JP2672127B2 - Radial piston pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a fixed cylinder type radial piston pump.

(Prior Art) A fixed cylinder type radial piston pump is conventionally configured as shown in FIG. 3, for example. That is, the eccentric cam 3 fixed to the rotary shaft 2 is housed inside the cam chamber 4 formed in the pump body 1, and a plurality of pistons 6 driven by the eccentric cam 3 are radially formed in the pump body 1. Each of the piston chambers 5 is slidably inserted.

The cam chamber 4 is sealed by a front cover 15 fixed to the pump body 1, and the rotating shaft 2 is attached to the front cover 15.
And the pump body 1 are rotatably supported by bearing metals 16 respectively. A rear cover 17 is fixed to the opposite end surface of the pump body 1. Reference numeral 18 is a seal that is in sliding contact with the rotary shaft 2.

The cam chamber 4 communicates with a reservoir (not shown) through a plurality of chokes 24 formed in the front cover 15, a suction passage 23, and a suction port 22 opening to the outside, and is constantly filled with hydraulic oil.

The piston 6 is formed in a cylindrical shape with a bottom, and the bottom portion is formed in the cam chamber 4
The inside end projects into the piston chamber 5 at the opposite end. The piston chamber 5 is sealed by the cap 7, and the cap 7
A spring 8 is interposed between the guide 14 and the piston 6 which are supported by the inside of the piston chamber 5. The bottom of the piston 6 is held in sliding contact with the eccentric cam 3 by this spring 8. A suction port 13 communicating with the piston chamber 5 is formed on the side surface of the piston 6 near the bottom.

The suction port 13 opens in the cam chamber 4 in the process in which the piston 6 urged by the spring 8 follows the eccentric cam 3 and projects into the cam chamber 4, thereby expanding the hydraulic oil in the cam chamber 4. Inhale to 5. Further, the piston 6 is slidably contacted with the pump body 1 and closed while the piston 6 slides on the eccentric cam 3 and slides in the compression direction. Even after the suction port 13 is submerged in the pump body 1, the piston 6 slides further toward the compression side to reduce the piston chamber 5 and pressurizes the internal working oil, while discharging from the discharge port 10 through the check valve 9. Discharge to the passage 11. In this way, the hydraulic oil discharged from each piston chamber 5 to the discharge passage 11 is supplied to the outside from a discharge port (not shown) that is open to the outside of the pump body 1.

The discharge flow rate of this pump increases with the number of rotations of the eccentric cam 3 in the low rotation range, but in the high rotation range, the number of discharges per unit time increases, while the suction time per cycle causes the hydraulic oil to flow in the piston chamber 5. Since it is less than the time required for filling, the suction amount per cycle decreases in proportion to the suction time, and naturally the discharge amount per cycle also decreases. Therefore, by canceling these, the discharge flow rate of the pump becomes constant regardless of the number of rotations in the rotation range above a certain level.

(Problem of the invention) By the way, in the case of this pump, since the flow rate level (control flow rate) after constant cannot be changed arbitrarily, when it is desired to control the flow rate, for example, the discharge side of the pump is connected to the reservoir. The flow rate was reduced to the required flow rate by connecting a relief valve that recirculates and recirculating a part of the discharged oil to the reservoir. However, even in that case, the discharge flow rate of the pump itself does not change, and as a result, the operating energy of the pump is wastefully consumed for the amount of reflux to the reservoir.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radial piston pump capable of changing a control flow rate according to usage conditions in order to solve the above problems.

(Means for Solving the Problem) According to the present invention, an eccentric cam formed on a rotary shaft is rotatably housed in a cam chamber of a pump body, and a plurality of pistons driven by the eccentric cam are centered around the rotary shaft. And slidably inserted into piston chambers formed radially in the pump body, and the pump body is provided with a passage for guiding the working oil from the suction passage to the cam chamber, and a suction port for sucking the working oil into the piston chamber,
In a radial piston pump having a discharge port for discharging this hydraulic oil pressurized in the piston chamber to the discharge passage,
A cylindrical spool that fits the outer peripheral portion to the inner wall of the cam chamber and slides in the rotation axis direction is provided close to the passage, and this spool is moved according to the pilot pressure,
The flow rate of hydraulic oil flowing through the passage was changed.

