JPH0828438A - Plunger pump - Google Patents

Abstract

PURPOSE:To reduce surge pressure and oil pressure pulsation without reducing pump displacement by providing a damping chamber adjacent to a pump chamber, and communicating the damping chamber with the pump chamber through an orifice while receiving a variable volume elastic member in the damping chamber. CONSTITUTION:A damping structure is provided with a damping structure which is composed of a damping chamber 16, orifice 17 and elastic member 15. When a plunger 8 shifts from the suction stroke for opening a suction port 12 near the lower dead point to the compression stroke for closing the suction port 12 with the opening edge of a cylinder 7, the pump chamber 9 is tightly closed to abruptly increase the pressure therein. Then, differential pressure is generated between the pump chamber 9 and damping chamber 16 and working oil flows gently through the orifice 17 into the damping chamber 16, so that the pressure in the pump chamber 9 is restrained from the abrupt rise. Hence, surge pressure generated immediately before the opening of a check valve 20 is kept extremely low and oil pressure pulsation is also reduced immediately after the opening of the check valve 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger pump used as a pressure supply source for an automobile hydraulic suspension device, an anti-lock brake device, etc. Regarding

[0002]

2. Description of the Related Art As a plunger pump of this type, one disclosed in Japanese Utility Model Laid-Open No. 2-67083 has been proposed.

In this plunger pump, a plunger that reciprocates by driving a cam is fitted into a cylinder, and a space surrounded by the cylinder and the plunger is a pump chamber. When the plunger projects into the suction chamber, The working oil is sucked into the pump chamber through the suction hole formed in the peripheral wall, and when the plunger retracts, the working oil is pressurized to be discharged to the discharge passage. Further, normally, a check valve that allows a flow in the discharge direction is provided in the discharge passage, and surge pressure or hydraulic pulsation due to the delay in the operation of the check valve is likely to occur. A damping structure is provided to reduce surge pressure and hydraulic pulsation. In this damping structure, a casing that communicates with the pump chamber accommodates a piston that receives the internal pressure of the pump chamber and a coil spring that urges the piston in the pump chamber direction. Is reduced by the elasticity of the coil spring.

[0004]

However, in the case of the above-mentioned conventional plunger pump, since the pressure fluctuation is reduced by the elasticity of the coil spring, the diameter of the coil spring becomes large in order to reduce a large surge pressure and the size of the apparatus becomes large. It is conceivable that the piston and the casing are likely to be worn over time due to the piston sliding in the casing.

A plunger pump in which an elastic member such as a rubber material whose volume can be changed is directly installed in the pump chamber and pressure fluctuation is reduced by this elastic member has been devised from the past. In this case, although the problems such as an increase in size and wear of the device are solved, the elastic member largely deforms elastically at the beginning of the compression process of the plunger and delays the rise of pressure in the pump chamber. Another drawback is that the pump capacity is reduced.

Therefore, the present invention intends to provide a plunger pump which can surely reduce surge pressure and hydraulic pulsation without increasing the size of the apparatus and lowering the durability of parts, and moreover, without reducing the pump capacity. It is what

[0007]

As a means for solving the above-mentioned problems, the invention of claim 1 forms a pump chamber by a cylinder and a plunger fitted to the cylinder, and reciprocates the plunger. In the plunger pump that discharges the hydraulic oil sucked into the pump chamber by the discharge passage having the check valve, a damping chamber facing the pump chamber is provided, and the damping chamber and the pump chamber are communicated with each other by an orifice, An elastic member whose volume can be changed was housed in the damping chamber.

Further, the invention of claim 2 is provided with a valve device for opening the orifice when the pressure difference between the pump chamber and the damping chamber becomes equal to or higher than a set pressure.

[0009]

In the invention of claim 1, when the pressure in the pump chamber fluctuates, a differential pressure is generated between the pump chamber and the damping chamber,
This differential pressure causes the hydraulic oil to pass through the orifice, causing the hydraulic oil to flow between the pump chamber and the damping chamber. Sudden pressure fluctuations in the pump chamber are reduced by this flow.
Further, since the flow rate of the hydraulic oil between the pump chamber and the damping chamber is determined by the volume of the damping chamber and the amount of the elastic member accommodated therein, the pressure inside the pump chamber can be changed by changing these appropriately. The characteristics can be adjusted.

