JPH09236077A - Opposed piston pump - Google Patents

Abstract

(57) Abstract: An opposed type in which a pair of opposed pistons for increasing and decreasing the volumes of two pump chambers respectively provided in two independent brake systems in a brake device are reciprocally moved by one motor. In a piston pump, the total length of a pair of opposed pistons is shortened. SOLUTION: Two pistons 304 that respectively increase and decrease the volumes of two pump chambers 312 are united to form one united piston 314, and the united piston is formed in a recess 316 formed in an intermediate portion thereof. , Motor 1
The eccentric cam 306 rotated by 52 is engaged, and the eccentric cam forces the reciprocating motion of the united piston. It suffices to secure the distance between the support points at both ends of the housing with respect to only one combined piston, and the length of the pair of pistons as a whole becomes shorter than when two pistons are fitted into the housing independently of each other. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opposed piston pump provided with a pair of opposed pistons,
In particular, the present invention relates to a technique for downsizing the pump and simplifying the structure.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 4-342648 discloses 2
It is described that each pump is operated by one motor, and an opposed piston pump is already known as one of the technologies. This opposed piston pump is generally (a) a housing, (b) an eccentric rotating member that eccentrically rotates with respect to an axis in a space inside the housing, and (c) the eccentricity on a straight line perpendicular to the axis. A pair of pistons slidably fitted in the housing in a state of facing each other with the rotary member sandwiched therebetween, and (d) a pair of independent pistons formed between the pair of pistons and the housing. And a pump chamber.

In this opposed piston pump, conventionally, a pair of pistons are independent from each other, and the pistons are slidably fitted in the housing independently of each other. Each piston is engaged with the eccentric rotation member by the eccentric rotation member in a state in which each piston performs a forward movement that reduces the volume of each pump chamber but does not perform a backward movement that increases the volume. The return movement of each piston is performed by the return spring arranged in each pump chamber.

Specifically, in the conventional opposed piston pump, as shown in FIG.
Each piston 504 is moved to each pump chamber 50 by an eccentric cam 502 as an eccentric rotation member which is rotated by 00.
6, the return spring 508 is arranged in each pump chamber 506, and the elastic force of the return spring 508 causes each piston 504 to increase the volume of each pump chamber 506.

[0005]

When designing a piston pump, the piston is not twisted in the cylinder bore of the housing during reciprocating movement of the piston.
Care is taken to ensure reliability against sliding of the piston. If the piston may be twisted in the cylinder bore, the piston may locally come into strong contact with the cylinder bore at the circumferential edge of the end face of the piston, leading to premature wear of the cylinder bore or seizure of the piston. It is strong, for example, when the housing is made of a material based on a relatively soft material, such as aluminum. Specifically, during rotation of the eccentric cam, the eccentric cam shifts from the center axis of the piston (is set) and comes into contact with the end surface of the piston, so that the piston is locally supported in two points in the cylinder bore. Therefore, the distance between the two support points, which is the distance between the two points, is designed to be equal to or greater than an empirically determined value according to the diameter of each piston.

On the other hand, in the conventional pump, as described above, since the pair of pistons are fitted into the housing independently of each other, as shown by points A and B in FIG. It is necessary to individually secure the distance between the support points on both ends of the piston. Therefore, the conventional pump has a problem that the entire length of the pair of pistons becomes long, which hinders downsizing of the housing.

The conventional pump also has the following problems.

In the conventional pump, as described above,
A return spring is required to cause each piston to perform a returning movement that increases the volume of each pump chamber. Therefore, the conventional pump requires a special space for disposing the return spring in the housing. For example, as shown in FIG. 11, a space is required in which the return spring can exist in the pump chamber even when the volume of the pump chamber is minimum.
Therefore, the conventional pump also has a problem in that the size of the housing is hindered by the presence of the return spring.

Further, in the conventional pump, it is not possible to design the minimum volume of the pump chamber to be smaller than a certain amount due to the presence of the return spring. Therefore, the conventional pump also has a problem that it is difficult to improve the discharge efficiency of the pump.

Under these circumstances, therefore, in both the first and second inventions according to claims 1 and 2, a pair of pistons are united, and not only the forward movement but also the backward movement of the combined pistons are performed. It is an object of the present invention to solve those problems by performing the eccentric rotation member.

[0011]

[Means for Solving the Problem, Operation and Effect of the First Invention] In order to solve the problem, the first invention is directed to an opposed piston pump including the housing, an eccentric rotating member, a pair of pistons and a pair of pump chambers. The pair of pistons is a coalesced piston in which the pair of pistons are relatively immovable in at least the direction of the straight line, and the coalesced piston is provided in the eccentric rotation member at an intermediate portion thereof, by the eccentric rotation member, It is characterized in that the portion of the combined piston that functions as each piston is engaged in a state in which not only the forward movement that reduces the volume of each pump chamber but also the backward movement that increases the volume is performed.

As described above, in the opposed piston pump according to the first aspect of the present invention, one coalescing piston constitutes a pair of pistons, and each piston function portion of the coalescing piston is composed of the eccentric rotating member. Not only the forward movement that reduces the volume of the pump chamber but also the backward movement that increases the volume is performed.

Therefore, according to the first aspect of the present invention, since the pair of pistons are composed of one united piston, it is not necessary to secure the distance between the support points of the two pistons according to the piston diameter. However, it suffices to secure the distance between the support points at both ends according to the piston diameter for only one combined piston, and the combined piston length is the entire pair of pistons in the conventional pump in which the pair of pistons are configured independently of each other. The length is shorter than the length, and the effect that the size of the housing can be easily reduced can be obtained.

