RADIAL PLUNGER PUMP DRIVEN BY MOTOR

Abstract: A radial plunger pump has a motor housing (315); a motor (411) is provided therein and a pump housing a pump portion is provided therein. The pump portion works when the rotation of the mortor is transmitted to the pump portion through a shaft. The pump housing has a constant pressure chamber between the pump portion and the mortor. The constant pressure chamber is formed between a first seal member and a second seal member, both seal members are fixed to the pump housing. The constant pressure chamber is always open to the outer atmosphere through a constant pressure hole so that the vibration of the pressure within the constant pressure chamber can maintain the atomosphere pressure. The first and second seal member and the constant pressure chamber prevent the leakage of the oil from the pump housing toward the motor housing. Since a plate is provided within the costant pressure chamber in order to make the pressure at the opening portion of the constant pressure port increase, the foreign objects is well prevented to be introduced into the constant pressure chamber through the constant pressure hole.

Description: The present invention relates to a radial plunger pump driven by a motor, the radial plunger pump of the present invention can be used as an oil pump for automotive breake system, for example. Conventionally, a radial plunger pump having a motor provided within a motor housing, a shaft rotatably provided within a pump housing and driven by the motor and a pump portion provided within the pump housing for sucking and discharging the fluid has been known such as described in USP 4, 201, 521. Such conventional type of the pump, however, has disadvantage that the fluid within the pump portion leaks toward the motor. Therefore, the conventional type motor has a seal member provided between the pump housing and the motor housing for preventing the leakage of the fluid. According to the experiment of the present inventors, the seal member provided between the motor housing and the pump housing cannot always seal. Namely, under the special occasion, the fluid within the pump housing leaks toward the motor housing even though the seal member is provided. DE-A-34 26 705 discloses a sealing structure between a rotating member and a stationary member, wherein a first and a second seal member is provided in a certain distance from each other so that a chamber is formed between the two seal members. This chamber is provided with a radial port leading to a means for watching over the pressure in this chamber. Further, a ring plate is provided in this chamber which ring plate has the function of a spacer between the seal members. BE-A-406136 discloses a similar sealing structure between a pump in general, and a bearing, wherein the chamber between two seal members is a constant pressure chamber which is connected by a radial port with the atmosphere. The present invention has an object to reduce the amount of the fluid leaking through the seal member. In order to attain the object, the radial plunger pump of the present invention employs the known constant pressure chamber provided between the pump portion and the motor housing in connection with the features in claim 1 referring to a deformation of the seal member. The first seal member is squeezed into a holding portion provided within the pump housing. Since a holding groove is formed at the inner side of the holding portion, the elastic first seal member is inserted toward the holding groove so that the first seal member is fixed within the holding portion. Accordingly, the first seal member of the present invention is well prevented from dropping off the holding portion. Further the radial plunge pump of the present invention further employs a plate within the constant pressure chamber. The plates rotates within the constant pressure chamber in accordance with the rotation of the shaft so that the centrifugal forth of the plate makes the pressure at the opening of the constant pressure hole to increase higher than the atmospheric pressure. Accordingly, it well prevents that foreign objects come into the constant pressure chamber through the constant pressure hole. Fig. 1 is a sectional view of the radial plunger pump of the present invention, Fig. 2 is a sectional view taken along with II-II line of Fig. 1, Fig. 3 explains an usage of the pump shown in Fig. 1, Figs. 4 and 5 are sectional views of a shoe shown in Fig. 1, Fig. 6 is a sectional view showing a pump portion of the pump shown in Fig. 1, Fig. 7 is a front view of a rotating member, Fig. 8 is a side view of the rotating member shown in Fig. 7, Fig. 9 is a side view of the rotating member shown in Fig. 7, Fig. 10 is a sectional view showing a part of seal member, Fig. 11 is a diagram showing the relationship between the holding length of the seal member and the holding