drilled.

Between the intake port 32 connected to the actuator and the exhaust port 33 connected to the intake manifold, the exhaust check valve equipped on the valve mounting member 34 that opens and closes due to the negative pressure of the intake manifold.
21 is provided and the actuator has an intake port 32,
The negative pressure of the intake manifold is introduced through the exhaust check valve 21 and the exhaust port 33. Also, install a filter between the exhaust port 33 and the exhaust check valve 21.
35 are provided.

The chamber for introducing the negative pressure of the intake manifold formed between the exhaust port 33 and the exhaust check valve 21 is hereinafter referred to as the exhaust chamber B.

Between the intake port 32 and the exhaust port 33, a chamber for introducing a negative pressure to the actuator is formed between the exhaust check valve 21 forming the exhaust chamber B, the valve mounting member 34, and the second housing 26. . Hereinafter, the chamber is referred to as the intake chamber C.
Call.

In order to seal the intake chamber C, the second housing 26 and the first housing 26
An O-ring 36 is interposed between the housings 28. As shown in the sectional view of the relief valve 40 of FIG. 2, the relief intake valve 41 seals the relief intake port 41 with the valve element 44 pressed by the spring 42, so that the pressure in the pump chamber A is
When the pressure drops below atmospheric pressure and reaches the specified pressure difference, the valve element 44
Is lowered against the pressing force of the spring 42 to guide the atmosphere to the pump chamber A. Further, the second housing 26 is provided with an orifice 31 which always connects the atmosphere and the internal pressure of the pump chamber A with an arbitrary fluid resistance.

Exhaust check valve 21, intake check valve
The 24 and the discharge check valve 25 are known rubber type valve bodies, have a support portion in the central portion, and are configured such that the communication hole is opened and closed by the umbrella portion around the support portion.

The vacuum pump shown in FIGS. 1 and 2 configured as described above can operate as follows. The negative pressure of the intake manifold is supplied to the exhaust chamber B via the exhaust port 33.
Is set to a negative pressure, the exhaust check valve 21 is opened, and the negative pressure is guided to the actuator via the intake port 32. Normally, the negative pressure of the intake manifold is directly guided to the actuator and used for opening / closing control of the throttle valve.

When a negative pressure in the intake manifold is insufficient, the motor 22 rotates, the diaphragm 23 moves up and down, and the pump chamber A further reduces the negative pressure in the intake chamber C. For example, when the pump chamber A expands, the suction check valve 24 opens to reduce the pressure in the intake chamber C and
When is compressed, the discharge check valve 25 opens and the pressure in the pump chamber A is discharged to the atmosphere.

However, when the diaphragm type vacuum pump of the present embodiment is used for a tote drive system, deceleration is precluded during operation at a predetermined vehicle speed, and then the resume switch is turned on to set the predetermined vehicle speed. When returning to, the flow rate consumed by the actuator may be low and the negative pressure in the intake chamber C may be high. At this time, when the vacuum pump is operated, the check valve 24 does not open unless the pressure in the pump chamber A becomes lower than the pressure in the intake chamber C, so the pump chamber A becomes in a sealed state and the starting torque of the motor 27 is extremely large. Will be things.

However, the pressure in the pump chamber A will not be reduced below the negative pressure set by the relief valve 40.
The characteristics are as shown in the characteristic diagram of the vacuum pump of this embodiment shown by the solid line in the figure.

The relationship between the rotation angle of the motor shaft, that is, the crankshaft of the vacuum pump 20, the torque of the motor, and the pressure in the pump chamber is shown in FIGS. 4 to 6. That is,
When the position of the connecting point between the connecting rod 29 for moving the diaphragm 23 up and down and the motor shaft 37 is represented by its rotation angle θ as shown in FIG. 4, the relief valve is as shown in FIGS. 5 and 6. In the conventional example that does not have 40, the torque T and the pressure P in the pump chamber 51 change as shown by the solid line.
It can be seen that in the first embodiment of the present invention, the peak value of the torque T in FIG. 5 is small and the peak value of the pressure P in FIG. 6 is also small.

In this embodiment, if there is a pressure difference between the atmospheric pressure and the internal pressure of the pump chamber 51, the gas moves through the orifice 31, so that the pressure difference may change the amount of air flowing through the orifice 31. And the driving torque decreases.