Further, according to the first aspect of the present invention, the eccentric rotation member causes the united piston to perform not only the forward movement for reducing the volume of each pump chamber but also the backward movement for increasing the volume thereof. In addition, it is no longer essential to install a return spring in each pump chamber in order to cause each piston to return, and it is possible to easily reduce the number of pump parts and to install a return spring. The existing space can be reduced,
This also brings about the effect that the size of the housing can be reduced.

Further, according to the first aspect of the present invention, it is not indispensable to dispose the return spring in each pump chamber in order to cause each piston to perform the returning movement, so that it is easy to reduce the minimum volume of the hoop chamber. As a result, the effect that the discharge efficiency of the pump can be easily improved is also obtained.

Hereinafter, the first invention will be supplementarily described. [1] The “eccentric rotation member” may be, for example, an eccentric cam type in which a disc rotates eccentrically with respect to the axis or a pin type in which a pin rotates with eccentricity with respect to the axis. [2] The "merged piston" is engaged with the eccentric rotation member, for example, when the eccentric rotation member is an eccentric cam type, a recess is formed in the middle of the merged piston, and the eccentric cam is fitted into the recess. It can be realized by a mode or a mode in which a ring-shaped continuous protrusion or a plurality of independent protrusions are formed in the intermediate portion of the united piston, and the eccentric cam is fitted into the inner space defined by the continuous protrusions or the independent protrusions. If the eccentric rotating member is a pin type, a bottomed or bottomless long hole extending in the direction perpendicular to the center line of the united piston is formed in the middle part of the united piston, and the pin is inserted into the long hole. It can be realized in the form of

[0017]

A second aspect of the present invention is an opposed piston pump according to the first aspect of the present invention, wherein the eccentric rotation member is eccentric with respect to the axis and the disc rotates. It is a cam, and a concave portion is formed in an intermediate portion of the united piston, and the concave portion has (a) a bottom surface portion extending substantially parallel to the straight line, and (b) a straight line from both edges of the bottom surface portion. And a pair of side surfaces extending substantially at right angles to the eccentric cam sandwiching the eccentric cam from both sides thereof and making substantially contact with the cam surface of the eccentric cam. It is characterized in that the eccentric cam causes the united piston to reciprocate.

As described above, in the opposed piston pump according to the second aspect of the present invention, the eccentric rotating member is the eccentric cam, and the recess is formed in the intermediate portion of the united piston, and the eccentric cam is fitted into the recess. By being
The eccentric cam causes the united piston to reciprocate.

