Patent Application
20150098847
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-207982 filed on Oct. 3, 2013, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vacuum pump for generating negative pressure to be used in a brake booster of a vehicle such as a car.
2. Related Art
An automotive braking device is provided with a brake booster for amplifying braking force by utilizing negative pressure in an intake pipe of an engine. In recent years, pumping loss has been reduced in response to a demand for good mileage. This results in a tendency for intake-pipe negative pressure to be smaller. In a hybrid vehicle, an electric vehicle, or a vehicle with an idling stop function, the intake-pipe negative pressure of an engine may not be obtained.
Therefore, the negative pressure to be supplied to a brake booster would be generated by use of an electric vacuum pump. Even in a vehicle mounted with a diesel engine that generates no intake-pipe negative pressure, the negative pressure is generated by use of an electric vacuum pump.
As one example of such a vacuum pump, a vacuum pump in Patent Document 1 for example includes a motor part provided with a commutator, a brush, and an armature, a pump part to be operated in sync with the motor part, and a bearing placed between the motor part and the pump part. In this vacuum pump in Patent Document 1, the commutator and the brush of the motor part are placed in positions closer to the pump part than the armature.
However, the vacuum pump in Patent Document 1 may generate motor foreign matter such as abrasion powder from the commutator and the brush due to sliding between the commutator and the brush during operation of the pump. The thus generated motor foreign matter is sucked toward the pump part by the negative pressure generated in the pump part and may flow in or enter the bearing placed between the motor part and the pump part. This increases sliding resistance in the bearing. Furthermore, when the motor foreign matter adheres to the bearing, the motor part is locked and stopped. Thus, the vacuum pump in Patent Document 1 may not operate stably.
The present invention has been made to solve the above problems and has a purpose to provide an electric vacuum pump that can operate stably.
To achieve the above purpose, one aspect of the invention provides an electric vacuum pump including: a rotary member including an armature and a commutator; a brush arranged to slide in contact with the commutator; a motor part provided with a rotary shaft integral with the rotary member; a pump part connected to the rotary shaft and configured to operate in sync with the motor part; and a bearing supporting the rotary shaft between the motor part and the pump part, the commutator and the brush being placed on a non-pump side opposite to a pump side on which the pump part is placed in an axial direction of the rotary shaft with respect to the armature.
According to the above aspect, the commutator and the brush are placed away from the bearing located between the motor part and the pump part. Accordingly, motor foreign matter such as abrasion powder possibly generated from the commutator and the brush due to sliding of the commutator against the brush are less likely to flow in the bearing. Furthermore, the armature which is a rotor is placed between the bearing and a set of the commutator and the brush. Thus, the motor foreign matter is much less likely to enter the bearing. Consequently, the performance of the bearing can be maintained, thereby enabling stable operation of the electric vacuum pump.
A detailed description of an embodiment of an electric vacuum pump embodying the present invention will now be given referring to the accompanying drawings. In the present embodiment explained below, the electric vacuum pump of the invention is applied to a brake system.
The brake system will be first explained referring to
A brake system 1 of this embodiment includes, as shown in
The brake booster 12 is provided between the brake pedal 10 and the master cylinder 14 as shown in
The brake booster 12 is internally partitioned by a diaphragm (not illustrated) into a negative pressure chamber (not shown) close to the master cylinder 14 and a transformer chamber (not shown) allowing introduction of atmospheric air. The negative pressure chamber of the brake booster 12 is connected to an intake pipe 32 of an engine through a first passage L1. That is, the first passage L1 is connected to the negative pressure chamber of the brake booster 12 and the intake pipe 32. Accordingly, the negative pressure chamber of the brake booster 12 is supplied with negative pressure generated in the intake pipe 32 through the first passage L1 according to an opening degree of a throttle valve 34 during driving of the engine.
The master cylinder 14 increases hydraulic pressure of a brake main body (not shown) by operation of the brake booster 12, thereby generating a braking force in the brake main body. The negative pressure sensor 16 detects the negative pressure in the negative pressure chamber of the brake booster 12.