(Operation) When the variable throttle is throttled via the pilot pressure, the resistance of the working oil flowing into the cam chamber increases, and the pressure in the cam chamber decreases.
Along with this, the pressure difference between the piston chamber and the cam chamber, which expands due to the expansion operation of the piston, becomes smaller, and the suction amount of the hydraulic oil into the piston chamber decreases. For this reason, the pump discharge amount is stabilized at a low level compared with the case where the variable throttle is opened with respect to the increase in the rotation speed.

(Embodiment) An embodiment of the present invention is shown in FIGS. 1 and 2. The same components as those of the conventional example are designated by the same reference numerals and detailed description thereof will be omitted.

In FIG. 1, 1 is a pump body, 2 is a rotating shaft, 3
Is an eccentric cam fixed to the rotary shaft 2. The eccentric cam 3 is housed in a cam chamber 4 formed in the pump body 1, and the cam chamber 4
Is sealed by the front cover 15. Piston chambers 5 are radially formed outside the cam chamber 4 of the pump body 1, and pistons 5 are housed in the respective piston chambers 5 with their bottoms slidably contacting the eccentric cams 3. The opposite end of the piston 6 opens into the piston chamber 5 which is sealed by the cap 7.

The side of the piston 6 has a suction port communicating with the piston chamber 5.
13 opens. The piston chamber 5 also communicates with a discharge passage 11 via a discharge port 10 and a check valve 9, and this discharge passage 11 communicates with a discharge port (not shown) that opens to the pump body 1.

The hydraulic oil is supplied to the cam chamber 4 through a suction port 22, a suction passage 23 and a choke 24 formed in the front cover 15, and a spool 25 as a variable throttle mechanism is provided at the outlet of the choke 24.

The spool 25 is formed in a cylindrical shape, and the outer peripheral portion of the spool 25 is slidably fitted in the cam chamber 4 in the direction of the rotary shaft 2. In addition, a concave portion that guides the hydraulic oil from the choke 24 to the cam chamber 4 is provided on the inner peripheral portion.
With 25A. A spring 26 interposed between the spool 25 and the front cover 15 urges the recess 25A in a direction away from the front surface of the choke 24, while the spool 25 is moved in the opposite direction, that is, the recess 25A is moved toward the choke 24. A pilot chamber 27 that drives to the front is formed between the spool 25 and the pump body 1. In the pump body 1, a pilot passage 28 for guiding pilot pressure to the pilot chamber 27,
A pilot port 29 communicating with the pilot passage 28 is formed.

 Next, the operation will be described.

When the rotary shaft 2 is driven to rotate, the eccentric cam 3 rotates integrally, and the piston 6 driven by the eccentric cam 3 sucks the working oil in the cam chamber 4 into the piston chamber 5 every time the eccentric cam 3 makes one revolution. It is pressurized and discharged from the discharge port 10 to the discharge passage 11 via the check valve 9. The hydraulic oil discharged from each piston chamber 5 to the discharge passage 11 is supplied to the outside through the discharge port.

The discharge flow rate of this discharge port increases with the rotation speed of the eccentric cam 3 similarly to the conventional example, and becomes constant at a certain rotation speed to become the control flow rate. In this pump, the pilot pressure to the pilot chamber 27 The control flow rate can be arbitrarily changed by changing the position of the spool 25 by the supply.

