Variable displacement vane pump

Abstract

We provide a variable displacement vane pump that allows for a wide range of full cutoff pressure adjustments from low to high pressure using a single pump without changing the spring. [Solution] The vane pump 100 includes a plurality of vanes 122 that slidably protrude from a rotor 120 that is rotatable around an axis 116, a cam ring 124 that is eccentric with respect to the axis and has an inner circumferential surface 128 that the outer peripheral ends 130 of the vanes slide against, a high-pressure spring 150 that biases the cam ring via a plunger, a low-pressure spring 154 that is at least partially inserted into a holder 152 and biases the cam ring via the holder and plunger, a stopper 156 provided on the end of the low-pressure spring opposite to the plunger side, and a pressure adjustment unit 132 that can adjust the position of the stopper from a position where the holder does not come into contact with the stopper even when the cam ring moves to a position where the stopper is in constant contact with the holder.

Description

Technical Field

[0001] The present invention relates to a variable displacement vane pump used as a hydraulic source of hydraulic oil.

Background Art

[0002] As an example, in various machines, a variable displacement vane pump that changes the discharge amount is used as a hydraulic source of hydraulic oil (for example, Patent Document 1). The variable displacement vane pump of Patent Document 1 includes a rotor, a plurality of vanes, and a cam ring, and changes the eccentricity of the cam ring with respect to the rotor according to the load pressure to discharge the discharge amount required for operation.

[0003] In a variable displacement vane pump, in an initial state before the cam ring moves, a holder biased by two springs (low-pressure side spring, high-pressure side spring) having different spring constants abuts against the cam ring. Therefore, a load determined by the combined spring constant of the two springs acts on the cam ring from the holder via the plunger. The cam ring is eccentric and fixed by receiving this load.

[0004] Subsequently, when the pressure in the pump chamber rises and the cam ring moves the distance from the holder to the plunger, the holder abuts against the plunger, so the low-pressure side spring is no longer compressed and stops functioning. Further, when the pressure in the pump chamber rises, thereafter, a load acts on the cam ring according to the spring constant of the high-pressure side spring, and the cam ring moves against this load. When the discharge pressure of the pump reaches an arbitrary set pressure, the movement amount of the cam ring becomes close to the eccentricity amount, the eccentricity amount of the cam ring becomes zero, and a full cut-off state is reached where the discharge flow rate of the pump becomes almost zero.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In the variable displacement vane pump described in Patent Document 1, the distance from the holder to the plunger is kept below the allowable eccentricity of the cam ring. As a result, when setting the initial load using the pressure adjustment unit, the adjustment range of the low-pressure spring becomes narrow, limiting the setting range of the full cutoff pressure to a narrow range. Consequently, in applications where the full cutoff pressure is used over a wide range from low to high pressure, it is necessary to change the spring combination for each setting range.

[0007] Furthermore, in the case of a vane pump with an integrated motor, it is necessary to prepare motors with different outputs for each set pressure range of the pump. In particular, if the motor uses a permanent magnet (such as an IPM motor), the motor rotor will be attracted to the stator by magnetic force when the pump section is separated. For this reason, reassembly is difficult without special equipment, and it is difficult to replace only the motor, so a predetermined number of motors must be prepared (managed) in stock for each set pressure range.

[0008] In view of these problems, the present invention aims to provide a variable displacement vane pump that can adjust the full cutoff pressure over a wide range from low to high pressure using a single pump without changing the spring. [Means for solving the problem]

[0009] To solve the above problems, the variable displacement vane pump of the embodiment comprises a rotor rotatable around an axis, a plurality of vanes slidably protruding from the rotating rotor, and a cam ring having an inner surface that slides against the outer peripheral ends of the vanes protruding from the rotor and which is eccentric with respect to the axis, and further comprises a plunger, a high-pressure spring that biases the cam ring via the plunger, a holder, a low-pressure spring that at least a portion of which is inserted into the holder and biases the cam ring via the holder and plunger, a stopper provided on the end of the low-pressure spring opposite to the plunger side, and a pressure adjustment unit that displaces the stopper, wherein the pressure adjustment unit can adjust the position of the stopper from a position where the holder does not contact the stopper to a position where the stopper is always in contact with the holder, even if the cam ring moves.

