JP2009097353A - Plunger pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plunger pump sucking a fluid from independent two channels and delivering the fluid to one channel without complicating a channel structure. <P>SOLUTION: The plunger pump is provided with a large diameter bore 35a and a small diameter bore 35b mutually concentrically disposed in a cylinder 32. A large diameter plunger 38 defining a first pump chamber 36 between a cylinder 32 and the same is fitted in the large diameter bore 35a, and a small diameter plunger 39 defining a second pump chamber 37 between a cylinder 32 and the same in the small diameter bore 35b. A first suction valve 51 is provided in a suction port 41 connected to the first pump chamber 36, a first delivery valve 53 is provided on a first pump chamber 36 side of a communication passage 50 providing communication between the first and the second pump chambers 36, 37, and a second suction valve 52 is provided on the second pump chamber 37 side. A second suction port 42 is communicated to the communication passage 50 between the first delivery valve 53 and the second suction valve 52, and a second delivery valve 54 is provided in a delivery port 43 communicating with the second pump chamber 37. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement of a plunger pump that includes a cylinder and a plunger that can slide in the cylinder, and that reciprocates the plunger by cooperation of a rotating cam shaft and a return spring.

Such a plunger pump is already known as disclosed in Patent Document 1, and a brake hydraulic control device for a vehicle using such a pump is already known as disclosed in Patent Document 2. It has been.
JP 2006-183619 A JP 2001-63542 A

  The conventional plunger type pump has only one suction port for one discharge port. Therefore, when sucking fluid from two independent flow paths and discharging it to one flow path, Since there were multiple plunger pumps that operated individually, it was not possible to avoid the increase in size and cost of the pump device. In addition, an open / close valve is provided in one flow path and the other flow path is checked to prevent mutual interference between the two flow paths so that fluid can be drawn from two independent flow paths with one pump. A valve is known (see Patent Document 2), but in this case, the flow path structure becomes complicated.

  The present invention has been made in view of such circumstances, and allows fluid to be sucked from two independent flow paths and discharged into one flow path without complicating the flow path structure. An object of the present invention is to provide a plunger pump that is simple in structure, compact, and inexpensive.

  In order to achieve the above object, the present invention provides a plunger pump comprising a cylinder and a plunger that can slide in the cylinder, and reciprocating the plunger by cooperation of a rotating cam shaft and a return spring. The cylinder is provided with a large-diameter bore and a small-diameter bore that are arranged coaxially with each other. A large-diameter plunger that is slidably fitted in the large-diameter bore and defines a first pump chamber between the cylinder and a small-diameter bore is slid. The plunger is constituted by a small-diameter plunger that is movably fitted and defines a second pump chamber between the cylinder and a first suction port that communicates with the first pump chamber, and communicates with the first pump chamber. A first suction valve that opens when the first pump chamber is depressurized, and a first discharge valve that opens when the pressure of the first pump chamber is increased in a communication path communicating between the first and second pump chambers; , Open when the second pump chamber is depressurized A second suction valve, a second suction port communicating with the communication path between the first discharge valve and the second suction valve, and a discharge port communicating with the second pump chamber, and a second pump chamber. A first feature is that a second discharge valve that communicates and opens when the pressure in the second pump chamber is increased is provided.

  In addition to the first feature, the present invention has a second feature that the small-diameter plunger is provided with the communication passage and the first discharge valve and the second suction valve attached thereto.

  The plunger pump corresponds to plunger hydraulic pumps 8a and 8b in the embodiments of the present invention to be described later.

  According to the first feature of the present invention, the plunger-type pump is separated from two independent oil passages by the pumping action of the first and second pump chambers by the operation of the large-diameter plunger and the small-diameter plunger aligned in the axial direction. Fluids can be sucked and discharged into the same oil passage. Therefore, it is possible to draw fluid from two independent flow paths and discharge them into one flow path without complicating the flow path structure with one plunger type pump, and the structure is simple. It is compact and can reduce costs.