Therefore, according to this second invention, the first
In addition to the effects of the invention, the engagement between the united piston and the eccentric cam can be realized with a relatively simple structure, and the structure of the opposed piston pump can be easily simplified.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Some preferred embodiments of the present invention will be listed below in the same expression form as the claims. (1) A brake device for a vehicle, comprising the opposed piston pump according to claim 1 or 2, wherein a plurality of brake cylinders extend independently from each other of two pressurizing chambers of a master cylinder. It has two brake systems leading to each, and (a) a reservoir and (b) the master cylinder or a pressure source other than it and the reservoir and the brake cylinder for each of the brake systems. At least a pressure increasing state is provided in which the brake cylinder is connected to the master cylinder or a pressure source different from it to shut off the reservoir from the reservoir, and a reduced pressure state is connected to the reservoir to shut off from the master cylinder or another pressure source. A solenoid valve device that can be switched to, and (c) a pump that pumps up the brake fluid discharged from the brake cylinder to the reservoir, In addition, the one common to those driving the two pumps in those two braking systems
A braking device comprising two motors, wherein the two pumps and one motor are configured as the opposed piston pump. (2) The brake device for a vehicle according to the embodiment (1), which further comprises, for each of the brake systems, a second reservoir which further extends from a first reservoir as the reservoir and supplies brake fluid to the master cylinder. A brake device having an auxiliary passage leading to. According to this embodiment, when the brake fluid to be pumped up by the pump does not exist in the first reservoir, the brake fluid is replenished from the second reservoir, so that the first reservoir is prevented from becoming a large negative pressure. . (3) The brake device according to the embodiment (2), further comprising a throttle provided in a portion of the auxiliary passage that is common to the two brake systems. According to this embodiment, each pump preferentially pumps the brake fluid from each first reservoir, and the brake fluid from the second reservoir is mainly pumped by each pump when the brake fluid is insufficient in each first reservoir. During pumping up and electro-hydraulic pressure control, the brake fluid in the second reservoir is prevented from being used more than necessary. (4) A brake device for a vehicle comprising the opposed piston pump according to any one of claims 1 or 2 and (1) to (3), which is a master cylinder in a four-wheel vehicle and is independent of each other. Two brake systems that have two pressurizing chambers and extend independently from each other are a front wheel braking system and a rear wheel braking system, and two pumps in these braking systems are common to them. A braking device for a vehicle, which is driven by one motor, and two pumps and one motor are configured as the opposed piston pump. (5) A brake device for a vehicle comprising the opposed piston pump according to any one of claims 1 or 2 and (1) to (3), which is a master cylinder in a four-wheel vehicle and includes two independent cylinders. Two brake systems that have pressure chambers but extend independently of each other from each pressure chamber are diagonally configured.
A pump device for a vehicle, wherein each pump is driven by one motor common to them, and the two pumps and one motor are configured as the opposed piston pump. (6) The vehicle brake device according to the embodiment (5), wherein the left and right front wheels are drive wheels and the left and right rear wheels are non-drive wheels.
Two independent independent master cylinders on a wheeled vehicle
Two brake systems that extend independently from each other in each of the two pressurizing chambers are diagonally configured, and perform antilock control and traction control for the left and right front wheels,
Anti-lock control is performed for the left and right rear wheels, and (a) the rear wheel brake passage branches from the middle of the front wheel brake passage that connects each master cylinder's pressure chamber and the front wheel brake cylinder for each brake system. To the rear wheel brake cylinder, and (b) in the part between the master cylinder and the branch point to the rear wheel brake passage in the front wheel brake passage, in the normal braking state, at least the direction from the master cylinder toward both brake cylinders. Of the brake fluid is blocked, the flow of brake fluid in at least the direction from the master cylinder to both brake cylinders is blocked in the anti-lock control state, and the brake fluid in at least the direction from the brake cylinders to the master cylinder in the traction control state. Flow control device that blocks the flow of A master cylinder cut valve) is provided in the embodiment ", the intermediate valve is provided a solenoid valve of normally open to the rear wheel brake passage (c), (d)
A pressure reducing valve, which is a normally-closed electromagnetic valve, is provided in a reservoir passage extending from a portion of the rear wheel brake passage between the intermediate valve and the rear wheel brake cylinder to reach the reservoir. The brake fluid is supplied from the reservoir to a portion of the wheel brake passage between the branch point from the front wheel brake passage and the intermediate valve or a pump passage to the portion of the front wheel brake passage between the flow control device and the front wheel brake cylinder. A pump for pumping up is provided, (f) a second reservoir for supplying brake fluid to the master cylinder is provided, and (g) an auxiliary passage extending from the second reservoir to the first reservoir as the reservoir is provided, (h) A controller (an example of which is an ECU in an embodiment of the invention described later) operates a pump during vehicle braking to operate an intermediate valve and a pressure reducing valve. Anti-lock control to prevent the left and right front wheels and the left and right rear wheels from locking by controlling the engine, and when the vehicle is operating, the pump is operated to control the intermediate valve and pressure reducing valve, so that the left and right front wheels run idle. A braking device characterized by executing traction control for preventing such a situation. (7) In the brake device according to the embodiment (6), further, in the auxiliary passage, from the second reservoir to the first reservoir in a non-negative pressure state where the reservoir chamber of the first reservoir is not substantially negative pressure.
A brake device, comprising: an inflow control valve that blocks an inflow of brake fluid into a reservoir and allows the inflow in a negative pressure state that is a substantially negative pressure. According to this embodiment, the brake fluid is replenished from the second reservoir only when the brake fluid is insufficient in the first reservoir,
For example, during the traction control, the brake fluid becomes excessive in the first reservoir and the reservoir piston thereof bottoms up, so that the brake fluid cannot be smoothly discharged from the brake cylinder to the first reservoir when the brake cylinder is depressurized. It is possible to avoid the situation where the brake cylinder is not depressurized quickly. (8) In the brake device according to the embodiment (7), the inflow control valve is in a closed state (an example of an inflow blocking state) in the non-negative pressure state, and an open state (an example of an inflow allowable state) in the negative pressure state.
Brake device characterized by being an electromagnetic on-off valve. (9) The brake device according to the embodiment (7), wherein the first reservoir is such that a reservoir piston is fitted in the housing in a substantially airtight and slidable manner to store the reservoir liquid in the housing. A chamber is formed, and when the volume of the reservoir chamber increases from the normal value, the reservoir piston is displaced from the normal position to the volume increasing position, and when the volume decreases from the normal value to the normal position to the volume decreasing position. In the above, the inflow control valve is a pilot type inflow control valve which is operated by the reservoir piston and is in an inflow blocking state when the reservoir piston is in a volume increasing position and is in an inflow allowing state when the reservoir piston is in a volume reducing position. Brake device.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, more specific embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 indicates a master cylinder. The master cylinder 10 is a tandem type in which two independent pressure chambers are arranged in series. The master cylinder 10 is linked to a brake pedal 12 as a brake operating member via a booster (not shown), and liquids of the same height are provided in two pressurizing chambers in response to the driver's depression of the brake pedal 12. Each pressure is mechanically generated. The master cylinder 10 has a reservoir 14. The reservoir 14 stores the brake fluid under atmospheric pressure, and replenishes the master cylinder 10 with the brake fluid as needed. That is, in the present embodiment, the reservoir 14 is an example of the second reservoir.

In one pressurizing chamber of the master cylinder 10,
The brake cylinder 16 of the left front wheel FL which is a driving wheel and the brake cylinder 17 of the right rear wheel RR which is a non-driving wheel are connected to each other, and the brake cylinder 18 of the right front wheel FR which is a driving wheel is connected to the other pressurizing chamber. And the brake cylinder 19 of the left rear wheel RL, which is a non-driving wheel, are connected to each other. That is, in a front-wheel drive four-wheel vehicle,
The two brake systems extending from each pressurizing chamber of the master cylinder 10 are diagonally configured independently of each other. Hereinafter, only one brake system will be described in detail with reference to FIG. 2, and the other brake systems have the same configuration, and thus the description thereof will be omitted. In FIG. 2, the portion surrounded by the larger one of the two dashed-dotted frames corresponds to the portion surrounded by the solid-line frame in FIG.

One pressurizing chamber of the master cylinder 10 is connected to the front wheel brake cylinder 16 by a front wheel brake passage 22. A rear wheel brake passage 24 is branched from the middle of the front wheel brake passage 22, and a rear wheel brake cylinder 17 is connected to the tip thereof.

A master cylinder cut valve 100, which is a solenoid valve as a flow control device, is provided in a portion of the front wheel brake passage 22 closer to the master cylinder 10 than the connection position with the rear wheel brake passage 24. The master cylinder cut valve 100 is open in the normal braking state, and the front wheel brake cylinder 16 and the rear wheel brake cylinder 17 are connected to the master cylinder 10 to allow the master cylinder 10 to increase the pressure of the brake cylinders 16, 17. On the other hand, in the antilock control state and the traction control state, the brake cylinders 16 and 17 are closed from the master cylinder 10 to allow the pumps to be described later to increase the pressure of the brake cylinders 16 and 17.