[0010] The pressure adjustment section described above should ideally allow the stopper's position to be adjusted to two positions: one where the holder is never in contact with the stopper, and another where the holder contacts the stopper as the eccentricity of the cam ring decreases from its maximum to zero. [Effects of the Invention]

[0011] According to the above configuration, a variable displacement vane pump can be provided that allows for a wide range of adjustment from low to high pressure to the full cutoff pressure using a single pump without changing the spring. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of a variable displacement vane pump according to an embodiment. [Figure 2] Figure 1 is a cross-sectional view of the vane pump at XX. [Figure 3] This figure shows the vane pump in a full-flow state with the stopper in contact with the holder. [Figure 4] This graph shows the control characteristics of a vane pump. [Modes for carrying out the invention]

[0013] This embodiment will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in this embodiment are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustration.

[0014] Figure 1 is a cross-sectional view of a variable displacement vane pump (hereinafter referred to as vane pump 100) in an embodiment. Figure 2 is a cross-sectional view of the vane pump 100 of Figure 1 from XX. The vane pump 100 is a pump that changes the discharge volume and is used as a hydraulic power source for hydraulic fluid in various machines. Here, as the vane pump 100, an electric motor-integrated vane pump integrated with an electric motor 102 shown in Figure 1 is given as an example.

[0015] The electric motor 102 has a motor shaft 104, a motor rotor 106, and a stator 108, which are housed in a motor case 110. When current is applied to the electric motor 102, the motor shaft 104 rotates together with the motor rotor 106 due to the interaction between the motor rotor 106 and the stator 108.

[0016] The motor shaft 104 extends into the body 112 of the vane pump 100 and is connected to the rotating shaft 116, which is the pump shaft of the vane pump 100, via a joint 114. The gap between the motor shaft 104 and the body 112 is sealed by an oil seal 118. As shown in Figure 1, the motor case 110 of the electric motor 102 and the body 112 of the vane pump 100 are connected to form a single unit.

[0017] As shown in Fig. 2, the vane pump 100 includes a pump rotor (hereinafter referred to as rotor 120), a plurality of vanes 122, and a cam ring 124. The rotor 120 is integrally supported with the rotating shaft 116 and is rotatable about the rotating shaft 116. The vanes 122 project slidably from the rotating rotor 120 through vane grooves 126 provided in the rotor 120 shown in Fig. 2.

[0018] The cam ring 124 is a cylindrical member that can be eccentric with respect to the rotating shaft 116. Here, the allowable amount of eccentricity (eccentricity) of the cam ring 124 is denoted as e (see Fig. 2). The outer peripheral end portions 130 of the vanes 122 protruding from the rotor 120 are in sliding contact with the inner peripheral surface 128 of the cam ring 124.

[0019] On one side of the cam ring 124 (the left side in Fig. 2), a pressure adjusting portion 132 for adjusting the discharge pressure of the vane pump 100 is provided, and on the other side (the right side in Fig. 2), a discharge amount adjusting portion 134 is provided. An opening is provided on the side of the body 112 opposite to the side (the right side in Fig. 2) that houses the cam ring 124. The opening of the body 112 is closed by an adapter 136. A hole for receiving a fixing member for fixing the adapter 136 to the body 112 is drilled in one end surface of the body 112 outside this opening. Further, a pair of through holes are provided in the adapter 136 at positions facing the hole in one end surface of the body 112. The fixing member passes through these through holes, and the tip side thereof is held in the hole of the body 112, whereby the adapter 136 is fixed to the body 112. In the adapter 136, a further through hole is provided between the pair of through holes for fixing to the body 112. A pressure adjusting screw 138 of the pressure adjusting portion 132 is screwed into this through hole. The pressure adjusting screw 138 is passed through the through hole of the adapter 136 and, by advancing and retreating, its tip portion is displaced with respect to the body 112. The discharge amount adjusting portion 134 is provided in the body 112 and has a discharge amount adjusting screw 142 that presses the outer peripheral surface 140 of the cam ring 124.