  According to the second feature of the present invention, in particular, the oil passage structure is simplified and the plunger pump is made compact by providing the small-diameter plunger with the communication passage provided with the first discharge valve and the first suction valve at both ends. Can be further promoted.

  Embodiments of the present invention will be described based on an embodiment of the present invention shown in the accompanying drawings.

  FIG. 1 is a hydraulic circuit diagram of a front wheel drive type automobile brake device equipped with a plunger type hydraulic pump according to an embodiment of the present invention, and FIG. 2 is an enlarged longitudinal sectional view of the hydraulic pump.

  First, in FIG. 1, the master cylinder M is configured in a tandem type having a pair of front and rear first and second output ports 1a, 1b that output brake hydraulic pressure in response to an input applied from a brake pedal P to a piston. The first and second input oil passages 2a and 2b individually connected to the first and second output ports 1a and 1b, the left front wheel wheel brake Ba, the right rear wheel wheel brake Bb, and the right front wheel wheel brake The modulator 3 is interposed between the first to fourth output oil passages 12a to 12d individually provided for Bc and the left rear wheel brake Bd.

  The modulator 3 includes brake control valve means 4. The brake control valve means 4 includes first to fourth inlet valves 5a individually corresponding to a left front wheel brake Bb, a right rear wheel brake Bb, a right front wheel brake Bc, and a left rear wheel brake Bd, respectively. To 5d, and first to fourth outlet valves 6a to 6d individually corresponding to the respective wheel brakes Ba to Bd, and each of the inlet valves 5a to 5d is a normally open solenoid valve, Each of the outlet valves 6a to 6d is a normally closed electromagnetic valve. The first input oil passage 2a is connected to the inlets of the first and second inlet valves 5a and 5b, and the second input oil passage 2b is connected to the inlets of the third and fourth inlet valves 5c and 5d. A first output oil passage 12a is provided at the outlet of the first inlet valve 5a and the inlet of the first outlet valve 6a. A second output oil passage 12b is provided at the outlet of the second inlet valve 5b and the inlet of the second outlet valve 6b. The third output oil passage 12c is connected to the outlet of the third inlet 5c and the inlet of the third outlet valve 6c, and the fourth output oil passage 12d is connected to the outlet of the fourth inlet valve 5d and the inlet of the fourth outlet valve 6d.

  First and second hydraulic pumps 8a and 8b driven by a common electric motor 17 are provided. Each of the hydraulic pumps 8a and 8b includes a pair of first and second suction ports 41 and 42 and a single discharge port. 43, and the outlets of the first and second outlet valves 6a, 6b are connected to the first suction port 41 of the first hydraulic pump 8a via the first pressure reducing oil passage 7a, and the third, fourth, The outlets of the outlet valves 6c and 6d are connected to the first suction port 41 of the second hydraulic pump 8b via the second pressure reducing oil passage 7b, and the first and second pressure reducing oil passages 7a and 7b are connected to the first and second outlets. Reservoirs 9a and 9b are connected to each other.

  The discharge port 43 of the first hydraulic pump 8a is connected to the first input oil passage 2a via the first pressure increase oil passage 11a, and the discharge port 43 of the second hydraulic pump 8b passes the second pressure increase oil passage 11b to the second. Connected to the input oil passage 2b. Further, an orifice 10 and a damper 13 for absorbing pulsation of the discharge pressure of the corresponding hydraulic pumps 8a and 8b are connected to the first and second pressure increasing oil passages 11a and 11b.

  The first and second input oil passages 2a and 2b are provided with a cut valve 14 consisting of a normally open electromagnetic valve upstream from the connection point of the first and second pressure increase oil passages 11a and 11b.

  A first suction oil passage 15a branched from the first input oil passage 2a upstream from the cut valve 14 is connected to the second suction port 42 of the first hydraulic pump 8a, and the second suction port of the second hydraulic pump 8b. The second suction oil passage 15b branched from the second input oil passage 2b upstream of the cut valve 14 is connected to 42.

