JP2002106479A - Variable displacement gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a mechanism capable of changing the discharge flow in proportion to the load with simple structure in a gear pump. SOLUTION: A drive gear 12 and a driven gear engaged with the drive gear 12 are accommodated in the housing H of casings 10, 11. Sidepieces of the drive gear 12 and the driven gear are in touch with a movable side plate 14 and formed a pressure control chamber 17 at the back surface of the movable side plate 14. The drive gear is rotated by drive source connected to coupling 18 and sucks in oil from suction opening 19 and delivers it from delivery opening 20. During on load operation, delivery pressure is led to a pressure control chamber 17 by the pressure control measure 22 and the pressure is increased in the pressure control chamber 17 and pressed the movable side plate 14 to the drive gear 12 and the driven gear to increase seal effect and improve the volumetric efficiency. During unload operation, the pressure control chamber 17 is connected to the suction side for decreasing the pressure and the movable side plate 14 is set back to make a space between the drive gear 12 and the driven gear to decrease the delivery rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement gear pump that can be used as a hydraulic pressure source for a hydraulic system such as a vehicle hydraulic suspension control device.

[0002]

2. Description of the Related Art FIG.
This will be described with reference to FIGS. The gear pump 1 is a circumscribed gear pump, and includes a pair of drive gears 3 and driven gears 4 that rotate while meshing with each other in casings 2A and 2B. The casings 2A and 2B are provided with a suction port 5 and a discharge port 6 on both sides of the meshing portion between the drive gear 3 and the driven gear 4. The shaft portion 7 of the drive gear 3 is provided with a joint 8 for connecting a drive source (not shown) such as an electric motor. Here, the joint 8 is chamfered to engage a floating cam (not shown) of the Oldham coupling.

[0003] With this configuration, a driving gear is driven by a driving source.
When 3 is rotated, the driven gear 4 meshing with it is also rotated,
The oil liquid that has entered the tooth spaces of the drive gear 3 and the driven gear 4 at the suction port 5 is transferred along the inner surface of the casing 2A,
It is sent to the discharge port 6 side, and is pressurized and discharged. In general, gear pumps have a simple structure, few parts, small size,
Since it has the advantages of being lightweight, inexpensive, and less susceptible to foreign matter in oil, it is widely used in hydraulic equipment for vehicles and the like.

Further, in order to reduce leakage of the oil liquid from the side surfaces of the driving gear 3 and the driven gear 4, a movable side plate is provided in contact with the side surfaces of these gears, and discharge pressure is introduced to the back side of the movable side plate. A movable side plate type gear pump is known in which the movable side plate is pressed against the side surfaces of the drive gear 3 and the driven gear 4 to enhance the sealing property of the side surfaces of the gears and enable application to a high-pressure system. .

[0005]

However, the conventional gear pump has the following problems. The theoretical torque T _th [Nm] required to rotate the drive gear is calculated based on the theoretical discharge amount q [ml / rev] and the discharge pressure P [M
Pa] is obtained from the following equation. T _th = P × q / 2π [Nm] The driving torque T actually required to drive the driving gear is obtained by the following equation as the mechanical efficiency η _m . T = T _th / η _m [Nm] Therefore, when the theoretical discharge amount q is determined by the shape of the drive gear and the driven gear, the drive torque T becomes the discharge pressure P
Will be approximately proportional to

On the other hand, the theoretical discharge amount per unit time Q _th [l / m
in] can be calculated from the theoretical discharge amount q [ml / rev] per rotation of the drive gear and the rotation speed N [rpm] by the following equation. Q _th = q × N / 1000 [l / min] Then, the actual discharge amount Q [l / min] is obtained by the following equation as the volume efficiency η _v . _{Q = Q th / η v [} l / min] Thus, the discharge quantity Q, it is seen to be determined by the rotational speed N.

Here, as an example, a case is considered in which a gear pump is used as a hydraulic source of a hydraulic suspension device of an automobile and a pump drive source is a gasoline engine of the automobile. In general, the number of revolutions of a gasoline engine of an automobile ranges from about 500 to 700 rpm during idling to a maximum
The fluctuation range is as large as about 000 rpm, and almost no output torque can be obtained during idling.