In the second aspect of the present invention, the flow start timing of the hydraulic oil between the pump chamber and the damping chamber can be adjusted by appropriately changing the valve opening pressure of the valve device.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

1 and 2, reference numeral 1 denotes a housing of a plunger pump according to the present invention, in which a drive shaft 2 is rotatably accommodated via bearings 3 and 4. The drive shaft 2 is provided with an eccentric cam 5, and the housing 1 is formed with an intake chamber 6 which accommodates the eccentric cam 5 so as to be eccentrically rotatable. The suction chamber 6 communicates with a suction passage (not shown), and hydraulic oil is introduced from the outside through the suction passage. Further, a plurality of cylinders 7 are radially provided outside the suction chamber 6 of the housing 1, and a cylindrical plunger 8 having a bottom is slidably fitted to each cylinder 7. A space surrounded by each of the cylinders 7 and the plunger 8 has a pump chamber 9 that repeatedly expands and contracts in volume by the reciprocating motion of the plunger 8.
To form.

The bottom of each cylinder 7 is closed by a plug 10 mounted from the outer peripheral side of the housing 1. Between the plug 10 and the plunger 8 facing the plug 10, the plunger 8 is always mounted on the eccentric cam 5. A spring 11 for urging so as to press is interposed. Therefore, when the eccentric cam 5 is eccentrically rotated, each plunger 8 repeatedly projects and retracts from the cylinder 7 by the elastic force of the spring 11 and the pushing-up action of the eccentric cam 5. Also,
Plural suction holes 12 are formed in the peripheral wall of the plunger 8, and when the plunger 8 moves to the vicinity of the bottom dead center,
The hydraulic oil in the suction chamber 6 is supplied to the pump chamber 9 through the suction hole 12.
It sucks inside.

The cylinder 7 of each spring 11
A spring retainer 13 having a hat-shaped cross section is attached to the end on the bottom (plug 10) side of the. This spring retainer 13 has a bottomed cylindrical top 13a fitted into the end of the spring 11, while a flange 13b.
Supports the end of the spring 11.
On the other hand, a recess 14 is provided at the bottom of the cylinder 7, and an elastic member 15 such as rubber or silicon whose volume can be changed is accommodated in the recess 14. The flange portion 13
b is in contact with the peripheral portion of the recess 14, and the space surrounded by the recess 14 and the spring retainer 13 is the damping chamber 16 in the present invention. Further, an orifice 17 having a predetermined diameter is provided on the end surface of the top portion 13a of the spring retainer 13 so that the pump chamber 9 and the damping chamber 16 communicate with each other. This orifice 17
When a differential pressure is generated between the pump chamber 9 and the damping chamber 16, the hydraulic oil passes through, and the flow of the hydraulic oil between the chambers 9 and 16 at this time reduces the pressure fluctuation in the pump chamber 9. It has become. The elastic member 15 is provided in both chambers 9,
This is for increasing the flow amount of the hydraulic oil between the parts 16, and in this embodiment, it is formed in a ring shape so as to fit into the inner circumference of the recess 14.

The vicinity of the bottom of each cylinder 7 communicates with a discharge passage 18, and each discharge passage 18 communicates with one damping pot 19 provided in the housing 1. A check valve 20 that allows only the flow in the discharge direction is provided at the end of each discharge passage 18 that opens to the damping pot 19.
It communicates with an external discharge pipe (not shown).

With the above structure, when the drive shaft 2 starts to rotate by an external power source such as an engine,
The eccentric cam 5 sequentially pushes up each plunger 8 and causes each plunger 8 to perform a pumping action. That is, each plunger 8 sucks the working oil into the pump chamber 9 through the suction hole 12 when protruding from the cylinder 7, and discharges the working oil sucked into the pump chamber 9 when retreating from the discharge passage 18.
Will be sent to. And thus each pump room 9
The hydraulic oil sent from the discharge port 18 to the discharge passage 18 opens the check valve 20, flows into the damping pot 19, and is discharged from the damping pot 19 to the discharge pipe outside the housing 1.

