WO 2014/198322 Al discloses a typical variable lubricant vane pump for providing pressurized lubricant for an Internal combustion engine. The variable lubricant vane pump is provided with a static pump housing, a shlftable control ring and a rotatable pump rotor comprising several rotor vanes rotating within the shlftable control ring. The control ring is shlftable with respect to the pump rotor to thereby vary the eccentricity of the control ring with respect to the pump rotor for controlling the displacement and, as a result, the volumetric pump performance. The variable lubricant vane pump is provided with a control ring preload spring arranged within a spring chamber, and preloading and pushing the shlftable control ring Into a hlgh-eccentriclty direction. The pump is also provided with a pilot chamber which is loaded with the pump output pressure causing the shlftable control ring to move Into a low-eccentiiclty direction against the control ring preload spring. The pump is provided with a control valve to regulate the hydraulic spring chamber pressure In a range between the pump outlet pressure and atmospheric pressure and, as a result to control the eccentricity of the control ring and thereby the volumetric pump performance.

Since the variable lubricant pump is mechanically driven by the engine, variations of the engine rotational speed cause variations of the volumetric pump performance. These pump performance variations are compensated by a closed-loop control of the eccentricity of the control ring via the control valve. However, the closed-loop control of the control ring eccentricity can cause low-frequency oscillations of the control ring. In particular oscillations with frequencies In the range of 5 Hz to 50 Hz. The control ring oscillations cause fluctuations of the pump outlet pressure and can reduce the pump efficiency. The control ring oscillations can be suppressed by providing the control ring with a damper unit, for example with a hydraulic damper.

DE 100 04 028 A1 discloses a variable vane pump comprising a shlftable control ring which is provided with a preload spring and with a hydraulic damper arranged In the spring chamber. The damper is attached to a static pump housing and supports the preload spring. The damper is In touching contact with the control ring. As a result, the movement of the control ring Into the low-eccentricity direction against the preload spring is damped by the hydraulic damper so that control ring oscillations are reduced. However, the damper does not damp the movement of the control ring Into the opposite hlgh-eccentrlclty direction. Furthermore, the damper can lose the touching contact with the control ring at fast control ring movements so that the damper does not damp In either direction anymore.

It is an object of the Invention to provide a simple variable lubricant vane pump which allows providing a stable pump outlet pressure or engine lubricant gallery pressure, respectively. This object is achieved with a variable lubricant vane pump with the features of claim 1.

The variable lubricant vane pump according to the Invention is provided with a static pump housing defining a pump chamber wherein a shlftable control ring is provided. The control ring can be supported at the pump housing being shlftable strictly linear or can be provided plvotable so that the control ring is moved along an arch-like path. The variable lubricant vane pump according to the Invention is also provided with a rotatable pump rotor located within the control ring. The pump rotor comprises several rotor vanes defining several pump chamber compartments. The rotor vanes and, as a result, the pump chamber compartments rotate within the control ring. The pump rotor axis of rotation is static so that a shifting of the control ring changes the eccentricity of the pump rotor with respect to the surrounding control ring to thereby control the displacement and, as a result, the volumetric performance of the pump. The variable lubricant vane pump according to the Invention is also provided with a control ling preload spring preloading and pushing the shiftable control ring Into a hlgh-eccentricity direction. In the maxlmum- eccentrlclty position, the pump provides the highest displacement and, as a result, the highest volumetric performance for a defined rotational speed. The preload spring is arranged within a hydraulic spring chamber being provided, for example, with atmospheric pressure or with the pump outlet pressure.

The variable lubricant vane pump according to the Invention is also provided with a pilot chamber which is pressurized with the lubricant causing a movement of the control ring against the preload spring Into a low-eccentrlclty direction. The pilot chamber can be pressurized, for example, with the pump outlet pressure or with the engine lubricant gallery pressure.

The variable lubricant vane pump according to the Invention is also provided with a damper unit. One end of the damper unit is attached to the static pump housing and another end of the damper unit is attached to the slldable control ring. The attachment to the pump housing as well as to the control ring allows the damper unit to mechanically damp the control ring movement Into both possible movement directions, the hlgh- eccentricity direction and the low-eccentrlclty direction, so that control ring oscillations can be very efficiently suppressed. As a result, the variable lubricant vane pump according to the Invention allows providing a very stable pump outlet pressure or engine lubricant gallery pressure, respectively.

Preferably, the damper unit comprises a hydraulic damper which uses the pumped lubricant as hydraulic liquid. This allows a simple and reliable arrangement of the damping unit within a hydraulic chamber of the lubricant pump.