Therefore, regardless of the discharge amount Q, the discharge pressure P
With the above-described characteristics of the gear pump in which the driving torque of the gear is determined, an unloader is required to reduce the engine load during idling as much as possible.

Further, when the rated discharge amount of the gear pump is determined so that the required oil amount can be obtained at a normal rotation speed of 1000 to 3000 rpm, the discharge amount Q becomes more than twice the required amount near the maximum rotation speed, and Since the loss becomes excessive, the pump needs to be unloaded. At this time, if an attempt is made to use a normal unloader, it is necessary to make the opening area of the valve means used as the unloader and the flow passage area of the pipe of the unloader sufficiently large in order to reduce pressure loss, and a large space is required. Problem arises.

The present invention has been made in view of the above points, and has as its object to provide a small-sized variable displacement gear pump having a simple structure capable of changing the discharge capacity.

[0011]

According to a first aspect of the present invention, there is provided a variable displacement gear pump according to the first aspect of the present invention, wherein a casing includes a driving gear and a driven gear meshing with the driving gear. A movable side plate that seals a side surface portion of the drive gear and the driven gear is provided so as to be able to move forward and backward with respect to the drive gear and the driven gear, and control means for moving the movable side plate forward and backward is provided. I do. With this configuration, the control means presses the movable side plate against the side surfaces of the drive gear and the driven gear, so that the sealing performance can be increased and the volume efficiency can be increased. By forming a gap between the driving gear and the driven gear, the discharge amount can be reduced to perform the unload operation. Further, in the variable displacement gear pump according to the second aspect of the present invention, in the configuration of the first aspect, the control unit is formed on a side of the movable side plate opposite to a surface that seals a side surface of the drive gear and the driven gear. The movable side plate is moved forward and backward by the pressure in the control pressure chamber. With this configuration, the discharge amount can be controlled by moving the movable side plate forward and backward by adjusting the pressure of the control pressure chamber.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. A first embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, the variable displacement gear pump 9 of the first embodiment is a circumscribed gear pump, and a pair of gear pumps that rotate while meshing with each other in a housing H formed by coupling casings 10, 11. The driving gear 12 and the driven gear 13 are accommodated. One side surface of the drive gear 12 and the driven gear 13 is sealed by an inner surface of the fixed casing 10, and the other side surface is a movable side plate 14 slidably fitted to the casing 11. Sealed by 15.

As shown in FIG. 3, the movable side plates 14 and 15 have large-diameter portions 14a and 15a fitted into the casing 10 and small-diameter portions 14a fitted to the casing 11 via a seal ring 16, respectively.
It is formed in a stepped substantially cylindrical shape having b and 15b, and is slidably guided in the housing H of the casings 10 and 11 along the axial direction. Small diameter parts 14b, 15b of large diameter parts 14a, 15a
An annular control pressure chamber 17 (control means) is formed between the side end and the end face of the casing 11. The drive gear 12 and the driven gear 13 are connected to shafts 12a and 13a on one end (the shaft 1 of the drive gear 12).
(Only 2a is shown) is rotatably supported by the casing 10, and the shaft portions 12b and 13b at the other end are inserted through the movable side plates 14 and 15 and rotatably supported.

One shaft portion 12b of the drive gear 12 is
A joint 18 is provided at the tip end of the joint 18 which extends to the outside from the outside and is connected to a driving source (not shown). In this embodiment, the joint 18 is chamfered to engage a floating cam (not shown) of the Oldham coupling.

In the conventional movable side plate for obtaining a high pressure by enhancing the sealing property of the gear side surface, the amount of movement in the axial direction is as follows.
In contrast to the setting of about 0.05 mm, the movable side plates 14 and 15 of the present embodiment have a sufficiently large axial dimension,
By disposing the seal ring 16 near the tip of the small diameter portions 14b and 15b, it is possible to move 0.1 mm or more in the axial direction, suppress the inclination of the movable side plate in the axial direction, and increase the seal length of the sliding part. To prevent oil leakage.