force, Fig. 12 is a sectional view showing the pump portion of the pump shown in Fig. 1, Fig. 13 is a sectional view showing a part of the pump portion of another embodiment, Fig. 14 is a front view showing the shoe shown in Fig. 13, and Fig. 15 is a diagram showing the relationship between the discharge pressure and the noise rebble. DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the radial plunger pump of the present invention is described hereinafter. A pump housing 131 made of aluminum alloy has a suction chamber 133 therein. An eccentric ring 151 is provided within the suction chamber in such a manner that an outer race 153 of the eccentric ring 151 is fixed to the inner surface of the pump housing 131 by a wave washer 180. A pintle housing 111 is provided at the opening end of the pump housing 131 via an O-ring, and the pintle housing is fixed to the pump housing 131 by a bolt 211. The pintle housing 111 has a pintle portion which projects toward the suction chamber 111, a suction connecting port 123 and a discharge connecting port 115 are provided within the pintle portion. The opening end of the suction connecting port 123 faces to the suction chamber 133, and the discharge connecting port 115 is connected with discharge port 113 formed within the pintle housing 111. As shown in Fig. 2, a suction groove 125 and a discharge groove 121 is formed at the outer surface of the pintle portion. A rotor 135 is rotatably supported at the outer surface of the pintle portion. A plurality of cylinder holes 141 are provided within the rotor radially. A piston 143 is slidably provided within the each of cylinder holes 141. A shoe 145 is provided at the top end of the piston 143, and the top end of the shoe 145 is connected within the inner surface of the eccentric ring 151. The eccentric ring 151 has an inner race 154, an outer race 153 and a plurality of balls 155 provided between the inner race 154 and the outer race 153. A spring 170 is provided within the cylinder hole 141 so that the spring 170 biases the piston 143 toward the shoe 145. As shown in Figs. 4 and 5, the shoe 145 has a side guide portion 149 to which the side surface of the inner race 154 abuts so that the movement of the rotor 135 along with the longitudinal axis of the pintle portion is limited by the side guide portion 149 of the shoe 145. It should be noted that there must be exist about 0.1 mm gap between side guide portion 149 and the inner race 154 during the normal operation so that the side guide portion 149 is well prevented to attach to the inner race. A holding hole 148 is formed at the center portion of the shoe 145, the depth P of the holding hole 145 is twice deeper than the eccentric amount ε of the rotor 135, the inner diameter D of the holding hole 148 has such length calculated by the next formula so that the piston can wobble within the holding hole 148. Dp... the outer diameter of the piston 143, r... the radius of the top portion of the piston 143, R... the radius of the inner race 154, S... the thickness of the central portion of the shoe 154 The rotor 135 is connected with a shaft 213 via a rotating member 215 (shown in Figs. 7, 8 and 9). A connecting portion formed at the end portion of the shaft 213 is inserted into the connecting groove 219 formed at the center portion of the rotating member 215 so that the rotating member 215 rotates synchronizedly with the shaft 213. The end portion of the connecting hook 218 is connected with the rotor 135 so that the rotor 135 rotates synchronizedly with the rotating member 215. The rotating member 215 has a stopper 217 the end portion of which faces to the rotor 135 so that the movement of the rotor 135 along with the longetudinal axis of the pintle portion is limited by the stopper 217. The stopper 217 and the connecting hook 218 is formed integrally to the rotating member 215. The rotating member 215 also has a inclining wall 216 at the side surface thereof so that the fluid within the suction chamber 135 is diffused by the rotation of the rotating member 215. The suction chamber 133 is connected to the suction port 221 formed within the pump housing 131 so that the working fluid within a reservoir 415 is introduced into the suction chamber 133 through the suction port 221. A motor housing 315 is fixed to the pump housing 131 by rivets 171. A motor 411 is provided within the motor housing 315 in such a manner that a shaft 213 of the motor 411 projects through the motor housing 315. The shaft 213 is rotatably supported by a bearing 255 mounted on the motor housing 315. The shaft 213 is also supported by the bearing 255 mounted on the pump housing. A plate 172 on which a brush 311 is fixed is provided at the opening end of the motor housing 315. The brush 311 faces to a commutator 313. The motor housing 315 has an atmospheric hole 321 under the commutator 315, the atmospheric hole 321 is covered