As described above, the diaphragm type vacuum pump has a pump chamber A whose volume increases and decreases due to the reciprocating movement of the diaphragm 23.
And a suction check valve 24 for introducing gas into the pump chamber A from the outside in the volume increasing process of the pump chamber A, and a discharge check valve for delivering gas in the pump chamber A to the outside in the volume decreasing process of the pump chamber A. In a diaphragm type vacuum pump comprising a valve 25 and a drive source composed of a motor 22 which is constantly connected to the diaphragm 23 for reciprocally displacing the diaphragm 23, a diaphragm type vacuum pump is provided at a position where the pressure in the pump chamber A and the atmospheric pressure are simultaneously received. It is provided and constantly urged in the valve opening direction by the differential pressure between the negative pressure in the pump chamber A and the atmospheric pressure.
The spring 42 is always biased in the valve closing direction, and when the differential pressure is about to exceed a predetermined value, the atmosphere is introduced into the pump chamber A to maintain the differential pressure at a predetermined value. The relief valve 40 is provided.

Therefore, when the difference between the pressure in the pump chamber A and the atmospheric pressure exceeds a predetermined value, the relief valve 40 is provided to make the pressure in the pump chamber A and the atmospheric pressure communicate with each other. Therefore, it is possible to suppress the negative pressure generated on the side where the consumption flow rate is small, which is supplied to the diaphragm type vacuum pump of the present embodiment set in the relief valve 40. And
A motor serving as a drive source of the diaphragm type vacuum pump of the present embodiment in which the load of the drive source composed of the motor 22 is made uniform.
22 can be miniaturized.

In the first embodiment, the relief valve 40 and the orifice 31 are arranged in the second housing 26, but the valve body 44 constituting the relief valve 40 may be provided with the orifice 31a. FIG. 7 is a cross-sectional view of the essential parts of a second embodiment of the relief valve of that example.

In any case, the relief valve 40 and the orifice 31
Since it suffices to dispose it between the pump chamber A and the atmosphere, the relief valve 40 shown in FIG. 2 or 7 may be formed in the connecting rod 29.

FIG. 8 is a cross-sectional view of an essential part of a third embodiment of the relief valve of the example, in which the valve element 44b is provided in the connecting rod 29b.
Is pressed by the spring 42b, and the pressing force can be set by the set pressure adjusting screw 45. In addition,
The relief intake port 41 is communicated with the inside of the third housing 27 by a through hole 46.

[Effects of the Invention] As described above, the diaphragm type vacuum pump of the present invention controls the pressure in the pump chamber and the pressure in the atmosphere when the difference between the pressure in the pump chamber and the pressure in the atmosphere exceeds a predetermined value. Since it is provided with a relief valve for communication,
It is possible to suppress the negative pressure generated by the vacuum pump set as the relief valve on the side that consumes less flow.
Moreover, since the load of the drive source can be made uniform and the rise of the negative pressure in the pump chamber can be suppressed during the operation of the pump, the drive source of the vacuum pump can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a vacuum pump according to a first embodiment of the present invention, FIG. 2 is a sectional view showing an essential part of a relief valve according to a first embodiment of the present invention, and FIG. Characteristic diagram, Fig. 4 is a diagram showing the rotation angle of the vacuum pump,
FIG. 5 is a characteristic diagram of the vacuum pump showing the rotation angle and torque of the vacuum pump, FIG. 6 is a characteristic diagram of the vacuum pump showing the rotation angle and pressure of the vacuum pump, and FIG.
FIG. 8 is a sectional view showing an essential part of a relief valve of a second embodiment of the present invention, FIG. 8 is a sectional view showing an essential part of a relief valve of a third embodiment of the present invention, and FIG. 9 is a diaphragm type. FIG. 10 is a system diagram of a vacuum pump used in a vacuum type automatic drive system, and FIG. 10 is a pump characteristic diagram of the vacuum pump of the first embodiment of the present invention. In the figure, 23: diaphragm 24: check valve for suction 25: check valve for discharge 26: second housing 27: third housing 28: first housing 29: connecting rod 31, 31a, 31b: orifice 40: relief valve 44 , 44b: valve body A: pump room B: exhaust room C: intake room. In the drawings, the same reference numerals and symbols indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A pump chamber whose volume is increased or decreased by the reciprocating movement of a diaphragm, a suction check valve for introducing gas into the pump chamber from the outside in a volume increase process of the pump chamber, and a pump in a volume decrease process of the pump chamber. In a diaphragm type vacuum pump comprising a discharge check valve for sending out gas in a room to the outside, and a drive source always connected to the diaphragm for reciprocally displacing the diaphragm, the pressure in the pump room and the atmospheric pressure are controlled. The differential pressure between the negative pressure and the atmospheric pressure in the pump chamber is constantly urged in the valve opening direction at the same time, and the spring is always urged in the valve closing direction. When trying to become larger than a predetermined value, atmospheric pressure is introduced into the pump chamber to maintain the differential pressure at a predetermined value. A diaphragm-type vacuum pump comprising a relief valve communicating with the diaphragm type vacuum pump.