In a preferred embodiment of the Invention, the damper unit is arranged within a vane pump hydraulic chamber, for example the spring chamber or the pilot chamber. The damper piston is provided with a damper balance channel fluldlcally connecting the damper displacement chamber and the vane pump hydraulic chamber. The damper balance channel provides a defined lubricant flow rate out of and Into the damper displacement volume. As a result, the damping ratio of the damping unit can be simply controlled via the cross-sectional area of the damper balance channel. The damper balance channel can be, for example, provided as a hole In the damper piston or can be provided simply by the gap between the damper housing and the damper piston. Preferably, the cross section of the damper balance channel is variable and depends on the lubricant temperature. This allows adapting the damper unit to different lubricant temperatures causing different lubricant viscosities. The temperature dependent balance channel cross section can be provided, for example, by using materials with a high thermal expansion coefficient for the damper housing and/or the damper piston. As a result, the width of the gap between the damper housing and the damper piston changes with temperature, wherein the gap defines the damper balance channel. Alternatively, the damper balance channel Inside surface can be coated with a material with a high thermal expansion coefficient.

In a preferred embodiment of the Invention, the damper unit is arranged within the spring chamber and radially supports the control ring preload spring. Preferably, the damper unit is provided with a cylindrical shape so that the control ring preload spring can be simply slipped over the damper unit. The control ring preload spring is axlally supported by the pump housing. This allows a simple attachment of the damper unit to the pump housing and the control ring and allows a very compact design of the lubricant vane pump.

Alternatively, the damper unit can be arranged within the pilot chamber to allow another simple attachment of the damper unit to the pump housing and the control ring.

Preferably, the damper unit comprises a damper housing and a damper piston. This damper unit embodiment allows a reliable damping and can be simply Integrated within a hydraulic chamber of the lubricant pump thereby using the lubricant as hydraulic liquid. This damper unit embodiment is particularly suitable for pumps with an exactly linear shlftable control ring. In a preferred embodiment of the Invention, the damper housing is attached to the pump housing or can be provided as a part of the pump housing. The damper housing defines a preferably cylindrical damper chamber In which the damper piston is moved In axial direction. The damper piston is attached to the control ring or can be provided as a part of the control ring. The movement of the piston varies the volume of a damper displacement chamber which is axlally defined by the piston frontend and the piston frontend-faclng axial damper housing wall. This embodiment of the damper unit allows a simple and reliable Integration of the damper unit, for example. Into the spring chamber or Into the pilot chamber of the pump.

Two embodiments of the Invention are described with reference to the accompanying drawings, wherein

figure 1 shows a schematic longitudinal section of a first embodiment of a variable lubricant vane pump according to the Invention, and

figure 2 shows a schematic longitudinal section of a second embodiment of a variable lubricant vane pump according to the Invention. Figure 1 shows a variable lubricant vane pump 110 being part of a pumping system for supplying an Internal combustion engine (not shown) with pressurized lubricant. The variable lubricant vane pump 110 is mechanically driven by the Internal combustion engine. The pump 110 comprises a pump housing 112 defining an Inlet chamber 113, an outlet chamber 114, a pumping chamber 115 with a rotatable pump rotor 116 and with a shlftable control ring 118, a spring chamber 120 with a control ring preload spring 122 and with a damper unit 124, and defining a pilot chamber 126. The pump Inlet chamber 113 is provided with atmospheric pressure PA and is fluldlcally connected to a lubricant tank 127. The pump outlet chamber 114 is pressurized with a pump outlet pressure PO and is fluldlcally connected with the Internal combustion engine.

The pump rotor 116 is located within the control ring 118 and rotates In counterclockwise direction about a static axis of rotation A. The pump rotor 116 is provided with seven rotor vanes 128 being supported radially slldable within corresponding vane silts 129. The pump housing 112, the control ring 118 and the rotor vanes 128 define seven rotating pumping chamber compartments 130 ₁ -130 ₇ .

The control ring 118 is supported by the pump housing 112 and is shiftable exactly linear with respect to the pump rotor 116. The volumetric pump performance of the pump 110 can be controlled by moving the control ring 118 and thereby varying the eccentricity of the pump rotor 116 with respect to the surrounding control ring 118.

The control ring 118 is preloaded by the control ring preload spring 122 pushing the control ring 118 Into a hlgh-eccentricity direction h. As a result, If no other forces In shifting direction of the control ring 118 are effective with respect to the control ring 118, the control ring 118 is pushed Into the maxlmum-eccentrlclty position providing the maximum volumetric pump performance.