The electric vacuum pump 18 is connected to a second passage L2 as shown in
The electric vacuum pump 18 is further connected to the ECU 24 through a relay 36 as shown in
The first check valve 20 is provided in the first passage L1 at a position between a branch point to the second passage L2 and the brake booster 12. The second check valve 22 is provided in the first passage L1 at a position closer to the intake pipe 32 than the first check valve 20 and between the branch point to the second passage L2 and the intake pipe 32. These first check valve 20 and second check valve 22 are each configured to open only when negative pressure on the side of the intake pipe 32 is higher than the negative pressure on the side of the negative pressure chamber of the brake booster 12 and to permit a fluid to flow only from the negative pressure chamber of the brake booster 12 to the intake pipe 32. In this manner, the brake system 1 can encapsulate negative pressure in the negative pressure chamber of the brake booster 12 by the first check valve 20 and the second check valve 22.
The ECU 24 consists of for example a microcomputer and includes a ROM that stores control programs, a rewritable RAM that stores calculation results and others, a timer, a counter, an input interface, and an output interface. To this ECU 24, as shown in
Next, the electric vacuum pump 18 will be explained.
Firstly, Example 1 is explained.
The electric vacuum pump 18 has a cylindrical shape and is provided with the suction port 151 and the discharge port 152 at an upper end as shown in
The motor part 110 includes an electric motor 112, a commutator 113, a metal motor case 114, a brush 115, a shaft 116, and others. The electric motor 112 is housed in the motor case 114 and includes an armature (a rotor) 112a and a magnet (a stator) 112b. The magnet 112b is fixed to the motor case 114. The armature 112a is rotatably placed inside the magnet 112b with a clearance therefrom. The armature 112a and the commutator 113 are one example of a “rotary member” of the present invention.
The shaft 116 is integrally attached to the armature 112a and the commutator 113. This shaft 116 is one example of a “rotary shaft” of the present invention.
In the motor part 110, the electric motor 112 is driven by an external power supply, thereby causing the shaft 116 to rotate. The shaft 116 is rotatably supported by the bearing 130 fixed to the motor case 114.
The commutator 113 is attached to the shaft 116. The brush 115 is placed outside the outer peripheral surface of the commutator 113. The brush 115 is configured to relatively slide in contact with the commutator 113 to transmit electric current.
In the present embodiment, as shown in
The pump part 120 is constituted of a vane-type vacuum pump and is placed above the motor part 110. The pump part 120 is activated in sync with the motor part 110. Herein, the vane-type vacuum pump is configured such that a rotor having a circular columnar shape placed in an eccentric state in a pump chamber is formed with grooves, in which a plurality of vanes are inserted to be movable in a rotor radial direction. When the rotor rotates, the vanes are caused to protrude from the grooves by centrifugal force and slide in contact with the inner peripheral surface of a pump chamber, thereby maintaining hermetical sealing between adjacent pump spaces of the pump chamber. In association therewith, the volume of each closed pump space partitioned by the vanes is increased or decreased, thereby causing suction, compression, and discharge of air, so that negative pressure is generated in the pump chamber.
To be concrete, the pump part 120 is provided with a housing 121 having an inner peripheral surface of a nearly cylindrical shape. The inner peripheral surface of a nearly cylindrical shape represents that the cross section of the housing 121 is defined in a circular shape surrounded by a curved line without being limited to a perfect circular or elliptic shape. Both ends of the housing 121 are closed by circular cover members 122a and 122b, so that a pump chamber 123 is formed by the inner peripheral surface of the housing 121 and the cover members 122a and 122b. The housing 121 is fixed to the case 140.
In the pump chamber 123, a circular columnar rotor 124 is housed to be rotatable about the axis eccentric to the center axis of the pump chamber 123. This rotor 124 is coupled to the shaft 116 of the electric motor 112. Accordingly, the rotor 124 is rotated in sync with rotary driving of the electric motor 112 via the shaft 116.
The rotor 124 has a plurality of vane grooves in each of which, a vane 125 formed in a flat plate shape is slidably engaged to be movable in and out. An end of each vane 125 slides in contact with the inner peripheral surface of the housing 121 by centrifugal force imparted to the vanes 125 during rotation of the rotor 124. Upper and lower end faces of the vanes 125 are in contact with the cover members 122a and 122b respectively. Thus, the vanes 125 partition the pump chamber 123 into a plurality of pump spaces.
