| Tandem pump no-load operation device -> Monitor Keywords |
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Tandem pump no-load operation deviceTandem pump no-load operation device description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080107545, Tandem pump no-load operation device. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001]The present invention relates to a tandem pump which comprises two fluid pumps that are driven simultaneously by a single drive source, and in which the pressurized oil output from both fluid pumps is merged and supplied to the fluid supply destination. In more detail, the present invention relates to a tandem pump no-load operation device in which when the fluid supply flow rate increases and the pressure within the fluid supply channel reaches the no-load operation start pressure, one of the fluid pumps is operated under no-load to reduce the power from the drive source. BACKGROUND ART [0002]A tandem pump includes two fluid pumps that are driven simultaneously by a single drive source, and the pressurized oil output from the respective outlets of the two fluid pumps can be at the same or different pressures. Two separate actuators can be connected to the two outlets of this type of tandem pump and the actuators can be separately operated, but by merging the pressurized oil output from the two pumps and supplying a fluid supply destination, it is possible to obtain a flow rate corresponding to two fluid pumps. An example of the use of the latter tandem pump is an oil pump provided in an automobile engine, for example, that supplies oil (engine oil) to an oil gallery provided in the engine block to lubricate and cool each part of the engine. This is configured so that the drive shaft of the tandem pump is driven by a gear installed on the engine crankshaft. When the engine rotation speed is low, and the flow rate of the oil output from both pumps is small, the oil output from both oil pumps is merged in the oil supply channel, and when the engine rotation speed is large and the flow rate of the oil output from both oil pumps is large, the oil output from one of the two oil pumps is drained and the oil pump is operated under no load, and the oil output from the other oil pump only is supplied to the oil supply channel. In this type of configuration, when the rotation speed of the engine is low, sufficient supply flow rate of lubricating oil can be ensured, so when the vehicle is traveling at low speed it is possible to provide sufficient lubrication to each part of the engine. This type of tandem pump is disclosed in for example Japanese Patent Application Laid-open No. H10-131751 and Japanese Patent Application Laid-open No. 2001-132624. [0003]FIG. 7 shows an example of a conventional tandem pump no-load operation device. In FIG. 7, a main oil pump P1 and a secondary oil pump P2 are driven simultaneously by a single drive source (an engine M). A main oil supply channel L1 is connected to an oil supply destination (for example, an oil gallery provided within the engine block) OB from the outlet of the main oil pump P1 via a line filter that is not shown in the drawings. Also, a secondary oil supply channel L2 that extends from the outlet of the secondary oil pump P2 is connected to the middle portion of the main oil supply channel L1. A check valve CV is installed in the secondary oil supply channel L2 to prevent the inflow of hydraulic oil from the main oil supply channel L1 towards the secondary oil pump P2 side, and an unload valve AV is installed on the secondary oil supply channel L2 between the check valve CV and the secondary oil pump P2. [0004]Here, when the rotation speed of the engine is low, and the pressure within the main oil supply channel L1 is low, the unload valve AV is closed, and the oil output from the secondary oil pump P2 passes through the check valve CV and flows into the main oil supply channel L1, so the oil output from both main and secondary oil pumps P1, P2 is merged and transmitted to the oil supply destination OB from the main oil supply channel L1. On the other hand, when the rotation speed of the engine is high, the flow rate of oil output from both oil pumps increases, and when the pressure within the main oil supply channel L1 is equal to or greater than the no-load operation start pressure, the pressurized oil within the main oil supply channel L1 presses a spool in the unload valve AV which opens the unload valve AV, so the hydraulic oil within the secondary oil supply channel L2 is released to the drain side, and the secondary oil pump P2 enters the no-load operation state. At this time, the pressure in the secondary oil supply channel L2 reduces, and the check valve CV closes the secondary oil supply path L2, so only oil output from the main oil pump P1 is supplied to the oil supply destination OB. Also, a relief valve (pressure regulator valve) LV is provided on the main oil supply channel L1, so that the pressure in the main oil supply channel L1 does not rise above the relief setting pressure. DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention [0005]In the conventional tandem valve as described above there was the problem that the check valve CV and the unload valve AV are provided on the secondary oil supply channel L2 and the relief valve (pressure regulator valve) LV is provided on the main oil supply channel L1 as separate valves, so the freedom of layout is limited in circuit design, and it is difficult to make the entire device compact. [0006]With the foregoing problems in view, it is an object of the present invention to provide a tandem pump no-load operation device having the same performance as a conventional device, but which can be made more compact. Means to Solve the Problems [0007]The tandem pump no-load operation device according to the present invention comprises: a tandem pump comprising a main fluid pump (for example, the main oil pump 7 in the embodiments) and a secondary fluid pump (for example, the secondary oil pump 8 in the embodiments) that are driven simultaneously by a drive source; a main fluid supply channel (for example, the main oil supply channel 9 in the embodiments) that