by a pipe 323 made of rubber. The lead wire of the brash 311 is supported between the motor housing 315 and the pump housing 131 by a bracket 173 made of rubber. A second seal member 241 is provided on the pump housing 131, the second seal member 241 is held within a second holding portion 225 formed within the pump housing 131. The second seal member 241 has a fixing frame 243 and an elastic member made of rubber covered with the fixing frame 243. A first holding portion 223 is formed within the pump housing 131 and a first seal member 233 is provided within the first holding portion 223. The first seal member 233 has a fixing frame 235 and an elastic member covered with the fixing frame. The first seal member 233 also includes a spring 231 which biases the fixing frame toward the shaft 213. As shown in Fig. 1, the outer diameter of the second holding portion 225 is smaller than that of the first holding portion 223. Because the first seal member 233 is fixed within the first holding portion 223 after the second seal member 241 is fixed within the second holding portion 225. An inclining wall 291 is formed at the opening end of the first holding portion 223 so that the seal member 223 can be inserted into the first holding portion 223 smoothly. A first and a second contacting groove 293 and 294 are formed at the inner surface of the first holding portion 223 in such a manner that the inner surface of the contacting groove 293 and 294 incline with the inner surface of the first holding portion 223 so that the seal member 233 can be inserted into the holding portion 223 without disturbed by the contacting groove 293 and that the seal member 233 is well prevented from dropping off the holding portion 223 after the seal member 233 is inserted into the holding portion 223 (as shown in Fig. 10). Fig. 11 shows the efficiency of the contacting groove 293 and 294 Fig. 1 shows the relationship between the deforming amount of the first seal member 233 and the pressure difference between both sides of the first seal member 233. The solid line A shows the relationship under the condition that the holding portion do not have any contacting groove and the working fluid is permeated between the seal member 233 and the holding portion 223, the solid line B shows the relationship under the condition that the holding portion does not have contacting groove and no working fluid is existed between the first seal member 233 and the first holding portion 223, the solid line C shows the relationship under the condition that the holding portion 223 has the contacting grooves 293 and 294 and working fluid is existed between the first seal member 233 and the first holding portion 223, and the solid line D shows the relationship under the condition that the holding portion 223 has the contacting grooves 293 and 294 and no working fluid exists between the first seal member 233 and the first holding portion 223. As shown from Fig. 11, the contacting grooves 293 and 294 can hold the first seal member 233 within the holding portion 223 effectively. The second seal member 241 aparts from the first seal member 233 by a predetermined distance such as about 5 mm so that a constant pressure chamber 245 is formed within the side surface of the first seal member 233, the side surface of the second seal member 241, the inner surface of the pump housing and the outer surface of the shaft 213. The atmospheric pressure is introduced into the constant pressure chamber 245 through a constant pressure hole 253 formed in the pump housing 131 so that the pressure within the constant pressure chamber is always kept under the atmospheric pressure. A ring plate 251 made of an elastic material such as rubber or synthetic resin is provided within the constant pressure chamber 245. The ring plate 251 can also be made of another material such as stainless steel. Since the ring plate 251 is fixed to the outer surface of the shaft 213, the ring plate rotates within the constant pressure chamber. The side portion of the ring plate 251 faces to the constant pressure hole 253. The constant pressure hole 253 has an inner diameter of about 2mm. The operation of the radial plunger pump of the present embodiment is described hereinafter. As shown in Fig. 3, the radial plunger pump is used as a supplying pump for supplying brake fluid of the automotive brake system. The brake fluid within the reservoir 415 is sucked toward the pump 413 through the suction path 421. The brake fluid discharged from the pump 413 is introduced into a master cylinder 425 through a discharge path 423. The pressurised oil is supplied to each of a wheel cylinder 431 in accordance with the movement of the brake pedal 433. The brake fluid is then returned to the reservior 415 through a recovery path 435. The operation of the motor 411 is controlled by a controller (not shown). The rotation of the motor 411 makes the