The pump chamber 123 communicates with the outside through a suction inlet 126 and a discharge outlet 127. The suction inlet 126 is provided in the cover member 122a to communicate with the pump chamber 123. The suction inlet 126 is a part to suck air from pump outside to pump inside. The discharge outlet 127 is also provided in the cover member 122a to communicate with the pump chamber 123. Exhaust air ejected from the discharge outlet 127 is discharged to the pump outside through the discharge port 152.
The bearing 130 is placed between the motor part 110 and the pump part 120. This bearing 130 supports the shaft 116 in a rotatable state.
The upper cover 150 is a resin member closing an upper open end of the case 140 that houses the motor part 110 and the pump part 120. Specifically, the upper cover 150 closes the case 140 from the pump part side.
The upper cover 150 is provided with the suction port 151 to suck air in the pump part 120 from the pump outside, a silencer part 153 including a space or cavity communicating with the discharge outlet 127 of the pump part 120, and the discharge port 152 to discharge exhaust air discharged or ejected from the pump part 120 to the pump outside.
The silencer part 153 is formed by the internal space of the upper cover 150. Thus, exhaust air discharged or ejected from the discharge outlet 127 of the pump part 120 passes through the silencer part 153 and then is discharged to the pump outside through the discharge port 152.
The lower cover 160 is a resin member closing a lower open end of the case 140 that houses the motor part 110 and the pump part 120. The lower cover 160 closes the case 140 from the motor part side.
In the electric vacuum pump 18 configured as above, when the electric motor 112 is driven to rotate by power externally supplied, the rotor 124 is rotated in synchronization therewith. Then, the vanes 125 slide along the vane grooves by centrifugal force, causing the end faces of the vanes 125 to contact with the inner peripheral surface of the housing 121. While keeping such a contact state, the vanes 125 are rotated along the inner peripheral surface of the housing 121. This rotation of the rotor 124 causes the volume of each pump space of the pump chamber 123 to expand or contract, thereby sucking air into the pump chamber 123 through the suction inlet 126 and ejecting air from the pump chamber 123 through the discharge outlet 127. This operation generates negative pressure in the pump chamber 123.
Specifically, in the brake system 1, when the relay 36 is turned on based on a drive start signal from the ECU 24, the electric vacuum pump 18 starts operating, thereby supplying negative pressure to the negative pressure chamber of the brake booster 12 through the suction port 151, the second passage L2 and the first passage L1. Furthermore, when the relay 36 is turned off based on a drive stop signal from the ECU 24, the electric vacuum pump 18 stops operating, thereby stopping supplying negative pressure to the negative pressure chamber of the brake booster 12 through the suction port 151, the second passage L2 and the first passage L1.
In the brake system 1, while the engine is running and negative pressure is generated in the intake pipe, the negative pressure in the intake pipe 32 is supplied to the negative pressure chamber of the brake booster 12 through the first passage L1. Thus, the negative pressure in the negative pressure chamber of the brake booster 12 can be regulated. In contrast, when the engine is stopped or when the ECU 24 determines that the negative pressure is insufficient, the ECU 24 turns on the relay, thereby driving the electric vacuum pump 18 to supply the negative pressure to the negative pressure chamber of the brake booster 12 through the second passage L2 and the first passage L1. Thus, the negative pressure in the negative pressure chamber of the brake booster 12 can be regulated.
The electric vacuum pump 18 of the present example explained in detail above includes the motor part 110 provided with the rotary member consisting of the armature 112a and the commutator 113, the brush 115 slidable together with the commutator 113, and the shaft 116 integral with the rotary member, the pump part 120 connected to the shaft 116 and configured to operate in sync with the motor part 110, and the bearing 130 supporting the shaft 116 between the motor part 110 and the pump part 120. The commutator 113 and the brush 115 are placed on the non-pump side opposite in the axial direction of the shaft 116 from the pump side on which the pump part 120 is placed with respect to the armature 112a.
The commutator 113 and the brush 115 are placed away from the bearing 130 located between the motor part 110 and the pump part 120. Accordingly, foreign matter such as abrasion powder (hereinafter, referred to as “motor foreign matter”) from the commutator 113 and the brush 115, which may be generated due to sliding between the commutator 113 and the brush 115, are less likely to enter the bearing. Furthermore, the armature 112a which is a rotor is placed between the bearing 130 and a set of the commutator 113 and the brush 115. This generates passage resistance, thereby making the motor foreign matter much less likely to enter the bearing 130. Consequently, the performance of the bearing 130 can be maintained and hence the electric vacuum pump 18 can operate stably.