Here, the check valve 20 provided in each discharge passage 18 opens when the pressure in the pump chamber 9 reaches a set valve opening pressure higher than the line pressure.
0 always causes an operation delay due to its weight, viscous resistance of hydraulic oil, etc., so that the pressure in the pump chamber 9 rapidly increases (surge pressure is generated) immediately before the check valve 20 is opened.
However, since this plunger pump has the damping structure including the damping chamber 16, the orifice 17, and the elastic member 15, the surge pressure can be effectively reduced as follows.

That is, when the plunger 8 moves from the suction process in which the suction hole 12 is opened near the bottom dead center to the compression process in which the suction hole 12 is closed by the opening edge of the cylinder 7, the pump chamber 9 is hermetically sealed. However, at this time, a pressure difference is generated between the pump chamber 9 and the damping chamber 16 and the working oil slowly flows into the damping chamber 16 through the orifice 17, so that the pump chamber 9
The sudden rise of the internal pressure is suppressed, and accordingly, the surge pressure generated immediately before the check valve 20 is opened is also suppressed to be extremely low. The broken line a in FIG. 3 indicates the pressure in the pump chamber 9 in the plunger pump of this embodiment, and the broken line b.
Shows the pressure in the damping chamber 16 and the solid line c shows the pressure in the pump chamber 9 when the damping structure is not provided. As is apparent from the figure, this plunger pump ensures that the surge pressure can be ensured. In addition, the pulsation of hydraulic pressure immediately after the check valve 20 is opened can be reduced.

Further, as shown in FIG. 3, the discharge process continues until the plunger 8 reaches the top dead center, and when the plunger passes the top dead center, the inside of the pump chamber 9 is sealed and the expansion process is started. The pressure in the pump chamber 9 is about to suddenly decrease, but a pressure difference also occurs between the pump chamber 9 and the damping chamber 16 at this time as well, so that the hydraulic oil gently flows from the damping chamber 16 into the pump chamber 9. . Therefore, at this time, the fall of the pressure in the pump chamber 9 becomes gentle. Then, after this, when the plunger 8 reaches the vicinity of the bottom dead center, the suction hole 12 is opened and the suction process is started. At this time, the pressure in the damping chamber 16 becomes almost the same as the pressure in the suction chamber 6, and the next compression step is prepared.

In the case of this plunger pump, the pump chamber 9
Pressure fluctuations such as surge pressure and hydraulic pressure pulsation are reduced by the flow of hydraulic oil between the damping chamber 16 and the damping chamber 16. However, the flow amount can be easily increased by increasing the capacity of the damping chamber 16 or the filling amount of the elastic member 15. Can be made larger. Further, if the filling amount of the elastic member 15 is increased, it is possible to reliably reduce a large surge pressure without increasing the size of the device.

Further, in the damping structure of this plunger pump, the pressure in the pump chamber 9 does not act directly on the elastic member 15, but the damping chamber 16 communicating with the pump chamber 9 through the orifice 17. Since the internal pressure acts on the plunger 8, the elastic member 15 does not suddenly deform at the beginning of the compression process of the plunger 8 and the rise of the pressure in the pump chamber 9 is not extremely delayed. Therefore, the pump capacity is significantly reduced. Such a problem does not occur.
Further, since the damping structure of the pump does not cause the members to slide with each other, and the pressure in the damping chamber 16 is evenly applied to the entire outer surface of the elastic member 15, the durability of the members is very high, which is advantageous in terms of maintenance. is there. In addition, the elastic member 15
Is formed in a ring shape, the cost can be reduced by using a known O-ring.

In the above, the plunger pump of the type in which the suction hole 12 is provided in the peripheral wall of the plunger 8 and the working oil is sucked into the pump chamber 9 when the suction hole 12 opens in the suction chamber 6 has been described. As shown in FIG. 4, the discharge passage 18 and the suction passage 21 are connected to the bottom of the cylinder 7,
A plunger pump of the type in which a check valve 20 that allows a flow in the discharge direction and a check valve 22 that allows a flow in the suction direction are provided in the passages 18 and 21 may be used.

Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the plunger pump of the first embodiment shown in FIGS. 1 to 3 are designated by the same reference numerals, and the description of the overlapping parts will be partially omitted.