  Connected to the first input oil passage 2a or the second input oil passage 2b is an oil pressure sensor 21 (master cylinder operating state detection means) that detects the output oil pressure of the master cylinder M and outputs a signal corresponding thereto. Is input to the electronic control unit 20. In addition to the hydraulic pressure sensor 21, the electronic control unit 20 includes a wheel speed sensor 22 that detects the rotational speed of each wheel, a steering angle sensor 23 that detects the steering angle of the steering handle, and a yaw rate sensor that detects the yaw rate of the vehicle. 24, detection signals from a radar 25 or the like for detecting the distance to an obstacle ahead of the vehicle are input, and these signals are calculated to control each part of the brake control valve means 4 and 4.

  Next, the first and second hydraulic pumps 8a and 8b will be described with reference to FIG.

  The first and second hydraulic pumps 8a and 8b are both plunger type, and are configured symmetrically with the cam shaft 30 driven to rotate by the electric motor 17, so that only the first hydraulic pump 8a is described in detail. Explained.

  A mounting hole 31 extending in the radial direction of the cam shaft 30 is provided in the body 3a of the modulator 3, and an inward annular step portion 31a is provided at the opening end of the mounting hole 31 on the cam shaft 30 side. A cylinder 32 is fitted into the mounting hole 31 so that one end thereof is in contact with the annular step portion 31a, and a bottomed cylindrical cylinder cap 33 is fitted to the inner peripheral surface of the other end of the cylinder 32. Then, a plug 34 that presses the cylinder 32 toward the annular step portion 31 a through the flange 33 a on the outer periphery of the cylinder cap 33 is screwed into the attachment hole 31. The cylinder 32 includes a first large-diameter bore 35a having one end opened on the camshaft 30 side, a small-diameter bore 35b having one end coaxially connected to the other end of the first large-diameter bore 35a, and the other end of the small-diameter bore 35b. A second large-diameter bore 35c that is coaxially connected at one end is provided, and a large-diameter plunger 38 that defines a first pump chamber 36 between the first large-diameter bore 35a and the cylinder 32 is fitted into the first large-diameter bore 35a. The small-diameter bore 35b is fitted with a small-diameter plunger 39 defining a second pump chamber 37 surrounding the small-diameter plunger 39 with the cylinder cap 33.

  The large-diameter plunger 38 is disposed so that its end surface is slidably in contact with the outer peripheral surface of the cam shaft 30, and the large-diameter plunger 38 is placed in the second pump chamber 37 in the contact direction with the cam shaft 30. A return spring 40 that is constantly urged is accommodated, and the plungers 38 and 39 are integrally formed by the cooperation of the pushing-up force of the rotating cam shaft 30 with respect to the large-diameter plunger 38 and the return force of the return spring 40 with respect to the small-diameter plunger 39. As a result, the volume of the first and second pump chambers 36 and 37 is increased or decreased by reciprocating in the axial direction.

  The body 3 a of the modulator 3 is provided with a first suction port 41, a second suction port 42, and a discharge port 43. The first suction port 41 is connected to the first decompression oil passage 7a at one end thereof, and through a first annular oil passage 44 surrounding the cylinder 32 at the other end and a plurality of small holes 45 in the peripheral wall of the cylinder 32. To the first pump chamber 36. The first suction port 41 is provided with a first suction valve 51 that opens when the first pump chamber 36 is decompressed. The first suction valve 51 can also be provided in a passage connected to the upstream side of the first suction port 41.

  The second suction port 42 is connected to the first suction oil passage 15a at one end, and has a second annular oil passage 47 surrounding the cylinder 32 at the other end and a plurality of small holes 48 in the peripheral wall of the cylinder 32. And communicates with the communication passage 50 penetrating through the central portion of the small-diameter plunger 39. A first discharge valve 53 that opens when the pressure of the first pump chamber 36 is increased is provided at the end of the communication path 50 on the first pump chamber 36 side, and at the end of the communication path 50 on the second pump chamber 37 side. Is provided with a second suction valve 52 that opens when the second pump chamber 37 is depressurized.