Next, Example 2 will be explained, in which similar or identical parts to those in Example 1 are assigned the same reference signs to those in Example 1 and their details are not explained. The following explanation is thus made with a focus on differences from Example 1.
As shown in
The commutator 113 thus includes inclined grooves 172 formed in the inclined direction with respect to the axial direction of the shaft 116 and arranged one each between adjacent ones of the segments 170 on the outer peripheral surface. An end 172a of each inclined groove 172 on the non-pump side is located at a more forward position in an opposite direction to a rotational direction (a direction indicated by a solid arrow in
In this Example, when the commutator 113 is rotated during operation of the electric vacuum pump 18, a flow of air is generated in a direction (a direction indicated by broken lines in
Next, Example 3 will be explained, in which similar or identical parts to those in Examples 1 and 2 are assigned the same reference signs to those in Examples 1 and 2 and their details are not explained. The following explanation is thus made with a focus on differences from Examples 1 and 2.
As shown in
As a variation, the armature 112a may be provided, on its outer peripheral surface, with inclined grooves 176 in the inclined direction to the axial direction of the shaft 116 (the vertical direction in
In the present example, when the armature 112a is rotated during operation of the electric vacuum pump 18, a flow of air is generated from the pump side toward the non-pump side in the motor part 110. This causes the motor foreign matter to flow from the pump side toward the non-pump side in the motor part 110. Thus, the motor foreign matter is much less likely to enter the bearing 130.
Next, Example 4 will be explained, in which similar or identical parts to those in Examples 1 to 3 are assigned the same reference signs to those in Examples 1 to 3 and their details are not explained. The following explanation is thus made with a focus on differences from Examples 1 to 3.
As shown in
As a variation, as shown in
The foreign-matter wall 180a and the foreign-matter wall 180b are one example of a “non-pump-side wall member” in the present invention.
In this example, the foreign-matter wall 180a or the foreign-matter wall 180b blocks the motor foreign matter from flowing toward the pump side through gaps between the armature 112a and the magnet 112b. The motor foreign matter is therefore much less likely to enter the bearing 130.
The foreign-matter wall 180a and the foreign-matter wall 180b are each formed in the resin molded part 180 covering the end face 178 of the armature 112a on the non-pump side. This resin molded part 180 can prevent the motor foreign matter from entering the bearing 130 while ensuring insulation in the armature 112a.
Next, Example 5 will be explained, in which similar or identical parts to those in Examples 1 to 4 are assigned the same reference signs those in Examples 1 to 4 and their details are not explained. The following explanation is thus made with a focus on differences from Examples 1 to 4. Herein,
As shown in
The cover member 122a of the pump part 120 includes a foreign matter discharge hole 128. This hole 128 communicates with inside and outside of the pump part 120.
In this example, the negative pressure generated in the pump part 120 allows the motor foreign matter to pass through the through hole 113a of the commutator 113, the abrasion powder passage 116a, the rotor 124, and the foreign matter discharge hole 128 as indicated by solid arrows in
Next, Example 6 will be explained, in which similar or identical parts to those in Examples 1 to 5 are assigned the same reference signs to those in Examples 1 to 5 and their details are not explained. The following explanation is thus made with a focus on differences from Examples 1 to 5.
As shown in
Of a plurality of thin plate-like core members stacked constituting the core 186, the upper core member 186a is a core member located at a position closest to the bearing 130 (an upper side in
Of the plurality of thin plate-like core members stacked constituting the core 186, the lower core member 186b is a core member located at a position closest to the commutator 113 (a lower side in
In the present example, the wall part 188 of the upper core member 186a and the wall part 190 of the lower core member 186b block the motor foreign matter from flowing toward the pump side. Thus, the motor foreign matter is much less likely to enter the bearing 130.
The above embodiment is a mere example and does not particularly limit the invention. Thus, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For instance, Examples 1 to 6 may be combined in various combinations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-207982 | Oct 2013 | JP | national |