This plunger pump corresponds to the invention of claim 2, and the recess 1 provided at the bottom of the cylinder 1
4 and spring retainer 13 for damping chamber 1
6 is formed, the elastic member 15 is accommodated in the damping chamber 16, and the top portion 13 of the spring retainer 13 is formed.
An orifice 17 that connects the pump chamber 9 and the damping chamber 16 is provided on the end surface of a, and a valve device 23 that opens and closes the orifice 17 is provided in the top portion 13 a of the spring retainer 13.

The valve device 23 is for adjusting the flow start timing of the hydraulic oil between the pump chamber 9 and the damping chamber 16, and the check ball 24 for directly opening and closing the orifice 17 from the inside of the damping chamber 16. A spring 25 for biasing the check ball 24 toward the orifice 17 and a locking plate 26 for locking the end of the spring 25 with the spring retainer 13 are provided. The valve device 23 is provided in the pump chamber 9
When the internal pressure becomes higher than the internal pressure of the damping chamber 16 by the set pressure or more, the check ball 24 opens the orifice 17 to allow the flow of the hydraulic oil from the pump chamber 9 to the damping chamber 16.

Further, in this plunger pump,
When the pressure in the pump chamber 9 becomes lower than the pressure in the damping chamber 16 by a set pressure or more, the spring retainer 13
Is separated from the plug 10 against the force of the spring 11,
A slight gap d is formed between the retainer 13 and the plug 10. In this case, the damping chamber 16 and the pump chamber 9 communicate with each other through the gap d, and the working oil slowly flows from the damping chamber 16 to the pump 9.

With the above-mentioned structure, the plunger pump operates as follows while the plunger 9 shifts from the suction process to the compression, discharge, expansion, and suction processes again. In FIG. 9, the broken line a is the pressure in the pump chamber of the plunger pump of this embodiment, and the broken line b is
Indicates the pressure inside the damping chamber, and the solid line c indicates the pressure inside the pump chamber when there is no damping structure. Hereinafter, description will be made with reference to FIG.

In the inhalation process, as shown in FIG.
The suction hole 12 of the plunger 8 opens into the suction chamber 6 and the working oil is sucked into the pump chamber 9 from the suction chamber 6.

In the subsequent compression step, as shown in FIG. 6, the suction hole 12 of the plunger 8 is closed by the opening edge of the cylinder 7, and the pressure in the pump chamber 9 rises sharply. Then, at this time, when the pressure in the pump chamber 9 becomes higher than the pressure in the damping chamber 16 by the set pressure ΔP ₁ or more, the check ball 24 of the valve device 23 causes the spring 25 to move.
The orifice 17 is opened (e in FIG. 9) against the force of, and the hydraulic oil in the pump chamber 9 slowly flows into the damping chamber 16. Therefore, after the opening of the orifice 17, the rise of the pressure in the pump chamber 9 becomes gentle, and as a result, the surge pressure due to the delay in the operation of the check valve 20 is surely reduced. Since the surge pressure is reduced, the hydraulic pressure pulsation immediately after the check valve 20 is opened does not occur.

When the check valve 20 is opened and the discharge process is started, the pressure in the pump chamber 9 becomes a constant pressure equal to the line pressure, so that the differential pressure between the pump chamber 9 and the damping chamber 16 is constant. As shown in FIG. 7, the check ball 24 of the valve device 23 closes the orifice 17.

Further, when the plunger 8 passes the top dead center and shifts to the expansion step, the pump chamber 9 is hermetically closed and the pressure inside thereof is drastically lowered, as shown in FIG. And
At this time, when the pressure in the pump chamber 9 becomes smaller than the pressure in the damping chamber 16 by the set pressure ΔP ₂ or more, the spring retainer 13 resists the force of the spring 11 and the plug 1
It separates from 0 (f in FIG. 9), and the hydraulic oil in the damping chamber 16 flows into the pump chamber 9 through the gap d formed between the retainer 13 and the plug 10. Therefore, at this time, the pressure in the pump chamber 9 falls slowly, and the pressure in the damping chamber 16 is returned to the initial pressure.