The casings 10 and 11 are provided with a suction port 19 in front of the rotating direction of these gears with a meshing portion between the drive gear 12 and the driven gear 13 therebetween, and a discharge port 20 behind. Is provided. In the control pressure chamber 17, movable side plates 14, 15
A wave washer 21 that presses the side surfaces of the driving gear 12 and the driven gear 13 is provided. Pressure control means 22 is connected to the control pressure chamber 17 (see FIG. 1). The pressure control means 22 can externally control (increase and decrease) the pressure in the control pressure chamber 17 .For example, during on-load operation, the control pressure chamber 17 is introduced by introducing the discharge pressure on the discharge port 20 side. During the unload operation, the control pressure chamber 17 may be connected to the suction port 19 side to increase the pressure and reduce the pressure by using an electromagnetic switching valve.

The operation of the embodiment constructed as above will be described below. When the drive gear 12 is rotated by the drive source, the driven gear 13 meshing with the drive gear 12 is also rotated, and the suction port is rotated.
In 19, the oil liquid that has entered the tooth grooves of the drive gear 12 and the driven gear 13 is transferred along the inner surface of the housing H, sent to the discharge port 20 side, and is pressurized and discharged.

At this time, during normal operation (on-road operation)
In addition, by increasing the pressure of the control pressure chamber 17 by the pressure control means 22 and pressing the movable side wall 14 against the side surfaces of the drive gear 12 and the driven gear 13, the sealing properties of the side surfaces of the drive gear 12 and the driven gear 13 are improved. , The leakage of the oil liquid can be prevented even under high pressure, the volumetric efficiency can be increased, and application to a high-pressure system can be made possible.

In the unloading operation, the control pressure chamber 17 is depressurized by the pressure control means 22, and the movable side walls 14, 15 are retracted by the pressure of the oil liquid transferred by the drive gear 12 and the driven gear 13. . As a result, the pressure on the discharge side is short-circuited to the suction side, the discharge amount is reduced, and the load is reduced. In this case, the movable side walls 14 and 15 are driven by the drive gear 12 and the driven gear 12 only by the spring force of the wave washer 21.
As a result, the discharge pressure during the unload operation can be set freely according to the spring force of the wave washer 21.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Note that, in the first embodiment, similar parts are denoted by the same reference numerals, and only different parts will be described in detail.

As shown in FIG. 4, the gear pump 23 according to the second embodiment is driven by a timing belt (not shown) of the engine. , 15 are disposed on the opposite side of the casing 10, and instead of the wave washers, the coil springs 24, 25 provided in the casing 10 are brought into contact with the ends of the small diameter portions 14b, 15b, so that the movable side plate 14, 15 is pressed against the driving gear 12 and the driven gear 13. The shaft 26 of the drive gear 12 is supported by the casing 11 by a ball bearing 27, and a pulley 28 is attached to a distal end of the shaft 26 by a nut 29 and a key 30. The ball bearing 27 receives a radial load applied to the drive shaft 26 from the timing belt via the pulley 28. Further, the drive gear 12 and the shaft 26 are divided,
A key (not shown) is used to transmit only the rotational force to each other, so that the thrust load acting on the pulley 19 is not transmitted to the drive gear 12. In the figure,
Reference numeral 31 indicates an oil seal.

With this configuration, the gear pump 23 can be operated by driving the drive gear 12 via the timing belt by the crankshaft (not shown) of the engine. Similarly, normal operation and unload operation can be performed by the pressure control means 22.

Next, an on-vehicle hydraulic system using the gear pump 23 will be described with reference to FIG. As shown in FIG. 5, in the hydraulic system 32, the drive gear 12 of the gear pump 23 is
Is driven by an engine 33, a suction port 19 is connected to a reservoir 34, and a discharge port 20 is connected to a hydraulic device 37 via a filter 35 and a check valve 36.
The oil cooler 38 is connected to the reservoir 34. As the hydraulic device 37, a system in which the amount of consumed fluid fluctuates greatly, such as a hydraulic suspension device (active suspension device) and a power steering device, can be connected. Discharge side of gear pump 23 (downstream of filter 35)
Is connected to the reservoir 34 via the relief valve 39 (oil cooler 3
8 upstream). An accumulator 40 and a pressure sensor 41 are provided on the discharge side of the gear pump 23 (downstream of the check valve 36).

The control pressure chamber 17 of the gear pump 23 is connected via a throttle 42 to the discharge side of the gear pump 23 (downstream of the filter 35). Further, the control pressure chamber 17 is connected to the reservoir 34 side (upstream of the oil cooler 38) via a normally open electromagnetic on-off valve 43.