extends from an outlet of the main fluid pump to a fluid supply destination (for example, the oil supply destination OB in the embodiments); a secondary fluid supply channel (for example, the secondary oil supply channel 10 in the embodiments) that extends from an outlet of the secondary fluid pump and is connected to the middle of the main fluid supply channel; a valve bore that forms a part of the secondary fluid supply channel; a spool disposed by fitting and insertion within the valve bore so that the spool can freely move, having an internal flow channel that extends in an axial direction; an urging member (for example, the spring 30 in the embodiments) that urges the spool within the valve bore toward connection with the main fluid supply channel; and a poppet disposed within the valve bore so as to be able to move freely, that is closer to the connection with the main fluid supply channel than the spool within the valve bore, and that can move to a position in which an end portion of the poppet contacts and closes an end of the internal flow channel of the spool, and to a position in which the poppet is separated from the end of the internal flow channel to open the internal flow channel. Furthermore, a drain channel is provided that is connected to the valve bore, and when the spool is acted on by the pressure within the main fluid supply channel the spool can move against the force of the urging member; when the pressure within the main fluid supply channel is lower than a no-load operation start pressure, the spool is moved by the force of the urging member towards the connection with the main fluid supply channel, the link with the drain channel is closed, and the secondary fluid supply channel and the main fluid supply channel are linked by the internal flow channel; and furthermore when the pressure within the main fluid supply channel rises higher than the no-load operation start pressure, the spool moves against the force of the urging member, and the secondary fluid supply channel is connected to the drain flow channel, and the poppet is moved into a position to contact and close the end of the internal flow channel of the spool by the difference in pressure between the secondary fluid supply channel and the main fluid supply channel resulting from pressurized oil within the secondary fluid supply channel being drained. [0008]Also, in the above tandem pump no-load operation device, it is desirable that a flow channel serving also as a drain opens to both the main fluid supply channel and the external peripheral surface of the poppet is provided within the poppet, and when the pressure within the main fluid supply channel exceeds the no-load operation start pressure and reaches a relief setting pressure that is still higher, the spool is acted on by the force of the relief setting pressure and is moved to a position where the flow channel serving also as a drain and the drain flow channel are connected, and the pressurized fluid within the main fluid supply channel is drained from the drain flow channel. Advantageous Effects of the Invention [0009]In the tandem pump no-load operation device according to the present invention, when the pressure within the main fluid supply channel is lower than the no-load operation start pressure, the pressurized fluid within the secondary fluid supply channel passes through the internal flow channel of the spool and flows into the main fluid supply channel. At this time the fluid output from the main and secondary fluid pumps is merged and transmitted to the fluid supply destination. When the pressure within the main fluid supply channel rises and reaches the no-load operation start pressure, the spool moves in the direction opposite to the direction of the force of the urging member, the pressurized fluid within the secondary fluid supply channel is drained, the poppet contacts the spool, and the internal flow channel of the spool is closed. At this time, the secondary fluid pump enters the no-load operation state, and oil output from the main fluid pump only is transmitted to the fluid supply destination. In this way, the tandem pump no-load operation device according to the present invention has a configuration in which the necessary components, which are the spool, the urging member, and the poppet, are provided within a single valve bore, while maintaining the same function as the conventional art, namely when the pressure in the secondary fluid supply channel rises and reaches the no-load operation start pressure, the secondary fluid pump enters the no-load operation state which reduces the power from the drive source (and furthermore when the pressure within the main fluid supply channel reaches the relief setting pressure, the pressurized oil within the main fluid supply channel is relieved), therefore the degree of freedom during circuit design is increased, and it is possible to make the overall device more compact. BRIEF DESCRIPTION OF THE DRAWINGS [0010]FIG. 1 is a section view showing the configuration of the tandem pump no-load operation device according to an embodiment of the present invention; [0011]FIG. 2 is a partially exploded section view of the no-load operation device; [0012]FIG. 3 is an exploded isometric view of the components within the valve body; [0013]FIG. 4 is a view showing an example of the operation position of the spool and poppet when the oil discharged from both the main and secondary oil pumps merge and is transmitted to the supply destination; [0014]FIG. 5 is a view showing an example of the operation position of the spool and poppet when the secondary oil pump is in the no-load operation state and oil discharged from the main oil pump only is transmitted to the supply destination; [0015]FIG. 6 is a view showing an example of the operation position of the spool and poppet when the outlet pressure in the outlet channel reaches the relief setting pressure and a part of the discharged oil of the main oil pump is drained; and [0016]FIG. 7 is a hydraulic circuit diagram showing an example of the configuration of a conventional tandem pump no-load operation device. 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