  The first discharge valve 53 includes a valve seat member 56 that is press-fitted and fixed to the end of the small-diameter plunger 39 on the side of the large-diameter plunger 38, and the valve hole 57 that passes through the center of the valve seat member 56 has a large-diameter and small-diameter plunger. The first and second pump chambers 36 communicate with each other through radial oil grooves 46 provided on the contact end surfaces 38 and 39. A valve chamber 58 connected to the communication passage 50 is provided on the back side of the valve seat member 56, and a cage 55 fixed to the small-diameter plunger 39 together with the valve seat member 56 is disposed in the valve chamber 58. The cage 55 accommodates a ball valve body 59 that can be seated on the valve seat 56a of the valve seat member 56, and a valve spring 60 that biases the ball valve body 59 toward the valve seat 56a. The ball valve body 59 opens when the first pump chamber 36 is pressurized.

  The second suction valve 52 includes a valve seat 61 formed at the open end of the communication passage 50 to the second pump chamber 37, a poppet valve body 62 that can be seated on the valve seat 61, and the poppet valve body 62. A valve spring 63 that urges the valve seat 61 in the seating direction and a cage 64 that holds the fixed end of the valve spring 63 are formed. The cage 64 is connected to the small-diameter plunger 39 and the cam shaft 30 side. It is clamped between the return spring 40 to be urged.

  The discharge port 43 is connected to the first pressure rising oil passage 11 a at one end, and through the oil groove 65 between the cylinder cap 33 and the plug body 34 and the discharge chamber 66 and the second discharge valve 54 at the other end. It communicates with the second pump chamber 37. The second discharge valve 54 includes a valve seat 67 formed on the end wall of the cylinder cap 33, a ball valve body 68 that can be seated on the valve seat 67, and a valve spring that urges the ball valve body 68 in the closing direction. 69 and a cage 70 that is locked to the cylinder cap 33 to hold the valve spring 69, and opens when the second pump chamber 37 is pressurized.

  In FIG. 2, reference numerals 71 to 74 denote seal members.

Next, the operation of this embodiment will be described.
[Normal brake]
During normal braking in which each wheel is not likely to lock, each inlet valve 5a to 5d is demagnetized and opened, and each outlet valve 6a to 6d is also demagnetized and closed. . Now, when the master cylinder M is operated by depressing the brake pedal P, the output hydraulic pressure from the first output port 1a is the first input oil passage 2a, the cut valve 14, the first and second inlet valves 5a, 5b and the first. , Are supplied to the left front wheel wheel brake Ba and the right rear wheel wheel brake Bb via the second output oil passages 12a and 12b, and operate them. The output hydraulic pressure from the second output port 1b is for the right front wheel via the second input oil passage 2b, the cut valve 14, the third and fourth inlet valves 5c and 5d, and the third and fourth output oil passages 12c and 12d. The brakes are supplied to the wheel brake Bc and the left rear wheel brake Bd to operate them.

  In this case, the output hydraulic pressure of the first and second output ports 1a and 1b is connected to the first and second hydraulic pumps 8a and 8b via the first and second suction oil passages 15a and 15b and the second suction port 42. The pressure is also transmitted to the passage 50 and acts on the first discharge valve 53. However, since the direction of the hydraulic pressure is the closing direction of the first discharge valve 53, the first discharge valve 53 maintains the closed state. Will continue. The output hydraulic pressures of the first and second output ports 1a and 1b are also supplied to the discharge chambers 66 of the first and second hydraulic pumps 8a and 8b via the first and second boost oil passages 11a and 11b and the discharge port 43. It is transmitted and acts on the second discharge valve 54, but since the direction of the hydraulic pressure is the closing direction of the second discharge valve 54, the second discharge valve 54 continues to maintain the closed state. .

