JP2012184657A - Vane pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of cavitation when a flow-rate control valve starts to open.SOLUTION: The vane pump has the flow-rate control valve 102 for controlling flow rates of working fluids supplied to a hydraulic apparatus from a pump chamber. The flow-rate control valve 102 comprises: a first pressure chamber 23 and a second pressure chamber 24 which are defined at both ends of a spool 20, and to which the throttle upstream and downstream working fluids are introduced, respectively; a bypass port 27 which is formed at the internal periphery of a spool accommodation hole 10a, and introduces the working fluid to a bypass passage 40 from the first pressure chamber 23 accompanied by the movement of the spool 20 accompanied by an increase of throttle fore-and-aft differential pressure; and an opposing port 29 which is formed at the internal periphery of the spool accommodation hole 10a while opposing the bypass port 27. The bypass port 27 is formed into a shape different from that of the opposing port 29 so that the first pressure chamber 23 and the bypass passage 40 are made to communicate with each other at the full close of the opposing port 29.

Description

  The present invention relates to a vane pump, and more particularly, to a vane pump including a flow control valve that controls a flow rate of a working fluid supplied to a hydraulic device.

  As a conventional vane pump, one having a flow rate control valve for controlling the flow rate of hydraulic oil supplied to a hydraulic device is known (for example, see Patent Document 1).

JP-A-9-170569

  In a vane pump provided with a flow control valve, the hydraulic oil that recirculates to the suction passage through the flow control valve has a function of increasing the suction pressure of the vane pump and improving the suction performance. However, since the pump suction pressure is low when the flow control valve starts to open, the vane pump may cause cavitation due to insufficient suction. Cavitation causes vibration and noise.

  The present invention has been made in view of the above problems, and an object thereof is to prevent the occurrence of cavitation when a flow control valve starts to open.

  The present invention is a vane pump including a flow rate control valve that controls a flow rate of a working fluid supplied from the pump chamber to a hydraulic device by returning a part of the working fluid discharged from the pump chamber to a pump suction side through a bypass passage. The flow control valve includes a spool that moves according to a differential pressure across the throttle that provides resistance to the flow of the working fluid discharged from the pump chamber, and a spool housing in which the spool is slidably inserted. A hole, a first pressure chamber and a second pressure chamber that are defined at both ends of the spool, to which the working fluid upstream and downstream of the throttle, respectively, are formed on an inner periphery of the spool receiving hole; A bypass port that guides the working fluid from the first pressure chamber to the bypass passage as the spool moves as the front-rear differential pressure increases, and a bar on the inner periphery of the spool receiving hole. An opposing port formed facing the passport, and an operation formed on the outer periphery of the spool and flowing from the first pressure chamber into the opposing port as the spool moves as the differential pressure across the throttle increases. An annular groove for guiding fluid to the bypass passage, and the bypass port is formed differently from the opposing port so as to communicate the first pressure chamber and the bypass passage when the opposing port is fully closed. It is characterized by that.

  According to the present invention, when the flow control valve starts to open, the first pressure chamber and the bypass passage communicate with each other only through the bypass port, so that the flow rate of the hydraulic oil returning to the pump suction side is increased and the vane pump is removed from the tank. Since the suction performance for sucking the working fluid is improved, the occurrence of cavitation is prevented.

It is sectional drawing of the vane pump which concerns on embodiment of this invention. It is sectional drawing which follows the AA line of FIG. It is a top view of the pump cartridge in the vane pump concerning an embodiment of the invention. 1 is a hydraulic circuit diagram of a vane pump according to an embodiment of the present invention. It is a graph which shows the flow volume characteristic of a vane pump.

  Hereinafter, a vane pump 100 according to an embodiment of the present invention will be described with reference to the drawings.

  The vane pump 100 is used as a hydraulic pressure supply source for hydraulic equipment mounted on a vehicle, for example, a continuously variable transmission or a power steering device.