[0020] Furthermore, the body 112 is provided with a ring position adjusting portion 144 (upper side in FIG. 2). The ring position adjusting portion 144 has a ring position adjusting screw 146 that presses the outer peripheral surface 140 of the cam ring 124, and adjusts the position of the cam ring 124 by displacing the ring position adjusting screw 146 in the axial direction. Note that the ring position adjusting screw 146 of the ring position adjusting portion 144 is substantially orthogonal to the pressure adjusting screw 138 of the pressure adjusting portion 132 and the discharge amount adjusting screw 142 of the discharge flow rate adjusting portion 134.

[0021] Furthermore, the vane pump 100 includes a plunger 148, a high-pressure side spring 150, a holder 152, a low-pressure side spring 154, and a stopper 156. The plunger 148 is a member that abuts against the cam ring 124, and has a contact surface 148a and a flange portion 148b. The contact surface 148a of the plunger 148 abuts against the outer peripheral surface 140 of the cam ring 124. One end 150a of the high-pressure side spring 150 abuts against the flange portion 148b.

[0022] The holder 152 is a bottomed hollow cylinder, is inserted into the high-pressure side spring 150, and the low-pressure side spring 154 is inserted therein. The holder 152 has a bottom portion 152a and a flange portion 152b. One end 154a of the low-pressure side spring 154 abuts against the bottom portion 152a of the holder 152. The other end 150b of the high-pressure side spring 150 abuts against the flange portion 152b. Thereby, the holder 152 biases the high-pressure side spring 150 toward the cam ring 124 side. Furthermore, the high-pressure side spring 150 biases the plunger 148 toward the cam ring 124 side. Note that the holder 152 may be configured to have an engaging portion where one end 154a of the low-pressure side spring 154 is engaged instead of the bottom portion 152a. In that case, the holder 152 has a bottomless cylindrical shape with a flange portion on the pressure adjusting portion 132 side.

[0023] The stopper 156 has a contact surface 156a and a pressing surface 156b. The contact surface 156a of the stopper 156 has a recess that is recessed toward the pressure adjustment section 132 side, where the portion of the low-pressure spring 154 facing the other end 154b is recessed, and the other end 154b contacts and is accommodated in this recess (first recess). The opposite side of the stopper 156a is the pressing surface 156b. The pressing surface 156b has a recess that is recessed toward the plunger 148 side, and the end of the pressure adjustment screw 138 contacts or is accommodated in this recess (second recess). In accordance with the movement of the pressure adjustment screw 138, the stopper 156 displaces the other end 154b of the low-pressure spring 154 toward the cam ring 124. Furthermore, the low-pressure spring 154 biases the holder 152 toward the cam ring 124 side. Furthermore, the configuration is not limited to housing and holding the low-pressure spring 154 in a recess; for example, the spring end may be engaged by an engaging portion (not shown).

[0024] Furthermore, the pressure adjustment unit 132 adjusts the position of the stopper 156 (displaces the stopper 156) by tightening the pressure adjustment screw 138 and displacing it in the axial direction, thereby pressing the pressing surface 156b of the stopper 156 toward the cam ring 124.Here, the amount of tightening of the pressure adjustment screw 138 is denoted as α, and the distance between the contact surface 156a of the stopper 156 and the flange portion 152b of the holder 152 (hereinafter, the distance between the stopper 156 and the holder 152) is denoted as St.The amount of tightening α can be rephrased as the length of the gap between the stopper 156 and the opening end face of the body 112.In other words, the amount of tightening α is the length of the screw's movement in the gap on the pressing surface 156b side of the stopper 156, and in the example of Figures 2 and 3, it can also be said to be the length between the pressing surface 156b and its opposing surface (adapter 136).

[0025] In the vane pump 100 shown in Figure 2, the tightening amount α of the pressure adjustment screw 138 is sufficiently small, so the distance St between the stopper 156 and the holder 152 is large (St>0), and the stopper 156 does not contact the holder 152. However, the distance St is not determined solely by the tightening amount α, but can also change depending on the pump capacity. This distance St will be discussed later with reference to Figures 3 and 4.