Then, after this, when the plunger 8 moves to the vicinity of the bottom dead center, the suction hole 12 of the plunger 8 opens and the process returns to the suction process again.

In the case of this plunger pump, surge pressure and hydraulic pulsation can be surely reduced by the flow of hydraulic oil between the pump chamber 9 and the damping chamber 16 as in the case of the first embodiment. Since the flow opening timing of the hydraulic oil between the pump chamber 9 and the damping chamber 16 can be freely set and adjusted by changing the setting of the valve opening pressure of the valve device 23, a more desirable pressure in the pump chamber 9 can be obtained. The characteristics can be easily obtained. For example, as shown in FIG. 9, if the flow of hydraulic oil is started in the latter half of the compression process, the pressure in the pump chamber 9 rises faster in the first half of the compression process, and the decrease in pump capacity is further reduced. It becomes possible.

The damping structure of the second embodiment is adopted in the plunger pump of the type (the type shown in FIG. 4) in which the discharge passage and the suction passage are communicated with the pump chamber and each passage is provided with a check valve. It is also possible.

[0036]

As described above, according to the invention of claim 1, the damping chamber facing the pump chamber is provided, the damping chamber and the pump chamber are communicated with each other by the orifice, and the elastic member capable of changing the volume is housed in the damping chamber. However, when a pressure fluctuation in the pump chamber occurs, the flow of hydraulic oil that suppresses the pressure fluctuation in the pump chamber is generated between the pump chamber and the damping chamber, so surge pressure or hydraulic pulsation is applied to this hydraulic oil. Can be reliably reduced by the flow of. Furthermore, since the flow rate of the hydraulic oil between the pump chamber and the damping chamber can be increased by increasing the amount of the elastic member accommodated in the damping chamber, a large surge pressure can be achieved without increasing the size of the device. Can be surely reduced. Further, according to the present invention, since the hydraulic oil basically flows between the two chambers due to the pressure difference between the pump chamber and the damping chamber, the rise of the pressure in the pump chamber may be significantly delayed at the beginning of the compression process of the plunger. Without
Therefore, the pump capacity is not significantly reduced. Furthermore, in the case of the present invention, there is no member that slides in the damping chamber when the pressure fluctuation is attenuated, and the pressure that deforms the elastic member is not locally applied to the elastic member but is evenly distributed over the entire region via the hydraulic oil. Since it is added, there is an advantage that the durability is high.

According to a second aspect of the present invention, a valve device is provided which opens the orifice when the pressure difference between the pump chamber and the damping chamber exceeds a set pressure, and the opening pressure of the valve device is appropriately changed so that the pump chamber and the damping chamber are opened. Since the flow start timing of the hydraulic oil can be adjusted during this period, more optimal pressure characteristics can be easily obtained.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing the same embodiment.

FIG. 3 is a graph showing the characteristics of the plunger pump of the same embodiment.

FIG. 4 is a sectional view showing a modified example of the same embodiment.

FIG. 5 is an enlarged cross-sectional view showing the main parts of the second embodiment of the present invention.

FIG. 6 is an enlarged cross-sectional view showing the same embodiment.

FIG. 7 is an enlarged cross-sectional view showing the same embodiment.

FIG. 8 is an enlarged cross-sectional view showing the same embodiment.

FIG. 9 is a graph showing characteristics of the plunger pump of the same embodiment.

[Explanation of symbols]

 7 ... Cylinder, 8 ... Plunger, 9 ... Pump chamber, 15 ... Elastic member, 16 ... Damping chamber, 17 ... Orifice, 18 ... Discharge passage, 20 ... Check valve, 23 ... Valve device.

Claims (2)

[Claims] 1. A pump chamber is formed by a cylinder and a plunger fitted to the cylinder, and the working oil sucked into the pump chamber by the reciprocating motion of the plunger is discharged into a discharge passage having a check valve. The plunger pump is characterized in that a damping chamber facing the pump chamber is provided, the damping chamber and the pump chamber are communicated with each other by an orifice, and an elastic member capable of changing the volume is housed in the damping chamber. 2. The plunger pump according to claim 1, further comprising a valve device that opens the orifice when the differential pressure between the pump chamber and the damping chamber becomes equal to or higher than a set pressure.