  As shown in FIG. 1, the vane pump 100 includes a pump cartridge 101 that discharges hydraulic oil (working fluid), and a flow rate that controls the flow rate of hydraulic oil discharged from the pump cartridge 101 and supplied to hydraulic equipment (not shown). And a control valve 102.

  As shown in FIG. 3, the pump cartridge 101 is such that the power of an engine (not shown) as a power source is transmitted to the end of the drive shaft 1 and the rotor 2 connected to the drive shaft 1 rotates. .

  The pump cartridge 101 accommodates the plurality of vanes 3 that can be reciprocated in the radial direction with respect to the rotor 2, and accommodates the rotor 2, and the tip of the vane 3 on the inner cam surface 4 a as the rotor 2 rotates. And a cam ring 4 that slides.

  In the rotor 2, slits 16 having openings on the outer peripheral surface are radially formed at predetermined intervals, and the vanes 3 are slidably inserted into the slits 16.

  A back pressure chamber 17 into which pump discharge pressure is guided is defined on the proximal end side of the slit 16. Adjacent back pressure chambers 17 communicate with each other by an arc-shaped groove 2a formed in the rotor 2, and pump discharge pressure is always guided to the groove 2a. The vane 3 is pressed in the direction of popping out of the slit 16 by the pressure of the back pressure chamber 17, and the tip part abuts on the cam surface 4 a on the inner periphery of the cam ring 4. Thus, a plurality of pump chambers 7 are defined inside the cam ring 4 by the outer peripheral surface of the rotor 2, the cam surface 4 a of the cam ring, and the adjacent vanes 3.

  The cam ring 4 is an annular member having an inner circumferential cam surface 4 a that is substantially elliptical, and has a suction region that expands the volume of the pump chamber 7 and a discharge region that contracts the volume of the pump chamber 7. In the present embodiment, the cam ring 4 has two suction areas and two discharge areas.

  A pump cover (not shown) is disposed in contact with one side of the rotor 2 and the cam ring 4, and a side plate 6 is disposed in contact with the other side. In this way, the pump cover and the side plate 6 are arranged with both side surfaces of the rotor 2 and the cam ring 4 being sandwiched, and seal the pump chamber 7.

  On the surface of the pump cover where the rotor 2 slides, two arc-shaped suction ports (not shown) that open to correspond to the suction region of the cam ring 4 and guide the hydraulic oil to the pump chamber 7 are formed in a groove shape. Is done.

  The side plate 6 is formed with two arc-shaped discharge ports 9 that open corresponding to the discharge region of the cam ring 4 and guide the hydraulic oil discharged from the pump chamber 7 to the discharge passage 14 through the high-pressure chamber. .

  Each pump chamber 7 sucks the hydraulic oil through the suction port in the suction region of the cam ring 4 as the rotor 2 rotates, and discharges the hydraulic oil through the discharge port 9 in the discharge region of the cam ring 4. Thus, each pump chamber 7 supplies and discharges hydraulic oil by expansion and contraction accompanying the rotation of the rotor 2.

  Next, the flow control valve 102 will be described with reference to FIGS.

  The flow control valve 102 has a spool 20 that moves in accordance with the differential pressure across the throttle 21 (see FIG. 4) that provides resistance to the flow of hydraulic oil discharged from the pump chamber 7, and is discharged from the pump chamber 7. The flow rate of the hydraulic oil supplied from the pump chamber 7 to the hydraulic equipment is controlled by returning a part of the hydraulic oil from the spool 20 to the pump suction side through the bypass passage 40. The throttle 21 is interposed in the discharge passage 14.

  The spool 20 is slidably inserted into a spool accommodation hole 10 a formed in the pump body 10. A cap 50 is screwed into the opening of the spool accommodation hole 10a.

