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Compressor having a suction throttle valveRelated Patent Categories: Pumps, Successive Stages, Condition Responsive Control Of FluidCompressor having a suction throttle valve description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080107543, Compressor having a suction throttle valve. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates generally to a compressor, and more particularly to a compressor having a suction throttle valve in a suction passage. [0002] A conventional piston type compressor is equipped with a stop for preventing a suction reed valve of the compressor from being vibrated by self-excitation during suction of refrigerant gas. In the piston type variable displacement compressor, however, the amount of suction gas drawn into the compressor differs between the time of maximum displacement and the time of variable displacement. When the stop is set for the maximum displacement, the suction reed valve does not open to a sufficient degree to be in contact with the stop when the displacement is small or when the displacement is minimum. As a result, the suction reed valve generates self-excited vibration to cause suction pulsation, the vibration from which may be propagated to the exterior of the compressor, thereby generating noise. [0003] In order to solve the above problem, there has been proposed a compressor having a suction throttle valve which is adapted to control the opening area of the suction passage, thereby to reduce pressure fluctuation when the flow rate is low. Japanese Patent Application Publications No. 2000-136776 and No. 2005-337232 disclose a variable displacement compressor having an opening control valve serving as the suction throttle valve. The compressor disclosed in Japanese Patent Application Publications No. 2000-136776 has an opening control valve which is operable by a pressure difference due to the flow of refrigerant gas in the suction passage and a spring force to reduce the pressure fluctuation when flow rate is low. [0004] Meanwhile, Japanese Patent Application Publication No. 2005-337232 discloses a variable displacement compressor having an opening control valve. The opening control valve is operable to adjust the opening of the suction passage in accordance with a pressure difference between suction pressure and pressure in the crank chamber. In the compressor, the suction pressure in a suction port acts on the opening control valve as well as the pressure in the crank chamber which varies according to the displacement. Thus, during operation of the compressor at the maximum displacement, influence of the urging force of the spring is lessened and the opening of the suction throttle valve is easily maximized. On the other hand, during the operation at a small displacement, the influence of the urging force of the spring is increased and the opening of the suction throttle valve is easily minimized. [0005] However, in the compressor disclosed in Japanese Patent Application Publication No. 2000-136776, the opening control valve is operable from pressure difference due to the flow of refrigerant gas in the suction passage and the spring force. In this compressor, if the throttling effect by the opening control valve is given priority, the compressor operation at the maximum displacement is influenced by the throttling effect and, therefore, pressure loss is caused in the suction passage, thereby inviting a deterioration in compressing performance. If the compressing performance during the maximum displacement operation is given priority, on the other hand, sufficient throttling effect of the opening control valve is not obtained during operation at a small displacement. [0006] The compressor of Japanese Patent Application Publication No. 2005-337232 can eliminate drawbacks of the compressor of Japanese Patent Application Publication No. 2000-136776. However, when flow rate is relatively high during operation at a variable displacement, the suction passage is subjected to the throttling effect by the opening control valve. In other words, the compressor disclosed in Japanese Patent Application Publication No. 2005-337232 can almost solve the problems of Japanese Patent Application Publications No. 2000-136776. However, despite the intention, there is another problem that a throttling effect by the opening control valve is produced in the suction passage when flow rate is relatively high during operation at a variable displacement. [0007] The opening control valves of Japanese Patent Application Publications No. 2000-136776 and No. 2005-337232 have an urging member in the form of a compression coil spring wherein the relation between load and displacement of the spring is linear. In other words, the compression coil spring has such spring characteristics that the load required when the compression coil spring starts to be displaced is relatively small, and the load is increased in accordance with an increase of displacement of the compression coil spring. In the suction throttle valve using the compression coil spring, if a small load is required when the compression coil spring starts to be displaced, the throttling effect of the suction throttle valve is not obtained sufficiently during operation at a low refrigerant flow rate. The load of the spring is increased with an increase of the spring displacement, so that the throttling effect tends to be produced during operation at a relatively high flow rate. [0008] The present invention, which has been made in view of the above-described problems, is directed to a compressor which ensures that the throttling effect of the suction throttle valve, which does not use crank pressure for its operation, is available during operation of the compressor at a low flow rate and also that the throttling effects of the suction throttle valve is prevented from being developed during operation of the compressor at a high flow rate. SUMMARY OF THE INVENTION [0009] In accordance with an aspect of the present invention, a compressor has a compression chamber formed in a cylinder block, a suction passage formed upstream of the compression chamber and a suction throttle valve formed in the suction passage for adjusting opening of the suction passage. The suction throttle valve has a valve hole and a valve seat formed around the valve hole, a valve body for opening and closing the valve hole and an urging member for urging the valve body in the direction which causes the valve hole to be closed. The urging member is a disk spring. The spring characteristics of the disk spring includes a range where the increasing rate of the load required for displacement of the disk spring is reduced with an increase of displacement of the disk spring. The displacement range of the valve body includes a range where the increasing rate of the load of the disk spring is reduced with an increase of the displacement of the disk spring. [0010] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: [0012] FIG. 1 is a longitudinal cross sectional view of a variable displacement compressor according to the first embodiment; [0013] FIG. 2A shows a graph showing spring characteristics of the disk spring; [0014] FIG. 2B shows a schematic view of a disk spring as an urging member; [0015] FIG. 3A is a partial cross sectional view of a compressor showing a suction throttle valve in its closed state during operation of the compressor at a low flow rate; [0016] FIG. 3B is a partial cross sectional view of a compressor showing a suction throttle valve in its opened state during operation of the compressor at a high flow rate; and [0017] FIG. 4 is a partial cross sectional view of a compressor according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0018] The following will describe a compressor of the first preferred embodiment according to the present invention with reference to FIGS. 1 through 3. The first preferred embodiment is an example as applied to a piston type swash plate variable displacement compressor. [0019] The swash plate variable displacement compressor (hereinafter referred to merely as "compressor") according to the first embodiment will now be described. In FIG. 1, the left side of the compressor on the drawing corresponds to the front side of the compressor, and the right side of the compressor on the drawing correspond to the rear side of the compressor. [0020] As shown in FIG. 1, the compressor has a cylinder block 11. The front end of the cylinder block 11 is connected to a front housing 12 and the rear end of the cylinder block 11 is connected to a rear housing 13 through a valve plate assembly 25. The cylinder block 11 has a compression chamber 33 formed therein. The cylinder block 11 and the front housing 12 cooperate to define therein a space as a crank chamber 14. Continue reading about Compressor having a suction throttle valve... Full patent description for Compressor having a suction throttle valve Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Compressor having a suction throttle valve patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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