Governor device for controlling a compressor

Abstract

Disclosed is a governor device for controlling a compressor in a pressurized air system. The governor device includes a supply port, a control port, an exhaust opening, an inlet valve between the supply port and the control port, and an outlet valve between the control port and the exhaust opening. The governor device also includes a displaceable piston and is switchable between a basic position with an open outlet valve and closed inlet valve and an actuated position with a closed outlet valve and open inlet valve. A valve arrangement is included at the piston, the valve arrangement comprising a fixed means fixed to the piston and a valve plate displaceable with respect to the fixed means.

Claims

1. A governor device for controlling a compressor in a pressurized air system, said governor device comprising: a supply port for receiving a supply pressure, a control port for delivering a control pressure to said compressor, an exhaust opening for exhausting air, an inlet valve provided between said supply port and said control port, and an outlet valve provided between said control port and said exhaust opening, a displaceable piston, an active bottom face of said piston being chargeable with the supply pressure to exert a pressure force, a spring means for biasing said piston with a bias force against said pressure force of the supply pressure, wherein said governor device is switchable between a basic position with an open outlet valve and a closed inlet valve and an actuated position with a closed outlet valve and an open inlet valve, wherein a valve arrangement is provided at said piston, said valve arrangement comprising a fixed means fixed to said piston and a valve plate displaceable with respect to said fixed means, wherein said fixed means comprises an exhaust passage to be sealed by a lip seal of said valve plate in said actuated position thereby realizing said outlet valve, wherein said inlet valve and said outlet valve are realized by said valve arrangement; wherein said lip seal is provided on a central hole of said valve plate, said central hole surrounding said fixed means for realizing said outlet valve, and wherein said valve plate is moveable in an axial direction with respect to said fixed means, for closing and opening a drilling passage in dependence of the piston position.

2. The governor device according to claim 1, wherein in said basic position the supply pressure does not exceed the bias force, and in said actuated position the supply pressure exceeds the bias force.

3. The governor device according to claim 1, further comprising a dome to be fixed in an external part, and an insert screwed into said dome, wherein said piston is slidably provided inside said insert.

4. The governor device according to claim 1, wherein said fixed means is screwed into said piston and defines a hole, and wherein said exhaust passage is realized by said hole extending in the axial direction and a drilling passage extending perpendicular to the axial direction.

5. The governor device according to claim 1, wherein said spring means is adjustable to adjust the bias force and defines a cut-out pressure, which exceeds the bias force.

6. A governor device for controlling a compressor in a pressurized air system, said governor device comprising: a supply port for receiving a supply pressure, a control port for delivering a control pressure to said compressor, an exhaust opening for exhausting air, an inlet valve provided between said supply port and said control port, and an outlet valve provided between said control port and said exhaust opening, a displaceable piston, an active bottom face of said piston being chargeable with the supply pressure to exert a pressure force, a spring means for biasing said piston with a bias force against said pressure force of the supply pressure, wherein said governor device is switchable between a basic position with an open outlet valve and a closed inlet valve and an actuated position with a closed outlet valve and an open inlet valve, wherein a valve arrangement is provided at said piston, said valve arrangement comprising a fixed means fixed to said piston and a valve plate displaceable with respect to said fixed means, wherein said inlet valve and said outlet valve are realized by said valve arrangement, wherein said inlet valve is realized by a sealing interface of said valve plate and a casing sealing surface, wherein a valve spring biases said valve plate with respect to said piston, and wherein in an idle position of said piston said valve spring presses a sealing surface of said valve plate against said casing sealing surface thereby closing said inlet valve.

7. The governor device according to claim 6, wherein in said idle position a distance between said piston and said casing sealing surface is smaller than in said actuated position.

8. The governor device according to claim 6, wherein the valve spring is provided between said bottom face of said piston to be charged by the supply pressure and said valve plate.

9. A pressurized air system, comprising the governor device according to claim 6, and a casing receiving and housing said governor device, wherein said casing sealing surface is provided at said casing, and wherein a control channel is formed in said casing extending to said control port.