  A first pressure chamber 23 and a second pressure chamber 24 into which hydraulic oil upstream and downstream of the throttle 21 are respectively guided are defined at both ends of the spool 20. As described above, the hydraulic oil discharged from the pump chamber 7 is directly guided to the first pressure chamber 23, whereas the hydraulic oil decompressed by the throttle 21 is guided to the second pressure chamber 24. A spring 25 that urges the spool 20 in a direction to expand the volume of the second pressure chamber 24 is accommodated in the second pressure chamber 24. Therefore, the spool 20 balances at a position where the load based on the differential pressure across the throttle 21 and the biasing force of the spring 25 are balanced.

  At the inner periphery of the spool housing hole 10a, there is a discharge port 26 (see FIG. 4) for guiding the hydraulic oil in the discharge passage 14 upstream of the throttle 21 to the first pressure chamber 23, and the hydraulic oil from the first pressure chamber 23 to the bypass passage 40. And a back pressure port 28 (see FIG. 4) for guiding the hydraulic oil in the discharge passage 14 downstream of the throttle 21 to the second pressure chamber 24 through the pressure guide passage 43.

  The bypass port 27 is closed by the land portion 20a of the spool 20 when the pressure difference across the throttle 21 is small and the spring 25 is extended, and the spool 20 is attached to the spring 25 as the pressure difference across the throttle 21 increases. It opens as it moves against the forces.

  As shown in FIG. 2, on the inner periphery of the spool accommodating hole 10a, a counter port recessed in a concave shape at a position facing the bypass port 27, that is, a position symmetrical to the bypass port 27 with the axis of the spool accommodating hole 10a as the center. 29 is formed. Further, on the outer periphery of the spool 20, an annular ring groove 20 b that guides hydraulic oil flowing from the first pressure chamber 23 to the opposing port 29 to the bypass port 27 is formed.

  When the opposed port 29 does not exist in the spool accommodation hole 10a, the spool 20 is pressed against the inner periphery of the spool accommodation hole 10a due to the pressure difference between the first pressure chamber 23 and the bypass passage 40, and the slidability of the spool 20 is increased. Damaged. However, by providing the opposing port 29 in the spool accommodation hole 10a, the pressure balance acting on the spool 20 is improved, and the slidability of the spool 20 with respect to the spool accommodation hole 10a is improved.

  Next, the operation of the flow control valve 102 will be described with reference to FIG. The flow rate Q indicated by the solid line in FIG. 5 is the flow rate of the hydraulic oil supplied to the hydraulic equipment, that is, the flow rate indicated by the flow meter 45 shown in FIG. The region surrounded by the solid line flow rate Q and the dotted line flow rate Q ′ is the recirculation flow rate that recirculates to the pump suction side through the flow rate control valve 102. Further, the pump suction pressure P shown in FIG. 5 is the pressure indicated by the pressure gauge 44 shown in FIG.

  When the pump rotational speed is low and the flow rate of the hydraulic oil discharged from the pump chamber 7 is small (region less than the pump rotational speed N shown in FIG. 5), the pressure loss at the throttle 21 is small. And the pressure difference between the second pressure chamber 24 is small. Therefore, the spool 20 is urged by the urging force of the spring 25, and the bypass port 27 is closed at the land portion 20 a of the spool 20. As a result, the hydraulic oil discharged from the pump chamber 7 is supplied to the hydraulic equipment in its entirety. For this reason, hydraulic oil proportional to the number of revolutions of the pump is supplied to the hydraulic equipment.

