JP2770732B2 - Lubrication-free vacuum pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling piston type pump, and more particularly, to a negative pressure source used for a vehicle such as an electric vehicle with a diesel engine, particularly a vacuum pump for generating a negative pressure for a brake booster. .

[0002]

2. Description of the Related Art A rolling piston pump has a small amount of heat generation because it has fewer sliding parts than a rotary vane pump in terms of structure, and is easily driven without lubrication. When lubrication is not performed, there is no lubricant that acts as a seal between the rotor and the casing and between the rotor and both side frames. Therefore, conventionally, as shown in Japanese Patent Application Laid-Open No. 61-164094, a special material is slid. There has been an attempt to maintain a minimum clearance by spraying a material onto a moving surface to remove a material by a clearance amount corresponding to an assembly error, a difference in thermal expansion, and a fine movement amount in an axial direction.

[0003]

However, spraying such a special material complicates the production of components, and the gap varies depending on the spraying condition, and further, the temperature condition and the like. Is set such that the gap becomes zero under the worst conditions, and depending on the temperature state, there may be a case where a gap that affects the pump capacity is generated.

[0004] The inventors of the present invention have made intensive studies and found that by setting the gap around the rotor in the casing to a predetermined value or less, it is possible to smoothly drive the pump without lowering the pumping ability. The present invention has been devised based on such findings of the present inventors, and has a stable performance even without lubrication by forming a gap that does not reduce the performance of the pump. It is an object to provide a lubrication-free vacuum pump.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a casing having a cylindrical inner peripheral surface, and a casing having a predetermined eccentricity with respect to the axis of the casing. A rotor arranged in the casing rolling along a surface, and on both sides of the casing,
A side frame on a flat plate provided with a gap to both end surfaces of the rotor, and inserted into the side frame;
Ball bearing and the ball bearing
An outer peripheral surface of the rotor and the case
The rotor is supported so that a gap is formed with the inner circumferential surface of the rotor.
A shaft lifting, sliding contact with the outer peripheral surface of said rotor, and divide the space between the cylindrical inner peripheral surface of the casing while reciprocating in a radial direction of said rotor and said rotor in the suction chamber and the discharge chamber In the non-lubricated vacuum pump having a blade to be formed, a radial gap when the cylindrical inner peripheral surface of the casing and the rotor outer peripheral surface are closest to each other is up to 40 μm.
m, and technical means that the total value of the gaps at both ends of the rotor is at most 20 μm.

[0006]

According to the above construction, when the rotor rolls in the casing, the radial gap between the inner peripheral surface of the casing and the outer peripheral surface of the rotor is set to a maximum of 40 μm.
m, and the total value of the clearances at both ends of the rotor is up to 20
If it is set to μm, even in such a non-contact state, the pump can be driven properly without affecting the degree of vacuum arrival and evacuation time of the pump within the range. Further, the generation of sliding heat due to no lubrication is avoided by maintaining this gap, and stable performance can be exhibited.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is used as a vacuum pump for a brake booster of a vehicle will be described.
The main body configuration is shown in FIGS. The electric vacuum pump 1 includes a pump unit 10 for discharging and sucking air and a motor unit 20 for driving the pump unit.

The pump portion 10 is provided with a casing 101 having a cylindrical inner peripheral surface 101a formed therethrough. Further, a flat drive frame 103 and a rear frame 104 are formed on both side surfaces of the casing 101 so as to cover the through holes.
It is fastened by a plurality of bolts 112 so as to be in contact with 01b and 101c, respectively.

A ball bearing 114 and a ball bearing 115 are fitted in the drive frame 103 and the rear frame 104, respectively, and a shaft 116 is rotatably supported by the ball bearing 114 and the ball bearing 115. The shaft 116 is provided with a shaft end 116 a that extends through the ball bearing 114 and extends toward the motor unit 20. The shaft end 116 a is fitted and connected to the axis of the motor shaft 210 of the electric motor 200.