10. The pressurized air system according to claim 9, wherein said casing is an air dryer casing of an air dryer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail below by means of exemplary embodiments shown in the drawings, wherein

(2) FIG. 1 is a sectional perspective view of a governor according to one embodiment of the invention;

(3) FIG. 2 is a sectional perspective view of the valve plate;

(4) FIG. 3 is a sectional view of the valve arrangement;

(5) FIG. 4 is a sectional view of the governor in its basic state (consumption, cut-in);

(6) FIG. 5 the valve arrangement of FIG. 3 in its actuated state (cut-out, off load phase);

(7) FIG. 6 depicts a pneumatic symbolic scheme representing the governor; and

(8) FIG. 7 is a diagram of the pressure as a function of time during subsequent phases.

DETAILED DESCRIPTION

(9) A governor 1 is provided in a pressurised air system of a vehicle in order to switch a compressor on and off in dependence of a supply pressure p21 provided in a supply tank 22. Thus the governor 1 detects a system pressure p21 of the supply tank 22 and outputs a control pressure p1 as a pressure signal to the control input of the compressor 24; this control input can be realised for example as part of an unloader valve of the compressor 24.

(10) The governor 1 comprises a dome 2 serving as a cover and being fixed, in particular screwed with its outer thread 2a into a casing 30, further an insert 3 screwed into the dome 1, a piston 4 slidably provided inside the insert 3, a spring 5 and a spring cap 6, wherein the spring 5 is provided between the spring cap 6 and the piston 4 and acts upon the top surface 4b of the piston 4.

(11) Thus main parts of the governor 1 are realised in the insert 3, which is fixed in the dome by an insert thread connection 13. Pre-assembling is therefore ease to handle, since most parts can be adjusted and pre-assembled in the insert 3.

(12) Further the governor 1 comprises a regulation screw 7 for adjusting a bias force of the spring 5 by pushing the spring cap 6. The piston 4 is sealed inside the insert 3 by a dynamic O-ring 8; further a static O-ring 9 and a protection cover 10 are provided; the regulation screw 7 is screwed into a screw thread part 11 fixed to the protection cover 10.

(13) A valve arrangement 12 is provided inside the piston 4 and extends under the piston 4; said valve arrangement 12 is explained more in detail with respect to FIGS. 2 to 5. The valve arrangement 12 comprises a stem 14 provided in the piston 4, for example by a thread (or interference fitting), further a valve plate 15 (valve disc) and a valve spring 16 provided between the piston 4 and the valve plate 15.

(14) The valve plate 15 surrounds a smaller top part 14a of the stem 14 and is biased by the valve spring 16. The stem 14 comprises a blind hole 14c starting from the top face 14e, extending through the smaller top part 14a and ending in the thicker bottom part 14b. A drilling 14d extends vertically to the axis A from the outside through the wall of the smaller top part 14a to the blind hole 14c.

(15) The valve plate 15 comprises a central hole 15a surrounding the smaller top part 14a of the stem; thus the valve plate 15 is displaceable (shiftable) in the top part 14a of the stem 14 along the axis A. The valve plate 15 further comprises at its bottom face a ring-shaped sealing surface 15b surrounding the central hole 15a. Furthermore the valve plate 15 comprises a lip seal 15c at the top of the central hole 15a.

(16) These features enable the valve arrangement 12 to realize the following valve functions:

(17) a) Inlet Valve Between Control Port 20 and Supply Port 21

(18) The sealing surface 15b of the valve plate 15 and a casing sealing surface 25 of the casing 30 serving as an inlet valve (The casing 30 is e.g. part of an air dryer body):

(19) Closed Inlet Valve, FIG. 4:

(20) is in the basic position of FIG. 4 the piston 4 is in its lowest position. Thus the valve plate 15 is pressed with its sealing surface 15b against the casing sealing surface 25 thereby closing a passage between a supply port 21, which is connected to the supply tank 22, and a control port 20 to be connected to the control input of the compressor. Therefore the inlet valve is closed.
Open Inlet Valve, FIG. 5:
The control port 20 is provided in the casing 30 under the bottom part 14b of the stem 14; air can pass the bottom part 14b in axial direction along passages surrounding the bottom part 14b. Thus if the valve plate 15 detaches according to the actuated position of FIG. 5 and gets out of contact with the casing sealing surface 25, air from the supply port 21 can enter the control port 20; therefore the inlet valve is open. The control port 20 is therefore pneumatically connected to a control channel 23 provided in the casing 30.
b) Outlet Valve Between Control Port 20 and Exhaust Chamber 17

(21) The second valve function realises an outlet valve between the control port 20 and the exhaust chamber 17 provided above the piston 4: the control port 20 is connected to the passages surrounding the bottom part 14b of the stem 14; these passages extend to the drilling 14d of the stem 14.