[0026] When the stopper 156 is not in contact with the holder 152, the low-pressure spring 154 inserted into the holder 152 functions to bias the holder 152 toward the cam ring 124. As a result, a load determined by the combined spring constant of the high-pressure spring 150 and the low-pressure spring 154, which have different spring constants, acts on the cam ring 124 from the holder 152 via the plunger 148.

[0027] Here, if we let K1 be the spring constant of the low-pressure spring 154, K2 be the spring constant of the high-pressure spring 150, and K be the combined spring constant, then the combined spring constant is determined by "1 / K = 1 / K1 + 1 / K2". In other words, when the stopper 156 does not contact the holder 152, the cam ring 124 is subjected to a load determined by a spring constant smaller than K2 and becomes eccentric.

[0028] Furthermore, in the vane pump 100, when the tightening amount α of the pressure adjustment screw 138 is sufficiently small, the distance St between the contact surface 156a of the stopper 156 and the flange portion 152b of the holder 152 is greater than the eccentricity allowance e of the cam ring 124, as shown in Figure 2 (St>e). In other words, the pressure adjustment unit 132 can adjust the position of the stopper 156 to a position where the holder 152 does not come into contact with the stopper 156 even when the cam ring 124 moves with St>e (a position where St>0). "When the cam ring 124 moves with St>e" means that even when the cam ring 124 moves and the eccentricity becomes zero, resulting in a full cutoff state (described later) where the discharge flow rate (discharge amount) of the vane pump 100 is almost zero, the stopper 156 does not come into contact with the holder 152. The position of the stopper 156 may also be considered as the contact position between the stopper 156 and the low-pressure spring 154.

[0029] The body 112 of the vane pump 100 is provided with a drain port 158 ​​that connects to a drain tank (not shown) at atmospheric pressure. The drain port 158 ​​communicates with a spring chamber 160 that houses a high-pressure spring 150 and a low-pressure spring 154. The drain port 158 ​​draws in or discharges hydraulic fluid from the outside in response to volume fluctuations in the spring chamber 160, which is filled with hydraulic fluid.

[0030] In the vane pump 100 shown in Figure 2, the cam ring 124 is in the full-flow state (maximum pump capacity) where it is most eccentric with respect to the rotor 120 (or rotation axis 116) and in contact with the discharge volume adjustment screw 142 of the discharge volume adjustment unit 134. When the discharge volume adjustment unit 134 is displaced in the axial direction, the gap between the rotor 120 and the cam ring 124 is adjusted. In other words, the maximum eccentricity of the cam ring 124 in the full-flow state is adjusted by the discharge volume adjustment screw 142. This adjusts the maximum discharge amount of hydraulic fluid flowing from the suction port 164 to the discharge port 166 provided in the cover 162 shown in Figure 1. The cover 162 is integrally formed with the body 112 of the vane pump 100.

[0031] The operation of the vane pump 100 will now be explained. In the full-flow state shown in Figure 2, when the rotor 120 rotates counterclockwise, the volume of the pump chamber 168 expands in the lower suction region, and hydraulic fluid is drawn into the pump chamber 168 from the suction port 164 shown in Figure 1. Furthermore, in the vane pump 100, pressurized hydraulic fluid is discharged from the pump chamber 168 to the discharge port 166 in the upper discharge region, where the volume of the pump chamber 168 contracts.

[0032] The amount of hydraulic fluid discharged from the vane pump 100 during operation is determined by the eccentricity of the cam ring 124 relative to the rotor 120. When the hydraulic fluid pressure rises in the discharge region of the pump chamber 168 and exceeds the load acting on the cam ring 124 via the plunger 148 (the load determined by the combined spring constant K of the high-pressure spring 150 and the low-pressure spring 154), the cam ring 124 moves in a direction that reduces the eccentricity (in the direction that pushes the plunger 148 back).

[0033] When the eccentricity of the cam ring 124 becomes zero, the size of the pump chamber 168 does not change even when the rotor 120 rotates, so the vane pump 100 enters a full cutoff state in which almost no hydraulic fluid is discharged. The pressure at which the full cutoff state occurs is called the full cutoff pressure.