At the center of the shaft 116, the shaft 1
A cylindrical eccentric adapter 117 having an axis eccentric by a predetermined amount in the radial direction from the axis of 16 is fixed, and fan-shaped balancers 118, 1 are provided on both sides of the eccentric adapter 117.
Reference numerals 19 are fitted and fixed to the shaft 116, respectively. The ball bearing 1 is provided on the outer periphery of the eccentric adapter 117.
25, the outer ring of which has a cylindrical rotor 1
The inner peripheral surface 102a of No. 02 is fitted and fixed. Therefore, the rotor 102 moves the ball bearing 12 around the shaft 116 about the axis of the eccentric adapter 117.
5 to be rotatably supported. that time,
A radial gap 110, which is a radial gap when the outer peripheral surface 102b of the rotor 102 and the inner peripheral surface 101a of the casing 101 are closest to each other, is formed. Each part is processed and assembled so that the radial gap 110 has a maximum of 40 μm. Specifically, a cylindrical inner peripheral surface 101a of the casing 101 is measured, and a rotor 102 having a maximum gap of 40 μm with respect to the numerical value is set among several rotors created within a certain tolerance. Choose from and combine.

The axial length of the rotor 102 is smaller than the distance between both end surfaces 101b and 101c of the casing 101 by a predetermined amount.
No contact with 04. Therefore, minute gaps and thrust gaps 111a and 111b are formed between the rotor end face and the drive frame 103 and the rear frame 104, respectively. These thrust gaps 111a and 111b
Of the rotor 102 so that the maximum value of
Width dimensions and end surfaces 101b, 101 of the casing 101
The distance dimension between c and the dimensions of the end faces of the drive frame 103 and the rear frame 104 are managed.

The casing 101 is formed with a blade chamber 101d which is open in the axial direction and has parallel grooves. A plate-like blade 107 is inserted into the blade chamber 101d. A spring hole 124 is formed in the upper casing 101 of the blade chamber 101d so as to penetrate to the outside. An opening communicating with the outside of the spring hole 124 is provided with a disk-shaped cap 109 so as to close the opening. Spring hole 124
, A coil-shaped compression spring 108 is inserted, one end of which contacts the cap 109 and the other end of the blade 1
07 is urged. This spring 1
The lower end surface of the blade 107 is always in contact with the outer peripheral surface 102b of the rotor 102 by the urging force of 08. Rotor 10
When the rotor 2 moves eccentrically in the cylinder, the tip of the blade 107
While sliding on 02, the blade chamber 101b reciprocates in the vertical direction in the figure.

The blade 107 divides a cylinder chamber formed by the inner peripheral cylindrical surface 101a of the casing 101, the drive frame 103, the rear frame 104, and the outer peripheral surface 102b of the rotor 102 into a suction chamber 120 and a discharge chamber 121. The casing 101 is provided with a suction port 122 for guiding air to the suction chamber 120. In addition, the blade 107 has an inclined ventilation groove 107a on its side.
The discharge chamber 121 and the blade chamber 1
01d.

Further, the driver frame 103 is provided with a discharge port 103a communicating with the blade chamber 101d. Therefore, the air in the discharge chamber 121 is
7A to the blade chamber 101d.
3a, and is sent to the motor housing 201 side. Next, the structure of the motor unit 20 will be described.

The motor section 20 is provided with a normal electric motor 200 composed of a rotor, a stator, and the like.
It is connected to the shaft 116 on the 0 side in the manner described above. A ball bearing 203 is provided on the outer periphery of the motor shaft 210, and its outer ring is
1, and rotatably supports the motor shaft 210. A ball bearing 207 is similarly provided on the other side of the motor shaft, and its outer ring is supported by the cover 204 and rotatably supports the motor shaft 210.

The housing 201 has an annular insertion portion 201a formed at the center thereof.
03 is inserted into the cylindrical discharge portion 103b,
The cylinder section 10 and the motor section 20 are connected by fastening the drive frame 103 and the housing 201 with bolts 206. A check valve 202 for closing the discharge port is provided at the opening end of the discharge port 103a provided in the drive frame 103 on the housing 201 side, thereby preventing the backflow of air.

A discharge passage 208 communicating with the discharge port 103a.
Communicates with a space between the motor 200 and the cover 204, and the cover 204 is provided with an exhaust port 205 for discharging air discharged into the space. Hereinafter, the operation of the electric vacuum pump 1 will be described.
The motor 200 is driven to rotate by receiving a current supplied from a power supply or the like of the vehicle. Then, the motor shaft 210 rotates about the axis, and the shaft 116 connected to the motor shaft 210 also rotates about the axis. Therefore, the eccentric adapter 117 fixed to the shaft 116 rotates eccentrically by the amount of eccentricity. At this time, since the rotor 102 is rotatably supported by the eccentric adapter via the ball bearing 125,
A rotational swinging motion is performed in the casing 1 in the direction of the arrow in FIG. At this time, the blade 107 abuts on the outer peripheral surface 102a of the rotor 102 by the urging force of the compression spring 108, and the blade chamber 1
Reciprocate within 01d. At this time, the balancers 118 and 11
Reference numerals 9 rotate inside the rotor 102 together with the shaft 116 so as to cancel the imbalance during the rotational swing motion of the rotor 102 without interfering with the inner peripheral surface of the rotor 102 and the ball bearing 125.

