1. Field of the Invention
This invention relates to pressure regulators in general and more particularly to a pressure regulator wherein a lack of the fuel supply volume can be removed at a high temperature of the engine.
2. Description of the Prior Art
This kind of pressure regulator has been applied to, for example, a fuel supply system. In FIG. 2 illustrating schematically the system, the fuel stored in a fuel tank 1 is pressurized by a fuel pump 2, supplied to an injector 7 through a fuel damper 3 and a fuel filter 4, and injected to an intake manifold 8 from the injector 7. A fuel supply conduit 9 connected to the injector 7 is provided with a branch conduit 9a whose free end is connected with a fuel pressure chamber of a pressure regulator 5'. The pressure regulator is further provided with a vacuum chamber connected with the intake manifold 8 through a conduit 6.
In FIG. 3 showing the structure of a conventional pressure regulator, an interior of a casing member 14 is divided into two chambers by means of a diaphragm 12. One chamber means includes a vacuum chamber 14 a connected with the intake manifold 8 via conduit 10, and the other chamber means includes a fuel pressure chamber 14b connected with the fuel conduit 9.
Interposed within the vacuum chamber 14a is a spring 11' which has a predetermined spring coefficient and biases the diaphragm 12 toward the fuel pressure chamber 14b against the vacuum within the vacuum chamber l4a. The fuel pressure chamber 14b is further connected with a fuel return conduit 15 which returns surplus fuel to the fuel tank 1. The communication between the fuel pressure chamber 14b and the fuel return conduit 15 is controlled by a valve 13' disposed in the diaphragm 12.
Referring to FIG. 2 and FIG. 3, when there are no changes in the vacuum pressure within the intake manifold 8, the fuel pressure in the conduit 9 is maintained at a constant positive value. Under this condition, between the vacuum pressure in the vacuum chamber 14a and the biasing force of the spring 11' a balance is maintained with a constant differential pressure, and therefore the valve 13' is maintained in the closed position thereby preventing the fuel from flowing into the return conduit 15.
When the vacuum pressure of the intake manifold 8 increases and also the vacuum pressure of the pressure regulator 5' increases, the diaphragm 12 will be moved upwardly against the force of the spring 11', thereby opening the valve 13' so that the fuel may be returned from the fuel pressure chamber 14b to the fuel tank 1 through the return conduit 15.
From the above, therefore, it will be seen that the pressure regulator 5' regulates the fuel pressure in response to changes in the vacuum pressure of the intake manifold 8 so that the differential pressure between the vacuum chamber 14a and the fuel pressure chamber 14b may be kept at a constant value so as to stably maintain the fuel supply volume.
Since the fuel supply conduit 9 is inevitably positioned close to the engine, the supply conduit 9 is apt to be under the influence of the heat radiated from the engine and then to be overheated by the radiated heat, whereby a vapor lock is apt to be produced in the conduit 9. Therefore, a predetermined volume of the fuel cannot be supplied to the intake manifold 8, thereby stopping operation of the engine.
In order to avoid the above disadvantages, there is introduced means in which a branch conduit communicating with the atmosphere is newly established in the conduit 6 connecting the intake manifold 8 with the pressure regulator 5', and a thermal responsive valve is further installed in the branch conduit 9a. When an ambient temperature rises beyond a predetermined value, the pressure chamber 14a will be connected with atmosphere by the operation of the thermal responsive valve, whereby the vacuum chamber 14a will be under atmospheric pressure and the fuel pressure of the fuel pressure chamber 14a will increase. Thus, the fuel supply volume can be suitably maintained. If the above technical means is adopted, however, there will be drawbacks in that the construction of the system is complicated, and a fluid leak takes place in the valve of the thermal responsive valve, with the result that productivity will be deteriorated and the fuel supply cannot be controlled with accuracy.