A return passage 102 is provided in parallel with the master cylinder cut valve 100. The return passage 102 is provided with a check valve 104 that blocks the flow of the brake fluid in the direction from the master cylinder 10 to the brake cylinders 16 and 17, but allows the flow in the opposite direction. This is to quickly return the brake fluid from the brake cylinders 16 and 17 to the master cylinder 10.

An intermediate valve 140, which is a normally open solenoid valve, is provided in the rear wheel brake passage 24. Further, a reservoir passage 142 is connected to a portion of the rear wheel brake passage 24 between the intermediate valve 140 and the rear wheel brake cylinder 17. The reservoir passage 142 is the reservoir 144.
A pressure reducing valve 146, which is a normally-closed electromagnetic valve, is provided in the middle thereof. That is, in the present embodiment, the reservoir 144 is an example of the first reservoir.

Also from the reservoir 144 is the pump passage 1
48 also extends. A pump 150 for pumping the brake fluid from the reservoir 144 is provided in the middle of the pump passage 148. The pump 150 is a piston type and is driven by a motor 152. Details of the configuration of the pump 150 will be described later. The outlet of the brake fluid in the pump passage 148 is the intermediate valve 140 in the rear wheel brake passage 24.
It is connected to the portion closer to the master cylinder 10.
In the pump passage 148, the suction side (low pressure side) of the pump 150 is provided with a suction valve 153a that is a check valve, and the discharge side (high pressure side) is provided with a discharge valve 153b that is a check valve.

A portion of the reservoir passage 142 between the connection position with the rear wheel brake passage 24 and the pressure reducing valve 146 is provided by the return passage 154 between the master cylinder 10 and the master cylinder cut valve 100 of the front wheel brake passage 22. Connected to the part. The return passage 154 is provided with a check valve 156 that blocks the flow of the brake fluid in the direction from the master cylinder 10 to the reservoir passage 142 but allows the flow in the opposite direction. This is to prevent residual pressure from being generated in the rear wheel brake cylinder 17 due to the opening pressure of the first check valve 162 described later.

A parallel circuit of a throttle 157a and a check valve 157b is connected to a portion of the rear wheel brake passage 24 between the connection position with the reservoir passage 142 and the rear wheel brake cylinder 17. The throttle 157a is provided to prevent the pressure reducing speed from becoming excessively high when the rear wheel brake cylinder 17 is pressure-reduced by opening the pressure reducing valve 146. Also, the check valve 157b is a throttle 157a.
This action is invalidated when the pressure of the rear wheel brake cylinder 17 is increased by the master cylinder 10 or the pump 150, and is provided to prevent the pressure increase speed from being limited. The throttle 157a can be configured, for example, by providing a narrow groove along the flow of the brake fluid in a portion of the valve seat, which is one component of the check valve 157a, on which the valve is to be seated.

A proportioning valve (hereinafter referred to simply as "P") is provided at a portion of the rear wheel brake passage 24 between the connection position with the reservoir passage 142 and the rear wheel brake cylinder 17.
158). As is well known, the P valve 158 transmits the input pressure as it is as the output pressure to the rear wheel brake cylinder 17 before the input pressure (master cylinder pressure or pump discharge pressure) reaches the break point pressure. After the input pressure reaches the break point pressure, in order to avoid the rear wheel lock due to the load movement to the front of the vehicle, the rear wheel brake cylinder 17 uses the hydraulic pressure obtained by reducing the input pressure at a constant ratio as the output pressure. introduce.

The pump passage 1 of the rear wheel brake passage 24
A pressure reducing device 160 is provided on the master cylinder 10 side from the connection position with 48.

The reason for providing the decompression device 160 is as follows. That is, in the conventional braking device, even when a load-sensing P-valve is used, especially in a light braking area when the vehicle is loaded and the front wheel braking force and the rear wheel braking force are close to 0 (for example, at the beginning of braking operation). , When braking on a road surface having a low friction coefficient, such as the area before the break point of the load-sensing P valve, the actual distribution line of the braking force is the rear wheel with respect to the ideal distribution line. The braking force deviates slightly to the side where it decreases, and it becomes impossible to sufficiently increase the rear wheel braking force in the region where the rear wheel is not locked. Such a situation is constant at least in the light braking area regardless of whether the actual distribution line is empty or loaded, and the gradient of the actual distribution line in the light braking area is equal to that when the vehicle is empty. It is caused by the fact that the wheel leading lock is set so as not to occur. Therefore, in order to solve such a situation, it is necessary to prepare a plurality of braking force distributions having different characteristics at least in the light braking region and selectively realize them. Therefore, the applicant of the present invention has found that the pump 1 in the antilock control state is
The discharge pressure of 50 is reduced and transmitted to the front wheel brake cylinder 16, the hydraulic pressure of the rear wheel brake cylinder 17 increases relatively more than in the normal braking state, and the rear wheel braking force increases sufficiently quickly in the light braking area. The pressure reducing device 160 is provided in order to shorten the braking distance.

The pressure reducing device 160 has a structure in which the first check valve 162 whose valve opening pressure is not substantially 0 and the second check valve 164 whose valve opening pressure is substantially 0 are opposite to each other and arranged in parallel. It is connected. In the present embodiment, the pump 150 is used as a pressure source in the antilock control state, so that the first
The check valve 162 functions as a check valve that allows the flow of brake fluid in the direction from the pump 150 toward the front wheel brake cylinder 16 at a set valve opening pressure or higher.

Here, the master cylinder 10 and the pump 15
The flow of the brake fluid between 0, the front wheel brake cylinder 16 and the rear wheel brake cylinder 17 will be specifically described.