  If the pump rotation speed increases and the flow rate of the hydraulic oil discharged from the pump chamber 7 increases (region where the pump rotation speed N is greater than or equal to that shown in FIG. 5), the pressure loss at the throttle 21 increases, so the first pressure chamber The pressure difference between the second pressure chamber 24 and the second pressure chamber 24 increases. Therefore, the spool 20 moves while compressing the spring 25, and accordingly, the first pressure chamber 23 communicates with the bypass port 27 and also communicates with the opposing port 29. As a result, part of the hydraulic oil in the first pressure chamber 23 flows directly into the bypass passage 40 through the bypass port 27, and flows into the opposing port 29 so as to bypass the land portion 20a, and from the annular groove 20b to the bypass port 27. Through the bypass passage 40. Thus, the hydraulic oil in the first pressure chamber 23 flows into the bypass passage 40 through two paths. The hydraulic oil that has flowed into the bypass passage 40 returns to the suction passage 41 that connects the tank 42 and the pump cartridge 101, and is again sucked into the pump chamber 7 through the suction port. Thus, part of the hydraulic oil discharged from the pump chamber 7 returns to the suction passage 41 through the bypass port 27.

  As the flow rate of hydraulic oil discharged from the pump chamber 7 increases, the pressure loss at the throttle 21 increases, so that the amount of movement of the spool 20 increases and the opening area of the bypass port 27 increases. Therefore, as shown in FIG. 5, the flow rate of the working oil that recirculates to the suction passage 41 increases as the flow rate of the working oil discharged from the pump chamber 7 increases. After the first pressure chamber communicates with the bypass port 27, the flow rate of the hydraulic oil supplied to the hydraulic equipment is kept moderate.

  As described above, when the pump speed is less than N, the flow rate of hydraulic oil discharged from the pump chamber 7 (hereinafter referred to as “pump discharge flow rate”) is equal to the flow rate of hydraulic oil supplied to the hydraulic equipment, and the pump rotation Above a few N, a flow rate obtained by subtracting the reflux flow rate from the pump discharge flow rate is supplied to the hydraulic equipment.

  When the recirculation flow rate returning to the suction passage 41 increases, the flow rate of the hydraulic oil increases and the inlet pressure of the pump chamber 7 increases, so that the hydraulic oil returning to the suction passage 41 acts to push the hydraulic oil into the pump chamber 7. To do. That is, the hydraulic oil that recirculates to the suction passage 41 has a function of increasing the suction pressure of the pump cartridge 101 and improving the suction performance. Therefore, as shown in FIG. 5, the pump suction pressure P in the pump chamber 7 decreases as the pump rotation speed increases when there is no recirculation flow rate (less than the pump rotation speed N). Then, when a part of the pump discharge flow rate starts to recirculate (pump rotation speed N or more), it generally starts increasing and increases as the recirculation flow rate increases.

  Here, when the pressure difference between the first pressure chamber 23 and the second pressure chamber 24 becomes large and the spool 20 moves while compressing the spring 25, when the bypass port 27 and the opposed port 29 start to open simultaneously, Since the hydraulic oil flows into the bypass passage 40 from both the bypass port 27 and the opposed port 29, the flow rate through each port is small and the flow rate is not fast. In particular, the hydraulic fluid flowing into the counter port 29 has a low flow rate when passing through the annular groove 20b, and therefore contributes to improving the suction performance of the pump cartridge 101. As described above, when the bypass port 27 and the opposed port 29 start to open at the same time, the effect of improving the suction performance of the hydraulic oil flowing back from the bypass passage 40 to the suction passage 41 is small.

  As a countermeasure against this, the shape of the bypass port 27, which conventionally has the same shape and dimensions as the opposed port 29, is formed in a shape different from the opposed port 29. This will be specifically described below.

  The facing port 29 is formed as a circular hole in the inner periphery of the spool accommodation hole 10a. On the other hand, as shown in FIG. 1, the bypass port 27 includes a circular hole 27a having the same shape and the same size as the opposed port 29, and a protruding hole 27b protruding from the circular hole 27a.

  The circular hole 27a and the circular hole of the facing port 29 are formed in the same process by drilling. Therefore, the circular hole 27a and the circular hole of the counter port 29 are formed in the same shape and the same size and symmetrically about the axis of the spool accommodation hole 10a.