[0034] Figure 3 shows the state in which the stopper 156 is in contact with the holder 152 when the vane pump 100 is in full flow condition. In the vane pump 100, tightening the pressure adjustment screw 138 of the pressure adjustment unit 132 increases the tightening amount α, causing the contact surface 156a of the stopper 156 and the flange portion 152b of the holder 152 to come into contact (St=0).

[0035] As a result, the low-pressure spring 154 inserted into the holder 152 is no longer compressed and ceases to function. When the low-pressure spring 154 is not functioning, the cam ring 124 is eccentric under a load determined by the large spring constant K2 of the high-pressure spring 150.

[0036] Figure 4 is a graph showing the control characteristics of the vane pump 100. In the figure, the horizontal axis of the graph is pressure (MPa), and the vertical axis is pump capacity (cm³). 3 The values ​​shown are / rev. Note that the pressure at which the pump capacity is almost zero (full cutoff state) is the full cutoff pressure. Therefore, the range shown as Pa-Pb on the horizontal axis of the graph represents the pressure adjustment range for the full cutoff pressure.

[0037] In the diagram, the black dots indicate the timing at which the stopper 156 contacts the holder 152. α1 is the tightening amount at which the pressure adjustment screw 138 is loosened to its lowest position, and the stopper 156 almost contacts the adapter 136. α2 is the tightening amount at which the pressure adjustment screw 138 is tightened, and the stopper 156 contacts the holder 152 at full cutoff. α6 is the tightening amount at which the stopper 156 contacts the holder 152 from full flow. α3 to α5, which are between α2 and α6, are examples of tightening amounts at which the stopper 156 contacts the holder 152 during the transition from full flow to full cutoff. α7 is a tightening amount even more than α6.

[0038] The range R1 of the set pressure (full cutoff pressure) corresponding to the tightening amounts α1 to α2 represents the control characteristics of the vane pump 100 shown in Figure 2. As described above, the vane pump 100 shown in Figure 2 is adjusted so that even if the cam ring 124 moves as St>e, the holder 152 does not come into contact with the stopper 156 (the position where St>0). For this reason, the low-pressure spring 154 continues to function until the cam ring 124 moves and the eccentricity becomes zero, resulting in a full cutoff state.

[0039] As a result, the cam ring 124 is subjected to a load determined by a small spring constant, which is the combined spring constant K of the high-pressure spring 150 and the low-pressure spring 154, i.e., "1 / K = 1 / K1 + 1 / K2". Therefore, the vane pump 100 can set the full cutoff pressure to a low pressure, as shown in range R1, if the low-pressure spring 154 continues to function. The vane pump 100 also moves from the full-flow state to the full-cutoff state with a slope determined by the combined spring constant K as shown in range R1.

[0040] The range of set pressures R2 corresponding to tightening amounts α2 to α6 represents the control characteristics of the vane pump 100 when the tightening amount α of the pressure adjustment screw 138 is greater than the tightening amount of the vane pump 100 shown in Figure 2, and less than the tightening amount of the vane pump 100 shown in Figure 3.

[0041] In this case, the pressure adjusting unit 132 can adjust the position of the stopper 156 to a position where the stopper 156 contacts the holder 152 (St = 0) while the cam ring 124 moves to the full cut-off state within the allowable eccentricity e of the cam ring 124 (St < e).

[0042] Thus, the cam ring 124 is eccentric under the load determined by the combined spring constant K (small spring constant) of the high-pressure side spring 150 and the low-pressure side spring 154 until the position where the stopper 156 does not contact the holder 152 (St > 0). When the stopper 156 contacts the holder 152 (St = 0), the low-pressure side spring 154 is no longer compressed and stops functioning.

[0043] When the low-pressure side spring 154 stops functioning, the cam ring 124 is eccentric under the load determined by the large spring constant K2 of the high-pressure side spring 1,50. Therefore, when the low-pressure side spring 154 stops functioning during the transition to the full cut-off state, the vane pump 100 can set the full cut-off pressure higher than that in the range R1 as shown in the range R2.

[0044] Also, the slope from the full flow state to the black dot is the same as the slope of the control characteristic corresponding to α1, and further, from the black dot to the full cut-off state, it is the same as the slope of the control characteristic corresponding to α6.