In the normal braking state, the master cylinder cut valve 100 is in the open state.
The brake fluid from is supplied to the front wheel brake cylinder 16 via the master cylinder cut valve 100, and is also supplied to the rear wheel brake cylinder 17 via the master cylinder cut valve 100 and the second check valve 164. Since the valve opening pressure of the second check valve 164 is substantially 0, the hydraulic pressures of equal height are generated in the front wheel brake cylinder 16 and the rear wheel brake cylinder 17 in the end.

On the other hand, when the pump 150 is operating, the master cylinder cut valve 100 is set to the pump 15
The brake fluid flowing from 0 to the master cylinder 10 is blocked, and the brake fluid discharged from the pump 150 is supplied to the front wheel brake cylinder 16 via the first check valve 162, while the rear wheel is supplied to the rear wheel. It is supplied to the brake cylinder 17 as it is. Since the valve opening pressure of the first check valve 162 is not substantially 0, in the end, the front wheel brake cylinder 16 has the first pressure higher than the hydraulic pressure of the rear wheel brake cylinder 17.
A hydraulic pressure lower by the valve opening pressure of the check valve 162 is generated.

That is, in the normal braking state, the master cylinder 10 functions as a pressure source to generate equal hydraulic pressures in the front wheel brake cylinder 16 and the rear wheel brake cylinder 17, respectively, while the pump 150 operates in the pump operating state. It functions as a pressure source and causes the front wheel brake cylinder 16 to generate a hydraulic pressure lower than that of the rear wheel brake cylinder 17. As a result, the front-rear braking force distribution of the vehicle is optimized, and in the loaded state, the hydraulic pressure of the rear wheel brake cylinder 17, that is, the rear wheel braking force is quickly changed from the light braking area which is an area below the break point of the P valve 158. An (effective) increase is possible and the braking distance is reduced.

As shown in FIG. 2, the reservoir 144 and the reservoir 14 (for the master cylinder 10) are connected to the auxiliary passage 1.
They are connected to each other by 70. Its auxiliary passage 17
At 0, an inflow control valve 172 is provided. The inflow control valve 172 is a pilot type in which the reservoir piston in the reservoir 144 operates as a pilot piston.

In the reservoir 144, as shown in FIG.
A reservoir piston 212 is formed in the housing 200 by fitting the reservoir piston 210 in a substantially airtight and slidable manner so as to form a reservoir chamber 212 containing the brake fluid. The reservoir piston 210 is displaced from the normal position shown in the figure to the volume increasing position when the volume of the reservoir chamber 212 increases from the normal value, and from the normal position to the volume decreasing position when the volume decreases from the normal value. Reservoir piston 21
A spring 216 as an urging means is engaged behind the 0 through a retainer 218, and the elastic force of the spring 216 is applied to the reservoir piston 210. But,
The retainer 218 has the flange portion of the housing 200.
The approach limit to the reservoir chamber 212 is regulated by contacting the stepped portion of the retainer 218, and the retainer 218 is loosely fitted to the reservoir piston 210. Therefore, if the volume of the reservoir chamber 212 decreases, the reservoir piston 210 advances independently while leaving the retainer 218 in the original position, while if the volume of the reservoir chamber 212 increases, the reservoir piston 210 compresses the spring 216 together with the retainer 218. fall back.

On the other hand, the inflow control valve 172, as shown in the figure, cooperates with each other from the reservoir 14 to the reservoir chamber 21.
2 has a valve seat 222 and a valve element 224 that block the flow of the brake fluid in the direction toward 2 but allow the flow in the opposite direction, and the valve element 224 is always provided with springs 226 and 228 as biasing means. The valve seat 222 is urged to be seated on the seat 222. Therefore, the inflow control valve 172 is always in the inflow blocking state that blocks the brake fluid in the reservoir 14 from flowing into the reservoir chamber 212. But,
A pin 230 as a cooperating member is arranged between the valve element 224 and the reservoir piston 210, and when the reservoir piston 210 is in the normal position shown in the drawing, the pin 230 engages the valve element 224 and the reservoir piston 210 at the same time. However, when the volume of the reservoir chamber 212 decreases and the reservoir piston 210 moves from the normal position to the volume reducing position, the reservoir piston 210 moves the valve element 224 via the pin 230 in a direction away from the valve seat 222. ,
As a result, the valve element 224 is separated from the valve seat 222, and an inflow permitted state is allowed in which the brake fluid in the reservoir 14 is allowed to flow into the reservoir chamber 212.

FIG. 4 shows a specific structure of the brake device described above, and also shows a specific structure of the pump 150. As is clear from the figure, the pump 150
Has a housing 300 made of a material containing aluminum as a main component, and a cylinder bore 302 is formed in the housing 300. A piston 304 is slidably fitted in the cylinder bore 302, and the piston 30
An eccentric cam 306 is engaged with the rear end portion of No. 4.

The motor 152 is attached to the housing 300, and the axis of the rotating shaft of the motor 152 intersects the axis of the piston 304 at a right angle. The eccentric cam 306 is non-rotatably attached to the rotation shaft of such a motor 152.

The eccentric cam 306 is constructed by eccentrically mounting a disk bearing on the rotation axis of the motor 152. As is well known, the bearing has a structure in which an outer ring-shaped member is relatively rotatably fitted to an inner ring-shaped member via a plurality of rolling elements (balls, rollers, etc.). The bearing is non-rotatably mounted on the rotating shaft of the motor 152 on the inner ring-shaped member, while it contacts the rear end of the piston 304 on the outer ring-shaped member. The bearing is used as the disc in order to prevent the rotation of the motor 152 from being directly transmitted to the outer ring-shaped member that contacts the rear end portion of the piston 304, and to reduce the contact between the piston 304 and the outer ring-shaped member. is there.