rotor 135 rotate within the suction chamber 133. Since the central axis of the eccentric ring 151 is off-setts from the central axis of the pintle portion as shown in Fig. 2, the piston 143 reciprocates within the cylinder hole 141 in accordance with the rotation of the rotor 135. The volume within the pump chamber 178 formed between the piston 143 and the cylinder hole 141 is varied in accordance with the reciprocation of the piston 143. The inner race 154 rotates synchornizedly with the rotor 135 so that the shoe 145 always contacts with the inner race 154. The shoe 145, however, wobbles against the top end of the piston 143 as shown in Fig. 6. The movement of the shoe 145 against the piston 143 is permitted because the enough space is formed within the holding hole 148 of the shoe 145. The piston 143 is biased toward the shoe 145 by the spring 170 and the centrifugal force. However, the piston 143 may remain within the cylinder under the special condition such as the temperature of brake fluid is low enough to cause high viscous force (as shown in Fig. 12). Since the holding hole of the shoe has the depth p deeper than the eccentric amount ε , the shoe 145 is well prevented from dropping off the top end of the piston 143 even though such special condition. The brake fluid within the suction chamber 133 is sucked toward the pump chamber 178 through a suction connecting port 123 and a suction groove 125 while the volume of the pump chamber 178 increases. The brake oil within the pump chamber 178 is then discharged toward discharge path 423 through the discharge connecting port 125 and the discharge port 113 while the volume of the pump chamber 178 decreases. The pressure of the brake oil within the suction chamber 133 should vary in accordance with the operation of the pump. Since the brake oil within the suction chamber 133 is supplied from the reservoir 415, and since the reservoir 415 is located upper than the pump 413, the pressure of the brake oil within the suction chamber 133 has the head of about 10 -20 mm Hg when the pump 413 is not operated. The pressure of the brake oil within the suction chamber 133 reduces under the atmospheric pressure when the pump 413 operates because the because the brake oil within the suction chamber 133 is sucked toward the pump chamber 178. The negative pressure of the brake oil within the suction chamber 133 may reduce as low as -300 - -400 mm Hg under the special condition such as the temperature of the working fluid is low enough to increase the viscous force of the brake oil. The suction chamber is vacuumed before the oil is introduce so that the pressure within the suction chamber 133 is vacuum temporally. Even though the pressure within the suction chamber 133 is varied, the leakage of the brake oil from the suction chamber toward the motor housing is well prevented by the first and second seal member 233. Since the constant pressure chamber is formed at one side of the first seal member 233, the pressure difference between both sides of the first seal member 233 is occurred mainly by the variation of the pressure within the suction chamber. Since the first seal member 233 is inserted into the first and second contacting grooves 293 and 294, the first seal member 233 is fixed to the first holding portion 223 rigidly. The motor rotates within the motor housing 315 when the voltage is supplied. The rotation of the motor 411 and commutator 313 makes the wind and such wind varies the pressure applied to the second seal member 241. Since the ring plate 251 is provided within the constant pressure chamber 245 in order to increase the pressure at the opening portion of the constant pressure port 253, the foreign objects is well prevented to be introduced into the constant pressure chamber 245. Further-more, since constant pressure port 253 is formed at the lower most portion of the pump housing 131, the introduction of the foreign objects or any other water is well prevented to be introduced. Figs. 13 and 14 shows another embodiment of the present invention. The shoe 145 shown in Figs. 13 and 14 has a notch portion 147 in order to limit the vibration of the shoe 145. Since the central axis of the rotor 135 is offset from the central axis of the inner race 154, the shoe 145 has the tendency to wobble slightly, and such wobble movement make noise. Since the brake oil within the suction chamber 133 is introduced into the contacting surface between the notch portion 147 and the inner race 154, the vibration of the shoe 145 can be reduced, so that the noise caused by the vibration of the shoe 145 is reduced as shown in Fig. 15. The solid line H shows the noise caused by the shoe 145 which has no notch portion 145, the dotted line I shows the noise caused by the shoe 145 having the notch portion 147. As clearly shown from the Fig. 15, the shoe having the notch portion 147 can reduce the noise.