That is, when the pilot pressure in the pilot chamber 27 is zero, the spool 25 is urged by the spring 26 to
It is held in the position shown. In this state, the recess 25A is displaced laterally from the front surface of the choke 24, and the cross-sectional area of the working oil flowing between the choke 24 and the cam chamber 4 is narrowed down. The hydraulic oil flowing into the valve causes a large pressure loss as it passes through the throttle, and the cam chamber 4 has a low pressure. As a result, the pressure difference between the piston chamber 5 and the cam chamber 4, which expands as the piston 6 slides, decreases, and the amount of hydraulic oil sucked into the piston chamber 5 from the suction port 13 also decreases. Therefore, the discharge flow rate of the pump becomes constant at a low level as shown in the graph of FIG.

On the other hand, when the pilot pressure is supplied to the pilot chamber 27 and the spool 25 is moved to the left side of the drawing against the spring 26 so that the recess 25A is located in front of the choke 24, the choke 24 and the cam chamber 4 are separated from each other. The cross-sectional area of the flow path between them gradually increases, and finally there is virtually no restriction. As a result, the pressure in the cam chamber 4 is less likely to decrease as compared with when the circulation cross-sectional area of the hydraulic oil is reduced by the spool 25, and the maximum value of the control flow rate becomes a large value as in the conventional example.

In this way, since the control flow rate changes in accordance with the pilot pressure supplied to the pilot chamber 27, by changing the pilot pressure according to the required discharge flow rate, it is possible to control the flow rate on the downstream side of the pump. A mechanism for returning a part of the discharged oil to the reservoir is unnecessary, and the pump can be operated without waste.

As described above, according to the present invention, the eccentric cam formed on the rotary shaft is rotatably housed in the cam chamber of the pump body, and the plurality of pistons driven by the eccentric cam are centered on the rotary shaft. The piston body is slidably inserted into the piston chamber that is formed radially, and the passage that guides the working oil from the suction passage to the cam chamber is provided in the pump body.The suction port that sucks the working oil into the piston chamber and the piston chamber In a radial piston pump having a discharge port for discharging this pressurized hydraulic oil to a discharge passage, a cylindrical spool that slides in a rotation axis direction by fitting an outer peripheral portion to an inner wall of a cam chamber is used as the passage. Since the spool is moved in accordance with the pilot pressure to change the flow rate of the hydraulic oil flowing through the passage, the resulting change in the pressure in the cam chamber causes the pump control flow to change. The amount can be changed arbitrarily. Therefore, the flow rate can be controlled without providing a flow rate control mechanism on the downstream side of the pump, and the operating energy of the pump can be saved. Since the spool serving as the variable throttle is provided in the cam chamber, the pump can be made compact and the structure can be simplified.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a radial piston pump showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the discharge flow rate and the rotational speed. Further, FIG. 3 is a vertical cross-sectional view of a radial piston pump showing a conventional example, and FIG. 1 ... Pump body, 2 ... Rotary shaft, 3 ... Eccentric cam,
4 ... Cam chamber, 5 ... Piston chamber, 6 ... Piston, 9
...... Check valve, 10 ... Discharge port, 11 ... Discharge passage, 13 ...
… Suction port, 15 …… Front cover, 22 …… Suction port,
23 …… Suction passage, 24 …… Choke, 25 …… Spool, 25
A: recess, 27: pilot room.

Claims (1)

(57) [Claims] 1. An eccentric cam formed on a rotary shaft is rotatably housed in a cam chamber of a pump body, and a plurality of pistons driven by the eccentric cam are radially formed on the pump body around the rotary shaft. The pump body is provided with passages for slidably inserting the piston chambers to guide the working oil from the suction passages to the cam chambers, and a suction port for sucking the working oil into the piston chambers.
In a radial piston pump having a discharge port for discharging this hydraulic oil pressurized in the piston chamber to the discharge passage,
A cylindrical spool that fits the outer peripheral portion to the inner wall of the cam chamber and slides in the rotation axis direction is provided close to the passage, and this spool is moved according to the pilot pressure,
A radial piston pump characterized by changing the flow rate of hydraulic oil flowing through the passage.