The cylinder bore 302 has one end closed by a piston 304 and the other end closed by a plug 310, whereby a pump chamber 312 is formed. The volume of the pump chamber 312 is increased / decreased in accordance with the linear reciprocating motion of the piston 304 by the eccentric cam 306. In the volume increasing process, the suction valve 153a is opened and the brake fluid flows from the reservoir 144 into the pump chamber 312. On the other hand, in the volume reduction process, the discharge valve 153b
Is opened and the brake fluid in the pump chamber 312 is discharged to the high pressure side.

As shown in FIG. 1, the pump 150 is provided for each of the two brake systems, and two pumps are provided for the entire braking device. The two pumps 150 are driven by a common motor 152. That is, in the present embodiment, the two pistons 150 and the one motor 152 constitute an opposed piston pump. Then, in FIG. 5, only a portion of the brake device relating to the opposed piston pump is taken out and shown.

In this opposed type piston pump, the two pumps 150 share the one united piston 314. As shown in FIG. 6 which is a perspective view and FIG. 7 which is a side view, the united piston 314 has an axial shape that extends straight in a substantially circular cross section, and has brakes at both ends thereof. A portion (hereinafter, simply referred to as “piston 304”) that functions as each piston 304 that increases or decreases the volume of each pump chamber 312 belonging to the system is formed. That is, the combined piston 314 is a combination of a pair of pistons 304 corresponding to two brake systems. As shown in FIG. 5, the pair of cylinder bores 302 corresponding to the two brake systems are provided in the housing 30.
0 are formed so as to face each other with the eccentric cam 306 interposed therebetween and have the same diameter between the two brake systems, and one coalescing piston 314 is formed across the two cylinder bores 302. It is slidably fitted.

Therefore, in this embodiment, the distance between the support points of the housing 302 of the united piston 314 at the two ends is such that the plurality of points assumed on the circular periphery of the one end face of the united piston 314 and the circular periphery of the other end face. It is the distance between the two most distant points A and B of the combination with the above-mentioned plurality of points. Therefore, it is sufficient to determine the length of each piston 304 of the united pistons 314 in consideration of smoothing of the axial movement and retention of airtightness, and it is not essential to determine the length in consideration of the prevention of twisting. Disappeared
The length of the united piston 314 becomes shorter than in the case where the pair of pistons 304 are fitted into the housing 302 independently of each other as in the conventional case.

A concave portion 316 which is an engaging portion with the eccentric cam 306 is formed in an intermediate portion of the united piston 314 (see FIGS. 6 and 7). The recess 316 is formed by a bottom surface portion 318 extending parallel to the axis of the united piston 314, and a pair of side surface portions 320 extending from both edges of the bottom surface portion 318 in a direction perpendicular to the axis. The pair of side surface portions 320 are sized to sandwich the diameter portion of the eccentric cam 306 from both sides thereof with a slight gap left therebetween. That is, the pair of side surface portions 320 are provided on the eccentric cam 3
06 is sandwiched from both sides thereof and substantially contacts the cam surface thereof. As a result, the eccentric cam 306 rotates in one direction, and if the position of the eccentric cam 306 when viewed from directly above is reciprocated in the axial direction of the united piston 314, the united piston 314 is accompanied by it. Will be reciprocated. Due to the engagement of the eccentric cam 306 and the recess 316, the united piston 314 performs not only the forward movement in which each piston 304 reduces the volume of each pump chamber 312 but also the backward movement in which the volume of each pump chamber 312 is increased. Therefore, it is not essential to dispose a return spring in each pump chamber 312 in order to realize the backward movement of each piston 304 as in the conventional case.

That is, the eccentric cam 306 causes the pair of pistons 304 to reciprocate while keeping the distance therebetween constant to increase or decrease the volume of each pump chamber 312. At this time, the volume of each pump chamber 312 is increased or decreased. The directions of changes in the above are opposite to each other, and when one pump chamber 312 is in the volume increasing process, the other pump chamber 312 is in the volume decreasing process.

As is clear from the above description, in the present embodiment, it is not essential to secure a space for disposing the return spring in each pump chamber 312, and the above-mentioned pair of pistons 304 is provided. In cooperation with coalescence, the pair of pistons 304 of the housing 300
It is possible to obtain the effect that the dimension L (see FIG. 5) in the axial direction can be easily shortened.

By the way, when the united piston 314 is engaged with the eccentric cam 306 in its recess 316 and the united piston 314 is reciprocated by the eccentric cam 306, the united piston 314 is moved from the forward stroke to the backward stroke. A tapping sound is generated between the concave portion 316 and the eccentric cam 306 each time the backward movement stroke is changed to the forward movement stroke. Of the pair of side surface portions 320, the cam surface, which is the outer peripheral surface of the eccentric cam 306, alternately contacts with each other in the forward movement stroke and the backward movement stroke, and the eccentric cam 3 is changed during the change.
This is because 06 and the side surface portion 320 are in contact with each other. But,
The level of the hammering sound expected to be generated is jarring to the occupant even when the pump 150 is artificially operated in a situation where the engine sound of the vehicle and the running noise are relatively small, such as during the initial check of the brake device. It is estimated that it will not reach such a level. This is because the tapping sound is generated when the united piston 314 is near the stroke end and the moving speed thereof is near zero.

The united piston 314 is further provided with an annular groove 32 between the recess 316 and the piston 304.
2 are formed respectively. A seal member 324 is attached to each annular groove 322. In the present embodiment, the seal member 324 includes a D ring 326 and a backup ring 328 arranged behind the D ring 326 (as viewed from the pump chamber 312). As a result, each pump chamber 312 is kept airtight.

The master cylinder cut valve 100, the intermediate valve 140, the pressure reducing valve 146 and the motor 152 are connected to an electronic control unit (hereinafter simply referred to as "ECU", Electronic Control Unit) 400, as shown in FIG. . This ECU 400 has, on its input side,
Four wheel speed sensors 402 that detect the wheel speed that is the rotation speed of each wheel are connected. Further, a brake switch 404 for detecting depression of the brake pedal 12,
An accelerator switch 406 or the like, which detects depression of an accelerator pedal (not shown) as an acceleration operation member, is also connected.