(22) Closed Outlet Valve, FIG. 5:

(23) If the drilling 14d is closed by the lip seal 15c and the sealing surface 15b of the valve plate 15 is pressed to the sealing seat 14f of the stem 14, then the control port 20 is disconnected from the exhaust chamber 17; the outlet valve is closed.

(24) Open Outlet Valve, FIG. 4:

(25) If the drilling 14d is not sealed, the control port 20 can exhaust through the passages around the bottom part 14b, the drilling 14d and the blind hole 14c of the stem 14, upward to the exhaust chamber 17, which is connected to the outer space via exhaust holes 17a. Thus the drilling 14d and the blind hole 14c realize an exhaust passage formed in the stem 14.

(26) FIG. 4 depicts the idle condition or basic position of the valve arrangement 12: the pressure p21 of the supply chamber 22, acting through the supply port 21 onto the bottom face 4a of the piston 4 is not high enough to overcome the bias spring force of the spring 5. Thus the inlet valve consisting of the sealing surface 15b and the casing sealing surface 25 is closed, since the piston 4 is pressed into its lowest position, in which the valve plate 15 is pressed onto the casing sealing surface 25. The spring force of the valve spring 16 is considerably lower than the bias spring force of the spring 5 and therefore not relevant in this content.

(27) In this idle condition or basic position the control port 20 is connected via the passages surrounding the bottom part 14b of the stem 14 to the area surrounding the smaller top part 14a of the stem 14 and via the drilling 14d to the blind hole 14c and to the exhaust chamber 17. Therefore the control port 20 is exhausted, and the compressor receives the pressure signal p1=0 (1 bar) for continuing pressurising air.

(28) If the supply pressure p21 in the supply port 21 rises, see the diagram of FIG. 7, and reaches a cut-out level, then the force exerted by the pressure onto the bottom face 4a of the piston 4 is higher than the bias spring force of the spring 5 Therefore the piston 4 is moved upward, thereby disengaging the sealing surface 15b of the valve plate 15 from casing sealing surface 25 and thereby opening the inlet valve. Further the outlet valve realized by the lip seal 15c, the drilling 14d, sealing surface 15b and sealing seat 14f of stem is closed by the relative axial movement of the valve plate 15 with respect to the stem 14; this movement is enabled by the valve spring 16, which presses the valve plate 15 downward.

(29) Thus the two valve functions are realized by the relative position of the valve plate 15, with respect to the fixed insert 3 (insert valve), and the relative position of the valve plate 15 with respect to the stem 14, which is fixed to the piston 4.

(30) FIG. 7 displays a pressure-time-diagram of the supply pressure p21. Starting at time t0, the compressor starts to compress; at time t1 the pressure p1 starts to rise until time t2, in which the cut-out pressure P_cut_out is reached, thereby opening the inlet valve and closing the outlet valve, as described above. At t3 the pressure p21 levels out to a maximum plateau, and then at t4 starts to fall due to consumption by the connected air circuits, for example air brake circuits. At t5 the pressure p21 reaches the cut-in pressure P_cut_in, thereby closing the inlet valve and opening the outlet valve, as already described above.

LIST OF REFERENCE NUMERALS (PART OF THE DESCRIPTION)

(31) 1 governor 2 dome 2a outer thread of the dome 2 3 insert 4 piston 4a bottom face of the piston 4 4b top surface of the piston 4 5 spring 6 spring cap 7 regulation screw 8 dynamic o-ring 9 static o-ring 10 protection cover 11 screw thread part fixed to protection cover 10 12 valve arrangement 13 insert thread connection between dome 2 and insert 3 14 stem 14a smaller top part 14b thicker bottom part 14c blind hole 14d drilling vertical to the blind hole and the axis A 14e top face of the stem 14f sealing seat of the stem 15 valve plate, valve disc 15a central hole 15b sealing surface 15c lip seal 16 valve spring for biasing said valve plate 15 17 exhaust chamber 17a exhaust hole 20 control port 21 supply port, supply port to the supply chamber 22 supply tank 23 control channel in the casing 30 24 compressor 25 casing sealing surface 30 casing 30 A axis p21 supply pressure p1 control pressure P_cut_in cut-in pressure P_cut_out cut-out pressure