[0045] Here, the vane pump 100 shown in FIG. 3 corresponds to the tightening amount α6 and is adjusted to the position where the stopper 156 contacts the holder 152 (St = 0). However, the pressure adjusting unit 132 can also adjust the position of the stopper 156 to a position "above" the position where the stopper 156 always contacts the holder 152 (St = 0) (that is, a position closer to the cam ring 124 than the position where the stopper 156 contacts the holder 152).

[0046] The range of set pressure R3 corresponding to tightening amounts α6 to α7 represents the control characteristics of the vane pump 100 when the position of the stopper 156 is adjusted to a position where the stopper 156 is constantly in contact with the holder 152. In such a vane pump 100, the low-pressure side spring 154 is non-functional from the start, and the cam ring 124 is eccentric only by the load determined by the large spring constant K2 of the high-pressure side spring 150.

[0047] In this way, in the vane pump 100, by adjusting the position of the stopper 156 so that the low-pressure spring 154 does not function from the full-flow state to the full-cutoff state, the full-cutoff pressure can be set to an even higher pressure compared to range R2, as shown in range R3. Furthermore, range R3 goes from the full-flow state to the full-cutoff state with only the slope determined by the spring constant K2 described above.

[0048] Therefore, with the vane pump 100, the full cutoff pressure can be adjusted over a wide range from low to high pressure, as shown in the pressure adjustment range Pa-Pb in Figure 4, without changing the spring with a single pump.

[0049] Furthermore, since the vane pump 100 has an integrated motor, there is no need to secure a separate motor for each pump pressure range. This reduces the number of types of vane pumps with integrated motors, i.e., the number of types corresponding to different pump levels (set pressures), simplifying inventory management and further reducing costs.

[0050] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Explanation of Symbols]

[0051] 100...Vane pump, 102...Electric motor, 104...Motor shaft, 106...Motor rotor, 108...Stator, 110...Motor case, 112...Vane pump body, 114...Joint, 116...Rotating shaft, 118...Oil seal, 120...Rotor, 122...Vane, 124...Cam ring, 126...Vane groove, 128...Inner surface of cam ring, 130...Outer end of vane, 132...Pressure adjustment section, 134...Discharge volume adjustment section, 136...Adapter, 138...Pressure adjustment screw, 140...Outer surface of cam ring, 142...Discharge volume adjustment screw, 144...Ring position adjustment section, 146...Ring position adjustment Screw, 148…Plunger, 148a…Contact surface of plunger, 148b…Flange of plunger, 150…High pressure spring, 150a…One end of high pressure spring, 150b…Other end of high pressure spring, 152…Holder, 152a…Bottom of holder, 152b…Flange of holder, 154…Low pressure spring, 154a…One end of low pressure spring, 154b…Other end of low pressure spring, 156…Stopper, 156a…Contact surface of stopper, 156b…Pressing surface of stopper, 158…Drain port, 160…Spring chamber, 162…Cover, 164…Intake port, 166…Discharge port, 168…Pump chamber

Claims

1. A rotor that can rotate around its axis, Multiple vanes slidably protruding from the rotating rotor, A variable displacement vane pump comprising a cam ring having an inner circumferential surface with which the outer peripheral ends of the vanes protruding from the rotor slide, and which is eccentric with respect to the shaft, Plunger and, A high-pressure spring that biases the cam ring via the plunger, Holder and, A low-pressure spring, at least a portion of which is inserted into the holder and biases the cam ring via the holder and the plunger, A stopper is provided on the end of the low-pressure spring opposite to the plunger side, It has a pressure adjustment unit that displaces the stopper, The pressure adjustment unit maintains the position of the stopper even when the cam ring moves. From a position where the holder does not come into contact with the stopper, The stopper is adjustable to a position greater than or equal to the position in which it is constantly in contact with the holder. A variable displacement vane pump characterized by the following features.

2. The pressure adjustment unit adjusts the position of the stopper, A position in which the holder does not always come into contact with the stopper, The variable displacement vane pump according to claim 1, characterized in that the holder can be adjusted to a position where it contacts the stopper, while the eccentricity of the cam ring is moving from its maximum to zero.

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