Claims: A radial plunger pump driven by a motor comprising ; a motor housing (315), a motor (411) provided within said housing, a pump housing (131) provided at a side of said motor housing, a shaft (213) rotatably provided within said pump housing and rotating synchronizedly with said motor, a pump chamber (133) provided within said pump housing for sucking and discharging working fluid in accordance with the rotation of said shaft (213), a first holding portion (223) provided within said pump housing, a first seal member (233) fixed to said first holding portion and limiting the leakage of the working fluid along said shaft and said pump housing toward said motor housing, a second holding portion (225) provided within said pump housing at a side portion of said first seal portion, a second seal member (241) fixed within said second holding portion (225) so that said first sealing member (233) and said second seal member (241) form a constant pressure chamber (245) there-between, said second seal member (241) limiting the leakage of the working fluid along said shaft, said first holding portion (223) having a triangular contacting groove (293) facing to said first seal member (223) so that said first seal member is deformed when inserted in order to prevent said first seal member from dropping off said first holding portion, and said pump housing further having a constant pressure port (253) through which atmospheric pressure is introduced into said constant pressure chamber (245). A radial plunger pump according to claim 1, wherein a plate (251) is provided within said constant pressure chamber (233) which plate is connected to said shaft (213). A radial plunger pump according to claims 1 and 2, wherein said constant pressure port (253) faces to said plate (251). A radial plunger pump according to claims 1, 2 and 3, wherein the seal surface of said first seal member (233) is larger than the seal surface of said second seal member (241). A radial plunger pump as claimed in the preceding claims, wherein a plunger (143) is reciprocally provided within a rotor (135), an excentric ring (151) is provided on the outer side of said rotor and a shoe member (145) is provided between the top portion of said plunger and the inner surface of said excentric ring (151), said shoe member (145) has a holding hole (148) in which said top portion of said plunger is inserted, the inner diameter (D) of said holding hole being calculated by the formula of Dp: the outer diameter of said plunger (143) r: radius of said top portion of said plunger R: radius of said excentric ring (151) S: thickness of said shoe member (145). A radial plunger pump as claimed in the preceding claims, wherein: said shoe member (145) has a side guide portion (149) to which a side portion of said excentric ring (151) abuts for limiting the movement of said shoe member along the longitudinal axis of said shaft. A radial plunger pump as claimed in the preceding claims, wherein: the depth of said holding hole (148) is twice deeper than an off-set amount (ε) of said excentric ring (151). A radial plunger pump as claimed in the preceding claims, wherein: a rotating member (215) is connecting said rotor (135) with said shaft (213) for rotating said rotor synchronizedly with said shaft, said rotating member (215) has inclined side walls (216) for diffusing working fluid within said pump housing. A radial plunger pump as claimed in the preceding claims, wherein: said shoe member (145) has a notch portion (147) at the outer surface for introducing working fluid within said pump housing into the gap between said outer surface of said shoe member and the inner surface of said excentric ring (151).

Inventors: ITO, YOSHIAKI, KOIKE, HIDEYUKI, KONDOH, HIROSHI, NAGAI, KOUJI, SAWADA, AKIHIKO
Applicants: NIPPONDENSO CO., LTD.
Application year: 1987
Main classification: F04B1
IPC codes: F16J15, B60T13, F04B1, F04B17