1. A travel vibration suppressing device of a work vehicle, connected to a hydraulic cylinder for operating a work machine and adapted to suppress vibration during vehicle travel, the travel vibration suppressing device comprising:
an accumulator configured to be connected to the hydraulic cylinder;
a control valve configured to bring about communication or blocking between the hydraulic cylinder and the accumulator;
a vehicle speed detecting device configured to detect vehicle speed of the work vehicle;
a work machine state determination section configured to determine whether the state of the work machine is an excavating state in which excavation is expected to be performed using the work machine, or a normal state in which excavation by the work vehicle is not performed; and
a control unit configured to control the control valve according to the determination result of the work machine state determination section; wherein
the control unit is configured to
upon determining the state of the work machine to be the excavating state, switch from a state of communication between the hydraulic cylinder and the accumulator to a blocked state when the vehicle speed changes from a speed exceeding a first speed to a speed which is equal to or less than the first speed, and
upon determining the state of the work machine to be the normal state, switch from the state of communication between the hydraulic cylinder and the accumulator to the blocked state when the vehicle speed changes from a speed exceeding a second speed which is lower than the first speed to a speed which is equal to or less than the second speed.
2. The travel vibration suppressing device in a work vehicle according to claim 1, wherein
the control unit is configured to
in the excavating state, place the hydraulic cylinder and the accumulator in the state of communication therebetween when the vehicle speed is equal to or greater than a third speed which is higher than the first speed; and
in the normal state, place the hydraulic cylinder and the accumulator in the state of communication therebetween when the vehicle speed is equal to or greater than a fourth speed which is higher than the second speed.
3. The travel vibration suppressing device in a work vehicle according to claim 1, wherein the work machine has a boom lifted and lowered by the hydraulic cylinder, and a bucket rotatably mounted to the distal end of the boom via a hinge pin, and
the work machine state determination section is configured to determine the state of the work machine from the height of the bucket.
4. The travel vibration suppressing device in a work vehicle according to claim 3, wherein
the work machine state determination section is configured to
determine that the excavating state exists when the height of the bucket is equal to or less than a predetermined height, and
determine that the normal state exists when the height of the bucket exceeds the predetermined height.
5. The travel vibration suppressing device in a work vehicle according to claim 3, wherein
the work machine state determination section is configured to
determine that the excavating state exists when the height of the bucket is equal to or less than a first height, and
determine that the normal state exists when the height of the bucket is equal to or greater than a second height which is higher than the first height, and
the control unit is configured to
execute control such that the state of the work machine remains in the excavating state until the height of the bucket reaches the second height when transitioning from the excavating state to the normal state, and
execute control such that the state of the work machine remains in the normal state until the height of the bucket reaches the first height when transitioning from the normal state to the excavating state.
6. The travel vibration suppressing device in a work vehicle according to claim 3, wherein
the work machine state determination section is configured to designate the height of the hinge pin as the height of the bucket when determining the state of the work machine.
7. The travel vibration suppressing device in a work vehicle according to claim 3, wherein
the work machine state determination section is configured to
determine that the excavating state exists when the height of the bucket is equal to or less than a first height,
determine that the normal state exists when the height of the bucket is equal to or greater than a second height which is higher than the first height, and
determine that an intermediate state exists when the height of the bucket is lower than the second height which is higher than the first height, and
the control unit is configured to
upon determining the state of the work machine to be the intermediate state, place the hydraulic cylinder and the accumulator in the communicating state when the vehicle speed is equal to or greater than the third speed, and place the hydraulic cylinder and the accumulator in the blocked state when the vehicle speed is equal to or less than the second speed.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Apparatus for testing semiconductor integrated circuit devices in wafer form, the apparatus comprising:
a test head,
a wafer prober for presenting successive wafers to be tested to the test head from beneath the test head,
a probe card support mechanism attached to the wafer prober for supporting a probe card beneath the test head, and
a lifting mechanism attached to the wafer prober for lifting the test head above the wafer prober,
and wherein upon lifting the test head above the wafer prober, the probe card support mechanism can move horizontally relative to the test head between an inserted position in which the probe card support mechanism is positioned to enable the probe card to engage contact elements of the test head and an extended position in which the probe card can be removed from the probe card support mechanism.
2. Apparatus according to claim 1, further comprising a probe card changer body attached to the wafer prober and wherein the probe card support mechanism includes a probe card tray attached to the probe card changer body, the probe card tray being movable relative to the probe card changer body between a retracted position and a projecting position.
3. Apparatus according to claim 2, comprising attachment elements to which the probe card changer body is attached, the test head being releasably engageable to the attachment elements, and wherein the lifting mechanism is effective between the wafer prober and the attachment elements.
4. Apparatus according to claim 3, wherein the attachment elements are docking bars and the test head is releasably engageable to the docking bars by a cam mechanism.
5. Apparatus according to claim 2, wherein the probe card tray is moveable vertically relative to the probe card changer body when the test head is lifted above the wafer prober.
6. Apparatus according to claim 1, wherein the test head includes a pogo tower.
7. Apparatus according to claim 1, wherein the probe card support mechanism is attached to the lifting mechanism and the lifting mechanism is releasably attached to the test head.
8. A method of modifying an apparatus for testing semiconductor integrated circuit devices in wafer form, the apparatus comprising a test head and a wafer prober for presenting successive wafers to be tested to the test head from beneath the test head, said method comprising:
disengaging the test head from the wafer prober,
attaching a lifting mechanism to the wafer prober,
attaching a probe card support mechanism to the wafer prober for supporting a probe card, and
engaging the test head with the lifting mechanism,
whereby the lifting mechanism can be employed to lift the test head above the wafer prober and upon lifting the test head above the wafer prober, the probe card support mechanism can move horizontally relative to the test head between an inserted position in which the probe card support mechanism is positioned to enable the probe card to engage contact elements of the test head and an extended position in which the probe card can be removed from the probe card support mechanism.
9. A method according to claim 8, wherein the apparatus includes attachment elements and the method comprises attaching the lifting mechanism to the attachment elements whereby the attachment elements may be elevated relative to the wafer prober.
10. A method according to claim 9, wherein the step of engaging the test head with the lifting mechanism comprises docking the test head to the attachment elements.
11. A method according to claim 8, wherein the apparatus includes docking bars and the method comprises attaching the lifting mechanism to the docking bars whereby the docking bars may be elevated relative to the wafer prober.
12. A method according to claim 8, comprising attaching the probe card support mechanism to the lifting mechanism and releasably attaching the lifting mechanism to the test head.
13. A method according to claim 8, wherein the method further comprises:
moving the card support mechanism to the extended position,
placing a probe card into the probe card support mechanism, and
moving the probe card support mechanism to the inserted position.