Therefore, the first and second suction oil passages 15a and 15b and the first and second pressure increase oil passages 11a and 11b to the first and second pressure reduction oil passages 7a and 7b, that is, the first and second reservoirs 9a and 9b. The hydraulic leak can be prevented. Therefore, it is not necessary to provide the suction valve 16a and the check valve 10 as described in Patent Document 2, which can contribute to the reduction in the number of parts and the simplification of the hydraulic circuit.
[Anti-lock control]
When the wheel is about to enter the locked state at the time of braking, the electronic control unit 20 activates the inlet valve corresponding to the wheel that is about to be locked among the first to fourth inlet valves 5a to 5d. While closing the valve, the outlet valve corresponding to the wheel among the first to fourth outlet valves 6a to 6d is excited and opened. Then, a part of the hydraulic pressure of the wheel brake corresponding to the wheel is absorbed into the first reservoir 9a or the second reservoir 9b through the corresponding outlet valve and the corresponding decompression oil passages 7a and 7b, and the wheel The brake hydraulic pressure is reduced.

  In order to keep the wheel brake hydraulic pressure constant, the inlet valves 5a to 5d corresponding to the wheel brake may be excited and closed, and the outlet valves 6a to 6d may be demagnetized to be closed. When the brake hydraulic pressure is increased, the inlets 5a to 5d are demagnetized and opened, and the outlet valves 6a to 6d are demagnetized and closed. By controlling in this way, braking can be performed efficiently without locking the wheels.

During such antilock control, the electronic control unit 20 energizes the electric motor 17 to rotationally drive the camshaft 30 and simultaneously reciprocates the large diameter plunger 38 and the small diameter plunger 39 of the first and second hydraulic pumps 8a and 8b. The volume of the first and second pump chambers 36 and 37 is increased or decreased simultaneously. Thus, when the first pump chamber 36 is depressurized, the brake oil absorbed in the first and second reservoirs 9a and 9b is absorbed by the first and second depressurized oil passages 7a and 7b, the first suction port 41 and the first suction port 41. 1 is sucked through the suction valve 51 and is discharged into the communication passage 50 when the pressure is increased. The second pump chamber 37 sucks the hydraulic fluid in the communication passage 50 through the second suction valve 52 when the pressure is reduced, and the pressure is increased. Since the discharge oil is sometimes discharged into the discharge chamber 66, the discharged oil flows back from the discharge chamber 66 to the first and second input oil passages 2a and 2b through the first and second pressure increase oil passages 11a and 11b. By this recirculation, an increase in the depression amount of the brake pedal P due to the absorption of the brake oil in the reservoirs 9a and 9b is suppressed.
[Automatic brake control 1 (traction control)]
For example, when the front wheel that is the driving wheel is likely to run idle when the vehicle starts, the electronic control unit 20 calculates the rotation difference between the front wheel and the rear wheel from the signal sent from the wheel speed sensor 22 of each wheel, and the rotation difference. Is determined to be in the idling state, the cut valve 14, the second inlet valve 5b and the fourth inlet valve 5d are excited and closed, and the electric motor 17 is operated to rotate the camshaft 30. The large-diameter plunger 38 and the small-diameter plunger 39 of the first and second hydraulic pumps 8a and 8b are reciprocated to increase or decrease the volumes of the first and second pump chambers 36 and 37. In this case, in particular, by the operation of the second pump chamber 37, the hydraulic oil of the master cylinder M is sucked from the first and second output ports 1a, 1b through the first suction oil passage 15a, and the boost oil passages 11a, 11b, The left and right front wheel brakes Ba and Bc are supplied to the left and right front wheel brakes Ba and Bc through the first and third inlet valves 5a and 5c, and the flow of the hydraulic oil to the master cylinder M side is blocked by the closed cut valve 14. The front wheel brakes Ba and Bc can be operated to automatically prevent the front wheels from slipping.