The control ring 118 is loaded In the opposing low-eccentrlclty direction I by the pressure of the pilot chamber 126. The pilot chamber 126 is fluldlcally connected with the pump outlet chamber 114 by a pilot chamber channel 132 and, as a result, is pressurized with the pump outlet pressure PO. The control ring 118 is loaded In the hlgh-eccentriclty direction h by the pressure of the spring chamber 120. The spring chamber 120 is fluldlcally connected with the pump outlet chamber 114 via a spring chamber channel 134 and is fluldlcally connected with a lubricant tank 127 via a control valve 136. The lubricant tank 127 is provided with atmospheric pressure PA. As a result, the control valve 136 allows controlling the spring chamber 120 pressure In the pressure range between the atmospheric pressure PA and the pump outlet pressure PO. The radial position of the shlftable control ring 118 depends on the ratio of the spring chamber 120 pressure to the pilot chamber 126 pressure and, as a result, can be controlled via the control valve 136. The pump 110 is provided with a bl-dlrectlonal damper unit 124 arranged within the spring chamber 120. The damper unit 124 is attached to the static pump housing 112 as well as to the shlftable control ring 118 and supports the control ring preload spring 122. The damper unit 124 comprises a cylindrical damper housing 138 provided as a part of the pump housing 112 and defining a cylindrical damper chamber 140. Alternatively, the damper housing 138 can be provided as a separate part being attached to the pump housing 112. The damper unit 124 also comprises a cylindrical damper piston 142 being axlally shlftable within the damper chamber 140. The damper piston 142 is positively connected with the control ring 118 via a piston form lock means 143. Alternatively, the damper piston 140 can be provided as a part of the control ring 118. The damper piston 142 is provided of a material with a relatively high thermal expansion coefficient compared to the thermal expansion coefficient of the damper housing 138 material.

The pump housing 112, the damper piston frontend 144 and the piston frontend-faclng axial damper housing wall 145 define a damper displacement chamber 146 with a volume VD depending on the axial damper piston 142 position and, as a result, depending on the control ring 118 position. The gap between the plston-faclng circumferential damper housing sldewall 148 and the circumferential damper piston surface 150 defines a damper balance channel 152 fluldlcally connecting the damper displacement chamber 146 and the spring chamber 120. When the piston 142 is axlally moved within the damper housing 140, the damper displacement chamber volume VD is varied so that lubricant is pressed out of or sucked Into the damper displacement chamber 146 via the damper balance channel 152. The lubricant flow rate through the damper balance channel 152 determines the piston 142 movement damping ratio and, as a result, the control ring 118 movement damping ratio.

The damper balance channel 152 lubricant flow rate is directly proportional to the damper balance channel 152 cross section. Since the piston 142 material provides a higher thermal expansion coefficient than the damper housing 138 material, the damper balance channel 152 cross section decreases with Increasing lubricant temperature. This allows to, at least partially, compensate damper unit 124 damping ratio changes caused by the temperature dependent lubricant.

Figure 2 shows an alternative variable lubricant vane pump 210 according to the Invention. The features of the lubricant vane pump 210 of figure 2 which correspond with the features of the lubricant vane pump 110 of figure 1 have a reference number Increased by 100.

The pump 210 is provided with a damping unit 224 being arranged within the pilot chamber 226. The damper housing 238 is provided as a part of the pump housing 212. The damper piston 242 is provided as a part of the control ring 218. The plston-faclng circumferential damper housing sldewall 248 and the circumferential damper piston surface 250 define the damper balance channel 252. The axial movement of the piston 242 within the damper chamber 240 and, as a result, the control ring 118 movement is damped caused by the limited lubricant flow out of or Into the damper displacement chamber 246 through the damper balance channel 252.

Reference list

110 variable lubricant vane pump

112 pump housing

113 Inlet chamber

114 outlet chamber

115 pumping chamber

116 rotatable pump rotor

118 shlftable control ring

120 spring chamber

122 control ring preload spring

124 damper unit

126 pilot chamber

127 lubricant tank

128 rotor vanes

129 vane silts

130 ₁ -130 ₇ pumping chamber compartments

132 pilot chamber channel

134 spring chamber channel

136 control valve

138 cylindrical damper housing

140 cylindrical damper chamber

142 cylindrical damper piston

143 piston form lock means

144 damper piston frontend

145 piston frontend-faclng axial damper housing wall

146 damper displacement chamber

148 circumferential damper housing sldewall

150 circumferential damper piston surface

152 damper balance channel

210 variable lubricant vane pump

212 pump housing 213 Inlet chamber

214 outlet chamber

215 pumping chamber

216 rotatable pump rotor

218 sh!ftable control ring

220 spring chamber

222 control ring preload spring

224 damper unit

226 pilot chamber

227 lubricant tank

228 rotor vanes

229 vane silts

230 ₁ -230 ₇ pumping chamber compartments

232 pilot chamber channel

234 spring chamber channel

236 control valve

238 cylindrical damper housing

240 cylindrical damper chamber

242 cylindrical damper piston

244 damper piston frontend

245 piston frontend-faclng axial damper housing wall

246 damper displacement chamber

248 circumferential damper housing sldewall

250 circumferential damper piston surface

252 damper balance channel

A axis of rotation

PA atmospheric pressure

PO pump outlet pressure

VD displacement chamber volume