  The protruding hole 27 b extends in the axial direction of the spool 20 and is formed to protrude toward the distal end direction of the spool 20. The protruding hole 27b is formed by cutting after forming the circular hole 27a and the circular hole of the opposed port 29 by drilling.

  By forming the bypass port 27 in this way, when the spool 20 moves while compressing the spring 25, the bypass port 27 starts to open through the protruding hole 27b before the opposing port 29 starts to open (see FIGS. 2 and 2). The state shown in FIG. As described above, the bypass port 27 is formed differently from the counter port 29 so as to communicate the first pressure chamber 23 and the bypass passage 40 when the counter port 29 is fully closed.

  When only the bypass port 27 starts to open when the spool 20 moves while compressing the spring 25, the hydraulic oil in the first pressure chamber 23 flows into the bypass passage 40 only through the protruding hole 27b of the bypass port 27 (FIG. 2). Therefore, the flow rate of the hydraulic oil flowing through the bypass port 27 is increased, and the pressure in the bypass passage 40 is decreased. As a result, the suction performance of the pump cartridge 101 for sucking hydraulic oil from the tank 42 is improved, and the pump suction pressure in the pump chamber 7 is increased, thereby preventing the occurrence of cavitation.

  The shape of the protruding hole 27b is not limited to the arc shape as shown in FIG. 1, and may be a triangular shape or a quadrangular shape.

  According to the above embodiment, the following operational effects are obtained.

  When the flow control valve 102 starts to open, the first pressure chamber 23 and the bypass passage 40 communicate with each other only through the bypass port 27, so that the flow rate of the hydraulic oil that returns to the pump suction side is increased, and the pressure in the bypass passage 40 is increased. descend. As a result, the suction performance of the pump cartridge 101 for sucking hydraulic oil from the tank 42 is improved, so that the occurrence of cavitation is prevented.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The vane pump according to the present invention can be applied to a hydraulic pressure supply source such as a transmission for a vehicle or a power steering device.

100 Vane Pump 101 Pump Cartridge 102 Flow Control Valve 1 Drive Shaft 2 Rotor 7 Pump Chamber 10a Spool Housing Hole 14 Discharge Passage 20 Spool 20a Land 20b Annular Groove 21 Restriction 23 First Pressure Chamber 24 Second Pressure Chamber 25 Spring 27 Bypass Port 27a Circular hole 27b Protruding hole 29 Opposed port 40 Bypass passage 41 Suction passage

Claims (2)

A vane pump comprising a flow rate control valve for controlling the flow rate of the working fluid supplied from the pump chamber to the hydraulic equipment by returning a part of the working fluid discharged from the pump chamber to the pump suction side through a bypass passage,
The flow control valve is
A spool that moves in accordance with a differential pressure across the throttle that provides resistance to the flow of the working fluid discharged from the pump chamber;
A spool receiving hole into which the spool is slidably inserted;
A first pressure chamber and a second pressure chamber which are defined at both ends of the spool and into which working fluids upstream and downstream of the throttle are respectively guided;
A bypass port formed on the inner periphery of the spool housing hole, for guiding the working fluid from the first pressure chamber to the bypass passage as the spool moves with an increase in the differential pressure across the throttle;
An opposing port formed on the inner periphery of the spool housing hole so as to oppose the bypass port;
An annular groove formed on the outer periphery of the spool for guiding the working fluid flowing from the first pressure chamber to the opposing port as the spool moves as the differential pressure across the throttle increases, to the bypass passage; Prepared,
The vane pump, wherein the bypass port is formed differently from the counter port so as to communicate the first pressure chamber and the bypass passage when the counter port is fully closed. The opposing port is formed as a circular hole;
The bypass port is composed of a circular hole having the same shape and size as the opposed port, and a protruding hole protruding from the outer periphery of the circular hole,
2. The vane pump according to claim 1, wherein the bypass port communicates the first pressure chamber and the bypass passage when the opposed port is fully closed.