At that time, when the oil pressure of the front wheel brakes Ba and Bc is kept constant, the inlet valves 5a to 5d are energized and closed, and the outlet valves 6a to 6d are demagnetized as in the anti-lock control. In order to increase the brake hydraulic pressure, the inlet valves 5a to 5d are demagnetized and opened, and the outlet valves 6a to 6d are demagnetized and returned to the closed state. Thus, it is possible to prevent the front wheels from slipping and to control the driving torque appropriately.
[Automatic brake control 2 (brake assist)]
When the master cylinder M is actuated by depressing the brake pedal P, the hydraulic sensor 21 detects the master cylinder output hydraulic pressure and outputs a signal corresponding thereto to the electronic control unit 20. The output boosting speed of M is calculated, and when the boosting speed exceeds a specified threshold value, it is determined that a sudden braking operation is being performed, and the electric motor 17 is operated to drive the first and second hydraulic pumps 8a and 8b. At the same time, the cut valve 14 is excited and closed. As a result, the first and second pump chambers 36 and 37 of the first and second hydraulic pumps 8a and 8b are operated. In this case, in particular, the first and second input oil passages 2a are operated by the operation of the second pump chamber 37. , 2b, the hydraulic pressure of the master cylinder M is sucked through the first and second suction oil passages 15a, 15b, and the pressure is increased from each of the pressure rising oil passages 11a, 11b via the open valves 5a-5d to the wheels. Since the pressure is fed to the brakes Ba to Bd, they can be operated strongly and can respond to a sudden braking operation.
[Automatic brake control 3 (vehicle running attitude control)]
When the vehicle is turning left, for example, the output signals of the rudder angle sensor 23 and the yaw rate sensor 24 do not correspond to each other, and the electronic control unit 20 determines that the vehicle is about to turn left, for example, excessively. The control unit 20 operates the electric motor 17 to correct the direction and drives the first and second hydraulic pumps 8a and 8b, as well as the cut valve 14, the first inlet valve 5a and the fourth inlet valve 5d. To close the valve. As a result, the first and second pump chambers 36 and 37 of the first and second hydraulic pumps 8a and 8b are operated. In this case, particularly, the operation of the second pump chamber 37 causes the hydraulic oil in the master cylinder M to be supplied to the first. , Intake through the first suction oil passage 15a from the second output ports 1a, 1b, and through the pressure increase oil passages 11a, 11b, the second and third inlet valves 5b, 5c, the right front wheel brake Bc and the right rear wheel. Since only the brake Bb is supplied and the flow of the hydraulic oil to the master cylinder M side is blocked by the closed cut valve 14, the right front wheel brake Bc and the right rear wheel brake Bb are operated. The vehicle's running posture can be corrected to the right so as to correspond to the rudder angle.

  In order to correct the vehicle direction to the left side, the second inlet valve 5b and the third inlet valve 5c are excited and closed in the opposite direction, and the discharge hydraulic pressures of the first and second hydraulic pumps 8a and 8b are reversed. Are supplied only to the left front wheel brake Ba and the left rear wheel brake Bd through the first and fourth inlet valves 5a, 5d, and operate them.

Further, whether the vehicle is turning right or straight, the traveling posture of the vehicle is controlled by the same action as described above.
[Automatic brake control 4 (vehicle rear-end collision prevention control)]
While the vehicle is traveling, the radar 25 detects the relative speed and distance with respect to the preceding vehicle, and when the electronic control unit 20 determines that there is a possibility of a rear-end collision based on the detected information, the electronic control unit 20 activates the electric motor 17. Then, the first and second hydraulic pumps 8a and 8b are driven and the cut valve 14 is excited to close. As a result, the first and second pump chambers 36 and 37 of the first and second hydraulic pumps 8a and 8b are operated. In this case, particularly, the operation of the second pump chamber 37 causes the hydraulic oil in the master cylinder M to be supplied to the first. , Through the first and second suction oil passages 15a and 15b from the second output ports 1a and 1b, and the pressure is increased and the wheel brakes are passed from the pressure increase oil passages 11a and 11b through the opened inlet valves 5a to 5d. Since the pressure is fed to Ba to Bd, they can be automatically operated to prevent a rear-end collision.

