Pumps – Expansible chamber type – Multiple cyclic outlet paths
Reexamination Certificate
1999-07-29
2001-05-15
Walberg, Teresa (Department: 3742)
Pumps
Expansible chamber type
Multiple cyclic outlet paths
C137S624110, C137S627500
Reexamination Certificate
active
06231321
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an air compressor for use in a vehicle, for example. More particularly, the present invention relates to an air compressor suitably used to supply and discharge compressed air for vehicle height adjustment with respect to an air-suspension system or the like that constitutes a vehicle-height adjusting apparatus.
In general, an air-suspension system mounted on a vehicle as a vehicle-height adjusting apparatus is selectively supplied with or exhausted of compressed air from an air compressor to suppress changes in the vehicle height that may occur according to the vehicle weight or the like and to allow vehicle height adjustment to be made as the driver likes.
A vehicle-mounted air compressor used for an air-suspension system or the like has a cylinder and a piston reciprocally provided in the cylinder to compress air in the cylinder. The air compressor further has a cylinder head mounted on the cylinder. The cylinder head is provided with an air supply passage for supplying compressed air generated by the piston to a pneumatic apparatus such as an air-suspension system. In addition, an exhaust valve is provided in the cylinder head to discharge compressed air from the air supply passage to an exterior of the cylinder head [for example, see Japanese Patent Application Unexamined Publication (KOKAI) No. 2-141321 (1990)].
In this type of conventional air compressor, when compressed air is to be supplied to an air-suspension system, for example, the piston is caused to reciprocate in the cylinder with the exhaust valve closed in advance, thereby generating compressed air and supplying it to the air-suspension system through the air supply passage. In the air-suspension system, an air chamber is expanded by the compressed air supplied thereto, and thus vehicle height adjustment is made so as to raise the vehicle height.
During vehicle height adjustment for lowering the vehicle, the exhaust valve is opened, with the piston reciprocating motion in the cylinder stopped, to allow the air supply passage to communicate with the exterior of the cylinder head, thereby making compressed air flow backward from the air chamber of the air-suspension system into the air supply passage. Thus, the compressed air is discharged to the exterior of the cylinder head to contract the air chamber.
In the conventional air compressor, the cylinder head is provided with a single exhaust passage for allowing the air supply passage to communicate with the outside air, and a solenoid-operated exhaust valve that constitutes the exhaust valve is placed at an intermediate position in the exhaust passage. The solenoid-operated exhaust valve is a normally closed valve. Accordingly, the solenoid-operated exhaust valve opens the exhaust passage only when it is opened by externally supplying an electric current thereto, and permits compressed air to be discharged from the air supply passage to the exterior of the cylinder head.
Incidentally, the above-described conventional air compressor is merely arranged such that a single exhaust passage is provided in the cylinder head and the exhaust passage is selectively opened or closed by the solenoid-operated exhaust valve. Therefore, when compressed air in the air-suspension system is discharged to the exterior of the cylinder head to adjust the vehicle height to a lower level, the flow rate of compressed air to be discharged is undesirably limited by the single exhaust passage. Consequently, the compressed air discharge speed is unfavorably low. Therefore, it is difficult to perform vehicle height adjustment in a short period of time.
It is possible to take measures to increase the compressed air discharge speed, for example, by increasing the port diameter of the solenoid-operated exhaust valve. However, if the port diameter of the solenoid-operated exhaust valve is increased, the pressure-receiving area of the valving element with respect to the exhaust port becomes large. Therefore, it becomes necessary to increase the urging force of a valve spring for urging the valving element of the solenoid-operated exhaust valve in a valve closing direction and also necessary to increase the size of a solenoid (coil) for driving the valving element in a valve opening direction against the valve spring. Consequently, not only the solenoid-operated exhaust valve but also the cylinder head must be increased in size.
SUMMARY OF THE INVENTION
In view of the above-described problems associated with the prior art, an object of the present invention is to provide an air compressor designed so that the compressed air discharge speed can be increased without increasing the size of a passage member, e.g. a cylinder head, and therefore, vehicle height adjustment, for example, can be made in a reduced period of time, and further the whole air compressor can be formed in a compact structure.
The present invention is applied to an air compressor having a drive source and a compressed air generating mechanism driven by the drive source to generate compressed air. A passage member is connected to the compressed air generating mechanism. The passage member is provided with an air supply passage for supplying the compressed air to a pneumatic apparatus. In addition, an exhaust device is provided in the passage member to discharge compressed air from the pneumatic apparatus to the exterior of the cylinder head,
According to the present invention, the exhaust device includes first and second exhaust passages provided in the passage member and connected to the air supply passage in parallel to each other. A pilot-operated switching valve is provided in the first exhaust passage and supplied with compressed air from the air supply passage as a pilot pressure, thereby selectively bringing the first exhaust passage into or out of communication with the exterior of the cylinder head. In addition, a solenoid-operated exhaust valve is provided in the second exhaust passage to selectively bring the second exhaust passage into or out of communication with the exterior of the cylinder head and also to control the pilot pressure supplied to the pilot-operated switching valve in response to external supply of an electric current.
With the above-described arrangement, when the solenoid-operated exhaust valve is closed by stopping the external supply of an electric current, for example, the second exhaust passage is cut off from the outside or atmospheric air (i.e. the air that is exterior of the passage member), and compressed air from the air supply passage is supplied to the switching valve acting in a valve closing direction. Thus, the first exhaust passage can be kept cut off from the outside air by the pilot-operated switching valve.
When the solenoid-operated exhaust valve is opened by externally supplying an electric current thereto, the second exhaust passage is allowed to communicate with the outside air. In addition, the pilot-operated switching valve is supplied with a pilot pressure acting in a valve opening direction. By opening the switching valve with the pilot pressure, the first exhaust passage is allowed to communicate with the outside air.
According to a specific example of the present invention, the pilot-operated switching valve includes a valving element slide hole formed as a stepped hole that is provided in the passage member at an intermediate position in the first exhaust passage. The valving element slide hole has a small-diameter hole portion, a large-diameter hole portion, and an annular step portion formed between the small-diameter hole portion and the large-diameter hole portion. A stepped valving element is fitted in the valving element slide hole. The stepped valving element defines an annular pressure-receiving chamber between the stepped valving element and the annular step portion. An urging device is provided between the stepped valving element and the passage member to urge the stepped valving element in a direction in which the pressure-receiving chamber contracts, thereby holding the stepped valving el
Fukudome Hiroshi
Kobayashi Kan
Mizutani Yoichi
Tokico Ltd.
Van Quang
Walberg Teresa
Wenderoth , Lind & Ponack, L.L.P.
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