The ECU 400 is mainly composed of a computer 410. The computer 410 is a CPU
It is configured to include 412, ROM 414 and RAM 416. Various programs for executing antilock control and traction control are stored in the ROM 414, and the CPU 412 executes various programs while using the RAM 416 to execute antilock control and traction control.

The antilock control operates the motor 152 and monitors the rotation speed of each wheel and the traveling speed of the vehicle body through each wheel speed sensor 402, and at least a plurality of pressure increasing modes and pressure reducing modes are included. By selectively executing the mode, it is possible to prevent each wheel from locking during vehicle braking.

In the pressure increasing mode, the front wheel independent pressure increasing mode in which only the front wheel brake cylinders 16 and 18 are increased in each brake system, and the front wheel brake cylinders 16 and 18 are used.
And the front and rear wheel simultaneous pressure increasing mode in which both the rear wheel brake cylinders 17 and 19 are simultaneously increased in pressure. The front wheel independent pressure increasing mode is realized by setting the master cylinder cut valve 100 to the excited state (closed state), the intermediate valve 140 to the excited state (closed state), and the pressure reducing valve 146 to the demagnetized state (closed state). On the other hand, in the front-rear wheel simultaneous pressure increasing mode, the master cylinder cut valve 100 is in the excited state (closed state), and the intermediate valve 140
Is demagnetized (open state), and the pressure reducing valve 146 is demagnetized (closed).

On the other hand, in the pressure reducing mode, there is a front / rear wheel simultaneous pressure reducing mode for simultaneously reducing the pressure of the front wheel brake cylinders 16 and 18 and the rear wheel brake cylinders 17 and 19 in each brake system. The front-rear wheel simultaneous depressurization mode is realized by setting the master cylinder cut valve 100 to the excited state (closed state), the intermediate valve 140 to the demagnetized state (open state), and the depressurization valve 146 to the excited state (open state).

When the motor 152 is operated during the antilock control, the eccentric cam 306 rotates in one direction, and the eccentric cam 306 causes the coalescing piston 314 to reciprocate so that the two pumps 150 are simultaneously operated. . As a result, the volume of each pump chamber 312 is increased or decreased, and the brake fluid is pumped up from each reservoir 144 and discharged to the high pressure side. Therefore, in the pressure boosting mode, only the front wheel brake cylinders 16 and 18 or the front wheel brake cylinders 16 and 18 and the rear wheel brake cylinder 1 are used.
High-pressure brake fluid is supplied to both of the brake cylinders 7 and 19, whereby the brake cylinders 16, 17, 18 and 19 are pressurized appropriately.

The brake fluid to be pumped by each pump 150 does not always exist in each reservoir 144. If it does not exist, a negative pressure tends to be generated in the reservoir chamber 212, but at a stage when the negative pressure becomes a little negative, the inflow control valve 172 is opened in the same manner as in the traction control described later, and the brake fluid is discharged from the reservoir 14. Each reservoir 1
It is replenished to 44. As a result, each pump chamber 31 has a structure in which not only the forward movement but also the backward movement of the united piston 314 is forcibly performed by the eccentric cam 306.
2 is prevented from becoming a large negative pressure.

On the other hand, the traction control is performed by the motor 152.
While monitoring the rotational speeds of the front left and right wheels, which are driving wheels, and the traveling speed of the vehicle body through the wheel speed sensors 402, at least a plurality of modes including a pressure increase mode and a pressure decrease mode are selectively selected. By executing the control, the left and right front wheels are prevented from idling when the vehicle is driven. The traction control ends when a predetermined condition such as the brake switch 404 detecting the driver's depression of the brake pedal 12 or the accelerator switch 406 detecting the driver's depression of the accelerator pedal 12 is satisfied. To do.

The pressure increasing mode means a mode in which only the front wheel brake cylinders 16 and 18 are increased in pressure in each brake system. The master cylinder cut valve 100 is in an excited state (closed state) and the intermediate valve 140 is in an excited state (closed state). ), And the pressure reducing valve 146 is demagnetized (closed).

The inflow control valve 172 is in the inflow blocking state immediately before the start of the traction control, but if the traction control is started and the pump 150 is operated, the pump 15
The brake fluid in the reservoir chamber 212 is pumped up by 0 and supplied to the front wheel brake cylinders 16 and 18. As a result, the pressures of the front wheel brake cylinders 16 and 18 are increased, the rotational speed of each front wheel is suppressed, and the idling of each front wheel is suppressed.

If the reservoir chamber 212 has a negative pressure because the brake fluid in the reservoir chamber 212 is pumped up by the pump 150, the reservoir piston 210 moves forward (moves upward in the figure) from the normal position shown in FIG. Pin 2
30 separates the valve element 224 from the valve seat 222. As a result, the inflow control valve 172 shifts to the inflow permitted state. Therefore, when the brake fluid in the reservoir chamber 212 is insufficient, the brake fluid from the reservoir 14 is replenished in the reservoir chamber 212.

Therefore, according to the present embodiment, the reservoir chamber 212 is prevented from becoming a large negative pressure, and the brake fluid is replenished from the reservoir 14 only when the brake fluid is insufficient in the reservoir 144. During the traction control, the brake fluid is excessive in the reservoir 144, and the reservoir piston 210 of the brake fluid is bottomed, so that the front wheel brake cylinders 16,
Since the brake fluid cannot be smoothly discharged from the front wheel brake cylinders 16 and 18 to the reservoir 144 when the pressure of the front wheel 18 is reduced, the front wheel brake cylinders 16 and 18 cannot be discharged.
It is possible to obtain a unique effect that it is possible to avoid the situation where the pressure is not quickly reduced.