  When the master cylinder M is operated by depressing the brake pedal P during the automatic brake control 1 to 4 described above, the hydraulic pressure sensor 21 receives the output hydraulic pressure and inputs a detection signal to the electronic control unit 20. Upon receiving the signal, the electronic control unit 20 stops the operation of the electric motor 17 to prohibit the automatic brake control, sets the cut valve 14 to the normal open state, and sets all the inlet valves 5a to 5d. All the outlet valves 6a to 6d are returned to the normal valve closed state in the normal valve open state. Accordingly, as in the case of the normal brake, the output hydraulic pressure of the master cylinder M is supplied to all the wheel brakes Ba to Bd and can be operated.

  As is clear from the above, each of the plunger-type hydraulic pumps 8a and 8b has a reduced pressure oil by the pumping action of the first and second pump chambers 36 and 37 by the operation of the large-diameter plunger 38 and the small-diameter plunger 39 arranged in the axial direction. Fluids can be sucked from two mutually independent oil passages such as the passages 7a and 7b and the suction oil passages 15a and 15b, and these can be discharged to the same oil passage called the pressure boosting oil passages 11a and 11b. Therefore, since each one hydraulic pump can perform the function of two conventional hydraulic pumps, the structure of each hydraulic pump 8a, 8b can be simplified without complicating the two oil passage structures. It can contribute to downsizing and downsizing. In particular, the oil passage structure is simplified by providing the small diameter plunger 39 with the communication passage 50 provided with the first discharge valve 53 and the second suction valve 52 at both ends, and the structure of each hydraulic pump 8a, 8b is further simplified. And downsizing can be achieved.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the large diameter plunger 38 and the small diameter plunger 39 can be integrally coupled to each other. The present invention is also applicable to a rear wheel drive vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hydraulic circuit diagram of a front wheel drive type automobile brake device provided with a plunger type hydraulic pump according to an embodiment of the present invention. The expanded longitudinal cross-sectional view of the said plunger type hydraulic pump.

Explanation of symbols

30 ... Cam shaft 32 ... Cylinder 35a ... Large diameter bore 35b ... Small diameter bore 36 ... First pump chamber 37 ... Second pump chamber 38 ... Large diameter plunger 39 ... Small diameter Plunger 40 ... Return spring 41 ... First suction port 42 ... Second suction port 43 ... Discharge port 50 ... Communication path 51 ... First suction valve 52 ... Second suction Valve 53 ... First discharge valve 54 ... Second discharge valve

Claims (2)

In a plunger pump comprising a cylinder (32) and a plunger that can slide in the cylinder (32), and reciprocating the plunger by cooperation of a rotating camshaft (30) and a return spring (40),
The cylinder (32) is provided with a large-diameter bore (35a) and a small-diameter bore (35b) arranged coaxially with each other. A second pump chamber (37) is defined between the large diameter plunger (38) defining the pump chamber (36) and the cylinder (32) slidably fitted in the small diameter bore (35b). The plunger is constituted by a small-diameter plunger (39), communicated with a first pump port (41) communicating with the first pump chamber (36), and with the first pump chamber (36). A first suction valve (51) that opens when the pressure of the first pump chamber (36) is reduced, and a communication passage (50) that communicates between the first and second pump chambers (36, 37), Opened when the first discharge valve (53) and the second pump chamber (37) are depressurized. The second suction valve (52) is provided, and the second suction port (42) is communicated with the communication path (50) between the first discharge valve (53) and the second suction valve (52). A discharge port (43) communicating with the pump chamber (37) and a second discharge valve (54) communicating with the second pump chamber (37) and opening when the pressure of the second pump chamber (37) is increased are provided. Plunger type pump characterized by the above. The plunger pump according to claim 1,
The plunger pump characterized in that the small diameter plunger (39) is provided with the communication passage (50) and the first discharge valve (53) and the second suction valve (52).

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