By the above-described swinging motion of the rotor 102, the suction chamber 120 and the discharge chamber 121 repeatedly expand and contract to perform a pumping action. That is, the shaft 11
With the rotation of 6, the air in the vacuum tank (not shown) of the brake booster is sucked into the suction chamber 120 through the suction port 122 until the suction chamber 120 becomes maximum. Thereafter, the sucked air is reduced by the reduction of the volume of the discharge chamber 121 so that the ventilation groove 1
07a, the blade chamber 101d, the discharge port 103a, the discharge passage 208, and the discharge port 2 via the motor outer peripheral space 209.
It is led to 05 and discharged outside.

By repeating the suction and discharge steps, the air in the vacuum tank is discharged to the outside, and the vacuum tank is evacuated. At this time, since the electric vacuum pump having the above configuration is lubricated, there is no lubricant that seals both the thrust gaps 111a and 111b of the rotor 102 and the radial gap 110. For this reason, leakage occurs in the two gaps and the performance is deteriorated. Therefore, it is necessary to reduce the dimension of the gap as much as possible. However, the gap size cannot be reduced to zero due to variations in tolerances during component processing and assembly. Therefore, in this embodiment, the maximum value of the radial gap 110 is set to 40 μm,
The total value of a and 111b was set to 20 μm.

In setting the numerical values, experimental results are shown below. FIG. 3 shows experimental data of the thrust gap (total value) and the evacuation time (time to exhaust a 5-liter tank to -600 mmHg) which is one of the evacuation performances of the electric vacuum pump. As shown in the figure, the time tends to greatly increase when the thrust gap (total value) exceeds 20 μm regardless of the radial gap.

FIG. 4 shows experimental data of the radial gap and the ultimate vacuum which is one of the exhaust performances of the vacuum pump. In FIG. 4, the thrust gap (total value) is 20 μm. Radial gap is 40μ from the figure
When m is exceeded, the ultimate vacuum degree is greatly deteriorated. As described above, simply minimizing only the radial gap,
The evacuation time cannot be shortened, and it can be seen that the radial gap does not need to be as narrow as the thrust gap in view of the ultimate vacuum. Therefore, by managing the gap individually in each of the thrust and radial directions, it is only necessary to consider the processing and assembly of the parts so that the minimum required gap that matches the performance of the pump can be taken into consideration. It is possible to realize a good electric vacuum pump.

In the embodiment described above, the upper limit of the thrust gap is set to the two thrust gaps 111a and 111a.
1b was 20 μm or less in total, but the upper limit on one side was 1
The same effect is obtained even when the thickness is 0 μm or less.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a side view showing an entire configuration of an electric vacuum pump according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of the cylinder section in FIG. 1;

FIG. 3 is a characteristic diagram showing a relationship between a thrust gap and an exhaust time.

FIG. 4 is a characteristic diagram showing a relationship between a radial gap and a degree of ultimate vacuum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric vacuum pump 10 Pump part 20 Motor part 101 Casing 102 Rotor 103 Drive frame 104 Rear frame 107 Blade 110 Radial gap 111a, 111b Thrust gap 120 Suction chamber 121 Discharge chamber 200 Motor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-206693 (JP, A) JP-A-63-219892 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F04C 18/356

Claims (1)

(57) [Claims] A casing having a cylindrical inner peripheral surface; a rotor disposed on the casing that rolls along an inner peripheral surface of the casing with a predetermined eccentricity with respect to an axis of the casing; A side frame on a flat plate provided on both side surfaces of the casing with a gap to both end surfaces of the rotor, a ball bearing inserted into the side frame, and a shaft supported by the ball bearing, Before
There is a gap between the outer peripheral surface of the rotor and the inner peripheral surface of the casing.
A shaft supporting the rotor so as to be formed , sliding on the outer peripheral surface of the rotor, and sucking a space between the cylindrical inner peripheral surface of the casing and the rotor while reciprocating in the radial direction of the rotor. chamber and partitioned into a discharge chamber, in unlubricated vacuum pump having a blade forming, the radial gap maximum 40μm when the rotor outer circumference and the cylindrical inner peripheral surface of the casing closest, the rotor The total value of the gaps at both ends of the
A non-lubricated vacuum pump characterized by the following.