On the other hand, the depressurization mode means a mode in which only the front wheel brake cylinders 16 and 18 in each brake system are depressurized, and the master cylinder cut valve 100 is used.
Is in an excited state (open state), the intermediate valve 140 is in a demagnetized state (open state), and the pressure reducing valve 146 is in a demagnetized state (closed state). When the depressurization mode is executed, the brake fluid in the front wheel brake cylinders 16 and 18 is the front wheel brake passage 22, the rear wheel brake passage 24, and the second check valve 16.
4, intermediate valve 140, return passage 154 and check valve 156
After that, the process returns to the master cylinder 10.

Another embodiment will be described.

In the above-described embodiment, as shown in FIG. 5, each pump chamber 312 is closed by each plug 310, and the two brake plugs 310 as a whole are provided.
Although one is used, the present invention can be implemented with one plug 310 being sufficient.

For example, as shown in FIG. 9, one of the two cylinder bores 302 is formed in the housing 300 in a bottomed state, while the other cylinder bore 302 is formed in a bottomless state as in the above embodiment. Then, after the coalescing piston 314 is inserted and fitted into the two cylinder bores 302, only the other cylinder bore 302 can be closed with the plug 310. By doing so, only one plug 310 is required for the entire braking device, the number of parts is reduced, and the assemblability of the pump is improved.

Another embodiment will be described.

In each of the two embodiments described above, the inflow control valve 172 is provided in the auxiliary passage 170 connecting the reservoir 144 and the reservoir 14, and the reservoir piston 210 of the reservoir 144 is the pilot piston of the inflow control valve 172. However, the present invention can also be implemented in the following modes, for example.

That is, as shown in FIG. 10, the use of the inflow control valve 172 in the auxiliary passage 170 is omitted, and the normal reservoir 430 is used instead of the reservoir 144.
Can also be implemented in the form used. The conventional reservoir 430 does not have a neutral position and the reservoir piston 432 is always in the illustrated advanced end position by the spring 434.

Further, in the present embodiment, the auxiliary passage 1
Restriction to a part of 70 that is common to two brake systems 4
40 are provided. Thereby, each pump 150 preferentially pumps the brake fluid from each reservoir 430, and the brake fluid from the reservoir 14 is mainly stored in each reservoir 4.
Pumps 15 when the brake fluid is insufficient at 30
It will be pumped up by 0.

Therefore, according to the present embodiment, the reservoir chamber of the reservoir 430 does not become a large negative pressure, and the brake fluid in the reservoir 14 for the master cylinder 10 is not used more than necessary. It is possible to easily reduce the number of parts and to simplify the structure of the brake device, which is a unique effect.

Although some embodiments of the present invention have been described in detail above with reference to the drawings, other than these, various modifications based on the knowledge of those skilled in the art without departing from the scope of the claims. It goes without saying that the present invention can be implemented in an improved form.

[Brief description of drawings]

FIG. 1 is a system diagram showing a diagonal two-system type anti-lock / traction type brake device including an opposed piston pump according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing one of two brake systems in the brake device of FIG.

3 is an enlarged front sectional view showing a reservoir and an inflow control valve in FIG.

FIG. 4 is a partial cross-sectional view showing a specific configuration of one of two brake systems in the brake device of FIG.

5 is a plan sectional view showing a relationship between two pumps and one motor in FIG. 1. FIG.

FIG. 6 is a perspective view showing a united piston in FIG.

FIG. 7 is a plan view and a side view of the united piston.

FIG. 8 is a block diagram showing an electrical configuration of the brake device.

FIG. 9 is a plan sectional view showing an opposed type piston pump according to another embodiment of the present invention.

FIG. 10 is a system diagram showing a diagonal two-system type antilock / traction type braking device including an opposed piston pump according to still another embodiment of the present invention.

FIG. 11 is a plan sectional view showing a conventional example of an opposed piston pump.

[Explanation of symbols]

 10 master cylinder 16,18 front wheel brake cylinder 17,19 rear wheel brake cylinder 100 master cylinder cut valve 140 intermediate valve 144 reservoir 146 pressure reducing valve 150 pump 152 motor 172 inflow control valve 300 housing 306 eccentric cam 312 pump chamber 314 merged piston 316 recess 318 Bottom part 320 Side part

Claims (2)

[Claims] 1. A housing, an eccentric rotation member that eccentrically rotates with respect to an axis in a space inside the housing, and a state where the eccentric rotation member is sandwiched from both sides of the eccentric rotation member on a straight line perpendicular to the axis. And a pair of pistons slidably fitted in the housing, and a pair of independent pump chambers formed between the pair of pistons and the housing. The piston is a coalesced piston in which the pair of pistons are immovably immovable in at least the direction of the straight line, and the coalesced piston is attached to the eccentric rotation member at an intermediate portion thereof by the eccentric rotation member. Of the forward movement, the portion of each of the pistons that functions as each piston reduces the volume of each pump chamber. The opposed piston pump is characterized in that it is engaged in a state in which the backward movement to increase its volume is also performed. 2. The opposed piston pump according to claim 1, wherein the eccentric rotation member is an eccentric cam that rotates a disc eccentric with respect to the axis, and a recess is formed in an intermediate portion of the united piston. And the concave portion is (a) a bottom surface portion that extends substantially parallel to the straight line, and (b) a pair of side surface portions that extend substantially perpendicularly to the straight line from both edge portions of the bottom surface portion, and the eccentricity It is formed by sandwiching the cam from both sides of the cam and making substantial contact with the cam surface of the eccentric cam. By inserting the eccentric cam into the recess, the eccentric cam reciprocates the united piston. Opposed piston pump characterized by being moved.