With this configuration, the on-load /
Controls unloading. When starting the engine 33,
The electromagnetic on-off valve 43 is de-energized (opened), the control chamber 17 is connected to the reservoir 34 side to reduce the pressure, and the gear pump 23 is brought into the unloaded state. Similarly, the engine 33 is set in the unloading state during idling. In this state, the discharge pressure of the gear pump 23 is kept at a low pressure set by the spring force of the springs 24 and 25, for example, about 0.1 Mpa, and the load on the engine 33 can be reduced.

If the pressure of the accumulator 40 detected by the pressure sensor 41 is equal to or less than a predetermined lower limit, the engine
When the rotation speed of 33 reaches the normal rotation speed, for example, 1000 rpm,
The electromagnetic on-off valve 43 is energized and the electromagnetic on-off valve 43 is gradually closed. Thereby, the discharge pressure of the gear pump 23 is introduced into the control pressure chamber 17 through the throttle 42, the control pressure chamber 17 is increased in pressure, and the movable side plates 14, 15 are pressed against the drive gear 12 and the driven gear 13, The discharge pressure gradually increases. Due to the increase in the discharge pressure, the oil liquid is supplied to the accumulator 40, and when the pressure of the accumulator 40 reaches a predetermined upper limit set value, the power supply to the electromagnetic on-off valve 43 is stopped, and the electromagnetic on-off valve 43 is gently moved. open. As a result, the control pressure chamber 17 is gradually reduced in pressure to bring it into the unloaded state. In the on-road state,
When the engine speed falls below the normal speed, the power supply to the electromagnetic on-off valve 43 is stopped, the electromagnetic on-off valve 43 is gradually opened, and the state gradually shifts to the unload state.

In this way, the movable side plates 14, 15 can be changed according to the load state of the engine and the accumulated pressure state of the accumulator 40.
By switching the on-load / unload state by moving the hydraulic pressure, stable hydraulic pressure can be supplied to the hydraulic device 37, and high hydraulic pressure can be obtained while reducing power loss. At this time, by gradually opening and closing the electromagnetic on-off valve 43 and gently switching the on-load / unload operation, a sudden change in the engine load is prevented,
The engine 33 can be operated smoothly by suppressing the occurrence of knocking and the like.

[0028]

As described above in detail, according to the variable displacement gear pump according to the first aspect of the present invention, the control means
By pressing the movable side plate against the side surfaces of the drive gear and the driven gear, the sealing performance can be improved and the volume efficiency can be increased, and the movable side plate is retracted to form a gap between the drive gear and the driven gear. By doing so, it is possible to perform the unload operation by reducing the discharge pressure and the discharge amount.
This makes it possible to provide a small variable displacement gear pump with a simple structure. Further, according to the variable displacement gear pump according to the second aspect of the present invention, the discharge amount can be controlled by moving the movable side plate forward and backward by adjusting the pressure of the control pressure chamber.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a variable displacement gear pump according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the device of FIG. 1 taken along line CC.

FIG. 3 is a front view of a movable side plate of the apparatus of FIG. 1;

FIG. 4 is a cross-sectional view of a variable displacement gear pump according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a vehicle-mounted hydraulic system using the variable displacement gear pump of FIG.

FIG. 6 is a front vertical sectional view of a conventional gear pump.

FIG. 7 is a longitudinal sectional view taken along line AA of FIG. 6;

FIG. 8 is a longitudinal sectional view taken along line BB of FIG. 6;

[Explanation of symbols]

 9,23 Variable gear pump 12 Drive gear 13 Follower gear 10,11 Casing 14,15 Movable side plate 17 Control means (control pressure chamber)

Claims (2)

[Claims] 1. A gear pump in which a drive gear and a driven gear that meshes with the drive gear are housed in a casing, a movable side plate that seals side surfaces of the drive gear and the driven gear is provided with respect to the drive gear and the driven gear. A variable displacement gear pump, further comprising control means for moving the movable side plate forward and backward. 2. The control means includes a control pressure chamber formed on a side of the movable side plate opposite to a surface that seals a side surface of the drive gear and a driven gear, and the movable pressure is controlled by a pressure in the control pressure chamber. 2. The variable displacement gear pump according to claim 1, wherein the side plate is moved forward and backward.